空时编码的OFDM盲信道估计

提出一种新的恒模复调制、单天线接收实现空时编码的OFDM(ST-OFDM)盲信道估计的算法.建立了2发1收的ST-OFDM系统模型;利用空时编码的特点,对发射信号采用恒模复调制,引入周期相关特性,将各子信道分开进行估计;利用循环前缀引入的信息冗余给出子空间算法,实现盲信道估计.恒模复调制可避免非常数调制导致的峰值功率问题.该算法不需要对OFDM信号进行冗余预编码,不会降低系统码率;由于采用单天线接收就可实现盲信道估计,不需要改变接收机的结构;不受信道阶数过估计的影响.但如有信道零点在OFDM子载波上,算法不能成立,因此受信道零点位置的限制.

A Blind Channel Estimation in Space-Time OFDM System

By constant envelope modulation,a new blind algorithm of channel estimation in space-time(ST)-OFDM was proposed using only signal received antenna. An ST-OFDM with two transmit antenna and one receive antenna was founded.By taking advantage of the space-time block coding,a special modulation scheme with constant envelope was designed,which can induce cycle correlation in the system, and lead to estimate the difference sub-channels independently.At last,making use of the CP in OFDM,a blind subspace algorithm was developed to estimate the channels.Constant envelope modulation can avoid the peak power problem in the OFDM,which is inherent to the un-constant modulation.Since no redundant symbols are added in the modulation,the ST-OFDM system can realize the channel identification without decrease of bandwidth efficiency.Moreover,the algorithm is realized by signal received antenna,so the algorithm does not change the structure of ST-OFDM.The algorithm is not sensitive to the channels order overdetermination and is only limited when the channel zeros locate on the subcarrier in the OFDM.