Enhancements of PUSCH repetitions for URLLC in licensed and unlicensed spectrum

Le, Trung-Kien; Salim, Umer; Kaltenberger, Florian
ISWCS 2021, 17th International Symposium on Wireless Communication Systems, 6-9 September 2021, Berlin, Germany

Ultra-reliable low-latency communication (URLLC) is specified in 5G New Radio to serve the applications and services with the strict requirements of reliability and latency. The URLLC operation is in licensed spectrum then extended to unlicensed spectrum to support new use cases in the industrial scenario. This requires new features in physical layer to make URLLC work with the strict requirements in both licensed and unlicensed spectrum. This paper focuses on the design of physical uplink shared
channel (PUSCH) repetitions for URLLC. In PUSCH repetition, the nominal PUSCH repetitions might be segmented into the smaller actual repetitions due to uplink/downlink (UL/DL) directions in time division duplex (TDD) configuration or slot boundary. This segmentation causes a degradation of the URLLC performance due to a smaller number of valid symbols for PUSCH repetitions, a drop of the repetition in an orphan symbol and an increase of listen before talk (LBT) overhead. To enhance the URLLC performance, two schemes are proposed. The first scheme deals with segmentation due to UL/DL directions by dynamically switching the chosen semi-static DL symbols to UL symbols. The second scheme deals with orphan symbols by transmitting signal in these symbols in order to maintain a continuous PUSCH transmission and avoid an additional LBT. The results show an improvement of URLLC performance in licensed and unlicensed spectrum by applying these two schemes.

Systèmes de Communication
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