Downlink Sensing in 5G-Advanced and 6G:SIB1-assisted SSB Approach

This paper investigates the potential to leverage existing 5G NR signals for network-side integrated sensing and communications (ISAC). In general, the synchronization signal block (SSB) is a suitable candidate for always-on downlink sensing, due to its frequent periodical availability and because of its beam-sweeping nature. However, as this work demonstrates, using only the SSB has challenges related to radar ambiguity while being also limited in both distance and velocity resolution due to limited bandwidth and per-beam time duration, respectively. A novel solution is then introduced by combining SSB with downlink control information (DCI) and system information block 1 (SIB1) symbols. The corresponding implications and variants how SIB1 is optimized and configured are discussed, covering both 5G evolution and potential 6G solutions. The performance of the proposed approach is also assessed through realistic numerical evaluations at both 3.5 GHz and 28 GHz network deployments, and shown to yield up to 25 dB suppression in radar peak sidelobe level (PSL) compared to SSB-only based range-velocity profile. Also considerable improvements in the sensing resolution in the order of 120–190% are demonstrated.