Channel state information measurement and calculation method and related user equipment

Abstract

A method of downlink channel state information (DL CSI) computation and reporting is proposed to support high speed scenarios in new radio (NR) systems. In a first novel aspect, two CSI reference slots are defined. A CSI reference slot for CSI measurement is defined to determine which CSI-RS / SSB occasion to use for CSI computation. A CSI reference slot for CSI computation is defined to determine a slot where the UE assumes that CSI computation should be based on the channel of that slot and onwards. In a second novel aspect, a UE can be configured with a CSI computation period consisting of one or N slots and can be divided into multiple non-overlapping sub-periods. The UE can be configured to compute and report wideband CSI for the entire CSI computation period and / or subband CSI for each sub-period.

Description

[0001] CROSS-REFERENCE

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 218,438, filed July 5, 2021, entitled “Extension of CSI Framework to Support High Mobility,” which is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The disclosed embodiments relate generally to mobile communication networks, and more specifically to a method for channel state information (CSI) computation to support high speed scenarios. 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 radio access network includes a plurality of base stations (BSs), referred to as next generation NodeBs (gNBs), in communication with a plurality of mobile stations, referred to as user equipment (UEs). The UEs can communicate with the base stations (BSs) or gNBs through the downlink and uplink. The downlink (DL) refers to the communication from the base station to the UE. The uplink (UL) refers to the communication from the UE to the base station. The 5G NR standards are set by 3GPP. The UEs use channel state information reference signals (CSI-RS) to measure and feedback the characteristics of the radio channel so that the gNB can use the correct modulation, code rate, beamforming, etc. for DL data transmission.

[0005] In real development, it is observed that the throughput drops significantly in high or medium speed scenarios. One major reason is that the reported CSI becomes outdated due to the fast channel variation. The channel variation can be observed in the Doppler domain. In current NR, the CSI is computed based on the slot where the CSI reference resource is located, which is before the uplink slot where the CSI is reported. When the gNB needs to perform scheduling, the CSI computed for the past slot can not be useful later, especially in high speed scenarios. To improve the throughput, the gNB needs to know the CSI that is beneficial for the “future” channel. The future CSI cannot be learned by “one-shot” measurement because any channel variation needs at least two measurements to be detected.

[0006] A solution is sought to extend the CSI framework in NR to support high speed scenarios. SUMMARY

[0007] A downlink channel state information (DL CSI) computation and reporting method is proposed to support high speed scenarios in new radio (NR) systems. In a first novel aspect, two CSI reference slots are defined. A CSI reference slot for CSI measurement is defined to determine which CSI-RS / SSB occasion to use for computing CSI. A CSI reference slot for CSI computation is defined to determine a slot from which the UE assumes that the CSI computation should be based on the channel from that slot onwards. In a second novel aspect, a UE can be configured with a CSI computation period consisting of one or N slots and can be divided into multiple non-overlapping sub-periods. The UE can be configured to compute and report wideband and subband CSI for the entire CSI computation period and / or for each sub-period.

[0008] In one embodiment, a UE receives channel state information reference signal (CSI-RS) configuration information from a base station (BS). The UE determines a first CSI reference slot for measurement and a second CSI reference slot for computation according to the CSI-RS configuration information. The second CSI reference slot occurs after the first CSI reference slot in the time domain. The UE measures CSI reference signals (CSI-RS) of a downlink channel received before the first CSI reference slot for measurement. The UE computes CSI of the downlink channel according to the second CSI reference slot for computation. The UE estimates and predicts the CSI of the downlink channel starting from the second CSI reference slot for computation.

[0009] In another embodiment, a UE receives channel state information reference signal (CSI-RS) configuration information from a base station (gNB). The CSI-RS configuration includes CSI-RS resources and a CSI computation period with one or more non-overlapping sub-periods within the CSI computation period in the time domain. The UE measures multiple occasions of CSI-RS of a downlink channel received through the configured CSI-RS resources. The UE uses the timing correlation of the multiple CSI-RS occasions to estimate the CSI of the downlink channel for the CSI computation period. The UE reports the estimated CSI of the downlink channel to the gNB and reports the estimated CSI according to the configured CSI computation period.

[0010] This application provides a CSI measurement and computation method and apparatus that is beneficial for “future” channels under high speed scenarios in extended NR, 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] FIG. 1 A new radio (NR) mobile communication network with channel state information reference signal (CSI-RS) measurement, computation, and reporting for high speed scenarios is illustrated according to one novel aspect.

[0012] FIG. 2 is a simplified block diagram of a base station and user equipment that perform certain embodiments of the present application.

[0013] FIG. 3 illustrates a sequence flow of the overall procedure for CSI acquisition and reporting according to one novel aspect.

[0014] FIG. 4 shows a first embodiment of applying CSI reference slots for measurement and CSI reference slots for computation to support high speed scenarios according to one novel aspect.

[0015] FIG. 5 illustrates a second embodiment of configuring CSI computation period with full period CSI and sub-period CSI to support high speed scenarios according to one novel aspect.

[0016] FIG. 6 illustrates an example of CSI computation period with full period CSI and sub-period CSI for wideband and subband.

[0017] FIG. 7 illustrates an example of CSI computation and reporting to support high speed scenarios according to one novel aspect.

[0018] FIG. 8 is a flow chart of a method of applying CSI reference slots for measurement and CSI reference slots for computation to support high speed scenarios according to one novel aspect.

[0019] FIG. 9 is a flow chart of a method of configuring CSI computation period from UE perspective to support high speed scenarios according to one novel aspect. DETAILED DESCRIPTION

[0020] Reference will now be made in detail to some embodiments of the application, examples of which are illustrated in the accompanying drawings.

[0021] FIG. 1A new radio (NR) mobile communication network 100 with high speed channel state information reference signal (CSI-RS) measurement, computation and reporting 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, wireless resources are divided into multiple time slots in time domain, each time slot consisting of multiple OFDM symbols. Each OFDMA symbol is further composed of multiple OFDMA subcarriers in frequency domain, depending on the system bandwidth. The basic unit of the resource grid is called a resource element (RE), which spans one OFDMA subcarrier on one OFDMA symbol. REs are grouped into resource blocks (RBs), where each RB consists of twelve consecutive subcarriers in one time slot.

[0022] Several physical downlink channels and reference signals are defined to carry information originating from higher layers using a set of resource elements. For downlink channels, the physical downlink shared channel (PDSCH) is the main downlink channel in NR to carry data, while the physical downlink control channel (PDCCH) is used to carry downlink control information (DCI). Control information can include scheduling decisions, information related to reference signal information, rules to form corresponding transport blocks (TBs) to be carried by PDSCH, and power control commands. For radio resource management (RRM) measurements in NR, each UE can be configured to measure synchronization signal (SS) blocks (SSB) and / or channel state information (CSI) reference signals (CSI-RS). For CSI-RS measurements, frequency and time resources need to be determined. UEs use CSI-RS to measure and feedback the characteristics of the DL channel so that the gNB can use the correct modulation, code rate, beamforming, etc. for DL data transmission.

[0023] In actual development, it is observed that the throughput drops significantly in high or medium speed scenarios. One major reason is that the reported CSI becomes outdated due to fast channel variations. According to one novel aspect, as FIG. 1CSI acquisition and reporting are proposed to support high speed scenarios. In a novel aspect, two CSI reference slots are defined. A CSI reference slot for CSI measurement is defined to determine which CSI-RS / SSB occasion to use for calculating CSI. A CSI reference slot for CSI computation is defined to determine the first slot that the UE assumes that CSI computation should be based on the channel starting from that slot. For example, if CSI reporting occurs in slot (n), the CSI reference slot for CSI measurement occurs in slot (n-nCSI_REF), while the CSI reference slot for computation occurs in slot (n+K). In another novel aspect, a UE can be configured with a CSI computation period consisting of one or N slots, and can be divided into multiple non-overlapping sub-periods. The UE can be configured to compute and report wideband and subband CSI for the entire CSI computation period and / or each sub-period.

[0024] FIG. 2 Figure 1 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 (abbreviated as transceiver in the figure) 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 208 also converts received baseband signals from the processor, converts them to RF signals, and sends them out to the antenna 221. The processor 203 processes the received baseband signals and invokes different functional modules to perform functions in the base station 201. A memory 202 stores program instructions and data 209 (abbreviated as program in the figure) to control the operation of the base station.

[0025] A similar configuration exists in the UE 211, where an antenna 231 transmits and receives RF signals. An RF transceiver module 218 (abbreviated as transceiver in the figure) is coupled with the antenna to receive RF signals from the antenna, convert them to baseband signals and send them to a processor 213. The RF transceiver 218 also converts received baseband signals from the processor, converts them to RF signals, and sends them out to the antenna 231. The processor 213 processes the received baseband signals and invokes different functional modules to perform features in the UE 211. A memory 212 stores program instructions and data 219 (abbreviated as program in the figure) to control the operation of the UE.

[0026] The base station 201 and the UE 211 also include several functional modules and circuits to perform some embodiments of the present application. The 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., by executing the programs 209 and 219), for example, allow the base station 201 to schedule (by the scheduler 204), precode (by the precoder 205), encode (via the MIMO encoding circuit 206), and transmit control / configuration information and data (via the control / configuration circuit (CTL / CFG) 207) to the UE 211, and allow the UE 211 to receive control / configuration information and data (via the control / configuration circuit (CTL / CFG) 217), measure CSI reference signals (by the measurement circuit 216), estimate CSI (by the estimation circuit 215), and report the estimated CSI accordingly (by the reporting circuit 220).

[0027] FIG. 3 A sequence flow of the overall procedure for CSI acquisition and reporting is illustrated according to one novel aspect. In step 311, the gNB 301 provides CSI configuration information to the UE 302 for CSI acquisition and reporting. The CSI configuration information can include CSI reference signal configuration, CSI reference resource configuration, CSI reporting configuration, CSI reference slots for CSI measurement, CSI reference slots for CSI computation, and CSI computation periodicity, etc. In step 312, the gNB 301 transmits multiple occasions of CSI reference signals to the UE 302 through the configured CSI-RS resources. In step 321, the UE 302 receives multiple occasions of multiple CSI reference signals, estimates the effective downlink channel, and performs CSI computation based on the CSI configuration information.

[0028] In one novel aspect, two CSI reference slots are defined. A CSI reference slot for CSI measurement is defined to determine which CSI-RS is used for computing CSI. The CSI reference slot for CSI computation is defined to determine which first slot of the channel the UE assumes that the CSI computation should be based on, starting from that slot. In another novel aspect, the UE 302 can be configured by the gNB 301 to have a CSI computation period consisting of one or N slots, and can be divided into multiple non-overlapping sub-periods. In step 322, the UE 302 reports the computed CSI to the gNB based on the CSI configuration information. The reported CSI parameters can include Rank Indicator (RI), Precoding Matrix Indicator (PMI), and Channel Quality Index (CQI). In step 331, the gNB 301 receives the CSI feedback and determines the scheduling parameters for the subsequent PDSCH transport block (TB) transmission. In step 341, the gNB 301 transmits the data to the UE 302 through the PDSCH using the determined parameters including modulation, code rate, beamforming.

[0029] FIG. 4 A first embodiment is shown that applies the CSI reference slot for measurement and the CSI reference slot for computation to support high speed scenarios according to one novel aspect. The CSI reference signal (CSI-RS) is a dedicated measurement signal introduced for UEs to obtain CSI, e.g., for channel-dependent scheduling, link adaptation, and transmission settings related to multi-antenna transmission. The UE is configured to compute CSI based on one single occasion or multiple CSI-RS occasions on configured CSI reference resources (e.g., a set of downlink frequency domain and time domain resource blocks). The CSI reference resources of a serving cell are defined as follows. In the frequency domain, the CSI reference resources are defined by a set of downlink physical resource blocks corresponding to the frequency band related to the derived CQI value. In the time domain, the CSI reference resources are defined by a single downlink slot or special subframe related to the derived CQI value. In the spatial / layer domain, the CSI reference resources are defined by the RI and PMI related to the derived CQI value.

[0030] In current NR, CSI is calculated based on the slot location where the CSI reference resource is located, which is before the uplink slot for CSI reporting. However, CSI calculated for past slots can not be useful when gNB needs to perform scheduling later, especially in high speed scenarios. To improve throughput, gNB needs to know the CSI that is beneficial for “future” channel when channel changes a lot. Future CSI cannot be learned by “one-shot” measurement because any channel change needs at least two measurements to detect. In one novel aspect, UE can be configured to measure multiple occasions of CSI-RS on multiple slots of past DL channel, and UE can also be configured to calculate and predict CSI for future DL channel based on detected channel changes from multiple CSI-RS measurements.

[0031] Specifically, two CSI reference slots are defined to support high speed scenarios. CSI reference slot for CSI measurement is defined to determine which CSI-RS is used to calculate CSI. CSI reference slot for CSI calculation is defined to determine the first slot which is the first slot that UE assumes CSI calculation should be based on the channel at that time. When UE is configured to calculate CSI based on one single CSI-RS occasion, the two CSI reference slots coincide and are the same as CSI reference resource of Rel-15 NR. When UE is configured to calculate CSI based on multiple CSI-RS occasions, to determine which CSI-RS occasion is used to calculate CSI, the CSI reference slot for CSI measurement is the same as CSI reference resource of Rel-15 NR. When UE is configured to calculate CSI based on multiple CSI-RS occasions, the CSI reference slot for CSI calculation can be configured to be the same or after the uplink slot for CSI reporting. The multiple CSI-RS occasions can be multiple repetitions in a burst period, or multiple CSI-RS resources in a cross-slot CSI-RS resource set no later than the CSI reference resource.

[0032] In FIG. 4In an embodiment, the UE is configured to compute CSI based on multiple occasions of CSI-RS and report the CSI at slot n. The CSI reference slot for CSI measurement is the same as the CSI reference resource that occurs nCSI_ref slots before slot n, e.g., occurs at slot (n-nCSI_ref). That is, the UE computes the CSI based on multiple occasions of CSI-RS received and measured no later than slot (n-nCSI_ref). The CSI reference slot for CSI computation can be configured after the uplink slot for CSI reporting, with an offset K, e.g., at slot (n+K). That is, the CSI computed by the UE is for a future time, starting from slot (n+K), where the UE assumes that the CSI computation should predict on the channel starting from the future time of slot (n+K). Traditionally, due to fast channel variation, the CSI computed on the past CSI reference resource (e.g., slot (n-nCSI_ref)) becomes outdated for the future time (e.g., slot (n+K)). By configuring two separate CSI reference slots for CSI measurement and CSI computation, the UE can compute and predict the future CSI in slot (n+K) based on multiple occasions of CSI-RS received and measured no later than slot (n-nCSI_ref). For example, the CSI prediction can use an autoregressive (AR) model is performed. Multiple CSI-RS measurements can be used to estimate the AR coefficients {ci}. This equation can then be applied recursively to compute H[n+K].

[0033] FIG. 5 A second embodiment of configuring CSI computation period with full-period CSI and sub-period CSI to support high-speed scenarios is illustrated according to one novel aspect. A UE can be configured with a CSI computation period consisting of one or more slots and can be divided into multiple non-overlapping sub-periods. Each sub-period consists of X consecutive slots, where X is configurable. The CSI computed for the entire CSI computation period is referred to as “full-period” CSI. The CSI computed for a sub-period is referred to as “sub-period” CSI. A CSI computation period can start from the CSI reference slot for CSI computation. The CSI computation period can be set before the CSI resource reference specified in NR Release 15.

[0034] In FIG. 5In an example, in time domain, sub-periods SUB-P 0, SUB-P1, SUB-P P-1 are defined. In frequency domain, sub-bands SUB-B 0, SUB-B 1, SUB-B B-1 are defined. The size of a sub-period depends on the total number of slots in a CSI computation period. If the number of slots in CSI computation period A is larger than that in CSI computation period B, the size of sub-periods in A is larger than or equal to that in B. If the number of slots in a CSI computation period is less than or equal to a certain pre-defined value, only the CSI of the whole period is reported. If none of the slots in a CSI computation period contains at least one higher layer configured downlink or flexible symbol, the reporting of the CSI of the whole period is omitted. A valid sub-period is a sub-period in which all slots contain at least one higher layer configured downlink or flexible symbol. If a sub-period is not a valid sub-period, the reporting of the CSI of the sub-period is ignored. The valid sub-periods are indexed starting from the first valid sub-period. The gNB can inform the UE which sub-periods can be omitted for CSI reporting. The omitted sub-periods are considered as invalid sub-periods.

[0035] In a preferred embodiment, the CSI reporting is configured in slot n, and the CSI computation period starts from the CSI reference slot for CSI computation, e.g., slot (n+K), as shown. FIG. 5 Because the UE is configured to compute the CSI based on the occasions of multiple CSI-RSs measured no later than slot (n-nCSI_ref), the UE can take into account the time-domain correlation of multiple CSI-RSs to predict the CSI in slot (n+K). In addition, the UE is configured with a CSI computation period (e.g., across multiple slots) that has one full period and multiple non-overlapping sub-periods, which can exploit the time-domain correlation. The CSI computation period aims to help reduce the CSI feedback overhead. If N slots in the same sub-period can share the same CSI with little performance loss, the overhead is reduced to 1 / N. In addition, the channel variation over time is usually sparse in the transform domain, e.g., Doppler domain (via DFT). Then, M' << M values can be used to describe M sub-periods, e.g., M' / M = 1 / 4.

[0036] In another alternative embodiment, the CSI reporting is configured in slot n, and the CSI computation period ends at the CSI reference slot for CSI measurement, which is the same as the CSI reference resource, e.g., slot (n - nCSI_ref) (not shown). The purpose is to let the gNB predict the future CSI, so the UE should only compute the CSI based on past observations. In this case, the UE measures the CSI-RS received no later than slot (n - nCSI_ref) and computes the CSI using the computation period ending at the same slot. The UE still takes into account the time-domain correlation throughout the computation period to estimate the CSI of the DL channel, while reducing the CSI feedback overhead. However, the UE does not need to make any prediction of the CSI of the DL channel starting from future slot (n + K). The UE simply reports the computed past CSI to the network, and the network can use the received past CSI to predict the future CSI.

[0037] FIG. 6 Figure illustrates examples of CSI computation period with full-period CSI and sub-period CSI for wideband and subband. The gNB can configure the UE to compute different CSI computation combinations. As FIG. 6 (a) shows, the UE can be configured to compute wideband CSI throughout the entire CSI computation period. The UE assumes that the gNB will apply the computed CSI to the entire bandwidth throughout the entire CSI computation period. As FIG. 6 (b) shows, the UE can be configured to compute subband CSI throughout the entire CSI computation period. For each subband CSI, the UE assumes that the gNB will apply the computed CSI to the referenced subband throughout the entire CSI computation period. In this example, three subbands SUB-B 0, SUB-B 1, and SUB-B 2 are defined, and the UE is configured to compute subband CSI for SUB-B 0, SUB-B 1, and SUB-B 2 throughout the entire CSI computation period.

[0038] As FIG. 6 (c) depicts, the UE can be configured to compute wideband CSI for each subperiod. The UE assumes that each computed CSI will be applied by the gNB to the entire bandwidth in the specified subperiod. In this example, three subperiods SUB-P 0, SUB-P 1, and SUB-P 2 are defined, and the UE is configured to compute CSI for the entire bandwidth in the three subperiods SUB-P 0, SUB-P 1, and SUB-P 2. As FIG. 6(d) As shown, the UE can be configured to compute subband CSI for each sub-period. The UE assumes that each computed CSI will be applied by the gNB to the reference subband in the reference sub-period. In this example, three subbands SUB-B 0, SUB-B 1, and SUB-B 2 are defined, and three sub-periods SUB-P 0, SUB-P 1, and SUB-P 2 are defined. The UE is configured to compute subband CSI (0-8) for SUB-B 0, SUB-B 1, and SUB-B 2 in the three sub-periods SUB-P 0, SUB-P 1, and SUB-P 2.

[0039] FIG. 7 An example of CSI computation and reporting to support high speed scenarios is illustrated according to one novel aspect. In one embodiment, the gNB can inform the UE which sub-periods can be omitted for CSI reporting. The omitted sub-periods are considered as invalid sub-periods. In FIG. 7 In the example of (a), according to the gNB’s notification, sub-periods 1 and 5 are omitted, and sub-period 2 is omitted because none of the slots include at least one higher layer configured downlink or flexible symbol. Therefore, the UE only needs to report the sub-period CQI for SUB-P 0 (0), SUB-P 3 (1), and SUB-P 4 (2). In another embodiment, the gNB can configure the UE to report sub-period CQI only for the best K sub-periods in the CSI computation period, where K is configurable. In FIG. 7 In the example of (b), each of the sub-period CQI for sub-periods 1, 2, and 4 is better than the sub-period CQI for sub-periods 0, 3, and 5. If K = 3, the UE only reports the sub-period CQI for SUB-P 1 (0), SUB-P 2 (1), and SUB-P 4 (2). In one embodiment, the number of reported sub-periods can be determined by the UE. The reported CSI consists of two stages, where the UE reports the selected number of sub-periods in the first stage.

[0040] In one example, the sub-period CQI is reported by the UE by signaling the quantization difference from the whole period CQI. In another example, the sub-period RI is reported by the UE by signaling the difference from the whole period RI. In another example, the sub-period PMI shares the same base vector as the whole period PMI. The coefficients of the sub-period PMI are reported by signaling the quantized amplitude and phase difference from the coefficients of the whole period PMI.

[0041] In one example, for semi-persistent CSI reporting on PUSCH, the configuration of CSI computation period can be updated by activating DCI scrambled with SP-CSI-RNTI, e.g., the number of slots. In another example, for semi-persistent CSI reporting on PUCCH, the configuration of CSI computation period can be updated by activation command, e.g., the number of slots. In another example, for aperiodic CSI reporting, the configuration of CSI computation period can be updated by triggering DCI, e.g., the number of slots.

[0042] FIG. 8 is a flowchart of a method of configuring CSI computation period to support high speed scenario according to a novel aspect. In step 901, a UE receives channel state information reference signal (CSI-RS) configuration information from a base station (gNB). The CSI-RS configuration includes CSI-RS resources and a CSI computation period, which has one or more non-overlapping sub-periods within the CSI computation period in time domain. In step 902, the UE measures multiple occasions of CSI-RS of a downlink channel received through the configured CSI-RS resources. In step 903, the UE estimates the CSI of the downlink channel for the CSI computation period using the timing correlation of the multiple CSI-RS occasions. In step 904, the UE reports the estimated CSI of the downlink channel to the gNB and reports the estimated CSI according to the configured CSI computation period.

[0043] FIG. 9 is a flowchart of a method of configuring CSI computation period to support high speed scenario according to a novel aspect. In step 901, a UE receives channel state information reference signal (CSI-RS) configuration information from a base station (gNB). The CSI-RS configuration includes CSI-RS resources and a CSI computation period, which has one or more non-overlapping sub-periods within the CSI computation period in time domain. In step 902, the UE measures multiple occasions of CSI-RS of a downlink channel received through the configured CSI-RS resources. In step 903, the UE estimates the CSI of the downlink channel for the CSI computation period using the timing correlation of the multiple CSI-RS occasions. In step 904, the UE reports the estimated CSI of the downlink channel to the gNB and reports the estimated CSI according to the configured CSI computation period.

[0044] While the application has been described in connection with certain specific embodiments thereof, it is to be understood that the application is not limited to the described embodiments but, on the contrary, is intended to cover various modifications, alternatives, and equivalents. Therefore, you can implement various modifications, modifications and combinations of the features described in the embodiments without departing from the scope of the application set forth in the claims.

Claims

1. A method of channel state information measurement and computation, comprising: receiving, by a user equipment (UE), channel state information reference signal (CSI-RS) configuration information from a base station (BS); determining, according to the CSI-RS configuration information, a first channel state information (CSI) reference time slot for measurement and a second CSI reference time slot for computation, wherein the second CSI reference time slot occurs in time domain after the first CSI reference time slot; measuring, by the UE, a CSI-RS of a downlink channel received before the first CSI reference time slot for measurement; and computing, by the UE, a CSI of the downlink channel based on the second CSI reference time slot for computation, wherein the UE estimates and predicts the CSI of the downlink channel starting from the second CSI reference time slot for computation. The UE is configured to report the CSI in a CSI reporting time slot.

2. The method of channel state information measurement and calculation according to claim 1, wherein, The first CSI reference time slot for measurement occurs at an offset before the CSI reporting time slot.

3. The method of claim 2, wherein, The second CSI reference time slot for computation occurs at an offset after the CSI reporting time slot.

4. The method of claim 2, wherein, The UE reports, to the BS, a CSI of a downlink channel including at least one of a rank indicator, a precoding matrix indicator, and a channel quality indicator.

5. The method for channel state information measurement and calculation according to claim 1, wherein, The UE is configured with a plurality of CSI-RS occasions before a first CSI reference time slot for CSI measurement.

6. The method for channel state information measurement and calculation according to claim 1, wherein, The UE estimates and predicts the CSI of the downlink channel using a timing correlation of the plurality of CSI-RS occasions.

7. The method of channel state information measurement and calculation according to claim 6, wherein, The UE is configured with a computation period for computing the CSI of the downlink channel during the computation period.

8. The method for channel state information measurement and calculation according to claim 1, wherein, The computation period further includes a plurality of sub-periods within the computation period.

9. The method of channel state information measurement and calculation according to claim 8, wherein, The computed CSI includes sub-period-CSI and whole-period-CSI for the downlink channel.

10. The method of channel state information measurement and calculation according to claim 9, wherein, 11. A user equipment (UE) for channel state information measurement and computation, comprising: a receiver configured to receive channel state information reference signal (CSI-RS) configuration information from a base station (BS); a control circuit configured to determine, according to the CSI-RS configuration information, a first channel state information (CSI) reference time slot for measurement and a second CSI reference time slot for computation, wherein the second CSI reference time slot occurs in time domain after the first CSI reference time slot; a measurement circuit configured to measure a CSI-RS of a downlink channel received before the first CSI reference time slot for measurement; and a CSI processing circuit configured to compute a CSI of the downlink channel based on the second CSI reference time slot for computation, wherein the UE estimates and predicts the CSI of the downlink channel starting from the second CSI reference time slot for computation. The UE is configured to report the CSI in a CSI reporting time slot. The first CSI reference time slot for measurement occurs at an offset before the CSI reporting time slot.

12. The UE of channel state information measurement and computation according to claim 11, wherein, ​ 13. The UE of channel state information measurement and computation according to claim 12, c h a r a c t e r i z e d b y ​ 14. The UE of channel state information measurement and computation of claim 12, wherein, The second channel state information (CSI) reference time slot for computation occurs at an offset after the CSI reporting time slot.

15. The CSI measurement and computation UE of claim 11, wherein, The UE reports, to the BS, CSI of a downlink channel including at least one of a rank indicator, a precoding matrix indicator, and a channel quality indicator.

16. The CSI measurement and computation UE of claim 11, wherein, The UE is configured with a plurality of CSI-RS occasions before the first channel state information (CSI) reference time slot for CSI measurement.

17. The UE of channel state information measurement and computation according to claim 16, c h a r a c t e r i z e d b y The UE estimates and predicts CSI of the downlink channel using a timing correlation of the plurality of CSI-RS occasions.

18. The CSI measurement and computation UE of claim 11, wherein, The UE is configured with a computation period during which the UE computes CSI of the downlink channel.

19. The UE of channel state information measurement and computation according to claim 18, c h a r a c t e r i z e d b y The computation period further includes a plurality of sub-periods within the computation period.

20. The UE of channel state information measurement and computation according to claim 19, wherein, The computed CSI includes sub-period-CSI and whole-period-CSI for the downlink channel.

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