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

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

Video over DSL with LDGM Codes for Interactive Applications

Digital Subscriber Line (DSL) network access is subject to error bursts, which, for interactive video, can introduce unacceptable latencies if video packets need to be re-sent. If the video packets are protected against errors with Forward Error Correction (FEC), calculation of the application-layer channel codes themselves may also introduce additional latency. This paper proposes Low-Density Generator Matrix (LDGM) codes rather than other popular codes because they are more suitable for interactive video streaming, not only for their computational simplicity but also for their licensing advantage. The paper demonstrates that a reduction of up to 4 dB in video distortion is achievable with LDGM Application Layer (AL) FEC. In addition, an extension to the LDGM scheme is demonstrated, which works by rearranging the columns of the parity check matrix so as to make it even more resilient to burst errors. Telemedicine and video conferencing are typical target applications

High Speed S-band Communications System for Nanosatellites

3Cat-3 is a nanosatellite based on the 6 unit cubesat standard. Its payload is an optical multispectral imager that imposes stringent downlink requirements for a nanosatellite. This TFG is based on the experience gained in 3Cat-1 and 3Cat-2 communications systems to develop a "high speed" (goal >= 5 Mbps) downlink for nanosatellites based on the TI CC3200.In order to accomplish the objectives of the next generation of nanosatellites high-speed downlinks have to be designed. This goal faces stringent design constraints as nanosatellites are limit in power, processing capabilities and dimensions. In the quest for higher bit rates the widely used VHF band has to be replaced for higher frequency bands and the link budged margin tightened, decreasing the SNR at reception. The proposed solution uses COTS 2.4 GHz WiFi adapters as transceivers. Range limitations imposed by the default 802.11 mode of operation are bypassed by using packet forging and injection at transmission jointly with monitor mode at reception. A loss-resilient unidirectional downlink is achieved by using application-layer encoding by means of LPDC-Staircase codes. This solution has been already implemented in 3CAT-2, a 6 unit cubesat GNSS-R mission to be launched in July 2016. In addition, bursts of errors are combated by using Reed-Solomon. The system has been tested under Doppler shift and scintillation effects, and a 188Km link between Barcelona and Mallorca has been performed, showing satisfactory results

A personalized system for scalable distribution of multimedia content in multicast wireless networks

The final publication is available at Springer via http://dx.doi.org/10.1007/s11042-014-2139-3This paper presents a novel architecture for scalable multimedia content delivery over wireless networks. The architecture takes into account both the user preferences and context in order to provide personalized contents to each user. In this way, third-party applications filter the most appropriate contents for each client in each situation. One of the key characteristics of the proposal is the scalability, which is provided, apart from the use of filtering techniques, through the transmission in multicast networks. In this sense, content delivery is carried out by means of the FLUTE (File Delivery over Unidirectional Transport) protocol, which provides reliability in unidirectional environments through different mechanisms such as AL-FEC (Application Layer Forward Error Correction) codes, used in this paper. Another key characteristic is the context-awareness and personalization of content delivery, which is provided by means of context information, user profiles, and adaptation. The system proposed is validated through several empirical studies. Specifically, the paper presents evaluations of two types that collect objective and subjective measures. The first evaluate the efficiency of the transmission protocol, analyzing how the use of appropriate transmission parameters reduces the download time (and thus increasing the Quality of Experience), which can be minimized by using caching techniques. On the other hand, the subjective measures present a study about the user experience after testing the application and analyze the accuracy of the filtering process/strategy. Results show that using AL-FEC mechanisms produces download times until four times lower than when no protection is used. Also, results prove that there is a code rate that minimizes the download time depending on the losses and that, in general, code rates 0.7 and 0.9 provide good download times for a wide range of losses. On the other hand, subjective measures indicate a high user satisfaction (more than 80 %) and a relevant degree of accuracy of the content adaption.This work is supported in part by the Ministerio de Economia y Competitividad of the Government of Spain under project COMINN (IPT-2012-0883-430000) and by the project PAID/2012/313 from the PAID-05-12 program of the Vicerrectorado de Investigacion of the Universitat Politecnica de Valencia.De Fez Lava, I.; Gil Pascual, M.; Fons Cors, JJ.; Guerri Cebollada, JC.; Pelechano Ferragud, V. (2014). A personalized system for scalable distribution of multimedia content in multicast wireless networks. 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IEEE Transactions on Multimedia 14(3):641–650de Fez I, Fraile F, Guerri JC (2013) Effect of the FDT transmission frequency for an optimum content delivery using the FLUTE protocol. Computer Communications 36(12):1298–1309de Fez I, Guerri JC (2014) An adaptive mechanism for optimal content download in wireless networks. IEEE Transactions on Multimedia 16(4):1140–1155Du R, Safavi-Naini R, Susilo W (2003) Web filtering using text classification (2003). 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Journal of Zhejiang University 7(5):873–884Hsieh CC, Lin CH, Chang WT (2009) Design and implementation of the interactive multimedia broadcasting services in DVB-H. IEEE Transactions on Consumer Electronics 55(4):1779–1787Kellerer H, Pferschy U, Pisinger D (2004) Knapsack problems. SpringerKorpipaa P, Malm EJ, Rantakokko T, Kyllonen V, Kela J, Mantyjarvi J, Hakkila J, Kansala I (2006) Customizing user interaction in smart phones. IEEE Pervasive Computing 5:82–90Kuppusamy KS, Aghila G (2012) A personalized web page content filtering model based on segmentation. Int Journal of Information Sciences and Techniques (IJIST) 2(1):41–51Kutscher D, Greifenberg J, Loos K (2007) Scalable DTN distribution over uni-directional links. Proc. of the SIGCOMM workshop on networked systems in developing regions (NSDR), Kyoto, Japan: article no. 6Lewis JR (1995) Ibm computer usability satisfaction questionnaires: psychometric evaluation and instructions for use. Int J Hum Comput Interact 7(1):57–78Liang L, Cruichkshank H, Sun Z, Kulatunga C, Fairhurst G (2010) The integration of TESLA and FLUTE over satellite networks. Proc. of the IEEE Global Telecommunications Conference (Globecom), Miami, FL, USA:1–6Lohmar T, Huschke J (2009) Radio resource optimization for MBMS file transmissions. Proc. of the IEEE Int Symposium on Broadband Multimedia Systems and Broadcasting (BMSB), Bilbao, Spain:1–7Neumann C, Roca V, Walsh R (2005) Large scale content distribution protocols. ACM Computer Communication Review 35(5):85–92Paila T, Walsh R, Luby M, Roca V, Lehtonen R (2012) FLUTE – File Delivery Over Unidirectional Transport. IETF RFC 6726Paolini E, Varrella M, Chiani M, Matuz B, Liva G (2008) Low-complexity LDPC codes with near-optimum performance over the BEC. Proc. Adv Satellite Mobile Systems (ASMS), Bologna, Italy:274–282Papastergiou G, Psaras I, Tsaoussidis V (2009) Deep-space transport protocol: a novel transport scheme for space DTNs. 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Performance evaluation of AL-FEC LDPC codes for push content applications in wireless unidirectional environments

The final publication is available at Springer via http://dx.doi.org/10.1007/s11042-011-0841-yFEC (Forward Error Correction) mechanisms improve IP content transmission reliability through the recovery of packets lost in transmission. Opposite to ARQ (Automatic Repeat Request), FEC mechanisms are especially suited to unidirectional environments or to multicast environments where multiple receivers perceived different channel losses, thus making difficult the implementation of mechanisms based on feedback information. Among the different types of FEC codes, this paper presents a thorough performance evaluation of LDPC (Low Density Parity Check) codes, based on an implementation developed by the authors, according to the specifications defined by RFC 5170 for the usage of LDPC codes by push content applications based on the FLUTE protocol. LDPC codes provide a good trade-off between performance and complexity, hence, they are appropriate for mobile applications. Contributions of this paper include tests conducted with commercial mobile phones connected to the push content download server over a Wi-Fi network. The evaluation highlights the advantages of using packet level FEC encoding in file transmission over unidirectional networks and provides with a comparison between two kinds of LDPC structures: Staircase and Triangle. This is accomplished by calculating the inefficiency ratio of these LDPC structures in different environments. Results show that the implemented LDPC codes can provide inefficiency ratios close to one when the different coding parameters (as the code rate or the number of blocks) are configured to an optimal value that depends on the packet loss rate. © 2011 Springer Science+Business Media, LLC.This work was supported in part by the Ministry of Industry, Tourism and Trade of the Government of Spain, under project "Redes Hibridas para la Provision de Servicios Turisticos" (TSI-020302-2010-165).De Fez Lava, I.; Fraile Gil, F.; Belda Ortega, R.; Guerri Cebollada, JC. (2012). Performance evaluation of AL-FEC LDPC codes for push content applications in wireless unidirectional environments. 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Optimization of protection techniques based on FEC codes for the transmission of multimedia packetized streams

Esta tesis presenta dos modelos novedosos de arquitecturas basadas en esquemas FEC con el fin de proteger flujos de paquetes con contenido multimedial, para comunicaciones en tiempo real y en canales donde las pérdidas se producen en ráfagas. El objetivo de estos diseños ha sido maximizar la eficiencia de los códigos FEC considerados. Por un lado, el primer modelo busca alcanzar un menor coste computacional para los códigos de Reed- Solomon, ya que su conocida capacidad de recuperación para todo tipo de canales necesita un coste computacional elevado. Por otro lado, en el caso de los códigos LDPC, se ha perseguido aumentar la capacidad de recuperación de estos códigos operando en canales con errores en ráfagas, teniendo en cuenta que los códigos LDPC no están directamente diseñados para este tipo de entorno. El modelo aplicado a los códigos de Reed-Solomon se denomina inter-packet symbol approach. Este esquema consiste en una estructura alternativa que asocia los bits de los símbolos del código en distintos paquetes. Esta característica permite aprovechar de forma mejor la capacidad de recuperación de los códigos de Reed-Solomon frente a pérdidas de paquetes en ráfagas. Las prestaciones de este esquema han sido estudiadas en términos de tiempo de codificación/decodificación versus capacidad de recuperación y han sido comparados con otros esquemas propuestos en literatura. El análisis teórico ha demostrado que el enfoque propuesto permite la utilización de Campos de Galois de menor dimensión con respecto a otras soluciones. Esto se traduce en una disminución del tiempo de codificación/decodificación requerido, mientras que mantiene una capacidad de recuperación comparable. Aunque la utilización de los códigos LDPC está típicamente orientada hacía canales con errores uniformemente distribuidos (canales sin memoria) y para bloques de información largos, esta tesis surgiere el uso de este tipo de códigos FEC a nivel de aplicación, para canales con pérdidas en ráfagas y para entornos de comunicación de tiempo real, es decir, con una latencia de transmisión muy baja. Para satisfacer estas limitaciones, la configuración apropiada de los parámetros de un código LDPC ha sido determinada usando bloques de información pequeños y adaptando el código FEC de modo que sea capaz de recuperar paquetes perdidos en canales con errores en ráfagas. Para ello, primeramente se ha diseñado un algoritmo que realiza una estimación de las capacidades de recuperación del código LDPC para un canal con pérdidas en ráfagas. Una vez caracterizado el código, se ha diseñado un segundo algoritmo que optimiza la estructura del código en términos de capacidad de recuperación para las características especificas del canal con memoria, generado una versión modificada del código LDPC, adaptada al canal con perdidas en ráfagas. Finalmente, los dos esquemas FEC propuestos, han sido evaluado experimentalmente en entornos de simulación usando canales con errores en ráfagas y se han comparado con otras soluciones y esquemas ya existentes. ABSTRACT This thesis presents two enhanced FEC-based schemes to protect real-time packetized multimedia streams in bursty channels. The objective of these novel architectures has been the optimization of existing FEC codes, that is, Reed-Solomon codes and LDPC codes. On the one hand, the optimization is focused on the achievement of a lower computational cost for Reed-Solomon codes, since their well known robust recovery capability against any type of losses needs a high complexity. On the other hand, in the case of LDPC codes, the optimization is addressed to increase the recovery capabilities for a bursty channel, since they are not specifically designed for the scenario considered in this thesis. The scheme based on Reed-Solomon codes is called inter-packet symbol approach, and it consists in an alternative bit structure that allocates each symbol of a Reed- Solomon code in several media packets. This characteristic permits to exploit better the recovery capability of Reed-Solomon codes against bursty packet losses. The performance of this scheme has been studied in terms of encoding/decoding time versus recovery capability, and compared with other proposed schemes in the literature. The theoretical analysis has shown that the proposed approach allows the use of a lower size of the Galois Fields compared to other solutions. This lower size results in a decrease of the required encoding/decoding time while keeping a comparable recovery capability. Although the use of LDPC codes is typically addressed for channels where losses are uniformly distributed (memoryless channels) and for large information blocks, this thesis suggests the use of this type of FEC codes at the application layer, in bursty channels and for real-time scenario, where low transmission latency is requested. To fulfill 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 if a given LDPC code in a burst packet loss network. The second step is the optimization of the code: an algorithm optimizes the code structure in terms of recovery capability against the specific behavior of the channel with memory, generating a burst oriented version of the considered LDPC code. Finally, for both proposed FEC schemes, experimental results have been carried out in a simulated transmission channel to assess the performances of the schemes and compared to several other schemes

Evaluation of background push content download services to mobile devices over DVB networks

© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper proposes a multicast content download service based on the use of residual network capacity to push multimedia content to available local storage in personal multimedia devices. The service under study is based on the FLUTE protocol. Specifically, FLUTE packets fill the spare capacity in the IP tunnels reserved for the primary streaming service (opportunistic insertion). The paper also evaluates the use of AL-FEC parity to overcome transmission errors,object multiplexing to send the most popular multimedia contents more frequently and cache management policies that consider user preferences in order to keep in storage the most useful items. The service has been evaluated through simulations and measurements performed with an application prototype based on the DVB-H standards. The results show that AL-FEC enables the use of residual capacity for background content download services. In turn, AL-FEC, as well as object multiplexing, improves the relation between the number of content items and the overall access time. Moreover, results show that high percentages of requests can be served from the local cache of the service, provided that it is possible to estimate the popularity of content items and the user preferences.This work was supported by the PAID-05-12 program of the UniversitatPolitecnica de Valencia.Fraile Gil, F.; De Fez Lava, I.; Guerri Cebollada, JC. (2014). Evaluation of background push content download services to mobile devices over DVB networks. IEEE Transactions on Broadcasting. 60(1):1-15. https://doi.org/10.1109/TBC.2013.2289639S11560