Forward Error Correction (FEC) Building Block

Today, Forward Error Correcting (FEC) codes are mainly implemented in hardware, and many believe that their complexity prohibits their software implementation. This paper presents in detail how the performances of a software implementantion can be significantly improved. Different levels of optimization which are independent of the working environment are presented and discussed. The coding throughput of 100 Mbps on an UltraSparc 1 shows that FEC codes can be easily added to multimedia applications without requiring dedicated hardware support. As a case study, we use FEC codes to protect AAL5-PDUs from cell losses in ATM networks.

Real-time audio over a best-effort network, such as the Internet, frequently suffers from packet loss. To mitigate the impact of such packet loss, several research efforts and implementation studies advocate the use of forward error correction (FEC) coding. Although these prior works have pioneered promising and novel applications of to Internet audio, they do not definitively demonstrate the advantages of because they do not evaluate aggregate performance that results from multiplexing many like flows. We build on previous landmark works with a systematic study of for packet audio that characterizes the aggregate performance across all audio sources in the network. We refine the novel but ad hoc coding techniques proposed by Hardman, Sasse, Handley and Watson (see Proc. INET, 1995) into a formal framework that we call processing-based FEC (SFEC) and use our framework to more rigorously evaluate the relative merits of this approach. Through extensive simulation, we evaluate the scalability of SFEC for packet audio-i.e., the ability for a coding algorithm to improve aggregate performance when used by all sources in the network-and find that optimal signal quality is achieved when sources react to network congestion not by blindly adding FEC, but rather by adding in a controlled fashion that simultaneously constrains the source-coding rate. As a result, packet loss is mitigated without introducing more congestion, thus admitting a more scalable and effective approach than successively adding redundancy to a constant bit-rate source. While this result may seem intuitive, it has not been previously suggested in the context of Internet audio, and until now, has not been systematically studied.

The preference improvement resulting from modifications to the original ARQ scheme proposed by E.J. Weldon (1982) for use in systems with finite-receiver buffers was analyzed in a previous paper. A modification involving the use of parity retransmission is studied. One drawback of using forward error correcting (FEC) codes is that the parity bits result in a degradation in efficiency under good channel conditions: the maximum throughput is limited to the FEC code rate. Two type II ARQ schemes which overcome this problem are studied. Lower bounds on the throughputs of the two schemes are obtained. The throughput of the type II ARQ scheme is no longer limited by one-half the rate of the FEC code used. Under good channel conditions, the throughput with the type II ARQ scheme is equivalent to not using FEC; as the channel degrades, it approaches the throughput with a rate one-half FEC code.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Forward error correction (FEC) coding, modulation formats like differential phase shift keying (DPSK) and adaptive electronic equalization to mitigate, e.g. polarization mode dispersion (PMD) are some of the methods applied in current direct-detection optical communication systems, which are limited to a spectral efficiency of 1 bit/s/Hz. Coherent single-carrier QPSK systems with polarization multiplexing (PolMUX) allows to attain an spectral efficiency of up to 4 bit/s/Hz. However, to guarantee a bit error rate (BER) <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> adaptive multiple-input multiple-output (MIMO) equalization as well as outer FEC coding has to be included which results in less than 4 bit/s/Hz in commercial 40 Gbit/s systems. From wireline and wireless systems it is well known that larger symbol alphabets in combination with FEC coding (denoted as coded modulation) and orthogonal frequency division multiplexing (OFDM) can significantly enhance the spectral efficiency. However, in order to exploit the channel capacity of the fiber the modulation itself needs to be capacity achieving. In this contribution we apply capacity achieving constellations in an optical OFDM system and jointly design mapping and low-density parity-check (LDPC) codes for an iterative decoding scheme, namely bit-interleaved coded modulation with iterative decoding (BICM-ID). The authors expect this coding scheme to be most appropriate for future optical transponders to utilize long haul communications close to channel capacity.

Chapter 17 - Error-Control Coding Techniques and Applications

In future broadband networks based on asynchronous transfer mode (ATM) transmission and switching technology, the dominant kind of impairment is expected to be packet (ATM cell) losses. The use of forward error correction (FEC) codes has been proposed as a way to overcome these losses. However, the maximum length of a lost packet string that a packet loss recovery scheme can be designed to recover highly depends upon the temporal behavior between the adjacent packet loss bursts. Thus, a realistic model for describing the packet loss process is needed. The Gilbert model proposed for such purpose turns out to be an unrealistic model, since it fails to consider some important characteristics during the packet loss process. A more realistic model is advanced in this paper.

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.

Forward error correction (FEC) allows the receiver to correct erasure without asking retransmission. This advantage is significant for several applications where retransmission is not available or desirable. In recent years, applying FEC codes to peer-to-peer data distribution networks is an innovation. In this way, the downloader can efficiently reconstruct the data from the encoding symbols multicasted from multiple distributors. However, FEC codes suffer from pollution attacks where the attackers corrupt some encoding symbols such that the data can not correctly be reconstructed. Although Krohn et al. propose a homomorphic hash based verification scheme, the scheme is specifically designed for Fountain codes and the variants. That is, the scheme can not apply to other FEC codes and suffers from another specific attacks, distribution attacks. Thus, in this paper we propose a new verification scheme for polynomial based FEC codes like Vandermonde codes. The scheme can defend against not only pollution attacks but distribution attacks. The analysis also shows the security and feasibility of the proposed scheme.

Complex position code parallel combinatory spread spectrum (CPC/PC/SS) communication system with forward error correction (FEC) coding scheme is proposed in this paper, and performances are analyzed. CPC/PC/SS system with FEC coding scheme can be designed to have higher data transmission capability, even several times compared to ordinary PC/SS system on Gaussian channel.The proposed FEC coding is separately applied to the combination data of orthogonal codes and the state data of their transmitting orthogonal code, and less redundant FEC code is enough to the state data of orthogonal codes by this coding scheme. Therefore, the total information rate exceeds that offered by the conventional overall FEC coding is applied. Simulation results show that the error rate performance of the CPC/PC/SS systems equipped with the proposed FEC coding is lower than conventional PC/SS system.

Severe energy constraints and hence the low power communication requirements amplify the significance of the energy efficient and preferably cross-layer error control mechanisms in wireless sensor networks (WSN). In this paper, a cross-layer methodology for the analysis of error control schemes in WSNs is presented such that the effects of multi-hop routing and the broadcast nature of the wireless channel are investigated. More specifically, the cross-layer effects of routing, medium access and physical layers are considered. This analysis enables a comprehensive comparison of forward error correction (FEC) and automatic repeat request (ARQ) in WSNs. FEC schemes improve the error resiliency compared to ARQ. In a multi-hop network, this improvement can be exploited by reducing the transmit power (transmit power control) or by constructing longer hops (hop length extension), which can be achieved through channel-aware routing protocols. The results of our analysis reveal that for certain FEC codes, the hop length extension decreases both the energy consumption and the end-to-end latency subject to a target PER compared to ARQ. Thus, FEC codes can be regarded as an important candidate for delay sensitive traffic in WSNs. On the other hand, transmit power control results in significant savings in energy consumption at the cost of increased latency. Moreover, the cases where ARQ outperforms FEC codes are indicated for various end-to-end distance and target PER values

In off-line streaming, packet level erasure resilient Forward Error Correction (FEC) codes rely on the unrestricted buffering time at the receiver. In real-time streaming, the extremely short playback buffering time makes FEC inefficient for protecting a single path communication against long link failures. It has been shown that one alternative path added to a single path route makes packet level FEC applicable even when the buffering time is limited. Further path diversity, however, increases the number of underlying links increasing the total link failure rate, requiring from the sender possibly more FEC packets. We introduce a scalar coefficient for rating a multi-path routing topology of any complexity. It is called Redundancy Overall Requirement (ROR) and is proportional to the total number of adaptive FEC packets required for protection of the communication. With the capillary routing algorithm, introduced in this paper we build thousands of multi-path routing patterns. By computing their ROR coefficients, we show that contrary to the expectations the overall requirement in FEC codes is reduced when the further diversity of dual-path routing is achieved by the capillary routing algorithm.

We propose an explicit construction of full-diversity space-time block codes, under the constraint of an error correction capability. Furthermore, these codes are constructed in order to be suitable for a serial concatenation with an outer linear forward error correcting (FEC) code. We apply the binary rank criterion, and we use the threaded layering technique and an inner linear FEC code to define a space-time error-correcting code. When serially concatenated with an outer linear FEC code, a product code can be built at the receiver, and adapted iterative receiver structures can be applied. An optimized hybrid structure mixing MMSE turbo equalization and turbo product code decoding is proposed. It yields reduced complexity and enhanced performance compared to previous existing structures.

Superdense coding promises increased classical capacity and communication security but this advantage may be undermined by noise in the quantum channel. We present a numerical study of how forward error correction (FEC) applied to the encoded classical message can be used to mitigate against quantum channel noise. By studying the bit error rate under different FEC codes, we identify the unique role that burst errors play in superdense coding, and we show how these can be mitigated against by interleaving the FEC codewords prior to transmission. We conclude that classical FEC with interleaving is a useful method to improve the performance in near-term demonstrations of superdense coding.

Thanks to the large buffering time of off-line streaming applications, erasure resilient forward error correction (FEC) codes can improve the reliability of communication particularly well. However real-time streaming puts hard restrictions on the buffer size making FEC inefficient for combating long link failures on single path routes. Path diversity is orthogonal to buffering and permits real-time streaming to also benefit from application of FEC. We introduce a capillary routing algorithm offering layer by layer a wide range of multi-path routing topologies starting from a simple solution and evolving toward reliable routing patterns with highly developed path diversity. The friendliness of a multi-path routing pattern is rated by the overall amount of FEC redundancy required for combating the non-simultaneous failures of all links of the communication footprint. We rated the friendliness of a dozen of capillary routing layers, built on several hundreds of network samples obtained from a random walk mobile ad-hoc network (MANET). The overall requirement in redundant FEC codes decreases substantially as the spreading of the routing grows

Error control coding improves reliability and efficiency of wireless communication systems. This research delves into the latest advancements in error control coding schemes for wireless communication systems, with a specific focus on their application within the domain of Low Power Wide Area Networks (LPWANs) such as Narrowband Internet of Things (NB-IoT) systems, LoRa energy-efficient hardware design, random access control systems, and wireless sensor networks. In the context of LPWANs, particularly NB-IoT systems, we investigate the adaptive coding and modulation (ACM) in NB-IoT systems, which adapts coding rates and modulation techniques to changing channel circumstances. Comprehensive analysis of the literature review shows that the proposed approaches are more energy efficient and less error-prone than fixed coding and modulation schemes. Using Cell Design Methodology (CDM), Single Error Correction (SEC) codes are optimized for energy efficiency. Power and energy efficiency have improved in standard CMOS and CDM logic systems. This impacts IoT devices, memory storage, and security systems. Next, Forward Error Correction (FEC) is examined for ALOHA-based random-access control systems wherein packet loss rate and spectral efficiency metrics are mathematically calculated. FEC is beneficial, especially when time and frequency synchronization diverge. Monte Carlo simulations studied in the literature shows that FEC improves satellite communication systems. This review establishes benefits of FEC, notably in satellite communications systems. In addition, Wireless Sensor Networks (WSNs) error control techniques and network reliability and performance are examined along with Convolutional, Turbo, Low density parity check codes(LDPC), and Polar error correction coding (ECC) methods. We learn about their benefits, drawbacks, and implementation challenges by assessing their efficacy, efficiency, and applicability in wireless sensor networks (WSN) applications. This study further highlights advancements of energy-efficient error control coding when, integrated into network designs alongwith the trade-offs between efficacy and intricacy to help improve wireless communication networks. Finally, this study summarizes current error control coding approaches for wireless communication systems. We provide insights into improving reliability, energy conservation, and efficacy by examining ACM, CDM, FEC, and error correction coding (ECC) across varied domains including LPWAN and IoT technologies with earnest hope to facilitate researchers, engineers, and professionals working in the field of error control coding in wireless communication.