Delay Analysis for Max Weight Opportunistic Scheduling in Wireless Systems

TL;DR

This paper analyzes the delay performance of max-weight opportunistic scheduling in multi-user wireless systems, demonstrating order-optimal delay bounds under certain conditions and exploring effects of multi-rate models.

Contribution

First to establish order-optimal delay bounds for max-weight policies in multi-user wireless systems with independent arrivals and channels.

Findings

Average delay is order-optimal and does not grow with network size under certain conditions.

Delay increases with network size in multi-rate transmission models due to residual packets.

Max-weight scheduling stabilizes networks and achieves maximum throughput.

Abstract

We consider the delay properties of max-weight opportunistic scheduling in a multi-user ON/OFF wireless system, such as a multi-user downlink or uplink. It is well known that max-weight scheduling stabilizes the network (and hence yields maximum throughput) whenever input rates are inside the network capacity region. We show that when arrival and channel processes are independent, average delay of the max-weight policy is order-optimal, in the sense that it does not grow with the number of network links. While recent queue-grouping algorithms are known to also yield order-optimal delay, this is the first such result for the simpler class of max-weight policies. We then consider multi-rate transmission models and show that average delay in this case typically does increase with the network size due to queues containing a small number of "residual" packets.