Research On Rources Allocation Mechanism For WiMAX System

Link adaptation is a key technology to the modern wireless communication systems. As a new-generation broadband wireless standard, WiMAX adopts a variety of link adaptive technology. An efficient resource allocation mechanism is essential in improving the performance of WiMAX system. This paper relied on "WiMAX wireless access equipment development" which is key item of NingBo industry project, and took highly-efficient resources allocation mechanism as the main content, including the adaptive modelation and coding(AMC), slot allocation for AMC subcarriers allocation and adptive frequency selection (DFS).chater 3 proposed a joint algorithm about power allocation and AMC. The algorithm adopted the water-filling power allocation according the modulation, and adjusted power combined with the quality of the subcarriers. Meanwhile, the different subchannel SNR measurement had been analyzed. The simulation results show that mean-corrections algorithm can efficiently reduce BER, compared with the mean corrections when the subchannel SNR fluctuates widely.Resource allocation for WiMAX involves time-frequency domain, and there maybe be a serious signaling overhead. Chater 4 proposes a resource allocation algorithm based on multiuser diversity for the AMC subcarrier permutation. The signaling overhead is restrained by searching the cotinuous subchannels with the same modulation and coding. Meanwhile, the system performance is distinctly improved. In addition, resources allocation for the PUSC mode was also discussed.In free-permission frequency band, WiMAX must provide the DFS function. Chapter 5 presented a DFS algorithm based on the channel priority. Every available channel is assigned a value based previous measurement records, which can reduce the time of channel switch. And this algorithm resolves the flaw of existing algorithms, like frequent switch and fake switch, through setting exit threshold and entry threshold. Exit threshold value and entry threshold value is the key factor of algorithm performance:the former impacts the frequency of channel switch; the latter impacts the system throughput. But fundamental principle is that the value of entry threshold is bigger than the value of exit threshold.