Near-Capacity Three-Stage MMSE Turbo Equalization Using Irregular Convolutional Codes

摘要

Traditional Turbo EQualization (TEQ) schemes suffer from residual bit errors due to the non-recursive nature of the channel imposing Inter-Symbol-Interference (ISI). The performance of the traditional TEQ scheme may, however, be improved if an intermediate recursive channel codec is invoked, which results in a three-stage serially concatenated system. This intermediate code is necessary, especially when the inner module cannot be rendered recursive, for example, when a Minimum Mean Square Error (MMSE) equalizer is invoked. Our EXtrinsic Information Transfer (EXIT) chart analysis explicitly explains the performance gain, and based on this explanation IRregular Convolutional Codes (IRCCs) are constructed to be used as the outer code for the sake of achieving near capacity performance. Furthermore, the proposed analysis and design procedure may be applied in the context of diverse iterative receivers employing multiple soft-in/soft-out (SISO) modules.