Iterative Resolution and Optimal Scheduling of Blind Retransmissions for Multi-user URLLC

Industrial applications have challenging requirements for wireless communication systems in terms of reliability and latency. Addressing these requirements without excessively consuming radio resources has led to the design of new communication services and resource management schemes. Blind repetition has been proposed as one of the promising features to increase reliability while satisfying the latency constraint by avoiding extra delays existent on feedback-based retransmission schemes. Moreover, performing transmissions of multiple users on the shared resources simultaneously could enhance the resource efficiency, by applying successive interference cancellations for decoding. In this work, we propose a scheduling scheme of multiple blind retransmissions on shared resources, which is based on an optimal shared resources allocation and on an iterative collision resolution algorithm. In addition, following the characterization of the iterative resolution chain, we refine our solution to increasing its robustness against transmission errors. Numerical simulations confirm that the proposed shared resource allocation design requires fewer shared radio resources to achieve the same reliability target compared with the scheme based on non-scheduled blind retransmission on shared resources.

I. Introduction

The fifth-generation (5G) New Radio (NR) cellular network is expected to support the forthcoming machine-centric mission-critical communications [1], e.g. remote industrial automation [2], vehicular-to anything (V2X) communication [3], and haptic communication [4]. Ultra-reliable low latency communication (URLLC) [5] is one of the new service classes in 5G NR that aims to meet the stringent requirements of the machine to machine communication which targets 1 ms one-way latency deadline for transmitting a packet while guarantees reliability of 99.999%. However, the standard protection mechanisms like Hybrid Automatic Repeat Request (HARQ) [6] and retransmissions at Radio Link Control (RLC) hardly meet the critical requirements of the URLLC, because the latency would increase by the feedback round-trip-time (RTT) as the sender needs to wait for a non-acknowledgement (NACK) signal before performing retransmission. Consequently, the redesign of novel communication components and corresponding resource management methods is of vital importance for the success of the URLLC service.