Leader-Contention-Based User Matching for 802.11 Multiuser MIMO Networks

TL;DR

MIMOMate is a leader-contention-based MAC protocol for MU-MIMO networks that optimally matches clients based on channel characteristics, significantly improving throughput and fairness over traditional contention-based methods.

Contribution

This paper introduces MIMOMate, a novel MU-MIMO MAC protocol that reduces contention overhead and enhances throughput by matching clients according to their channel conditions.

Findings

Achieves 1.42x and 1.52x throughput gains in prototype tests.

Ensures fair sharing of transmission opportunities among users.

Compatible with legacy 802.11 devices.

Abstract

In multiuser MIMO (MU-MIMO) LANs, the achievable throughput of a client depends on who are transmitting concurrently with it. Existing MU-MIMO MAC protocols however enable clients to use the traditional 802.11 contention to contend for concurrent transmission opportunities on the uplink. Such a contention-based protocol not only wastes lots of channel time on multiple rounds of contention, but also fails to maximally deliver the gain of MU-MIMO because users randomly join concurrent transmissions without considering their channel characteristics. To address such inefficiency, this paper introduces MIMOMate, a leader-contention-based MU-MIMO MAC protocol that matches clients as concurrent transmitters according to their channel characteristics to maximally deliver the MU-MIMO gain, while ensuring all users to fairly share concurrent transmission opportunities. Furthermore, MIMOMate elects the leader of the matched users to contend for transmission opportunities using traditional 802.11 CSMA/CA. It hence requires only a single contention overhead for concurrent streams, and can be compatible with legacy 802.11 devices. A prototype implementation in USRP-N200 shows that MIMOMate achieves an average throughput gain of 1.42x and 1.52x over the traditional contention-based protocol for 2-antenna and 3-antenna AP scenarios, respectively, and also provides fairness for clients.