Distributed Medium Access Control with SDMA Support for WLANs

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.

[1]  Ilenia Tinnirello,et al.  A space-division time-division multiple access scheme for high throughput provisioning in WLANs , 2005, IEEE International Conference on Communications, 2005. ICC 2005. 2005.

[2]  Yang Xiao,et al.  Throughput and delay limits of IEEE 802.11 , 2002, IEEE Communications Letters.

[3]  Weihua Zhuang,et al.  A Distributed Multi-User MIMO MAC Protocol for Wireless Local Area Networks , 2008, IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference.

[4]  Leandros Tassiulas,et al.  Efficient media access protocols for wireless LANs with smart antennas , 2003, 2003 IEEE Wireless Communications and Networking, 2003. WCNC 2003..

[5]  Jing Zhu,et al.  On Optimal QoS-aware Physical Carrier Sensing for IEEE 802.11 Based WLANs: Theoretical Analysis and Protocol D esign , 2008, IEEE Transactions on Wireless Communications.

[6]  Ari T. Alastalo,et al.  Smart-antenna operation for indoor wireless local-area networks using OFDM , 2003, IEEE Trans. Wirel. Commun..

[7]  James C. Yee,et al.  Understanding wirele ss LAN performance trade-offs , 2002 .

[8]  Rohit U. Nabar,et al.  Introduction to Space-Time Wireless Communications , 2003 .

[9]  Georgios B. Giannakis,et al.  Cross-Layer combining of adaptive Modulation and coding with truncated ARQ over wireless links , 2004, IEEE Transactions on Wireless Communications.

[10]  Zhisheng Niu,et al.  On the Impact of Carrier Frequency Offsets in OFDM/SDMA Systems , 2007, 2007 IEEE International Conference on Communications.

[11]  A. Girotra,et al.  Performance Analysis of the IEEE 802 . 11 Distributed Coordination Function , 2005 .

[12]  Yuguang Fang,et al.  Enhancing the performance of medium access control for WLANs with multi-beam access point , 2007, IEEE Transactions on Wireless Communications.

[13]  Khaled Ben Letaief,et al.  Joint Channel State Based Random Access and Adaptive Modulation in Wireless LAN with Multi-Packet Reception , 2007, 2007 IEEE International Conference on Communications.

[14]  Luis Alonso,et al.  Multiuser MAC Protocols for 802.11n Wireless Networks , 2009, 2009 IEEE International Conference on Communications.

[15]  Periklis Chatzimisios,et al.  IEEE 802.11 packet delay-a finite retry limit analysis , 2003, GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489).

[16]  Liesbet Van der Perre,et al.  Space Division Multiple Access for Wireless Local Area Networks , 2006 .

[17]  G.B. Giannakis,et al.  Carrier frequency offset estimation for OFDM-based WLANs , 2001, IEEE Signal Processing Letters.