Delay Performance of the Multiuser MISO Downlink

TL;DR

This paper analyzes the delay performance of multiuser MISO downlink channels, revealing how the number of users impacts data rates and delay, and identifying the optimal user count based on traffic and delay needs.

Contribution

It introduces a stochastic network calculus approach to quantify queueing delay in multiuser MISO systems, highlighting the trade-off between multiplexing and beamforming gains.

Findings

Optimal number of users depends on traffic and delay constraints.

Increasing users reduces individual data rates and increases delay.

Trade-off between multiplexing gain and beamforming gain is quantifiable.

Abstract

We analyze a MISO downlink channel where a multi-antenna transmitter communicates with a large number of single-antenna receivers. Using linear beamforming or nonlinear precoding techniques, the transmitter can serve multiple users simultaneously during each transmission slot. However, increasing the number of users, i.e., the multiplexing gain, reduces the beamforming gain, which means that the average of the individual data rates decreases and their variance increases. We use stochastic network calculus to analyze the queueing delay that occurs due to the time-varying data rates. Our results show that the optimal number of users, i.e., the optimal trade-off between multiplexing gain and beamforming gain, depends on incoming data traffic and its delay requirements.