WO2025065612A1

WO2025065612A1 - Systems and methods for physical random access channel (prach) enhancement

Info

Publication number: WO2025065612A1
Application number: PCT/CN2023/122876
Authority: WO
Inventors: Wei Cao; Fangyu CUI; Nan Zhang
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2023-09-28
Filing date: 2023-09-28
Publication date: 2025-04-03
Anticipated expiration: 2026-03-28

Abstract

Presented are systems and methods for physical random access channel (PRACH) enhancement. A wireless communication device may receive a plurality of candidate values for each parameter of a set of PRACH parameters from a wireless communication node. The wireless communication device may determine at least one trigger condition. The wireless communication device may identify, for each parameter of the set of PRACH parameters, a first value from the plurality of candidate values, according to the at least one trigger condition, for use by the wireless communication device to perform a random access procedure.

Description

SYSTEMS AND METHODS FOR PHYSICAL RANDOM ACCESS CHANNEL (PRACH) ENHANCEMENT

TECHNICAL FIELD

The disclosure relates generally to wireless communications, including but not limited to systems and methods for physical random access channel (PRACH) enhancement.

BACKGROUND

The standardization organization Third Generation Partnership Project (3GPP) is currently in the process of specifying a new Radio Interface called 5G New Radio (5G NR) as well as a Next Generation Packet Core Network (NG-CN or NGC) . The 5G NR will have three main components: a 5G Access Network (5G-AN) , a 5G Core Network (5GC) , and a User Equipment (UE) . In order to facilitate the enablement of different data services and requirements, the elements of the 5GC, also called Network Functions, have been simplified with some of them being software based, and some being hardware based, so that they could be adapted according to need.

SUMMARY

The example embodiments disclosed herein are directed to solving the issues relating to one or more of the problems presented in the prior art, as well as providing additional features that will become readily apparent by reference to the following detailed description when taken in conjunction with the accompany drawings. In accordance with various embodiments, example systems, methods, devices and computer program products are disclosed herein. It is understood, however, that these embodiments are presented by way of example and are not limiting, and it will be apparent to those of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of this disclosure.

At least one aspect is directed to a system, method, apparatus, or a computer-readable medium of the following. A wireless communication device (e.g., a user equipment (UE) ) may receive a plurality of candidate values for each parameter of a set of physical random access channel (PRACH) parameters from a wireless communication node (e.g., a base station (BS) , or a radio access network (RAN) node) . The wireless communication device may determine at least one trigger condition. The wireless communication device may identify, for each parameter of the set of PRACH parameters, a first value from the plurality of candidate values, according to the at least one trigger condition, for use by the wireless communication device to perform a random access procedure (e.g., a 2-step or 4-step RACH) .

In some embodiments, the set of PRACH parameters may comprise at least one of: a Ncs value; a logical root sequence index; a subcarrier spacing (SCS) parameter; a frequency start parameter; a frequency division multiplexing (FDM) number; a PRACH configuration index; or a cyclic prefix (CP) length.

In some embodiments, the at least one trigger condition may comprise at least one of: the wireless communication device having or lacking a global navigation satellite system (GNSS) capability; presence or absence of abnormality in a GNSS operation or result, e.g., of the wireless communicate device; a time or frequency error exceeding or not exceeding an error threshold; the wireless communication device being a defined/certain user equipment (UE) type; the wireless communication device having a speed exceeding or not exceeding a speed threshold; the wireless communication device positioned (e.g., relative to a communication satellite) with an elevation angle exceeding or not exceeding an elevation angle threshold; the wireless communication device located at a distance to a reference location exceeding or not exceeding a distance threshold; or the wireless communication device having a power headroom exceeding or not exceeding a power headroom threshold.

In some embodiments, the wireless communication device may receive the plurality of candidate values via at least one of: a system information block (SIB) signaling (e.g., system information block type 1 (SIB1) or system information block type 19 (SIB19) ) , or a higher layer signaling specific to the wireless communication device.

In some embodiments, the wireless communication device may determine first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters. The first frequency domain resources can be determined for another wireless communication that does not satisfy the at least one trigger condition, to be used by preambles generated using second values for the set of PRACH parameters.

In some embodiments, the wireless communication device may determine first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters. Second frequency domain resources that are non-overlapping with respect to the first frequency domain resources, can be for another wireless communication that does not satisfy the at least one trigger condition (e.g., a speed threshold) . The second frequency domain resources to be used by preambles generated using second values for the set of PRACH parameters.

In some embodiments, the wireless communication device may determine first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters. Second frequency domain resources that are non-overlapping and having a different subcarrier spacing (SCS) with respect to the first frequency domain resources, can be for another wireless communication that does not satisfy the at least one trigger condition (e.g., an elevation angle threshold) . The second frequency domain resources to be used by preambles generated may use second values for the set of PRACH parameters.

In some embodiments, the first frequency domain resources can be determined according to at least one of: a msg1-FrequencyStart; a msgA-RO-FrequencyStart; a msg1-FDM; or a msgA-RO-FDM.

In some embodiments, the wireless communication device may receive an indication of a number of frequency domain resources to be used by the wireless communication device from the wireless communication node. In some embodiments, same or overlapping time domain resources can be determined for the wireless communication device and the another wireless communication device.

In some embodiments, a wireless communication node (e.g., a base station (BS) , or a radio access network (RAN) node) may send a plurality of candidate values for each parameter of a set of physical random access channel (PRACH) parameters to a wireless communication device (e.g., a UE) . The wireless communication device may determine at least one trigger condition. The wireless communication device may identify, for each parameter of the set of PRACH parameters, a first value from the plurality of candidate values, according to the at least one trigger condition, for use by the wireless communication device to perform a random access procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

Various example embodiments of the present solution are described in detail below with reference to the following figures or drawings. The drawings are provided for purposes of illustration only and merely depict example embodiments of the present solution to facilitate the reader's understanding of the present solution. Therefore, the drawings should not be considered limiting of the breadth, scope, or applicability of the present solution. It should be noted that for clarity and ease of illustration, these drawings are not necessarily drawn to scale.

FIG. 1 illustrates an example cellular communication network in which techniques disclosed herein may be implemented, in accordance with an embodiment of the present disclosure;

FIG. 2 illustrates a block diagram of an example base station and a user equipment device, in accordance with some embodiments of the present disclosure;

FIG. 3 illustrates an example adaptive physical random access channel (PRACH) configuration, in accordance with some embodiments of the present disclosure; and

FIG. 4 illustrates a flow diagram for physical random access channel (PRACH) enhancement, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

1. Mobile Communication Technology and Environment

FIG. 1 illustrates an example wireless communication network, and/or system, 100 in which techniques disclosed herein may be implemented, in accordance with an embodiment of the present disclosure. In the following discussion, the wireless communication network 100 may be any wireless network, such as a cellular network or a narrowband Internet of things (NB-IoT) network, and is herein referred to as “network 100. ” Such an example network 100 includes a base station 102 (hereinafter “BS 102” ; also referred to as wireless communication node) and a user equipment device 104 (hereinafter “UE 104” ; also referred to as wireless communication device) that can communicate with each other via a communication link 110 (e.g., a wireless communication channel) , and a cluster of cells 126, 130, 132, 134, 136, 138 and 140 overlaying a geographical area 101. In FIG. 1, the BS 102 and UE 104 are contained within a respective geographic boundary of cell 126. Each of the other cells 130, 132, 134, 136, 138 and 140 may include at least one base station operating at its allocated bandwidth to provide adequate radio coverage to its intended users.

For example, the BS 102 may operate at an allocated channel transmission bandwidth to provide adequate coverage to the UE 104. The BS 102 and the UE 104 may communicate via a downlink radio frame 118, and an uplink radio frame 124 respectively. Each radio frame 118/124 may be further divided into sub-frames 120/127 which may include data symbols 122/128. In the present disclosure, the BS 102 and UE 104 are described herein as non-limiting examples of “communication nodes, ” generally, which can practice the methods disclosed herein. Such communication nodes may be capable of wireless and/or wired communications, in accordance with various embodiments of the present solution.

FIG. 2 illustrates a block diagram of an example wireless communication system 200 for transmitting and receiving wireless communication signals (e.g., OFDM/OFDMA signals) in accordance with some embodiments of the present solution. The system 200 may include components and elements configured to support known or conventional operating features that need not be described in detail herein. In one illustrative embodiment, system 200 can be used to communicate (e.g., transmit and receive) data symbols in a wireless communication environment such as the wireless communication environment 100 of FIG. 1, as described above.

System 200 generally includes a base station 202 (hereinafter “BS 202” ) and a user equipment device 204 (hereinafter “UE 204” ) . The BS 202 includes a BS (base station) transceiver module 210, a BS antenna 212, a BS processor module 214, a BS memory module 216, and a network communication module 218, each module being coupled and interconnected with one another as necessary via a data communication bus 220. The UE 204 includes a UE (user equipment) transceiver module 230, a UE antenna 232, a UE memory module 234, and a UE processor module 236, each module being coupled and interconnected with one another as necessary via a data communication bus 240. The BS 202 communicates with the UE 204 via a communication channel 250, which can be any wireless channel or other medium suitable for transmission of data as described herein.

As would be understood by persons of ordinary skill in the art, system 200 may further include any number of modules other than the modules shown in FIG. 2. Those skilled in the art will understand that the various illustrative blocks, modules, circuits, and processing logic described in connection with the embodiments disclosed herein may be implemented in hardware, computer-readable software, firmware, or any practical combination thereof. To clearly illustrate this interchangeability and compatibility of hardware, firmware, and software, various illustrative components, blocks, modules, circuits, and steps are described generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware, or software can depend upon the particular application and design constraints imposed on the overall system. Those familiar with the concepts described herein may implement such functionality in a suitable manner for each particular application, but such implementation decisions should not be interpreted as limiting the scope of the present disclosure.

In accordance with some embodiments, the UE transceiver 230 may be referred to herein as an "uplink" transceiver 230 that includes a radio frequency (RF) transmitter and a RF receiver each comprising circuitry that is coupled to the antenna 232. A duplex switch (not shown) may alternatively couple the uplink transmitter or receiver to the uplink antenna in time duplex fashion. Similarly, in accordance with some embodiments, the BS transceiver 210 may be referred to herein as a "downlink" transceiver 210 that includes a RF transmitter and a RF receiver each comprising circuity that is coupled to the antenna 212. A downlink duplex switch may alternatively couple the downlink transmitter or receiver to the downlink antenna 212 in time duplex fashion. The operations of the two transceiver modules 210 and 230 may be coordinated in time such that the uplink receiver circuitry is coupled to the uplink antenna 232 for reception of transmissions over the wireless transmission link 250 at the same time that the downlink transmitter is coupled to the downlink antenna 212. Conversely, the operations of the two transceivers 210 and 230 may be coordinated in time such that the downlink receiver is coupled to the downlink antenna 212 for reception of transmissions over the wireless transmission link 250 at the same time that the uplink transmitter is coupled to the uplink antenna 232. In some embodiments, there is close time synchronization with a minimal guard time between changes in duplex direction.

The UE transceiver 230 and the base station transceiver 210 are configured to communicate via the wireless data communication link 250, and cooperate with a suitably configured RF antenna arrangement 212/232 that can support a particular wireless communication protocol and modulation scheme. In some illustrative embodiments, the UE transceiver 210 and the base station transceiver 210 are configured to support industry standards such as the Long Term Evolution (LTE) and emerging 5G standards, and the like. It is understood, however, that the present disclosure is not necessarily limited in application to a particular standard and associated protocols. Rather, the UE transceiver 230 and the base station transceiver 210 may be configured to support alternate, or additional, wireless data communication protocols, including future standards or variations thereof.

In accordance with various embodiments, the BS 202 may be an evolved node B (eNB) , a serving eNB, a target eNB, a femto station, or a pico station, for example. In some embodiments, the UE 204 may be embodied in various types of user devices such as a mobile phone, a smart phone, a personal digital assistant (PDA) , tablet, laptop computer, wearable computing device, etc. The processor modules 214 and 236 may be implemented, or realized, with a general purpose processor, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. In this manner, a processor may be realized as a microprocessor, a controller, a microcontroller, a state machine, or the like. A processor may also be implemented as a combination of computing devices, e.g., a combination of a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other such configuration.

Furthermore, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in firmware, in a software module executed by processor modules 214 and 236, respectively, or in any practical combination thereof. The memory modules 216 and 234 may be realized as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. In this regard, memory modules 216 and 234 may be coupled to the processor modules 210 and 230, respectively, such that the processors modules 210 and 230 can read information from, and write information to, memory modules 216 and 234, respectively. The memory modules 216 and 234 may also be integrated into their respective processor modules 210 and 230. In some embodiments, the memory modules 216 and 234 may each include a cache memory for storing temporary variables or other intermediate information during execution of instructions to be executed by processor modules 210 and 230, respectively. Memory modules 216 and 234 may also each include non-volatile memory for storing instructions to be executed by the processor modules 210 and 230, respectively.

The network communication module 218 generally represents the hardware, software, firmware, processing logic, and/or other components of the base station 202 that enable bi-directional communication between base station transceiver 210 and other network components and communication nodes configured to communication with the base station 202. For example, network communication module 218 may be configured to support internet or WiMAX traffic. In a typical deployment, without limitation, network communication module 218 provides an 802.3 Ethernet interface such that base station transceiver 210 can communicate with a conventional Ethernet based computer network. In this manner, the network communication module 218 may include a physical interface for connection to the computer network (e.g., Mobile Switching Center (MSC) ) . The terms “configured for, ” “configured to” and conjugations thereof, as used herein with respect to a specified operation or function, refer to a device, component, circuit, structure, machine, signal, etc., that is physically constructed, programmed, formatted and/or arranged to perform the specified operation or function.

The Open Systems Interconnection (OSI) Model (referred to herein as, “open system interconnection model” ) is a conceptual and logical layout that defines network communication used by systems (e.g., wireless communication device, wireless communication node) open to interconnection and communication with other systems. The model is broken into seven subcomponents, or layers, each of which represents a conceptual collection of services provided to the layers above and below it. The OSI Model also defines a logical network and effectively describes computer packet transfer by using different layer protocols. The OSI Model may also be referred to as the seven-layer OSI Model or the seven-layer model. In some embodiments, a first layer may be a physical layer. In some embodiments, a second layer may be a Medium Access Control (MAC) layer. In some embodiments, a third layer may be a Radio Link Control (RLC) layer. In some embodiments, a fourth layer may be a Packet Data Convergence Protocol (PDCP) layer. In some embodiments, a fifth layer may be a Radio Resource Control (RRC) layer. In some embodiments, a sixth layer may be a Non Access Stratum (NAS) layer or an Internet Protocol (IP) layer, and the seventh layer being the other layer.

Various example embodiments of the present solution are described below with reference to the accompanying figures to enable a person of ordinary skill in the art to make and use the present solution. As would be apparent to those of ordinary skill in the art, after reading the present disclosure, various changes or modifications to the examples described herein can be made without departing from the scope of the present solution. Thus, the present solution is not limited to the example embodiments and applications described and illustrated herein. Additionally, the specific order or hierarchy of steps in the methods disclosed herein are merely example approaches. Based upon design preferences, the specific order or hierarchy of steps of the disclosed methods or processes can be re-arranged while remaining within the scope of the present solution. Thus, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or acts in a sample order, and the present solution is not limited to the specific order or hierarchy presented unless expressly stated otherwise.

2. Systems and Methods for Physical Random Access Channel (PRACH) Enhancement

To expand a utilization of new radio (NR) access technologies, 5G connectivity via satellites and/or airborne vehicles can be considered as a promising application. The integrated terrestrial and non-terrestrial communication network is also a potential technical direction in 6G. New radio -non-terrestrial networks (NR-NTN) and Internet of Things -non-terrestrial networks (IoT-NTN) can be supported with an assumption of global navigation satellite system (GNSS) -capable UEs. To be more specific, a UE with GNSS capabilities can obtain the UE’s own position and can calculate the relative speed as well as the round-trip time (RTT) between the UE and a satellite using the broadcast ephemeris in system information. In such a way, time and frequency pre-compensation can be used in uplink (UL) transmission. As a result, NR PRACH configurations for terrestrial networks (TN) can be used directly.

However, in practical NTN scenarios, UEs with very diverse capabilities may probably coexist. For example, a low-cost UE without GNSS capability, a handheld UE with mobility, and a very small aperture terminal (VSAT) UEs with high transmission power may be served by a same satellite. In addition, NTN communications may face some abnormal conditions which do not exist in TN communications. For example, a UE with GNSS capabilities may have/use expired GNSS information during its communications. For another example, the time and/or frequency estimation at the UE side may be abnormal due to the rapid relative movement of the UE and the serving satellite. As a result, a fixed set of PRACH parameters for TN may not be enough to support these UEs with diverse capabilities as well as the abnormal cases.

To deal with this problem, a new method for adaptive PRACH configurations can be considered. The details are elaborated in the present disclosure. A brief outline of a portion of the present disclosure is provided in FIG. 3.

To support UEs with diverse capability and conditions, different PRACH parameter sets can be utilized. In some embodiments, only one PRACH parameter set is used by all UEs. To solve this problem, new methods are provided with one or more of the following aspects.

a) Adaptive parameters: Possible adaptive parameters can be analyzed to support multiple PRACH parameter sets.

b) Triggering conditions: The conditions for selection of a proper PRACH parameter set can be listed.

c) Signaling and new fields: To support multiple PRACH parameter sets, new fields can be utilized in a higher layer signaling.

d) Examples: Typical examples can be provided to show how to use different trigger conditions to determine the adaptive parameters and/or detailed signaling to be used.

A PRACH for TN can be used (e.g., directly reused) for a NTN, with the assumption of GNSS-capable UEs performing pre-compensation in PRACH transmission. Aspects of the PRACH are introduced below.

1. Format

The NR PRACH formats can be defined, for instance as shown in Table 1.

Table 1: PRACH preamble formats for L_RA=839 and Δf_RA∈ {1. 25, 5} kHz.

Table 2: Preamble formats for L_RA∈ {139, 571, 1151} and Δf_RA=15·2^μ kHz where μ∈ {0, 1, 2, 3, 5, 6} .

2. Configuration

The NR PRACH configurations can be defined. The related parameters can include one or more of the parameters listed below.

(1) RACH-ConfigCommon

(2) RACH-ConfigCommonTwoStepRA

(3) RACH-ConfigDedicated

(4) RACH-ConfigGeneric

(5) RACH-ConfigGenericTwoStepRA

3. Signaling

Common RACH configurations can be provided by a SystemInformationBlockType1 (SIB1) signaling. For example, the RACH-ConfigCommon can be related to an uplink BWP, such as, BWP-UplinkCommon in SIB1.

Dedicated RACH configurations can be provided by a UE-specific signaling. For example, the RACH-ConfigDedicated can be included in CellGroupConfig in the RRCSetup and RRCReconfiguration messages.

Implementation Example 1

To serve UEs with diverse capabilities as well as the abnormal cases, multiple sets of PRACH parameters can be provided to UEs. The UEs may select proper PRACH parameter set (s) according to their capability and/or abnormal cases.

1. Adaptive PRACH parameters

(1) Ncs value: Multiple zeroCorrelationZoneConfig values can be provided to determine the Ncs value. Each of the candidate value can be associated with a logical root sequence index.

(2) Logical root sequence index: Three higher layer parameters (e.g., prach-RootSequenceIndex, rootSequenceIndex-BFR, msgA-PRACH-RootSequenceIndex) can be used to determine the start root index for RACH with different purpose. Multiple logical root sequence index values for each purpose can be provided. Each of the candidate value can be associated with a Ncs value.

(3) SCS: Two higher layer parameters (e.g., msg1-SubcarrierSpacing, msgA-SubcarrierSpacing) can be used to determine the SCS for 4-step and 2-step RACH, respectively. Multiple SCS values can be provided for each type of RACH.

(4) Frequency start: Two higher layer parameters (e.g., msg1-FrequencyStart, msgA-RO-FrequencyStart) can be used to determine the frequency resource start for 4-step and 2-step RACH, respectively. Multiple frequency start values for each type can be provided. Each of the candidate values can be associated with a combination of (Ncs value, logical root sequence index) .

(5) FDM number: Four possible values (1, 2, 4, 8) can be used to determine the number of frequency resource blocks. If separate frequency start is used, separate FDM may be used. If a same frequency start is used and the FDM value is more than 1, multiple FDMed frequency resource blocks can be associated with different combination of (Ncs value, logical root sequence index) .

(6) PRACH configuration index: This parameter may determine the time resource together with the PRACH format. If multiple PRACH configuration indexes are provided, each of the candidate value can be associated with a combination of (PRACH format, Ncs value, logical root sequence index) .

2. Trigger conditions

(1) GNSS capability: For GNSS-capable UEs, accurate pre-compensation for UL synchronization is possible. In such case, the UE can use a PRACH parameter set with [smaller Ncs, smaller SCS, smaller CP] . In some embodiments, the combination of the parameters in the brackets can be “and/or” , which applies hereafter if no special explanation. On the contrary, those UEs without GNSS can use a PRACH parameter set with [larger Ncs, larger SCS, larger CP] .

(2) GNSS abnormality: If a GNSS-capable UE detects abnormal GNSS, the UE may not be able to carry out accurate pre-compensation for UL transmission. In such case, the UE can use a PRACH parameter set with larger [larger Ncs, larger SCS, larger CP] .

(3) Time/frequency error threshold: If a UE detects out-of synchronization and wants to initialize random access immediately, the UE may not be able to carry out accurate pre-compensation for UL transmission. In such case, the UE can use a PRACH parameter set with [larger Ncs, larger SCS, larger CP] . To be more specific, error threshold for time and/or frequency can be set. A UE can use a PRACH parameter set with [larger Ncs, larger SCS, larger CP] , when the time and/or frequency error exceeds the corresponding threshold.

(4) UE type: Though IoT UE and VSAT UE may be both equipped with GNSS, the accuracy of these two UE types may be different. The VSAT UE can probably support more accurate pre-compensation for UL synchronization. In such case, the UEs can use a PRACH parameter set with [smaller Ncs, smaller SCS, smaller CP] . On the contrary, those IoT UEs with weaker GNSS capability can use a PRACH parameter set with [larger Ncs, larger SCS, larger CP] . Different UE type may also have different transmission power. A VAST UE may have larger transmission power than an IoT UE. In such case, the VSAT UE can probably use a PRACH parameter set with [smaller symbol number] , while the IoT UE can use a PRACH parameter set with [larger symbol number] .

(5) UE speed threshold: UEs with high speed, e.g., those on a flight or on high speed train, may face higher Doppler shift than normal speed UEs. In such case, if the UE or the network determines the UE’s speed exceeding a speed threshold, the UE can use a PRACH parameter set with [larger Ncs, larger SCS, larger CP] .

(6) Elevation angle threshold: Small elevation angle generally leads to larger Doppler shift and round trip time (RTT) . If a UE determines its elevation angle is smaller than an elevation angle threshold, the UE can use a PRACH parameter set with [larger Ncs, larger SCS, larger CP] . Small elevation angle may also mean/indicate longer propagation path. Therefore, if a UE determines its elevation angle is smaller than an elevation angle threshold, the UE can use a PRACH parameter set with [larger symbol number] .

(7) Distance threshold: The network may pre-compensate Doppler shift in its DL transmission to guarantee zero Doppler shift at a reference location, e.g., the beam center. The UEs with long distance to the reference location may face residual Doppler, which may lead to imperfect pre-compensation for UL synchronization. In such case, if the UE determines its distance to the reference location exceeding a distance threshold, the UE can use a PRACH parameter set with [larger Ncs, larger SCS, larger CP] .

(8) Power headroom threshold: A UE’s power headroom indicates how much transmission power left for a UE to use in addition to the power being used by current transmission. If the power headroom is lower than a power headroom threshold, the UE can use a PRACH parameter set with [larger symbol number] .

The benefits of determining the trigger conditions can include providing adaptive RACH support for UEs with varying capabilities and conditions, as well as enabling the BS to initially assess the UE's capabilities and conditions based on the set conditions.

3. Signaling and new fields

(1) System information: For example, extra fields can be added in SIB1 or SIB19 specific for NTN.

① New fields can be added in RACH-ConfigGeneric, which is marked with bold font. All possible new fields can be listed in the information element (IE) , although only part of them may exist in the IE according to practical requirements. This principle can apply for other IEs with new fields hereafter if no special explanation.

② New fields can be added in RACH-ConfigGenericTwoStepRA, which is marked with bold font.

③ New fields can be added in RACH-ConfigCommon, which is marked with bold font. RACH-ConfigCommon information element

④ New fields can be added in RACH-ConfigCommonTwoStepRA, which is marked with bold font.

(2) UE-specific signaling: Extra fields can be added in RRCSetup and/or RRCReconfiguration, which can be used in handover (including conditional handover) .

① New fields can be added in RACH-ConfigGeneric. The change can be found in the counterpart in system information shown above.

② New fields can be added in RACH-ConfigGenericTwoStepRA. The change can be found in the counterpart in system information shown above.

③ New fields can be added in RACH-ConfigCommon. The change can be found in the counterpart in system information shown above.

④ New fields can be added in RACH-ConfigCommonTwoStepRA. The change can be found in the counterpart in system information shown above.

⑤ New fields can be added in BeamFailureRecoveryConfig, which is marked with bold font.

BeamFailureRecoveryConfig information element

All possible new fields are listed in this implementation example, but in actual applications, maybe only some of them may be added to the information element (IE) .

4. Examples

(1) Example 1: In a same time and frequency resource, multiple PRACH parameter sets can be utilized.

In this example, a same time and frequency resource can be used to accommodate multiple PRACH with different parameter sets. In the NTN, both UEs with GNSS capability and without GNSS capability can be to be supported. The UEs with GNSS capability can use a PRACH parameter set with [smaller Ncs] . The UEs without GNSS capability can use a PRACH parameter set with [larger Ncs] . Two different logical root sequence indexes can be used to provide two non-overlapped sets of available roots. The number of roots in each available root set can be determined by the corresponding Ncs value.

There can be 64 preambles for each PRACH parameter set using the same time-frequency resource. For the first PRACH parameter set, the 64 preambles can be enumerated in increasing order of first increasing cyclic shift determined by the corresponding Ncs of a logical root sequence, and then in increasing order of the logical root sequence index, starting with the index obtained from the higher-layer parameter prach-RootSequenceIndex or rootSequenceIndex-BFR or by msgA-PRACH-RootSequenceIndex if configured and a type-2 random-access procedure is initiated. Additional preamble sequences, in case 64 preambles cannot be generated from a single root Zadoff-Chu sequence, can be obtained from the root sequences with the consecutive logical indexes until all the 64 sequences are found. For the second PRACH parameter set, the 64 preamble can be generated as described above, while the logical root sequence index starts with the index obtained from the higher-layer parameter prach-RootSequenceIndex-NTN or rootSequenceIndex-BFR-NTN or by msgA-PRACH-RootSequenceIndex-NTN.

The benefit of this example is that only a common time and frequency resource allocation is needed. A same PRACH format with different adaptive parameters can be used by UEs with different capabilities or conditions. The adaptive parameters can be at least one of: a Ncs value or a logical root starting index. The UEs with GNSS capability and without GNSS capability can be distinguished at the BS side by the roots. According to the root used, the BS may determine the corresponding Ncs and may decode the preamble correctly.

The details are elaborated below.

① To support UEs with GNSS capability, a PRACH parameter set with following parameters {LRA=139, [Ncs=6] , SCS=15kHz, PRACH format=A1} can be used. With this PRACH parameter set, the number of roots is 3 to provide 64 preambles. The logical root sequence index can be 0. To support UEs without GNSS capability, a PRACH parameter set with following parameters {LRA=139, [Ncs=19] , SCS=15kHz, PRACH format=A1} can be used. With this PRACH parameter set, the number of roots can be 10 to provide 64 preambles. The logical root sequence index can be 4. All other adaptive PRACH parameters can be set as the same.

② The two Ncs values can be provided in RACH-ConfigGeneric via a SIB1 and/or RRCSetup/RRCReconfiguration, using zeroCorrelationZoneConfig=3 and zeroCorrelationZoneConfig2=10, respectively.

③ The two logical root sequence indexes can be provided in RACH-ConfigCommon via a SIB1 and/or RRCSetup/RRCReconfiguration, using prach-RootSequenceIndex= [CHOICE=l139, 0] and prach-RootSequenceIndex-NTN= [CHOICE=l139, 4] . If the roots for the two PRACH parameter sets are continuous, then the parameter prach-RootSequenceIndex-NTN can be omitted.

(2) Example 2: In a time and frequency resource with FDM>=2, multiple PRACH parameter sets may use non-overlapped FDMed PRACH resource.

In this example, FDMed frequency resource can be used to accommodate multiple PRACH with different parameter sets. In the NTN, both UEs on high speed train and pedestrian-based UEs can be to be supported. The BS can provide a speed threshold (or a high speed flag, or more than one speed thresholds) to UEs. If the UE or the BS determines a UE’s speed exceeding the speed threshold, the UE can use a PRACH parameter set with [larger Ncs] , and PRACH transmission may use the corresponding FDMed PRACH resource.

The preamble generation method can be the same as that in the Example 1.

The frequency resource mapping may require extra change. The preambles can only be transmitted in the frequency resources given by either the higher-layer parameter msg1-FrequencyStart or msgA-RO-FrequencyStart if configured. The PRACH frequency resources n_RA∈ {0, 1, …, M/2-1} can be used by the 64 preambles generated using the first PRACH parameter set, and the PRACH frequency resources n_RA∈ {M/2, M/2+1, …, M-1} can be used by the 64 preambles generated using the second PRACH parameter set, where M equals the higher-layer parameter msg1-FDM or msgA-RO-FDM if configured, can be numbered in increasing order within the initial uplink bandwidth part during initial access, starting from the lowest frequency. Otherwise, n_RA can be numbered in increasing order within the active uplink bandwidth part, starting from the lowest frequency.

The benefit of this example is that only a common time and frequency resource allocation indication is utilized. A same PRACH format with different adaptive parameters can be used by UEs with different capabilities or conditions. The adaptive parameters can be at least one of: Ncs and logical root starting index combination, or mapping relationship between FDM and each combination. The PRACH with different combination of {Ncs, logical root starting index} uses non-overlapping frequency domain resources, which leads to good reception performance due to less inter-root interference. The UEs with different speed may use non-overlapping frequency resource and be distinguished at the BS side by the frequency resource. In conjunction with Example 1, different combinations are placed at different FDM positions.

The details related to the Ncs and logical root sequence index can be the same as those in the Example 1. Only extra details are elaborated below.

① The BS may provide a speed threshold of 250km/h, which can be a pre-defined value, or provided via SI and/or UE-specific signaling.

② The frequency resources can be determined msg1-FrequencyStart=0 and msg1-FDM=4.

The PRACH frequency resources n_RA∈ {0, 1} can be used by the 64 preambles generated using the first PRACH parameter set (corresponding to the UEs with speed not exceeding the speed threshold) . The PRACH frequency resources n_RA∈ {2, 3} can be used by the 64 preambles generated using the second PRACH parameter set (corresponding to the UEs with speed exceeding the speed threshold) .

③ If the number of high speed UEs are small, less than half of the FDMed PRACH frequency resources can be used. In such case, an extra indication of the number FDMed resource (called N) can be provided by the BS to the UEs. The applicable condition of N can be indicated. For example, the BS may provide N=1 for UEs with speed exceeding the speed threshold. The PRACH frequency resources n_RA∈ {0, 1, 2} can be used by the 64 preambles generated using the first PRACH parameter set (corresponding to the UEs with speed not exceeding the speed threshold) , where the number of frequency resource is M-N=4-1=3. The PRACH frequency resources n_RA∈ {3} can be used by the 64 preambles generated using the second PRACH parameter set (corresponding to the UEs with speed exceeding the speed threshold) , where the number of frequency resource is N=1. This example can support uneven distribution of FDMed frequency domain resources, which may improve resource utilization.

(3) Example 3: Multiple PRACH parameter sets may use non-overlapped frequency resource with separate definition and a same time resource.

In this example, dedicated non-overlapped frequency resources can be used to accommodate multiple PRACH with different parameter sets, where separate frequency start and FDM indications can be provided by the BS. In the NTN, UEs at beam edge and beam center may have diverse elevation angles. An elevation angle threshold can be provided by the BS via system information and/or UE-specific signaling. If a UE determines its elevation angle is smaller than an elevation angle threshold, the UE can use a PRACH parameter set with [larger SCS] to combat larger residual Doppler shift. The BS may need to use separate frequency resources for the PRACH transmission using different SCSs.

The preamble generation method can be the same as that in the Example 1.

The frequency resource mapping may require extra change. For the 64 preambles generated using the first PRACH parameter set (corresponding to the UEs with elevation angle not exceeding the elevation angle threshold) , the frequency resources can be determined msg1-FrequencyStart=0 (e.g., the higher-layer parameter msg1-FrequencyStart or msgA-RO-FrequencyStart) and msg1-FDM=2 (e.g., the higher-layer parameter msg1-FDM or msgA-RO-FDM) . For the 64 preambles generated using the second PRACH parameter set (corresponding to the UEs with elevation angle exceeding the elevation angle threshold) , the frequency resources can be determined msg1-FrequencyStart-NTN=24 (e.g., the new higher-layer parameter msg1-FrequencyStart-NTN or msgA-RO-FrequencyStart-NTN) and msg1-FDM-NTN=2 (e.g., the new higher-layer parameter msg1-FDM-NTN or msgA-RO-FDM-NTN) .

The benefit of this example is that PRACH preambles with different adaptive parameters can be supported to serve UEs with different residual Doppler shifts. The PRACH format can be the same. The adaptive parameters may include at least one of: Ncs and logical root starting index combination, SCS, or frequency start and FDM. The PRACH with different adaptive parameters uses non-overlapping frequency domain resources. The BS may obtain a rough range of the UE’s condition (e.g., residual Doppler shift) according to the frequency resource used. In conjunction with Example 1, different combinations can be placed on different frequency domain resources.

① The BS may provide an elevation angle threshold of 60 degree, which can be a pre-defined value, or provided via SI and/or UE-specific signaling.

② To support UEs elevation angle not exceeding 60 degree, a PRACH parameter set with following parameters {LRA=139, Ncs=19, [SCS=15kHz] , PRACH format=A1} can be used, in which SCS is provided by msg1-SubcarrierSpacing. To support UEs elevation angle exceeding 60 degrees, a PRACH parameter set with following parameters {LRA=139, Ncs=19, [SCS=30kHz] , PRACH format=A1} can be used, in which SCS is provided by msg1-SubcarrierSpacing-NTN.

③ The frequency resources can be determined by {msg1-FrequencyStart=0, msg1-FDM=2} for the UEs using SCS=15kHz. The frequency resources can be determined by {msg1-FrequencyStart-NTN=24, msg1-FDM-NTN=2} for the UEs using SCS=30Hz.

④ If the frequency resources for the two PRACH parameter sets are continuous, the parameter msg1-FrequencyStart-NTN can be omitted.

⑤ If the FDM frequency resource number for the two PRACH parameter sets are the same, the parameter msg1-FDM-NTN can be omitted.

⑥ If the SCS used by the two PRACH parameter sets are the same, the parameter msg1-SubcarrierSpacing-NTN can be omitted.

It should be understood that one or more features from the above implementation examples are not exclusive to the specific implementation examples and/or embodiments, but can be combined in any manner (e.g., in any priority and/or order, concurrently or otherwise) .

FIG. 4 illustrates a flow diagram of a method 400 for physical random access channel (PRACH) enhancement. The method 400 may be implemented using any one or more of the components and devices detailed herein in conjunction with FIGs. 1–3. In overview, the method 400 may be performed by a wireless communication device, in some embodiments. Additional, fewer, or different operations may be performed in the method 400 depending on the embodiment. At least one aspect of the operations is directed to a system, method, apparatus, or a computer-readable medium.

A wireless communication device (e.g., a user equipment (UE) ) may receive a plurality of candidate values for each parameter of a set of physical random access channel (PRACH) parameters from a wireless communication node (e.g., a base station (BS) , or a radio access network (RAN) node) . The wireless communication device may determine at least one trigger condition. The wireless communication device may identify, for each parameter of the set of PRACH parameters, a first value from the plurality of candidate values, according to the at least one trigger condition, for use by the wireless communication device to perform a random access procedure (e.g., a 2-step or 4-step RACH) .

In some embodiments, the at least one trigger condition may comprise at least one of: the wireless communication device having or lacking a global navigation satellite system (GNSS) capability; presence or absence of abnormality in a GNSS operation or result; a time or frequency error exceeding or not exceeding an error threshold; the wireless communication device being a defined user equipment (UE) type; the wireless communication device having a speed exceeding or not exceeding a speed threshold; the wireless communication device positioned with an elevation angle exceeding or not exceeding an elevation angle threshold; the wireless communication device located at a distance to a reference location exceeding or not exceeding a distance threshold; or the wireless communication device having a power headroom exceeding or not exceeding a power headroom threshold.

In some embodiments, the wireless communication device may determine first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters. The first frequency domain resources can be determined for another wireless communication that does not satisfy/meet the at least one trigger condition, to be used by preambles generated using second values for the set of PRACH parameters.

In some embodiments, the wireless communication device may determine first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters. Second frequency domain resources that are non-overlapping and having a different subcarrier spacing (SCS) with respect to the first frequency domain resources, can be for another wireless communication that does not satisfy the at least one trigger condition (e.g., an elevation angle threshold) . The second frequency domain resources to be used by preambles generated using second values for the set of PRACH parameters.

While various embodiments of the present solution have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. Likewise, the various diagrams may depict an example architectural or configuration, which are provided to enable persons of ordinary skill in the art to understand example features and functions of the present solution. Such persons would understand, however, that the solution is not restricted to the illustrated example architectures or configurations, but can be implemented using a variety of alternative architectures and configurations. Additionally, as would be understood by persons of ordinary skill in the art, one or more features of one embodiment can be combined with one or more features of another embodiment described herein. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described illustrative embodiments.

It is also understood that any reference to an element herein using a designation such as "first, " "second, " and so forth does not generally limit the quantity or order of those elements. Rather, these designations can be used herein as a convenient means of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element in some manner.

Additionally, a person having ordinary skill in the art would understand that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits and symbols, for example, which may be referenced in the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

A person of ordinary skill in the art would further appreciate that any of the various illustrative logical blocks, modules, processors, means, circuits, methods and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two) , firmware, various forms of program or design code incorporating instructions (which can be referred to herein, for convenience, as "software" or a "software module) , or any combination of these techniques. To clearly illustrate this interchangeability of hardware, firmware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in various ways for each particular application, but such implementation decisions do not cause a departure from the scope of the present disclosure.

Furthermore, a person of ordinary skill in the art would understand that various illustrative logical blocks, modules, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, modules, and circuits can further include antennas and/or transceivers to communicate with various components within the network or within the device. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein.

If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program or code from one place to another. A storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD- ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

In this document, the term "module" as used herein, refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. Additionally, for purpose of discussion, the various modules are described as discrete modules; however, as would be apparent to one of ordinary skill in the art, two or more modules may be combined to form a single module that performs the associated functions according embodiments of the present solution.

Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present solution. It will be appreciated that, for clarity purposes, the above description has described embodiments of the present solution with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements or domains may be used without detracting from the present solution. For example, functionality illustrated to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Hence, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

Various modifications to the embodiments described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the scope of this disclosure. Thus, the disclosure is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the novel features and principles disclosed herein, as recited in the claims below.

Claims

A method comprising:

receiving, by a wireless communication device from a wireless communication node, a plurality of candidate values for each parameter of a set of physical random access channel (PRACH) parameters;

determining, by the wireless communication device, at least one trigger condition; and

identifying, by the wireless communication device for each parameter of the set of PRACH parameters, a first value from the plurality of candidate values, according to the at least one trigger condition, for use by the wireless communication device to perform a random access procedure.
The method of claim 1, wherein the set of PRACH parameters comprises at least one of:

a Ncs value;

a logical root sequence index;

a subcarrier spacing (SCS) parameter;

a frequency start parameter;

a frequency division multiplexing (FDM) number;

a PRACH configuration index; or

a cyclic prefix (CP) length.
The method of claim 1, wherein the at least one trigger condition comprises at least one of:

the wireless communication device having or lacking a global navigation satellite system (GNSS) capability;

presence or absence of abnormality in a GNSS operation or result;

a time or frequency error exceeding or not exceeding an error threshold;

the wireless communication device being a defined user equipment (UE) type;

the wireless communication device having a speed exceeding or not exceeding a speed threshold;

the wireless communication device positioned with an elevation angle exceeding or not exceeding an elevation angle threshold;

the wireless communication device located at a distance to a reference location exceeding or not exceeding a distance threshold; or

the wireless communication device having a power headroom exceeding or not exceeding a power headroom threshold.
The method of claim 1, wherein the wireless communication device receives the plurality of candidate values via at least one of: a system information block (SIB) signaling, or a higher layer signaling specific to the wireless communication device.
The method of claim 1, comprising:

determining, by the wireless communication device, first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters,

wherein the first frequency domain resources are determined for another wireless communication that does not satisfy the at least one trigger condition, to be used by preambles generated using second values for the set of PRACH parameters.
The method of claim 1, comprising:

determining, by the wireless communication device, first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters,

wherein second frequency domain resources that are non-overlapping with respect to the first frequency domain resources, are for another wireless communication that does not satisfy the at least one trigger condition, the second frequency domain resources to be used by preambles generated using second values for the set of PRACH parameters.
The method of claim 1, comprising:

determining, by the wireless communication device, first frequency domain resources for the wireless communication device, to be used by preambles generated using first values for the set of PRACH parameters,

wherein second frequency domain resources that are non-overlapping and having a different subcarrier spacing (SCS) with respect to the first frequency domain resources, are for another wireless communication that does not satisfy the at least one trigger condition, the second frequency domain resources to be used by preambles generated using second values for the set of PRACH parameters.
The method of claim 6 or 7, wherein the first frequency domain resources are determined according to at least one of:

a msg1-FrequencyStart;

a msgA-RO-FrequencyStart;

a msg1-FDM; or

a msgA-RO-FDM.
The method of claim 1, comprising:

receiving, by the wireless communication device from the wireless communication node, an indication of a number of frequency domain resources to be used by the wireless communication device.
The method of claim 5, 6, or 7, wherein same or overlapping time domain resources are determined for the wireless communication device and the another wireless communication device.
A method comprising:

sending, by a wireless communication node to a wireless communication device, a plurality of candidate values for each parameter of a set of physical random access channel (PRACH) parameters,

wherein the wireless communication device determines at least one trigger condition, and wherein the wireless communication device identifies, for each parameter of the set of PRACH parameters, a first value from the plurality of candidate values, according to the at least one trigger condition, for use by the wireless communication device to perform a random access procedure.
A non-transitory computer readable medium storing instructions, which when executed by at least one processor, cause the at least one processor to perform the method of any one of claims 1-11.
An apparatus comprising:

at least one processor configured to perform the method of any one of claims 1-11.