MU-MIMO Based SDMA Protocols for WLANs

Ruizhi Liao
Boris Bellalta, Núria Garcia and Miquel Oliver

IEEE 802.11 Wireless Local Area Networks (WLANs) are widely deployed and have been hugely successful in the last decade. However WLANs suffer from different problems, such as high link-layer protocol overheads and collisions, which lead to an effective throughput sometimes less than a half of the raw data rate that the Physical (PHY) layer can achieve. Multiple-Input Multiple-Output (MIMO) techniques are a good option to significantly improve the performance of WLANs by operating either in the Spatial Diversity mode (the sender transmits several duplicate data frames at the same time) or the Spatial Multiplexing mode (the sender transmits several independent data frames at the same time).

Although the single-user MIMO (SU-MIMO) has already been included in the IEEE amendment 802.11n-2009, the multi-user MIMO (MU-MIMO) communication has not been standardized, which gives us free space to explore and contribute to the new IEEE 802.11 amendment. In order to take full benefits that the MMO techniques have brought, the protocol modification of Distributed Coordination Function (DCF) at Medium Access Control (MAC) layer should be considered. In this thesis, we focus on designing a MAC protocol that supports the MU-MIMO WLANs communication at both UP and DOWN links (Space Division Multiple Access), based on which, we set up a cross-layer framework that considers and tunes parameters of different layers to provide the optimal performance.

In progress