5G Radio Access Protocols with Multi-User Detection for URLLC

In this paper we present both collision-free and contention-based radio access protocols for sporadic small data packet transmissions in the uplink of 5G. We compare them by computer simulations with respect to throughput and a joint latency plus reliability metric. Based on that we analyze the tradeoff between number of transmission attempts and advanced collision resolution. In a second study we investigate the impact of multi-user detection on the performance. The key outcome of our study is that contention-based radio access combined with multi-user detection is well suited for URLLC applications with required error rates down to 10-5 in a low traffic load scenario.