Efficient receiver design for OFDMA Systems with subband carrier allocation strategy

Time and frequency offsets can cause severe degradation in the performance of any OFDM-based System. Therefore synchronization procedures are necessary for the proper function of a receiver. In OFDMA, where different users share the available subcarriers, synchronization becomes an arduous task. Synchronization errors as far as the uplink transmission is concerned may cause intolerable Multiple Access Interference (MAI) as the signals are produced by different mobile users and propagate through different channels with various Carrier Offsets and Doppler shifts. The receiver must estimate a number of parameters and compensate for the produced intercarrier (ICI) and intersymbol (ISI) interference. These tasks cause massive increase of the computational workload required by the receiver. However, with the use of proper filtering and multirate processing the receiver complexity can be contained with no significant performance degradation.