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Decoder Block Diagram
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The decoding of LDPC codes on finite-state Markov channels is considered. A message-passing algorithm using a threshold to control decoding order, where the threshold depends upon the estimated channel state is proposed.
Context in source publication
Context 1
... ⊕ ˆ c n . This is used as input to a forward-backward algorithm similar to the BCJR algo- rithm. This algorithm computes the approximate LLR, ˆ λ n , and become inputs to the sum-product algorithm for successive "global" iterations. However, if there are errors in the hard decisionsˆcdecisionsˆ decisionsˆc n , this can cause error prop- agation. Fig. 2 shows the decoder block diagram for a sys- tem where the approximate LLRs are computed by Wa- dayama's algorithm. Alternatively, the BCJR algorithm may be used to compute the exact ...
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Citations
Voice and video traffic can tolerate some errors in end-to-end transfer but require very low latency. Data traffic typically requires an almost error free transfer but can tolerate higher latency. Thus, coding and forward error corrections are the main mechanisms for error controls for voice and video traffic while ARQ is the main mechanism for error controls for data traffic. When the error rates are high (for example, in wireless links), it is beneficial to have both forward error corrections and ARQ for data traffic. In addition, the effectiveness of the coding and FEC can be improved by using interleaving. The combined effects of coding, interleaving, and ARQ on data traffic effective throughput is not well understood. In this paper, we take the first steps. In particular, we show the effective throughput is very sensitive to channel, coding, and interleaving parameters, thus identifying a need to study parameter optimization further. We also show that appropriately sized LDPC codes provide better throughput than traditional codes do. Early results also suggest that, for mixed traffic environment, it may pay to have some coding and interleaving be done at higher layer to allow application specific parameters.
