瑞利衰落信道下的Turbo均衡

Turbo均衡是一种将Turbo原理和均衡技术结合起来的技术。他通过反复均衡和信道译码来提高接收机性能。针时瑞利衰落信道，采用基于线性滤波器的软输入／软输出均衡器来消除码间干扰，其系数由最小均方误差准则确定。译码器采用最大后验概率算法时卷积码译码。考虑到瑞利衰落信道为随机信道，用非相干检测时信道进行估计。接收机通过联合均衡和译码以充分利用已经获得的信息，实现信道估计及信道均衡与信道译码的迭代更新。仿真结果表明其性能不仅远远优于非迭代系统．而且在信噪比高于4dB时几乎可以完全消除符号间干扰的影响，与MAPSE相比其复杂度大大降低。

Turbo Equalization for Rayleigh Fading Channel

Turbo equalization is a technique which combines Turbo principle with equalization technology which repeating equalization and channel decoding to improve receiver performance.For Rayleigh fading channel,the ISI is removed with a Softin Softout(SISO) equalizer based on linear filtering,where the minimum mean squared error criterion is used to set up the filter coefficients.A convolutional code is employed using a decoder based on a Maximum Aposteriori Probability(MAP) per symbol estimation.Considering Rayleigh fading channel is random channel,noncoherent detection is used for channel estimation.The receiver performs joint equalization and decoding to realize iterative channel estimation,channel equalization and channel decoding.Simulation results show that the proposed system performs well,not only providing perfomance that is significantly better than tradition noniterative techniques,but also can almost entirely remove the degration introduced by ISI for SNB is higher than 4 dB.While compared to MAP Symbol Estimation(MAPSE),there is a large saving in computational complexity.