The Research On Multi-Channel WLAN Network Access Based On QoS

With the rapid popularization of mobile terminal equipment, wireless Internet access demand is bigger and bigger. While the wireless cellular network has high flexibility and mobility, however, the characteristic of the low rate and high prices can not satisfy the present popular multimedia service transmission. As wireless LAN (WLAN) network mode is simple and the characteristics of low rates, WLAN become the main way of wireless Internet access in People’s Daily life.WLAN MAC layer using the IEEE802.11protocol, mechanism of DCF model can provide good throughput and channel utilization, but the quality of service QoS support is insufficient. For this purpose, the IEEE802.11e EDCA mechanism is proposed, using access categories as the competitors of channel competition, because of each type of access categories occupy the whole channel at a time, one single channel of transmission way has been unable to meet the needs of more and more users accessing the Internet at the same time.OFDMA technique applied to WLAN, all the subcarriers will be divided into multiple sub-channels, which allows users to compete for the right to transfer data on different sub-channels. The collision occurs when a user competes for a sub-channel will not affect the user access to the other sub-channel. Multiple priorities based on OFDMA multi-channel EDCA access protocol, can reduce the overhead of WLAN system, and improve the throughput. EDCA protocol support contention Free bursting mechanism, make voice and video access category queue send multiple data frames after winning the contention of channel. Because the actual wireless LAN real-time traffic flow has the characteristics of variable bit rate generally, and the support for variable bit rate traffic flow in EDCA mechanism is insufficient, which will not meet the QoS requirements based on real-time traffic flowThesis is based on EDCA protocol, firstly, we study about multi-channel mechanism, and draw the conclusion that multi-channel mechanism can improve the throughput of the system. Secondly, according to the characteristics of real-time business with variable bit rate, we find the way of adjusting TXOP dynamically, which can satisfy the QoS requirements of variable bit rate business. Finally, the dynamic adaptive TXOP adjustment mechanism based on multi-channel EDCA protocol is given, which can not only improve the system throughput, but also reduce the delay of traffic flow of variable bit rate, satisfy the QoS requirements of real-time traffic flow.