Flow-Level Stability of Wireless Networks: Separation of Congestion Control and Packet Scheduling

TL;DR

This paper demonstrates that flow-level stability in wireless networks can be achieved with simple congestion control mechanisms, using queue length differences for scheduling, challenging the necessity of alpha-fair congestion control.

Contribution

It shows that stability does not require alpha-fair congestion control, using a fixed window scheme and queue length differences for scheduling.

Findings

Stability achieved with simple fixed window congestion control.

Queue length differences can effectively guide scheduling.

Alpha-fair congestion control is not necessary for stability.

Abstract

It is by now well-known that wireless networks with file arrivals and departures are stable if one uses alpha-fair congestion control and back-pressure based scheduling and routing. In this paper, we examine whether ?alpha-fair congestion control is necessary for flow-level stability. We show that stability can be ensured even with very simple congestion control mechanisms, such as a fixed window size scheme which limits the maximum number of packets that are allowed into the ingress queue of a flow. A key ingredient of our result is the use of the difference between the logarithms of queue lengths as the link weights. This result is reminiscent of results in the context of CSMA algorithms, but for entirely different reasons.