Optimal LDPC Code Research Articles

Novel Energy Optimized LDPC Codes for Next-Generation MIMO OFDM Systems

With the increasing prevalence of internet services in our daily lives, there is a growing demand for spectrum, resulting in a shortage of available frequencies. This is primarily due to the recent surge in subscribers seeking faster and more dependable data rates. Researchers globally have suggested various solutions to combat the spectrum shortage, such as technology, modulation schemes, beamforming, intelligent reflective surfaces, and channel coding schemes. With respect to channel coding, multiple codes have been proposed to overcome challenging and uncertain channel conditions. The paper introduces a DWT-incorporated LDPC STBC system as a solution to meet the rigorous demands of 5G deployment and use cases. A comparative analysis of the proposed codes is conducted to assess their suitability for next-generation communication networks, considering SNR and BER. Results indicate that the suggested code performs optimally, achieving a BER of 10-4 at 7dB SNR for Rayleigh Faded wireless channel. Therefore, the suggested code is deemed the most suitable option for the deployment of 5G and beyond systems.

Improved EXIT Algorithm Based on Gaussian Mixture Model and its Application to LDPC Construction in Coding Cooperative Systems With Hybrid Fading

In this study, an EXIT algorithm based on Gaussian mixture coding and multi-dimensional node information calculation is proposed. The objective is to solve the problem of performance analysis of cooperative communication and LDPC code construction under hybrid fading and impulse noise. First, Gaussian mixture model estimation of the decoding initialization information is performed by the expectation maximized algorithm. In addition, key parameters, such as weight, mean, and variance of the Gaussian mixture model are obtained. Then, the multi-dimensional information processing is performed on the variable node and the check node information in the traditional EXIT algorithm based on the multi-dimensional Gaussian mixture model and system symmetry analysis. Finally, the objective function of LDPC code optimization is constructed, the constraints are given, and the optimal LDPC code degree distribution is obtained by the differential evolution algorithm. The simulation results show that compared with the traditional regular and other irregular LDPC codes, the newly constructed degree distribution has better performance in waterfall characteristics and error floor characteristics. Such distribution provides a necessary method to analyze and optimize the performance of cooperative coding system under hybrid media or hybrid fading.

An Optimization Approach for an RLL-Constrained LDPC Coded Recording System Using Deliberate Flipping

For a recording system that has a run-length-limited (RLL) constraint, this approach imposes the hard error by flipping bits before recording. A high error coding rate limits the correcting capability of the RLL bit error. Since iterative decoding does not include the estimation technique, it has the potential capability of solving the hard error bits within several iterations compared to an LDPC coded system. In this letter, we implement density evolution and the differential evolution approach to provide a performance evaluation of unequal error protection LDPC code to investigate the optimal LDPC code distribution for an RLL flipped system.

Noncoherent LDPC-Coded Physical-Layer Network Coding Using Multitone FSK

A noncoherent two-way relaying system is developed using physical-layer network coding for improved throughput over conventional relaying in a fading channel. Energy-efficient noncoherent operation is achieved using multitone frequency shift keying (FSK). A novel soft-output demodulator is developed for the relay, and corresponding achievable exchange rates are found for Rayleigh fading and AWGN channels. Bit-error rate performance approaching the achievable rate is realized using a capacity-approaching channel code and a receiver architecture, which iterates between demodulation and channel decoding. Iterative decoding is performed feeding information back from the channel decoder to the demodulator. In addition, the error-rate performance is made to approach the achievable rate more closely by optimizing LDPC codes for this system. The energy efficiency improvement obtained by increasing the modulation order is more dramatic for the proposed physical-layer network coding scheme than it is for a conventional point-to-point system. Using optimized LDPC codes, the bit-error rate performance is improved by as much as 1.1 dB over a widely known standardized LDPC code, and comes to within 0.7 dB of the limit corresponding to the achievable rate. Throughout this paper, the performance for physical-layer network coding is compared with conventional network coding. When noncoherent FSK is used, physical-layer network coding enables higher achievable rates, and conventional network coding exhibits better energy efficiency at low rates.

A Survey on LDPC Codes for Cooperative Communications

LDPC codes are being considered as the codes that can approach the theoretical capacity limit while are not so complicated to implement. In this survey paper, the application of LDPC codes in decode-and-forward cooperative communications is investigated. Most of current researches focus on how to implement the LDPC-coded cooperation effectively. Here we consider two approaches: the first one uses factor graph decoupling and the other uses bilayer LDPC codes. The performance analysis of these schemes is carried out by density evolution and by EXIT chart analysis. In addition, the methods to design the optimal LDPC codes for these systems are also introduced. The numerical results show that we can reach very close to the capacity limit of the relay channels. Finally, simulation results of a new iterative decoding technique for LDPC codes are also presented.

Design optimization of low density parity check codes in multipath underwater acoustic channels

We propose an iterative decoding and equalizing scheme using low density parity check codes and decision feedback equalizer for underwater acoustic communication system. The scheme decodes and equalizes iteratively by linking a LDPC decoder with an adaptive DFE and feeding output soft information of the LDPC decoder to the DFE as priori information. We extend extrinsic information transfer (EXIT) charts to analyze the performance of LDPC codes in multipath underwater acoustic channels. Furthermore, we introduce an EXIT aided method of optimally designing the parameters of LDPC codes using modified differential evolution algorithm in multipath underwater acoustic channel. Design example and simulation are presented in two different underwater acoustic channels which are generated by BELLOP ray tracing model. Bit error rate of the proposed scheme is less than 10-5 as signal to noise rate (SNR) is greater than 8.5 dB in the channels. Compared the regular LDPC code with degree 3 and the Turbo code with feedback and feedforward generator polynomials 1+D+D 2+D 3 and 1+D 2+D 3, the optimized LDPC codes achieve gains of about 0.5 dB and 0.8 dB, respectively, at BER= 10-4 under the same code rate and block length.

Construction of non-binary quasi-cyclic LDPC codes by arrays and array dispersions - [transactions papers

This paper presents two algebraic methods for constructing high performance and efficiently encodable nonbinary quasi-cyclic LDPC codes based on arrays of special circulant permutation matrices and multi-fold array dispersions. Codes constructed based on these methods perform well over the AWGN and other types of channels with iterative decoding based on belief-propagation. Experimental results show that over the AWGN channel, these non-binary quasi-cyclic LDPC codes significantly outperform Reed-Solomon codes of the same lengths and rates decoded with either algebraic hard-decision Berlekamp-Massey algorithm or algebraic soft-decision Kötter- Vardy algorithm. Also presented in this paper is a class of asymptotically optimal LDPC codes for correcting bursts of erasures. Codes constructed also perform well over flat fading channels. Non-binary quasi-cyclic LDPC codes have a great potential to replace Reed-Solomon codes in some applications in communication environments and storage systems for combating mixed types of noises and interferences.

Optimal regular LDPC codes for the binary erasure channel

We prove that for any given R between 0 and 1 the best threshold value for a regular LDPC code of rate R with common variable degree v and common check degree c occurs when v is at least 3 and is minimal subject to the condition R=1-v/c.