Multiuser Carrier Frequency Offset Estimation for WiMAX Initial Ranging Based on OFDMA
WiMAX OFDMA初始测距中的多用户频偏估计

Ranging is one of the most important processes in the mobile WiMAX standard, for resolving the uplink synchronization and near/far problems. In this paper, under WiMAX OFDMA framework, two Carrier-Frequency Offset (CFO) estimation methods for multiuser case are proposed for initial ranging process. In Method 1, the CFO of each ranging user is estimated by utilizing the phase of time-domain correlation results between the ranging signal and the received signal samples. Method 2 uses the phase difference of frequency-domain correlation results between the ranging signal and two received consecutive OFDMA symbols. Simulation results show that the proposed frequency-domain correlation method performs better than the time-domain correlation method even in the case of multiple users simultaneously existing in one ranging time-slot. And it is more robust to timing offsets result from the Symbol Timing Offset (STO) estimation error.