Low-latency communication plays an increasingly important role in
delay-sensitive applications by ensuring the real-time exchange of information.
However, due to the constraints on the maximum instantaneous power, bounded
latency is hard to be guaranteed. In this paper, we investigate the
reliability-latency-rate tradeoff in low-latency communications with
finite-blocklength coding (FBC). More specifically, we are interested in the
fundamental tradeoff between error probability, delay-violation probability
(DVP), and service rate. Based on the effective capacity (EC) and normal
approximation, we present several gain-conservation inequalities to bound the
reliability-latency-rate tradeoffs. In particular, we investigate the
low-latency transmissions over an additive white Gaussian noise (AWGN) channel,
over a Rayleigh fading channel, with frequency or spatial diversity, and over a
Nakagami-m fading channel. To analytically evaluate the
quality-of-service-constrained low-latency communications with FBC, an
EC-approximation method is further conceived to derive the closed-form
expression of quality-of-service-constrained throughput. For delay-sensitive
transmissions in which the latency threshold is greater than the channel
coherence time, we find an asymptotic form of the tradeoff between the error
probability and DVP over the AWGN and Rayleigh fading channels. Our results may
provide some insights into the efficient scheduling of low-latency wireless
communications in which statistical latency and reliability metrics are
adopted.Comment: Submitted to IEEE Trans. Inf. Theor