Optimal Tradeoff between Reliability and Latency with Finite Blocklength for Many Access Channel

With the evolution of mobile network towards "Digital twin, ubiquitous intelligence", the massive low latency high reliability short packet communication will become more prevalent for beyond 5G wireless networks. One of the fundamental problems in this scenario is to fulfill both high reliability and low latency for short blocklength. We address this issue by formulating it as maximization of probability of success under the reliability and latency constraints, in which we optimize the decoding success probability and minimizing demodulation reference signal (DMRS) collision probability jointly. The optimal blocklength/channel use is obtained by the bi-level optimization and the proposed golden section search based method. Numerical results verified the tradeoff between different assumptions. And it is found that larger blocklength/channel use not only leads to higher latency, but also increase the DMRS collision probability.