Research On The Key Technique For OFDMA System

The wireless mobile communication in the future needs the ability to transfer the data with high speed and provide the broadband multimedia service. Because of its high spectrum efficiency and good immunity for the effects of frequency selective or multi-path channel propagation, orthogonal frequency division multiplexing access (OFDMA) has drawn much attention and became a hot spot of researching. OFDMA is a new wireless access technique based on orthogonal frequency division multiplexing (OFDM). It not only inherits all the advantages of OFDM, but also has its own characteristics. In this paper, we present the basic principle of OFDM and OFDMA, then analyze many of there advantages. According to the two uppermost advantages in OFDMA system, the high spectrum efficiency and immunity for frequency selective fading, we study the blind estimation of multi-user frequency offset in the OFDMA uplink and the adaptive resource allocation in the OFDMA downlink. For the blind estimation of frequency offset in OFDMA uplink, we propose two blind estimation algorithms based on different sub-carrier allocation strategies, which can estimate the frequency offset without the help of any pilot or training sequence. For the adaptive resource allocation in OFDMA downlink, we propose a QOS guaranteed adaptive sub-carrier and power allocation algorithm, which has low complexity and can fulfill the need of transmission rate or the proportional fairness of the users.