In this paper, we propose a method for constructing quasicyclic low-density parity-check codes randomly using cyclic shift submatrices on the basis of the girth of the Tanner graphs of these codes. We consider (3, K)-...
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In this paper, we propose a method for constructing quasicyclic low-density parity-check codes randomly using cyclic shift submatrices on the basis of the girth of the Tanner graphs of these codes. We consider (3, K)-regular codes and first derive the necessary and sufficient conditions for weight-4 and weight-6 codewords to exist. On the basis of these conditions, it is possible to estimate the probability that a random method will generate a (3, K)-regular code with a minimum distance less than or equal to 6, and the proposed method is shown to offer a lower probability than does conventional random construction. Simulation results also show that it is capable of generating good codes both regular and irregular.
Forward error correction (FEC) with high coding gain is needed to achieve PR30 (29 dB) link budget in 50G-PON. In particular, the stringent capacity and latency requirements of the 50G PON call for innovations in the ...
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Forward error correction (FEC) with high coding gain is needed to achieve PR30 (29 dB) link budget in 50G-PON. In particular, the stringent capacity and latency requirements of the 50G PON call for innovations in the design of FEC codes to go against the noise in the channel. In this paper, we propose a generic FPGA design for an adaptive irregular LDPC coding emulator that supports hard-decision, soft-decision, shortening, and puncturing. We evaluate the error-correction performance of the low-density parity-check (LDPC) forward-error correction (FEC) code that is currently under study by ITU-T's 50G-PON group for burst-mode upstream reception. Through experimental measurements based on a real-time FGPA platform, we found that soft-decision (SD) offers similar to 1.3 dB more gross coding gain than hard-decision (HD). The SD LDPC performance is well maintained for non-uniform input bit error distributions where the errors are concentrated at the first 1/8 of each code word, corresponding to similar to 44 ns (similar to 88 ns) for a 50-Gb/s (25-Gb/s) upstream signals. This indicates the suitability of the use of the SD-LDPC for burst-mode upstream reception in 50G-PON.
It has been shown that under min-sum (MS) decoding, scaling the messages at the output of check nodes can improve the performance of regular low-density parity-check (LDPC) codes. However, for irregular codes designed...
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It has been shown that under min-sum (MS) decoding, scaling the messages at the output of check nodes can improve the performance of regular low-density parity-check (LDPC) codes. However, for irregular codes designed for the sum-product decoder, linear scaling can hinder the performance. The problem of code design for MS and linear scaling min-sum (LSMS) decoders have been recently investigated. It is shown that the gap to the capacity for LSMS codes is better than MS codes, but compared to sum-product codes the gap is still considerable. In this letter, a modified MS decoding is proposed and studied. We use the stability analysis of density evolution to show that the proposed method allows for a larger fraction of edges connected to degree-2 variable nodes than LSMS codes. Finally, by designing codes based on the modified method, we show that compared to MS and LSMS codes, a smaller gap to the capacity can indeed be achieved while the complexity of decoding remains essentially the same.
We compute closed-form transfer characteristics for EXIT chart of short rate 1 block codes for binary erasure channel. These functions closely approximate the measurements over additive white Gaussian noise (AWGN) cha...
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ISBN:
(纸本)9781424425143
We compute closed-form transfer characteristics for EXIT chart of short rate 1 block codes for binary erasure channel. These functions closely approximate the measurements over additive white Gaussian noise (AWGN) channel. Optimum irregular inner codes are derived for serial concatenated coding over AWGN channel. In addition, we apply the results on bitinterleaved coded modulation (BICM) and introduce signal set capacity on bit level. It is pointed out that capacity approaching performance with BICM requires new modulation schemes.
As the demands of multimedia and data services increase, efficient communication systems are being investigated to meet the high data rate requirements. Joint source-channel coding (JSCC) schemes were proposed for imp...
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As the demands of multimedia and data services increase, efficient communication systems are being investigated to meet the high data rate requirements. Joint source-channel coding (JSCC) schemes were proposed for improving overall system performance. However, existing JSCC systems may suffer a symbol error rate (SER) performance loss when residual source redundancy is not fully exploited. This paper presents a novel, low-complexity JSCC system, which consists of a fixed-length source block code and an irregular convolutional channel code. A simple approach is proposed to design source codes that minimize the SER of source detection and guarantee the convergence of iterative source-channel decoding (ISCD). To improve the waterfall performance of ISCD, the channel code is optimized by using the extrinsic information transfer (EXIT) chart and the concept of irregular code. The channel code is constituted by recursive non-systematic convolutional (RNSC) subcodes. The weights of subcodes are optimized to make the EXIT curves of the channel decoder and the source decoder well-matched, and therefore, a near-capacity performance is achieved. Simulation results show that the proposed system achieves more than 1 dB gains and 0.3 dB gains compared to the separate source-channel code system and the other optimal JSCC systems, respectively. Additionally, the performance of the proposed system is within 1 dB deviation from the Shannon limit capacity.
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