Scan Based On 802.11mac Layer Switching Mechanism In The Algorithm

WLAN is the product of the combination of computer internet and wireless communication technology in the 1990s .It access network with wireless channel .WLAN provides some substantial tricks to the communication mobility , personal and multi-media using .IEEE 802.11 is developed from Ethernet among various of WLAN standards. As it is simple and reliable, IEEE 802.11 is supported widely. It becomes the focus, because its fastest data processing is 11Mbps which would support most of the network presently.At the same time, the needs of mobility data communication is increasing . People are not satisfied with the limitation of mobility area, which is provided by the single Access Point when they access WLAN. It is proved be a main point that how to handoff machinist through MAC layer to expend mobility area and ensure the data of communication.However, how the handoff is accomplished is not defined in the 802.11 protocol, It only gives logically that a handoff of a MN be devised into 3 sections . They are discovery process, reauthentication process, reassociation process . With the experimental analysis this logical process, a lot of researching results suggest that the probe delay is almost 90% present of the MAC layer handoff delay. That is to say, the effective way in reducing the probe delay in the MN's discovery process would improve the performance of MAC layer handoff greatly.Follow the reasons above; the paper is mainly about the research on the fatal technologies and mechanism in discovery process in handoff. The author provides Selective-scan algorithm and Neighbor- Graph-scan algorithm. With the deeply analysis and result on the present Full-scan algorithm. Further more; Neighbor Graph scan algorithm is algorism could be divided into two parts on the different way of Neighbor Graph. They are: MN forecast AP and location registered in server.In order to analysis the performance of the algorithm ,the author simulated the Full-scan algorithm, Selective-scan algorithm and NG-scan algorithm using Opnet modeler .And the comparison among the delays and packet losing are analyzed in paper.