| A primary challenge for future generation broadband wireless networks is the support of integrated multimedia type traffic over a unified network platform. Given the stringent constraints on bandwidth, power and cost relative to increasing end-user expectations, design optimization approaches for the air interface (involving multiple access/modem designs) that most efficiently exploit spectrum resources in a dynamic time-varying environment is a critical imperative. Orthogonal Frequency Division Multiplexing is a form of modulation that presents excellent performance over frequency selective channel and the type of parallelism most suitable for DSP implementation. Built upon OFDM modem, Orthogonal Frequency Division Multiple Access has emerged prime multiple-access schemes for wireless broadband networksThis dissertation elaborated the inevitability of OFDMA as the first choice of future Wireless communication multi-access scheme base on the analyse of OFDM and multiple access techniques. Researched the adaptive resource allocation techniques(subcarrier allocation technique, bit allocation technique and power allocation technique) under the wireless fading channel.And then, researched and analyzed the Lagrangian Relaxation algorithm and Yin algorithm under the criterion of Margin Adaptive; Researched and analyzed the Rhee and Shen algorithms under the criterion of Rate Adaptive; Contrast the respective superiority and insufficiency of them through computer simulation.Finally, introduced a low complexity algorithm for proportional resource allocation in OFDMA systems, improved it through adding a Fairness-Iterative under the criterion of Rate-adaptive, the new method can solve the problem of proportionality constrained rate maximization, The computer simulation result show that the improved algorithm can provide a flexible trade-off between complexity, throughput and proportionality constraint, manifested excellent performance on the respect of proportional character. |
PDF Full Text Request