Research And Improvement On MAC Layer Of WLAN

Wireless Local Area Network (WLAN) technology is widely used and becomes more and more popular. But the rapid development of WLAN has not yet broken the bottleneck that the low transmission speed hinders the further development of WLAN. Thus, this paper concentrates on how to raise transmission speed of WLAN which is an attractive topic in the field of wireless research.This article mainly focuses on IEEE 802.11 standards and do some research on IEEE802.11n MAC layer from both theory and practice.There are six parts in this thesis:First, history and key technologies as well as development of WLAN are presented. By analyzing its advantages, WLAN will sure be used more widely.But its low speed is also introduced as shortcoming and it is also what we concern.Secondly we introduce the structure of WLAN.At the beginning we introduce the communication characteristic and then mainly show WLAN topology structure.Third, 802.11 MAC protocol is introduced, including frame structure and types,especially MAC access mechanism:DCF andPCF as well as technologies which can improve MAC performance.Then we give analysis of aggregation and fragmentation(FA). Then, two means based on adaptive FA is presented:one is Adaptive FA based on Lookup table(LT-AFA) and the other is AFA based on ARF (ARF-AFA). Optimal fragment size is also shown.Most important, we introduce details about the two means above.Following, we simulate with network simulation tool NS2 and Iperf, and then give out simulation results as well as analysis,and give measurement results in both office and industrial enviroments. Both simulations and measurments prove the two means of new MAC protocol raise the throughput of WLAN system.Last, summarizing the contribution of this thesis and direction of further research.