An Optimization Framework for Demand-based Fair Stream Allocation in MIMO Ad Hoc Networks

Abstract

In this paper, we investigate the problem of scheduling flows for fair stream allocation (or, stream scheduling) in ad hoc networks in which the transmitter and receiver use multiple antennas called Multiple Input Multiple Output (MIMO) technology. Our main contributions include: i) the concept of stream allocation to flows based on their traffic demands or class, ii) stream allocation to flows in the network utilizing single user or multiuser MIMO communication, iii) achieving the proportional fairness of the stream allocation in the minimum possible schedule length, and iv) performance comparison of the stream scheduling in the network for single user and multiuser communication and the tradeoff involved therein. We first formulate demand-based fair stream allocation as an integer linear programming (ILP) problem whose solution is a schedule that is guaranteed to be contention-free. We then solve this ILP in conjunction with binary search to find a minimum length contention-free schedule that achieves the fairness goals. We show that an implementation of our algorithm for a number of sample topologies in fact yields minimum length schedules that achieve the fairness goals. We then give performance comparison results that show the benefit of multiuser MIMO links over single user links at higher traffic workloads in the network. Finally, we also give a greedy heuristic for stream scheduling and compare its performance with the ILP-based algorithm in terms of the fairness goals achieved in a given schedule length.