一种基于IEEE 802.16d的OFDM载波跟踪算法

利用OFDM符号中插入的导频信号,提出了一种基于IEEE802.16d标准的载波频率偏移跟踪的优化算法,该优化算法基于最小均方误差准则(MM SE).估计过程中,同时考虑载波频率偏移产生的2方面影响:在某个OFDM符号内,与子载波位置无关的固定相位旋转和幅度衰减;载波正交性破坏引入的载波间干扰(ICI).对于载波间干扰能量的估计则充分利用了空子载波提供的信息.仿真结果表明,基于MM SE准则的频偏跟踪算法由于减小了ICI的影响,所以比忽略ICI只考虑固定相位旋转量的跟踪算法能够更有效地减小系统的误码率和均方误差.

Efficient algorithm for tracking carrier frequency offset in IEEE 802.16d OFDM systems

The spread spectrum pilots of the OFDM(orthogonal frequency division multiplexing) symbols are used to estimate the effect caused by residual carrier frequency offset in IEEE 802.16d OFDM systems by an improved tracking algorithm. This novel method is based on MMSE(minimum mean square error) estimation.In the estimating process,two kinds of effects caused by carrier frequency offset are considered,including the fixed phase rotation and amplitude attenuation,which keep unchanged for different subcarriers within the same OFDM symbol,and the intercarrier interference(ICI) resulted from orthogonality broken between subcarriers.The null subcarriers are utilized to estimate the energy of ICI.Simulation results show that the MMSE based tracking method mitigates the ICI influence,therefore it decreases bit error and mean square error more effectively than the neglect-ICI ways that only put fixed phase rotation into consideration.