Forward Error Correction

Digital Video Broadcasting-Terrestrial second generation (DVB-T2) systems are increasingly deployed for high quality terrestrial broadcasting. However, low Signal-to-Noise Ratio (SNR) conditions in urban and fringe coverage areas pose significant challenges, resulting in elevated Bit Error Rates (BER) and degraded service reliability. Forward Error Correction (FEC) techniques, particularly Low-Density Parity-Check (LDPC) and Bose Chaudhuri Hocquenghem (BCH) codes, play a crucial role in mitigating transmission errors and ensuring robust communication. This study investigates a systematic approach to optimizing LDPC and BCH FEC schemes to enhance transmission reliability and minimize BER under low-SNR conditions in DVB-T2 networks. Using simulation-based analyses, the study evaluates multiple LDPC code rates (e.g., 1/2, 2/3, 3/4) in combination with BCH codeword lengths and error-correcting capabilities. Results indicate that an optimized LDPC (64800, 32400) configuration combined with a BCH (255, 239) code significantly reduces BER, achieving approximately 10⁻⁵ at an SNR of 2 dB, compared to a BER of 10⁻³ using standard DVB-T2 FEC configurations. Additionally, iterative decoding algorithms for LDPC were fine-tuned to balance convergence speed and error correction performance, demonstrating a 25% reduction in decoding iterations without compromising reliability. The analysis also explores trade-offs between redundancy, throughput and latency, highlighting the practical considerations for real-world deployment. The findings underscore that strategic optimization of LDPC/BCH FEC parameters is critical for maintaining broadcast quality in low-SNR scenarios. By enhancing error resilience and reducing BER, the proposed approach improves signal integrity, supports consistent reception in fringe areas and maximizes spectrum efficiency. This work provides a foundation for adaptive FEC strategies in future DVB T2 systems, enabling broadcasters to deliver reliable high-definition content even under challenging channel conditions.

Forward error correction (FEC) technique has been widely used in wireless communication and mass storage applications. In recent years, FEC has also become very important to optical communication because of its powerful error correcting ability. FEC codes provide performance gain by trading off coding gain with coding redundancy and decoding complexity. For transmission bit rate of 10 Gb/s or higher, coding redundancy of less than 25% is desired. Therefore, FEC schemes with moderate coding redundancy and tolerable decoding complexity are desirable and very important for high-speed long-haul optical systems. In this thesis, two FEC augmentation schemes, namely wavelength interleaving and errors-and-erasures decoding (E&ED), are proposed to improve the FEC performance of optical channels subjected to polarization mode dispersion (PMD) and chromatic dispersion (CD). Wavelength interleaving provides frequency diversity, hence reducing the effective error burst length and improving FEC performance without requiring more coding redundancy. In E&ED scheme, an erasure zone is used to collect highly unreliable received symbols called erasure symbols.

In order to improve the data transmission reliability of mobile ad hoc network, a routing scheme called integrated forward error correction multipath routing protocol was proposed, which integrates the techniques of packet fragmenting and forward error correction encoding into multipath routing. The scheme works as follows: adding a certain redundancy into the original packets; fragmenting the resulting packets into exclusive blocks of the same size; encoding with the forward error correction technique, and then sending them to the destination node. When the receiving end receives a certain amount of information blocks, the original information will be recovered even with partial loss. The performance of the scheme was evaluated using OPNET modeler. The experimental results show that with the method the average transmission delay is decreased by 20% and the transmission reliability is increased by 30%.

In Japan, the next generation of Integrated Services Digital Broadcasting — Terrestrial (ISDB-T) system is being developed for transmission of large-volume content services such as ultra high definition television (UHDTV). The system uses low density parity check (LDPC) code as the forward error correction (FEC) to improve its robustness. In particular, the performance of the system's FEC should be evaluated not only in additive white Gaussian noise (AWGN) environments, but also in multipath environments. Moreover, it would be desirable for the new FEC to have better performance than the previous one even in multipath environments. Previous research evaluated the transmission performance of LDPC code by using computer simulations of the propagation model. The actual propagation characteristics were not evaluated. In this paper, we describe the transmission performance of convolutional coded orthogonal frequency division multiplexing (CC-OFDM) and LDPC coded OFDM (LDPC-OFDM) in computer simulations using the same OFDM frame structure and propagation channels as measured in an outdoor experiment conducted in an urban area. We show that LDPC code outperforms CC in multipath environments and how the transmission performance depends on the code rate. In addition, we analyze the correlation between transmission performance and propagation channels.

In this paper we evaluate the performance of forward error correction (FEC) techniques in the presence of four wave mixing (FWM) and dispersion induced inter-symbol interference (ISI). A comparison with the detuning technique [1] is also presented, for the case of FWM penalty mitigation. FEC has been widely used in long haul submarine optical transmission systems, both repeated [2] and unrepeated [3] and its performance in the presence of polarization mode dispersion (PMD) has also been investigated [4,5]. The influence of non-linearities on optical systems that use FEC has recently been reported [6].

In this work we present a complete set of techniques devoted to offer robustness against frame losses in distributed speech recognition over packet-switched networks. The proposed scheme is composed of tree techniques, two of them are applied at the sender and the last one in the recognizer itself. On one hand, a media-specific forward error correction (FEC) technique is used to allow the recovery of information within the bursts. On the other hand, a recognizer-based technique well known by its remarkable ability to reduce the effects of long consecutive frame losses during recognition, the weighted Viterbi algorithm (WVA), is used to handle the additional information introduced by FEC codes. Moreover, a double stream strategy whereby interleaving can be applied along with FEC codes without any delay increase, is also applied. The application of interleaving allows to reduce the perceived burst length at the receiver, further improving the recognition performance. As a result, the proposed scheme can provide an acceptable performance even under extremely adverse channel conditions.

This paper studies TCP performance improvement in wireless and heterogeneous networks using Forward Error Correction (FEC) technique driven by TCP semantics. In the proposed scheme, called TCP-aware FEC, the amount of redundancy added to a packet at the sender node corresponds to the level of error protection and is computed as a function of TCP congestion window. The TCP-aware FEC becomes stronger for low congestion window values (experienced after a packet loss is detected), while the amount of added redundancy is reduced for the large window values approaching the capacity of the end-to-end link.

Online video transmissions over wireless networks are rising in popularity and have already become part of our daily life. In the meantime, it is necessary to address a number of challenges ranging from the scarce resources, time-varying, and high error rates, to the fluctuating bandwidth, unveiling the need for an adaptive mechanism to ensure a good video transmission. Adaptive Forward Error Correction (FEC) techniques with Quality of Experience (QoE) assurance are appropriate to deliver QoE-aware video data to wireless users in dynamic and high error rates networks. This paper proposes an adaptive Video-aware FEC and Fuzzy Logic-based mechanism to shield realtime video transmissions against packet loss in wireless networks, improving both user experience and the usage of resources. The benefits and drawbacks of the proposed mechanism compared with exiting work are demonstrated through simulations and assessed with QoE metrics.

Despite the emergence of voice over IP and videoconferencing services, recent studies have shown that the Internet still may not provide acceptable quality for interactive streaming applications. Among the major parameters that affect quality of service are packet loss rates and loss burst sizes. To mitigate the negative impact of losses, forward error correction (FEC) techniques can be employed. These work by adding extra information to the data stream. So, while FEC can potentially reduce the perceived effects of packet losses, it increases bandwidth requirements which in turn may increase the loss rate. Therefore, it is important to choose, in real time, the proper FEC scheme to provide the best performance to the application. We evaluate the performance of parity-based FEC schemes using an analytical loss model. Then, we develop an adaptive mechanism for FEC selection using a predictive model. We present the results of simulation experiments using real Internet measurements.

The remarkable development of mobile networks has enabled ubiquitous communications that has transformed the way people connect with each other. Meanwhile, the growing adoption of smartphones, tablets, and increasingly bandwidth-intensive applications and services is driving unprecedented mobile broadband traffic growth; therefore, finding state-of-the-art strategies for improving the wireless transmission reliability has emerged significantly. In particular, to enable significant mitigation of the detrimental effects of multipath fading, high-performance forward error correction (FEC) techniques have now recognized to become a vital part of modern digital wireless systems. This work is dedicated to address a class of high-performance iteratively decoded FECs referred to as serial concatenation of quadratic interleaved codes (SCQICs) wherein the reordering arrays for permutor and unscramble in the FEC encoding/decoding entities enjoy the remarkable algorithm proposed by Takeshita et al. seminal contribution which: (1) yields provisioning coding gain in both waterfall and error-floor regions of the bit error rate (BER) performance curve (2) enables possibility of analysis and compact representation, (3) requires straightforward implementation. We have observed that their utilization for the modern wireless communications applications remained scarce due to the lack of strong and comprehensive performance predictions over the different statistical wireless channel models. Hence, in this paper, we endeavor to analyze and examine the error-correction capability of SCQICs vastly from the various aspects, and investigate their resultant coding gains in different wireless Doppler environments.

Forward error correction (FEC) techniques are essential for optical core and optical access networks. In optical core networks, the emphasis is on high coding gains and extremely low output bit error rates, while allowing decoder realizations to operate at a throughput of 100 Gb/s and above. Optical access networks operate at 10 Gb/s or above and require low-complexity FEC codes with low power consumption. Coherent optical transmission with higher order modulation formats will become mandatory to achieve the high spectral efficiencies required in next-generation core networks. In this paper, we provide an overview of these requirements and techniques, and highlight how coding and modulation can be best combined in optical core networks. We also present guidelines for modulation and low-complexity FEC system design for optical access networks.

Chapter 17 - Error-Control Coding Techniques and Applications

In real-time video streaming, data packets are transported over the network from a transmitter to a receiver. The quality of the received video fluctuates as the network conditions change, and it can degrade substantially when there is considerable packet loss. Forward error correction (FEC) techniques can be used to recover lost packets by incorporating redundant data. Conventional FEC schemes do not work well when scalable video coding (SVC) is adopted. In this paper, we propose a novel FEC scheme that overcomes the drawbacks of these schemes by considering the reference picture structure of SVC and weighting the reference pictures more when FEC redundancy is applied. The experimental results show that the proposed FEC scheme outperforms conventional FEC schemes.

Path and server diversities have been used to guarantee reliable video streaming communication over wireless networks. In this paper, server diversity over mobile wireless ad hoc networks (MANETs) is implemented. Particularly, multipoint-to-point transmission together with multiple description coding (MDC) and forward error correction (FEC) technique is used to enhance the quality of service of video streaming over the wireless lossy networks. Additionally, the dynamic source routing (DSR) protocol is used to discover maximally disjoint routes for each sender and to distribute the workload evenly within the MANETs for video streaming applications. NS-2 Simulation study demonstrates the feasibility of the proposed mechanism and it shows that the approach achieves better quality of video streaming, in terms of the playable frame rate, reliability and real-time performance on the receiving side.

In this work, a concatenated forward error correction (FEC) scheme together with Orthogonal Frequency Division Multiplexing (OFDM) have been used for effective transmission of data/images over additive and fading channels. With a Bose Chaudhuri Hocquenghem (BCH) code as the outer code and a Low Density Parity Check (LDPC) code as the inner code, the transmission has been simulated over both the Gilbert-Elliot and ITU Rayleigh fading channels. The FEC parameters assumed throughout the simulations were obtained from the DVB-T2 standard and the Base Band (BB) frames were created by making use of shortening and zero-padding concepts. The results which have been presented in terms of BER and psycho-visual performances show the resilience of the FEC schemes and OFDM to channel impairments. The BER performances attained over the Gilbert-Elliot Channel (a channel that introduces burst errors when in the bad state) using LDPC only and BCH-LDPC concatenated coding indicated that the outer BCH coding will start to achieve a much lower BER after an SNR of 5 dB. Over the ITU-A Rayleigh fading channel it was observed that the performance increment due to the outer BCH encoder only become apparent after 6 dB when compared to the rate ¼ LDPC only coded system BER performance. Over the Gilbert-Elliot channel a BCH-LDPC coded QPSK-OFDM system would provide a BER of 3×10−4 at 6 dB while the same BER for the ITU Vehicular-A channel was possible at 6.6 dB.