The Research And Implementation Of FastRoaming Based On IEEE 802.11n MAC Layer

With the rapid development of wireless communication product, performance of traditional wireless LAN in transmission speed, coverage, security, mobile scope and roaming time have been unable to meet higher requirments of these new products. Therefore,the IEEE developed the 802.11n protocol to adapt to the new communication requirements in 2003.Based on IEEE 802.11n Draft 2.0,author will research FrameAggregation,TXOP, BlockACK, PSMP, network connectivity mechanism and so on.Then author will research how to reduce the time in the MAC layer network roaming to implement the FastRoaming.The roaming of WLAN MAC layer have three sections.They are discovery process, reauthentication process and reassociation process. A lot of researching results suggest that the delay in discovery process account for more than 90% present of the MAC layer roaming delay,so the reducing extent of roaming time is the biggest in this process. This paper presents a direct connect target AP mechanism (DCTA) through the establishment of neighbors map (NM) to reduce the number of scanning channel at first, in the second stage, before reauthentication process and reassociation process the mechanism will always maintain a connection for the target AP, to ensure that terminal equipment needs roaming judgement can be directly connected to the target AP. After the actual certification test, the average roaming time in fast roaming module added the mechanism account for 40.1% of the unadded , to a certain extent, reduce the roaming time.