HK1233389A1 - Lte-u communication devices and methods for aperiodic beacon and reference signal transmission - Google Patents

Abstract

An enhanced NodeB (eNB), user equipment (UE) and method of communicating using Long Term Evolution (LTE) licensed and unlicensed bands are generally described herein. The eNB may transmit a trigger signal to the UE. The trigger signal may be transmitted in the LTE unlicensed or licensed band and inform the UE of transmission of a reference signal from the eNB to the UE in the unlicensed band. The trigger signal may correspond to a single reference signal transmission or multiple periodic or consecutive reference signal transmissions. The trigger signal or a separate trigger signal may be used to inform the UE of a data transmission. The trigger signal may be transmitted at any point prior to or in the same subframe as the reference signal and the reference signal may be transmitted before, after or in the same subframe as the data.

Description

LTE-U communication device and method for aperiodic beacon and reference signal transmission

Priority declaration

This application claims priority benefits from U.S. application No.14/669,366 filed on 26/3/2015, which claims priority benefits from U.S. provisional patent application No.62/016,001 entitled "[ RAN1] APERIODIC BEACON SIGNAL for LTE-U ] (RAN 1 APERIODIC BEACON signaling for LTE-U) filed on 23/6/2014, each of which is incorporated herein by reference in its entirety.

Technical Field

Embodiments relate to radio access networks. Some embodiments relate to transmitting scheduling information for both licensed and unlicensed spectrum.

Background

Long Term Evolution (LTE) networks operate on multiple specific frequency bands and deliver a variety of information to an increasing number and type of User Equipments (UEs). Typically, the use of different communication technologies is limited to licensed bands specified by the federal government. The growth in network usage has stimulated interest in extending LTE usage beyond these licensed bands. LTE-unlicensed (LTE-U) allows UEs to use unlicensed spectrum in communications. Other networks, such as WiFi and bluetooth, coexist with LTE-U in unlicensed spectrum. This is a problem because periodic reference signaling messages occur between the LTE network and the UE. The reference signaling message may include cell-specific reference signals (CRS) used to schedule transmissions to multiple UEs and for channel estimation used in coherent demodulation at the UEs. The reference signaling message may include a Channel Quality Indication (CQI) indicating measurement of channel quality, a channel state information reference signal (CSI-RS) for measurement purposes, and a Discovery Reference Signal (DRS) specific to an individual UE. These and other periodic messages thus not only provide information about the communication channel, but also enable tracking of communications with the UE over time and/or frequency. These periodic messages may create problems in the communication between the WiFi device and the bluetooth device and/or create additional interference in the communication between the WiFi device and the bluetooth device. Also, some periodic messages may not reach the intended UE because the nature of the transmission in the unlicensed band is different from the commanded transmission in the licensed band.

It is therefore desirable to provide an efficient signaling mechanism for LTE-U devices while minimizing interference to other devices operating on the same unlicensed frequency band.

Drawings

In the drawings, like numerals may describe like components throughout the different views, which figures are not necessarily drawn to scale. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in this document.

Fig. 1 illustrates a portion of an end-to-end network architecture of an LTE network having various components of the network, in accordance with some embodiments.

Fig. 2 illustrates a functional block diagram of an eNB, according to some embodiments.

Fig. 3 illustrates a flow diagram of a method for an eNB to transmit aperiodic beacon signals, according to some embodiments.

Fig. 4A and 4B illustrate resource blocks in accordance with some embodiments.

Detailed Description

The following description and the annexed drawings set forth in detail certain illustrative embodiments, so as to enable those skilled in the art to practice the embodiments. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of others. The embodiments given in the claims encompass all possible equivalents of these embodiments.

Fig. 1 illustrates an example of a portion of an end-to-end network architecture of a Long Term Evolution (LTE) network having various components of the network, according to some embodiments. Network 100 may include a Radio Access Network (RAN)101 (e.g., the depicted E-UTRAN or evolved universal terrestrial radio access network) and a core network 120 (e.g., shown as an Evolved Packet Core (EPC)), coupled together by an S1 interface 115. For convenience and brevity, only a portion of the core network 120 and the RAN101 are shown in this example.

The core network 120 may include a Mobility Management Entity (MME)122, a serving gateway (serving GW)124, and a packet data network gateway (PDN GW) 126. RAN101 includes an evolved node b (enb)104 (which may act as a base station) to communicate with User Equipment (UE) 102. The enbs 104 may include macro enbs and Low Power (LP) enbs.

The MME 122 may be similar in function to the control plane of a conventional Serving GPRS Support Node (SGSN). The MME 122 may manage mobility aspects in access such as gateway selection and tracking area list management. The serving GW 124 may terminate the interface towards the RAN101 and route data packets between the RAN101 and the core network 120. In addition, the serving GW 124 may be a local mobility anchor for inter-eNB handover and may also provide an anchor for inter-3 GPP mobility. Other responsibilities may include lawful interception, billing, and some policy enforcement. The serving GW 124 and the MME 122 may be implemented in one physical node or in different physical nodes. The PDN GW126 may terminate the SGi interface towards the Packet Data Network (PDN). The PDN GW126 may route data packets between the EPC120 and the external PDN, and may perform policy enforcement and charging data collection. The PDN GW126 may also provide an anchor point for mobility devices with non-LTE access. The external PDN may be any kind of IP network, as well as an IP Multimedia Subsystem (IMS) domain. The PDN GW126 and the serving GW 124 may be implemented in one physical node or in different physical nodes.

The PDN GW126 and MME 122 may also be connected to a location server 130. The UE and eNB may communicate with the location server 130 via a user Plane (U-Plane) and/or a control Plane (C-Plane). The location server 130 may be a physical entity or a network entity that may collect measurement data and other location information from the UE102 and eNB104 and assist the UE102 with an estimate of the location of the UE102, thereby providing for network location-based calculations, as described in more detail below.

The enbs 104 (macro and micro enbs) may terminate the air interface protocol and may be the first point of contact for the UE 102. In some embodiments, the eNB104 may implement various logical functions of the RAN101 including, but not limited to, RNCs (radio network controller functions), such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. According to an embodiment, the UE102 may be configured to communicate OFDM communication signals with the eNB104 over a multicarrier communication channel in accordance with an OFDMA communication technique. The OFDM signal may include a plurality of orthogonal subcarriers.

S1 interface 115 may be an interface that separates RAN101 and EPC 120. The S1 interface 115 may be divided into two parts: S1-U and S1-MME, where S1-U may carry traffic data between eNB104 and serving GW 124, and S1-MME may be the signaling interface between eNB104 and MME 122. The X2 interface may be an interface between enbs 104. The X2 interface may include two parts: X2-C and X2-U. X2-C may be a control plane interface between eNBs 104, while X2-U may be a user plane interface between eNBs 104.

For cellular networks, LP cells can generally be used to extend coverage to indoor areas where outdoor signals do not reach well, or to increase network capacity in areas where usage is very dense. In particular, it may be desirable to enhance the coverage of a wireless communication system using different sized cells (macro cells, micro cells, pico cells, and femto cells) to improve system performance. Different sized cells may operate on the same frequency band, e.g., an LTE unlicensed frequency band, or may operate on different frequency bands, with each cell operating on a different frequency band or only cells with different sizes operating on different frequency bands. As used herein, the term Low Power (LP) eNB refers to any suitable relatively low power eNB for implementing a narrower cell (narrower than a macrocell), such as a femtocell (femtocell), pico (pico) cell, or microcell. A femto cell eNB may typically be provided by a mobile network operator to its residential or enterprise users. A femto cell may typically have the size of a residential gateway or smaller and may typically be connected to a subscriber's broadband line. Femto cells may connect to the mobile operator's mobile network and provide additional coverage typically ranging from 30 to 50 meters. Thus, the LP eNB may be a femto cell eNB as it is coupled through the PDN GW 126. Similarly, a picocell may be a wireless communication system that typically covers a small area, such as within a building (office, shopping center, train station, etc.), or recently on an airplane. A picocell eNB may typically connect to another eNB (e.g., a macro eNB) through an X2 link through its Base Station Controller (BSC) functionality. Thus, the LP eNB may be implemented with a picocell eNB since it is coupled to a macro eNB via an X2 interface. The pico eNB or other LP eNB may contain some or all of the functionality of the macro eNB. In some cases, it may be referred to as an access point base station or an enterprise femtocell.

Communications over the LTE network are divided into 10ms frames, each frame comprising ten 1ms subframes. Each subframe may in turn comprise two 0.5ms slots. Each slot may comprise 6-7 symbols depending on the system used. A Resource Block (RB) may be the smallest resource unit that may be allocated to a UE. A resource block may be 180kHz wide in frequency and one slot long in time. In frequency, a resource block may be 12x 15kHz subcarrier or 24x7.5kHz subcarrier wide. For most channels and signals, 12 subcarriers may be used per resource block. In Frequency Division Duplex (FDD) mode, the uplink and downlink frames can each be 10ms and are separated by frequency (full duplex) or by time (half duplex). In Time Division Duplexing (TDD), an uplink frame and a downlink frame may be transmitted on the same frequency and multiplexed in the time domain. The downlink resource grid may be used for downlink transmissions from the eNB to the UE. The grid may be a time-frequency grid, which is the physical resource of the downlink in each slot. Each column and each row of the resource grid may correspond to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain may correspond to one slot. The smallest time-frequency unit in the resource grid may be represented as a resource element. Each resource grid may comprise a plurality of the above-mentioned resource blocks, which describe the mapping of a particular physical channel to resource elements. Each resource block may include 12 (subcarriers) × 14 (symbols) ═ 168 resource elements.

There are several different physical downlink channels that may be transmitted using such resource blocks. Two of these physical downlink channels may be a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH). Each subframe may be divided into a PDCCH and a PDSCH. The PDCCH may normally occupy the first two symbols in each subframe and carry information about the resource allocation and transport format aspects of the PDSCH channel, H-ARQ information about the uplink shared channel, and the like. The PDSCH may carry higher layer signaling and user data for the UE and occupy the remaining symbols of the subframe. Typically, downlink scheduling (allocation of control and shared channel resource blocks to UEs within a cell) may be performed at the eNB based on channel quality information provided to the eNB from the UEs, and then downlink resource allocation information may be sent to each UE on the PDCCH used (allocated) for the respective UE. The PDCCH may contain Downlink Control Information (DCI), which is one of a plurality of formats that tell the UE how to find and decode data transmitted on the PDSCH in the same subframe from the resource grid. The DCI format may provide details such as the number of resource blocks, resource allocation type, modulation scheme, transport block, redundancy version, coding rate, and the like. Each DCI format may have a Cyclic Redundancy Code (CRC) and be scrambled with a Radio Network Temporary Identifier (RNTI), which identifies the target UE for which the PDSCH is intended. Using UE-specific RNTIs may limit decoding of DCI formats (and thus corresponding PDSCHs) to only the desired UE.

Fig. 2 illustrates a functional block diagram of a communication device, according to some embodiments. The communication device 200 may be a UE or eNB and may include physical layer circuitry (PHY)202 to transmit and receive radio frequency electrical signals to and from other enbs, other UEs, or other devices using one or more antennas 201 electrically connected to the PHY circuitry. The PHY circuitry 202 may include circuitry for modulation/demodulation, up/down conversion, filtering, amplification, and so forth. The communication device 200 may also include a medium access control layer (MAC) circuit 204 to control access to the wireless medium and to configure frames or packets for transmission over the wireless medium. The communication device 200 may also include processing circuitry 206 and memory 208 arranged to configure the various elements of the cellular device to perform the operations described herein. The memory 208 may be used to store information used to configure the processing circuit 206 to perform operations.

In some embodiments, the communication device 200 may be part of a portable wireless communication device, such as a Personal Digital Assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smart phone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure detector, etc.), a wearable device, a sensor, or other device that may receive and/or transmit information wirelessly. In some embodiments, the communication device 200 may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

The one or more antennas 201 used by the communication device 200 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas (patch antennas), loop antennas (loopantennas), microstrip antennas or other types of antennas suitable for transmission of RF signals. In some embodiments, one antenna with multiple apertures may be used instead of two or more antennas. In these embodiments, each aperture may be considered a separate antenna. In some multiple-input multiple-output (MIMO) embodiments, the antennas may be effectively separated to take advantage of the spatial diversity and different channel characteristics that may result between each antenna of a receiving station and each antenna of a transmitting station. In some MIMO embodiments, the antennas may be isolated by a distance of one tenth of a wavelength or more.

Although communication device 200 is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including Digital Signal Processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, Application Specific Integrated Circuits (ASICs), Radio Frequency Integrated Circuits (RFICs), and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, a functional element may refer to one or more processes operating on one or more processing elements.

The described embodiments may be implemented in one or a combination of hardware, firmware, and software. Embodiments may also be implemented as instructions stored on a computer-readable storage medium, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage medium may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage medium may include Read Only Memory (ROM), Random Access Memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, and other storage devices and media. In these embodiments, the one or more processors may be configured with instructions to perform the operations described herein.

In some embodiments, the processing circuitry 206 may be configured to receive OFDM communication signals over a multicarrier communication channel in accordance with an OFDMA communication technique. The OFDM signal may include a plurality of orthogonal subcarriers. In some broadband multicarrier embodiments, cellular device 200 may operate as part of a Broadband Wireless Access (BWA) network communication network, such as a Worldwide Interoperability for Microwave Access (WiMAX) communication network or a third generation partnership project (3GPP) Universal Terrestrial Radio Access Network (UTRAN) or a Long Term Evolution (LTE) communication network or an LTE-advanced communication network or a fifth generation (5G) LTE communication network or a high speed downlink/uplink access (HSDPA/HSUPA) communication network, although the scope of the invention is not limited in this respect.

Fig. 3 illustrates a flow diagram of a method for an eNB to transmit aperiodic beacon signals, according to some embodiments. Aperiodic beacon signals (also referred to herein as trigger signals) may be transmitted on either the licensed band or the unlicensed band, while aperiodic reference signals indicated by the aperiodic beacon signals may be transmitted on the unlicensed band. The aperiodic reference signal indicated by the aperiodic beacon signal can be transmitted in addition to the typically periodically transmitted reference signals (which can be periodically transmitted as many as several hundred milliseconds apart). In other embodiments, a non-periodic reference signal indicated by a non-periodic beacon signal may be transmitted in place of the periodically transmitted reference signal. In various embodiments, the timing of various steps may be adjusted, and some steps shown may not occur. The aperiodic reference signal may include at least one of: cell-specific reference signals (CRS), Channel Quality Indication (CQI), channel state information reference signals (CSI-RS), and Discovery Reference Signals (DRS). CRS may be used by UEs for cell search and initial acquisition of communications with the eNB, downlink channel quality measurements and downlink channel estimates for coherent demodulation or detection. The CQI may provide the eNB with channel quality information including carrier level Received Signal Strength Indication (RSSI) and Bit Error Rate (BER). The CSI-RS may be used to estimate the channel and report channel quality information. The DRS may include one or more of the signals described above and may be specific to an individual UE.

In step 302, the eNB may determine whether it desires to transmit a signal to one or more particular UEs. For example, the eNB may detect or request information from a UE or other communication device regarding whether there are currently any WiFi devices transmitting on the unlicensed frequency band. In one embodiment, the eNB may decide to transmit the trigger signal only when the eNB decides that the carrier is idle. It should be noted that the carrier in the licensed band may be a primary cell in which the UE may perform an initial RRC connection establishment procedure (or initiate a re-establishment procedure), or the carrier in the licensed band may be a secondary cell which may provide additional resources and may be configured after performing an RRC connection procedure using the primary cell. For example, the primary cell may be in a licensed band and the secondary cell may be in an unlicensed band.

If the eNB determines that a trigger signal is desired to be transmitted, the eNB may determine whether the transmission is a trigger signal (also referred to as an aperiodic beacon) in step 304. The trigger signal may indicate to the UE that the reference signal is to be transmitted on an unlicensed band. The trigger signal may be transmitted on the primary cell in a Physical Downlink Control Channel (PDCCH), an Enhanced Physical Downlink Control Channel (EPDCCH), a medium access control element (MAC-CE), or a Radio Resource Control (RRC) message. EPDCCH, like PDCCH, may be UE-specific and uses PDSCH resources to send control information. EPDCCH may be configured via RRC signaling. Each UE may be configured with two EPDCCH sets, the configuration may differ between the sets. For example, one or more bits of PDCCH or EPDCCH may be used as a trigger signal.

If the eNB determines at step 304 that the transmission is a trigger, the eNB may determine at step 306 the manner in which the trigger is transmitted to the UE. In one embodiment, the eNB may decide between sending the trigger signal to the UE via the LTE licensed band and sending the trigger signal to the UE via the unlicensed band (independent of sending the reference signal, the reference signal will be sent via the unlicensed band).

Further, the eNB may select a specific RNTI for the UE at step 308. As above, instead of using bits in the PDCCH, a new RNTI may be used. In one embodiment, a random access RNTI (typically used for a Physical Random Access Channel (PRACH) response) may be used to scramble the PDCCH or EPDCCH. In this case, the PDCCH or EPDCCH may be subsequently transmitted on the common search space to allow the UE (which must search the common search space) to find the PDCCH or EPDCCH. This may also allow multiple UEs capable of descrambling PDCCH or EPDCCH to receive the trigger message.

The eNB may also determine the timing between transmitting the trigger signal and transmitting the reference signal at step 310. The timing may indicate a difference in subframes between transmitting the trigger signal and transmitting the reference signal. The timing may take any value, i.e., the trigger signal and the reference signal may be transmitted in the same subframe or different subframes. In some embodiments, the trigger signal may be sent before the reference signal. In other embodiments, the trigger signal may be transmitted in the same subframe in which the reference signal is transmitted. Allowing the trigger signal to trigger the reference signal early for at least one subframe may help the UE prepare to receive the reference signal in a carrier in the unlicensed frequency band. For example, the PDCCH decoding time typically requires about 1 millisecond (ms). This means that a margin of at least 1ms is expected to enable the UE to receive the trigger signal in the PDCCH, decode it, and prepare to receive the reference signal in a carrier in the unlicensed band. In addition, a typical processing time of the PDSCH is 3 ms. A margin of at least 3ms is desirable if MAC-CE/RRC based triggering is employed. Therefore, it may be desirable for the eNB to set a delay of 4 subframes between transmitting the trigger signal and transmitting the reference signal to allow processing time to obtain data in the PDSCH and provide a usual acknowledgement in the PUCCH, which typically requires a time of one subframe. It should be noted that the desired times described above are typical, and the scope of the embodiments is not limited in this respect.

The eNB may next determine whether to transmit a reference signal at step 312. That is, in various embodiments, the eNB may determine whether to transmit one reference signal or multiple reference signals. According to embodiments, each reference signal may have a respective trigger signal or multiple reference signals may correspond to one trigger signal.

If the eNB determines to transmit one reference signal, the eNB transmits a trigger signal at step 314. In one embodiment, the eNB may transmit a trigger signal when it determines to transmit one. In another embodiment, the eNB may delay at least one subframe retransmission trigger signal. The timing between the transmission trigger signal and the reference signal and the frequency band of the transmission trigger signal may vary, which is determined by the eNB. In one embodiment, the trigger signal may be aperiodic and unscheduled.

As above, the trigger signal may be transmitted in a licensed or unlicensed frequency band. At step 316, the eNB may then determine whether to transmit data to the UE in addition to the reference signal. The number of trigger signals may vary depending on the determination of the eNB.

If the eNB decides not to transmit data, a reference signal may be transmitted to the UE on a carrier of the unlicensed band at step 318. In one embodiment, the reference signal may be transmitted on the same frequency band (e.g., unlicensed frequency band) as the trigger signal is transmitted. In another embodiment, the reference signal may be transmitted on a different frequency band (e.g., a licensed frequency band) than the transmission trigger signal. In one embodiment, the reference signal may be transmitted in the same subframe as the trigger signal is transmitted. In one embodiment, the reference signal may be transmitted in a subframe subsequent to the transmission of the trigger signal.

In one embodiment, an eNB may determine to transmit a data signal including data for a UE to the UE. In this embodiment, at step 320, the eNB may determine a time to transmit the data signal. The timing of transmitting the reference signal and the data signal may vary according to the determination of the eNB.

At step 322, the eNB may determine whether to transmit another trigger signal or scheduling information to the UE. In one embodiment, the further trigger signal may be used to inform the UE of the data transmission. In another embodiment, the same trigger signal that may inform the UE of the reference signal transmission may also inform the UE of the data transmission.

If the eNB determines to transmit another trigger signal or scheduling information to the UE, the eNB transmits another trigger signal to the UE to inform the UE of the data transmission at step 324. The timing between transmitting the trigger signal, transmitting another trigger signal, transmitting the reference signal, and transmitting the data signal (and the timing between transmitting the reference signal and the data signal) may be individually varied according to the determination of the eNB. In one embodiment, the trigger signals may be transmitted in the same subframe. In one embodiment, the trigger signals may be sent in different subframes. If these trigger signals are transmitted in different sub-frames, in one embodiment, the trigger signal indicating transmission of the reference signal may be transmitted before the trigger signal indicating transmission of the data signal. Alternatively, in one embodiment, the trigger signal indicating transmission of the data signal may be transmitted before the trigger signal indicating transmission of the reference signal. In one embodiment, one or both of these trigger signals may be aperiodic and unscheduled.

Regardless of whether another trigger signal is transmitted to the UE, the eNB may transmit a reference signal at a time determined by the eNB at step 326. In one embodiment, the time at which the reference signal is transmitted may be indicated in the trigger signal. The reference signal may be transmitted at a non-periodic time. That is, in one embodiment, the reference signal may be transmitted at a different time than the scheduled periodic reference signal transmission from the eNB in the licensed frequency band. In one embodiment, the reference signal may be transmitted at the same time and in the same subframe as the scheduled periodic reference signal transmission from the eNB in the licensed frequency band. The reference signal may include at least one of: cell-specific reference signals (CRS), Channel Quality Indication (CQI), channel state information reference signals (CSI-RS), and Discovery Reference Signals (DRS). In one embodiment, the aperiodic reference signal transmitted in the unlicensed band may be different from the reference signal transmitted on the licensed band, even if transmitted by the eNB in the same subframe.

At step 328, the eNB may transmit a data signal to the UE at the determined time. In one embodiment, the data signal may be transmitted in the same subframe as the reference signal. In one embodiment, the data signal and the reference signal may be transmitted in different subframes. If the data signal and the reference signal are transmitted in different subframes, in one embodiment, the data signal may be transmitted before the reference signal is transmitted. Alternatively, in one embodiment, the reference signal may be transmitted before the data signal. The timing of these transmissions may be independent of the timing of the transmission trigger signal. That is, in one embodiment, although the trigger signal indicating transmission of the reference signal is transmitted before the trigger signal indicating transmission of the data signal, the data signal may be transmitted before the reference signal is transmitted. In another embodiment, although the trigger signal indicating transmission of the data signal is transmitted before the trigger signal indicating transmission of the reference signal, the reference signal may be transmitted before the data signal is transmitted. In one embodiment, the trigger signal indicating transmission of the reference signal may be transmitted before the trigger signal indicating transmission of the data signal, and the reference signal may be transmitted before the data signal. In one embodiment, the trigger signal indicating transmission of the data signal may be transmitted before the trigger signal indicating transmission of the reference signal, and the data signal may be transmitted before the reference signal is transmitted. Thus, the order in which the trigger signals are transmitted may be different from the order in which the reference signals and the data signals are transmitted.

Fig. 4A and 4B illustrate resource blocks in accordance with some embodiments. As shown, in one embodiment, the reference signal may occupy the first two OFDM symbols in the subframe. Generally, the first OFDM symbol in each sub-frequency (subfrequency) in a resource block may be used by a UE for Automatic Gain Control (AGC) of a received signal, while the second OFDM symbol helps in time/frequency synchronization before data decoding. This may allow the starting symbol of the PDSCH to be defined so that data is not lost during AGC operation of the UE. The reference signal may be transmitted on the PDCCH in a specific resource block of a specific subframe only through one or two carrier sub-frequencies (of 12 available carrier sub-frequencies), as shown in fig. 4A; or may be carried by all sub-frequencies as shown in fig. 4B. In one embodiment, if two carrier sub-frequencies are used to carry the reference signal, the two carrier sub-frequencies may be separated by a maximum number of carrier sub-frequencies, e.g., the 6 th or 12 th carrier sub-frequency. As above, the data trigger and the reference signal trigger may be transmitted at any time relative to each other. For example, although fig. 3 shows the trigger signal to the reference signal being transmitted before the trigger signal/scheduling information for data transmission, in other embodiments, the data signal for the UE may be scheduled before the trigger signal to the reference signal is transmitted by the eNB, and the data signal may be separated by one or more subframes. Also, the transmission of the reference signal and the data signal may occur in any order, and thus, the relative timing of the transmission of the reference signal and the transmission of the data signal may be independent of the timing of the transmission of the trigger signal for the reference signal and the transmission of the trigger signal for the data. In various embodiments, the reference signal and the data signal may be transmitted in the same subframe or may be transmitted in different subframes.

If the eNB determines that more than one reference signal is to be transmitted to the UE at step 312, the eNB may determine whether multiple trigger signals are associated with the reference signals at step 330. Thus, in one embodiment, one trigger signal may be used to indicate to the UE to send multiple reference signals. In another embodiment, the transmission of the respective reference signals may be indicated by different trigger signals. In one embodiment, a plurality of trigger signals may be provided, each indicative of one or more reference signals.

If the eNB determines to transmit more than one reference signal to the UE, the eNB may select the timing of each reference signal at step 332. In one embodiment, the reference signals may be sent to the UE in the same unlicensed frequency band. In one embodiment, one of the reference signals may be transmitted to the UE in an unlicensed frequency band, while another of the reference signals may be transmitted to the UE in a licensed frequency band. In one embodiment, the reference signals may be transmitted in consecutive subframes. In one embodiment, the reference signals may be transmitted in non-consecutive subframes.

In step 334, the eNB transmits a trigger signal and a reference signal according to the respective determined timings. In one embodiment, each trigger signal may be transmitted corresponding to a different reference signal, so each trigger signal has an associated reference signal. In other embodiments, the eNB may transmit a mix of two or more trigger signals to the UE, where a trigger signal corresponds to the transmission of one reference signal and a trigger signal corresponds to the transmission of multiple reference signals. The timing between transmitting the trigger signal and transmitting the reference signal may vary according to the determination of the eNB. In one embodiment, the at least one trigger signal may be transmitted in the same subframe as the at least one reference signal is transmitted. For example, in one embodiment, at least one trigger signal and a corresponding reference signal may be transmitted in the same subframe, while at least one other trigger signal and a corresponding reference signal may be transmitted in different subframes. Alternatively, in one embodiment, the trigger signal and the reference signal are transmitted in non-overlapping subframes.

If the eNB determines that one trigger signal is associated with multiple reference signals at step 330, the eNB may transmit an activation message to the UE indicating transmission of a first reference signal of the multiple reference signals at step 336. The reference signals may then be transmitted in consecutive subframes or in non-consecutive subframes. For example, the reference signal may be transmitted periodically (e.g., every n subframes). In another embodiment, the reference signal set may be transmitted periodically (e.g., x reference signals are transmitted on x consecutive subframes every n subframes). In one embodiment, no activation message is sent, and the trigger message indicates the number and timing of reference signals.

At step 338, the eNB determines whether the last reference signal has been transmitted. The number of reference signals transmitted may be determined for each transmission or may be set for a particular set of reference signals and indicated by a trigger signal.

At step 340, the eNB sends a deactivation message to the UE to indicate that the last reference signal has been sent. In one embodiment, no deactivation message is sent, and as described above, the trigger signal indicates the number and timing of reference signals.

Further, the eNB may determine at step 322 that another trigger signal may be transmitted to indicate transmission of the data signal. That is, the trigger signal transmitted at step 314 may be used to indicate that both the reference signal and the data signal are transmitted. As described above, the reference signal and data may be transmitted in any order, and thus the relative timing of transmitting the reference signal and the data signal may be independent of the relative timing of transmitting the trigger signals for the reference signal and the data signal. In various embodiments, the reference signals and data may be transmitted in the same subframe or may be transmitted in different subframes.

If in step 304 the eNB may determine that no trigger signal will be transmitted, the data signal may instead be scheduled on an unlicensed band at step 344. In one embodiment, the data signals may be scheduled to be aperiodic while other signals are scheduled on the licensed frequency band.

At step 348, the eNB may determine whether data signals should be scheduled to multiple UEs. If the eNB determines that data signals should not be scheduled to multiple UEs, the eNB may determine that only one data signal (or multiple data signals) is scheduled to only one UE.

At step 356, the eNB may transmit a data signal schedule to the UE on the unlicensed band. In this case, the eNB may independently transmit data signals to the UE on an unlicensed band. Alternatively, the eNB may transmit the data signal to the UE without transmitting a separate schedule.

At step 348, the eNB may determine that data signals should be scheduled to multiple UEs. However, certain problems may arise if the eNB transmits to multiple UEs on an unlicensed band. Due to the opportunistic nature of transmissions on the unlicensed band and the control of the transmission medium on the licensed band, it may be better to transmit control channel transmissions, such as scheduling information, using the licensed band, while data transmissions are provided over the unlicensed band. This means that the licensed band can stop scheduling data transmission of multiple bands. To reduce the problems of increased control channel overhead and PDCCH blocking (i.e., the UE does not search for the correct carrier for control information) in the licensed band, group scheduling for multiple UEs or multiple resource blocks may be performed using a single PDCCH or EPDCCH resource. To provide this operation, the eNB determines whether to use a new RNTI in step 350.

If the eNB determines that a new RNTI should be used, the eNB may define a new group RNTI (G-RNTI) to address the desired group of UEs at step 352. In one embodiment, the eNB then scrambles the CRC of the DCI message using the G-RNTI addressing the desired group of UEs. In one embodiment, the CRC may be used by a respective UE configured with the G-RNTI for data scheduling.

If the eNB determines that a new group RNTI will not be defined, the eNB may define a bit field as part of the DCI scheduling transmission at step 354. In one embodiment, each bit in the bit field may represent a resource block and/or a UE in an unlicensed carrier. In one embodiment, one or more additional bits may be added to the DCI format being used, or one or more existing bits in an existing field may be replaced. According to the format, 0 or 1 may be used to indicate whether a corresponding resource block or UE is scheduled by using DCI information.

Whether or not the G-RNTI is defined, the eNB may transmit a data signal schedule to the UE on an unlicensed band at step 356. The eNB may use the scheduling to transmit data signals to the desired UE on the unlicensed frequency band. In one embodiment, the schedule may indicate that data signals are to be transmitted in consecutive subframes or in non-consecutive subframes. For example, the schedule may indicate that the data signals are to be transmitted periodically (e.g., every n subframes). In another embodiment, the schedule may indicate that the set of data signals is to be transmitted periodically (e.g., x reference signals are transmitted in x consecutive subframes every n subframes).

Although embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The accompanying drawings that form a part hereof show by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This detailed description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.

Such embodiments of the inventive subject matter may be referred to herein, individually and/or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.

In this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more than one, and independently of any other instances or usages of "at least one" or "one or more". In this document, the term "or" is used to refer to a non-exclusive or, such that "a or B" includes "a instead of B", "B instead of a", and "a and B" without an indication to the contrary. In this document, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein". In addition, in the following claims, the terms "comprise" and "comprise" are open-ended terms, that is, a system, UE, article, composition, formation, or process that includes elements in addition to those listed in a claim following the term is still considered to fall within the scope of the claim. In addition, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

The abstract of the present disclosure is provided to comply with 37c.f.r. § 1.72(b), which requires an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also in the foregoing detailed description, it can be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of the present disclosure should not be interpreted as reflecting an intention that: the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims (25)

1. An enhanced nodeb (enb), comprising:

a transceiver configured to transmit and receive signals to and from a User Equipment (UE) on a carrier in a licensed band and on a carrier in an unlicensed band; and

a processing circuit configured to:

causing the transceiver to transmit a trigger signal to the UE in one of the unlicensed frequency band and the licensed frequency band, the trigger signal configured to inform the UE to transmit an aperiodic reference signal from the eNB to the UE in the unlicensed frequency band;

cause the transceiver to transmit the aperiodic reference signal to the UE in the unlicensed frequency band in addition to transmitting a periodic reference signal in one of the unlicensed frequency band and the licensed frequency band, the aperiodic reference signal comprising one of a cell-specific reference signal (CRS), a Channel Quality Indication (CQI), a channel state information reference signal (CSI-RS), and a Discovery Reference Signal (DRS); and

causing the transceiver to receive measurements of at least one of channel quality and channel estimation from the UE based on the aperiodic reference signal.

2. The eNB of claim 1, wherein:

the processing circuit is configured to cause the transceiver to transmit the trigger signal in one of the unlicensed band and the licensed band using one of: a Physical Downlink Control Channel (PDCCH), an Enhanced Physical Downlink Control Channel (EPDCCH), a medium access control element (MAC-CE), or a Radio Resource Control (RRC) message.

3. The eNB of claim 2, wherein when the trigger signal is transmitted using one of PDCCH or EPDCCH, the processing circuitry is further configured to:

scrambling the one of PDCCH or EPDCCH with a Radio Network Temporary Identifier (RNTI) specific to the trigger signal.

4. The eNB of any one of claims 1-3, wherein,

the processing circuit is configured to cause the transceiver to transmit the trigger signal N subframes earlier than transmitting a non-periodic reference signal, where N is a non-negative integer.

5. The eNB of any one of claims 1-3, wherein:

the trigger signals correspond to a plurality of aperiodic reference signals, and

the processing circuit is further configured to cause the transceiver to transmit the aperiodic reference signal periodically or in consecutive subframes.

6. The eNB of any one of claims 1-3, wherein:

the trigger signals correspond to a plurality of aperiodic reference signals, and

the processing circuit is configured to cause the transceiver to trigger a start of transmitting the aperiodic reference signal using an activation message and to trigger a termination of transmitting the aperiodic reference signal using a deactivation message.

7. The eNB of any one of claims 1-3, wherein the processing circuitry is configured to:

causing the transceiver to transmit a second trigger signal to the UE in one of the unlicensed frequency band and the licensed frequency band, the second trigger signal configured to inform the UE of data transmissions from the eNB to the UE in the unlicensed frequency band; and

causing the transceiver to transmit data transmissions from the eNB to the UE in the unlicensed frequency band to the UE.

8. The eNB of claim 7, wherein the processing circuitry is configured to cause the transceiver to perform at least one of:

transmitting the second trigger signal before transmitting the trigger signal;

transmitting the aperiodic reference signal before transmitting the data transmission; or

Transmitting the aperiodic reference signal and the data transmission in the same subframe.

9. The eNB of any one of claims 1-3, wherein:

the trigger signal is further configured to inform the UE of a data transmission from the eNB to the UE in the unlicensed frequency band.

10. The eNB of any one of claims 1-3, wherein the processing circuitry is further configured to:

causing the transceiver to transmit scheduling information to a plurality of UEs, including the UE, in one of the unlicensed frequency band and the licensed frequency band, the scheduling information configured to inform the UEs of at least one data transmission from the eNB to the UEs in the unlicensed frequency band,

wherein the scheduling information includes scheduling of a plurality of physical resource blocks using one Physical Downlink Control Channel (PDCCH) or Enhanced Physical Downlink Control Channel (EPDCCH) resource.

11. The eNB of any one of claims 1-3, wherein the processing circuitry is further configured to:

causing the transceiver to transmit scheduling information to a plurality of UEs, including the UE, in one of the unlicensed frequency band and the licensed frequency band, the scheduling information configured to inform the UEs of at least one data transmission from the eNB to the UEs in the unlicensed frequency band,

wherein the scheduling information comprises Downlink Control Information (DCI) having an M-bit field, wherein each bit in the M-bit field represents a physical resource block in the unlicensed frequency band.

12. The eNB of any one of claims 1-3, wherein the processing circuitry is further configured to:

causing the transceiver to transmit scheduling information to a plurality of UEs, including the UE, in one of the unlicensed frequency band and the licensed frequency band, the scheduling information configured to inform the UEs of at least one data transmission from the eNB to the UEs in the unlicensed frequency band,

wherein the scheduling information comprises Downlink Control Information (DCI) having an M-bit field, each bit in the M-bit field representing an individual UE.

13. The eNB of any one of claims 1-3, wherein the processing circuitry is further configured to:

causing the transceiver to transmit scheduling information to a plurality of UEs, including the UE, in one of the unlicensed frequency band and the licensed frequency band, the scheduling information configured to inform the UEs of at least one data transmission from the eNB to the UEs in the unlicensed frequency band,

wherein the scheduling information uses a Physical Downlink Control Channel (PDCCH) or an Enhanced Physical Downlink Control Channel (EPDCCH) having Downlink Control Information (DCI) scrambled using a group radio network temporary identifier (G-RNTI) configured to identify the plurality of UEs.

14. The eNB of any one of claims 1-3, wherein the trigger signal is configured to indicate to the UE that the aperiodic reference signal is transmitted on a carrier in the unlicensed frequency band to allow the UE to make measurements on the aperiodic reference signal even in the event that the UE cannot make measurements on a periodic reference signal provided by the eNB on a carrier in the unlicensed frequency band due to the UE or a WiFi device proximate to the UE using a carrier in the unlicensed frequency band when the eNB provides the periodic reference signal to allow the UE to co-exist with the WiFi device.

15. A User Equipment (UE), comprising:

a transceiver configured to transmit and receive signals to and from an enhanced NodeB (eNB) on a carrier in a licensed frequency band and on a carrier in an unlicensed frequency band; and

a processing circuit configured to:

causing the transceiver to receive a trigger signal from the eNB in one of the unlicensed frequency band and the licensed frequency band, the trigger signal configured to inform the UE to transmit an aperiodic reference signal from the eNB to the UE in the unlicensed frequency band, the aperiodic reference signal comprising one of a cell-specific reference signal (CRS), a Channel Quality Indication (CQI), a channel state information reference signal (CSI-RS), and a Discovery Reference Signal (DRS);

causing the transceiver to receive the aperiodic reference signal from the eNB in the unlicensed frequency band in addition to transmitting a periodic reference signal in one of the unlicensed frequency band and the licensed frequency band;

performing measurements on at least one of channel quality and channel estimation based on the aperiodic reference signal; and

causing the transceiver to transmit measurements based on the aperiodic reference signal to the eNB.

16. The UE of claim 15, wherein:

the processing circuit is configured to cause the transceiver to receive the trigger signal N subframes earlier than the aperiodic reference signal, where N is a non-negative integer.

17. The UE of claim 15 or 16, wherein:

the trigger signals correspond to a plurality of aperiodic reference signals, and

the processing circuit is further configured to cause the transceiver to receive the aperiodic reference signal periodically or in consecutive subframes.

18. The UE of claim 15 or 16, wherein:

the trigger signals correspond to a plurality of aperiodic reference signals, and

the processing circuit is configured to cause the transceiver to receive an activation message configured to indicate a start of transmitting the aperiodic reference signal and a deactivation message configured to indicate a termination of transmitting the aperiodic reference signal.

19. The UE of claim 15 or 16, wherein the processing circuitry is configured to:

causing the transceiver to receive a second trigger signal from the eNB in one of the unlicensed frequency band and the licensed frequency band, the second trigger signal configured to inform the UE of a data transmission from the eNB to the UE in the unlicensed frequency band; and

causing the transceiver to receive, from the eNB, a data transmission from the eNB to the UE in the unlicensed frequency band.

20. The UE of claim 19, wherein the processing circuitry is configured to cause the transceiver to perform at least one of:

receiving the second trigger signal prior to receiving the trigger signal;

receiving the aperiodic reference signal before receiving the data transmission; or

Receiving the aperiodic reference signal and the data transmission in the same subframe.

21. The UE of claim 15 or 16, wherein:

the trigger signal is further configured to inform the UE of a data transmission from the eNB to the UE in the unlicensed frequency band.

22. A method of communicating using a licensed frequency band and an unlicensed frequency band, the method comprising:

transmitting, from an enhanced NodeB (eNB) to at least one User Equipment (UE) in one of the licensed and unlicensed bands, a trigger signal configured to inform the at least one UE to transmit at least one of an aperiodic reference signal or data transmission from the eNB to the at least one UE in the unlicensed band, the aperiodic reference signal comprising one of a cell-specific reference signal (CRS), a Channel Quality Indication (CQI), a channel state information reference signal (CSI-RS), and a Discovery Reference Signal (DRS);

transmitting the at least one of an aperiodic reference signal or data transmission from the eNB to the at least one UE in the unlicensed frequency band at a time indicated in the trigger signal; and

receiving, in response to transmitting the aperiodic reference signal to the at least one UE, a measurement of at least one of a channel quality and a channel estimate based on the aperiodic reference signal.

23. The method of claim 22, wherein at least one of:

a) the trigger signals correspond to a plurality of aperiodic reference signals, and

the method further includes transmitting the aperiodic reference signal periodically or in consecutive subframes;

b) the trigger signal is configured to inform the at least one UE of the transmission of both the aperiodic reference signal and the data transmission;

c) the trigger signal is configured to inform the at least one UE of the transmission of the aperiodic reference signal from the eNB to the at least one UE in the unlicensed frequency band, and

the method further comprises the following steps:

transmitting a second trigger signal from the eNB to the at least one UE on a carrier in the licensed band, the second trigger signal configured to inform the UE to transmit a data transmission from the eNB to the at least one UE in the unlicensed band; and

transmitting, to the at least one UE, a data transmission from the eNB to the at least one UE in the unlicensed frequency band at a time indicated in the second trigger signal.

24. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors of an enhanced nodeb (eNB) to cause the one or more processors to configure a transceiver of the eNB to communicate with Licensed Assisted Access (LAA) User Equipment (UE) operating on an unlicensed band, the eNB to:

transmitting a trigger signal to the UE on a carrier in the licensed band, the trigger signal configured to inform the UE to transmit at least one of an aperiodic reference signal or data transmission from the eNB to the at least one UE in the unlicensed band;

transmitting the at least one of an aperiodic reference signal or data transmission from the eNB to the UE in the unlicensed frequency band at a time indicated in the trigger signal, the aperiodic reference signal comprising one of a cell-specific reference signal (CRS), a Channel Quality Indication (CQI), a channel state information reference signal (CSI-RS), and a Discovery Reference Signal (DRS); and

receiving, in response to transmitting the aperiodic reference signal to the UE, a measurement of at least one of a channel quality and a channel estimate based on the aperiodic reference signal.

25. The non-transitory computer readable storage medium of claim 24, wherein at least one of:

a) the trigger signals correspond to a plurality of aperiodic reference signals, and

the aperiodic reference signal is transmitted periodically or in consecutive subframes; and

b) the trigger signal is configured to inform the UE of transmissions of both the aperiodic reference signal and data transmissions.