Research And Improvement Of Backoff Mechanism And Frame Aggregation In IEEE802.11 MAC

With the rapid development and popularization of mobile terminals, the age of mobile Internet has arrived.Under this background,the Wireless Local Area Network has got more and more attention and is widely used in people’s life and work.IEEE 802.11 WLAN as the main protocol of WLAN, using both the 2.4GHz and 5GHz ISM band specifies a set of media access control(MAC) and physical layer for implementing wireless local area network.802.11 n is adopted in 2009, whose theoretical rate has reached 600 Mbps.It has become the mainstream the industry.Nowadays,the widespread of voice and video make big challenge to wireless technology.As we all know, the voice application is very sensitive to the throughput and latency of WLAN; the video applications is very sensitive to throughput of WLAN.In order to provide QoS guarantee,IEEE come up with 802.11 e,which aims to guarantee the QoS of services just like voice and video.However, due to IEEE 802.11 e introduces many new concepts and the higher hardware requirements, many manufacturers don’t support it.This thesis proposes two methods to guarantee the Qo S of delay and throughput sensible services.In chapter 3,author proposes a backoff mechanism for DCF that takes the node priority as a reference factor in selecting backoff value.A Markov chain model is deployed and used to analyze and evaluate the mechanism performance. Besides, the analytical model is validated with NS2 simulation results. The results show that the proposed mechanism can provide better QoS guarantee for high priority nodes in terms of throughput and delay.In chapter 4,author proposes access control mechanism which combines IEEE802.11 e EDCA with Frame Aggregation.This mechanism regards a certain AC as the object of research.A Markov chain model is used to analyze and calculate the delay and throughput of this AC.NS2 is used to evaluate the performance of the mechanism.The results show that this access control mechanism can provide QoS guarantee for delay and throughput sensible services.