WiMAX şebekelerinde kısmi frekans tekrar kullanımı için statik ve ayarlanabilir altkanal tahsis şemalarının performansı

We study the downlink performance of WiMAX under fractional frequency reuse (FFR)model. Conventional cellular planning methods can be used for broadband wireless accesssystems that operate in point-to-multipoint (PMP) conguration based on OFDMA/OFDMsuch as WiMAX. As an alternative planning method, FFR has been recently proposed forOFDMA/OFDM based cellular systems. FFR divides the cell into two regions: the innerand outer cell. Mobile Stations (MS) inside the inner cell can use the entire frequencyband (achieving full frequency reuse), while MSs in the outer ring use a fraction of theband (having fractional frequency reuse). Transmissions in the inner and outer cells occurduring dierent time periods so that users at the cell edge experience less interference. Inthis thesis, we investigate the eect of dynamically changing the number of subcarriersallocated to inner and outer cells. We use two metrics: total cell throughput and Jain'sfairness index for the distribution of cell throughput among MSs. As the ratio of subcarriersallocated to inner cell increases, the total cell throughput increases while the fairnessindex decreases. We use the product of cell throughput and fairness index in order to studythe trade-o between the two metrics. We show that by dynamically adjusting the ratioof subcarriers allocated to the inner cell based on the user distribution, the throughputiiifairness index product can be increased by about 5% compared with the xed optimumsubcarrier allocation.