To deal with the complexity of traditional BP decoding algorithm, a kind of blind decoding algorithm for LDPC codes based on soft-input, soft-output is put forward in this paper. The algorithm uses soft squared Euclidean distance as the metric, realizes decoding by iterating the antilog-sum of the Euclidean distance as the process taken in BP algorithm. The proposed algorithm does not require knowledge of the signal-to-noise ratio of the received signal, and is less complex to implement than other soft decision algorithms. At the same time, a simplified algorithm is also put forward to reduce the computational complexity. What's more, the proposed SBSD decoding algorithm can not only decode Binary LDPC codes, but also can be used for Qary-LDPC codes. Simulations results show that the proposed algorithm can achieve good performance not only on the AWGN channels but also on Rayleigh channel, and the performance is very close to that of the sum-product algorithm, but the computational complexity is reduced sharply.%针对传统BP译码算法需要初始条件的缺点,本文提出了一种基于软输入软输出(SISO)的LDPC码盲译码算法,所提算法采用类似BP迭代译码算法步骤,通过对距离信息进行迭代处理,实现无需接收信号的信噪比和信道状态即可译码;同时,还将所提盲译码算法推广到多进制LDPC码的译码应用中.本文所提盲译码算法在初始状态难以确定以及接收信号信噪比难以估计的通信信道中具有重要价值.仿真结果表明,所提算法不论是在AWGN信道还是在瑞利衰落信道上都能取得优良的性能,不论是与标准BP译码算法还是与分层BP译码算法相比,在性能相近的情况下,计算复杂度都有所降低.
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