Optimized Message Passing Schedules for LDPC Decoding
de Baynast, Alexandre
Cavallaro, Joseph R.
Forward Error Correction; LDPC codes; Message-Passing algorithms; Decoding convergence; Layered Belief Propagation
The major drawback of the LDPC codes versus the turbo-codes is their comparative low convergence speed: 25-30 iterations vs. 8-10 iterations for turbo-codes. Recently, Hocevar showed by simulations that the convergence rate of the LDPC decoder can be accelerated by exploiting a â turbo-schedulingâ applied on the bit-node messages (rows of the parity check matrix). In this paper, we show analytically that the convergence rate for this type of scheduling is about two times increased for most of the regular LDPC codes. Second we prove that â turbo-schedulingâ applied on the rows of the parity check matrix is identical belief propagation algorithm as standard message passing algorithm. Furthermore, we propose two new message passing schedules: 1) a turbo-scheduling is applied on the checknode messages (columns of the parity check matrix); 2) a hybrid version of both previous schedules where the turbo-effect is applied on both check-nodes and bit-nodes. Frame error rate simulations validate the effectiveness of the proposed schedules.
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