Ultra-Reliable and Low-Latency Multiple-Antenna Communications in the High SNR Regime

Emerging time-sensitive applications such as automated driving, factory automation, and telesurgery have stimulated an increased interest in Ultra-Reliable and Low-Latency Communications (URLLC). Meanwhile, Multiple-Input Multiple-Output (MIMO) techniques have played a vital role in radio access networks since the 2000s, due to their spatial multiplexing and diversity gains over fading channels. Thus, it is of interest to consider the fundamental performance limits of URLLC operating over MIMO channels. In this letter, we consider this problem in the asymptotic regime of high Signal-to-Noise Ratio (SNR) for short packets involving finite-blocklength codes. In particular, we show that a fundamental tradeoff exists among service capability, latency, and error probability in the high SNR regime. We present a piecewise linear gain conservation equation to characterize this cross-layer tradeoff, which is also validated by extensive numerical results.