Performance Guarantees of Distributed Algorithms for QoS in Wireless Ad Hoc Networks

TL;DR

This paper analyzes the performance of distributed algorithms for ensuring quality-of-service in wireless ad hoc networks, establishing bounds on their efficiency relative to centralized solutions based on local information.

Contribution

It quantifies the tradeoff between decentralization and performance in distributed scheduling algorithms for wireless networks, providing optimal bounds for primary interference and line networks.

Findings

Distributed algorithms can approximate centralized performance within a factor depending on local neighborhood size.

For primary interference, performance degrades gracefully with the radius of local information.

Row constraints are within a factor of 3 of optimal for line networks under the protocol interference model.

Abstract

Consider a wireless network where each communication link has a minimum bandwidth quality-of-service requirement. Certain pairs of wireless links interfere with each other due to being in the same vicinity, and this interference is modeled by a conflict graph. Given the conflict graph and link bandwidth requirements, the objective is to determine, using only localized information, whether the demands of all the links can be satisfied. At one extreme, each node knows the demands of only its neighbors; at the other extreme, there exists an optimal, centralized scheduler that has global information. The present work interpolates between these two extremes by quantifying the tradeoff between the degree of decentralization and the performance of the distributed algorithm. This open problem is resolved for the primary interference model, and the following general result is obtained: if each node knows the demands of all links in a ball of radius $d$ centered at the node, then there is a distributed algorithm whose performance is away from that of an optimal, centralized algorithm by a factor of at most $(2d+3)/(2d+2)$. The tradeoff between performance and complexity of the distributed algorithm is also analyzed. It is shown that for line networks under the protocol interference model, the row constraints are a factor of at most $3$ away from optimal. Both bounds are best possible.