Master Thesis - 2008

For advanced mobile multimedia services, it is expected that wireless access networks have much wider bandwidth. As a promising technology to realize such a network, a mesh network based on WiMAX or WiFi has attracted attention over the years. In a WiFi mesh network, several WiFi access points (APs) are interconnected wirelessly and the communication with the backbone network transits through the gateway AP connected by wired cable. In addition, if each AP has the multi-channel and multi-interface function, it is possible to increase the network capacity by dynamic changing of the assigned channel of each wireless link. However, when many users communicate with the backbone network, the network throughput decreases by concentration of the network load on gateway APs.

To overcome this problem, WiMAX/WiFi interworking mesh network where some WiFi APs connect to WiMAX base station as a gateway to the Internet has been proposed and spotlighted. Therefore, the network load on each gateway AP in a WiFi mesh network is balanced and the throughput of entire system is improved.

On the other hand, to widen the available spectrum bandwidth further, a new reservation of the spectrum is necessary. However, in WiMAX/WiFi interworking mesh networks, the number of the unused spectrum band exists on a certain time and space in each system. Hence, dynamic spectrum access technology which allows a wireless system to use the radio frequency spectrum used in another wireless systems secondarily is expected.

In this paper, we propose the effective spectrum sharing method in such a WiMAX/WiFi interworking mesh network by using the dynamic spectrum access technology in order to improve the network throughput. Finally, we show the effectiveness of the proposed method by simulation experiments.