RU2835576C1 - Method and apparatus for implementing user equipment-initiated communication channel occupancy time interval for equipment based on use of frames - Google Patents

Abstract

FIELD: wireless communication.

SUBSTANCE: method comprises: determining, by user equipment, UE, in FBE mode, that a communication channel in an unlicensed spectrum region is available for use; and the transmission, by said UE, of a first transmission to a gNB node in a fixed frame period, FFP, associated with said UE, to initiate a first communication channel occupancy time interval, COT, within this FFP period by said UE, a first transmission starts at the beginning of the FFP period and ends before the onset of a free period within this FFP period; and receiving, by the UE, information on a time interval during which the UE is allowed to initiate periodic COT intervals, said time interval comprising an FFP period.

EFFECT: reduced delays in equipment mode based on use of frames, FBE.

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Description

Field of technology to which the invention relates

The present invention relates generally to the field of radio communications and, in particular embodiments, to methods and mechanisms for implementing a user equipment (UE) initiated channel occupancy time (COT) interval for frame based equipment (FBE).

State of the art

Recently, the license-free spectrum, also referred to as unlicensed spectrum or shared spectrum, has attracted considerable interest from cellular operators. 3GPP LTE Releases (Rel) 13 and 14 specified the Long Term Evolution licensed assisted access (LTE-LAA) system. More recently, in the New Radio Unlicensed (NR-U) system, operation in the unlicensed spectrum (or shared spectrum) was specified in Release 16 (3GPP TS 38.213, which is hereby incorporated by reference in its entirety) for the 3GPP New Radio (NR) system.

3GPP and IEEE technologies operating in unlicensed spectrum use the listen before talk (LBT) channel access principle. In some regions, such as the European Union (EU) and Japan, the LBT rule is usually dictated by the spectrum regulators to reduce the risk of interference and to provide a fairer coexistence mechanism. The LBT mechanism requires the transmitter to check whether there are other stations occupying the communication channel in question before starting a transmission and to postpone the transmission if the channel is occupied.

In particular, the LBT rule in the EU, specified in the European Standard (EN) 301 893 for the 5 GHz frequency range developed by the European Telecommunications Standards Institute (ETSI), uses a clear channel assessment (CCA) to determine whether a communication channel is available for transmission. The CCA assessment checks whether the energy received in the communication channel in question exceeds the CCA assessment threshold. If the received energy exceeds the CCA assessment threshold, the communication channel is considered to be in use (occupied), otherwise the communication channel is considered to be free. If the communication channel is free, the transmitter may transmit for a certain channel occupied time (COT) interval in a frequency band that is at least a part, for example 80%, of the total channel bandwidth. The maximum COT duration for a transmission burst is also specified in ETSI EN 301 893 V2.1.1 (2017-05), which is hereby incorporated by reference in its entirety. The maximum COT duration (MCOT), adopted in 3GPP NR-U Rel 16 (TS 37.213, which is hereby incorporated by reference in its entirety), is a function of the channel access priority class (CAPC). As specified in TS 37.213, to determine the COT duration, if the transmission gap (the interval between consecutive transmissions) is not greater than 25 μs (microseconds), this transmission gap is taken into account in the COT duration. A transmission packet is defined as a sequence of transmissions with pauses (i.e. transmission pauses) between them of no more than 16 µs, and if these pauses exceed 16 µs, such a sequence of transmissions is considered as separate transmissions.

3GPP Rel 16 (TS 37.213) defines several types of channel access in unlicensed spectrum, for downlink (DL) and uplink (UL).

During Type 1 access to the downlink (DL) channel, the gNB may transmit after first determining that the channel is idle, during the slot duration determination for the delay time T _d , and after the number in the randomly triggered countdown counter N, which is decremented at each determination that the slot is idle, becomes zero. The slot evaluation duration is 9 μs. Type 1 access to the DL channel is used before the start of a new COT interval, where the COT interval duration can be up to 10 ms depending on the traffic priority.

The Type 2 downlink (DL) channel access mode (Type 2 DL) uses a deterministic channel evaluation duration during which the channel is determined to be free. This Type 2 DL channel access mode includes the Type 2A, Type 2B, and Type 2C channel access modes.

Access mode Type 2A to the communication channel allows transmissions to be made if it is determined that the communication channel has remained idle for at least a 25 µs control interval before the start of the transmission.

Access mode Type 2B to the communication channel allows transmissions to be made if it is determined that the communication channel has remained free for at least a 16 µs control interval before the start of the transmission.

The Type 2C access mode to the communication channel allows transmission for no more than 584 µs without determining the channel state before starting the transmission.

The DL access mode Type 2A procedures are applicable to the link in the shared COT after a user equipment (UE) transmission and for transmissions containing a discovery burst with a duration of at most 1 ms and a duty cycle of at most 1/20.

The Type 2B or Type 2C DL access mode procedures to the communication channel are applicable to the next transmission(s) of the UE after a pause of 16 µs or before 16 µs, respectively, when the shared channel is busy.

Similar to the downlink (DL) channel access types, TS 37.213 defines uplink (UL) channel access procedures, where UL access mode Type 1 is based on the detection of the channel being idle for a fixed duration of the delay time (Td) and thereafter until a countdown counter, which is initialized by a random value N and decremented each time a slot is detected to be idle, reaches zero, as in DL channel access mode Type 1. UL channel access mode Type 2 requires the channel to be detected to be idle for a fixed (deterministic) duration before transmissions can be started, where UL channel access mode Type 2A requires the channel to be idle for at least 25 µs before transmissions can be started, and UL channel access mode Type 2B requires the channel to be idle for at least 16 µs before transmissions can be started. The Type 2C access mode to the communication channel allows transmission for no more than 584 µs without determining the channel state before starting the transmission.

The essence of the invention

Technical advantages are generally realized by embodiments of the present invention that describe a method and apparatus for transmissions using a receiver in a shared spectrum region.

According to one aspect of the present invention, a method is provided, comprising: determining, by a user equipment (UE) in a frame-based equipment (FBE) mode, that a communication channel in an unlicensed spectrum region is available for use; and transmitting, by the UE on this communication channel, a first transmission to a gNB within a fixed frame period (FFP) associated with the UE, for the purpose of initiating a first channel busy time (COT) interval by the UE within the FFP period, where the first transmission starts at the beginning of the FFP period and ends before the onset of a free period within the FFP period.

Optionally, in any of the preceding aspects, the procedure for determining that a communication channel is available comprises: performing, by the UE, a channel clearing assessment (CCA).

Optionally, in any of the preceding aspects, the procedure for determining that a communication channel is available comprises: starting, by the UE equipment, a countdown counter after receiving a successful CCA assessment; and determining, by the UE equipment, that the communication channel is available when a number in the countdown counter decreases to zero (0).

Optionally, in any of the preceding aspects, the first transmission comprises a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), channel state information (CSI), a scheduling request (SR), a random access preamble, or a sounding reference signal (SRS).

Optionally, in any of the preceding aspects, the first transmission occupies all or part of the bandwidth of the communication channel.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the UE, information about a time interval (T_UE_COT) during which the UE is allowed to initiate periodic COT time intervals, this T_UE_COT time interval comprising an FFP period.

Optionally, in any of the preceding aspects, the first COT interval is a periodic COT interval initiated by the UE.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the UE equipment, a configuration for configuring the UE equipment to initiate a semi-static COT interval on the communication channel.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the UE, configuration information regarding the first COT interval, the configuration information regarding the first COT interval comprising one or more of the following parameters: a COT interval index for the first COT interval; a periodicity for the FFP period; a maximum allowed duration of a COT interval within an FFP period (MCOT); a time offset within the FFP period; a minimum duration of a free period within the FFP period; a maximum duration of a free period within the FFP period; an offset of the FFP period; or frequency resources for uplink transmissions during the first COT interval.

Optionally, in any of the preceding aspects, the FFP period offset or the FFP period start position is determined relative to the boundary of a radio frame with an even sequence number.

Optionally, in any of the preceding aspects, the periodicity for the FFP period has a value in milliseconds (ms) from the set {1, 2, 2.5, 4, 5, 10}.

Optionally, in any of the preceding aspects, the periodicity for the FFP period has any one value in milliseconds (ms) from the set {1, 2, 2.5, 4, 5, 10} or a subset of the values {1, 2, 2.5, 4, 5, 10}, in accordance with the capability of the UE to initiate COT intervals.

Optionally, in any of the preceding aspects, the periodicity is in the range from 1 ms to 10 ms.

As an option, in any of the preceding aspects, the configuration information is received via dedicated RRC control signaling.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the UE, listen before talk (LBT) information for estimating a communication channel.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the UE equipment, from the gNB node, in response to sending the first transmission, an indicator indicating whether the initiation of the first COT interval by the UE equipment was acknowledged or rejected.

As an option, in any of the preceding aspects, the method further comprises: determining, by the UE, that the initiation of the first COT interval by the UE is confirmed after receiving a transmission from the gNB within a certain period of time after sending the first transmission, or that the initiation of the first COT interval is rejected if no transmissions have been received from the gNB within the time period.

As an option, in any of the preceding aspects, the method further comprises: performing, by the UE, uplink transmissions within the first COT interval when the initiation of this first COT interval by the UE is confirmed.

As an option, in any of the preceding aspects, the method further comprises: performing, by the UE, uplink transmissions within a second COT interval initiated by the gNB node when the initiation of the first COT interval by the UE equipment is rejected.

As an option, in any of the preceding aspects, the method further comprises: transmitting, by the UE equipment, to the gNB, a request to provide a new COT interval for use by the UE equipment, the requested new COT interval being a COT interval initiated by the UE equipment.

Optionally, in any of the preceding aspects, the method further comprises: starting a timer by the UE equipment after transmitting said request; and receiving, by the UE equipment, from the gNB node before the timer expires, an indication indicating that the request has been accepted, and making, by this UE equipment, transmissions in a new COT interval; and transmitting, by the UE equipment to the gNB node, another request for granting a new COT interval if the first request has not been accepted by the gNB node before the timer expires.

Optionally, in any of the preceding aspects, said request is transmitted within the third COT interval, initiated by the gNB node or initiated by the UE equipment.

Optionally, in any of the preceding aspects, the specified request contains the parameters of the new COT interval.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the UE equipment during the first COT interval, a signaling instructing the UE equipment to switch from transmission in accordance with the first COT interval to transmission in accordance with a fourth COT interval.

Optionally, in any of the preceding aspects, said signaling comprises information about the remaining duration of the fourth COT interval.

As an option, in any of the preceding aspects, the method further comprises: starting, by the UE equipment, a transition timer upon receiving said signaling.

As an option, in any of the preceding aspects, the method further comprises: continuing, by the UE, to transmit during the first COT interval in response to the completion of the fourth COT interval before the expiration of the transition timer.

As an option, in any of the preceding aspects, the method further comprises: switching, the UE equipment, to use the fourth COT interval for transmissions after the transition timer expires.

Optionally, in any of the preceding aspects, the fourth COT interval is a COT interval initiated by the UE, and the method further comprises: initiating, by the UE, the fourth COT interval within the next FFP period.

Optionally, in any of the preceding aspects, the fourth COT interval is a COT interval initiated by the gNB node, and the method further comprises: monitoring and sharing, by the UE, the fourth COT interval within the next FFP period.

As an option, in any of the preceding aspects, the method further comprises: transmitting, by the UE, capability information indicating the capability of the UE to initiate COT intervals.

According to another aspect of the present invention, a method is provided, comprising receiving, by a gNB node, from a user equipment (UE) over a communication channel in an unlicensed spectrum region, a first transmission within a fixed frame period (FFP), where the UE equipment is in a frame-based equipment (FBE) mode; and determining, by the gNB node, based on said first transmission, that the UE equipment initiates a first channel busy time (COT) interval within this FFP period in response to the fact that this first transmission has been started at the beginning of the FFP period and has been completed before the onset of a free period in this FFP period.

Optionally, in any of the preceding aspects, the first transmission comprises a PUCCH channel, a PUSCH channel based on a configured grant, channel state information (CSI), a scheduling request (SR), a random access preamble, or a sounding reference signal (SRS).

Optionally, in any of the preceding aspects, said first transmission occupies all or part of the bandwidth of the communication channel.

As an option, in any of the preceding aspects, the method further comprises: transmitting, by the gNB node to the UE, information about a time interval (T_UE_COT) during which the UE is allowed to initiate periodic COT intervals, this T_UE_COT time interval comprising an FFP period.

As an option, in any of the preceding aspects, the method further comprises: transmitting, by the gNB node to the UE, a configuration for configuring the UE to initiate a semi-static COT interval on the communication channel.

As an option, in any of the preceding aspects, the method further comprises: transmitting, by the UE, configuration information regarding the first COT interval, the configuration information regarding the first COT interval comprising one or more of the following parameters: a COT interval index for the first COT interval; a periodicity for the FFP period; a maximum allowed duration of a COT interval within this FFP period (MCOT); a time offset of the FFP period; a minimum duration of a free period within the FFP period; a maximum duration of a free period within the FFP period; an offset of the FFP period; or frequency resources for uplink transmissions during the first COT interval.

Optionally, in any of the preceding aspects, the FFP period offset or the FFP period start position is determined relative to the boundary of a radio frame with an even sequence number.

As an option, in any of the preceding aspects, the method further comprises: transmitting, by the gNB node to the UE equipment, in response to receiving the first transmission, an indication indicating whether the initiation of the first COT interval by the UE equipment was confirmed (acknowledged) or rejected.

Optionally, in any of the preceding aspects, this indication is transmitted on the PDCCH, in the DCI information, or as a HARQ_ACK acknowledgement parameter.

Optionally, in any of the preceding aspects, the method further comprises: sending, by the gNB, in response to receiving the first transmission, to the UE a transmission within a certain period of time in order to confirm the initiation of the first COT interval; or not making, by the gNB, any downlink transmissions to the UE within the specified period of time in order to indicate that the initiation of the first COT interval is rejected.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the gNB node from the UE, a request to use a new COT interval for the UE, the requested new COT interval being a COT interval initiated by the UE.

As an option, in any of the preceding aspects, the method further comprises: indicating, by the gNB node to the UE equipment, whether the said request has been received.

Optionally, in any of the preceding aspects, this request is received within the third COT interval, initiated by the gNB node or initiated by the UE equipment.

Optionally, in any of the preceding aspects, the specified request contains the parameters of the new COT interval.

As an option, in any of the preceding aspects, the method further comprises: transmitting, by the gNB node to the UE equipment during the first COT interval, a signaling instructing the UE equipment to switch from transmission in accordance with the first COT interval to transmission in accordance with a fourth COT interval.

Optionally, in any of the preceding aspects, said signaling comprises information about the remaining duration of the fourth COT interval.

Optionally, in any of the preceding aspects, the fourth COT interval is a gNB-initiated COT interval or a UE-initiated COT interval.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the gNB node from the UE, capability information indicating the capability of the UE to initiate COT intervals.

As an option, in any of the preceding aspects, the method further comprises: receiving, by the gNB, from the plurality of UEs over the communication channel, a plurality of transmissions made by the respective UEs within the FFP period, each transmission of the plurality of transmissions starting at the beginning of the FFP period under consideration and ending before the onset of a free period within the FFP period under consideration; determining, by the gNB, that each of the plurality of UEs initiates a first COT interval within the FFP period; acknowledging, by the gNB, the first COT interval initiated by the UE under consideration; and rejecting, by the gNB, the first COT interval initiated by other UEs of the plurality of UEs.

As an option, in any of the preceding aspects, the method further comprises: canceling, by the gNB, the first COT interval initiated by the UE within the FFP period.

According to another embodiment of the present invention, a system is proposed, which comprises: a user equipment (UE), which is in a frame-based equipment (FBE) mode; and a gNB, which communicates with the UE. The UE is configured to: determine that a communication channel in an unlicensed spectrum is available for use; and transmit, on this communication channel, a first transmission to the gNB within a fixed frame period (FFP) associated with the UE, in order to initiate a first channel busy time (COT) interval by the UE within the considered FFP period, this first transmission starting at the start of the FFP period and ending before the onset of a free period within this FFP period. The gNB is configured to: receive, from the UE on the said communication channel in the unlicensed spectrum, the first transmission within the considered FFP period; and determining, based on this first transmission, that the UE initiates a first COT interval within this FFP period, in response to a first transmission that started at the beginning of the FFP period and ended before the onset of a free period within the FFP period in question.

According to another embodiment of the present invention, a device is proposed that has a non-volatile memory device containing instructions; and one or more processors communicating with this memory device, where, when the instructions are executed by one or more processors, a method is implemented according to any of the previous aspects.

According to another embodiment of the present invention, non-volatile computer-readable storage media are provided that store instructions, upon execution of which by one or more processors of the apparatus, the proposed apparatus implements the method according to any of the preceding aspects.

The above aspects of the present invention facilitate the implementation of communications by UE equipment in FBE mode in an unlicensed spectrum region, with reduced transmission delays, lower costs and lower battery consumption.

Brief description of the drawings

For a more complete understanding of the present invention and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a diagram of one of the variants of a radio communication network;

Fig. 2 represents one of the variants of the communication system and mathematical expressions for the signals transmitted in this communication system;

Fig. 3A and 3B are schematic diagrams of conventional systems for analog beam position control and digital beamforming;

Fig. 4 shows an example of a typical transmission synchronization timing diagram for frame-based equipment (FBE) operations;

Fig. 5 is a diagram of a conventional method of carrier monitoring;

Fig. 6 is a diagram of the usual "listen before you speak" method;

Fig. 7 shows an example of a typical procedure for accessing a Wi-Fi channel;

Fig. 8A is an illustration of an example of a wide beam pattern;

Fig. 8B is an illustration of an example of a narrow beam pattern;

Fig. 9 is a timing diagram of an example of synchronization of operations in the load based equipment (LBE) mode;

Fig. 10 is a timing diagram of an example of synchronization of operations in the FBE mode;

Fig. 11 is a timing diagram of one embodiment of synchronization of UE equipment operations, highlighting the CCA evaluation procedure after the countdown;

Fig. 12 shows a timing diagram of one embodiment of synchronization of UE equipment operations, highlighting a T_UE_COT time interval assigned to a group of UE equipment units and confirmation of COT intervals initiated by the UE equipment;

Fig. 13 is a timing diagram of one of the options for synchronizing the operations of the UE equipment, highlighting the periodic COT intervals assigned by the gNB node;

Fig. 14 is a timing diagram of one embodiment of synchronization of operations of the gNB node and the UE equipment, highlighting the initiation of COT intervals by both the gNB node and the UE equipment;

Fig. 15 is a logical diagram of one embodiment of the UE equipment operations for requesting a new COT interval for the UE equipment;

Fig. 16 represents one embodiment of an information element (IE) of configuration information for semi-static access to a communication channel;

Fig. 17 is a logical diagram of one embodiment of the operations of the UE equipment and the gNB node for switching the COT interval;

Fig. 18 is a timing diagram of one embodiment of gNB-initiated COT intervals and UE-initiated COT intervals highlighting the overlap of COT intervals;

Fig. 19 is a logical diagram of one embodiment of the operations of the UE equipment and the gNB node for accessing the communication channel, highlighting the dynamic change of COT intervals;

Fig. 20 is a logical diagram of one embodiment of the operations of the UE equipment and the gNB node for accessing the communication channel, highlighting the confirmation of initiation of the COT interval for the UE equipment;

Fig. 21 is a timing diagram of one embodiment of gNB-initiated COT intervals and UE-initiated COT intervals, highlighting non-overlapping COT intervals occupying the communication channel;

Fig. 22 is a logical diagram of one embodiment of a method for initiating a COT interval for UE equipment;

Fig. 23 is a logical diagram of another embodiment of a method for initiating a COT interval for a UE;

Fig. 24 is a diagram of one of the variants of the processor system;

Fig. 25 is a diagram of one of the variants of the transceiver; and

Fig. 26 is a diagram of one embodiment of the operations of the gNB node and the UE equipment.

Corresponding reference numerals and symbols in the various drawings generally refer to corresponding parts unless specifically indicated otherwise. The drawings are designed to clearly illustrate the corresponding aspects of the embodiments shown and are not necessarily drawn to scale.

Detailed description of illustrative variants

The manufacture and use of embodiments of the present invention are discussed in detail below. However, it should be understood that the concepts discussed herein may be implemented in a wide variety of specific contexts, and that the specific embodiments discussed herein are merely illustrative and do not serve to limit the scope of the Claims. It should further be understood that various substitutions, replacements and changes may be made without departing from the spirit and scope of the present invention as defined by the appended Claims.

Communication in the unlicensed spectrum uses the "Listen Before You Talk" (LBT) channel access. The transmitter performs a channel clearance assessment (CCA) to determine whether the channel is available for transmission. If the channel is assessed to be available, the transmitter may transmit for a channel busy time (COT) interval duration. A COT interval is a period of time during which a communication device, such as a user equipment (UE) or a gNB, may transmit on the channel in question without having to re-assess the availability of the channel. During a COT interval, a communication device may have multiple transmissions and may allow other communication devices to share the COT interval (i.e., transmit within the shared COT interval). Typically, only a gNB may initiate a COT interval (i.e., the gNB is the device that first transmits within the COT interval), and the gNB may share the COT interval with UEs. A UE in the frame-based equipment (FBE) mode cannot initiate a COT itself, so it must use a COT shared with a gNB for its transmissions. The gNB may schedule an uplink grant in the COT initiated by the gNB for uplink transmissions performed by the UE.

The restriction that only the gNB can initiate a COT interval may result in unnecessary delays and overhead for uplink (UL) transmissions. As an example, a UE that has data to transmit on the uplink (UL) may need to wait until a gNB-scheduled COT interval begins. When the UE has no data to transmit, the UE may still need to monitor each scheduled COT interval, which results in unnecessary consumption of UE battery power and radio spectrum.

Embodiments of the present invention propose a method for initiating a COT interval by a UE in an FBE mode. In some embodiments, a UE in an FBE mode may determine that a communication channel in an unlicensed spectrum region is available for use and transmit on this communication channel to a gNB in a fixed frame period (FFP) associated with this UE in order to initiate a channel busy time (COT) interval within this FFP period for this UE. The transmission begins at the beginning of the considered FFP period and ends before the onset of a free period within this FFP period. The gNB receives this transmission and determines, based on the reception of the transmission, that the UE has initiated the COT interval. In other words, this UE is the device that first transmits in the considered COT interval. The gNB may confirm or reject the initiation of this COT interval by the UE. If the gNB does not reject the initiation, the UE may continue to communicate with this gNB in the COT interval initiated by this UE. The UE does not need to re-evaluate the availability of the communication channel during the COT interval initiated by this UE. Thus, when the UE has uplink data to transmit, this UE does not need to wait to share the COT interval initiated by the gNB to transmit uplink data in this COT interval initiated by the gNB. The UE may initiate a COT interval itself to transmit uplink data. The proposed embodiments facilitate UE communication in the FBE mode in an unlicensed spectrum region with reduced latency, overhead and battery consumption.

Fig. 1 illustrates an example of a radio communication system 100. The communication system 100 includes an access node 110 with a coverage area 111. The access node 110 serves several user equipment (UEs), including a UE 120 and a UE 122. Transmissions from the access node 110 to the UEs are called downlink (DL) transmissions and occur on a downlink (shown in Fig. 1 as a thick line with arrows), while transmissions from the UEs to the access node 110 are called uplink (UL) transmissions and occur on an uplink (shown in Fig. 1 as a dashed line with arrows). Services for several UEs are provided by service providers connected to the access node 110 via a transport network 130, such as the Internet. The communication system 100 may include a plurality of distributed access nodes 110.

In a typical communication system, several modes of operation are used. In the cellular mode, communication from and to multiple UEs passes through the access node 110, although direct communication between devices is also possible, for example in the proximity services (ProSe) mode, where, for example, direct communication between UEs is possible. Access nodes may also be commonly referred to as Node B, evolved Node B (eNB), next generation (NG) Node B (gNB), master eNB (MeNB), secondary eNB (SeNB), master gNB (MgNB), secondary gNB (SgNB), network controllers, control nodes, base stations, access points, transmission point (TP), transmission-reception point (TRP), cells, carriers, macro cells, femto cells, pico cells, repeaters, customer premises equipment (CPE), etc. The UE equipment units may be generally referred to as mobile stations, mobile devices, terminals, terminal devices, users, subscribers, stations, communication devices, CPE equipment, repeaters, Integrated Access and Backhaul (IAB) repeaters, and other similar names. It should be noted that when relaying is used (based on repeater stations, pico cells, CPE equipment, etc.), in particular multi-hop relaying, the boundary between a controller and a node controlled by this controller may become blurred, so that a dual node (either a controller or a node controlled by this controller) may be deployed, where the first node, which provides the second node with information for configuring or controlling the second node, is considered to be the controller. Similarly, the concept of uplink (UL) and downlink (DL) transmissions may also be extended.

A cell may contain one or more uplink (UL) or downlink (DL) bandwidth parts (BWPs) assigned to a UE. Each BWP may have its own BWP-specific numerical characteristics and configuration. Note that not all BWPs need to be active at the same time for a given UE. One cell may correspond to one or more carrier frequencies. Typically, one cell (primary cell (PCell) or secondary cell (SCell), for example) corresponds to a component carrier (primary component carrier (PCC) or secondary CC (SCC), for example). For some cells, each cell may have multiple uplink (UL) carriers, one such carrier is called an uplink (UL) carrier or non-supplementary (non-SUL) carrier (hereinafter referred to as non-SUL carrier) for which there is an associated downlink (DL) carrier, and the other carriers are called supplementary UL carriers (SUL carriers) for which there are no associated DL carriers. A cell or carrier may be configured in a format of slots or subframes containing downlink (DL) symbols and uplink (UL) symbols, and this cell or carrier is represented as operating in time division duplexed (TDD) mode. In general, for unpaired spectrum, the cells or carriers operate in TDD mode, and for paired spectrum, the cells or carriers operate in frequency division duplexed (FDD) mode. The access nodes may provide radio access according to one or more radio protocols, such as long term evolution (LTE), LTE advanced (LTE-A), 5G, 5G LTE, 5G NR, High Speed Packet Access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. While it is understood that communication systems may employ multiple access nodes capable of communicating with multiple UEs, only one access node and two UEs are shown in the figure for simplicity.

Fig. 2 illustrates an example of a communication system 200 and mathematical expressions for signals transmitted in this communication system 200. The communication system 200 includes an access node 205 communicating with a UE 210. As shown in Fig. 2, the access node 205 uses a transmit filter v and the UE 210 uses a receive filter w. Both the access node 205 and the UE 210 use linear precoding or combining. Assume that the channel matrix (or channel model or channel characteristic) H is a matrix of size N _rx x N _tx for a multiple-input multiple-output (MIMO) system, i.e., there are N _tx transmit antennas and N _rx receive antennas. A transmit filter v of size N _tx x Ns allows the transmitter to perform precoding or beamforming of the transmitted signal, where Ns denotes the number of transmitted layers, ports, streams, symbols, pilots, data messages or known sequences. A receive filter w in a multi-antenna system has dimensions N _rx x Ns and is a combining matrix that is typically applied to a received signal y according to the expression w ^H y. The above description applies to transmission from the access node 205 to the UE 210, i.e., to the downlink (DL) transmission (DL transmission). Transmission may also occur in the reverse direction (uplink (UL) transmission (UL transmission)), for which the channel matrix in this case becomes the matrix H ^H for the TDD case (where H ^H is the result of applying the Hermite operator to the communication channel model H), and w can be considered as a transmit filter and v as a receive filter. The transmit filter w and the receive filter w may or may not be the same filter, and the same applies to the filter v.

The downlink (DL) channel 215 (or forward channel) between the access node 205 and the UE 210 has a channel model or characteristic of H, while the uplink (UL) channel 220 (or reverse channel) between the UE 210 and the access node 205 has a channel model or characteristic of H ^H . (In another notation, the UL channel is denoted as H ^T , which is the result of transposing the channel model H .) Although only one access node and one UE are shown in FIG. 2, the communication system 200 is not limited to this case. Multiple UEs may be served by a single access node using different time-frequency resources (e.g., as in frequency division multiplexed-time division multiplexed (FDM-TDM) communication systems, as in typical cellular communication systems) or using the same time-frequency resources (as in multi-user MIMO (MU-MIMO) communication systems, where multiple UEs are paired and the transmissions for each UE are individually precoded). There is intra-cell interference among paired UEs.

In addition, there may be multiple access nodes in the communication network, such that some of these nodes may jointly serve the UE 210 in a joint transmission mode (such as coherent joint transmission, non-coherent joint transmission, coordinated multipoint transmission, etc.), in a dynamic point switching mode, etc. Some other access nodes may not serve the UE 210, and their transmissions for their own UEs serve these nodes create inter-cell interference for the UE 210. A scenario with multiple access nodes and multiple UEs, where the access nodes cooperate with each other to serve the UE, and there is a MU-MIMO system, represents one example of the scenarios considered here.

One way to increase the amount of network resources may be to use more and more usable spectrum resources, which include not only licensed spectrum resources of the same type as macrocell resources, but also licensed spectrum resources of other types than macrocells (e.g., a macrocell may be an FDD cell and a small cell may use both FDD and TDD carriers), as well as unlicensed spectrum resources and shared licensed spectrum; some of these spectral resources may be in the high frequency bands, such as the 6 GHz to 60 GHz bands. Unlicensed spectrum may be used generally by any user, subject to regulatory requirements. Shared licensed spectrum may also not be owned exclusively by any one operator. Traditionally, unlicensed spectrum areas are not used by cellular networks, since it is usually difficult to meet quality of service (QoS) requirements. Unlicensed spectrum areas are mainly used by wireless local area networks (WLANs), such as Wi-Fi networks. Due to the fact that licensed spectrum areas are usually scarce and expensive, the use of unlicensed spectrum area by a cellular operator can be considered. Note that in high frequency bands and in unlicensed/shared licensed bands, time-division multiplexing (TDD) is usually used, so that channel reciprocity can be used for communication.

In unlicensed spectrum areas, there is usually no prior coordination between multiple nodes operating on the same frequency resource. Thus, a contention-based protocol (CBP) may be used. According to Section 90.7 of Part 90 (paragraph 58) of the United States Federal Communication Commission (FCC), the CBP protocol is defined as follows:

"A protocol that allows multiple users to share the same spectrum by defining events that may occur when two or more transmitters attempt to simultaneously access the same communication channel and establishing rules by which one transmitter provides reasonable opportunity for other transmitters to operate. Such a protocol may contain procedures for initiating new transmissions, procedures for determining the state of the communication channel (available or unavailable), and procedures for managing retransmissions when the communication channel is busy."

Note that the state of a busy communication channel can also be called "channel unavailable", "channel not free", "channel not clear", "channel busy", etc., and the state when the channel is not in use can also be called "channel available", "channel free", "channel clear", "channel not busy", etc.

One of the most widely used CBP protocols is the Listen Before Talk (LBT) procedure defined in the IEEE 802.11 or Wi-Fi standard (which can be found, for example, in the document “Wireless LAN medium access control (MAC) and physical layer (PHY) specifications”, IEEE Std. 802.11-2007 (Revision of IEEE Std. 802.11-1999), which is hereby incorporated by reference in its entirety). One way to implement the Listen Before Talk (LBT) mode is to use the carrier sense multiple access with collision avoidance (CSMA/CA) protocol. According to the CSMA/CA protocol, carrier sensing is performed before any transmission attempt, and transmission is performed only if the carrier is found to be idle, otherwise, if the carrier is busy, a randomly determined countdown time is applied for the next carrier sensing. Carrier sensing is typically performed using a CCA estimation procedure to determine whether the power level in the communication channel is below a certain threshold.

ETSI EN 301 893 V2.1.1 (which is hereby incorporated by reference in its entirety) in Clause 4.9.2, describes two (2) types of Adaptive Equipment: Frame Based Equipment (FBE) and Load Based Equipment (LBE), where the following is specified (extract from ETSI EN 301 893 V2.1.1, Clause 4.9.2).

Frame Based Equipment must meet the following requirements:

1) Before commencing transmissions on a working channel, the equipment shall perform a channel clearance assessment (CCA) using "energy measurement". The equipment shall monitor the working channel(s) for a CCA monitoring time, which shall be at least 20 µs. The CCA monitoring time used by the equipment shall be declared by the equipment manufacturer. A working channel shall be considered occupied if the energy level on that channel exceeds the threshold corresponding to the power level specified in paragraph 5 below. If the equipment detects that the working channel(s) is clear, it may commence transmission immediately (see paragraph 3 below).

2) If the equipment detects that the working channel is busy, it shall not transmit on this communication channel during the next fixed frame period.

Note 1: Equipment is permitted to continue Short Control Signaling Transmissions on this communication channel provided that this communication channel meets the requirements of clause 4.9.2.3.

Note 2: Equipment having simultaneous transmissions on multiple (adjacent or non-adjacent) working communication channels is permitted to continue transmissions on other working communication channels provided that the CCA assessment has not detected any signals on these channels.

3) The total time during which the equipment may transmit on a particular link without re-evaluating the availability of that link is defined as the Link Busy Time Interval. This Link Busy Time Interval shall be in the range from 1 ms to 10 ms and the minimum free period shall be at least 5% of the Link Busy Time Interval used by the equipment for the current fixed frame period. At the end of the free period, the equipment shall perform a new CCA assessment as described in paragraph 1 above.

4) The equipment, after correctly receiving a packet intended for that equipment, may skip the CCA assessment and proceed immediately (see note 3) to transmit control and management frames (e.g. acknowledgement (ACK) and block ACK frames). The chain of such successive transmissions performed by the equipment without performing a new CCA assessment shall not exceed the maximum channel busy time interval as defined in paragraph 3 above.

Note 3: For multicast purposes, transmissions of acknowledgements (ACKs) (associated with the same data packet) from individual devices are permitted to be made in sequence.

5) The threshold value for the energy measurement during the CCA assessment shall be proportional to the maximum transmit power (PH) of the relevant transmitter: for an effective isotropically radiated power (e.i.r.p.) of the transmitter equal to 23 dBm, the threshold level (TL) of the CCA assessment shall be no more than -73 dBm/MHz at the input of the receiver (assuming a 0 dBi receiving antenna). For other transmitter power levels, the threshold level TL for the CCA assessment shall be calculated using the formula: TL = -73 dBm/MHz + 23 - PH (assuming a 0 (zero) dBi receiving antenna and a power PH specified in units of dBm e.i.r.p.).

“Load based Equipment may implement a spectrum sharing mechanism based on the LBT mode, which relies on the channel occupancy assessment (CCA) mode using “energy measurement” as described in IEEE 802.11™-2007 [9], clauses 9 and 17, IEEE 802.11n™-2009 [10], clauses 9, 11, and 20, subject to the conformance requirements specified in clause 4.9.3 (see note 1) (all of which are hereby incorporated by reference).

Note 1: This is intended to also allow the use of a mechanism based on the Channel Clearance Assessment (CCA) mode using "energy measurement" as described in IEEE 802.11ac™ [i.2], clauses 8, 9, 10, and 22 (which are hereby incorporated by reference) when available.

Load-based equipment that does not use any of the mechanisms mentioned above shall meet the following minimum set of requirements:

1) Before performing a transmission or a burst of transmissions on a working communication channel, the equipment shall perform a channel clearance assessment (CCA) using "energy measurement". The equipment shall monitor the working communication channel(s) for a CCA monitoring time, which shall be at least 20 µs. The CCA monitoring time used by the equipment shall be declared by the equipment manufacturer. A working communication channel shall be considered occupied if the energy level on that channel exceeds the threshold corresponding to the power level specified in paragraph 5 below. If the equipment detects that the working communication channel(s) is clear, it may start transmitting immediately (see paragraph 3 below).

2) If the equipment detects that the working communication channel is occupied, it shall not transmit on this channel. The equipment shall perform Extended CCA assessment, during which the working communication channel is monitored for a period of time equal to the product of a random factor N and the monitoring time for the CCA assessment. Here, the factor N determines the number of free slots forming a total free period that must be monitored before initiating a transmission. The value of N shall be chosen randomly in the range 1..q each time Extended CCA assessment is required and this value shall be recorded in the counter. The value of q shall be chosen by the manufacturer in the range 4..32. This chosen value shall be declared by the manufacturer (see clause 5.3.1 q)). The number in the counter is decreased each time a CCA assessment slot is found to be "unoccupied". When the counter reaches zero, the equipment may transmit.

Note 2: Equipment is permitted to continue to transmit short control signalling on this communication channel provided that this communication channel complies with the requirements of clause 4.9.2.3.

Note 3: Equipment having simultaneous transmissions on multiple (adjacent or non-adjacent) working communication channels is permitted to continue transmissions on other working communication channels provided that the CCA assessment has not detected any signals on these channels.

3) The total time during which the equipment uses the working communication channel is equal to the maximum time interval of the communication channel occupied, which shall be less than (13/32) × q ms, where the number q is defined in paragraph 2 above, after which the device shall perform an extended CCA assessment as described in paragraph 2 above.

4) The equipment, after correctly receiving a packet intended for that equipment, may skip the CCA assessment and proceed immediately (see note 4) to transmit control and management frames (e.g. acknowledgement (ACK) and block ACK frames). The chain of such successive transmissions performed by the equipment without performing a new CCA assessment shall not exceed the maximum channel busy time interval as defined in paragraph 3 above.

Note 4: For multicast purposes, transmissions of acknowledgements (ACKs) (associated with the same data packet) from individual devices are permitted to be made in sequence.

5) The threshold value for the energy measurement during the CCA assessment shall be proportional to the maximum transmit power (PH) of the relevant transmitter: for a transmitter effective isotropically radiated power (e.i.r.p.) of 23 dBm, the threshold level (TL) for the CCA assessment shall be no more than -73 dBm/MHz at the input of the receiver (assuming a 0 dBi receiving antenna). For other transmitter power levels, the threshold level TL for the CCA assessment shall be calculated using the formula: TL = -73 dBm/MHz + 23 - PH (assuming a 0 dBi receiving antenna and a power PH specified in units of dBm e.i.r.p.).

The above is an excerpt from ETSI EN 301 893 V2.1.1, Clause 4.9.2.

Fig. 3A and 3B show diagrams of conventional systems 300 and 350 for analog beam steering and digital beamforming. The system 300 shown in Fig. 3A includes a video baseband component 302 for digital processing, several high-frequency path components 304, several phase shifters 306, several combiners 308 and several antennas 310. The system 300 can be used for transmission or reception. For simplicity, the system in Fig. 3A is shown for transmission as an example; the principle of reception can be understood similarly. Each high-frequency path 304 receives a weighting coefficient (or weight, p ₁ , ..., p _m as shown in Fig. 3A) from the video baseband component 302. This set of weighting coefficients forms a digital precoding vector, a precoding matrix, a beamforming vector or a beamforming matrix for transmission. For example, the precoding vector may be a vector [ p ₁ , ..., p _m ]. When multiple layers/streams are transmitted, the video baseband component 302 may use a precoding matrix to generate weights, where each column (or row) of the matrix is applied to one layer/stream for transmission. Each high-frequency path is connected to several phase shifters 306. These phase shifters 306 can, in theory, apply any values of phase shifts, but in practice only a small number of possible values of phase shifts are used, for example, 16 or 32 values. Each high-frequency path 304 generates a narrow beam 312 oriented in a direction determined by the settings of the phase shifters 306 and the summers 308. If the phase shifters 306 can apply any values of phase shifts, the beam can point in any direction; but if only a small number of phase shift values can be used, the beam may be oriented in one of several possible directions (for example, as shown in Fig. 3A, a narrow beam (solid line) is selected by setting a specific phase shift value in the high-frequency path 304, and this beam is one of all possible narrow beams shown by the solid line and dashed lines and corresponding to all possible phase shift values). Each high-frequency path selects one such narrow beam, and all such narrow beams selected by all high-frequency paths (high-frequency paths 1 through N) will then be superimposed on one another. How exactly such superposition is carried out is based on digital weighting factors. The weighting factors can make the beam from the high-frequency path stronger or weaker, and therefore different sets of weighting factors can produce different superposition options in the spatial domain; in Fig. 3A, a specific beam 314 is illustrated. In other words, by selecting different digital weighting factors, different beams 314 can be generated. Digital operations for forming a beamform can be generally referred to as (digital) beamforming or precoding, and analog operations for forming a beamform can be generally referred to as (analog) beam position control or phase shift.

The system 350 shown in Fig. 3B is similar to the system 300 shown in Fig. 3A, except that the respective adders 308 in each high frequency path 304 are connected to one another.

An example of a timing diagram 400 for synchronizing transmissions for equipment based on the use of frames is shown in Fig. 4. The equipment, such as a unit under test (UUT), performs a CCA assessment for a communication channel before transmitting, and if the communication channel is found to be free (or available, not busy), this equipment transmits within a time interval of the communication channel being busy and then goes into an "idle" state (rest state) for the duration of a free period. During this free period, the equipment performs a CCA assessment to determine whether the communication channel is available.

An example of a logic diagram of a method 500 for carrier sensing is shown in Fig. 5. The method 500 shown in Fig. 5 begins with a block 502, in which a communication controller receives an analog signal from the UE equipment. In a block 504, the communication controller processes this signal and generates a decision variable, X. The signal processing here is performed mainly in the digital domain, which is typically done in the video range, and may include sampling, analog-to-digital (A/D) conversion, digital summation in the receiver using weighting using pre-coding weighting factors, etc. This decision variable, X, is used to determine whether the carrier channel is free or busy. In a block 506, the communication controller determines whether the decision variable is less than a threshold value, T. This threshold value may be a standardized value or may be determined from a standard or some normative documents and may be specific for a type of device, spatially specific, etc. The threshold value may be allowed to vary within a specified range in accordance with traffic loads, interference conditions, etc. If, in block 506, the communication controller determines that the value of the decision variable, X, is less than the threshold value, T, the method 500 proceeds to block 508, where the communication controller determines that the communication channel of the carrier in question is free, after which the implementation of the method 500 is completed. If, in block 506, the communication controller determines that the value of the decision variable, X, is not less than the threshold value, T, then the method 500 proceeds to block 510, where the communication controller determines that the communication channel of the carrier in question is busy, after which the implementation of the method 500 is completed.

A logic diagram of one embodiment of a method 600 for a general mechanism of the "listen before you talk" mode is shown in Fig. 6. The implementation of the method 600 shown in Fig. 6 begins with a block 602 in which the communication controller assembles a frame. In a block 604, the communication controller performs carrier sensing, such as the carrier sensing procedure described above with reference to Fig. 5, to determine whether the communication channel is idle. If in block 604 the communication controller determines that the communication channel in question is not free, but rather busy, then the method 600 proceeds to block 606, in which the communication controller refrains from transmitting the frame and waits until the randomly selected countdown time has expired, after which the method 600 returns to block 604. If in block 604 the communication controller determines that the communication channel in question is free, the method 600 proceeds to block 608, in which the communication controller transmits the specified frame, after which the implementation of the method 600 is completed.

Wi-Fi is a prime example of the listen-before-speak mechanism. Wi-Fi uses technologies from the 802.11 family of standards, such as the air interface (including the physical (PHY) layer and the MAC layer). In 802.11 standards, the communication channel (also called the radio channel) is shared among stations according to a mechanism called distributed channel access with a function called the distributed coordination function (DCF), which uses CSMA/CA technology. The DCF uses both the physical and virtual carrier sense functions to detect the state of the medium (i.e., the link). The physical carrier sense function resides at the physical (PHY) layer, and uses energy measurement and preamble detection separated from the frame length to determine when the link is busy. The virtual carrier sense function resides at the MAC layer and uses the reservation information carried in the Duration field in the MAC layer headers that indicate that the radio channel is being blocked. The virtual carrier sense mechanism is called the network allocation vector (NAV). A radio channel is determined to be idle only when the carrier sense mechanism, both physical and virtual, indicates that it is so. A station (e.g., STA 1) that has a data frame to transmit first performs a CCA assessment by sensing the radio channel for a fixed duration, the DCF inter-frame space (DIFS). If the radio channel is busy, the station waits until the channel becomes idle, pauses for the DIFS, and then waits for the next randomly set countdown period (setting a countdown timer with an integer number of slots). The number in the countdown timer is decreased by one in response to each free slot and is "frozen" when it is determined that the communication channel is busy. When the countdown timer reaches zero, the station begins transmitting data. The Wi-Fi communication channel access procedure 700, as described above, is shown in Fig. 7.

To meet regulatory requirements for operation in the unlicensed spectrum and to coexist with other radio access technologies (RATs) such as Wi-Fi, unlicensed spectrum transmissions cannot be continuous or constant over time. Instead, on/off or "opportunistic" transmissions and on-demand metering may be used.

In addition, high frequency bands, especially those between 28 GHz and 60 GHz, commonly referred to as the millimeter wave (mmWave) band, require very different propagation characteristics than the so-called microwave (MW) band (typically below 6 GHz). For example, mmWave has higher propagation losses over distance than the MW (microwave) band. Therefore, high frequency bands are more suitable for small cell operation than for macrocell operation, and these bands typically employ beamforming with a large number of antennas (e.g., >16, and in some cases, several hundred antennas) to ensure efficient transmissions. Note that at high frequencies, wavelengths, antenna sizes, and antenna spacings can all be smaller than at low frequencies, making it possible to equip a communications node with a large number of antennas. As a result, the beams formed by a large number of antennas can be very narrow (sharp), for example, with a beam width of 10 degrees or less. This is in sharp contrast to traditional radio communication systems, in which the beam width is typically much larger, for example, tens of degrees. Fig. 8A shows a radiation pattern with a wider beam 802 obtained using a small number of antennas at a low frequency. Fig. 8B shows a radiation pattern with a narrow (sharp) beam 804 obtained using a large number of antennas at a high frequency. In general, narrow (sharp) beams are considered to be the main new property of millimeter waves. As a general rule of thumb, the beamforming gain in a MIMO system with a large number of stations can be roughly estimated by the formula N x K, where N is the number of transmit antennas and K is the number of receive antennas. This is because the 2-norm of the channel characteristic matrix H roughly scales according to (N x K) ^1/2 _, and therefore, if the precoding vector at the transmitting node is denoted by p, and the summation vector at the receiving node is denoted by w, then the composite channel characteristic is w'Hp, and with the correct choice of the vectors w and p, the energy gain of the composite channel can reach N x K, which is much higher than in the case with a smaller number of antennas.

The New Radio (NR) standards do not specify a UE-initiated COT (i.e., a COT not scheduled by a gNB). The NR standards specify a gNB-initiated COT. During a gNB-initiated COT, the UE may be allowed to transmit as a COT sharer (i.e., the UE shares the gNB-initiated COT for transmissions). The gNB may configure the UE's transmission, including an indication of the LBT mode type that the UE should use as a COT sharer during the gNB-initiated COT. The UL channel access type (e.g., LBT mode) may be indicated by the gNB when scheduling the UL grant.

The LTE LAA and NR-U standard specifications define two types of operations for unlicensed bearer access based on bearer access timing, namely, load-based equipment (LBE) mode of operation and frame-based equipment (FBE) mode of operation.

In the LBE mode of operation, access to the unlicensed communication channel is not synchronized with an external clock signal, and the COT interval is initiated as soon as the CCA evaluation procedure is successful. Fig. 9 shows a timing diagram 900 of an example of synchronization of operations in the LBE mode. After each COT interval 910 within a fixed frame period (FFP) 930, the gNB node performs monitoring of the communication channel (e.g., CCA evaluation) in monitoring slots 920, and when the monitored communication channel is perceived as free, the gNB node starts a randomly initiated countdown counter. The number in this randomly initiated countdown counter is decreased for each monitoring slot 922 when it is detected that the communication channel is free. If during monitoring the communication channel is busy (e.g., in the monitoring slot 924), i.e. the CCA evaluation was unsuccessful, the process of decreasing the number in the countdown counter is stopped.

Fig. 10 shows a timing diagram 1000 of synchronization of operations in the FBE mode according to the TS 37.213 standard. In the FBE mode of operation, the gNB node performs an LBT mode operation (for example, extended CCA assessment) in each time interval T (period) in the communication channel, for example, during a free period. If, according to the LBT mode operation, the communication channel is free, the gNB node can initiate a COT interval 1010 of duration Ty, which is a certain fraction of the repetition period (T). In other words, the gNB node is the entity that first starts using the COT interval for transmission. This COT interval 1010 is initiated periodically in every fixed frame period (FFP) T in two consecutive radio frames, starting from the radio frame with an even index at the time x∙T, with a maximum channel occupancy time interval Ty=0.95*T, where T denotes the FFP period in ms, which is also known as a frame and is a higher layer parameter, and the parameter x is an integer representing the period number (i.e., the FFP period number). This type of access is called semi-static channel occupancy in TS 37.213. Only the gNB can initiate a COT interval in the FBE mode. As shown in Fig. 10, each FFP period contains a COT interval 1010 starting from the start of this FFP period and a free period following that interval. The gNB performs CCA evaluation before the start of the next FFP period, for example, during the free period in the current FFP period. If the link is found to be available (not busy or clear) based on the CCA assessment, the gNB may initiate a COT 1010 interval in the next FFP period.

In the FBE mode of operation, the UE receives information about the FFP period from the gNB, such as the starting position of the FFP period and the duration of this FFP period. UE transmissions within this FFP period may occur if one or more of the following downlink (DL) signals/channels (e.g. physical downlink control channel (PDCCH), synchronization signal block (SSB), physical broadcast channel (PBCH), remaining minimum system information (RMSI), or configured grant (CG)-PDCCH) are detected within this FFP period.

TS 37.213 defines a periodic COT interval (with period T= FFP) triggered by a gNB (as discussed above), and such a periodic COT interval may be referred to as a periodic COT interval of the first type. A COT interval may be referred to as a period of time during which the link is "owned" by the initiator that initiated this COT interval. During this COT interval, the initiator may have several transmissions and may allow other devices, such as a receiver, to share this COT interval in the sense that this receiver may also make some transmissions. The initiator that initiates a COT interval may be understood as the initiator that first starts transmitting at the beginning of the FFP period associated with this COT interval after verifying that the channel is idle and other devices that share this COT interval may transmit only after the initiator initiates this COT interval and grants grants for sharing this COT interval. In the NR specifications of Release 16 or later, the UE cannot be an initiator, and only the gNB can initiate a COT interval. In other words, the UE can use a COT interval only after this COT interval is initiated by the gNB (after the gNB starts transmitting in the COT interval) and the gNB grants the UE permission to share the COT interval in question. For example, the gNB may initiate a COT interval, transmit in the downlink (DL), and schedule the UE to share the COT interval. The UE equipment receives a downlink (DL) transmission and may then perform an uplink (UL) transmission according to a scheduled COT interval. The LBT procedure performed during the COT interval may be different from the LBT procedure performed outside the COT interval, and more specifically, the LBT procedure performed during the COT interval may be very short, and a deterministic period may be used to perform the CCA assessment, or if the interval between successive transmissions is shorter than a predetermined period, for example, 16 μs, the CCA assessment (in the LBT mode) is not needed.

Before initiating a COT interval in the FBE mode, the gNB, in accordance with TS 37.213, shall perform an advanced CCA procedure, which is called LBT Category 4 in 3GPP documents and which is related to the basic LBT mode. This basic LBT mode procedure contains a truncated exponential countdown based on energy detection (ED). During this procedure, the gNB monitors the link and if the link is detected to be idle (i.e., low energy is detected on the link), the gNB starts a countdown counter, initialized with a random number, so that the number in the counter is decremented each time the link is detected to be idle in the monitored slot. When the number in the randomly initiated countdown counter reaches zero, the gNB can initiate a COT interval; Otherwise, if the randomly initiated countdown counter does not reach zero before the COT interval expires, the gNB node shall skip the current transmission opportunity (i.e., the current FFP period), and wait for the next period to initiate a COT interval for transmissions. The terms "transmission opportunity" and "opportunity" are used interchangeably throughout the description of the present invention.

The restriction that only the gNB can initiate a COT interval for the FBE mode, as noted above, may result in unnecessary delays for uplink (UL) transmissions or overhead. For example, if the UE is a security camera in which uplink (UL) transmissions are triggered by motion detection, the UE's uplink (UL) traffic may be delayed by one FFP period at best. In such a case, the gNB may schedule a periodic COT interval if the channel is idle and schedule UL grants to the UE even if the UE has no data to transmit. This results in wasted battery power and spectrum at the UE, since the UE needs to monitor each of the periodic COT intervals.

This problem discussed above can be avoided if the UE equipment can initiate COT intervals in the FBE mode itself. Using the example above, if the video camera in the UE equipment can initiate COT intervals in the FBE mode itself, this video camera in the UE equipment can start a periodic COT interval as soon as motion is detected, and cancel this periodic COT interval when the video transmission is completed or stopped.

Embodiments of the present invention propose a method for initiating a COT interval by a UE in the FBE mode, which will reduce delays and overhead. When the UE has data to transmit, the UE does not need to wait for the gNB to initiate a COT interval in the FFP period and schedule/allow the UE to share this COT interval initiated by the gNB, and the UE then transmits in the shared COT interval initiated by the gNB. Instead, the UE itself can initiate a COT interval within the FFP period to transmit in the COT interval initiated by the UE. In other words, the UE can determine whether the communication channel is idle before the FFP period, and if the communication channel is idle, the UE can start transmitting at the beginning of the FFP period to initiate a COT interval within the FFP period. The UE is the entity that first starts transmitting within the FFP period. The proposed embodiments define additional types of UE-initiated periodic COT (semi-static channel access) intervals. In various embodiments, a UE may be able to initiate a COT interval periodically associated with an FBE mode of operation. For a UE-initiated COT interval, the UE may be referred to as the initiator and owner of the COT interval, and only the UE that initiated the COT interval may grant the right to transmit during the COT interval owned by the UE. The UE may share the COT interval with other devices, such as a gNB or other UEs. A periodic COT interval is a COT interval that may be initiated periodically, such as every FFP period within a configured time interval. In various embodiments of the present invention, a UE may initiate a single COT interval or a periodic COT interval.

In some embodiments, UE-initiated periodic COT intervals of a second type are proposed. With respect to COT intervals of this type, the gNB may, by means of start positions and possible end positions, provide the UE with a time interval T_UE_COT, in which the UE may initiate periodic COT intervals. The time interval T_UE_COT denotes an interval during which the UE is allowed to initiate a COT interval or a periodic COT interval. The time interval T_UE_COT may be denoted using a start position of the time interval and an end position of the time interval, or in other ways. For example, the start position and the end position of the time interval may be expressed or denoted in terms of a frame index or a number of frames by signaling. The gNB may also provide a configuration for an FFP period (also referred to as an FFP period configuration) to the UE initiating the COT interval. This FFP period may also be simply referred to as a "period" within the scope of the present invention. The FFP period configuration may contain an FFP period value, for example indicating the length (duration in time) of this FFP period. If the FFP period value is not present, the UE may take into account the last FFP period value used by the serving cell/gNB, for example. At the beginning of each FFP period, there is an opportunity for the UE to initiate a COT interval. This opportunity is here called a COT opportunity or a periodic COT opportunity. If the UE does not use this opportunity to initiate a COT, the UE loses this missed COT opportunity, so it needs to wait for the next COT opportunity to initiate a COT. As will be discussed below, the UE may transmit uplink using the COT opportunity for the current FFP period, i.e., at the beginning of the current FFP period, which (opportunity) initiates a COT interval for the current FFP period. Then the UE may own the COT interval in the current FFP period and transmit during this UE-initiated COT interval in the current FFP period. If the UE does not initiate a COT interval in the current FFP period, the UE may initiate a COT interval for the next FFP period or another FFP period in the future using the same mechanism.

These options are different from the buffer status report (BSR), where the UE transmits a scheduling request (SR) and the gNB allocates resources for uplink (UL) transmission. For the BSR, transmission opportunities in the COT must be scheduled, which must be initiated by the gNB, and the UE never has "ownership" of the COT. In these options, the gNB is not required to initiate a COT. The UE can initiate and own a COT, which can be shared with the gNB, for example.

Embodiments of the present invention also propose a technical solution that allows multiple UEs to compete and initiate a COT interval during FBE operation. The gNB node can acknowledge the "winner" of the competition between the UEs as the owner of this COT interval.

In some embodiments, the gNB may assign a T_UE_COT time interval (as shown in FIG. 12) for UE-initiated COT intervals to either a single UE or a group of UEs. If the T_UE_COT time interval for UE-initiated COT intervals is assigned to a single UE, the UE may initiate a periodic COT interval immediately after successfully completing an extended CCA (e.g., LBT Category 4) procedure during this T_UE_COT time interval. The period (FFP) for this periodic COT interval may be provided by the gNB. The type of LBT mode for the UE to implement may be provided by the gNB, or, for example, the UE may use the default LBT Type 1 mode or use the short-term deterministic LBT mode for monitoring the link. In another embodiment, the LBT type and the FFP period may be obtained by the UE from a higher layer configuration.

The FFP for initiating a COT interval by the UE may be configurable or pre-configured. The FFP for initiating a COT interval by the UE may be provided by the gNB. Possible FFP period values may be the same or different from the FFP period values for a gNB-initiated COT interval. In some embodiments, the FFP period value may be provided for a single COT interval, which may correspond to an equivalent infinite period duration. LBT may still be required or implemented during the infinite period duration for transmissions. In another embodiment, the FFP period configuration may signal that only a short COT interval may be initiated for short control signaling transmissions. A short COT interval would not require LBT to be implemented as specified for short control signaling transmissions in ETSI standard specifications (e.g., ETSI EN 301 893 V2.1.1 (2017-05)). In some embodiments, the period for a UE-initiated COT interval may be the same as the FFP period for downlink (DL) transmissions (DL FFP) for the gNB, or always the same as for a one-time COT interval, or may have a fixed value, either as a desired operation or before granting RRC control. A configured or otherwise known period for a UE-initiated COT interval may be redefined by informing the UE of a "gap" or by informing the UE of a "new period", where the value of this "new period" is for one or more initiated COT intervals, or for some small or limited number of allowed or configured values. Transmissions during this COT interval may be considered as a buffer status report, but at a more physical layer.

The FFP period values may be different (e.g., one-time or infinite period) by default for certain types of traffic (e.g., infrequent alarms). The FFP period configuration may also indicate to the UE that it should operate in a gNB-initiated COT, where the UE is required to use the FFP period configuration set by the gNB. In other words, the UE may transmit using the gNB-initiated COT according to the corresponding FFP period configuration set by the gNB. In some embodiments, the UE may be instructed to switch between transmitting using the UE-initiated COT and transmitting using the gNB-initiated COT.

In some embodiments, the T_UE_COT time interval may be divided into periods (FFP), and these periods may be determined (configured) by the gNB or by higher layer configuration. For example, the T_UE_COT time interval may contain several FFP periods, and the number of these FFP periods may be determined by the communication network. At the beginning of each period, the UE may select or decline to start a COT interval or a periodic COT interval for the FFP period. To select (i.e., determine whether to start or initiate a COT interval for the UE or a periodic COT interval for the UE during the FFP period), the UE shall first perform the LBT procedure, and if this LBT procedure is successful, the UE will proceed to its transmissions in the COT interval of the FFP period in question. For failure, the UE may skip the LBT mode procedure and make a very short transmission in the uplink (UL) to indicate that it will miss the corresponding opportunity to start a COT interval or a periodic COT interval. The said short transmission in the uplink (UL) may be a message in the uplink (UL) about the gap and may be a simple sequence predefined in such a way as to make it more reliable.

If the UE misses one opportunity in the T_UE_COT interval, it may use the next opportunity to initiate a COT interval within the T_UE_COT interval, unless the UE is prohibited from doing so by the gNB, for example by a special message. In such a case, the gNB may take away the remainder of the T_UE_COT interval.

The COT interval may be a COT interval initiated by the UE as soon as the UE has information to transmit on the uplink (UL) (e.g., a PUCCH, a PUSCH, an SR request, or an SRS signal) after the LBT procedure has been successful before the start of the FFP period. In other words, the UE may initiate a COT interval when it transmits on the uplink (UL) in the FFP period associated with this COT interval. This UL transmission may start at the start of the FFP period in question (or at the start of a COT opportunity within this FFP period) and end before a free period within this FFP period occurs. The UL transmission from the UE that carries the signal in the uplink to initiate the COT interval may be referred to as the first transmission of the UE in this COT (opportunity). Other transmissions in this COT interval will be after the first transmission and will be completed before the free period within the FFP period. The gNB that receives such a first transmission may determine that the UE initiates a COT interval in the FFP period in question. The frequency resources for this uplink (UL) transmission may be provided in advance by the gNB, or the gNB may determine a cyclic shift, as when receiving the RACH. This UL transmission may contain, for example, a PUCCH, a PUSCH, a scheduling request (SR), a sounding reference signal (SRS), or channel state information (CSI) (such as a channel quality indicator (CQI)). This UL transmission may be transmitted using some predefined resources. In one embodiment, the UE may initiate a COT interval using the entire channel or a subset of carriers. If a subset of carriers is used, the gNB may need to perform scheduling for UEs in such a way as to satisfy the minimum channel bandwidth occupancy requirement.

In one embodiment, the UE may inform the gNB whether it intends to use the next FFP period or to skip this next FFP period. For example, the UE may be allowed to initiate multiple COT intervals within the T_UE_COT time interval. The UE may inform the gNB that it will skip a certain number or all COT interval opportunities within the T_UE_COT interval, or initiate some or all COT intervals within the T_UE_COT interval. This information allows the gNB to reuse unused COT interval opportunities initiated by the UE, which (the opportunities) may be assigned to other UEs or for another type of traffic.

In some embodiments, the gNB may assign a T_UE_COT time interval to a group of UEs. In this case, the T_UE_COT interval is a time interval during which the group of UEs is allowed to initiate a COT interval. In this case, the group of UEs competes for the right to initiate a COT interval within an FFP. In order to avoid collisions between multiple UEs that have successfully completed the Category 4 LBT (extended CCA) procedure before the periodic COT opportunity, an additional countdown procedure follows immediately after the initial LBT procedure as part of the COT initiation procedure. In other words, each UE performs a COT initiation procedure within the T_UE_COT interval in accordance with the periodic COT opportunity. During the COT initiation procedure, each UE performs a CCA assessment to determine whether the communication channel is free. If the communication channel is free, the UE may immediately perform an additional countdown procedure. During this additional countdown procedure (also called the post-CCA countdown procedure), each UE that has successfully passed the LBT mode procedure generates a random number R to initiate a countdown counter and continues monitoring the communication channel. The number in the countdown counter is decreased each time in the next slot it is determined that the monitored channel in this slot is free. The UE may initiate a COT interval when R=0 is reached. The initial value of R in the countdown counter in each UE may be provided by the gNB, configured by higher layers, or be equal to a predefined default number. In one example, the initial value of R in the countdown counter for each UE may be proportional to the number of UEs in the group in order to reduce the chances of collisions.

Note that in Internet of things (IoT) applications, the uplink (UL) traffic may be uneven and may be triggered by an event in the field or by measurement results. In this case, the additional countdown period at the beginning of the COT opportunity (start of the FFP period), which may be the last few symbols, is not expected to affect the throughput during the COT interval, which may be milliseconds.

In one embodiment, the gNB may provide each UE with its own initial range of random numbers (e.g., contention window (CW)) with the ability to give higher priority to some UEs (shorter CW). For example, each UE in the group may be configured with a CW window. One or more UEs may have a higher priority (e.g., with shorter CW windows) than other UEs (with longer CW windows). In another embodiment, each UE may use an initial range of a countdown counter based on the priority of its traffic. For example, each UE may be configured with an initial range of a countdown counter based on the priority of its traffic.

Fig. 11 shows a timing diagram 1100 of one embodiment of synchronization of operations of the UE equipment, highlighting the CCA evaluation procedure after a countdown. In this example, a group of UE equipments is configured to initiate periodic COT intervals for each COT interval opportunity using the CCA evaluation procedure after a countdown. A UE equipment in the group may transmit in a COT interval 1102 initiated by this UE equipment for the first COT interval opportunity. After the expiration of the COT interval 1102, this UE equipment may enter a free period 1104 and then perform a CCA evaluation (in a time domain 1106) before the start of the next (second) COT interval opportunity. When the CCA evaluation is successful, the UE equipment may begin an additional countdown procedure and continue monitoring the communication channel. The randomly initiated countdown counter starts with an initial value stored in it. If, during the additional countdown procedure, the communication channel is idle, in other words, the number in the randomly initiated countdown counter decreases to zero (in time domain 1108), the UE may initiate a COT interval 1110 for the second COT interval opportunity, for example by performing a transmission on the uplink (UL) in the second COT interval opportunity, and continue transmissions within the initiated COT interval 1110. The UE stops its transmissions when it enters a free period 1112 after the end of the COT interval 1110, and performs a CCA assessment in time domain 1114 to determine whether it can initiate a COT interval 1116 for the next (third) COT interval opportunity. If the CCA assessment is unsuccessful, the UE may cancel the third COT interval opportunity. In other words, the UE skips the third COT interval opportunity for transmissions. The UE may perform a CCA assessment before the next (fourth) COT opportunity (in time domain 1118) and this CCA assessment may be successful. In this case, the UE may start an additional countdown procedure and continue monitoring the link in time domain 1120. If the link is occupied in one of the monitoring slots during the additional countdown procedure, this additional countdown procedure fails. In this case, the UE will be unable to initiate a COT 1122 during the fourth COT opportunity, and thus cancels the fourth COT opportunity. The above operations may be performed by each UE in the group.

In some embodiments, after a successful uplink (UL) transmission from the UE initiating a COT interval, the fact that the COT interval has started or been initiated may be acknowledged (ACK) by the gNB via a downlink (DL) transmission, for example, on a PDCCH that schedules an uplink (UL) grant for the UE, or via a hybrid automatic repeat request acknowledgement (HARQ_ACK) in response to the indicated first uplink (UL) transmission. For example, the UE may send an uplink (UL) transmission to the gNB to initiate a COT interval within an FFP period. The gNB may successfully receive the uplink (UL) transmission and send a downlink (DL) transmission to the UE to acknowledge or confirm the initiation of the COT interval by the UE. Note that if multiple UEs are allowed to compete for the right to initiate a COT interval, each UE may have its own different time advance (TA) for uplink (UL) transmissions while remaining synchronized with the gNB via the primary synchronization signal/secondary synchronization signal (PSS/SSS) from that gNB.

In another embodiment, the first transmission from each UE (i.e., the uplink (UL) transmission used to initiate or start a COT interval) may be scrambled using a UE-specific code, such that if two or more UEs send uplink (UL) transmissions at the same time, these UL transmissions may be decoded by the gNB. In one embodiment, only one COT interval for a UE may be stored and acknowledged with a gNB ACK. In other words, the gNB may select one of the UEs that sent it uplink (UL) transmissions as the owner of the COT interval in question and acknowledge or confirm the initiation of this COT interval by the selected UE. This acknowledgement may be unicast - for only one UE, or multicast, where the COT interval for the UE-owner of the interval is identified, for example, by a sequence. In the unicast case, downlink control information (DCI) scrambled with a radio network temporary identifier (RNTI) may be used. In the multicast case, individual DCI or common DCI for a group scrambled with a group RNTI may be used, and the content of this DCI contains the identifier of the UE that owns the COT in question, for example by means of a sequence encoded in the DCI information field.

In some embodiments, multiple UEs may share a single COT interval initiated by multiple UEs. The gNB may acknowledge the shared COT interval for multiple UEs and provide, as feedback to each UE, an assignment of resources for transmissions from those UEs.

Fig. 12 shows a time diagram of one embodiment 1200 of synchronizing the operations of the UE, allocating a T_UE_COT time interval assigned to a group of UEs and acknowledging the COT intervals initiated by these UEs. In this example, the group of UEs is configured to be able to initiate periodic COT intervals for each COT opportunity within the T_UE_COT time interval. The UE may perform an additional countdown procedure (in time domain 1202) after a successful CCA assessment and start it at the beginning of the COT opportunity (the beginning of the FFP period). If the communication channel is found to be idle during the additional countdown procedure, the UE may initiate a COT interval for the COT opportunity in question, for example by sending an uplink (UL) transmission to the gNB within this COT opportunity (at the beginning of the FFP period). However, unlike the example shown in Fig. 11, the UE will wait for a response from the gNB after sending an uplink (UL) transmission to this gNB, where the response from the gNB may acknowledge or reject the initiation of the COT interval by the UE. In this example, the UE receives an ACK from the gNB acknowledging the initiation of the COT interval by the UE (in time domain 1204). Thus, this UE becomes the owner of the COT interval in question and performs uplink (UL) transmissions in this COT interval.

In another embodiment, when the gNB acknowledges a periodic COT interval initiated by the UE, the gNB may assign multiple periodic COT intervals to a particular UE. In such a case, the UE may not be required to start a countdown period after successfully completing the LBT mode, so that the equipment may start transmitting uplink (UL) traffic using the pre-assigned resources immediately after the start of the COT interval. Fig. 13 illustrates an example for this case. Fig. 13 shows a timing diagram 1300 of one embodiment of synchronizing the operations of the UE, allocating the periodic COT intervals assigned by the gNB. The UE starts an additional countdown procedure, as discussed above, and initiates a COT interval 1304 after successfully completing this additional countdown procedure. The gNB acknowledges the initiation of COT 1304 by the UE and assigns periodic COTs 1306, 1308, and 1310 to the UE (in time domain 1302). The UE receives the ACK from the gNB and transmits UL transmissions in COT 1304. After the ownership period of COT 1304 expires, the UE may initiate periodic COTs 1306, 1308, and 1310 according to commands from the gNB. For these COTs 1306, 1308, and 1310, the UE may only need to perform a CCA assessment before each of the COTs. If the CCA assessment before any COT is successful, the UE transmits in this COT without the need for an additional countdown procedure.

In some embodiments, a third type of periodic COT interval is proposed. For the third type of periodic COT interval, both the UEs and the gNB may initiate such COT intervals. In one embodiment, a free period and a CCA evaluation period may be mandatory before the COT interval, as specified by the regulations and presented above. The gNB may have a higher priority for initiating a COT interval and may initiate a COT interval immediately after the CCA evaluation period if the channel is free. The UEs may have a lower priority for initiating a COT interval and therefore may continue with a countdown procedure during which a number in a counter initiated by a random number is decreased for each control interval when the communication channel is free. To ensure that there is no collision between the gNB transmissions and the UE transmissions, a contention window (CW) for the UE may be configured, which may have a minimum value greater than zero. The third type of periodic COT intervals may be initiated within a certain period of time (e.g., a T_UE_COT interval) and may be configured in advance by the gNB such that the UE or subset of such UEs that can initiate a periodic COT interval knows the value of this period in advance.

Fig. 14 is a timing diagram 1400 illustrating one embodiment of synchronizing operations of a gNB and a UE, and highlighting the initiation of COT intervals by both the gNB and the UE. Fig. 14 illustrates one embodiment for initiating a third type of COT interval, where the gNB has a higher priority than the UE for initiating a COT interval. In this example, both the UE and the gNB compete for the right to initiate a COT interval periodically within a time interval T_UE_COT. Both the UE and the gNB may perform a CCA evaluation (in time domain 1402) before the COT interval 1404. When the CCA evaluation by the UE is successful, the UE may perform a countdown procedure similar to the additional countdown procedure discussed above. If the countdown procedure performed by the UE is not successful, i.e. it turns out that the communication channel is occupied in one of the monitored slots and the number in the randomly initiated countdown counter has not reached zero, the gNB may initiate a COT interval 1404 (e.g. by performing a transmission in the downlink (DL) link) and becomes the owner of this COT interval 1404. In this case, this COT interval 1404 is a COT interval initiated by the gNB. Before the next COT interval 1412, both the UE and the gNB perform a CCA assessment (in the time domain 1406). The UE may perform a successful CCA assessment and countdown procedure (1408), and then transmit on the uplink (UL) to the gNB to initiate COT 1412. When the UE receives an ACK from the gNB acknowledging the initiation of COT 1412 by the UE (1410), the UE becomes the owner of COT 1412, and this COT 1412 is a COT interval initiated by the UE. If the gNB rejects the initiation of COT 1412 by the UE, the gNB may own this COT 1412.

In one embodiment, the gNB may allow the UE to have a zero countdown duration before the start of the COT interval. The gNB may acknowledge the UE's transmission and the COT interval, for example, using a HARQ-ACK message to the UE, or may cancel the transmission of the COT interval to the UE using a HARQ-NACK message and assume ownership of the COT interval.

In some embodiments, for all UE-initiated COT intervals, the gNB may "take away" any periodic COT interval, cancel any periodic COT interval, or modify any periodic COT interval from the set of UE-initiated intervals to make that interval a gNB-initiated COT interval. The gNB may also modify the period and duration of a COT interval, such as through control signaling to the UEs. To achieve this, the gNB may request interruptions or cancellations or modifications of a COT interval in various ways, such as by adding a field to the HARQ ACK-NACK message or by adding a field to the DCI information. A request by the gNB to interrupt, cancel, or modify a COT interval may also be made in a slower manner using a MAC CE element or an RRC control message.

In some embodiments, the gNB may specify, for the UEs, a subset (e.g., a scheme) of time intervals or a scheme of capabilities available to the UEs to initiate or start a COT interval. For example, the UE may only be allowed to initiate a COT interval in odd/even periods (FFP), in uplink (UL)/downlink (DL) transmission periods, or in uplink (UL) transmission periods. The possible time intervals for initiating a COT interval or a periodic COT interval may be provided by the base station, configured by higher layers, or predefined. These capabilities may be assigned to the UEs based on the category of the corresponding UE or the capabilities of such UE, for example. A gNB may, by assigning capability allocation schemes within a T_UE_COT interval, allow multiple UEs to share (i.e. initiate/start) COT intervals within the duration of the same T_UE_COT interval.

In some embodiments, the configuration of a COT interval or a periodic COT interval, which may also be referred to herein as an FFP period configuration, for the UEs may be performed and signaled to the UEs by the gNB, or may be preconfigured in the UE and reconfigurable. The FFP period configuration for a COT interval initiated by the UE may be different from or the same as the FFP period configuration for a COT interval initiated by the gNB. As an example, the gNB communicates with a group of UEs configured by the gNB to initiate COT intervals. The UE may first monitor the communication channel based on the CCA assessment, and after the CCA assessment is successful, the UE may transmit in the uplink (UL) to the gNB to initiate the COT interval based on the uplink transmission configurations and the COT interval from the gNB. The gNB, upon receiving the corresponding uplink transmission from the UE, may determine that the COT in question is a UE-initiated COT and determine the resulting/subsequent actions to be taken based on the detected UE-initiated COT and its own status. The actions to be taken by the gNB may comprise an acknowledgement of the UE-initiated COT, or an indication to the UE to share the gNB-initiated COT, or an indication to the UE to share a COT initiated by another UE. The corresponding indication from the gNB may be transmitted as part of the downlink control information (DCI) on the PDCCH. This indication may contain information about the COT interval (also referred to as COT interval information, COT interval parameters, or COT interval parameters for the FFP period), such as the periodicity for the FFP period (which is also the period/periodicity of the COT interval opportunity), the MCOT interval within this FFP period, the time offset of the FFP period, the minimum duration of the idle period within the FFP period, the maximum duration of the idle period within the FFP period, the communication channel, the frequency bandwidth, or a combination of these parameters. The FFP period is the length (or duration in time or period) of a fixed frame period, the MCOT interval is the maximum allowed duration of the COT interval within the period (FFP), the minimum duration of the idle period and the maximum duration of the idle period are the respective minimum and maximum time durations of the idle period (no transmissions) within this FFP period, and the communication channel and the frequency bandwidth represent the frequency resources used for transmissions in the COT interval. The configuration of the COT interval or the periodic COT interval, which may be initiated by the UE or the gNB, may contain the COT interval parameters as described above. The UE may receive the COT interval configuration from the gNB.

In some embodiments, after a successful CCA assessment, the UE may transmit a channel or signal (called an uplink transmission) on the uplink to initiate a COT interval. The uplink transmission from the UE may comprise a PUSCH based on a configured grant (CG). Alternatively, the uplink transmission may be a PUCCH based on a radio resource control (RRC) configuration from the gNB and CSI (channel state information) such as a CQI, a rank indicator (RI), a precoding matrix indicator (PMI), etc. In one example, the uplink transmission comprises a PUCCH (with a HARQ request) or an SR (Scheduling Request) sent on the PUCCH, or both. In another example, the uplink transmission may be a physical random access channel (PRACH) preamble sent by the UE. The PRACH capability (in terms of time and frequency resource) and the preamble sequence of this PRACH can be configured by the gNB. In yet another example, the uplink transmission can be an SRS (Sounding Reference Signal) signal transmitted to the gNB using the SRS resource (in terms of time and frequency resource, comb spectrum position, sequence, etc.) configured by the gNB.

In some embodiments, after a successful CCA assessment, the UE may transmit a COT grant request to the gNB on the uplink, requiring the UE to initiate a COT. This COT grant request may be transmitted using a PUCCH resource or a PDSCH resource based on a CG grant. The COT grant request may contain one or more of the following types of information: an SR (Scheduling Request), a BSR (Buffer Status Report) to the UE, or CSI information.

The gNB detects possible uplink transmissions from the UE that initiates a COT interval or requests initiation of a COT interval over the channel(s) and using the signal(s) configured for the UE to initiate a COT interval. When the gNB transmits, for example, in a COT interval initiated by this gNB, it may be unable to detect the uplink transmission. In addition, the gNB may fail to detect the uplink transmissions due to interference, low signal level, etc. Therefore, the uplink transmission from the UE to initiate or request a COT interval may be missed by the gNB. In addition, multiple UEs may transmit uplink transmissions to initiate or request a COT interval at roughly the same time. Therefore, several situations may occur. In one case, the UE is the only entity initiating or requesting a COT at a given time, and therefore there is no collision/overlap. In another case, both the UE and the gNB initiate a COT, and the gNB missed an uplink transmission from the UE, and therefore is not aware that the UE is initiating or requesting a COT. In yet another case, the gNB also initiates a COT (after a successful CCA assessment), and the gNB has detected an uplink transmission from the UE, and therefore is aware that the UE is initiating or requesting a COT. In yet another case, another UE (or more UEs) may also initiate or request a COT, and the gNB receives COT initiations or requests from multiple UEs.

After the UE sends an uplink transmission that initiates or requests permission to initiate a COT interval, it may wait for a response from the gNB. One reason for the UE to wait for a response from the gNB is to resolve the conflict and overlap between the COT intervals initiated by the gNB and the UE, or between the COT intervals initiated by multiple UEs. The UE may not be aware of such a conflict or overlap and may take some time to realize it. Therefore, the gNB may act as an arbitrator to resolve the conflict and transmit a response to the UE indicating information about the COT interval for use by the UE. As one example, the response from the gNB may contain information indicating that the gNB confirms (or authenticates, or acknowledges) the COT interval initiated or requested by the UE. As another example, the gNB may not authenticate or reject the COT interval initiated by the UE. As yet another example, the gNB may inform the UE that a COT interval initiated by the gNB may be used or shared. As yet another example, the gNB may inform the UE that a COT interval initiated or requested by another UE may be used or shared. As yet another example, the gNB may determine and initiate a COT interval and transmit information related thereto to the UE so that the UE shares this COT interval. In response thereto, the gNB may acknowledge or reject the COT interval initiated by the UE or the request for permission to initiate a COT interval sent by the UE, or indicate the type of COT interval that the UE in question may use, where the indicated COT interval may be initiated by the UE, another UE, or the gNB.

The response from the gNB or the indication of the type of COT interval to be used by the UE may be conveyed implicitly. In other words, the gNB may indicate its response to the UE implicitly. For example, after the UE sends an uplink transmission to initiate or request a COT interval, the UE may receive a downlink transmission from the gNB. If any downlink transmission for the UE in question is received from the gNB within a certain time window, the UE may consider that the COT interval it requested or initiated has been granted and may continue its uplink transmission, for example, using this COT interval based on the parameters configured for the COT interval initiated by the UE, such as the period (or the FFP period associated with this COT interval), the duration of the COT interval, the idle time (idle state) and the offset of the FFP period relative to the frame number. Although such implicit acknowledgement by the gNB may work in a relatively simple situation without considering COT conflicts, there may be ambiguity, for example when the gNB uses a different COT to transmit downlink transmissions to the UE.

In some embodiments, the gNB response or indication of the COT interval to use may be communicated explicitly. For example, after the UE performs an uplink transmission to initiate or request a COT interval, the UE may receive downlink control information (DCI). The gNB may transmit the COT interval information as part of the DCI. The COT interval information may comprise a COT interval configuration index that identifies a COT interval configuration. A number of COT interval configurations (where each COT interval configuration comprises a period (e.g., an FFP period) associated with this COT interval, a duration of the COT interval, an idle time (free time) in the period, and/or an offset of the period relative to the frame number) may be configured for the UE, for example, through RRC control, and each COT interval configuration may be assigned an index value. Each COT interval configuration defines a COT interval and corresponds to this COT interval. By transmitting a COT interval configuration index to a UE, the UE is informed of the corresponding COT interval to use. In one embodiment, the COT interval information transmitted in the DCI information may comprise a set of parameters (e.g., COT interval parameters) required for the UE to correctly use or share the COT interval, and the set of parameters comprises a period associated with the COT interval, a duration of the COT interval, an idle time (free time) in the period, and an offset of the period relative to the frame number. The DCI information for transmitting the COT interval information to a UE may be specific to this UE. Alternatively, group-wide DCI information may be used to transmit the COT interval information to a group of UEs. The COT interval information may also be transmitted in a medium access control element (MAC CE). After the UE receives the response from the gNB and obtains the COT interval information to use or share, the UE shall perform uplink transmission within the COT interval according to the COT interval information or parameters reported to the UE.

In one embodiment, the gNB may indicate to the UE that there are no COT intervals to use. As one example, after performing an uplink transmission to the gNB to initiate or request a COT interval, when the UE does not receive, within a certain time window, any acknowledgement/acknowledgment (ACK) message from the gNB to indicate a COT interval to use, the UE may consider that initiation of the COT interval failed or that the requested COT interval is rejected. In such a case, the UE may accept downlink transmissions to share the COT interval indicated by the gNB, or the UE may perform a CCA assessment to initiate or request a COT interval again.

In one embodiment, after performing an uplink transmission to the gNB to initiate or request a COT interval, when the UE has not received, within a certain time window, any acknowledgement/acknowledgment (ACK) message from the gNB to indicate a COT interval to use, and no other downlink transmission is detected, the UE may consider that the initiation or request of the COT interval is granted. The UE in question may then perform transmissions in the initiated or requested COT interval.

Fig. 15 shows a flow chart of one embodiment 1500 of the UE operations for requesting a new COT interval for the UE for the FFP period. The UE transmits a request on the uplink (UL) to the gNB that requires a new UE-initiated COT interval for the FFP period (step 1502). The requested new COT interval for the UE may have parameters different from the parameters of the COT interval used by the UE up to now. The UE then starts a timer to wait for a response from the gNB to the transmitted request on the uplink (step 1504). If the UE determines that there is no response from the gNB (step 1506) and that the timer has not expired (step 1508), the UE returns to step 1506 to continue monitoring for a response from the gNB. If the timer expires and the UE does not receive a response from the gNB (step 1508), the UE does not change the COT interval for the FFP period used by the UE (step 1510). If the UE receives a response from the gNB (step 1506), the UE determines whether the response means that the request is accepted by the gNB (step 1512). If the request is not accepted by the gNB (rejected), the UE proceeds to step 1510. If the request is accepted by the gNB, the UE may transmit in a new COT interval for the UE. The response may indicate parameters of the requested new COT interval, such as the position of the FFP period, the duration of the COT interval within this FFP period, a free period within this FFP period, etc., as discussed above. The UE may wait for the offset time for the FFP period as indicated in the response, perform a CCA evaluation before that FFP period, and initiate a COT interval after a successful CCA evaluation.

The UE may transmit a request in the uplink (UL) requesting permission to initiate a COT within an FFP in various ways. In one embodiment, the UE may transmit the request while sharing a COT initiated by the gNB. In other words, the request is transmitted using a COT initiated by the gNB. In another embodiment, the UE may transmit the request while in its own initiated COT shared with the gNB. In other words, the request is transmitted using a UE-initiated COT shared with the gNB. In yet another embodiment, the UE may transmit the request while in its own initiated COT for an FFP, and the UE wants to change the parameters of the current FFP for a different FFP. In other words, the UE transmits a request in a UE-initiated COT interval within the current FFP period, and the UE requests a new FFP period and/or a new COT interval within the new FFP period. In this request, the UE may provide the gNB with parameters for a new COT interval in the new FFP period, including but not limited to the periodicity, the link or link bandwidth, the maximum free period duration, the MCOT interval, and the offset for starting the new FFP period. The gNB may accept the request and the parameters specified in this request, or may replace the requested parameters with a new set of parameters, for example, the gNB may propose a different periodicity, or different frequency resources (link) or a different offset for starting the new FFP period. The gNB may also reject the request. If the request is rejected, the UE cannot start a new COT interval for the new FFP period with the requested parameters. If the UE has already been configured with a COT interval for a certain FFP period, it may only be able to initiate COT intervals based on the existing configuration, or may share a COT interval initiated by the gNB for a certain FFP period, or may only initiate or share a dynamic COT interval. If the request has been accepted by the gNB, the UE may start initiating COT intervals after the offset time has expired. Acceptance or rejection by the gNB may be done in various ways, such as by adding a field for the acknowledgement/negative acknowledgement (ACK-NACK) message for the HARQ mode or by adding a field to the DCI information. Acceptance or rejection may also be done in a slower way via the MAC CE element or an RRC control message. In some embodiments, acceptance (or rejection) may be implied by the UE if the gNB has not rejected (accepted) the request.

Embodiments of the present invention may allow for the use of alternative periods with dynamic COT intervals and with semi-static COT intervals (with FFP periods) on both the gNB side and the UE side. The gNB may configure such time periods where dynamic or semi-static access to the communication channel is allowed.

For channel access in semi-static channel occupancy, as defined in TS 37.213, the gNB provides the UE with higher layer ChannelAccessMode-r16 = 'semistatic' parameters via SIB1, or dedicated higher layer configuration parameters proposed in SemiStaticChannelAccessConfig, where the channel access parameters such as the periodicity in semi-static channel access mode are specified. In frame-based operation (FBE) mode in unlicensed/shared spectrum, the device may transmit in each fixed frame period (FFP) during the maximum busy time (MCOT). The MCOT interval may be up to 95% of the FFP period. The durations of the FFP period, MCOT interval and idle period in each FFP period are parameters (or configuration) characterizing the gNB or COT interval initiated by the UE in each FFP period.

Similarly, the associated parameters required for a UE-initiated COT interval in an FFP period shall be provided to the UE by the gNB. Parameters such as the periodicity for the FFP period, the MCOT interval, the time offset (e.g. relative to every frame or frame number zero) for the UE FFP periods (COT interval capabilities) may be different from the corresponding parameters for a gNB-initiated COT interval for the FFP period. The high-layer parameters as defined in TS 37.213 for providing channel access parameters may be extended to provide parameters relative to UE-initiated COT intervals. As an example, the higher-layer parameters may be extended as shown in Fig. 16. Fig. 16 shows one embodiment of a configuration information element (IE) 1600 for semi-static channel access that may be used for embodiments of the present invention. As shown, the semi-static bearer access configuration IE 1600 contains parameters for the UE-initiated COT interval, such as an offset, a period, an MCOT interval, etc. The set of values for the period, offset, and MCOT interval for the UE-initiated COT interval may be the same as the set of values for the gNB-initiated COT interval, and the value provided for the UE-initiated COT interval may be the same or different from the value configured for the gNB-initiated COT interval. The COT interval period or the COT interval capability may also be referred to as the periodicity for the FFP period associated with this COT interval. The gNB-initiated COT interval period may be selected from the set of values: {1, 2, 2.5, 4, 5, 10} (in ms). The gNB-initiated COT interval offset may be selected from the following set of values: {1, 2, 2.5, 4, 5, 10} (in ms). The MCOT interval for the gNB-initiated COT interval may be selected from the following set of values: {80, 85, 90, 95} (in %). The UE-initiated COT interval period may be selected from the following set of values: {1, 2, 2.5, 4, 5, 10} (in ms). The UE-initiated COT interval offset may be selected from the following set of values: {1, 2, 2.5, 4, 5, 10} (in ms). The MCOT interval for the COT interval initiated by the UE may be selected from the following set of values: {80, 85, 90, 95} (in %). In one embodiment, the value provided by the UE may be configured from the value configured for the COT interval initiated by the gNB, and may take any value from the set of values, whether it is the same value or a value different from the value configured for the COT interval initiated by the gNB. In another embodiment, for the period under consideration, the value offered to the UE may be dependent on the value configured for the COT interval initiated by the gNB, where only a subset of the values may be provided to the UE, for example, values that are multiples of each other. As an example of this option, if the COT interval configured by the gNB has a period of 2 ms, then the UE may be granted a period of 1, 2, 4, or 10, but not 2.5 or 5. The capability information may indicate the capability of the UE to initiate COT intervals, including the capability of the period of the COT interval initiated by the UE to have any value from the set of values: {1, 2, 2.5, 4, 5, 10} (in ms), regardless of the value configured for the period of the COT interval initiated by the gNB.

The UE may be provided with one or more such configurations. When the UE receives a command to switch from the current COT to the new COT, it may stop using the configuration of the current COT and start using the configuration of the new COT. For example, it stops sharing the current COT and starts sharing the new COT. The dynamic indication of the new COT may require the gNB to provide the UE with an amount of the remaining duration of the new COT. Based on the indication of the new COT parameters from the gNB, the UE may be configured to take into account and respect the new quiet periods associated with the new COT parameters. The remaining COT duration for the new COT may be signaled, for example, in the DCI Format 2_0 information specified in TS 38.212.

In some variants, the DCI format 2_0 information may be extended to signal a switch of the FFP period configuration parameters (or the COT interval configuration) or an indication of the FFP period configuration parameters via the SemiStaticAccessConfig-ID. This DCI format 2_0 information may be extended to indicate the target FFP period (e.g., by indicating the FFP period configuration or the target FFP period configuration parameters or the target COT interval (UE-initiated COT interval or gNB-initiated COT interval)) to the UE that the UE should switch to the target FFP period configuration or to use the target COT interval (UE-initiated COT interval or gNB-initiated FFP period). The UE may use or switch to use the indicated target COT interval and start sharing after the N_COT_switch (transition time) slots. Until this point, transmissions from the UE are considered to occur in the UE's current COT. Before the transition time expires, the UE transmits in its own current COT. After the transition time expires, the UE starts using the target COT. If the target COT expires before the N_COT_switch, the UE may not switch to the target COT and may terminate the current COT for the FFP. If the FFP configuration for the FFP in question matches one of the UE's possible configurations (e.g., based on the SemiStaticChannelAccessConfig_UE_List), the UE may initiate a new COT with new COT parameters. These new COT parameters are the target COT parameters. If the parameters of the target COT interval belong to the SemiStaticChannelAccessConfig_gNB_List list, the UE may monitor the gNB to detect a COT interval initiated by the gNB and may share this COT interval.

Fig. 17 shows a flow chart 1700 of one embodiment of operations of the UE and the gNB for switching a COT interval for the UE. In this example, the gNB may instruct the UE to switch transmissions from using the current COT interval to using the target COT interval. The gNB may initiate the COT interval switch via a command in the DCI (block 1702). Upon receiving the command, the UE may start a transition timer (TT) to transition from the current COT interval to the target COT interval (block 1704). The UE may determine whether the TT timer expires faster than the duration of the target COT interval (block 1706). For example, the UE may determine whether the TT timer expires before the end of the target COT interval. If the UE determines that the TT timer will expire before the end of the target COT interval, the UE switches to the target COT interval after the TT timer expires (step 1708). The UE may switch to using the COT interval parameters corresponding to the target COT interval. If the UE determines that the TT timer will expire after the end of the target COT interval, the UE may continue to use the current COT interval for transmissions until the current COT interval expires (step 1710), after which the UE switches to the target COT interval (step 1708). The UE may determine whether the target COT interval is a UE-initiated COT interval (step 1712). If the target COT interval is a UE-initiated COT interval, the UE may initiate a COT interval at the next opportunity (step 1714). The initiated COT interval has the parameters of the target COT interval. If the target COT interval is not a UE-initiated COT interval, the UE may monitor the gNB-initiated COT interval for sharing (step 1716).

The gNB may provide the UE with the gNB-initiated COT interval configuration for the FFP period and/or the UE-initiated COT interval configuration for the FFP period. These configurations may be different.

In accordance with the spectrum regulations requirements of ETSI EN 301 893 V2.1.1 (2017-05), a UE-initiated COT interval for an FFP period is triggered by a burst of uplink (UL) transmissions from the UE at the start of the UE's FFP period. This transmission follows channel monitoring for a monitoring period of at least 9 ms, during which the channel must be idle.

When a gNB-initiated COT interval for an FFP period and a UE-initiated COT interval for an FFP period overlap in time, their FFP periods and idle periods may not be aligned, as shown in Fig. 18. Fig. 18 shows a timing diagram 1800 showing gNB-initiated COT intervals 1810 and UE-initiated COT intervals 1820 that are not aligned with each other. These devices, the UE and the gNB, must take into account the transmission periods and idle periods associated with their own COT intervals. In other words, each of the devices, both the gNB and the UE, uses specific sets of parameters (e.g., periodicity for the FFP period, idle period duration, FFP period offset) associated with their own COT intervals. At the same time, the gNB and the UE may share the same COT interval (as specified in TS 37.213). The concept of sharing a COT interval needs to be reconsidered and clearly defined. If the UE transmits during a UE-initiated COT interval and the gNB transmits during a gNB-initiated COT interval, and these two COT intervals overlap in time, as shown in FIG. 18, questions may arise as to whether these two COT intervals can be shared between the gNB and the UE. In some embodiments, to clarify these situations, two devices may share a COT interval for an FFP period when they use the same set of COT interval parameters for the FFP period for their transmissions. In other words, two devices share one COT interval for an FFP period if they use the same set of COT interval parameters for the FFP period for their transmissions.

In some embodiments, when a UE transmits during a COT interval for an FFP that overlaps another COT interval, the gNB must uniquely identify to which COT interval the UE transmission belongs. The gNB must determine whether the COT interval used by the UE for transmission from the UE belongs to a COT interval initiated by the UE or to a COT interval initiated by the gNB. In one embodiment, the gNB may decode a burst of transmissions from the UE that started at the start of the FFP opportunity for the UE and interpret this as an initialization of the COT interval for the UE. In other words, when the gNB receives a burst of transmissions from the UE that started at the start of the FFP opportunity for the UE, the gNB may determine that the UE initiated the COT interval. However, it is not possible to determine unambiguously whether the UE has initiated its own COT interval or whether the UE is simply sharing a COT interval belonging to the gNB based on a simple transmission from the UE. To resolve this dilemma, the UE may explicitly signal to the gNB that it has initiated its own COT interval. For example, an uplink (UL) transmission from the UE may have an additional field identifying or indicating a UE-initiated COT interval or a gNB-initiated COT interval. Such signaling may help the gNB determine that the UE transmission belongs to the UE-initiated COT interval for the FFP period, but cannot clearly indicate the COT interval for subsequent UE transmissions during overlapping COT intervals.

The proposed solution to these problems, in one variant, requires that transmissions from the UE belong to the same (single) COT interval until that COT interval ends, unless the gNB instructs otherwise. This requires that when the UE initiates a COT interval for an FFP period, the UE continues to transmit in the same COT interval, in other words, the UE cannot switch back and forth between its own initiated COT interval and the gNB-initiated COT interval. However, the gNB may instruct the UE to switch to a different COT interval if necessary. For example, the UE may decide to initiate its own COT interval, during which the gNB instructs the UE to switch to the gNB-initiated COT interval and share that COT interval. In this way, the gNB can dynamically instruct the UE which set of COT interval parameters it should use. The COT interval configuration can be changed via dynamic control information, such as DCI information, or via RRC control configuration. The set of UE-initiated COT interval parameters for the FFP period can be dynamically configured by the gNB. Uplink scheduling grants can specify resources and capabilities for the UE to initiate a COT interval for the FFP period. For Internet of Things (IoT) applications, uplink transmissions can be started in response to an external event causing the UE to initiate a COT interval at the earliest opportunity.

Fig. 19 shows a logic diagram of one embodiment 1900 of the operations of the UE and the gNB for accessing a communication channel, highlighting the dynamic change of COT intervals. The gNB may configure parameters for a UE-initiated COT interval and a COT interval initiated by this gNB (step 1902). This gNB may also assign uplink (UL) grants, such as resources, for a particular traffic type and a particular COT interval (step 1904). The UE may initiate a COT interval for an FFP period via an uplink (UL) transmission burst (step 1906). This UL transmission burst may start at the start of the FFP period associated with the considered COT interval, which indicates that the UE initiates this COT interval. The gNB determines that the UE has initiated a COT interval (step 1908), for example, based on an uplink (UL) transmission burst received by the gNB. The UE may determine whether the gNB has dynamically instructed the UE to move to a new COT interval (step 1910). If the gNB has not instructed the UE to move to a new COT interval, the UE may continue to use the COT interval it initiated (step 1912). If the gNB has instructed the UE to move to a new COT interval, the gNB may provide a value of the remaining duration of the new COT interval and initiate a COT switch (step 1914). The gNB may perform the instruction and initiate the COT switch by transmitting DCI information to the UE. The DCI information may contain information about the remaining duration of the new COT interval. The UE may start using the new COT interval (step 1916).

In some embodiments, after the UE initiates its own COT interval, the UE may start a timer and wait for the UE-initiated COT interval to be validated by the gNB. The validation procedure may be any DL transmission that does not require the UE to switch to a different set of COT interval parameters (i.e., to a different COT interval). If such a switch command is received by the UE before the timer expires, the UE may switch to a different COT interval using a different set of COT interval parameters. If such a switch command is not received by the UE before the timer expires, and no other DL transmission is received by the UE before the timer expires, the UE may automatically return to sharing the gNB-initiated COT intervals.

For a UE indicating support for a UE-initiated COT interval in the FBE mode of operation, for example, when indicating capabilities, the gNB may indicate, when scheduling an uplink grant, whether the UL transmissions from the UE should be performed using the gNB FFP period configuration in the gNB-initiated COT interval or using the UE FFP period configuration in the UE-initiated COT interval. Such an indication may be made using a DCI information field, for example, and the presence of such a DCI information field indicates the type of FFP period for scheduling the UL transmissions. This field may always be present during FBE operation when the gNB schedules UL transmissions from the UE. Such an indication is to avoid the need for additional rules for dealing with situations where such a field is missing. An example of such a situation is the case where a gNB-initiated COT interval and a UE-initiated COT interval overlap. The presence of a DCI information field indicating the type of uplink (UL) transmissions in the COT interval shall allow the gNB to respond with a small delay to some events in the Industrial Internet of Things and Ultra-Reliable Low Latency Communications (IIoT/URLLC) operation. In one embodiment, it may be specified, for example in the standard, that a field in the DCI information that specifies whether the planned UL transmission is based on a UE-initiated COT interval or on a shared gNB-initiated COT interval cannot be absent when operating in the FBE mode.

A COT interval initiated by the UE begins with an uplink (UL) transmission as required by the ETSI standard. An example of such an UL transmission that can initiate a COT interval may be a periodic/semi-persistent transmission with a configured grant. However, there are situations where a non-periodic/persistent transmission may be needed. As an example, a gNB may need to schedule the UE to transmit an aperiodic SRS or an aperiodic CSI-RS report. If this happens at the end of a COT interval, the gNB may need to wait for the next COT interval and then transmit the DCI information with the scheduled grant. Thus, additional delay will be added. However, if the gNB can schedule, at the end of a COT interval, an uplink (UL) grant after the start of the next COT interval, the response time can be significantly reduced.

In another example, the UE may transmit a request, such as a scheduling request (SR), near the end of a COT interval. If the gNB can transmit DCI information with assignment over COT intervals, the delay of uplink (UL) transmissions can be reduced.

In another example, scheduling an aperiodic transmission using DCI information with an indication that the aperiodic transmission is to be performed in a UE-initiated COT (FFP) interval for the next FFP period for the UE may be used for a one-time UE-initiated COT interval for non-periodic low-latency applications.

There are various ways to specify the scheduled uplink (UL) transmission time, for example:

Have a scheduled transmission time via DCI information greater than the current COT interval

Have an indication via DCI information of the FFP period index (0 means the current period) and the uplink (UL) transmission time in this FFP period (shorter than the COT interval duration)

When the scheduled time of the uplink (UL) transmission is later than the end time of the COT interval in the current FFP period, as shown in Fig. 26, the UE equipment may determine the FFP period (in which the considered uplink (UL) transmission is to be performed) by calculating the difference between the scheduled time and the end time of the COT interval in the current FFP period and dividing this difference by the duration of the FFP period. Fig. 26 shows a diagram 2600 of one embodiment of the operations of the gNB and the UE equipment. The gNB node transmits DCI information 2602 at the end of the COT interval in the current FFP period 2604 to schedule the uplink UL transmission 2606.

It may happen that the gNB or the UE cannot initiate the next FFP period due to a failure of the LBT mode. In such a case, the corresponding device (the gNB or the UE) needs to wait for another FFP period before trying to initiate a new COT interval. If an uplink transmission is scheduled for the FFP period where the failure occurred, the UE needs to defer the scheduled transmission to the next FFP period. Therefore, when an uplink transmission is scheduled for a future FFP period (either an FFP period for the gNB or an FFP period for the UE), and this FFP period (the COT interval in this FFP period) cannot be initiated, the uplink transmission is deferred to the next FFP period that can be initiated (e.g. by the gNB or the UE). Examples of such transmissions may include a CSI-RS report, an SRS signal, data, etc.

One additional issue that needs to be addressed is what type of FFP period configuration should be used for deferred transmission.

If the DCI scheduling information indicates that the UL transmission scheduled after the end of the current COT interval is to be performed in a gNB-initiated COT interval or in a UE-initiated COT interval, the UE may wait for the corresponding gNB-initiated COT interval or the UE-initiated COT interval for transmission. In other words, if the COT interval initiation fails, the UE will wait until the corresponding (necessary) COT interval is initiated. To calculate the time or slot index for the UL transmission, the UE may stop the slot counter when the COT interval (where the DCI scheduling information is located) ends and continue to increment the slot counter when the corresponding initiated COT interval starts.

In one embodiment, a default timer may be considered that starts counting when DCI information for cross-scheduling of COT intervals is received. If the timer expires before a COT interval (indicated in the DCI scheduling information) can be initiated, the UE may cancel its transmission and request new resources.

Scheduling within the next FFP period may depend on the type of uplink (UL) transmission, such as data, SRS signaling, or CSI information. In addition, data deferral may also depend on the type of transmission and/or its priority. For example, any transmission may be allowed within the next FFP period, but further deferral may only be allowed for A-SRS or A-CSI reports.

Industrial Internet of Things (IIoT) and ultra-reliable URLLC applications involve transmissions triggered by periodic events such as measurements and reports, as well as transmissions triggered by unscheduled events such as alarms. To handle unexpected/unscheduled situations and schedule some transmissions with higher priority than already scheduled periodic/semi-persistent transmissions, the gNB should be able to cancel pending transmissions, including uplink (UL) transmissions that may trigger a COT interval. A possible solution uses CG Type 2 PUSCH activation/deactivation. Other cancellation modes may also be considered.

The gNB may cancel uplink (UL) transmissions deferred in a future FFP period, including canceling future COT intervals initiated by the UE in future FFP periods, such as by canceling an uplink (UL) transmission initiating any COT interval.

Examples of cancellation signaling may include transmission of DCI information (e.g., in DCI 2_0 format), RRC control, MAC CE element, or cancellation may be implemented via timer expiration. Another way to cancel a future COT interval initiated by the UE may be that the gNB changes the symbol configuration from UL symbols to DL symbols.

In order to communicate with multiple UEs that independently initiate overlapping COT intervals, the gNB may request the UEs to switch to a different FFP configuration. For example, the gNB may signal the UEs that they should switch to the gNB FFP configuration and the gNB-initiated COT interval, which may cause the UEs to synchronize. The gNB may indicate to the UEs that they should switch between FFP configurations, such as from a UE FFP to a gNB FFP, during the current UE-initiated FFP or at future FFP boundaries. Examples of signaling for such switching may be DCI information, RRC control messages, MAC CE element associated with certain switch deadline timer expiration events.

In one embodiment, in the event of a link failure, the UE may switch to the FFP period configuration for the gNB node, i.e. wait for a COT interval initiated by the gNB node. In another embodiment, in the event of a link failure, the UE may be configured to initiate a COT interval within the FFP period for the UE equipment and an uplink (UL) broadcast (e.g., an alarm or beacon signal). In this solution, a UE that has lost a connection can restore communication much faster if it is surrounded by several receivers (such as gNB nodes).

In another embodiment, a default FFP period may be configured by the gNB. If a link failure occurs, the UE switches to the default FFP period configuration. In another embodiment, the UE may fall back from the FFP period configuration to the default configuration after a number of FFP failures due to LBT failures, i.e., persistent LBT failures, which may be different from a link failure.

In addition, the UL transmission scheduling grants for different traffic types may specify the corresponding sets of FFP period parameters for the COT interval to use. With this approach, different UL traffic types may be configured to be transmitted in different COT intervals. For example, transmissions of some emergency messages or messages requiring low latency may be allowed in the UE-initiated COT interval, while other UL traffic may be allowed only in the gNB-initiated COT interval. In this way, transmission of different traffic types may be allowed only for special types of COT interval initialization.

In some embodiments, if the UE determines that the communication channel between the UE and the gNB is lost, it may revert or "fall back" to the gNB-initiated COT interval for the FFP period and transmit using the parameters of that gNB-initiated COT interval.

Fig. 20 shows a logic flow chart 2000 of one embodiment of the operations of the UE and the gNB for accessing a communication channel, allocating an acknowledgement of the initiation of a COT interval for the UE. The gNB may configure parameters for the UE-initiated COT interval and the gNB-initiated COT interval (step 2002). The gNB may also assign uplink (UL) grants, such as resources, for a particular traffic type and a particular COT interval (step 2004). The UE may initiate a COT interval for an FFP period via a burst of uplink (UL) transmissions and start a timer for verification by the gNB (step 2006). The UE may wait for verification of the UE-initiated COT interval from the gNB before the timer expires. The uplink (UL) transmission burst may start at the beginning of the FFP period associated with the COT interval, which means that the UE initiates the COT interval. The UE may determine whether the gNB has authenticated the UE-initiated COT interval (step 2008). If the UE determines that the gNB authenticates the UE-initiated COT interval, the UE may continue to use its initiated COT interval (step 2010). If the UE determines that the gNB does not authenticate the UE-initiated COT interval, the UE determines whether it accepts a command to switch to and share a new COT interval (step 2012). If the UE accepts this command, i.e. the gNB transmits such a command to the UE, which means that the gNB does not authenticate the COT interval initiated by the UE, the gNB may provide information about the remaining duration of the new COT interval to the UE and start switching (step 2014). The UE may start using (sharing) the new COT interval (step 2016). If the UE does not receive this command and the timer for authentication by the gNB expires, the UE may start using the COT interval initiated by the gNB (step 2018).

The corresponding resources for initiating a COT interval for the UE for the FFP period may be configured by, for example, CG Type 2, i.e. configured by an RRC control message, and activated on a PDCCH scrambled with the configured scheduling identifier (CS)-RNTI before using the COT interval for the UE. With this approach, the gNB can directly control whether or not the UE can initiate a COT interval in the next FFP period. The UE may be configured with the necessary resources for initiating a COT interval for the UE for the FFP period by CG Type 2.

A problematic scenario may arise when a single gNB serves multiple UEs that may initiate COTs independently of each other. Such situations are quite similar to the case of Internet of Things (IoT) applications. In such a case, managing UE-initiated COTs may be very complex, since the gNB is not able to predict which UE (e.g., IoT devices) may initiate a COT and when, and multiple COTs initiated by different UEs may overlap in time. One possible technical solution for handling a large number of UEs is to split the entire population of UEs into groups, and (re)configure (e.g., configure COTs) on a group basis via group-wide controls. In one embodiment, dynamic (re)configuration of a UE-initiated COT interval for an FFP period may be supported on a per-UE group basis, such as dynamic (re)configuration of COT interval parameters on a per-group basis.

It is possible for the gNB and the UE to alternate their COT intervals, as shown in Fig. 21, where the gNB and the UE can occupy the entire link to a higher duty cycle than allowed by the regulators (>95%). In other words, although the gNB and the UE observe their own idle periods, they collectively occupy the link by more than 95%. Fig. 21 shows a time diagram of one embodiment of gNB-initiated COT intervals and UE-initiated COT intervals, highlighting non-overlapping gNB and UE COT intervals occupying the link. In one embodiment, this situation can be avoided when the UE and the gNB share the same COT interval for the FFP period. Therefore, the gNB and the UE will observe idle time for the corresponding FFP period and avoid hijacking the link.

Some types of UEs may be capable of or may be allowed to initiate COT intervals, and some types of UEs may be unable to or may not be allowed to initiate COT intervals. For example, a relatively old UE may be unable to initiate a COT interval for an FFP period, while a new UE for URLLC communication may be capable of doing so. In such a case, if the UE can initiate a COT interval by transmitting a RACH, the UE may inform the gNB that it is capable of initiating a COT interval. As an example, the UE may indicate its capability using specific sequences on the PRACH, or via message 3 (MSG3) if the UE has received message 2 (MSG2), which allows the UE to initiate a COT interval for an FFP period. The UE shall support signaling capabilities to inform the gNB that it can initiate COT intervals for an FFP period. This signaling can be transmitted during random access, either over the PUCCH or over the PUSCH.

Embodiments of the present invention provide the following:

A method for a UE to initiate a periodic COT interval that may or may not be acknowledged by a gNB. A method for a group of UEs to compete for the right to initiate an aperiodic COT interval that may be acknowledged by a gNB.

A method for a UE and a gNB to compete for the right to initiate a periodic COT interval. This creates opportunities for flexible implementation of uplink (UL) and downlink (DL) transmissions when the gNB has priority for initiating a periodic COT interval. The UE may wait for a random period of time.

A method for a gNB node to communicate with a UE that has won a contention for ownership of a periodic COT interval, and this UE is the owner of this periodic COT interval for several periods. The term "owner" means that this UE is the only device that can start the COT interval for several periods.

A method for specifying different types of traffic allowed for initiation of specific COT intervals, for example, emergency traffic is allowed in both the UE-initiated COT interval and the gNB-initiated COT intervals, and some types of traffic with relatively low priority may be allowed only in the gNB-initiated COT interval, etc.

Bulk (re)configuration of COT interval parameters for an FFP period. Dynamically changing the COT interval parameters for a UE for an FFP period, which validates or invalidates the current COT interval.

Ability to signal to support UE initiated COT intervals.

The UE falls back to sharing the COT interval initiated by the gNB after the link fails or is not authenticated by the gNB.

Fig. 22 shows a flow chart of one embodiment 2200 of a method for initiating a COT interval for a UE. The method 2200 may show operations of the UE operating in the FBE mode. As shown in the figure, the UE may determine that a communication channel is available in an unlicensed spectrum region (step 2210). The UE may send, on this communication channel, a first transmission to the gNB in a fixed frame period (FFP) associated with the UE to initiate a channel busy time (COT) interval by the UE within this FFP. The first transmission begins at the beginning of this FFP and ends before an idle period occurs within the considered FFP (step 2220).

Fig. 23 shows a flow chart of another embodiment 2300 of a method for initiating a COT interval for a UE. The method 2300 may show operations of a gNB communicating with a UE operating in an FBE mode. The gNB may receive, from the UE over a communication channel operating in an unlicensed spectrum region, a first transmission in a fixed frame period (FFP) (block 2310). This first transmission may begin at the beginning of this FFP period and end before a free period within the considered FFP period. The gNB may determine, upon receiving the first transmission, that the UE initiates a channel busy time (COT) interval within this FFP period (block 2320).

It should be understood that one or more steps of the methods proposed herein can be implemented by corresponding devices or modules. For example, a signal can be transmitted by a transmitting device or a transmitting module. The signal can be received by a receiving device or a receiving module. The signal can be processed by a processor device or a processor module. The other steps may be implemented by a decision device/module, a detection device/module, a device/module for switching a COT interval, an instruction (command) device/module, a device/module for starting a timer, an assignment device/module, a configuration device/module, an alarm device/module, an indicator device/module, a certifying device/module, a device/module for acknowledging/negatively acknowledging/rejecting a COT interval, a device/module for initiating a COT interval, a device/module for monitoring a COT interval, a device/module for sharing a COT interval, and/or a requesting device/module. The corresponding devices/modules may be implemented by hardware, software, or a combination of hardware and software. For example, one or more devices/modules may represent an integrated circuit such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

Embodiments of the present invention may be implemented by computer methods. These embodiments may be implemented by a processor system. Fig. 24 shows a diagram of one embodiment of a processor system 2400 for implementing the methods proposed herein, which may be installed in a host device. As shown in the drawing, the processor system 2400 includes a processor 2404, a memory 2406, and interfaces 2410 - 2414, which may (or may not) be located and connected as shown in Fig. 24. The processor 2404 may be any component or set of components adapted to perform calculations and / or other tasks related to data processing, and the memory 2406 may be any component or set of components adapted to store programs and / or instructions for execution by the processor 2404. In one embodiment, the memory 2406 includes a non-volatile computer-readable storage medium. The interfaces 2410, 2412, 2414 may represent any component or set of components that allow the processor system 2400 to communicate with other devices/components and/or with a user. For example, one or more interfaces 2410, 2412, 2414 may be adapted to transmit data, control signals, and administrative messages from the processor 2404 to applications installed in the host device and/or in the remote device. As another example, one or more interfaces 2410, 2412, 2414 may be adapted to allow a user or user device (e.g., a personal computer (PC), etc.) to interact/communicate with the processor system 2400. The processor system 2400 may contain additional components not shown in Fig. 24, such as a device for storing data (e.g., a non-volatile memory device, etc.).

In some embodiments, the processor system 2400 is included in a network device having access to a telecommunications network, or otherwise forming part of this network. In one example, the processor system 2400 is a device on the network side in a wireless (radio) or cable telecommunications network, such as a base station, a relay station, a scheduler, a controller, a gateway, a router, an application server or another device of the telecommunications network. In other embodiments, the processor system 2400 is a user-side device having access to a wireless (radio) or cable telecommunications network, such as a mobile station, user equipment (UE), a personal computer (PC), a tablet computer, a wearable communication device (e.g., a "smart" wristwatch, etc.) or some other device adapted for access to a telecommunications network.

In some embodiments, one or more interfaces 2410, 2412, 2414 connect the processor system 2400 to a transceiver adapted to transmit and receive signals via a telecommunications network. Fig. 25 shows a block diagram of a transceiver 2500 adapted to transmit and receive signals via a telecommunications network. The transceiver 2500 may be installed in a host device. As shown in the drawing, the transceiver 2500 comprises a network-side interface 2502, a coupling element (bridge) 2504, a transmitter 2506, a receiver 2508, a signal processor 2510, and a device-side interface 2512. The interface 2502 may comprise any component or set of components adapted to transmit or receive signals via a wireless (radio) or cable telecommunications network. The communication element 2504 may comprise any component or set of components adapted to facilitate two-way communication via the network-side interface 2502. The transmitter 2506 may comprise any component or set of components (e.g., an up-converter, a power amplifier, etc.) adapted to convert a video-band signal into a modulated carrier signal suitable for transmission via the network-side interface 2502. The receiver 2508 may comprise any component or set of components (e.g., a down-converter, a low-noise amplifier, etc.) adapted to convert a carrier signal received via the network-side interface 2502 into a video-band signal. The signal processor 2510 may comprise any component or set of components adapted to convert a video-band signal into a data signal suitable for communication via the device-side interface(s) 2512 or vice versa. The device-side interface(s) 2512 may comprise any components or set of components designed to exchange data signals between the signal processor 2510 and components in the host device (e.g., the processor system 2400, local area network (LAN) ports, etc.).

The transceiver 2500 can transmit and receive signals via a communication line of some type. In some embodiments, the transceiver 2500 transmits and receives signals via a radio communication line. For example, the transceiver 2500 can be a radio transceiver for communicating in accordance with a radio telecommunications protocol, such as a cellular protocol (e.g., long-term evolution (LTE)), etc.), a wireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or some other type of radio communication protocol (e.g., Bluetooth, near field communication (NFC), etc.). In such embodiments, the network side interface 2502 comprises one or more antennas/radiating elements. For example, network side interface 2502 may comprise a single antenna, multiple individual antennas, or a multi-antenna array configured for multi-level communications, such as single input multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO), and the like. In other embodiments, transceiver 2500 transmits and receives signals over a cable link, such as twisted pair cable, coaxial cable, fiber optic cable, and the like. Specific processor systems and/or transceivers may use all or only a subset of the components shown herein, and integration levels may vary from one device to another.

The following references are relevant to the subject matter of this application. Each of these documents is incorporated herein by reference in its entirety:

3GPP TS 38.213, V16.5.0 (2021-03), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Physical layer procedures for control (Release 16)”;

3GPP TS 37.213, V16.3.0 (2020-09), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical layer procedures for shared spectrum channel access (Release 16)”; and

ETSI EN 301 893 V2.1.1 (2017-05), “5 GHz RLAN; Harmonised Standard covering the essential requirements of article 3.2 of Directive 2014/53/EU”.

Although the present invention has been described in detail, it should be understood that various changes, substitutions and additions can be made without departing from the scope of the present invention as defined by the appended claims. Moreover, it is not intended to limit the scope of the present invention to the specific embodiments described herein, since even one of ordinary skill in the art can easily understand from the present description that processes, machines, manufacturing techniques, material compositions, means, methods or steps that already exist today or are later developed can perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacturing techniques, material compositions, means, methods or steps.

Claims (32)

1. A communication method containing: determining, by the user equipment, UE, in frame-based equipment, FBE, mode, that a communication channel in an unlicensed spectrum region is available for use; and transmission, by that UE on that link, of a first transmission to a gNB in a fixed frame period, FFP, associated with that UE, to initiate a first channel busy time, COT, within that FFP by that UE, the first transmission starting at the beginning of the FFP and ending before a free period within that FFP; and reception, by the UE, of information on a time interval during which the UE is allowed to initiate periodic COT intervals, this time interval containing the FFP period. 2. The method according to paragraph 1, wherein the procedure for determining that the communication channel is available comprises: implementation, by the UE equipment, of channel occupancy assessment, CCA. 3. The method according to paragraph 2, wherein the procedure for determining that the communication channel is available comprises: starting, by the UE, a countdown counter upon successful completion of the CCA assessment; and determining, by the UE equipment, that the communication channel is available when the number in the countdown counter decreases to zero. 4. The method according to any one of paragraphs 1-3, wherein the first transmission comprises a physical uplink control channel, PUCCH, a physical uplink shared channel, PUSCH, channel state information, CSI, a scheduling request, SR, a random access preamble, or a sounding reference signal, SRS. 5. The method according to any one of paragraphs 1-4, in which the first transmission occupies all or part of the bandwidth of the communication channel. 6. A communication method containing: receiving, by a gNB node, from a user equipment, UE, over a communication channel in an unlicensed spectrum region, the first transmission within a fixed frame period, FFP, in which the UE is in the frame-based equipment, FBE, mode; and determining, by the gNB, based on said first transmission, that the UE initiates a first channel busy time interval, COT, within that FFP period in response to that first transmission starting at the beginning of the FFP period and ending before the onset of a free period within that FFP period; transmission by the gNB to the UE of information about the time interval during which the UE is allowed to initiate periodic COT intervals, this time interval containing the FFP period. 7. The method of claim 6, wherein the first transmission comprises a PUCCH channel, a PUSCH channel based on a configured grant, channel state information, CSI, a scheduling request, SR, a random access preamble, or a sounding reference signal, SRS. 8. The method according to claim 6 or 7, wherein said first transmission occupies all or part of the bandwidth of the communication channel. 9. The method according to any one of paragraphs 6-8, additionally comprising: transmission, by the gNB node to the UE, of a configuration for configuring the UE to initiate a semi-static COT interval on the communication channel. 10. The method according to any one of paragraphs 6-9, additionally comprising: transmitting, by the UE equipment, configuration information regarding the first COT interval, the configuration information regarding the first COT interval comprising one or more of the following: COT interval index for the first COT interval; periodicity for the FFP period; the maximum permissible duration of the COT interval within this FFP period, MCOT; FFP period time shift; the minimum duration of the free period within the FFP period; the maximum duration of the free period within the FFP period; FFP period shift; or frequency resources for uplink transmissions during the first COT interval. 11. Communication equipment containing modules configured to implement the method according to any one of paragraphs 1-5. 12. Communication equipment containing modules configured to implement the method according to any one of paragraphs 6-10. 13. A communication system comprising the equipment according to item 11 and the equipment according to item 12.