In this letter we propose rate variable turbo codes based on the parallel concatenation of tailbiting Recursive Systematic multi-binary (m-ary) convolutional codes. Rate variability is not achieved by puncturing, whic...
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In this letter we propose rate variable turbo codes based on the parallel concatenation of tailbiting Recursive Systematic multi-binary (m-ary) convolutional codes. Rate variability is not achieved by puncturing, which can have adverse effects on the minimum distance of the code. Using a variable number of input lines of the encoder, we obtain several different overall rates ranging from 1/2 to 7/8. The most suitable Soft-In-Soft-Out decoding algorithm for these turbo codes is based on the Dual Reciprocal Code, which is very efficient for high rate codes. A particular interleaver design, namely the "backbone" interleaver, guarantees a high Hamming weight in codewords with information weight 2 and 3, as well as good minimum distances and fairly low multiplicities for higher information weights. Therefore, these codes have very low error floors.
A reduced complexity algorithm is presented for computing the log-likelihood ratios (LLRs) arising in the successive cancellation (SC) decoder for polar codes with large kernels of arbitrary dimension. The proposed al...
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A reduced complexity algorithm is presented for computing the log-likelihood ratios (LLRs) arising in the successive cancellation (SC) decoder for polar codes with large kernels of arbitrary dimension. The proposed algorithm exploits a recursive trellis representation of the codes generated by submatrices of the polarization kernel and enables polar codes based on large kernels to be decoded with lower complexity compared to the codes based on the Arikan kernel with the same performance. Extensions to the case of non-binary kernels are presented.
This paper presents a novel construction scheme for nonbinary single-error correcting (SEC) codes that yields highspeed parallel decoding. The proposed scheme utilizes two methods, namely, Improved and Reordered;these...
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This paper presents a novel construction scheme for nonbinary single-error correcting (SEC) codes that yields highspeed parallel decoding. The proposed scheme utilizes two methods, namely, Improved and Reordered;these methods can be also combined. Both of these methods reduce the number of 1's in the parity-check matrix (H-matrix) by reducing the 1's in every row vector. This results in a reduction in the gate depth in the syndrome generator, thus achieving a shorter delay time for parallel decoding. In the proposed Improved method, for a single b-bit byte (i.e., 2(b)-ary symbol) error correcting code, the submatrix of the H-matrix corresponding to every b-bit byte is multiplied with a regular matrix. The so-called improved submatrix is generated using a heuristic (greedy) algorithm. The proposed Reordered method selects the correct b-bit bytes for deletion when shortening is performed. Simulation results show that the proposed scheme accomplishes a faster parallel decoding time than existing schemes. Furthermore, the proposed scheme is applicable to any class of linear SEC codes, whereas existing schemes are applicable only to specific codes. Extensive simulation results are provided to substantiate the viability of the proposed codes for faster parallel decoding (albeit incurring for most cases in modest increases of area and power dissipation due to additional circuitry).
A recursive construction of k-ary uniquely decodable multiuser codes is proposed for use in a noiseless multiple-access adder channel. The code rates of the proposed codes are higher than those of previous uniquely de...
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ISBN:
(纸本)9784885523182
A recursive construction of k-ary uniquely decodable multiuser codes is proposed for use in a noiseless multiple-access adder channel. The code rates of the proposed codes are higher than those of previous uniquely decodable multiuser codes. A recursive decoding algorithm is also proposed.
Previous work on non-binary Fibonacci codes is extended by the presentation of a new family of universal codes having the additional advantage of admitting more codewords for a given large enough length. These denser ...
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ISBN:
(纸本)9798350385885;9798350385878
Previous work on non-binary Fibonacci codes is extended by the presentation of a new family of universal codes having the additional advantage of admitting more codewords for a given large enough length. These denser codes also share the other properties of instantaneous decipherability and robustness against transmission errors, and are proposed as an alternative to compress lists of very large integers, like those used in cryptography.
We introduce a new family of linear block codes over Z(q) that we name low-Lee-density parity-check (LLDPC) codes. These codes, which are embedded with the Lee metric, are characterized by a parity-check matrix whose ...
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ISBN:
(纸本)9781728150895
We introduce a new family of linear block codes over Z(q) that we name low-Lee-density parity-check (LLDPC) codes. These codes, which are embedded with the Lee metric, are characterized by a parity-check matrix whose rows and columns have low Lee weight. We propose general constructions of LLDPC codes and devise an efficient iterative decoding algorithm for them, with complexity that grows linearly with the code length. We assess the error rate performance of these codes through numerical simulations.
The recently proposed recursive convolutional lattice code (RCLC) can form a signal with pseudo-Gaussian constellations, and their parallel concatenation is shown to approach the Shannon limit. A practical limitation ...
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The recently proposed recursive convolutional lattice code (RCLC) can form a signal with pseudo-Gaussian constellations, and their parallel concatenation is shown to approach the Shannon limit. A practical limitation is that its input symbol is limited to L-2-ary quadrature amplitude modulation (QAM), which has non-power-of-two constellation points when L is chosen from the odd numbers. Therefore, encoding binary information by the RCLC is not straightforward. Furthermore, the information rate is limited to log(2) L bits per complex dimension due to their parallel concatenation. In this paper, we tackle these issues by introducing a serial concatenation of binary-input nonbinary-output convolutional code (CC) and the RCLC, where the outer CC outputs an L-ary symbol that is matched to the input of the inner RCLC. We demonstrate that even with L = 3, the proposed approach can achieve 2 bits per complex dimension and still is able to approach the Shannon limit with lower decoding complexity compared with its parallel concatenation counterpart. As is demonstrated through theoretical analysis, the major practical drawback of the constellation generated by the RCLC is its Gaussian-like distribution, which has large peak-to average power ratio. Therefore, we further introduce an approach to reduce the signal dynamic range for the proposed system. It is shown that a remarkable gain can be achieved in terms of capacity compared with the conventional QAM signals under the constraint of comparable power amplifier efficiency.
A class of circular 64-QAM that combines "geometric" and "probabilistic" shaping aspects is presented. It is compared to square 64-QAM in back-to-back, single-channel, and wavelength division multi...
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A class of circular 64-QAM that combines "geometric" and "probabilistic" shaping aspects is presented. It is compared to square 64-QAM in back-to-back, single-channel, and wavelength division multiplexing (WDM) transmission experiments. First, for the linear additive white Gaussian noise channel model, it permits to operate close to the Shannon limits for a wide range of signal-to-noise ratios. Second, WDM simulations over several hundreds of kilometers show that the obtained signal-to-noise ratios are equivalent to-or slightly exceed-those of probabilistic shaped 64-QAM. Third, for real-life validation purpose, an experimental comparison with unshaped 64-QAM is performed where 28% distance gains are recorded when using 19 channels at 54.2 GBd. This again is in line-or slightly exceeds-the gains generally obtained with probabilistic shaping. Depending upon implementation requirements (core forward-error correcting scheme for example), the investigated modulation schemes may be key alternatives for next-generation optical systems.
Transmission channels underlying modern dense storage systems, e.g., Flash memory and magnetic recording (MR) systems, significantly differ from canonical channels, like additive white Gaussian noise (AWGN) channels. ...
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Transmission channels underlying modern dense storage systems, e.g., Flash memory and magnetic recording (MR) systems, significantly differ from canonical channels, like additive white Gaussian noise (AWGN) channels. While existing low-density parity-check (LDPC) codes optimized for symmetric, AWGN-like channels are being actively considered for Flash applications, we demonstrate that, due to channel asymmetry, such approaches are inadequate. We introduce a refined definition of absorbing sets, which we call general absorbing sets of type two (GASTs), and study the combinatorial properties of GASTs. We then present the weight consistency matrix (WCM), which succinctly captures key properties in a GAST. Furthermore, we show how to customize the WCM definition such that it suits other special subclasses of GASTs. Based on these new concepts, we then develop a new, general combinatorial code optimization framework, which we call the WCM framework, and demonstrate its effectiveness on the realistic highly-asymmetric normal-Laplace mixture (NLM) Flash channel. Moreover, we show that our framework can be customized to optimize non-binary LDPC (NB-LDPC) codes for other asymmetric channels, channels with memory (incorporated in MR systems), and canonical symmetric channels. For all the channels we have simulated NB-LDPC codes over, the codes optimized using the WCM framework enjoy at least 1 order, and up to nearly 2 orders of magnitude performance gain in the uncorrectable bit error rate (UBER) or the frame error rate (FER) relative to the unoptimized codes. Our simulations also show that codes optimized for symmetric channels are not the best choice for asymmetric channels.
Three areas of ongoing research in channel coding are surveyed, and recent developments are presented in each area: Spatially coupled low-density parity-check (LDPC) codes, non-binary LDPC codes, and polar coding.
Three areas of ongoing research in channel coding are surveyed, and recent developments are presented in each area: Spatially coupled low-density parity-check (LDPC) codes, non-binary LDPC codes, and polar coding.
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