Optimization of LDPC Codes by Extrinsic Information Transfer Chart

2013 ◽  
Vol 427-429 ◽  
pp. 1518-1523
Author(s):  
Jing Xi Zhang
Keyword(s):  
Information Transfer ◽  
Multiple Access ◽  
Gaussian Approximation ◽  
Additive White Gaussian Noise ◽  
Ldpc Code ◽  
Multiple Access Channel ◽  
Parity Check ◽  
Extrinsic Information ◽  
Access Channel ◽  
Check Matrix

The optimization of degree profiles of low-density parity-check (LDPC) code in additive white Gaussian noise (AWGN) multiple access channel (MAC) by fitting the transfer characteristics of variable nodes detector (VND) and that of check nodes detector (CND) is discussed. Extrinsic information transfer (EXIT) characteristics are used for determining the degree profiles based on curve fitting. The convergence the optimized LDPC code is ensured by the EXIT characteristics of VND and CND. Degree profiles are obtained and check matrix is constructed. Simulation results show that the method is variable in designing LDPC code degree profiles in MAC with reduced complexity compared with density evolution based on Gaussian approximation.

Image Transmission Based on QC-LDPC Codes with Simple Recursive Encoding Form

2014 ◽  
Vol 602-605 ◽  
pp. 3223-3227
Author(s):  
Hua Xu
Keyword(s):  
Information Transfer ◽  
Ldpc Codes ◽  
Ldpc Code ◽  
Image Transmission ◽  
Parity Check ◽  
Extrinsic Information ◽  
Transmission Scheme ◽  
Check Matrix ◽  
Exponent Matrix ◽  
Base Matrix

Low encoding delay and complexity is very important for image transmission. This paper proposes a novel image transmission scheme with low encoding complexity. The proposed scheme is based on quasi-cyclic low density parity check (QC-LDPC) codes with a simple recursive encoding form (SREF QC-LDPC code) which results in low encoding complexity and delay. Constructing the SREF QC-LDPC codes in this scheme composes of two main steps, construction of the base matrix and the exponent matrix. We combine the differential evolution and protograph extrinsic information transfer (PEXIT) method to optimize the base matrix of QC-LDPC code. Consequently, the exponent matrix and the parity check matrix are constructed. Simulation results show that the proposed scheme based on SREF QC-LDPC code can provide a good tradeoff between the performance and complexity.

scholarly journals On Compressed Sensing of Binary Signals for the Unsourced Random Access Channel

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 605
Author(s):  
Elad Romanov ◽  
Or Ordentlich
Keyword(s):  
Compressed Sensing ◽  
Additive White Gaussian Noise ◽  
Random Access ◽  
Monte Carlo Algorithm ◽  
Parity Check ◽  
Sensing Matrix ◽  
Recovery Algorithm ◽  
Access Channel ◽  
Check Matrix ◽  
Sparse Sensing

Motivated by applications in unsourced random access, this paper develops a novel scheme for the problem of compressed sensing of binary signals. In this problem, the goal is to design a sensing matrix A and a recovery algorithm, such that the sparse binary vector x can be recovered reliably from the measurements y=Ax+σz, where z is additive white Gaussian noise. We propose to design A as a parity check matrix of a low-density parity-check code (LDPC) and to recover x from the measurements y using a Markov chain Monte Carlo algorithm, which runs relatively fast due to the sparse structure of A. The performance of our scheme is comparable to state-of-the-art schemes, which use dense sensing matrices, while enjoying the advantages of using a sparse sensing matrix.

scholarly journals LDPC Code Design for the Two-User Gaussian Multiple Access Channel

2016 ◽  
Vol 15 (4) ◽  
pp. 2833-2844 ◽  
Author(s):  
Shahrouz Sharifi ◽  
A. Korhan Tanc ◽  
Tolga M. Duman
Keyword(s):  
Multiple Access ◽  
Ldpc Code ◽  
Multiple Access Channel ◽  
Code Design ◽  
Access Channel

scholarly journals Improving Polar-Coded SCMA System by Information Coupling and Parity Check

Sensors ◽  
2020 ◽  
Vol 20 (23) ◽  
pp. 6740
Author(s):  
Xi Wu ◽  
Yafeng Wang
Keyword(s):  
Information Transfer ◽  
Multiple Access ◽  
Iterative Detection ◽  
Bayes Rule ◽  
Parity Check ◽  
Extrinsic Information ◽  
Polar Code ◽  
Successive Cancellation ◽  
Simulation Results ◽  
Encoding Method

In this paper, the uplink information-coupled polar-coded sparse code multiple access (PC-SCMA) system is proposed. For this system, we first design the encoding method of systematic joint parity check and CRC-aided (PCCA) polar code. Using the systematic PCCA-polar code as base code, the partially information-coupled (PIC) polar code is constructed. Then, a joint iterative detection and successive cancellation list (SCL)-decoding receiver is proposed for the PC-SCMA system. For the receiver, the coupled polar decoder’s extrinsic messages are calculated by the Bayes rule and soft cancellation (SCAN) algorithm. Based on the extrinsic information transfer (EXIT) idea, the PIC PCCA-polar code is optimized. Simulation results demonstrate that the PIC PCCA-PC-SCMA system outperforms the other polar (or LDPC) coded SCMA systems at various code rates and channel configurations. Additionally, compared with an uncoupled PC-SCMA system with SCL decoder, the complexity of PIC PCCA-PC-SCMA is reduced at a high Eb/N0

A New Way to Optimize LDPC Code in Multiple Access Channel

2014 ◽  
Vol 989-994 ◽  
pp. 4095-4099
Author(s):  
Jing Xi Zhang
Keyword(s):  
Differential Evolution ◽  
Maximum Degree ◽  
Multiple Access ◽  
Ldpc Codes ◽  
Ldpc Code ◽  
Multiple Access Channel ◽  
Access Channel ◽  
Noise Threshold ◽  
Irregular Ldpc Codes ◽  
Combination Technology

A new way to optimize the degree profiles for irregular LDPC codes in MAC is presented. The combination technology of differential evolution and density evolution is applied in the optimizing of degree distributions. By using a greedy algorithm we show the differential evolution method to seek the maximum noise threshold in MAC channels under different degree number and maximum degree condition.

SC-LDPC code design for Gaussian multiple access channel

2016 ◽  
Vol 10 (17) ◽  
pp. 2402-2406 ◽  
Author(s):  
Md. Noor-A-Rahim ◽  
Khoa D. Nguyen ◽  
Gottfried Lechner
Keyword(s):  
Multiple Access ◽  
Ldpc Code ◽  
Multiple Access Channel ◽  
Code Design ◽  
Access Channel
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