A High Reliability and Low Latency Distributed Random Access Scheme for Industrial IoT Networks

High throughput with constraints of high reliability and low latency brings a great challenge to random access (RA) protocol. A novel high reliability and low latency distributed random access (DiRA) scheme is proposed for RA systems with multiple access points (APs) and a central processing unit (CPU) to meet the requirements of the industrial Internet of Things (IIoT) networks. IIoT devices send packets to APs with the irregular repetition slotted ALOHA (IRSA) protocol. A comprehensive packet collision resolution scheme is proposed and employed at APs, which effectively combined the intra-slot, inter-slot, AP-CPU cooperation-based network-aided, and virtual multi-input multi-output (V-MIMO) packet collision resolution schemes. Then, the optimization problem of the temporal degree distribution of IRSA is formulated and solved under reliability and latency constraints. Numerical results show that the proposed protocol improves throughput and achieves a carried density of devices 257%, 292%, and 328% times that of the full cooperation-based RA scheme, for a target access success probability of 99.999% and a frame duration of 40 slots, for 4, 9, and 16 APs respectively.