Abstract:Based on the research of IEEE802.11,referring to information related to the channel access control of Ad hoc network and analyzing the strongpoint and shortcoming of IEEE802.11, we provide some kinds of new improved methods for IEEE8 02.11 DCF to improve the performance of the system. The main work of this paper includes the following several aspects:1. Based on analyzing the shortcoming of the BEB backoff mechanism used in IEEE802.11 and referring to related improved methods, such as MILD,EIED and so on, we put forward a new backoff mechanism which is based on the status of the channel. This method is based on the busy or idle degree of the channel to certain the parameter of the contention window then can relieve the unfairness during the period of the channel access and enhance the throughput of the system.2. After analyzing the problem of the hidden terminal,exposed terminal and blocking in IEEE802.11's channel ac cess control, we modify the mechanism of DCF.During the period of deferring, we detect the channel to avoiding the false blocking. At the same time, based on the status of receiving and sending RTS/CTS we decide to transfer data parallelly to improve throughput.3. Modifying the threshold of the retransmission for RTS/CTS and DATA packet in IEEE802.11, an adaptive mechanism is used to set the threshold of the retransmission, so that the probability of packet loss is minimized and TCP's congestion control mechanism is triggered fewer.4. The NS2 network simulator is used to simulate the modified scheme. The results of the simulation show that with the modified scheme, the throughput of network is better than IEEE802.11. In this paper, we take into account the shortcoming of the IEEE802.11 and put forward some improvement. The results of this paper providesa valuable reference for the research of Ad hoc network.