The University of British Columbia

Wireless local area networks (WLANs) have become a ubiquitous high-speed data access technology. The recent 802.11n proposal further increases the transmission rate by using the multiple-input-multiple-output (MIMO) technique. Multiple antennas can be used to achieve a performance gain by either increasing the transmission reliability through spatial diversity or increasing the transmission rate through spatial multiplexing. This new characteristic at the wireless physical layer requires the corresponding adaptation at the medium access control (MAC) layer to reach the best performance gain. This paper proposes a cross-layer optimization framework for jointly optimizing the MIMO configuration at the physical layer and the persistent probabilities for different classes of multimedia traffic at the MAC layer with slotted Aloha. A distributed algorithm NUM-D based on dual decomposition is proposed. Numerical results are compared with a simplified algorithm NUM-S to show the effectiveness of the proposed methods.