Throughput Improvement Via Smart Antenna and Link Adaptation Scheme for IEEE 802.11A Systems

Propagation delay spread and inter-symbol interference impact the transmission performance of WLAN systems. This paper presents performance enhancement using beamforming techniques operated at the access point. The performance by using omni-directional, switched beam system and phase array system in an indoor office are analyzed and compared. Based on the IEEE 802.11a physical layer specification, numerical simulations indicate that adopting directional antennae at the access point can increase diversity gain in non-line-of-sight propagations channels, while the packet error rate remains below 10-2. Besides, this paper also presents a link adaptation algorithm, based on the Ricean k-factor and signal to noise ratio, for throughput enhancement in IEEE 802.11a systems. Simulation results show that the average throughput reaches 33.7 Mbps in the signal-strength-based conventional algorithm, but rises to 43.1 Mbps when adopting the proposed scheme