Prioritized S-ALOHA for URLLC

Abstract

Ultra reliable low latency communication (URLLC) is one of the main goals in 5G. URLLC requires highly reliable and low latency transmission of safety critical and control packets. Slotted ALOHA forms one of the widely used access schemes in cellular communication. In this paper, we study the performance of URLLC packet transmissions utilizing slotted ALOHA and propose a prioritized access mechanism to provide low latency and high reliability transmission of delay critical packets. We consider two types of traffic, namely, regular traffic and URLLC traffic. URLLC packets have stringent delay requirements, thus, they are provided high priority access to the channel. Via analytical formulation, we obtain the packet delay distribution function for both URLLC and regular packets and formulate an optimization problem to maximize the reliability of regular packets given that the URLLC packets meet their required reliability threshold. Results show that by enabling prioritized access to URLLC packets, their reliability requirements can be met, while at the same time, regular packet transmission can make most use of the remaining channel.