G.5.2 Test method for PSCCH/PSSCH performance using sidelink HARQ feedback

38.521-43GPPNRPart 4: PerformanceRadio transmission and receptionRelease 17TSUser Equipment (UE) conformance specification

Test method described in this subclause applies to the UE supporting psfch-FormatZeroSidelink-r16.

Figure G.5.2-1 descriptively represents the course of a test based in two metrics: the noise-normalized test SNR and the performance session, represented in terms of fractional throughput. The SS counts the sidelink HARQ feedback samples sent by the UE under test during performance session and calculate the performance metrics based on them. This effectively results on the discard of early sidelink HARQ feedback that might take place between their initialization at State 4-A and the stabilized performance session. The test method is as follows:

1) The UE is set on state 4-A with generic procedure parameters Test Loop Function = On according to TS 38.508-1 [6] clause 4.4A.2. The UE is configured as the receiving UE.

2) Once the UE is operating on state 4-A, the SNR is set to the test SNR level and the scheduling of sidelink packets starts. This takes place during the test procedure stage. The SS receives every sidelink HARQ feedback sent by the UE under test and starts to count the number of ACK/NACK/DTX (for ACK/NACK HARQ) or NACK/DTX (for NACK-only HARQ).

3) Once the scheduling of sidelink packets starts, the SS shall wait for a stability window of T=10 seconds before recoding the number of sidelink HARQ feedback sent by the UE under test.

4) Upon expiration of the stability window, the SS shall recode the number of ACK/NACK/DTX (for ACK/NACK HARQ) or NACK/DTX (for NACK-only HARQ) sent by the UE under test (Time Point A in Figure G.5.2-1). Then the performance session starts.

5) During the performance session the SS shall record the number of transmitted sidelink packets (PSCCH, PSSCH carrying SDAP SDU) starting in Time Point A and ending in Time Point B and keep counting the number of ACK/NACK/DTX (for ACK/NACK HARQ) or NACK/DTX (for NACK-only HARQ) sent by the UE under test. The performance session lasts for the Test Time defined in sections G.5.4 and G.5.5 for throughput and PSCCH miss-detection probability, respectively.

6) Once the Test Time is completed the SS shall recode the number of ACK/NACK/DTX (for ACK/NACK HARQ) or NACK/DTX (for NACK-only HARQ) sent by the UE under test (Time Point B in Figure G.5.2-1) and then stop counting. The SS shall use the retrieved counter values at Time Point A and Time Point B, as well as the recorded number of transmitted sidelink packets (PSCCH, PSSCH and/or SDAP SDU) between Time Point A and Time Point B, to calculate the PSCCH probability of miss-detection, the PSSCH BLER and the SDAP SDU loss, respectively.

Figure G.5.2-1: Proposed Test Method for PSCCH/PSSCH performance using sidelink HARQ feedback

According to both the test method described in this section and Figure G.5.2-1, the PSCCH probability of miss-detection can be defined as follows when ACK/NACK HARQ or NACK-only HARQ is applied, respectively.

Similarly, we can define the PSSCH BLER as follows:

Finally, we can define the SDAP SDU loss as follows:

Where:

P^MD = Probability of Miss-Detection

BLER = Block Error Rate

Loss_{SDAP_SDU} = SDAP SDU Loss rate

NACK_Counter = number of NACK feedback recorded by the SS

DTX_Counter = number of DTX observed by the SS

SDAP_SDU_Counter = number of SDAP SDUs all of whose corresponding PSSCHs are correctly received (i.e. the SS receives positive acknowledgements on all corresponding PSFCHs)

T = 10 seconds stability window

PSCCH_Transmitted = Transmitted number of PSCCH transport blocks counted by the SS

PSSCH_Transmitted = Transmitted number of PSSCH transport blocks counted by the SS

STCH_SDU_Transmitted = Transmitted number of STCH PDCP SDUs counted by the SS

MNAS = Minimum Number of Active Subframes, as per Table G.5.4-1 and Table G.5.5-1 for performance tests with throughput and probability of miss-detection, respectively