Jesus Alcober

Supporting Scalable Video Transmission in MANETs through Distributed Admission Control Mechanisms

Emerging multimedia applications over mobile devices are becoming very popular, especially over infrastructure wireless networks such as cellular and WLANs. However, providing this kind of services over infrastructure-less networks like ad hoc networks presents many additional problems. One of these problems is how to share resources fairly among the users involved. In this article we propose a QoS framework supporting scalable video streaming in mobile ad hoc networks based on distributed admission control and video traffic awareness. Our framework promotes fairness between video flows in terms of resource consumption. It also guarantees a significant reduction of the idle times experienced by users during periods of network saturation, thus increasing the video playout time in reception for all users. Using the IEEE 802.11e MAC technology as our basis for traffic differentiation, our framework, called DACME-SV (Distributed Admission Control for MANETs - Scalable Video), relies on a periodic probing process to measure the available bandwidth and the end-to-end delay on the path. DACME-SV adopts a cross-layer approach to determine the optimum number of video layers to transmit at any given time, thus avoiding network congestion and guaranteeing an acceptable video quality at the destination. Experimental results show that idle time periods are substantially decreased, while exhibiting a good overall performance in terms of throughput and delay.

Context-aware multimedia service composition using quality assessment

With the proliferation of multimedia capable devices, media services have to deal with heterogeneous environments where very different types of terminals wish to receive content anywhere and anytime. This situation motivates the appearance of multimedia services that adapt contents to the specific context of users. However, current Internet architecture is based on a rigid layered model, which makes difficult to introduce new functionalities efficiently. To solve this, Service Oriented Architectures (SOA) appear with the goal of proposing new architectures based on services that can be invoked when and where necessary. This work introduces how SOA paradigm can be applied to context-aware multimedia communications. In addition, a scoring function for selecting different service implementations is presented and particularized for a case of selecting transcoding functions taking into account different quality assessment metrics.

Design and implementation of a measurement and alert system of QoS parameters in SIP based Internet telephony

This paper proposes a measurement system of QoS parameters for a SIP based Internet telephony service. This system is called QoS agent and will allow telephony user to receive alerts in real time if network conditions are not suitable to make a call. Two complementary types of measurement methods will be used. The first one is called incall method which uses RTCP packets statistics obtained during the first seconds of a call in progress. The second one is called outcall method. It periodically uses the SIP OPTIONS method to obtain delay statistics out of a call. This system constitutes an alternative solution of QoS management for IP telephony service providers that use third partys infrastructure to provide the service

Assessing the best strategy to improve the stability of scalable video transmission in MANETs

Mobile Ad Hoc Networks (MANETs) have been an important research topic for the last years, playing a crucial role within the fast growing sector of mobile communications. At the same time, video applications over mobile devices are becoming widely used by nowadays mobile clients, where the quality in the transmission of such contents will determine the success of these applications in the future. Therefore, it is mandatory to find the best strategies to guarantee a good Quality of Service (QoS) to the end-user. In this work we present a set of novel strategies to improve the performance of video transmission over MANETs. These new strategies are based on distributed admission control protocols which has proved to be helpful at achieving an efficient video transmission system. Experimental results show that, when adopting the new strategies to determine the optimal number of layers to transmit, we can achieve better results compared to other existent approaches in terms of idle time periods, fairness and delay.

Fuzzy redundancy adaptation and joint source-network coding for VANET video streaming

Video communication VANETs has many applications, such as emergency video transmission or inter-vehicle entertainment. However, delivering video to high mobile vehicles faces challenges such as packet loss due to intermittent connectivity and channel variations. Thus, designing a reliable approach for video streaming over such harsh scenarios is needed. Hence, we propose a reliable approach based on random practical network coding and source coding. This approach integrates the benefits of network coding with Multiple Description Coding to achieve robust streaming over VANET. Furthermore, we propose a redundancy controller based on fuzzy inference system to adjust the amount of redundant packets based on vehicular traffic density and SNR of the channel. Simulation shows the proposed approach achieves better protection against packet loss, application layer throughput and video quality.

Costing framework for service-oriented future internet architectures: empowering requester's choice

Internet is evolving fast thanks to the rising of new services and applications. This situation allowed realizing about current Internet deficiencies. Nowadays, researchers are proposing novel Internet architectures avoiding the rigidity of the layered structure posed by the TCP/IP stack. Service Oriented Architectures (SOA) principles are appropriate for proposing a flexible and scalable Internet architecture, which relies on the combination of services according to the requester needs. In this context it is necessary to introduce a framework for cost and price that enables requesters and providers to interact and create new business models for the Future Internet (FI). This work proposes a novel costing framework for providing services adapted to requester requirements.

Analysis of control and multimedia real-time traffic over SIP and RTP on 802.11n wireless links for utilities networks

Urban facility interconnection networks require a robustness and reliability usually found in public networks or private cable and radio networks in licensed bands. Both factors mean an increase in costs, which also increase as the size of the network increases. The recent rise in use of wireless technologies in open wavebands has attracted the interest of the industry in the spread of these types of links, even though they have a lower level of robustness and reliability, which must be improved using communication mechanisms and protocols. This aspect directly affects real time applications, such as VoIP and video-streaming, and determines the viability of these systems in real installations. This paper evaluates the performance of control and real time multimedia traffic in the 5 GHz band through the use of the SIP (Session Initiation Protocol) and RTP (Real-Time Transport Protocol) protocols, in a laboratory testbed.

The SIP-CMI platform-an open testbed for advanced integrated continuous media services

We introduce the design an implementation of the SIP-based continuous media integration (SIP-CMI) platform, an open, flexible, scalable testbed to support a wide and extensible set of next-generation continuous media services. SIP-CMI employs a modular architecture and is built using commodity hardware. This platform follows the principle that any continuous media service can be accessed by using the SIP protocol, regardless of the nature of the service; i.e., videoconference or streaming,. Furthermore, we explain how different ongoing projects are using this testbed to prototype and validate its advanced services

Letter Throughput and Delay Analysis of the Ideal Window

We consider the problem of random access communications over a time slotted channel with feedback of infinitely multiplicity at the beginning of each collision resolution interval (CRI), i.e., users know via instantaneous feedback the number of users involved in that collision. Once this is known, the resolution algorithm (CRA) operates with binary (successful / non successful, s /ns) feedback. The analysis of this simple hll feedback sensing window random access algorithm, named ideal window stabilized ALOHA, (IWSA). algorithm, provides a throughput of 0.5053 packetslslot. Its delay is also analyzed and compared with similar algorithms.

Evaluating MDC with incentives in P2PTV systems

The popularity of P2P video streaming is raising the interest of broadcasters, operators and service providers. Concretely, mesh-pull based P2P systems are the most extended ones. Despite these systems address scalability efficiently, they still present limitations that difficult them to offer the same user experience in comparison with traditional TV. These ones are mainly the free-riding effect, long start-up delays and the impact of churn and bandwidth heterogeneity. In this paper we study the performance of Multiple Description Coding (MDC) combined with the use of incentives for redistribution in order to mitigate some of them by means of simulations. Simulation results show that the use of MDC and incentive-based scheduling strategies improve the overall performance of the system. Moreover, an extended version of the P2PTVSim simulator has been developed to support MDC and incentives.