A Novel Rate Adaptation Technique for Improving the Performance of Wireless Networks

Abstract

ABSTRACT newline newlineIEEE 802.11 technology provides a low-cost wireless networking solution. In the last few years the demand for high data rate wireless local area networks increased rapidly, due to the proliferation of mobile devices such as laptops, smart phones and tablet PCs. This has driven the widespread deployment of IEEE 802.11 wireless networks to provide Internet access. Wireless channel is extremely variable and can be affected by a number of different factors, such as collisions, multipath fading and signal attenuation. The IEEE 802.11 standard conformant wireless communication stations have multi-rate transmission capability. To achieve greater communication efficiency, multi-rate capable stations use rate adaptation to select appropriate transmission rate according to variations in the channel quality to match the wireless channel conditions. newline newlineThis thesis deals with improving the performance of the wireless networks using a novel rate adaptation technique in the wireless networking environment. The performance metrics used are throughput, delay, loss ratio and jitter. In this thesis two different techniques are attempted. In the first technique a closed loop rate adaptation method based on the channel quality estimation and the channel stability is developed and tested. This technique selects the type of the rate adaptation based on the channel quality estimated by the destination node. If the channel quality estimated is bad then the Multi Rate Retry mechanism, an open loop rate adaptation scheme is performed which selects the rate based on local channel estimation without getting any feedback from the destination. If the channel quality is good then the stability of the dynamic environment is checked using the coherence time. If the channel is stable for the coherence time the rate adaptation is performed by the source based on the rate of the acknowledgement frame received from the destination. If the channel is unstable for the coherence time, then there may be loss of frames. RTS probing method is use