The Study Of Multi-rate And Multi-channel MAC Protocol In Wireless Local Area Network

As the publication of a series of IEEE 802.11 standards, wireless area local network becomes a promising solution to Internet due to its flexibility, broadband and wireless access. Since MAC protocol has significant impact on the performance of wireless networks, designing an effective MAC protocol becomes more important.Many MAC protocols use rate-adaptive mechanism to adapt the wireless channel, thus there are multiple rates exist in the single network. Many researchers have analyzed the performance of multi-rate MAC. However, they cannot consider the impact of channel error. Thus, one of major works in this thesis is to analyze the performance of Multi-rate IEEE 802.11 MAC over Gaussian and fading channel.In addition, current IEEE 802.11 faces the performance anomaly in multi-rate network. This thesis evaluates the various methods to solve the performance anomaly, and then proposes a new method based on collision avoidance, known as Collision Avoidance Multi-rate MAC (CAMR-MAC). The simulation results show that CAMR-MAC can effectively improve the performance of multi-rate network and guarantee the temporal fairness in the network.Finally, we take DCA (Dynamic Channel Assignment) for example to analyze the throughput of Multi-channel MAC based on dedicated control channel. Besides, in this multi-channel MAC protocol, the collision in control channel greatly reduces the utilization rate of data channel. Thus, we propose a DCA based on adaptive window, known as Adaptive Window DCA (AW-DCA). The results show that AW-DCA can effectively enhance the performance of network. However, AW-DCA is based on the contention access, which can not fully avoid the collision. Thus, we propose a new method called Collision Avoidance DCA (CA-DCA). The simulation results show that CA-DCA has better performance than that of AW-DCA.