Master Thesis - 2007

Recently, as wireless systems develop and multimedia communications spread, the stringency of a radio frequency spectrum has stood out in relief. Cognitive radio is expected as a technology to overcome the spectrum shortage. The ideal goal of the cognitive radio is to achieve the effective communications in any environments in response to network and user demands.

The studies which try to realize WiMAX/WLAN integrated network which uses WiMAX and WLAN selectively to provide the effective services to users are extensively performed. Although the well-researched method can realize the integrated network without contravening Radio Law, the number of the unused spectrum band exists on a certain time and space in each system. Therefore, it is said that the utilization efficiency of the radio frequency spectrum is not so improved by using the existing method.

Thus, I propose the spectrum sharing method that enables the improvement of the utilization efficiency of the spectrum and the quality of services by flexibly and dynamically sharing each spectrum between WiMAX and WiFi in the WiMAX/WiFi integrated network.

Finally, we evaluated the effectiveness of the proposed method by simulation and confirmed that the proposed method can improve the utilization efficiency of the spectrum, the throughput and the rejected ratio of the WiMAX/WiFi integrated network.