FEC Code Research Articles

A cascaded bit-weighted distribution matching for LDPC-coded PS-64QAM DMT in a high-speed Unamplified IM-DD system

We experimentally demonstrate the generation and transmission of probabilistic shaping (PS) 64-ary quadrature amplitude modulation (64-QAM) discrete multi-tone (DMT) signal with low-density parity-check (LDPC)-coded modulation based on two-stage bit-weighted distribution matching (TS-BWDM) in a high-speed unamplified intensity modulation and direct detection system. The TS-BWDM scheme is based on a two-stage bit-weighted inversion algorithm, which has the advantages of no complex multiplication and division operations and low hardware implementation complexity. As the key content of TS-BWDM, before FEC coding, the bit-weighted intervention operation is used to change the bit probability of a specific sequence in the parallel binary sequence. The two-stage bit-weighted inversion operation and one-stage weight-labeling bit insertion is performed for achieving the target symbol probability distribution. As a result, it does not add a significant amount of extra redundant bits. Additionally, the high-accuracy training symbols-based sampling frequency offset (SFO) estimation method and digital interpolation are used to compensate SFO. In our experiments, the TS-BWDM-based PS-64QAM DMT signals with a net rate of 157.3-Gb/s transmission over 10-km non-zero dispersion- shifted fiber can be achieved. The system performance is investigated under two LDPC code rates (3/4 and 9/10) and three PS parameter values (k = 3, 5 and 9). The experimental results show that the receiver power sensitivity and the system fiber nonlinear effect tolerance can be significantly improved compared with uniformly-distributed signals.

An ANALYSIS OF DVB-T2 TV BROADCAST TESTING DRIVE TEST AND FIELD STRENGTH METHODS IN THE JAKARTA SERVICE AREA

Indonesia has adopted DVB-T2 as the technology standard for terrestrial digital television broadcasting. This research aims to test and analyze the reception quality of DVB-T2 TV broadcasts in the DKI Jakarta service area. The research was conducted using drive test and field strength methods to test and evaluate the quality of digital television broadcasts. Tests were conducted in various locations in the DKI Jakarta service area using the Gsertel Hexylon TV Analyzer technical device to test DVB-T2 TV broadcast signals. The field strength test results were more accurate and higher values were generated than the drive test. Several parameters such as signal level and MER are evaluated and analyzed to find out what affects their values. The transmitter parameter settings such as modulation, FEC code rate, FFT Mode, Guard Interval, and Pilot Pattern greatly affect the signal level and MER values. The optimization performed on CH 24 also managed to maintain its signal level value of 18.19 dB and its MER of 55.01 dBµV to maintain broadcast stability during a technical failure of the transmitter on CH 1.

Machine Learning for Channel Coding: A Paradigm Shift from FEC Codes

Machine Learning for Channel Coding: A Paradigm Shift from FEC Codes

Modeling of a DVB-S2 Transmission Chain with Optimization of Adjustment Parameters for a Good Quality of the Reception Signal

Digital television is part of our daily lives. We took an interest in the DVB-S2 standard in particular, because it is the one that governs the transmission by satellite of multimedia content from television programs. With ever-changing user needs, there are new challenges that the DVB-S2 standard is no longer able to meet due to errors caused by weather and hardware limitations. The main purpose of a satellite TV transmission is to obtain a video signal in reception of the best possible quality and at a high bit rate. It is therefore important to determine all the factors which could intervene in the process of transmission and which have a negative impact on the yield at the reception of the signal. We therefore designed and simulated the DVB-S and DVB-S2 transmission chains with QPSK modulation (and an FEC coding rate of 1/2), on MATLAB software (Simulink), and with an AWGN channel for the sake of comparison performance between these two chains. Then we carried out the design of the DVB-S2 transmission chain with an RF (Radio Frequency) satellite channel, by materializing all the elements which intervene in the downlink to evaluate the performance of this chain according to the factors which influence and/or degrade the signal quality between transmission and reception at the receiving earth station. The main results obtained relate to the DVB-S2 transmission chain and were interpreted using the visualization of the error rate blocks: With an AWGN channel, increasing the signal-to-noise ratio decreases the rate of erroneous packets and therefore improves the quality of the received signal. With an RF satellite channel on the downlink: increasing the transmit power improves the receive performance, this is useful for correcting most RF imperfections; having larger parabolic antennas is an advantage because they have greater gains; this makes it possible to minimize the rate of erroneous packets. These simulations allowed us to determine the precise and numerical impact of RF degradations on the performance of the downlink DVB-S2 transmission chain.

Performance evaluation of free space optics communication system in the scenario of triple play service using probabilistic shaping scheme

An advanced triple-play-services (TPS) system based on probabilistic shaping (PS) scheme for free- space-optical (FSO) communication network is proposed and experimentally demonstrated for the first time. In this paper, the PS-32-quadrature amplitude modulation (QAM) 10 Gb/s data, PS-32-QAM 10 Gb/s voice and PS based 2.5 Gb/s HDTV signal are successfully transmitted over 600-m FSO link employing doublet lens scheme. The PS and polarization multiplexing technique both are helped to upgrade the spectral efficiency and improve the system performance. Normalized-generalized-mutual-information (NGMI) threshold is 0.92 at FEC code rate 9/10 for voice/data and 0.82 at FEC code rate 4/5 for video signal are selected to successfully execute the experiment. The spectral efficiency of our system is achieved by calculating the NGMI and shaping parameter (α), 13.6 bits/s/Hz (voice and data) and 10.41 bits/s/Hz (video) spectral efficiency are obtained at maximum α. Experimental results prove that PS based FSO communication system provides flexible data rate and greater spectrum efficiency and also be a powerful candidate to alleviate pressure on modern optical transport system.

Turbo Product Codes for Satellite Communication: a Survey

Turbo Product Codes (TPCs) with near Shannon capacity performance especially for high code rates allow decoding operations at a speed of several Mbps or more and has low error floor. In this paper, the characteristics of TPCs as FEC code, and their suitability for being a potential candidate in satellite communication applications are discussed. Emphasis is laid to highlight TPC's flexibility in attaining different code rates, improved coding gain especially for high code rates, benefits of different types of TPC construction and decoding modifications. The need for careful amalgamation of higher order modulation techniques with TPCs to achieve good spectral and power efficiency is discussed in detail. In addition, a deep learning based approach (neural-BP) for decoding of TPCs has been discussed. This is intended to improve the parallelism in TPC decoding and to reduce the implementation complexity. It is envisaged that the neural-BP decoding approach would lead to the design of hardware efficient decoders providing high Quality of Service (QoS) in satellite communication systems.

Blind Recognition of Parameters of Reed Solomon Code from Intercepted Erroneous Codewords

Error correcting codes are designed for reliable transmission of digital information over a noisy channel. Several papers have been published on blind identification of binary FEC codes but papers reported on the identification of non-binary error correcting codes are less. Due to its strong error correction capability, RS (Reed-Solomon) code is being used widely. So technique for blind recognition of RS code is required to analyse intercepted signal as well as for intelligent communication. This paper presents a technique for extraction of parameters of Reed-Solomon code from intercepted demodulated bitstream. The proposed algorithm is very simple and hence it is very practical for hardware implementation. Our approach has been verified using MATLAB simulation.

Blind Recognition of Forward Error Correction Codes Based on Recurrent Neural Network.

Forward error correction coding is the most common way of channel coding and the key point of error correction coding. Therefore, the recognition of which coding type is an important issue in non-cooperative communication. At present, the recognition of FEC codes is mainly concentrated in the field of semi-blind identification with known types of codes. However, the receiver cannot know the types of channel coding previously in non-cooperative systems such as cognitive radio and remote sensing of communication. Therefore, it is important to recognize the error-correcting encoding type with no prior information. In the paper, we come up with a neoteric method to identify the types of FEC codes based on Recurrent Neural Network (RNN) under the condition of non-cooperative communication. The algorithm classifies the input data into Bose-Chaudhuri-Hocquenghem (BCH) codes, Low-density Parity-check (LDPC) codes, Turbo codes and convolutional codes. So as to train the RNN model with better performance, the weight initialization method is optimized and the network performance is improved. The experimental result indicates that the average recognition rate of this model is 99% when the signal-to-noise ratio (SNR) ranges from 0 dB to 10 dB, which is in line with the requirements of engineering practice under the condition of non-cooperative communication. Moreover, the comparison of different parameters and models show the effectiveness and practicability of the algorithm proposed.

Design and Implementation of RS(450, 406) Decoder

Nowadays, in the field of data transmission between receiver and transmitter, the Reed Solomon code is used very frequently. FEC codes have two foremost and influential operations: (1) calculating parity symbols at the encoder side and (2) transmitting message symbols with parity symbols and decoding the received codeword at the second side by using the decoding algorithms. Gigabit automotive ethernet is used in the automotive car to provide better bandwidth for every kind of applications to connect functional components of the vehicles. This error correction technique is used in the gigabit automotive ethernet to reduce the channel noise during data transmission. RS (450, 406) is a powerful error correction techniques used in automotive ethernet. This paper focused only on the analysis of Reed Solomon decoding. Reed Solomon decoding is more efficient decoding techniques for correcting both burst and random errors. The critical steps of the Reed Solomon decoding are to solve the error evaluator and error calculator polynomial, which is also known as KES solver.

Paper] FPGA-based Performance Evaluation of FEC Codes for an Advanced ISDB-T

Paper] FPGA-based Performance Evaluation of FEC Codes for an Advanced ISDB-T

RETRACTED ARTICLE: Improved SOVA decoding for UEP wireless transmission of JPEG 2000 images over MIMO-OFDM systems

In this paper, improved Joint Source Channel (JSC) decoding using turbo codes is employed that are unified into JPEG 2000 decoder architecture. Rather than using conventional decoding approach, the proposed system provides reduced BER and complexity. This work deliberates Soft Output Viterbi Algorithm (SOVA) for its real time implementation features. Nevertheless, the algorithm suffers from performance degradation due to optimistic and correlation effects. The objective of this work is to enhance the performance of SOVA by using appropriate reduction factors that integrates and eliminates both these distortions. Acquired Integrated Factor is incorporated in the turbo decoders of the image transmission system. Bit Error rate and Peak Signal to Noise Ratio (PSNR) analysis is made by considering Additive White Gaussian Noise and Rayleigh fading channel through MATLAB simulation. To illustrate the visual quality improvement of the proposed scheme, comparison with other FEC codes is done with significant PSNR gains.

Rate Redundancy and Entropy Allocation for PAS-OFDM Based Mobile Fronthaul

From the perspective of an experimentalist, we discuss the comparison framework that ensures the same information rate in probabilistic shaping (PS) signals. Theoretically, the information rate can be tuned by adjusting the target entropy, scaling the signal bandwidth and adjusting FEC code rate. In practice, the information rate tuning should be based on the hardware feasibility (e.g., DAC resolution, available analog bandwidth, cost of rate adaptation). Adjusting a constellation entropy rate without considering FEC redundancy will cause an over-estimation of the PS system performance gain. To avoid the over-estimation issue, the modified pre-FEC threshold for PS signal is also proposed to estimate the system performance accurately. The modified pre-FEC threshold is obtained from the FEC code rate of PS signal. Moreover, we experimentally investigated the adaptive entropy allocation scheme in a millimeter-wave analog radio over fiber fronthaul using the modified pre-FEC threshold. By grouping the subcarriers into PS units and using the same QAM order, the proposed scheme can reduce the required data frame length as well as the processing complexity. Notably, this method requires neither dynamic FEC coding rate nor bandwidth adjusting method. Up to 2.5-dB power margins and a smoother pre-FEC performance among PS units are achieved in a frequency selective fading channel. If the modified FEC threshold were not used, it would induce up to 0.7-dB over-estimation in the received sensitivity. This indicates the importance of employing the proposed methods for comparison when FEC is used in combination with PS.

Efficient power allocation method for non orthogonal multiple access 5G systems

One of the hot research topics for the upcoming 5G (fifth-generation) wireless communication networks is the non orthogonal multiple access (NOMA) systems, where it have attracted both industrial and academic fields to improve the existing spectral efficiency. In fact, the multiuser detection process for NOMA systems is largely affected by the power distribution of the received signals. In this paper, a new method has been proposed to control the transmit power among active users in one of the promising NOMA systems; the interleave division multiple access (IDMA) which has been adopted here for consideration. Unlike conventional methods, where tedious mathematical computations are required; a simple and direct method has been derived. The proposed method has been applied to IDMA system with different FEC codes. The obtained results show that the proposed method outperforms the conventional one as compared to optimal results.

Hardware Architectures of Visible Light Communication Transmitter and Receiver for Beacon-based Indoor Positioning Systems

High-speed applications of Visible Light Communications have been presented recently in which response times of photodiode-based VLC receivers are critical points. Typical VLC receiver routines, such as soft-decoding of run-length limited (RLL) codes and FEC codes was purely processed on embedded firmware, and potentially cause bottleneck at the receiver. To speed up the performance of receivers, ASIC-based VLC receiver could be the solution. Unfortunately, recent works on soft-decoding of RLL and FEC have shown that they are bulky and time-consuming computations. This causes hardware implementation of VLC receivers becomes heavy and unrealistic. In this paper, we introduce a compact Polar-code-based VLC receivers. in which flicker mitigation of the system can be guaranteed even without RLL codes. In particular, we utilized the centralized bit-probability distribution of a pre-scrambler and a Polar encoder to create a non-RLL flicker mitigation solution. At the receiver, a 3-bit soft-decision filter was implemented to analyze signals received from the VLC channel to extract log-likelihood ratio (LLR) values and feed them to the Polar decoder. Therefore, the proposed receiver could exploit the soft-decoding of the Polar decoder to improve the error-correction performance of the system. Due to the non-RLL characteristic, the receiver has a preeminent code-rate and a reduced complexity compared with RLL-based receivers. We present the proposed VLC receiver along with a novel very-large-scale integration (VLSI) architecture, and a synthesis of our design using FPGA/ASIC synthesis tools.

Statistical BER Analysis of Wireline Links With Non-Binary Linear Block Codes Subject to DFE Error Propagation

This paper presents a statistical model to accurately estimate post-FEC BER for high-speed wireline links using standard linear block codes, such as the RS(544,514,15) KP4 and RS(528,514,7) KR4 codes. A hierarchical approach is adopted to analyze the propagation of PAM-symbol and FEC-symbol errors through a two-layer Markov model. A series of techniques including state aggregation, time aggregation, state reduction, and dynamic programming are introduced making the time complexity to compute post-FEC BER below 10−15 reasonable. Error bounds associated with each method are found. The efficiency of the proposed model allows it to handle a larger state space, more DFE taps, and more sophisticated linear block codes than prior work. A 4-PAM 60 Gb/s wireline transceiver fabricated in a 7 nm FinFET technology is used as a test vehicle to validate this model. Measured data with two different channels reveals that the statistical model can properly predict the post-FEC error floor with standard FEC codes. While this paper demonstrates the method for capturing DFE error propagation, the method is general and can be applied to model other communication systems having memory effects. Moreover, our proposed model can be easily extended to higher-level PAM schemes and other advanced equalizer architectures to assist in making architectural choices for wireline transceivers.

Energy Optimization For Wireless Video Transmission Employing Hybrid ARQ

In this paper we investigate energy-optimized wireless video transmission employing a hybrid automatic repeat request. We formulate the problem as maximizing the video quality, subject to a constraint on the wireless transmission energy consumption. We consider multiple parameters in multiple layers in a wireless video transmission system: transmit power, alphabet size, FEC code rate, maximum number of transmissions, and unequal video data importance. An analytical framework is proposed to include these parameters, which allows us to divide this problem into two sub-problems: data transmission and unequal error protection. The problem is tackled by solving the two sub-problems, which are done by exhaustive search and convex optimization, respectively. Simulations of different videos show that the proposed scheme outperforms methods using conventional data transmission and/or unequal error protection.

Performance Improvement of MIMO-OSTBC System with BCH-TURBO Code In Rayleigh Fading Channel

Recently, OSTBCs has become a widespread technique for signal transmission over wireless channels because of their diversity gain, but there are not designed to achieve an additional coding gain. Hence, OSTBCs must be concatenated with an external code which allows a significant coding gain.FEC (forward error correction) is a technique used for detecting and possibly correcting errors that can occur when messages are transmitted through a digital communication system, also for rendering the information more reliable. Thus, with staffing these coding techniques that are able to reach Shannon limits, in MIMO systems, better performances can be achieved by taking advantages of diversity and coding gains. The objective of this paper is to compare different FEC codes in Rayleigh fading channel and propose an appropriate code for MIMO-OSTBC systems. The simulation results reveal the performance of the proposed model

Embracing Corruption Burstiness: Fast Error Recovery for ZigBee under Wi-Fi Interference

The ZigBee communication can be easily and severely interfered by Wi-Fi traffic. Error recovery, as an important means for ZigBee to survive Wi-Fi interference, has been extensively studied in recent years. The existing works add upfront redundancy to in-packet blocks for recovering a certain number of random corruptions. Therefore, the bursty nature of ZigBee in-packet corruptions under Wi-Fi interference is often considered harmful, since some blocks are full of errors which cannot be recovered and some blocks have no errors but are still requiring redundancy. As a result, they often use interleaving to reshape the bursty errors, before applying complex FEC codes to recover the re-shaped random distributed errors. In this paper, we take a different view that burstiness may be helpful. With burstiness, the in-packet corruptions are often consecutive and the requirement for error recovery is reduced as “recovering any k consecutive errors” instead of “recovering any random k errors”. This lowered requirement allows us to design far more efficient code than the existing FEC codes. Motivated by this implication, we exploit the corruption burstiness to design a simple yet effective error recovery code using XOR operations (called ZiXOR). ZiXOR uses XOR code and the delay is significantly reduced. More, ZiXOR uses RSSI-hinted approach to detect in packet corruptions without CRC, incurring almost no extra transmission overhead. The testbed evaluation results show that ZiXOR outperforms the state-of-the-art works in terms of the throughput (by 47 percent) and latency (by 22 percent).

Application-Layer FEC Scheme Configuration Optimization via Hybrid Simulated Annealing

An optimization technique based on an adapted combination of simulated annealing (SA) and tabu search (TS) is presented. This method aims at finding near-optimal unequal error protection (UEP) application-layer FEC code configurations. This approach is intended to smartly protect audio and video transmission over IP networks when hard time restrictions apply. The considered code is a UEP version of the widely-used Pro-MPEG COP3 codes enabling the use of several matrices of dissimilar size and thus of unequal recovery capability. Finding the optimal configuration frequently requires the evaluation of a large solution space. So, to fulfill the imposed constraints, SA is adapted to the specifics of the scenario. In particular, the annealing schedule is conditioned by the real-time restrictions. Furthermore, solution neighborhood structures are determined by a proposed definition of distance between protection configurations, which, jointly with TS, conditions the selection of candidate solutions. Experimental results show a significantly improved performance of the optimization process, which invariably fulfills imposed timing constraints, at the expense of a very low distortion increase, when compared to using exhaustive search. These results allow the use of UEP Pro-MPEG COP3 codes for protecting video and audio transmission, which distinctly outperforms the standard code in a wide range of scenarios.

Compressed FEC Codes With Spatial-Coupling

An error floor problem is observed for a spatially coupled sparse-regression (SCSR) code with limited sparsity in low-to-medium rates. This letter presents a scheme that also involves spatial-coupling and compressed-sensing (SCCS) similar to SCSR. We replace position modulation in SCSR by a general concatenated forward error control code. We introduce a chaining principle that improves the error floor behavior of the underlying code. We show that SCCS based on chained Hadamard codes can offer significantly improved performance.