Design And Performance Analysis Of MAC Protocol Or Wirless LAN

In recent years, much interest has been involved in the design of wireless LAN (WLAN) . In the medium access control (MAC) layer of WLAN, there is only one logical channel designed, so different mobile stations will contend for the control of the transmission media. Then MAC layer protocol should provide efficient contending mechanism for the users to share the limited spectrum resources. Nowadays, the DCF and EDCF, which supports different kinds of service, become the basis of the IEEE802.11 standard on the MAC layer.However, it is observed that the primary deficiency of the current MAC protocol is to use the binary increasing-only mechanism. DCF absorbs the number of collisions as the condition to derive the contention window (CW) . Whereas the transmission history is not the direct factor influencing the future collision probability, it is actually used to estimate the number of active nodes in the Wireless LAN, which dominates the frame delay and system performance. The major advantage of DCF is simplicity and distributed algorithm, which are important in the Wireless LAN.Fortunately, in the infrastructure wireless LAN, it is not too difficult to get partial global information. Then we can combine the distributed and central control algorithms to get more credits. In the infrastructure Wireless LAN, the network core is Access Point (AP) , and all the mobile stations cooperate under the control of the AP. In this case AP can collect the distributed contention information and derive the optimized CW based on the number of the active mobile stations in the next contention cycle. It will broadcast the control information if necessary...