A Decoding Algorithm for LDPC Codes Over Erasure Channels with Sporadic Errors

none4An efficient decoding algorithm for low-density parity-check (LDPC) codes on erasure channels with sporadic errors (i.e., binary error-and-erasure channels with error probability much smaller than the erasure probability) is proposed and its performance analyzed. A general single-error multiple-erasure (SEME) decoding algorithm is first described, which may be in principle used with any binary linear block code. The algorithm is optimum whenever the non-erased part of the received word is affected by at most one error, and is capable of performing error detection of multiple errors. An upper bound on the average block error probability under SEME decoding is derived for the linear random code ensemble. The bound is tight and easy to implement. The algorithm is then adapted to LDPC codes, resulting in a simple modification to a previously proposed efficient maximum likelihood LDPC erasure decoder which exploits the parity-check matrix sparseness. Numerical results reveal that LDPC codes under efficient SEME decoding can closely approach the average performance of random codes.noneG. Liva; E. Paolini; B. Matuz; M. ChianiG. Liva; E. Paolini; B. Matuz; M. Chian

Reliable multicast transport by satellite: a hybrid satellite/terrestrial solution with erasure codes

Geostationary satellites are an efficient way to provide a large scale multipoint communication service. In the context of reliable multicast communications, a new hybrid satellite/terrestrial approach is proposed. It aims at reducing the overall communication cost using satellite broadcasting only when enough receivers are present, and terrestrial transmissions otherwise. This approach has been statistically evaluated for a particular cost function and seems interesting. Then since the hybrid approach relies on Forward Error Correction, several practical aspects of MDS codes and LDPC codes are investigated in order to select a code

A protection scheme for multimedia packet streams in bursty packet loss networks based on small block low-density parity-check codes

This paper proposes an enhanced forward error correction (FEC) scheme based on small block low-density parity-check (LDPC) codes to protect real-time packetized multimedia streams in bursty channels. The use of LDPC codes is typically addressed for channels where losses are uniformly distributed (memoryless channels) and for large information blocks. This work suggests the use of this type of FEC codes at the application layer, in bursty channels (e.g., Internet protocol (IP)-based networks) and for real-time scenarios that require low transmission latency. To fulfil these constraints, the appropriate configuration parameters of an LDPC scheme have been determined using small blocks of information and adapting the FEC code to be capable of recovering packet losses in bursty environments. This purpose is achieved in two steps. The first step is performed by an algorithm that estimates the recovery capability of a given LDPC code in a burst packet loss network. The second step is the optimization of the code: an algorithm optimizes the parity matrix structure in terms of recovery capability against the specific behavior of the channel with memory. Experimental results have been obtained in a simulated transmission channel to show that the optimized LDPC matrices generate a more robust protection scheme against bursty packet losses for small information blocks

Recent Results on the Implementation of a Burst Error and Burst Erasure Channel Emulator Using an FPGA Architecture

The behaviour of a transmission channel may be simulated using the performance abilities of current generation multiprocessing hardware, namely, a multicore Central Processing Unit (CPU), a general purpose Graphics Processing Unit (GPU), or a Field Programmable Gate Array (FPGA). These were investigated by Cullinan et al. in a recent paper (published in 2012) where these three devices capabilities were compared to determine which device would be best suited towards which specific task. In particular, it was shown that, for the application which is objective of our work (i.e., for a transmission channel simulation), the FPGA is 26.67 times faster than the GPU and 10.76 times faster than the CPU. Motivated by these results, in this paper we propose and present a direct hardware emulation. In particular, a Cyclone II FPGA architecture is implemented to simulate a burst error channel behaviour, in which errors are clustered together, and a burst erasure channel behaviour, in which the erasures are clustered together. The results presented in the paper are valid for any FPGA architecture that may be considered for this scope

Link-Layer Coding for GNSS Navigation Messages

In this paper, we face the problem of ensuring reliability of Global Navigation Satellite Systems (GNSSs) in harsh channel conditions, where obstacles and scatter cause long outage events that cannot be counteracted with channel coding only. Our novel approach, stemming from information-theoretic considerations, is based on link-layer coding (LLC). LLC allows us to significantly improve the efficiency in terms of time-to-first-fix with respect to current operational GNSSs, which adopt carousel transmission. First, we investigate the maximum theoretical LLC gain under different Land Mobile Satellite channel conditions. Then, some practical LLC coding schemes, namely, fountain codes and a novel low-density parity-check plus low-rate repetition coding, are proposed and tested in realistic single-satellite and multi-satellite Land Mobile Satellite scenarios, considering the Galileo I/NAV message as study case. Simulation results show that our designed schemes largely improve on carousel transmission and achieve near-optimal performance with limited increase in complexity. Also, back-compatibility of LLC is assessed with respect to present-time GNSS specifications. © 2018 Institute of Navigation

Analysis and optimization of the satellite-to-plane link of an aeronautical global system

En aquest projecte s'ha analitzat i optimitzat l'enllaç satèl·lit amb avió per a un sistema aeronàutic global. Aquest nou sistema anomenat ANTARES està dissenyat per a comunicar avions amb estacions base mitjançant un satèl·lit. Aquesta és una iniciativa on hi participen institucions oficials en l'aviació com ara l'ECAC i que és desenvolupat en una col·laboració europea d'universitats i empreses. El treball dut a terme en el projecte compren bàsicament tres aspectes. El disseny i anàlisi de la gestió de recursos. La idoneïtat d'utilitzar correcció d'errors en la capa d'enllaç i en cas que sigui necessària dissenyar una opció de codificació preliminar. Finalment, estudiar i analitzar l'efecte de la interferència co-canal en sistemes multifeix. Tots aquests temes són considerats només per al "forward link". L'estructura que segueix el projecte és primer presentar les característiques globals del sistema, després centrar-se i analitzar els temes mencionats per a poder donar resultats i extreure conclusions.En este proyecto se ha analizado y optimizado el enlace satélite a avión para un sistema aeronáutico global. Este nuevo sistema, ANTARES, está diseñado para comunicar aviones y estaciones base mediante un satélite. Esta es una iniciativa europea en la que participan varias instituciones oficiales en aviación como el ECAC y es desarrollada en una colaboración europea de universidades y empresas. El trabajo llevado a cabo en este proyecto comprende básicamente tres aspectos. El diseño y análisis de la gestión de recursos. La idoneidad de usar corrección de errores en la capa de enlace y en caso que sea necesario diseñar una opción de codificación preliminar. Finalmente, estudiar y analizar el efecto de la interferencia co-canal en sistemas multihaz. Todos estos temas se consideran sólo en el "forward link". La estructura que sigue el trabajo es, primero presentar las características globales del sistema, luego centrarse y analizar los temas mencionados para finalmente dar resultados y extraer conclusiones.In this project it is analyzed and optimized the satellite-to-plane link of an aeronautical global system. This new upcoming system called ANTARES is intended for communicating airplanes and ground stations through a satellite system. This is a European initiative involving official institutions in terms of aviation such as the ECAC and developed in a European collaboration of universities and companies. The work carried out in the project comprehends basically three issues. The Radio Resource Management analysis and design. Analyze the suitability of using Link Layer-Forward Error Correction in the system and in case it is necessary design a preliminary coding option. Finally, study and analyze the effect of the co-channel interference in multibeam systems. All these issues are considered only for the forward link of the system. The structure of the project is as follows, first present the global characteristics of the system, then focus and analyze the mentioned subjects and finally give results and take conclusions on the work

Memory and Complexity Analysis of On-the-Fly Coding Schemes for Multimedia Multicast Communications

A new class of erasure codes for delay-constraint applications, called on-the-fly coding, have recently been introduced for their improvements in terms of recovery delay and achievable capacity. Despite their promising characteristics, little is known about the complexity of the systematic and non-systematic variants of this code, notably for live multicast transmission of multimedia content which is their ideal use case. Our paper aims to fill this gap and targets specifically the metrics relevant to mobile receivers with limited resources: buffer size requirements and computation complexity of the receiver. As our contribution, we evaluate both code variants on uniform and bursty erasure channels. Results obtained are unequivocal and demonstrate that the systematic codes outperform the nonsystematic ones, in terms of both the buffer occupancy and computation overhead

Analysis and evaluation of adaptive LDPC AL-FEC codes for content download services

This paper proposes the use of adaptive low density parity check (LDPC) application layer-forward error correction (AL-FEC) codes for content download services over erasure channels. In adaptive LDPC codes, clients inform the content download server of the losses they are experiencing. Using this information, the server makes forward error correction (FEC) parity symbols available to the client at an optimum code rate. This paper presents an analytical model of the proposed adaptive LDPC codes. The model is validated through measurements realized with an application prototype. In addition, results show the performance of these codes in different scenarios, compared to the performance of nonadaptive AL-FEC, optimum LDPC AL-FEC codes, and an almost ideal rateless code. Adaptive LDPC AL-FEC codes achieve download times similar to almost ideal rateless codes with less coding complexity, at the expense of an interaction channel between server and clients.De Fez Lava, I.; Fraile Gil, F.; Belda Ortega, R.; Guerri Cebollada, JC. (2012). Analysis and evaluation of adaptive LDPC AL-FEC codes for content download services. IEEE Transactions on Multimedia. 60(3):641-650. doi:10.1109/TMM.2012.2190392S64165060