CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. §119 from U.S. Provisional Application Number 63/061,818, entitled "Method and Apparatus for a UE with Multiple Panels," filed on August 6, 2020, the subject matter of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The disclosed embodiments relate generally to wireless communication, and, more particularly, to resource configuration for UEs with multiple panels in a next generation new radio (NR) cellular system.

BACKGROUND

[0003] The wireless communications network has grown exponentially over the years. A Long-Term Evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simplified network architecture. LTE systems, also known as the 4G system, also provide seamless integration to older wireless network, such as GSM, CDMA and Universal Mobile Telecommunication System (UMTS) . In LTE systems, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNodeBs or eNBs) communicating with a plurality of mobile stations, referred to as User Equipments (UEs ) . The 3 ^rd generation partner proj ect ( 3GPP ) network normally includes a hybrid of 2G/ 3G/ 4G systems . The Next Generation Mobile Network (NGMN) board, has decided to focus the future NGMN activities on defining the end-to-end requirements for 5G New Radio (NR) systems . The base stations in 5G NR are referred to as gNBs .

[ 0004 ] The bandwidth shortage increasingly experienced by mobile carriers has motivated the exploration of the underutili zed Millimeter Wave (mmWave ) frequency spectrum between 3G and 300G Hz for the next generation broadband cellular communication networks . The available spectrum of mmWave band is two hundred times greater than the conventional cellular system . The mmWave wireless network uses directional communications with narrow beams and can support multi-gigabit data rate . The underutili zed bandwidth of the mmWave spectrum has wavelengths ranging from 1mm to 100mm . The very small wavelengths of the mmWave spectrum enable large number of miniaturi zed antennas to be placed in a small area . Such miniaturi zed antenna system can produce high beamforming gains through electrically steerable arrays generating directional transmissions .

[ 0005 ] In principle , beam training mechanism, which includes both initial beam alignment and subsequent beam tracking, ensures that base station (BS ) beam and user equipment (UE ) beam are aligned for data communication . In downlink DL-based beam management (BM) , the BS side provides opportunities for UE to measure beamformed channel of different combinations of BS beams and UE beams. For example, BS performs periodic beam sweeping with reference signal (RS) carried on individual BS beams. UE can collect beamformed channel state by using different UE beams and report the collect information to BS . Similarly, in uplink UL-based BM, the UE side provides opportunities for BS to measure beamformed channel of different combinations of UE beams and BS beams. For example, the UE performs periodic beam sweeping with reference signal (RS) carried on individual UE beams. BS can collect beamformed channel state by using different BS beams and report the collect information to the UE .

[0006] In LTE TDD system or 5G NR system, the gNB uses the sounding reference signal (SRS) transmitted by the UE in the uplink (UL) in order to get downlink (DL) channel state information (CSI) thanks to channel reciprocity. DL CSI acquisition thus involves SRS resource configuration for the corresponding SRS transmission. For example, in 5G NR, the UE is configured with the higher layer parameter usage in SRS -ResourceSet set as 'antennaSwitching' for DL CSI acquisition. Up to two SRS resource sets can be configured and each set has one SRS resource with multiple ports. The UE is configured with a guard period of 1~2 symbols, in which the UE does not transmit any other signal, in case the SRS resources of a set are transmitted in the same slot. However, this doesn't consider the UE with multiple panels because the UE may require the additional delay for antenna switching in case one panel is deactivated by UE's own decision (e.g. power saving) .

[0007] A solution is sought to provide proper SRS configuration to UEs with multiple panels for DL CSI acquisition .

SUMMARY

[0008] A method of configuring uplink sounding reference signal (SRS) resource for UEs with multiple panels for downlink channel state information (CSI) acquisition in a cellular communication network is proposed. A UE with multiple panels reports its antenna capability to a base station. The antenna capability comprises a number of UE panels and a minimum guard period for panel switching. In response, the UE receives SRS resource configuration from the base station. The SRS resource configuration allocates SRS resources with a guard period for panel switching. The UE then performs uplink SRS transmission accordingly. The base station measures UL SRSs and obtains DL CSI using the UL SRS measurement results.

[0009] In one embodiment, a UE transmits antenna capability of the UE to a base station in a cellular mobile communication network. The antenna capability comprises a number of UE panels and a minimum guard period for panel switching. The UE receives a sounding reference signal (SRS) resource configuration for SRS transmission. The SRS resource configuration comprises at least one SRS resource set with allocated resources and a guard period for panel switching based on the UE antenna capability . The UE performs SRS transmission to the base station using the allocated SRS resource set and the corresponding guard period for panel switching . In one embodiment , the minimum guard period is represented by a minimum number of OFDM symbols between two SRS resources of the SRS resource set , and the allocated guard period is represented by one or more variables indicative of the minimum number of OFDM symbols . [ 0010 ] In another embodiment , a gNB receives antenna capability of a UE from the UE in a cellular mobile communication network . The antenna capability comprises a number of UE panels and a minimum guard period symbols for panel switching . The gNB transmits a sounding reference signal ( SRS ) resource configuration to the UE . The SRS resource configuration comprises at least one SRS resource set with allocated resources and a guard period for panel switching based on the UE antenna capability . The gNB receives SRSs transmitted from the UE using the allocated SRS resource set and the corresponding guard period for panel switching . The gNB obtains downlink channel state information ( CS I ) based on SRS measurements . In one embodiment , the minimum guard period is represented by a minimum number of OFDM symbols between two SRS resources of the SRS resource set , and the allocated guard period is represented by one or more variables indicative of the minimum number of OFDM symbols .

[ 0011 ] Other embodiments and advantages are described in the detailed description below . This summary does not purport to define the invention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention .

[0013] Figure 1 illustrates downlink (DL) channel state information (CSI) acquisition in a 5G new radio (NR) wireless communication system for UEs supporting multiple panels in accordance with one novel aspect.

[0014] Figure 2 is a simplified block diagram of a base station and a user equipment that carry out certain embodiments of the present invention.

[0015] Figure 3 illustrates a procedure for downlink (DL) channel state information (CSI) acquisition with UE antenna capability signaling and panel activation/deactivation in accordance with one novel aspect.

[0016] Figure 4 illustrates one embodiment of UE antenna capability signaling and UL SRS resource configuration in accordance with one novel aspect.

[0017] Figure 5 is a flow chart of a method of configuring uplink reference resource for UEs with multiple panels for downlink CSI acquisition from UE perspective in a cellular communication network in accordance with one novel aspect.

[0018] Figure 6 is a flow chart of a method of configuring uplink reference resource for UEs with multiple panels for downlink CSI acquisition from BS perspective in a cellular communication network in accordance with one novel aspect.

DETAILED DESCRIPTION

[0019] Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

[0020] Figure 1 illustrates downlink (DL) channel state information (CSI) acquisition in a 5G new radio (NR) wireless communication system for UEs supporting multiple panels in accordance with one novel aspect. 5G NR cellular communication network 100 comprises a base station BS/gNB 101 and a user equipment UE 102. The cellular network 100 uses directional communication with narrow beams and can support multi-gigabit data rate. Directional communication is achieved via digital and/or analog beamforming, wherein multiple antenna elements are applied with multiple sets of beamforming weights to form multiple beams. Different beamformers can have different spatial resolution, i.e., beamwidth. For example, a sector antenna can form beams having lower array gain but wider spatial coverage, while a beamforming antenna can have higher array gain but narrower spatial coverage.

[0021] The purpose of downlink (DL) and uplink (UL) beam training is to decide a proper beam pair link (BBL) between a BS and a UE for communication. In uplink UL-based beam management, the UE side provides opportunities for BS to measure beamformed channel of different combinations of UE beams and BS beams. For example, UE performs periodic beam sweeping with reference signal (RS) carried on individual UE beams. BS can collect beamformed channel state by using different BS beams and report the collected information to UE . In LTE TDD system or 5G NR system, the gNB uses the sounding reference signal (SRS) transmitted by the UE in the UL in order to get DL channel state information (CSI) thanks to channel reciprocity. DL CSI acquisition thus involves SRS resource configuration for the corresponding SRS transmission .

[0022] In the example of Figure 1, gNB 101 provides UL SRS resource configuration to UE 102 for CSI acquisition. UE 102 then transmits UL SRS using different UE TX beams over the configured UL SRS resources. gNB 101 performs measurements and obtains corresponding DL CSI based on the UL SRS measurement results. As depicted by 110, in 5G NR, UE 102 is configured with the higher layer parameter usage in SRS -ResourceSet set as 'antennaSwitching' for DL CSI acquisition. Up to two SRS resource sets can be configured and each set has one SRS resource with multiple ports. The UE is configured with a guard period of 1~2 symbols, in which the UE does not transmit any other signal, in case the SRS resources of a set are transmitted in the same slot and antenna switching is needed. However, this doesn't consider the UE with multiple panels, e.g., each panel comprises a group of antennas. For a UE with multiple panels, the UE may require the additional delay for antenna switching in case one panel is deactivated by UE's own decision (e.g. power saving) . As a result, the guard period for 'panel switching' may need to be longer than the guard period configured as 'antennaSwitching' for DL CSI acquisition. [0023] In Figure 1, gNB 101 has two transmission points (TRP1 and TRP2) and ten TX beams, beams #1-5 are transmitted from TRP1, and beams #6-10 are transmitted from TRP2. UE 102 has three panels (#1, #2, and #3) . In according with one novel aspect, in step 111, UE 102 provides its antenna capability signaling to gNB 101 to facilitate the SRS resource configuration. From UE perspective, UE 102 needs to report the number of panels and the minimum guard period symbols for panel switching as UE capability. In step 112, when BS determines SRS resources, gNB 101 allocates each SRS resource set configuration using the minimum guard period symbols reported by UE 102. As depicted by 110, UE 102 is configured with the higher layer parameter usage in SRS- ResourceSet set as 'antennaSwitching' or 'panelswitching' for DL CSI acquisition. In addition, a new MAC CE is introduced to activate and deactivate, by the gNB, panel (s) of the UE .

[0024] Figure 2 is a simplified block diagram of a base station and a user equipment that carry out certain embodiments of the present invention. BS 201 has one or more antenna/panel 211 having multiple antenna elements that transmits and receives radio signals, one or more RF transceiver modules 212, coupled with the antenna, receives RF signals from antenna 211, converts them to baseband signal, and sends them to processor 213. RF transceiver 212 also converts received baseband signals from processor 213, converts them to RF signals, and sends out to antenna 211. Processor 213 processes the received baseband signals and invokes different functional modules to perform features in BS 201. Memory 214 stores program instructions and data 215 to control the operations of BS 201. BS 201 also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention.

[0025] Similarly, UE 202 has one or more antenna/panel 231, which transmits and receives radio signals. A RF transceiver module 232, coupled with the antenna, receives RF signals from antenna 231, converts them to baseband signals and sends them to processor 233. RF transceiver 232 also converts received baseband signals from processor 233, converts them to RF signals, and sends out to antenna 231. Processor 233 processes the received baseband signals and invokes different functional modules to perform features in UE 202. Memory 234 stores program instructions and data 235 to control the operations of UE 202. UE 202 also includes multiple function modules and circuits that carry out different tasks in accordance with embodiments of the current invention.

[0026] The functional modules and circuits can be implemented and configured by hardware, firmware, software, and any combination thereof. For example, BS 201 comprises a beam management module 220, which further comprises a beamforming circuit 221, a beam monitor 222, a resource allocation circuit 223, and a beam management control circuit 224 . Beamforming circuit 221 may belong to part of the RF chain, which applies various beamforming weights to multiple antenna elements of antenna 211 and thereby forming various beams . Beam monitor 222 monitors received radio signals and performs measurements of the radio signals transmitted over the various UE beams . Resource allocation circuit 223 allocates RS resource sets based on reported UE antenna capability, configures and triggers di f ferent UL BM procedures , and beam management control circuit 224 controls DL and UL beam management to determine BBL and to obtain DL CS I .

[ 0027 ] Similarly, UE 202 comprises a beam management module 240 , which further comprises a beamforming circuit 241 , a beam monitor 242 , a beam grouping circuit 243 , and an SRS handling circuit 244 . Beamforming circuit 241 may belong to part of the RF chain, which applies various beamforming weights to multiple antenna elements of antenna 231 and thereby forming various beams . Beam monitor 242 monitors received radio signals and performs measurements of the radio signals over the various beams . Beam grouping and antenna/panel switching circuit groups di f ferent BS beams into beam groups based on RS resource configuration, and performs antenna/panel switching accordingly . SRS handling circuit 244 performs SRS transmission used the allocated SRS resource set ( s ) . Overall , beam management circuit 240 performs UL beam training and management procedures to provide UE antenna capability, to transmit reference signals over configured SRS resources over di f ferent UE beams , and to enable BS to activate or inactivate one or more panels for power saving.

[0028] Figure 3 illustrates a procedure for downlink (DL) channel state information (CSI) acquisition with UE antenna capability signaling and panel activation/deactivation in accordance with one novel aspect. Initially, UE 302 performs scanning, beam selection, and synchronization with BS 301 using periodically configured control beams. In step 311, UE 302 provides UE antenna capability signaling to BS 301. For example, the antenna capability information may comprise a number of required UL RS resource groups, i.e., a number of UE antenna groups or panels, a number of UE beams per group, and beam correspondence state. In one novel aspect, the antenna capability information comprises a number of UE antenna panels, and the minimum guard period symbols for the purpose of performing panel switching during UL SRS transmission.

[0029] In step 321, BS 301 provides UL SRS resource configuration to UE 302 based on the UE antenna capability. The SRS resource configuration comprises a guard period for panel switching used for UL SRS transmission for DL CSI measurement, determined based on the minimum guard period symbols reported by the UE . In step 331, UE 302 periodically transmits UL SRS to BS 301 using different UE beams over the configured UL SRS resources. Because the guard period is configured based on UE capability with multiple panels, UE 302 is guaranteed to have enough time to perform antenna panel switching in case one panel is deactivated. Based on the UL SRS transmission, BS 301 recursively monitors and measures the UE beams for its RSRP and/or DL CSI metric (step 341) . In step 351, BS 301 activates or deactivates one or more UE panel (s) using a newly defined MAC CE .

[0030] Figure 4 illustrates one embodiment of providing UE antenna capability signaling and receiving UL SRS resource configuration in accordance with one novel aspect. In the example of Figure 4, UE 401 is equipped with three panels: panel A, panel B, and panel C, each panel comprises a number of antennas/beams for transmission and reception. For example, panel A comprises antenna/beam #l-#3, panel B comprises antenna/beam #4-5, and panel C comprises antenna/beam #6-8. In general, the UE can receive downlink data using multiple panels simultaneously. This can be supported by group-based reporting, where the UE reports the beam indexes (such as QCL-TypeD RS) that can be received simultaneously. In NR, more operations can be supported for UE's multiple panel transmission and reception, e.g., applying panel switching in uplink transmission, and panelspecific power control and timing advance command.

[0031] In 5G NR, the UE is configured with higher layer parameters in SRS resource configuration for DL CSI acquisition. Up to two SRS resource sets can be configured and each set has one SRS resource with multiple ports. For each SRS resource set, the UE is configured with a guard period of 1~2 OFDM symbols, in which the UE does not transmit any other signal. This is because if the SRS resources of a set are transmitted in the same slot , then the guard period makes sure that the UE can have enough time to perform antenna switching for the corresponding SRS transmission . Figure 4 table 410 depicts the guard period (Y symbols ) between two SRS resources of an SRS resource set for antenna switching, where // is the subcarrier spacing configuration defined in 3GPP NR . However, this doesn' t consider the UE with multiple panels because the UE may require the additional delay for antenna switching in case one panel is deactivated by UE ' s own decision ( e . g . for power saving purpose ) .

[ 0032 ] In according with one novel aspect , UE 401 reports to its serving gNB the number of panels and the minimum guard period Z OFDM symbols for panel switching by UE capability, and the gNB allocates each SRS resource set with the reported guard period Z for panel switching used for DL CS I measurement . In a preferred embodiment , each SRS resource set configuration comprises a resource set ID, a resource list , a resource type , and a usage . The parameter usage in SRS -ResourceSet set can be set as ' antennaSwitching' or can be set as 'panelswitching' , for DL CS I acquisition for UEs equipped with single panel or multiple panels , respectively, based on the reported UE capability .

[ 0033 ] In other words , the UE is configured, via higher layer, with a guard period of Y or Z symbols , in which the UE does not transmit any other signal , in case the SRS resources of a set are transmitted in the same slot , and Y or Z symbols are determined by whether the UE has a single panel (corresponds to Y symbols) or multiple panels

(corresponds to Z symbols) . If the UE has single panel, then the usage of the SRS resource set configuration is set as 'antennaSwitching' . If the UE has multiple panels, then the usage of the SRS resource set configuration is set as 'panelSwitching' , and the UE is configured with a guard period that can satisfy the reported minimum guard period Z symbols. In one example, if the reported minimum guard period Z for panel switching is Z=4 OFDM symbols for SCS=15kHz, then the RRC parameter usage in SRS-ResourceSet can be set as 'panelSwitching' and a variable a=4 OFDM symbol can be configured. The UE can derive the minimum guard period Z=a, a, a, 2a OFDM symbol for different SOS = 15, 30, 60, and 120kHz, respectively.

[0034] Figure 5 is a flow chart of a method of configuring uplink reference resource for UEs with multiple panels for downlink CSI acquisition from UE perspective in a cellular communication network in accordance with one novel aspect. In step 501, a UE transmits antenna capability of the UE to a base station in a cellular mobile communication network. The antenna capability comprises a number of UE panels and a minimum guard period for panel switching. In step 502, the UE receives a sounding reference signal (SRS) resource configuration for SRS transmission. The SRS resource configuration comprises at least one SRS resource set with allocated resources and a guard period for panel switching based on the UE antenna capability. In step 503, the UE performs SRS transmission to the base station using the allocated SRS resource set and the corresponding guard period for panel switching . In one embodiment , the minimum guard period is represented by a minimum number of OFDM symbols between two SRS resources of the SRS resource set , and the allocated guard period is represented by one or more variables indicative of the minimum number of OFDM symbols . [ 0035 ] Figure 6 is a flow chart of a method of configuring uplink reference resource for UEs with multiple panels for downlink CS I acquisition from BS perspective in a cellular communication network in accordance with one novel aspect . In step 601 , a gNB receives antenna capability of a UE from the UE in a cellular mobile communication network . The antenna capability comprises a number of UE panels and a minimum guard period symbols for panel switching . In step 602 , the gNB transmits a sounding reference signal ( SRS ) resource configuration to the UE . The SRS resource configuration comprises at least one SRS resource set with allocated resources and a guard period for panel switching based on the UE antenna capability . In step 603 , the gNB receives SRSs transmitted from the UE using the allocated SRS resource set and the corresponding guard period for panel switching . In step 604 , the gNB obtains downlink channel state information ( CS I ) based on SRS measurements . In one embodiment , the minimum guard period is represented by a minimum number of OFDM symbols between two SRS resources of the SRS resource set , and the allocated guard period is represented by one or more variables indicative of the minimum number of OFDM symbols .

[ 0036 ] Although the present invention has been described in connection with certain speci fic embodiments for instructional purposes , the present invention is not limited thereto . Accordingly, various modi fications , adaptations , and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims .