831 research outputs found
Network coding meets multimedia: a review
While every network node only relays messages in a traditional communication system, the recent network coding (NC) paradigm proposes to implement simple in-network processing with packet combinations in the nodes. NC extends the concept of "encoding" a message beyond source coding (for compression) and channel coding (for protection against errors and losses). It has been shown to increase network throughput compared to traditional networks implementation, to reduce delay and to provide robustness to transmission errors and network dynamics. These features are so appealing for multimedia applications that they have spurred a large research effort towards the development of multimedia-specific NC techniques. This paper reviews the recent work in NC for multimedia applications and focuses on the techniques that fill the gap between NC theory and practical applications. It outlines the benefits of NC and presents the open challenges in this area. The paper initially focuses on multimedia-specific aspects of network coding, in particular delay, in-network error control, and mediaspecific error control. These aspects permit to handle varying network conditions as well as client heterogeneity, which are critical to the design and deployment of multimedia systems. After introducing these general concepts, the paper reviews in detail two applications that lend themselves naturally to NC via the cooperation and broadcast models, namely peer-to-peer multimedia streaming and wireless networkin
Video transport optimization techniques design and evaluation for next generation cellular networks
Video is foreseen to be the dominant type of data traffic in the Internet. This vision is supported by a number of studies which forecast that video traffic will drastically increase in the following years, surpassing Peer-to-Peer traffic in volume already in the current year.
Current infrastructures are not prepared to deal with this traffic increase. The current Internet, and in particular the mobile Internet, was not designed with video requirements in mind and, as a consequence, its architecture is very inefficient for handling this volume of video traffic. When a large part of traffic is associated to multimedia entertainment, most of the mobile infrastructure is used in a very inefficient way to provide such a simple service, thereby saturating the whole cellular network, and leading to perceived quality levels that are not adequate to support widespread end user acceptance.
The main goal of the research activity in this thesis is to evolve the mobile Internet architecture for efficient video traffic support. As video is expected to represent the majority of the traffic, the future architecture should efficiently support the requirements of this data type, and specific enhancements for video should be introduced at all layers of the protocol stack where needed. These enhancements need to cater for improved quality of experience, improved reliability in a mobile world (anywhere, anytime), lower exploitation cost, and increased flexibility.
In this thesis a set of video delivery mechanisms are designed to optimize the video transmission at different layers of the protocol stack and at different levels of the cellular network. Upon the architectural choices, resource allocation schemes are implemented to support a range of video applications, which cover video broadcast/multicast streaming, video on demand, real-time streaming, video progressive download and video upstreaming.
By means of simulation, the benefits of the designed mechanisms in terms of perceived video quality and network resource saving are shown and compared to existing solutions. Furthermore, selected modules are implemented in a real testbed and some experimental results are provided to support the development of such transport mechanisms in practice
Radio resource allocation algorithms for multicast OFDM systems
Mención Internacional en el título de doctorVideo services have become highly demanded in mobile networks leading
to an unprecedented traffic growth. It is expected that traffic from wireless
and mobile devices will account for nearly 70 percent of total IP traffic
by the year 2020, and the video services will account for nearly 75 percent
of mobile data traffic by 2022. Multicast transmission is one of the key
enablers towards a more spectral and energy efficient distribution of multimedia
content in current and envisaged mobile networks. It is worth noting
that multicast is a mechanism that efficiently delivers the same content to
many users, not only focusing on video broadcasting, but also distributing
many other media, such as software updates, weather forecast or breaking
news.
Although multicast services are available in Long Term Evolution (LTE)
and LTE-Advanced (LTE-A) networks, new improvements are needed in
some areas to handle the demands expected in the near future. Resource
allocation techniques for multicast services are one of the main challenging
issues, since it is required the development of novel schemes to meet the
demands of their evolution towards the next generation. Most multicast
techniques adopt rather conservative strategies that select a very robust
modulation and coding scheme (MCS), whose characteristics are determined
by the propagation conditions experienced by the worst user in the group
in order to ensure that all users in a multicast group are able to correctly
decode the received data. Obviously, this robustness comes at the prize of
a low spectral efficiency.
This thesis presents an exhaustive study of broadcast/multicast technology
for current mobile networks, especially focusing on the scheduling
and resource allocation (SRA) strategies to maximize the potential benefits
that multicast transmissions imply on the spectral efficiency. Based on that
issue, some contributions have been made to the state of the art in the radio
resource management (RRM) for current and beyond mobile multicast
services.
• In the frame of LTE/LTE-A, the evolved multimedia broadcast and
multicast service (eMBMS) shares the physical layer resources with the
unicast transmission mode (at least up to Release 12). Consequently,
the time allocation to multicast transmission is limited to a maximum
of a 60 percent, and the remaining subframes (at least 40 percent)
are reserved for unicast transmissions. With the aim of achieving the
maximum aggregated data rate (ADR) among the multicast users, we
have implemented several innovative SRA schemes that combine the
allocation of multicast and unicast resources in the LTE/LTE-A frame,
guaranteeing the prescribed quality of service (QoS) requirements for
every user.
• In the specific context of wideband communication systems, the selection
of the multicast MCS has often relied on the use of wideband
channel quality indicators (CQIs), providing rather imprecise information
regarding the potential capacity of the multicast channel. Only
recently has the per-subband CQI been used to improve the spectral
efficiency of the system without compromising the link robustness.
We have proposed novel subband CQI-based multicast SRA strategies
that, relying on the selection of more spectrally efficient transmission
modes, lead to increased data rates while still being able to fulfill
prescribed QoS metrics.
• Mobile broadcast/multicast video services require effective and low complexity
SRA strategies. We have proposed an SRA strategy based
on multicast subgrouping and the scalable video coding (SVC) technique for multicast video delivery. This scheme focuses on reducing
the search space of solutions and optimizes the ADR. The results in
terms of ADR, spectral efficiency, and fairness among multicast users,
along with the low complexity of the algorithm, show that this new
scheme is adequate for real systems.
These contributions are intended to serve as a reference that motivate
ongoing and future investigation in the challenging field of RRM for broadcast/
multicast services in next generation mobile networks.La demanda de servicios de vídeo en las redes móviles ha sufrido un incremento
exponencial en los últimos años, lo que a su vez ha desembocado
en un aumento sin precedentes del tráfico de datos. Se espera que antes
del año 2020, el trafico debido a dispositivos móviles alcance cerca del 70
por ciento del tráfico IP total, mientras que se prevé que los servicios de
vídeo sean prácticamente el 75 por ciento del tráfico de datos en las redes
móviles hacia el 2022. Las transmisiones multicast son una de las tecnologías
clave para conseguir una distribución más eficiente, tanto espectral como
energéticamente, del contenido multimedia en las redes móviles actuales y
futuras. Merece la pena reseñar que el multicast es un mecanismo de entrega
del mismo contenido a muchos usuarios, que no se enfoca exclusivamente
en la distribución de vídeo, sino que también permite la distribución de
otros muchos contenidos, como actualizaciones software, información meteorológica o noticias de última hora.
A pesar de que los servicios multicast ya se encuentran disponibles en
las redes Long Term Evolution (LTE) y LTE-Advanced (LTE-A), la mejora
en algunos ámbitos resulta necesaria para manejar las demandas que se
prevén a corto plazo. Las técnicas de asignación de recursos para los servicios
multicast suponen uno de los mayores desafíos, ya que es necesario
el desarrollo de nuevos esquemas que nos permitan acometer las exigencias
que supone su evolución hacia la próxima generación. La mayor parte de
las técnicas multicast adoptan estrategias conservadoras, seleccionando esquemas
de modulación y codificación (MCS) impuestos por las condiciones de propagación que experimenta el usuario del grupo con peor canal, para
así asegurar que todos los usuarios pertenecientes al grupo multicast sean
capaces de decodificar correctamente los datos recibidos. Como resulta obvio,
la utilización de esquemas tan robustos conlleva el precio de sufrir una
baja eficiencia espectral.
Esta tesis presenta un exhaustivo estudio de la tecnología broadcast/
multicast para las redes móviles actuales, que se centra especialmente en
las estrategias de asignación de recursos (SRA), cuyo objetivo es maximizar
los beneficios que la utilización de transmisiones multicast potencialmente
implica en términos de eficiencia espectral. A partir de dicho estudio, hemos
realizado varias contribuciones al estado del arte en el ámbito de la gestión
de recursos radio (RRM) para los servicios multicast, aplicables en las redes
móviles actuales y futuras.
• En el marco de LTE/LTE-A, el eMBMS comparte los recursos de la
capa física con las transmisiones unicast (al menos hasta la revisión
12). Por lo tanto, la disponibilidad temporal de las transmisiones
multicast está limitada a un máximo del 60 por ciento, reservándose
las subtramas restantes (al menos el 40 por ciento) para las transmisiones
unicast. Con el objetivo de alcanzar la máxima tasa total de
datos (ADR) entre los usuarios multicast, hemos implementado varios
esquemas innovadores de SRA que combinan la asignación de los recursos
multicast y unicast de la trama LTE/LTE-A, garantizando los
requisitos de QoS a cada usuario.
• En los sistemas de comunicaciones de banda ancha, la selección del
MCS para transmisiones multicast se basa habitualmente en la utilización de CQIs de banda ancha, lo que proporciona información bastante
imprecisa acerca de la capacidad potencial del canal multicast.
Recientemente se ha empezado a utilizar el CQI por subbanda para
mejorar la eficiencia espectral del sistema sin comprometer la robustez
de los enlaces. Hemos propuesto nuevas estrategias para SRA multicast
basadas en el CQI por subbanda que, basándose en la selección de los modos de transmisión con mayor eficiencia espectral, conducen
a mejores tasas de datos, a la vez que permiten cumplir los requisitos
de QoS.
• Los servicios móviles de vídeo broadcast/multicast precisan estrategias
eficientes de SRA con baja complejidad. Hemos propuesto una
estrategia de SRA basada en subgrupos multicast y la técnica de
codificación de vídeo escalable (SVC) para la difusión de vídeo multicast,
la cual se centra en reducir el espacio de búsqueda de soluciones
y optimizar el ADR. Los resultados obtenidos en términos de ADR,
eficiencia espectral y equidad entre los usuarios multicast, junto con la
baja complejidad del algoritmo, ponen de manifiesto que el esquema
propuesto es adecuado para su implantación en sistemas reales.
Estas contribuciones pretenden servir de referencia que motive la investigación actual y futura en el interesante ámbito de RRM para los servicios
broadcast/multicast en las redes móviles de próxima generación.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Atilio Manuel Da Silva Gameiro.- Secretario: Víctor Pedro Gil Jiménez.- Vocal: María de Diego Antó
WIMAX Basics from PHY Layer to Scheduling and Multicasting Approaches
WiMAX (Worldwide Interoperability for Microwave Access) is an emerging broadband wireless technology for providing Last mile solutions for supporting higher bandwidth and multiple service classes with various quality of service requirement. The unique architecture of the WiMAX MAC and PHY layers that uses OFDMA to allocate multiple channels with different modulation schema and multiple time slots for each channel allows better adaptation of heterogeneous user’s requirements. The main architecture in WiMAX uses PMP (Point to Multipoint), Mesh mode or the new MMR (Mobile Multi hop Mode) deployments where scheduling and multicasting have different approaches. In PMP SS (Subscriber Station) connects directly to BS (Base Station) in a single hop route so channel conditions adaptations and supporting QoS for classes of services is the key points in scheduling, admission control or multicasting, while in Mesh networks SS connects to other SS Stations or to the BS in a multi hop routes, the MMR mode extends the PMP mode in which the SS connects to either a relay station (RS) or to Bs. Both MMR and Mesh uses centralized or distributed scheduling with multicasting schemas based on scheduling trees for routing. In this paper a broad study is conducted About WiMAX technology PMP and Mesh deployments from main physical layers features with differentiation of MAC layer features to scheduling and multicasting approaches in both modes of operations
Towards an LTE hybrid unicast broadcast content delivery framework
The era of ubiquitous access to a rich selection of interactive and high quality multimedia has begun; with it,
significant challenges in data demand have been placed on mobile network technologies. Content creators and broadcasters alike have embraced the additional capabilities offered by network delivery; diversifying content offerings and providing viewers with far greater choice. Mobile broadcast services introduced as part of the Long Term Evolution (LTE) standard, that are to be further enhanced with the release of 5G, do aid in spectrally efficient delivery of popular live multimedia to many mobile devices, but, ultimately rely on all users expressing interest in the same single stream. The research presented herein explores the development of a standards aligned, multi-stream aware framework; allowing mobile network operators the efficiency gains of broadcast whilst continuing to offer personalised experiences to subscribers. An open source, system level simulation platform is extended to support broadcast, characterised and validated. This is followed by the implementation of a Hybrid Unicast Broadcast Synchronisation (HUBS) framework able to dynamically vary broadcast resource allocation. The HUBS framework is then
further expanded to make use of scalable video content
Towards video streaming in IoT environments: vehicular communication perspective
Multimedia oriented Internet of Things (IoT) enables pervasive and real-time communication of video, audio and image data among devices in an immediate surroundings. Today's vehicles have the capability of supporting real time multimedia acquisition. Vehicles with high illuminating infrared cameras and customized sensors can communicate with other on-road devices using dedicated short-range communication (DSRC) and 5G enabled communication technologies. Real time incidence of both urban and highway vehicular traffic environment can be captured and transmitted using vehicle-to-vehicle and vehicle-to-infrastructure communication modes. Video streaming in vehicular IoT (VSV-IoT) environments is in growing stage with several challenges that need to be addressed ranging from limited resources in IoT devices, intermittent connection in vehicular networks, heterogeneous devices, dynamism and scalability in video encoding, bandwidth underutilization in video delivery, and attaining application-precise quality of service in video streaming. In this context, this paper presents a comprehensive review on video streaming in IoT environments focusing on vehicular communication perspective. Specifically, significance of video streaming in vehicular IoT environments is highlighted focusing on integration of vehicular communication with 5G enabled IoT technologies, and smart city oriented application areas for VSV-IoT. A taxonomy is presented for the classification of related literature on video streaming in vehicular network environments. Following the taxonomy, critical review of literature is performed focusing on major functional model, strengths and weaknesses. Metrics for video streaming in vehicular IoT environments are derived and comparatively analyzed in terms of their usage and evaluation capabilities. Open research challenges in VSV-IoT are identified as future directions of research in the area. The survey would benefit both IoT and vehicle industry practitioners and researchers, in terms of augmenting understanding of vehicular video streaming and its IoT related trends and issues
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