Delay Performance of the Multiuser MISO Downlink under Imperfect CSI and Finite Length Coding

TL;DR

This paper analyzes the delay performance of multiuser MISO downlink systems using stochastic network calculus, highlighting the impact of imperfect CSI and finite blocklength coding on reliability and transmission rates.

Contribution

It provides a comprehensive analysis of delay performance under realistic conditions, deriving bounds and revealing that high reliability persists despite degradations.

Findings

Imperfect CSI and finite blocklength coding significantly reduce average transmission rates.

High reliability with respect to maximum delay is achievable if the average rate exceeds the arrival rate.

System behavior remains qualitatively similar to the ideal case despite practical impairments.

Abstract

We use stochastic network calculus to investigate the delay performance of a multiuser MISO system with zero-forcing beamforming. First, we consider ideal assumptions with long codewords and perfect CSI at the transmitter, where we observe a strong channel hardening effect that results in very high reliability with respect to the maximum delay of the application. We then study the system under more realistic assumptions with imperfect CSI and finite blocklength channel coding. These effects lead to interference and to transmission errors, and we derive closed-form lower and upper bounds on the resulting error probability. Compared to the ideal case, imperfect CSI and finite length coding cause massive degradations in the average transmission rate. Surprisingly, the system nevertheless maintains the same qualitative behavior as in the ideal case: as long as the average transmission rate is higher than the arrival rate, the system can still achieve very high reliability with respect to the maximum delay.