WiMAX OFDMA初始测距中的多用户频偏估计

测距过程是移动WiMAX标准中的重要过程，用于解决远近效应及同步问题。该文针对WiMAX OFDMA上行链路的初始测距，提出了两种适用于多用户的载波频偏估计方法。方法1采用参考测距信号与接收信号的时域相关提取期望测距信号，并利用相关结果的相位估计测距用户的频偏；方法2采用参考测距信号与接收到的两个相邻OFDM符号的频域相关提取期望测距信号，并利用两次结果的相位差估计测距用户的频偏。仿真实验证明基于频域相关的方法更适合于在一个测距时隙内存在多个测距用户的情况，并且不易受定时偏差估计误差的影响。

Multiuser Carrier Frequency Offset Estimation for WiMAX Initial Ranging Based on OFDMA

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.