一种基于判决反馈的OFDM系统载波频率跟踪算法

A kind of decision-directed carrier frequency tracking algorithm for OFDM systems

研究了多径信道下OFDM系统的一种新的载波频率跟踪算法,这种算法以判决反馈和接收端的时域信号重构为基础。推导了估计结果的精确解,比较了使用原估计结果和新的估计结果进行频偏补偿时系统跟踪性能的不同。通过对算法的仔细分析,发现除了通常的加性噪声外,信道估计误差、子载波数目和子载波的调制方式也影响频偏的估计结果和跟踪范围,而且子载波的数目和调制方式是决定性的因素。这种频率跟踪方法的优点是即使在很低的信噪比下仍然能获得高的跟踪精度,且实现相对简单。

In this paper, a novel decision-directed carrier frequency blind tracking algorithm for OFDM systems in multipath channels, based on time domain signal reconstructed by data after decision and channel estimation, has been addressed, and the accurate CFO estimate result is derived. The improvement of performance due to using the new estimate result is illustrated. The tracking algorithm is analyzed carefully, and it is found that not only noise, but other three factors—channel estimate errors, carrier number and modulation schemes— also affect the estimate result and tracking range. Moreover, carrier number and modulation schemes are the dominant factors. This estimator has the advantage of high accuracy even on low signal to noise ratio conditions, but its implementation is relatively simple.