Design of LDPC Coded CPM over Burst-Error Channels

There are several ways to use iterative decoding techniques with coded continuous phase modulation (CPM). This paper presents a method using parallel concatenation of convolutionally-coded CPM. All CPM schemes can be decomposed into a ring convolutional code and a memoryless signal mapper. This allows a properly designed convolutional code trellis to be combined with the CPM trellis, producing the joint trellis of a constituent code. Parallel concatenation of such constituent codes combined with iterative decoding yields very good performance. We present the results of code searches for two binary CPM schemes, each using bit interleaving and symbol interleaving. Simulation results using various length interleavers are also provided. Low complexity encoders are shown to perform better using bit interleaving, whereas encoders with higher complexity perform better with symbol interleaving.

Joint source and channel coding (JSCC) using combined trellis coded quantization (TCQ) and trellis coded continuous phase modulation (CPM) is studied. Optimal soft decoding based on the a posteriori probability (APP) algorithm for trellis coded CPM is developed for the considered systems. It has been demonstrated that the combined TCQ/CPM systems are both power and bandwidth efficient compared with the combined TCQ/TCM/8PSK systems. Furthermore, a TCQ design algorithm for the noisy channel is developed. The novelties of this work is the use of a soft decoder and the APP algorithm for combined TCQ/CPM systems.

In this paper, a doubly-iterative linear receiver, equipped with a soft-information aided frequency domain minimum mean-squared error (MMSE) equalizer, is proposed for the combined equalization and decoding of coded continuous phase modulation (CPM) signals over long multipath fading channels. In the proposed receiver architecture, the front-end frequency domain equalizer (FDE) is followed by the soft-input, softoutput (SISO) CPM demodulator and channel decoder modules. The receiver employs double turbo processing by performing back-end demodulation/decoding iterations per each equalization iteration to improve the a priori information for the front-end FDE. As presented by the computational complexity analysis and simulations, this process provides not only a significant reduction in the overall computational complexity, but also a performance improvement over the previously proposed iterative and noniterative MMSE receivers.

With the rapid development of Ethernet, RS (544, 514) (KP4-forward error correction), which was widely used in high-speed Ethernet standards for its good performance-complexity trade-off, may not meet the demands of next-generation Ethernet for higher data transmission speed and better decoding performance. A concatenated code based on KP4-FEC has become a good solution because of its low complexity and excellent compatibility. For concatenated codes, aside from the selection of outer and inner codes, an efficient interleaving scheme is also very critical to deal with different channel conditions. Aiming at burst errors in wired communication, we propose a novel matrix interleaving scheme for concatenated codes which set the outer code as KP4-FEC and the inner code as Bose-Chaudhuri-Hocquenghem (BCH) code. In the proposed scheme, burst errors are evenly distributed to each BCH code as much as possible to improve their overall decoding efficiency. Meanwhile, the bit continuity in each symbol of the RS codeword is guaranteed during transmission, so the number of symbols affected by burst errors is minimized. Simulation results demonstrate that the proposed interleaving scheme can achieve a better decoding performance on burst-error channels than the original scheme. In some cases, the extra coding gain at the bit-error-rate (BER) of 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−15</sup> can even reach 1 dB.

Link-16, an excellent tactical data link developed by US army, provides security and reliable tactical data for aeroamphibious platforms and it's communication terminal, Joint Tactical Information Distribution System (JTIDS), features Reed-Solomon (RS) codes for random error, interlaced codes to for burst error. In the past decades, a variety of new-style electromagnetic weapons are constantly emerging and military communication environment becomes more and more complex and inscrutability, the BER performance of original JTIDS will be difficult to adapt to modern warfare increasingly harsh channel environment. In this paper, we establish a new burst-error channel to simulate the attack of electromagnetic weapons and we find a sharp fall in jam-resistant performance of original JTIDS. Furthermore, a new JTIDS based on LDPC codes over GF(q) which are capacity-approaching codes is proposed for confronting the new channel model.

The detection of convolutional codes over rings suitable for continuous phase modulation (CPM) are presented based on the Rimoldi's Decomposition of CPM. Because the ring convolutional codes are on the same ring as the inner codes of CPM, We can use reduced state sequence detection (RSSD) to analyze and detect the overall encoder. Numerical result shows the detection complexity of this RSSD is significantly reduced with a very small degradation in error performance.

In distributed speech recognition, the speech features are computed on a mobile device, compressed, and sent over a network to a speech recognition server, where the Viterbi search and hidden Markov modeling take place. We examine some error concealment methods for distributed speech recognition over burst error channels. We consider interpolation and interleaving, and we present a novel use of the stochastic weighted Viterbi recognition algorithm to increase robustness against interpolated features. We examine interleaving at both the frame level and codebook index level. Channel errors are simulated using a Gilbert model, and the performance of our algorithm is compared with other techniques, including the ETSI DSR standard, on a digits task and a large vocabulary task. Coupled with interleaving and interpolation, our algorithm can provide accuracy as high as 96.7% on a digit recognition task during an average bit error probability of 1/20. On the more difficult WSJ task, the accuracy without bit errors is 85.7%. Using our algorithm, we can achieve 82.9% accuracy with an average bit error probability of 1/30.

A new Markovian model for burst-error processes is herein presented. Our basic idea consists of imposing a convenient structure on this model, with the double purpose of reproducing the generation of some typical patterns of burst error sequences and facilitating the maximum-likelihood estimation of the model's parameters. A simple procedure for calculating the maximum-likelihood metric of those parameters is derived and numerically maximized to fit the model to data. Some numerical results are presented that illustrate the effectiveness of this approach in reproducing very well important statistics of burst-errors processes.

In this paper, we evaluate the performances of the Reed–Solomon (RS) and low density parity check (LDPC) codes in order to propose an efficient coding system for the outer code in high density optical recording channels. Hard decision decoding (HDD) RS code, iterative soft decision decoding (SDD) RS code or LDPC code is used as the outer code and LDPC code is used as the inner code. We compare the bit error rate (BER) performance of each coding system for various code rates, code lengths and burst errors. Simulation results show that the LDPC code has a better BER performance than the HDD RS and iterative SDD RS codes as the outer code in high density optical channels. Therefore, the LDPC code could be more attractive as the outer code than the RS code in high density optical channels.

Low-density parity-check (LDPC) codes are promising for low code rate applications, however its competitiveness over BCH codes in the high code rate region is not well studied. In this work, we compare the Euclidean geometry (EG) LDPC and BCH codes of the length 1,023, 4,095, and 16,383 that have the code rates of 0.75~0.85. Hard-decision input data are applied to both decoders, and the EG-LDPC codes are decoded using the layered bit-flipping (BF) algorithm. Since the number of needed iterations for LDPC decoding depends on the channel condition, both decoders are designed to have the similar minimum throughput. Not only error performance but also hardware complexity and power consumption of these decoders are compared.

Introduction: In modern systems for communication, data storage and processing the error-correction capability of codes are estimated for memoryless channels. In real channels the noise is correlated, which leads to grouping error in bursts. A traditional method to fight this phenomenon is channel decorrelation, which does not allow developing of coding schemes, mostly utilizing the channel capacity. Thus the development of bursts decoding algorithms for arbitrary linear codes is the actual task. Purpose: To develop a single error burst decoding algorithm for linear codes, to estimate the decoding error probability and computational complexity. Results: Two approaches are proposed to burst error correction. The first one is based on combining the window sliding modification of well-known bit-flipping algorithm with preliminary analysis of the structure of parity check matrix. The second one is based on the recursive procedure of constructing the sequence of certain events which, in the worst case, performs the exhaustive search of error bursts, but in many cases the search may be significantly decreased by using the proposed heuristics. The proposed recursive decoding algorithm allows a guaranteed correction of any single error bursts within burst-correction capability of the code, and in many cases beyond the burst-correction capability. The complexity of this algorithm is significantly lower than that of a bit flipping algorithm if the parity-check matrix of the code is sparse enough. An alternative hybrid decoding algorithm is proposed utilizing the bit-flipping approach and showing the error probability and completion time comparable to the recursive algorithm, however, in this case the possibility of a guaranteed burst correction hardly can be proved. Practical relevance: The proposed decoding methods may be used in modern and perspective communication systems, allowing energy saving and increasing reliability of data transmission by better error performance and computational complexity.

Visible light communications integrated with Internet-of-Things has numerous applications in indoor wireless communications and it requires high data rates and flicker mitigation. Flicker mitigation is an important consideration since light emitting diodes are simultaneously used for illumination and communications. Several run-length limited (RLL) codes have been proposed in the literature for flicker mitigation with trade-offs between code rate, bit error performance, encoding and decoding complexities. However, there are no generalized algorithms for high rate codes generation with low complexity encoding and decoding. Hence, in this paper, we propose generalized algorithm for generating high rate RLL codes with low complexity encoding and decoding. The proposed codes can be used for flicker mitigation conditioned on maximum flickering time period (MFTP). The performance of the proposed codes is compared with existing codes in terms of various metrics like code rate, minimum Hamming distance, peak to average power ratio, run-length, and bit error rate. We show that the proposed codes mitigate flicker conditioned on MFTP and provide high data rates with low complexity encoding and decoding compared to the codes in the literature.

Jamming is a simple but efficient attack method that challenges communications while traditional physical-layer defence solutions are limited. Recently, index modulation (IM) is proposed to enable index transmission in addition to data symbol transmission, which gains resistance against jamming but with limited efficacy. This letter proposes a coding split and adjustment (CSA) framework for low-density parity-check (LDPC) coding assisted orthogonal frequency division multiplexing with IM (OFDM-IM) to enhance its anti-jamming capability. CSA splits the traditionally single system code rate into an index code rate and a data code rate, each independently adjusted based on jamming impacts to error performance. Simulation results verify that OFDM-IM with CSA exhibits superior error performance over traditional OFDM-IM and OFDM in three investigated jamming scenarios. Moreover, this letter reveals that the CSA assisted OFDM-IM can still recover signals while OFDM-IM and OFDM completely fail under high jamming power.

Continuous phase modulation (CPM) systems for noncoherent coded transmission are proposed and analyzed. Specifically, the application of a feedback-free modulator is regarded. For demodulation, a receiver structure which requires only two or three linear filters is considered. For decoding, noncoherent sequence estimation (NSE) with Viterbi decoding and per-survivor processing is applied. Noteworthy, in our approach the problems of low-complexity filtering and reduced-state decoding can be treated separately. Since we give a recursive formula for the phase reference symbol necessary for NSE metric calculation, computational effort is further decreased. Overall, in terms of complexity, the proposed noncoherent receiver provides significant advantages over approaches in the literature. The high performance of the novel noncoherent CPM system is confirmed by simulation results.

In this paper, in order to improve bit error performance, bandwidth efficiency and reduction of complexity compared to related schemes such as turbo codes, we combine low density parity check (LDPC) codes and continuous phase frequency shift keying (CPFSK) modulation and introduce a new scheme, called ‘low density parity check coded‐continuous phase frequency shift keying (LDPCC‐CPFSK)’. Since LDPC codes have very large Euclidean distance and use iterative decoding algorithms, they have high error correcting capacity and have very close performances to Shannon limit. In all communication systems, phase discontinuities of modulated signals result extra bandwidth requirements. Continuous phase modulation (CPM) is a powerful solution for this problem. Beside CPM provides good bandwidth efficiency; it also improves bit error performance with its memory unit. In our proposed scheme, LDPC and CPFSK, which is a special type of CPM, are considered together to improve both error performance and bandwidth efficiencies. We also obtain error performance curves of LDPCC‐CPFSK via computer simulations for both regular and irregular LDPC code. Simulation results are drawn for 4‐ary CPFSK, 8‐ary CPFSK and 16‐ary CPFSK over AWGN, Rician and Rayleigh fading channels for maximum 100 iterations, while the frame size is chosen as 504. Copyright © 2006 John Wiley &amp; Sons, Ltd.