多载波调制码分多址系统自适应盲信道估计

Adaptive Blind Channel Estimation in Multicarrier CodeDivision Multiple Access System

针对多载波调制码分多址系统中循环前缀的引入会降低系统传输效率及相应的盲信道估计方法运算量大等问题 ,在分析了无需循环前缀而利用虚拟子载波的盲信道估计方法的基础上 ,将子载波的正交性与信号时域特征相结合 ,提出一种基于恒模准则的盲信道估计方法 .通过将频域的扩频码等效到时域 ,利用恒模算法锁定期望用户、抑制干扰用户和无需大量矩阵求逆运算等特性 ,在时域实现了盲信道估计与多用户分离 .数值仿真结果表明 ,基于恒模准则的信道估计均方根误差小于基于有限码集的方法 ,并且具有运算量小、收敛速度快等特点 .

Multicarrier modulation code division multiple access (MC CDMA) technique can sufficiently utilize the subcarrier diversity and meet the demand of diverse multimedia services, therefore, it is broadly considered as an effective approach for future wireless multimedia communications. The insertion of cyclic prefix (CP) can combat the channel distortion, but with the loss of channel throughput. Using the useful information of CP, the blind channel estimation has much computing burden, so the blind channel estimation using virtual carrier is studied. Combining the orthogonal property of subcarrier with the signal's time-domain character, a constant modulus (CM) based method is proposed for MC-CDMA systems, in which the spreading code in frequency domain can be equivalent to the time domain, and achieve the blind channel estimation and multiuser detection in time domain. Compared SVD based method and the finite apphabet (FA) based method, the CM based method can lock and converge to the desire user, reduce the interference and has low complexity. Numerical simulations illustrate the effectiveness of this algorithm.