Improving Access Protocol to Effectively Support Smart Antenna in Wireless LAN

Smart antenna is a promising technology to improve the capacity of wireless networks. Implementing smart antenna in WLAN urgently demands new multiple access protocols. In this paper we propose a multiple access protocol for WLAN to effectively support smart antenna. The proposed protocol makes use of the hybrid superframe structure of polling and contention, which is illumed from IEEE 802.11, and distinguishes the stations residing within the AP's broadcast range from those out of the broadcast range. For the stations residing within the AP's broadcast range, the AP uses polling to transmit in broadcasting mode; for those residing out of the AP's broadcast range but in its directional range, the AP uses contention-based method to transmit in beamforming mode. We have evaluated and optimized the protocol performance against its parameters by simulation. To show the efficiency of the proposed protocol, we also compare it with other protocols in average packet delay and throughput. The simulation results show that the proposed protocol performs well; especially, under heavy traffic load, it achieves the smallest average delay and the highest throughput.