Cross-component carrier beam management method and apparatus

Abstract

A Cross-CC beam management method is proposed. A transceiver uses channel measurements of multiple CCs to obtain a beam vector, so that better performance can be achieved by exploiting a wideband channel. The transceiver derives a beam vector by using channel measurements of a selected set of CCs with a carrier weight factor applied. The transceiver exploits a beam management reference signal (BM-RS) of the selected set of CCs to derive a beam vector, such as a best beam. In one embodiment, the carrier weight factor can be a number of BM-RS REs per CC. In another embodiment, the channel measurements can be SNR / RSRP, and the carrier weight factor can be a SNR / RSRP per CC.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 63 / 296,006, filed January 3, 2022, entitled “Cross-CC AWV-OPT,” the subject matter of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The disclosed embodiments relate generally to mobile communication networks, and more specifically, to methods for cross component carrier (Cross-CC) beam management. BACKGROUND

[0004] Fifth generation new radio (5G NR) is an improved radio access technology (RAT) that provides higher data rates, higher reliability, lower latency, and improved system capacity. In an NR system, a terrestrial wireless access network includes multiple base stations (BSs), known as generation Node-Bs (gNBs), that communicate with multiple mobile stations, known as user equipment (UEs). A UE can communicate with a base station (BS) or gNB through the downlink and uplink. The downlink (DL) refers to communication from the base station to the UE. The uplink (UL) refers to communication from the UE to the base station. The 5G NR standards are set by the 3GPP. A UE uses channel state information reference signals (CSI-RS) to measure and feedback the characteristics of the radio channel so that the UE and gNB can use the correct modulation, code rate, beamforming, etc. for data transmission.

[0005] Mobile operators increasingly experience bandwidth shortage, which motivates the exploration of the underutilized millimeter wave (mmWave) spectrum between 3G and 300 GHz for the next generation of broadband cellular communication networks. The available spectrum in the mmWave band is 200 times that of the traditional cellular system. Millimeter wave wireless networks use narrow-beam directional communication, which can support data rates of several gigabits. In principle, a beam training mechanism including initial beam alignment and subsequent beam tracking ensures BS beam and user equipment (UE) beam alignment for data communication. In downlink (DL) based beam management (BM), the BS side provides the UE with the opportunity to measure the beamformed channels of different combinations of BS beams and UE beams. For example, the BS performs periodic beam sweeping using reference signals (RSs) carried on individual BS beams. The UE can collect beamformed channel states by using different UE beams and report the collected information to the BS.

[0006] The essence of beamforming technology is to create an interference effect between different antenna signals. The basic idea of analog beamforming is to control the phase of each transmitted signal using a phase shifter. Analog beamforming affects the gain of the antenna array, thereby improving coverage. The antenna gain caused by analog beamforming partially compensates for high mmWave path loss. Therefore, analog beamforming is essential for 5G mmWave frequencies. In digital beamforming, signals are precoded before being sent to analog radio frequency circuits. Digital beamforming improves cell throughput because the same physical resource block (PRB) can be used to transmit data to multiple users at the same time. Hybrid beamforming is a combination of analog and digital beamforming.

[0007] Carrier aggregation (CA) is a bandwidth expansion technology supported since the LTE-Advanced era, which can aggregate multiple component carriers (CCs) for simultaneous reception. For downlink and uplink data, the UE and BS use the same antenna (panel) to receive all CCs within the same frequency band, and the same beam is applied to all intra-band CCs. It is desirable to use multiple CCs for channel measurement to obtain the best beam so that better performance can be achieved by taking advantage of the wideband channel. SUMMARY

[0008] A method of Cross-CC beam management is presented. A transceiver obtains beam vectors using channel measurements of multiple CCs, so that better performance can be achieved by exploiting wideband channels. The transceiver derives beam vectors by using channel measurements of a selected set of CCs to which a carrier weight factor is applied. The transceiver derives beam vectors, e.g., the best beam, using beam management reference signals (BM-RS) of the selected set of CCs. In one embodiment, the carrier weight factor can be the number of BM-RS resource elements (REs) per CC. In another embodiment, the channel measurements can be signal to noise ratio / reference signal received power (SNR / RSRP), and the carrier weight factor can be the SNR / RSRP per CC.

[0009] In one embodiment, a first transceiver receives BM-RS transmitted from a second transceiver for reference signal measurements, where the first transceiver comprises an antenna array to which analog beamforming is applied. The first transceiver performs channel measurements for multiple CCs under carrier aggregation based on the received BM-RS. The first transceiver derives beam vectors from channel measurements on a selected set of CCs, where the beam vectors are obtained from channel measurements of the selected set of CCs to which a carrier weight factor of the respective CC is applied. The first transceiver applies the beam vectors in subsequent data reception or transmission.

[0010] Other embodiments and advantages are described in the following detailed description. This summary is not intended to define the invention. The invention is defined by the claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 A new NR mobile communication network for cross component carrier beam management and optimization is illustrated in accordance with one novel aspect.

[0012] Figure 2 is a simplified block diagram of a base station and user equipment implementing certain embodiments of the invention.

[0013] Figure 3 A sequence flow illustrating the overall procedure for channel measurement and cross CC beam management and optimization in accordance with one novel aspect.

[0014] Figure 4 is a flow chart of a method of cross CC channel measurement and beam optimization in accordance with one novel aspect. DETAILED DESCRIPTION

[0015] Reference will now be made in detail to some embodiments of the application, examples of which are illustrated in the accompanying drawings.

[0016] Figure 1 A new NR mobile communication network for cross-component carrier beam management and optimization is illustrated according to one novel aspect. The mobile communication network 100 is an OFDM network comprising a serving base station (gNB 101) and a user equipment (UE 102). In a 3GPP NR system based on OFDMA downlink, the radio resources are divided in time domain into multiple time slots, each consisting of multiple OFDM symbols. According to the system bandwidth, each OFDMA symbol also includes multiple OFDMA subcarriers in frequency domain. The basic unit of the resource grid is called RE, which spans one OFDMA subcarrier on one OFDMA symbol. Multiple REs are grouped into different physical resource blocks (PRBs), where each PRB consists of twelve consecutive subcarriers in one time slot.

[0017] Several physical downlink channels and reference signals are defined to use a set of resource elements that carry information originating from higher layers. For downlink channels, the physical downlink shared channel (PDSCH) is the main downlink channel in NR that carries data, while the physical downlink control channel (PDCCH) is used to carry downlink control information (DCI). The control information can include scheduling decisions, information related to reference signal information, rules to form the corresponding transport block (TB) to be carried by the PDSCH, and power control commands. For radio resource management (RRM) measurements in NR, each UE can be configured to measure synchronization signal (SS) blocks (SS blocks, SSBs) and / or channel state information (CSI) reference signals (CSI reference signals, CSI-RSs). For CSI-RS measurements, frequency and timing resources need to be determined. The UE can utilize the SSB / CSI-RS to measure the characteristics of the radio channel so that the UE can use the correct modulation, code rate, beamforming, etc. for DL data reception.

[0018] The essence of beamforming techniques is to create an interference effect between the signals emitted by different antennas. The basic idea of analog beamforming is to control the phase of each transmitted signal using a phase shifter. In digital beamforming, the signals are precoded before being sent to the analog RF circuitry. Hybrid beamforming is a combination of analog and digital beamforming, as shown in Figure 1 In downlink DL-based BM, the BS side provides the UE with an opportunity to measure the beamformed channels of different combinations of BS beams and UE beams. Based on the channel measurements, the Antenna Weight Vectors (AWVs) for analog beamforming and the precoding matrices for digital beamforming are calculated. In one embodiment, the channel covariance information can be used to design the transmitter precoder, the receiver combiner, the channel estimator, etc.

[0019] In the example of Figure 1 , the UE 102 is equipped with multiple RXUs (RF chains), and the UE 102 is also configured with carrier aggregation (CA). Typically, for downlink data, the UE 102 uses the same antenna (panel) to receive all CCs within the same frequency band, and the same AWV is applied to all intra-band CCs. However, the UE 102 can experience low signal to noise radio (SNR) performance and face misalignment of steering vectors between different RXUs. For example, assuming there is no inherent phase misalignment between two RXUs (e.g., RF chains 124 and 125), the AWVs (W RF ) of the two RXUs should be the same, as the angle of arrival (AoA) of the two RXUs is the same. However, if the received signal is weaker than the other RXU, one of the UE RXUs cannot train the AWV well. For example, if the received signal power of RXU0 is much smaller than that of RXU1, the AWV of RXU0 will be different from that of RXU1.

[0020] According to one novel aspect, the UE 102 uses channel measurements of multiple CCs to obtain the best beam, so that better performance can be achieved by exploiting the wideband channel. In Figure 1In a downlink example of gNB 101, the gNB 101 includes a digital precoder 111, an IFFT 112, an IFFT 113, RFs 114, RF chains 115, a plurality of phase shifters 116, and an antenna array 117. Similarly, the UE 102 includes a digital combiner 121, an FFT 122, an FFT 123, RF chains 124, RF chains 125, a plurality of phase shifters 126, and an antenna array 127. In DL-based BM, the gNB 101 transmits BM-RS to the UE 102. The BM-RS is precoded by digital precoding (111), by IFFT processing (112-113), by RF chain processing (114-115), by phase shifting (116), and transmitted from the antenna array (117) to the UE 102. On the UE side, the UE 102 receives the BM-RS from the antenna array 127 by phase shifting (126), RF chain processing (124-125), FFT processing (122-123), and digital combining (121) for additional processing.

[0021] In a novel aspect, upon receiving the BM-RS, the UE 102 considers channel measurements of the plurality of CCs to obtain a beam vector, e.g., the best beam (best UE RX AWV) (W RF ). The best UE RX AWV can then be used in subsequent DL data reception and / or uplink transmission to improve performance. More specifically, a carrier weight factor is applied to the channel quality of each of the CCs, and then the combined channel quality is used to derive the best W RF . Note that while the illustrated example is for DL beam management, it also applies to UL beam management, where the gNB 101 derives the best beam from the cross-CC channel measurements.

[0022] Figure 2 is a simplified block diagram of a base station 201 and a user equipment 211 performing certain embodiments of the present application in a mobile communication network 200. For the base station 201, an antenna 221 transmits and receives radio signals. An RF transceiver module 208 is coupled with the antenna to receive RF signals from the antenna, convert them to baseband signals and send them to a processor 203. The RF transceiver module 208 also converts received baseband signals from the processor to RF signals and sends them to the antenna 221. The processor 203 processes the received baseband signals and invokes different functional modules to perform features in the base station 201. The memory 202 includes volatile and non-volatile computer readable storage media, storing program instructions and data 209 to control the operation of the base station.

[0023] Similar configuration exists in the UE 211, where the antennas 231 transmit and receive RF signals. The RF transceiver module 218, coupled with the antennas, receives RF signals from the antennas, converts them to baseband signals and sends them to the processor 213. The RF transceiver 218 also converts received baseband signals from the processor to RF signals and sends them to the antennas 231. The processor 213 processes the received baseband signals and invokes different functional modules to perform features in the UE 211. The memory 212 includes volatile and non-volatile computer readable storage media, storing program instructions and data 219 to control the operation of the UE.

[0024] The base station 201 and the UE 211 also include several functional modules and circuits to perform some embodiments of the present application. Different functional modules are circuits that can be configured and implemented by software, firmware, hardware, or any combination thereof. The functional modules and circuits, when executed by the processors 203 and 213 (e.g., via executing program codes 209 and 219), for example, allow the base station 201 to schedule (via the scheduler 204), precode (via the beamforming circuit 205), encode (via the beam management circuit 206), and transmit control / configuration information and data (via the control / configuration circuit 207) to the UE 211, and allow the UE 211 to receive control / configuration information and data (via the control / configuration circuit 217), measure reference signals (via the measurement circuit 216), estimate channels (via the estimation circuit 215), and accordingly derive the best beam (via the beamforming circuit 220).

[0025] In one example, the BS 201 transmits BM-RS to the UE 211, which can be SSB, CSI-RS, CSI-RS for tracking (e.g., tracking reference signal (TRS)), PDSCH DMRS, or PUSCH DMRS (if transmitted from the UE 211 to the BS 201). Upon receiving the BM-RS, the UE 211 performs channel measurement via the measurement circuit 216, which utilizes the BM-RS of all intra-band CCs. The UE 211 then performs channel estimation via the estimation circuit 215 for all CCs. A carrier weighting factor is applied to combine the channel qualities of the respective CCs. The UE 211 then derives the best beam from the combined channel qualities via the beamforming circuit 220 for DL / UL data reception / transmission.

[0026] Figure 3A sequence flow of the whole procedure for channel measurement and cross-CC beam management and optimization according to one novel aspect is illustrated. In step 311, the first transceiver 1 performs BM by sending BM-RS to the second transceiver 2. The transceiver 2 is equipped with multiple antenna sub-arrays, multiple phase shifters (for analog beamforming), multiple RF chains (RXU) and one digital combining circuit (for digital beamforming) for data reception. The transceiver 2 is also configured with multiple CCs for data transmission under carrier aggregation (CA). In one example, the transceiver 1 is a base station, the transceiver 2 is a UE, and the beam management is downlink BM; in another example, the transceiver 1 is a UE, the transceiver 2 is a base station, and the beam management is uplink BM. The BM-RS can be SSB, CSI-RS, CSI-RS for tracking, Physical Downlink Shared Channel (PDSCH) Demodulation Reference Signal (DMRS), or Physical Uplink Shared Channel (PUSCH) DMRS.

[0027] In step 312, the transceiver 2 receives the BM-RS from the transceiver 1 and performs channel measurement and channel estimation accordingly. In one embodiment, the transceiver 2 scans the beam W RF,b with RX beam b on the i-th CC to receive signal R i , and calculates the beamformed channel quality M CC associated with one or several (N i,b ) received CCs.

[0028] M i,b = f1(W RF,b , R i )

[0029] wherein

[0030] i = 0, 1, …, N CC - 1 is the index of CC

[0031] b = 0, 1, …, N Beam - 1 is the index of RX beam

[0032] N CC is the total number of CCs under CA

[0033] N Beam is the total number of RX beams

[0034] In step 313, transceiver 2 selects multiple CCs for beam management and optimization calculations based on certain criteria. For example, these criteria may include at least one of CCs with smaller index values, CCs with better or weaker channel quality (based on SNR / RSRP), and CCs with greater uplink and downlink (UL / DL) intersection. Note that the order of steps 312 and 313 can be reversed, especially if the CC selection criteria do not depend on channel measurements.

[0035] In step 314, transceiver 2 obtains beamforming channel quality M from a selected number of CCs. combine Deriving (e.g., based on function f3) beam vectors, such as the optimal beam W RF,opt And W RF,opt It is the carrier weighting factor a i and beamforming channel quality M i,b The function (f2):

[0036]

[0037] W RF,opt =f3(M combine )

[0038] in

[0039] M i,b The beamforming channel quality of the RX beam b on the i-th CC

[0040] a i It is the carrier weighting factor of the i-th CC.

[0041] M combine The beamforming channel quality on a selected number of CCs

[0042] Channel quality M i,bis determined based on channel measurements. In a first example, the channel measurements on the CC are associated with an indicator of channel quality with respect to the CC. In a second example, the channel measurements on the CC are based on at least one of: signal to noise ratio (SNR), reference signal received power (RSRP), signal-to-noise and interference (SINR), throughput, bit error rate, block error rate, interference power, noise power, beamforming gain, mutual information, receive signal strength indicator (RSSI), reference signal received quality (RSRQ), received signal code power (RSCP) of the corresponding CC.

[0043] CC i The carrier weight factor (a i ) can be a function of one or more of: the number of received BM-RS REs of the ith CC (N_(N RE,i ), the number of received PDSCH DMRS REs of the ith CC, the SNR of the ith CC, the RSRP of the ith CC, and any other indicator related to the channel quality of the ith CC. In step 315, the transceiver 2 applies the beam vector, e.g., the best beam W RF,opt for the subsequent DL data reception and / or UL data transmission.

[0044] Note that traditionally, the carrier weight factor is proportional to the maximum PDSCH bandwidth of each corresponding CC, which is in favor of the CC with larger PDSCH bandwidth. However, if the UE sees RXU imbalance from the CC with larger PDSCH bandwidth, such design is still in favor of the CC with larger bandwidth. According to one novel aspect, the proposed carrier weight factor is proportional to the number of BM RS REs of each corresponding CC. In Figure 3 the example, the carrier weight factor is equal to where N RE,i is the number of BM RS REs of the ith CC, ) is the total number of BM-RS REs.

[0045] In one embodiment, according to a novel aspect, the best beam, e.g., AWV, can be obtained using BM-RS for data reception and transmission. In a 3GPP NR system based on OFDMA downlink, radio resources are divided into multiple slots in time domain, each of which consists of multiple OFDM symbols. According to the system bandwidth, each OFDMA symbol also includes multiple OFDMA subcarriers in frequency domain. For downlink channels, PDSCH is the main downlink channel carrying data in NR, while PDCCH is used to carry downlink control information. For radio resource management (RRM) measurement, the UE is configured to measure SSB and / or CSI-RS. For DL-based BM, the BS side provides the UE with the opportunity to measure beamformed channels of different combinations of BS beams and UE beams.

[0046] In one example of DL beam management, the gNB transmits BM-RS in a pre-defined OFDM symbol in slot n. Upon receiving the BM-RS, the UE obtains the best UE RX AWV (W RF,opt ) considering channel measurements of multiple CCs. The best UE RX AWV can then be used in subsequent DL data reception to improve performance. For example, W RF,opt may be used by the UE for analog beamforming for downlink data reception in slot n+X, slot n+X+1, etc. More specifically, a carrier weight factor proportional to the number of BM-RS REs of the corresponding CC is applied to the measured channel quality, and then the best W RF,opt is derived using it. Similar examples can be applied to uplink beam management.

[0047] Figure 4 is a flowchart of a method of cross-CC channel measurement and beam optimization according to a novel aspect. In step 401, a first transceiver receives a BM-RS transmitted from a second transceiver for reference signal measurement, wherein the first transceiver comprises an antenna array applying analog beamforming. In step 402, the first transceiver performs channel measurement for multiple CCs under carrier aggregation based on the received BM-RS. In step 403, the first transceiver derives a beam vector from channel measurements on a set of selected CCs, wherein the beam vector is obtained from channel measurements of the set of selected CCs applying a carrier weight factor of the corresponding CC. In step 404, the first transceiver applies the beam vector in subsequent data reception or transmission.

[0048] While the application has been described in connection with certain specific embodiments thereof, it will be understood that it is carried out in practice not limited to them. It being thus within the scope of the application as set forth in the following claims, the various characteristics described can be practiced separately or in combination and the application is therefore to be considered in its broadest and genuine sense.

Claims

1. A method of cross-component carrier beam management, comprising: receiving, by a first transceiver, a beam management reference signal (BM-RS) transmitted from a second transceiver for reference signal measurement, wherein the first transceiver comprises an antenna array with applied analog beamforming; performing channel measurement on a plurality of component carriers (CCs) under carrier aggregation based on the received BM-RS; deriving a beam vector from the channel measurement on a set of selected CCs, wherein the beam vector is obtained from the channel measurement of the set of selected CCs with applied carrier weight factors of the respective CCs; and applying the beam vector in subsequent data reception or transmission of the first transceiver.

2. The method of claim 1, wherein, the BM-RS is one of a synchronization signal block (SSB), a channel state information reference signal (CSI-RS), a CSI-RS for tracking, a physical downlink shared channel (PDSCH) demodulation reference signal (DMRS), and a physical uplink shared channel (PUSCH) DMRS.

3. The method of claim 1, wherein, the set of selected CCs is based on at least one of criteria comprising a CC index, a CC channel quality, and an intersection of uplink or downlink (UL / DL) CCs.

4. The method of claim 1, wherein, the channel measurement on a CC is associated with an indicator on channel quality of the CC.

5. The method of claim 1, wherein, the channel measurement on a CC is based on at least one of a signal-to-noise ratio (SNR), a reference signal received power (RSRP), a signal-to-noise-and-interference (SINR), a throughput, a bit error rate, a block error rate, an interference power, a noise power, a beamforming gain, a mutual information, a received signal strength indicator (RSSI), a reference signal received quality (RSRQ), and a received signal code power (RSCP).

6. The method of claim 1, wherein, the carrier weight factor of a respective CC is based on a number of received BM-RS resource elements (REs) of the respective CC.

7. The method of claim 1, wherein, the carrier weight factor of a respective CC is based on a number of received physical downlink shared channel (PDSCH) demodulation reference signal (DMRS) resource elements (REs) of the respective CC.

8. The method of claim 1, wherein, the carrier weight factor of a respective CC is based on a signal-to-noise ratio (SNR) or a reference signal received power (RSRP) of the respective CC.

9. The method of claim 1, wherein, the carrier weight factor of a respective CC is based on an indicator related to channel quality of the respective CC.

10. The method of claim 1, wherein, the beam vector is an antenna weight vector (AWV) applied to the antenna array. 11.A device of cross-component carrier beam management, comprising: a first transceiver configured to receive a beam management reference signal (BM-RS) transmitted from a second transceiver for reference signal measurement, wherein the first transceiver comprises an antenna array with applied analog beamforming; a channel measurement circuit configured to perform channel measurement on a plurality of component carriers (CCs) under carrier aggregation based on the received BM-RS; a beamforming circuit configured to derive a beam vector from the channel measurement on a set of selected CCs, wherein the beam vector is obtained from the channel measurement of the set of selected CCs with applied carrier weight factors of the respective CCs; and an antenna array, the beam vector being applied in a subsequent data reception or transmission of the first transceiver.

12. The cross-component carrier beam management device of claim 11, wherein, The BM-RS is one of a synchronization signal block (SSB), a channel state information reference signal (CSI-RS), a CSI-RS for tracking, a physical downlink shared channel (PDSCH) demodulation reference signal (DMRS), and a physical uplink shared channel (PUSCH) DMRS.

13. The cross-component carrier beam management device of claim 11, wherein, The set of selected CCs is based on at least one of criteria comprising a CC index, a CC channel quality, and an intersection of uplink or downlink (UL / DL) CCs.

14. The cross-component carrier beam management device of claim 11, wherein, The channel measurement on a CC is associated with an indicator related to a channel quality of the CC.

15. The cross-component carrier beam management device of claim 11, wherein, The channel measurement on a CC is based on at least one of a signal-to-noise ratio (SNR), a reference signal received power (RSRP), a signal-to-noise-and-interference (SINR), a throughput, a bit error rate, a block error rate, an interference power, a noise power, a beamforming gain, a mutual information, a received signal strength indicator (RSSI), a reference signal received quality (RSRQ), and a received signal code power (RSCP).

16. The cross-component carrier beam management device of claim 11, wherein, The carrier weight factor of a respective CC is based on a number of received BM-RS resource elements (REs) of the respective CC.

17. The cross-component carrier beam management device of claim 11, wherein, The carrier weight factor of a respective CC is based on a number of received physical downlink shared channel (PDSCH) demodulation reference signal (DMRS) resource elements (REs) of the respective CC.

18. The cross-component carrier beam management device of claim 11, wherein, The carrier weight factor of a respective CC is based on a signal-to-noise ratio (SNR) or a reference signal received power (RSRP) of the respective CC. 19.The cross-component carrier beam management device of claim 11, wherein, The carrier weight factor of a respective CC is based on an indicator related to a channel quality of the respective CC. 20.The cross-component carrier beam management device of claim 11, wherein, The beam vector is an antenna weight vector (AWV) applied to the antenna array.

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