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

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

Low latency LDGM code for multimedia-packet stream in bursty packet loss networks

In this paper we present a FEC scheme based on simple LDGM codes to protect packetized multimedia streams. We demonstrate that simple LDGM codes working with a limited number of packets (small values of k) obtain recovery capabilities, against bursty packet losses, that are similar to those of other more complex FEC-based schemes designed for this type of channels

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

Mix & Latch: An Optimization Flow for High-Performance Designs with Single-Clock Mixed-Polarity Latches and Flip-Flops

Flip-flops are the most used sequential elements in synchronous circuits, but designs based on latches can operate at higher frequencies and occupy less area. Techniques to increase the maximum operating frequency of flip-flop based designs, such as time-borrowing, rely on tight hold constraints that are difficult to satisfy using traditional back-end optimization techniques. We propose Mix & Latch , a methodology to increase the operating frequency of synchronous digital circuits using a single clock tree and a mixed distribution of positive- and negative-edge-triggered flops, and positive- and negative-level-sensitive latches. An efficient mathematical model is proposed to optimize the type and location of the sequential elements of the circuit. We ensure that the initial registers are not moved from their initial location, although they may change type, thus allowing the use of equivalence checking and static timing analysis to verify formally the correctness of the transformation. The technique is validated using a 28nm CMOS FDSOI technology, obtaining 1.33X post-layout average operating frequency improvement on a broad set of benchmarks over a standard commercial design flow. Additionally, the circuit area was also reduced by more than 1.19X on average for the same benchmarks, although the overall area reduction is not a goal of the optimization algorithm. To the best of our knowledge, this is the first work that proposes combining mixed-polarity flip-flops and latches to improve the circuit performance

Hand arm vibration generated by a rotary pick-up for table olives harvesting

The manual harvest of olives is one of the most expensive operations in the table olives production, but the use of the electric hand-guided machines triples the productivity.  The development of these new machines leads to changes in the harvesting methodologies and in the operator’s working behavior.  These items may also affect the hand-arm vibration (HAV) transmitted to the operators during the work.  Aim of this study is to evaluate the hand-arm vibration transmitted to the operator using an experimental electric labor saving machine with rotary combs with teeth of different dimensions covered by silicon to minimize the damage to the drupes.  Moreover, the olives removal forces have been analyzed to understand if the force necessary to detach the drupes is correlated to the vibration levels transmitted to the operator’s hand arm.  With this type of hand held olive harvester, it has been found that higher is the fruit removal force, higher are the measured vibration levels.   Keywords: HAV, portable olive shakers, rotary pick-up, table olive

Antiherpevirus activity of Artemisia arborescens essential oil and inhibition of lateral diffusion in Vero cells

<p>Abstract</p> <p>Background</p> <p>New prophylactic and therapeutic tools are needed for the treatment of herpes simplex virus infections. Several essential oils have shown to possess antiviral activity <it>in vitro </it>against a wide spectrum of viruses.</p> <p>Aim</p> <p>The present study was assess to investigate the activities of the essential oil obtained from leaves of <it>Artemisia arborescens </it>against HSV-1 and HSV-2</p> <p>Methods</p> <p>The cytotoxicity in Vero cells was evaluated by the MTT reduction method. The IC₅₀values were determined by plaque reduction assay. In order to characterize the mechanism of action, yield reduction assay, inhibition of plaque development assay, attachment assay, penetration assay and post-attachment virus neutralization assay were also performed.</p> <p>Results</p> <p>The IC₅₀values, determined by plaque reduction assay, were 2.4 and 4.1 μg/ml for HSV-1 and HSV-2, respectively, while the cytotoxicity assay against Vero cells, as determined by the MTT reduction method, showed a CC₅₀value of 132 μg/ml, indicating a CC₅₀/IC₅₀ratio of 55 for HSV-1 and 32.2 for HSV-2. The antiviral activity of <it>A. arborescens </it>essential oil is principally due to direct virucidal effects. A poor activity determined by yield reduction assay was observed against HSV-1 at higher concentrations when added to cultures of infected cells. No inhibition was observed by attachment assay, penetration assay and post-attachment virus neutralization assay. Furthermore, inhibition of plaque development assay showed that <it>A. arborescens </it>essential oil inhibits the lateral diffusion of both HSV-1 and HSV-2.</p> <p>Conclusion</p> <p>This study demonstrates the antiviral activity of the essential oil <it>in toto </it>obtained from <it>A. arborescens </it>against HSV-1 and HSV-2. The mode of action of the essential oil as antiherpesvirus agent seems to be particularly interesting in consideration of its ability to inactivate the virus and to inhibit the cell-to-cell virus diffusion.</p

A Qualitative Exploration of the Use of Contraband Cell Phones in Secured Facilities

Offenders accepting contraband cell phones in secured facilities violate state corrections law, and the possession of these cell phones is a form of risk taking behavior. When offenders continue this risky behavior, it affects their decision making in other domains where they are challenging authorities; and may impact the length of their incarceration. This qualitative phenomenological study examined the lived experience of ex-offenders who had contraband cell phones in secured correctional facilities in order to better understand their reasons for taking risks with contraband cell phones. The theoretical foundation for this study was Trimpop\u27s risk-homeostasis and risk-motivation theories that suggest an individual\u27s behaviors adapt to negotiate between perceived risk and desired risk in order to achieve satisfaction. The research question explored beliefs and perceptions of ex-offenders who chose to accept the risk of using contraband cell phones during their time in secured facilities. Data were collected anonymously through recorded telephone interviews with 8 male adult ex-offenders and analyzed using thematic content analysis. Findings indicated participants felt empowered by possession of cell phones in prison, and it was an acceptable risk to stay connected to family out of concern for loved ones. The study contributes to social change by providing those justice system administrators, and prison managers responsible for prison cell phone policies with more detailed information about the motivations and perspectives of offenders in respect to using contraband cell phones while imprisoned in secured facilities

Cytotoxic diacetylenic spiroketal enol ethers from Plagius flosculosus

Three new diacetylenic spiroketal enol ethers named flosculins A (1), B (2), and C (3), along with five known compounds (4-8) of the same structural class, were isolated from the leaves of Plagius flosculosus. The structures were deduced by extensive 1D and 2D NMR spectroscopy and mass spectrometry. All isolated compounds exhibited significant cytotoxic activity against leukemia cells (Jurkat T and HL-60). Compounds 5-8 induced apoptosis in HL-60 cells with corresponding IC(50) values ranging from 4 to 6 microM

Phenolic constituents from Ephedra nebrodensis

Two new phenolic glycosides, 4-hydroxy-3-(3-methyl-2-butenyl)phenyl -D-glucopyranoside (nebrodenside A)and O-coumaric acid -D-allopyranoside (nebrodenside B), were isolated from the aerial parts of Ephedra nebrodensis. In addition, O-coumaric acid glucoside, ()-epicatechin, and ()-ephedrine were also isolated. The structures were deduced from extensive 1D and 2DNMR spectroscopy (1H, 13C, DQF-COSY, TOCSY, GHSQC, GHMQC, ROESY) as well as mass spectrometry (EI and HR-MALDI). ()-Epicatechin showed weak antiviral activity against Influenza A virus and very weak cytotoxicity against MDCK cells