Research On Resource Allocation Algorithm In OFDMA Systems

In the future broadband wireless communication systems, it exists two most criticalchallenges: multipath fading channel and frequency efficiency. Orthogonal frequency divisionmultiplexing (OFDM) technology had enormous advantages in the anti-multipath fading andhigh-speed transmission, they made OFDM as a key technology of the fourth-generation mobiletechnology. Orthogonal frequency division multiple access (OFDMA) based on OFDM alsobecame a research point in wireless access technology research. Therefore, the research ofresource allocation based on OFDMA became as a hot topic in the study of the current fourthgenerationmobile communications.Firstly, the development of mobile communications and resource allocation techniques werereviewed. Secondly, the basic concepts and principles about OFDMA systems and resourceallocation techniques were given. Thirdly, the adaptive resource allocation techniques (subcarrierallocation technique, bit allocation technique and power allocation technique) about OFDMAsystems were researched, some typical resource allocation algorithms, including greedyalgorithm, Max-Min algorithm, Ian algorithm and Hui algorithm, are analyzed.Finally, a new algorithm with controllable capacity and fairness is proposed in this paper forOFDMA downlink resource allocation. It seeks to maximize the total system capacity subject toconstraints on total power, BER and rate proportions. Future communication systems should takeboth capacity and fairness into account together. Therefore, the new algorithm has a novel step torearrange the subcarriers among users to achieve a certain tradeoff between enhanced rate andproportional fairness. This tradeoff can be controlled by the introduced Tradeoff-Factor (TF).Simulation results show that this new capacity and fairness controllable scheme may be suitablefor future Quality of Service (QoS) adjustable OFDMA systems.