Distributed Medium Access Control with SDMA Support for WLANs

Sheng ZHOU  Zhisheng NIU  

Publication
IEICE TRANSACTIONS on Communications   Vol.E93-B   No.4   pp.961-970
Publication Date: 2010/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E93.B.961
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Terrestrial Radio Communications
Keyword: 
MIMO,  WLAN,  medium access control (MAC),  spatial division multiple access (SDMA),  IEEE 802.11n,  

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Summary: 
With simultaneous multi-user transmissions, spatial division multiple access (SDMA) provides substantial throughput gain over the single user transmission. However, its implementation in WLANs with contention-based IEEE 802.11 MAC remains challenging. Problems such as coordinating and synchronizing the multiple users need to be solved in a distributed way. In this paper, we propose a distributed MAC protocol for WLANs with SDMA support. A dual-mode CTS responding mechanism is designed to accomplish the channel estimation and user synchronization required for SDMA. We analytically study the throughput performance of the proposed MAC, and dynamic parameter adjustment is designed to enhance the protocol efficiency. In addition, the proposed MAC protocol does not rely on specific physical layer realizations, and can work on legacy IEEE 802.11 equipment with slight software updates. Simulation results show that the proposed MAC outperforms IEEE 802.11 significantly, and that the dynamic parameter adjustment can effectively track the load variation in the network.