SFBC-OFDM系统在时频双选信道下的迭代接收算法

Iterative receive algorithm for SFBC-OFDM systems in time-frequency dispersive fading channels

基于广义最小信道估计算法,结合迫零均衡原则,针对空频块码正交频分复用系统,提出了一种迭代的均衡广义最小接收算法。该方法推导了两发两收空频块码正交频分复用系统的迫零频域均衡算法,以便消除信道频率选择性衰落所引起的系统相邻子载波间信道系数的差异,从而保证了空频块码的正交性,使得接收算法能够有效抑制差错传播、明显加快迭代的收敛速度并改善系统的比特误码性能。数值仿真结果表明:当归一化多普勒较大时,采用该接收算法的空频块码正交频分复用系统能够较快地收敛,并较基于期望最大化的空频块码正交频分复用系统与基于时域卡尔曼的空频块码正交频分复用系统分别获得8 dB和14 dB的增益。

Based on the generalized M （GM） channel estimation algorithm and the zero forcing principle, an iterative equalized generalized M （EQ-GM） algorithm is proposed and applied to the space frequency block coded orthogonal frequency division multiplexing systems. In the scheme, a frequency domain zero forcing equalizer for the 2 × 2 SFBC-OFDM system is deduced, in order to eliminate the channel coefficient differences of the adjacent subcarriers introduced by the frequency selective channel. Therefore, the receive algorithm can maintain the orthogonality of the SFBC codes, suppress the error propagation, accelerate the iteration convergence and hence improve the system performance effectively. Simulation results show that when the normalized Doppler is large, the SFBC-OFDM system can converge rapid- ly by using the EQ-GM algorithm. When the proposed system is compared with the expectation maximization （EM） SFBC-OFDM system and the time domain Kalman SFBC-OFDM system, gains of 8 dB and 14 dB can be obtained respectively.