Short Packet Communications with Random Arrivals: An Effective Bandwidth Approach

Short packet transmission techniques have recently attracted substantial attention due to their potential of achieving low latency in emerging Industrial Internet of Things (IIoT). To this end, finite-blocklength coding is expected to play a central role in short packet communications. With the random arrival of short packets, there exists a fundamental tradeoff between reliability and latency in finite-blocklength coding based transmission systems. In this paper, we consider the reliability-latency tradeoff of short packet transmission over AWGN channels. More specifically, an effective bandwidth approach is adopted to obtain the delay violation probability given a hard delay constraint. We present an approximate but closed-form Quality-of-Service (QoS) exponent that bridges the delay violation probability of short packets and the error probability of finite-blocklength coding. Numerical results shall validate our theoretical analysis, which characterizes a performance limit of ultra-reliable and low latency communications (URLLC) over AWGN channels.