A Design Of MAC Layer Scheme To Confront OBSS Problem In WLAN

With the development of new IEEE802.11 ac network, overlapping phenomenon of BSSs with different operating frequency band will become more and more common. Adjacent BSS whose main channel is different can interact control frames in their respective primary channel and then use the traditional channel bonding technology to bind the available subchannels for data transmission. Specific channel binding technology has both static and dynamic ways, but the two channel binding mechanisms will bring the hidden terminal problem in secondary channel, the collision of data will lead to a waste of spectrum resource; On the other hand if the main channel of adjacent BSS is the same, according to the IEEE802.11 ac standard, all the expansion bands of the 802.11 ac BSS must remain idle when the main channel is occupied, that also leads to a waste of spectrum resource. In summary, the study of designing appropriate MAC protocol scheme under dense network environment to improve the utilization of spectrum resources and to improve the throughput of OBSS system is particularly important.This paper first studies the design of MAC layer scheme to solve the problem of spectrum utilization when the primary channel of adjacent BSS is not the same. We first analyze the expanded continuous channel binding mechanism in 802.11 ac protocols and compare the performance of the static or dynamic channel binding mechanism. Then we introduce the enhanced protection mechanism to resolve hidden terminal problem in secondary channel appearing in continuous channel binding mechanism. Then we design a MAC scheme based on enhanced protection mechanisms to solve the problem of spectrum utilization. The simulation results show that, the designed scheme with enhanced protection feature of MAC layer can effectively alleviate the hidden terminal problem in secondary channel, avoiding unnecessary collisions, and further improve network throughput.Secondly we study the scheme of MAC layer to solve the problem of spectrum utilization when the primary channel of adjacent BSS is the same. We first analyze the performance of OBSS system under the 802.11 ac protocol, and then propose a Channel access algorithm based on Virtual-Primary channel to optimize the throughput of the OBSS system. The simulation results show that the channel access algorithm based on Virtual-Primary channel has greatly enhanced spectrum efficiency OBSS system.In summary, aimed at the shortage problem of spectrum utilization we put forward the corresponding MAC scheme to optimize the 802.11 ac MAC layer protocol, raise the utilization ratio of the frequency spectrum of OBSS system.