Patent Publication Number: US-2021194557-A1

Title: Accurate Sidelink CSI Report

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is filed under 35 U.S.C. § 111(a) and is based on and hereby claims priority under 35 U.S.C. § 120 and § 365(c) from International Application No. PCT/CN2019/126162, titled “Methods and Apparatus Accurate Sidelink CSI Report,” with an international filing date of Dec. 18, 2019. This application claims priority under 35 U.S.C. § 119 from Chinese Application Number CN 202011481175.0, titled “ACCURATE SIDELINK CSI REPORT,” filed on Dec. 15, 2020. The disclosure of each of the foregoing documents is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate generally to wireless communication, and, more particularly, to accurate sidelink CSI report with restriction procedure. 
     BACKGROUND 
     5G radio access technology will be a key component of the modern access network. It will address high traffic growth and increasing demand for high-bandwidth connectivity. In 3GPP New Radio (NR), sidelink continues evolving. With new functionalities supported, the sidelink offers low latency, high reliability and high throughout for device to device communications. NR vehicle to everything (V2X) supports sidelink measurement. In sidelink measurement report, channel quality indication (CQI)/ranking indication (RI) are used for channel state information (CSI) report. Unlike the CSI report for Uu interface, the sidelink CSI report is carried on MAC control element (CE). 
     Improvements and enhancements are required for measurement configuration and report for sidelink open-loop power control. 
     SUMMARY 
     Apparatus and methods are provided for the UE performs restriction procedures for accurate sidelink CSI report using MAC CE. In one novel aspect, the UE stops sending SL CSI if it is larger than the configured delay budget or a maximum delay to address the out-of-date issue. In one embodiment, the UE establishes a sidelink with a receiving UE in a wireless network, performs SL measurements on the sidelink to obtain an SL CSI information including CQI and/or RI, generates a first SL CSI report based on the SL CSI information using a MAC CE, wherein the first SL CSI report is transmitted or retransmitted when a CSI trigger is detected, and cancels a triggered first SL CSI report transmission when a latency bound associated to the triggered first SL CSI report exceeds a latency threshold. In one embodiment, the latency threshold is a configured delay budget. In another embodiment, the configured delay budget is configured by RRC signaling. In yet another embodiment, the UE subsequently, transmits a second SL CSI report with newly measured CSI information upon completion of the first CSI report transmission. 
     In one novel aspect, the UE performs restriction procedures to get accurate sidelink CSI report. In one embodiment, the UE establishes a sidelink with a receiving UE in a wireless network, performs SL measurements on the sidelink to obtain an SL CSI including CQI and/or RI, generates a first SL CSI report based on the SL CQI/RI using a MAC CE, wherein the first SL CSI report is transmitted or retransmitted when a CSI trigger is detected, and performs an SL CSI report restriction process such that the receiving UE receives up-to-date CSI report. In one embodiment, the UE starts a prohibit timer upon transmission of the first SL CSI report and prohibits generating a second SL CSI report on MAC CE before the prohibit timer expires. In another embodiment, the UE prepares the second SL CSI report on MAC CE based on latest SL CSI information upon expiration of the prohibiting timer and transmits the second SL CSI report to the receiving UE. In one embodiment, the UE prohibits generating of a second SL CSI report before a success transmission of the first SL CSI report. In another embodiment, the UE prohibits a hybrid automatically retransmission request (HARQ) for the first SL CSI report. In one embodiment, the UE starts a prohibit timer upon transmission of the first SL CSI report and prohibits new data from being delivered to a PHY layer before the prohibit timer expires. In another embodiment, the UE assigns a fix numbered HARQ process to the first SL CSI report and prohibits new data from being delivered to a PHY layer in the fix numbered HARQ before an ACK is received corresponding to the first SL CSI report. In one embodiment, the UE includes in the first SL CSI report at least one reference elements comprising a version number of the first SL CSI report and/or a time stamp of the first SL CSI report. 
     This summary does not purport to define the invention. The invention is defined by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention. 
         FIG. 1  is a schematic system diagram illustrating an exemplary wireless network for measurement accurate sidelink CSI report with restriction procedure in accordance with embodiments of the current invention. 
         FIG. 2  illustrates an exemplary NR wireless system with centralized upper layers of the NR radio interface stacks in accordance with embodiments of the current invention. 
         FIG. 3  illustrated exemplary diagrams for a UE to perform CSI restriction procedures such that the receiving UE receives latest CSI report in order in accordance with embodiments of the current invention. 
         FIG. 4  illustrates exemplary diagrams of a restriction procedure of the TX UE stopping sending SL CSI when the latency of a successful sending of the CSI report is larger than a configured delay budget or a maximum delay in accordance with embodiments of the current invention. 
         FIG. 5  illustrates exemplary diagrams of a restriction procedure of the TX UE setting a prohibit timer that keeps the CSI report pending without generating MAC CE for transmission in accordance with embodiments of the current invention. 
         FIG. 6  illustrates exemplary diagrams of a restriction procedure of the TX UE setting a restriction at the MAC layer for packet data unit (PDU) assembly in accordance with embodiments of the current invention. 
         FIG. 7  illustrates exemplary diagrams of a restriction procedure of the TX UE setting a restriction of CSI report for HARQ retransmission in accordance with embodiments of the current invention. 
         FIG. 8  illustrates exemplary diagrams of a restriction procedure of including a version number and/or time stamps for CSI report MAC CE messages in accordance with embodiments of the current invention. 
         FIG. 9  illustrates exemplary diagrams of a restriction procedure of the TX UE setting prohibit timer with HARQ buffer to prohibit new data being delivered to the PHY layer in accordance with embodiments of the current invention. 
         FIG. 10  illustrates exemplary diagrams of a restriction procedure of the TX UE setting TB including only CSI report and no mux with SL data in accordance with embodiments of the current invention. 
         FIG. 11  illustrates an exemplary flow chart of a UE restriction procedure by stopping SL CSI sending when latency is larger than a configured delay budge or a maximum delay in accordance with embodiments of the current invention. 
         FIG. 12  illustrates an exemplary flow chart of a UE restriction procedure for accurate CSI report for sidelink in accordance with embodiments of the current invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
     In an NR wireless network, the sidelink is enabled. NR vehicle to everything (V2X) supports the transmission of CSI-RS for CQI and/or RI measurement. In the following description, CQI/RI is used for simplicity. CSI-RS is confined with physical sidelink shared channel (PSSCH) transmission and it can only be transmitted if SL CQI/RI report is enabled by high layer signaling. The SL CQI/RI report from RX UE is enabled by SCI (i.e. Sidelink Control Information) at physical layer to help the TX UE to do link adaption. The traditional CSI report over Uu is performed at physical layer. In NR V2X, 3GPP agreed to report the SL CSI via MAC CE (with one OCTET) identified by new logic channel identification (LCID). The CSI report event shall be cancelled if the CSI report has been transmitted. The CSI report is one-shot transmission. There is fixed priority for the transmission of SL CSI MAC CE. The prioritization rule for SL data can be reused for SL CSI MAC CE. Since the reception of a particular SL CSI report at the Receiver side may be delayed, or the transmission of a particular SL CSI report is not correctly decoded by the Receiver side (at HARQ combination), which leads to a retransmission of the SL CSI report by HARQ. The sequential SL CSI report organized by MAC will be sent by PHY in a non-sequential manner, and eventually being received by Receiver side out of order. The Receiver side receive CSI report, which is out of date. There will be a risk for the Receiver side to adjust the MCS according to the CSI report, which is out of date. The same applies to unicast and groupcast. In one novel aspect, CSI report restriction procedures are implemented such that the receiving UE would not receive out of order and/or out of date CSI report. 
       FIG. 1  is a schematic system diagram illustrating an exemplary wireless network for accurate sidelink CSI report with restriction procedure in accordance with embodiments of the current invention. Wireless system  100  includes one or more fixed base infrastructure units forming a network distributed over a geographical region. The base unit may also be referred to as an access point, an access terminal, a base station, a Node-B, an eNode-B (eNB), a gNB, or by other terminology used in the art. The network can be a homogeneous network or heterogeneous network, which can be deployed with the same frequency or different frequency. gNB  101  is an exemplary base station in the NR network. 
     Wireless network  100  also includes multiple communication devices or mobile stations, such as user equipments (UEs)  111 ,  112 ,  113 ,  114 ,  115 ,  116 , and  117 . The exemplary mobile devices in wireless network  100  have sidelink capabilities. The mobile devices can establish one or more connections with one or more base stations, such as gNB  101 . UE  111  has an access link, with uplink (UL) and downlink (DL), with gNB  101 . UE  112 , which is also served by gNB  101 , may also establish UL and DL with gNB  101 . UE  111  also establishes a sidelink with UE  112 . Both UE  111  and UE  112  are in-coverage devices. Mobile devices on vehicles, such as mobile devices  113 ,  114 , and  115 , also have sidelink capabilities. Mobile device  113  and mobile device  114  are covered by gNB  101 . Mobile device  113 , an in-coverage device, establishes sidelink with mobile device  114 , which is also an in-coverage device. Mobile device  115  on a vehicle, however, is an out-of-coverage device. In-coverage mobile device  114  establishes a sidelink with the out-of-coverage device  115 . In other embodiments, the mobile devices, such as UE  116  and  117 , may both be out-of-coverage but can transmit and receive data packets with another one or more other mobile stations with sidelink connections. 
       FIG. 1  further illustrates simplified block diagrams of a base station and a mobile device/UE for early packet filtering for UE sidelink relay. gNB  101  has an antenna  156 , which transmits and receives radio signals. An RF transceiver circuit  153 , coupled with the antenna, receives RF signals from antenna  156 , converts them to baseband signals, and sends them to processor  152 . RF transceiver  153  also converts received baseband signals from processor  152 , converts them to RF signals, and sends out to antenna  156 . Processor  152  processes the received baseband signals and invokes different functional modules to perform features in gNB  101 . Memory  151  stores program instructions and data  154  to control the operations of gNB  101 . gNB  101  also includes a set of control modules  155  that carry out functional tasks to communicate with mobile stations. 
     UE  111  has an antenna  165 , which transmits and receives radio signals. An RF transceiver circuit  163 , coupled with the antenna, receives RF signals from antenna  165 , converts them to baseband signals, and sends them to processor  162 . In one embodiment, the RF transceiver may comprise two RF modules (not shown). A first RF module is used for HF transmitting and receiving, and the other RF module is used for different frequency bands transmitting and receiving, which is different from the HF transceiver. RF transceiver  163  also converts received baseband signals from processor  162 , converts them to RF signals, and sends out to antenna  165 . Processor  162  processes the received baseband signals and invokes different functional modules to perform features in THE UE. Memory  161  stores program instructions and data  164  to control the operations of THE UE. Antenna  165  sends uplink transmission and receives downlink transmissions to/from antenna  156  of gNB  101 . 
     The UE also includes a set of control modules that carry out functional tasks. These control modules can be implemented by circuits, software, firmware, or a combination of them. A sidelink connection circuit  191  establishes an SL connection with a receiving UE in the wireless network in the wireless network. A measurement circuit  192  performs SL measurements on the sidelink to obtain an SL channel state information (CSI) information including channel quality indicator (CQI) and/or ranking indicator (RI). A CSI report circuit  193  generates a first SL CSI report based on the SL CSI information using a MAC control element (CE), wherein the first SL CSI report is transmitted or retransmitted when a CSI trigger is detected. A restriction circuit  194  performs an SL CSI report restriction process such that the receiving UE receives up-to-date CSI report. 
       FIG. 2  illustrates an exemplary NR wireless system with centralized upper layers of the NR radio interface stacks in accordance with embodiments of the current invention. Different protocol split options between central unit (CU) and distributed unit (DU) of gNB nodes may be possible. The functional split between the CU and DU of gNB nodes may depend on the transport layer. Low performance transport between the CU and DU of gNB nodes can enable the higher protocol layers of the NR radio stacks to be supported in the CU, since the higher protocol layers have lower performance requirements on the transport layer in terms of bandwidth, delay, synchronization and jitter. In one embodiment, SDAP and PDCP layer are located in the CU, while RLC, MAC and PHY layers are located in the DU. A Core unit  201  is connected with one central unit  211  with gNB upper layer  252 . In one embodiment 250, gNB upper layer  252  includes the PDCP layer and optionally the SDAP layer. Central unit  211  is connected with distributed units  221 ,  222 , and  221 . Distributed units  221 ,  222 , and  223  each correspond to a cell  231 ,  232 , and  233 , respectively. The DUs, such as  221 ,  222  and  223  include gNB lower layers  251 . In one embodiment, gNB lower layers  251  include the PHY, MAC and the RLC layers. In another embodiment 260, each gNB has the protocol stacks  261 , including SDAP, PDCP, RLC, MAC and PHY layers. 
     In one novel aspect, the sidelink CSI report restriction procedures are implemented to support accurate CSI report over Sidelink in mobile communication system. The transmitting (TX) UE sets up the restriction of CSI report via initiation of a prohibit timer. If a CSI report is triggered, but the prohibit timer is running, then the CSI report keeps pending and UE does not generate the MAC CE for transmission to Physical layer. The restriction of CSI report is to avoid out of date and/or out of order delivery of CSI report. 
       FIG. 3  illustrated exemplary diagrams for a UE to perform CSI restriction procedures such that the receiving UE receives latest CSI report in order in accordance with embodiments of the current invention. A transmitting UE  301  establishes sidelink connection with a receiving UE  302 . At step  311 , UE  301  performs SL measurement. At step  312 , UE  301  generates MAC CE that carries SL CSI report with CQI/RI based on the performed measurement. At step  331 , UE  301  sends MAC CE carrying the first CSI report to UE  302 . At step  321 , UE  321  decodes the message carrying the first CSI report if UE  302  receives the message. In one scenario, the message carrying the first CSI report may be lost and UE  302  did not receive it. In other scenarios, UE  302  cannot decode the received message correctly to get the first CSI report. At the same time, UE  301  detects a trigger for the second CSI report. UE  301  generates a new CSI report (the 2 nd  CSI report) in MAC CE and passes the MAC PDU to the PHY layer queue  351  for transmission. While UE  302  cannot get the first CSI report correctly, a NACK triggering HARQ is sent to UE  301 . In other scenarios, the HARQ entity buffers the transmission block carrying the first CSI report message after its initial transmission. And then PHY queue  352  has both the 2 nd  CSI report and the 1 st  CSI report for retransmission in its buffer. At step  341 , UE  301  sends the 2 nd  CSI report based on PHY queue  352 . Subsequently, at step  342 , UE  301  sends the 1 st  CSI report for retransmission based on HARQ feedback. Scenario  340  described above creates an out-of-order and out-of-date CSI report for the receiving UE  302 . In one novel aspect, scenario  340  can be avoided by performing SL CSI report restriction procedure  360 . The restriction procedure discussed in the following sections are implemented independently to avoid the problem. In other embodiment, the combination of the individual procedures presented below are used. 
       FIG. 4  illustrates exemplary diagrams of a restriction procedure of the TX UE stopping sending SL CSI when the latency of a successful sending of the CSI report is larger than a configured delay budget in accordance with embodiments of the current invention. In one novel aspect, the UE stops sending SL CSI if it is later than the configured delay budget to address the out-of-date issue. A transmitting UE  401  establishes a sidelink connection with a receiving UE  402 . At step  411 , UE  401  performs sidelink measurement. At step  421 , UE  401  generates the first CSI report containing CQI/RI based on the measurement. At step  431 , UE  401  sends the CSI report message with the first CSI report to UE  402 . At step  451 , triggered by the sending the first CSI report, a timer is started to track the latency bound for the transmission of the first CSI report. In some exemplary scenarios, at step  432 , UE  402  sends a NACK. At step  433 , UE  401  retransmits a CSI report message with the first CSI report. At step  434 , UE  402  sends a second NACK. PHY queue  481  may include the first CSI report (and a second CSI report). At step  442 , the timer expires. Upon expiration of the latency timer, at step  450 , UE  401  stops sending CSI report. In one embodiment, step  450  is triggered by the latency being over a configured delay budget. In another embodiment, step  450  is triggered by the latency being over a maximum delay. UE  401  subsequently cancels pending CSI report in procedure  461 . PHY queue  482  is empty without CSI report. Subsequently, UE  401  resumes the CSI report procedure and consequently, a latest generated CSI report is sent to UE  402  in procedure  471 . In another embodiment, procedure  462  is used. At step  435 , an ACK for the first CSI report is received, and subsequently, the CSI report procedure is resumed. 
       FIG. 5  illustrates exemplary diagrams of a restriction procedure of the TX UE setting a prohibit timer that keeps the CSI report pending without generating MAC CE for transmission in accordance with embodiments of the current invention. In one embodiment, the UE sets up a prohibit timer for CSI report MAC CE transmission. If the prohibit timer is set long enough, we may be able to avoid the problem of out of order delivery of CSI report MAC CE. Of course, the prohibit timer should not be set too long which cause non-instant channel state information. If a CSI report is triggered, but the prohibit timer is running, then the CSI report keeps pending and UE do not generate the MAC CE for transmission. When the prohibit timer expires, UE transmit the MAC CE including the latest information. UE  501  establishes a sidelink connection with UE  502 . At step  511 , UE  501  performs sidelink measurement. The first measurement is in the measurement queue  581 . At step  512 , UE  501  generates the first CSI report containing CQI/RI based on the measurement. The MAC CE is delivered to the PHY queue  591  with the first CSI report. At step  531 , UE  501  sends the CSI report message with the first CSI report to UE  502 . At step  551 , a prohibit timer is started. In one exemplary scenario, at step  561 , new measurement is triggered with the second measurement in the measurement queue  582 . At step  532 , UE  502  sends a NACK. At step  560 , as the prohibit timer is still running, UE  501  keeps the second CSI report pending and does not generate the MAC CE for transmission. At step  552 , the prohibit timer expired. In one scenario, the pending second CSI report is now generated with MAC CE and passed to PHY queue  593 . In other scenarios, new measurement is triggered at step  561  after the prohibit timer expires. A third CSI report is generated with MAC CE and passed to the PHY queue  594 . At step  562 , new message carrying the new CSI report is generated. At step  533 , UE  501  sends the new CSI report. 
       FIG. 6  illustrates exemplary diagrams of a restriction procedure of the TX UE setting a restriction at the MAC layer for packet data unit (PDU) assembly in accordance with embodiments of the current invention. In one embodiment, the UE sets up a restriction at MAC layer for PDU assembly. No new CSI report MAC CE is allowed to be multiplexed and assembled into the MAC PDU if there is no acknowledgement received for the previously CSI report MAC CE (exclusively assembled or non-exclusively assembled). In logic channel priority (LCP), CSI report MAC CE is put lowest priority, which can be controlled by a new timer, to avoid transmitting out of date CSI report. In one embodiment, CSI report MAC CE is prohibited from being multiplexed into a SL MAC PDU if the previous transmission is not yet successful. In another embodiment, CSI report MAC CE is put lowest priority. UE  601  establishes a sidelink connection with UE  602 . At step  611 , UE  601  performs sidelink measurement. The first measurement is in the measurement queue. UE  601  assembles CSI report in procedure  613 . At step  612 , UE  601  generates the first CSI report containing CQI/RI based on the measurement. The measurement data is generated for MAC CE to include the first measurement, with a designated LCID and a regular LCP. The MAC CE is delivered to the PHY queue with the first CSI report. At step  631 , UE  601  sends the CSI report message with the first CSI report to UE  602 . At step  661 , new measurement is triggered, and a second CSI report is generated in measurement queue. At step  662 , UE  601  checks if the ACK is received for the message carrying the first CSI report. If step  662  determines yes, procedure  665  is performed to pass the second measurement to generate the MAC CE for the second CSI report, passes the MAC PDU with regular LCP to PHY queue with the second CSI report. If step  662  determines no, a MAC layer restriction is performed. In one embodiment, procedure  667  is performed where no MAC PDU is generated for the MAC CE carrying the second CSI report. In another embodiment, procedure  668  is preformed where the MAC PDU carrying the second CSI report is set to have the lowest LCP. A CSI report message carrying the second CSI report is sent to UE  602  at step  633 . 
       FIG. 7  illustrates exemplary diagrams of a restriction procedure of the TX UE setting a restriction of CSI report for HARQ retransmission in accordance with embodiments of the current invention. In one embodiment, the UE sets up a restriction for retransmission of CSI report MAC CE. No HARQ retransmission is allowed for CSI report MAC CE. A one-shot transmission at PHY together with MAC is performed. The CSI report transmitted, and thus received by the receiving UE, will be sequential and in order. Some CSI report may be lost due to no retransmission. UE  701  establishes a sidelink connection with UE  702 . At step  711 , UE  701  performs sidelink measurement. At step  712 , UE generate CSI report with CQI/RI MAC CE. At step  731 , UE  701  sends CSI report message with the first CSI report to UE  702 . At step  732 , UE  701  determines is a message with HARQ request corresponds to a CSI report MAC CE message. If step  732  determines yes, at step  750 , UE  701  prohibits HARQ retransmission of the message carrying the CSI report MAC CE. 
       FIG. 8  illustrates exemplary diagrams of a restriction procedure of including a version number and/or time stamps for CSI report MAC CE messages in accordance with embodiments of the current invention. Version number/time stamp information can be included in the CSI report MAC CE. The receiving UE has reference of the sequence of the CSI reports. UE  801  establishes a sidelink connection with UE  802 . At step  811 , UE  801  performs sidelink measurement. At step  812 , UE  801  determines if the MAC CE includes a CSI report. If step  821  determines yes, UE  801  adds version number and/or time stamp to the message in step  850 . At step  822 , UE  801  generates CSI report with CQI/RI MAC CE together with the version number and/or time stamp. At step  831 , UE  801  sends CSI report message with the first CSI report to UE  802 . 
       FIG. 9  illustrates exemplary diagrams of a restriction procedure of the TX UE setting prohibit timer with HARQ buffer to prohibit new data being delivered to the PHY layer in accordance with embodiments of the current invention. In one embodiment, the UE sets up a prohibit timer for transmission for data (assembled with a CSI report MAC CE) within HARQ buffer. No new data is delivered from HARQ buffer to PHY before the expiry of the timer. In one embodiment, an accurate value of the duration of the timer is selected to ensure the previous CSI report MAC CE has already correctly transmitted by sender and received by receiver including possible retransmissions. The timer does impact the CSI report assembly at MAC layer. UE  901  establishes a sidelink connection with UE  902 . At step  911 , UE  901  sends CSI report message with the first CSI report to UE  902 . At step  951 , a prohibit timer with value  961  is started upon the transmission of the first CSI report. While prohibit timer is running, at step  950 , no new data is delivered from HARQ to the PHY. At step  952 , prohibit timer expires. At step  931 , UE  901  sends a new CSI report to UE  902 . 
       FIG. 10  illustrates exemplary diagrams of a restriction procedure of the TX UE setting TB including only CSI report and no mux with SL data in accordance with embodiments of the current invention. The UE sets up a restriction at HARQ process assignment. The CSI report MAC CE is assembled in an exclusive manner. No multiplexing is allowed between CSI report MAC CE and SL data, nor between CSI report MAC CE and PC5-RRC/S control signaling. The TB includes only the CSI report MAC CE goes to the HARQ buffer of a fixed numbered HARQ process (e.g. 1 st  HARQ process) sequentially. The new TB going to the HARQ buffer of that HARQ process shall not be delivered to the PHY until the successful transmission of the previous TB. The transmission is successful when there is already received HARQ ACK for the TB. A new timer can be used to avoid too long time spent for the successful transmission of the previously TB. UE  1001  establishes a sidelink connection with UE  1002 . At step  1011 , UE  1001  sends CSI report message with the first CSI report to UE  1002 . At step  1012 , a new measurement is triggered. At step  1021 , UE  1001  determines if the ACK for the first CSI report sent at step  1011  is received. If step  1021  determines yes, the CSI report MAC CE is assembled in an exclusive manner. At step  1051 , no multiplexing is allowed between CSI report MAC CE and SL data, nor between CSI report MAC CE and PC5-RRC/S control signaling. A fixed number of HARQ is assigned. If step  1021  determines no, at step  1052 , new TB going to the HARQ buffer of that HARQ process shall not be delivered to the PHY. At step  1031 , upon successful receives ACK for the first CSI report, a new CSI report is sent to UE  1002 . 
       FIG. 11  illustrates an exemplary flow chart of a UE restriction procedure by stopping SL CSI sending when latency is larger than a configured delay budge in accordance with embodiments of the current invention. At step  1101 , the UE establishes a sidelink (SL) connection with a receiving UE in a wireless network. At step  1102 , the UE performs SL measurements on the sidelink to obtain an SL CSI information including channel quality indicator (CQI) and/or ranking indicator (RI). At step  1102 , the UE generates a first SL channel state information (CSI) report based on the SL CSI information using a MAC control element (CE), wherein the first SL CSI report is transmitted or retransmitted when a CSI trigger is detected. At step  1104 , the UE cancels a triggered first SL CSI report transmission when a latency bound associated to the triggered first SL CSI report exceeds a latency threshold. The said latency threshold can be a configured delay budget according to the configuration from RRC. 
       FIG. 12  illustrates an exemplary flow chart of a UE restriction procedure for accurate CSI report for sidelink in accordance with embodiments of the current invention. At step  1201 , the UE establishes an SL connection with a receiving UE in a wireless network. At step  1202 , the UE performs SL measurements on the sidelink to obtain an SL CSI information including channel quality indicator (CQI) and/or ranking indicator (RI). At step  1203 , the UE generates a first SL channel state information (CSI) report based on the SL CSI information using a MAC control element (CE), wherein the first SL CSI report is transmitted or retransmitted when a CSI trigger is detected. At step  1204 , the UE performs an SL CSI report restriction process such that the receiving UE receives up-to-date CSI report. 
     Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, 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.