Ana Pajares

JMFMoD: a new system for media on demand presentations

This article describes the main challenges of implementing a Java media on demand (MoD) system. The objective of this system is to offer a complete solution for creating multimedia presentations (audio, video, text, slides) and their synchronized reproduction on the client side. This system consists of the following elements: an authoring presentation tool, a standalone MoD server application, a Web integrated MoD client, a database containing all the available media presentations, and a proprietary protocol that provides all the functionality of a VCR stream control mechanism. The Java Media Framework library (JMF) and the RTP protocol for audio and video transmission were used as development tools.

A mobile device application applied to low back disorders

Many muscular function assessments require the monitoring of muscular activity in different environments. This can happen in the gymnasium during a training session or while practising a sport; at work, where movements and specific actions are executed; at school, where the child adopts an incorrect posture, or even while we walk. In this paper, we propose a system to allow the assessment of the muscular condition in any of these environments in a comfortable and simple way for the patient and using the advances in wireless communications. Just a wireless biomonitor (we have used the ME6000 biomonitor, a medical portable equipment of very small dimensions) and one PDA or mobile phone with wireless interface are needed. The medical device is configured from the mobile device. Then, wireless communications are used to transmit online the electromyographic signals registered by the medical equipment to a mobile device. The specific protocol used by the medical device is implemented to carry out the communication. There are two ways to configure the system: offline and online. In offline mode, once all the information is received, it is sent to a server using a connection to the Internet instead of the online way, where this information is sent simultaneously. The server includes a background application to process the information in real-time with the aim to evaluate the function of the muscle during the exercise and to establish healthy behaviours for the patient. Then, this information can be consulted by the specialist and also by the client using the PDA or mobile phone to show the report. A prototype of this system has been developed and implemented. The system has been evaluated by a preliminary usability, reliability, feasibility and communication performance study.

A real-time e-learning system via satellite based on JMF and Windows Media

In this paper we present the design and development of a real-time e-learning system at the Polytechnic University of Valencia. The main novelty of this multimedia virtual classroom is the integration of Windows Media, Java Media Framework (JMF) and MPEG4 in a web-based environment. The communication network used in this real-time e-learning system is a satellite network for the multicasting of high-quality video from the teachers to the students using RTP, together with Internet/ISDN as return channel from the remote classrooms for low-quality video questions transmission. The system is fully operational and in the following year will be used as support for an e-learning co-operation project between Spain and South-America by a satellite communications operator.

A feedback packet-level error control for real-time applications in wireless networks

Current wireless networks have been designed to carry voice and data at a low transmission rate. However, GSM 2++ and 3rd. generation wireless systems will be able to also carry multimedia traffic at a high data transmission rate. These new wireless systems should be able to support different kinds of traffic (voice, data, video), each of them with different requirements regarding to latency, data rate or error rate. But like in fixed networks, new mechanisms should be added so that the applications may adapt their behavior to current network conditions and maintain a certain quality of service (QoS). By making use of the RTP/RTCP protocols, the approach presented in this paper is able to adjust the transmission rate according to the packet loss rate perceived at the receiver.

Dynamic frequency and resource allocation with adaptive error control based on RTP for multimedia QoS guarantees in wireless networks

Providing QoS guarantees in wireless networks is a much more complex problem than in fixed networks. Conventional fixed allocation schemes are not suitable for these traffic patterns and it becomes necessary to design new dynamic resource allocation schemes. This paper deals with three of the main wireless network problems to provide multimedia QoS guarantees, i.e., frequency assignation, bandwidth requirements and error rate. For the former problem, several frequency assignment algorithms have been evaluated. For the second, a dynamic resource allocation algorithm is proposed. The goal of this algorithm is to share the available wireless bandwidth between the major number of connections, and offer the maximum QoS to all of them depending on the connection state. For the latter, error rate effects are corrected by means of an adaptive error control algorithm based on RTP. This algorithm tries to balance the channel quality of the on-going calls to obtain a fair error quality for all of them.

Policy-based quality of service mapping in distributed systems

An effective management is a necessary prerequisite for the economical operation of a telecommunications network or service. In particular, the quality of an offered service is an important task of the management. We refer to quality of service (QoS) as the ability to deliver services according to a set of contractual agreed parameters. All involved networks, end-systems, and to a large extent, the applications, influence end-to-end QoS. Thus, we have two quite different views on QoS: the application point of view and the network point of view. Both have to be integrated in a combined management process to enable the delivery of a guaranteed end-to-end QoS. The integrated management together with its requirements we will call the management view. In our QoS mapping process we identify four types of QoS specifications: (1) subjective end-user requirements; (2) the applications QoS view including QoS profiles and application QoS parameters; (3) objective QoS parameters, and (4) network QoS parameters used for signalling QoS through the network.

Adaptive Error Resilience Tools for Improving the Quality of MPEG-4 Video Streams over Wireless Channels

The transmission of encoded video streams over heterogeneous networks, characterized by congestion losses in wired links and high bit error rate in the wireless channel, is under consideration in this paper. First of all, it is necessary to make a distinction between the different kinds of losses to achieve a high channel utilization. Then, when dealing with wireless losses, the robustness of the encoded stream has to be improved. This article shows an easy way of implementing a global adaptive algorithm for wireless networks. It proposes a new algorithm to adequate the parameters of video error resilience tools to the changing characteristics of the wireless channel. The aim of this algorithm is guaranteeing the quality of the video. Simplicity is the key, as the receiver of the video stream will be a handheld device (i.e. PDA, mobile phone, etc.) with limited processing capacity

Hand-off and synchronization protocols for supporting multimedia communications in an ATM based wireless network

New multimedia service provision, that requires high transfer speeds, and end-to-end network guaranteed delays, is an under-research field in mobile communications. These services are currently supported by ATM networks, that are, in fact the basis of the fixed network in whole mobile communication systems. However, new generations of digital wireless communication systems, based on TDMA, have bandwidth and signalling limitations in supporting these services. An important problem in this scenario is the synchronisation of multimedia flows when a hand-off is performed, and bandwidth management. We propose, for a typical ATM fixed network/TDMA wireless system architecture, some improvements in the synchronisation and bandwidth management process of multimedia flows after a hand-off procedure.

Social Aware TV Content Delivery Over Intelligent Networks

As explained throughout the book, the analysis of social media has a great potential in improving the Quality of Experience (QoE) of media services. In this context, video delivery over IP networks is one of the processes that could benefit from the analysis of the social aspects associated to broadband video services. This chapter presents network intelligence as a technology enabler to integrate social media analysis in the management of video content delivery in IP networks. More precisely, this chapter presents dynamic reservations to manage network resources in an intelligent way, anticipated reservations to guarantee network resources during a time interval and content caching to maximize the usage of bandwidth across the network. All these techniques allow network operators to benefit from social media, improving the QoE of users considerably.