基于时频子空间投影的LOFDM系统时域相关信道估计算法  

LOFDM Time Domain Correlation Channel Estimation Based on the Time-Frequency Subspace Projection

作　　者：高猛[1] 沈越泓[1] 许魁[1] 

机构地区：[1]解放军理工大学通信工程学院,南京210007

出　　处：《信号处理》2011年第1期81-87,共7页Journal of Signal Processing

基　　金：国家自然科学基金(60772083)

摘　　要：StrohmerT与Beaver S于2003年提出了适用于时频散射信道的网格正交频分复用(LOFDM,Lattice OrthogonalFrequency Division Multiplexing)系统,与传统OFDM系统相比该系统具有更高的频带利用率和更好的误码性能。LOFDM系统发送端需要自适应地调整信号的原形脉冲和其时频分布的参数,使之与信道保持匹配;而接收端则需要准确的信道估计以实现相干解调。本文针对LOFDM系统由于其信号的时频交错特性接收端无法直接利用接收信号进行时域信道估计的问题,采用一种低复杂度的等效时频子空间投影方法有效分离奇偶子载波,并在此基础上提出了一种LOFDM系统频率选择性块衰落信道条件下的时域信道估计算法。同时还对系统存在的干扰进行了分析,推导得到LOFDM系统时域信道估计算法的Cramer-Rao理论下界。仿真表明:提出的LOFDM信道估计算法不仅具有较好的均方误差性能,而且近似达到理想信道估计的误符号率性能。LOFDM（Lattice Orthogonal Frequency Division Multiplexing）,which is proposed by Strohmer T and Beaver S in 2003,has higher spectral efficiency and better bit error rate（BER） performance compared with OFDM systems in the time-frequency dispersive channel.LOFDM systems need to adapt the parameters of signals＇ time-frequency lattice（TFL） and shaping-pulse scale to the channel dispersion characteristics in the transmitters,while the exact channel estimation is required for coherence demodulation in the receivers.The time-frequency interleaving characteristics of LOFDM signals induce that the time domain channel estimation can＇ t be achieved via the received signals directly.In this work,we separate the odd and even carriers through the equivalent time-frequency subspace projection,and a low complexity time domain correlation channel estimation algorithm for LOFDM systems is proposed based on pilot design and frequency domain pilot time domain correlation method.The interference problem is analyzed and the Cramer-Rao bound（CRB） of the time domain channel estimation for LOFDM systems is also deduced.Simulation results demonstrate that the proposed algorithm has good mean square error performance between the estimated CIR（Channel Impulse Response） and the true one, while symbol error rate performance of demodulation through the estimated CIR is near with the ideal channel.

关 键 词：LOFDM 时频子空间投影 频域导频时域相关 信道估计 Cramer-Rao BOUND 

分 类 号：TN929.5[电子电信—通信与信息系统]