Elsa M. Macías

Elsa M. Macías
Universidad de Las Palmas de Gran Canaria | ULPGC · Telematics Engineering

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86
Publications
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Introduction

Publications

Publications (86)
Article
Full-text available
Wireless sensor networks proliferate more and more in all social scopes and sectors. Such networks are implemented in smart homes, smart cities, security systems, medical resources, agriculture, automotive industry, etc. Communication devices and sensors of such networks are powered with batteries: the enlarging of battery life is a hot research to...
Article
Full-text available
Wireless fidelity (WiFi) networks are deployed in several varied environments all around the World. Usually, the wireless fidelity access points are always on in houses and other small companies. In buildings of large companies and public organizations and in university campuses the number of access points is elevated; they are powered using power...
Article
Full-text available
Currently environment protection is a big challenge. One way of protection is focusing on power saving of electrical devices. Although computers and networks are not the main air polluting sources, they are contributing in a considerable way. Multiple proposals to reduce the power consumption have been presented due to the massive usage of the netw...
Article
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Daily human actions cause positive or negative side effects on Environment. A city is a kind of Environment that supports a big amount of people daily causing side effects on it. Urban wastes and car driving are typical actions that pollute the city. Smart city treats to reinvent cities making them a good living environment. Wireless Sensor Network...
Article
Full-text available
Low-cost video surveillance systems are attractive for Smart Home applications (especially in emerging economies). Those systems use the flexibility of the Internet of Things to operate the video camera only when an intrusion is detected. We are the only ones that focus on the design of protocols based on intelligent agents to communicate the video...
Article
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RSSI is a reference magnitude of radio signal strength received by a wireless terminal. Traditionally, it has been used to implement wireless services like scanning in handoff. But its high long term variability (volatility) makes its high precision estimation be impossible, complicating its applicability. Moreover, every wireless terminal has its...
Conference Paper
Actualmente los sistemas de videovigilancia en el Hogar se pueden combinar con sensores para formar un sistema de muy bajo coste y fácil manejo por parte del usuario final. Un componente importante en este sistema es el servidor de video streaming en tiempo real a clientes Web que usan Wireless Fidelity. El servidor se puede instalar en open hardwa...
Article
Full-text available
Ubiquitous sensing allows smart cities to take control of many parameters (e.g., road traffic, air or noise pollution levels, etc.). An inexpensive Wireless Mesh Network can be used as an efficient way to transport sensed data. When that mesh is autonomously powered (e.g., solar powered), it constitutes an ideal portable network system which can be...
Article
Full-text available
Received Signal Strength Indicator is an indication of power level being received by a wireless device. This parameter for Wireless Fidelity has never been standardized, so any manufacturer implements it measuring as he knows better doing. This is a problem because different scenarios can be found based in several elements like: the particular Wire...
Article
Full-text available
Wireless sensor networks (WSNs) are currently widely used in many environments. Some of them gather many critical data, which should be protected from intruders. Generally, when an intruder is detected in the WSN, its connection is immediately stopped. But this way does not let the network administrator gather information about the attacker and/or...
Article
Clustering is a well known methodology to optimize the use of the resources, to lower the congestion and to improve the reliability in self-organized networks as the wireless sensor networks. This paper deals with the proposal of a novel clustering approach based on a low complexity distributed cluster head election based on a two-stage process. I...
Article
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Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-cen...
Chapter
Improved 4G communication technologies in conjunction to Web 2.0 technologies are contributing to design and implement new and exciting healthcare services for citizens that can be accessed any time and any place. Tobacco is a risk factor causing increased morbidity and mortality in developed countries. Smoking cessation is a hard challenge for...
Article
Full-text available
Current mobile phones come with several sensors and powerful video cameras. These video cameras can be used to capture good quality scenes, which can be complemented with the information gathered by the sensors also embedded in the phones. For example, the surroundings of a beach recorded by the camera of the mobile phone, jointly with the temperat...
Article
Full-text available
The number of appliances at home is increasing continuously, mainly because they make our lives easier. Currently, technology is integrated in all objects of our daily life. TCP/IP let us monitor our home in real time and check ubiquitously if something is happening at home. Bearing in mind this idea, we have developed a low-cost system, which can...
Chapter
A basic WiFi access network provides a poor connectivity and does not support acceptable Quality of Service. The standard IEEE 802.11e includes some Medium Access Control improvements. IEEE 802.11n includes some improvements alone and in combination with Wireless Media Extensions but they are not available in the most current mobile devices and do...
Chapter
Most of today’s smart-phones are geared towards a single user experience, whether it is reading a book, watching a movie, playing a game or listening to music. However, there has been a shift towards providing a more complex and social experience: applications are being developed and deployed to help users connect and share information with each ot...
Chapter
Nowadays an intensive diversification can be experienced among the devices that can display multimedia content to the user. Typically, clients are unable to receive large audio-visual data volumes in original quality because of resource limitations and deficiency of terminal capabilities. The aim of media resource adaptation is to provide multimedi...
Chapter
In recent years, mobile phones have become the de facto system of communication across the planet. Mobile phones have helped increase economic growth and critical response in many parts of the world. Mobile phones are even being used for data transmission. However, little academic research has been done on the specific problem of streaming real tim...
Chapter
Applications and infrastructures of the future will have to be intelligent to some extent, which means that they should automatically adapt to the current situation and intention of the user. This regards basic interoperability issues in heterogeneous environments as well as advanced behavior of software. Two technological trends contribute to solv...
Chapter
The multimedia content is migrating promptly from standard quality to high-definition and even 3D. As a result, existing wireless technologies can no longer support multimedia streaming as their wired counterparts. To overcome this problem, new wireless technologies that support multi Gbps wireless transmission are desperately needed. In this chapt...
Chapter
Due to the time-varying nature of wireless channels and the Internet backbone traffic, it is a challenging task to maintain the quality of wireless multimedia streaming throughout the transmission. An effective solution is to adapt the codec setting based on the wireless channel condition or the Internet backbone state. In this chapter, we present...
Chapter
Video streaming technique is at present the key factor of some multimedia services. The efficient implementation of multimedia services in mobile telephones is currently a major challenge. Today, the deployment of multi-platform multimedia software in high-end mobile telephones is also a challenge. In this chapter, we will review current and upcomi...
Chapter
Traditionally, Internet has offered multimedia services independently of the services offered by companies associated to Telco (companies that traditionally offer telephony and associated services). In the last years, the technical community has assumed that the convergence of both worlds is a fact; however, there are many barriers to be removed. O...
Chapter
Recent improvements in technology have opened new, intriguing, and challenging scenarios for the latest generation of mobile devices, and users are asking for an ever larger spectrum of applications. In particular, implementation of interactive applications is an exciting task. In spite of the continuous improvements in the hardware components of m...
Chapter
The media streaming server technology have been developed in the recent past using free software and open source approaches. But commercial approaches are preferred by certain multimedia big enterprises. These enterprises dominate the mobile media delivery business. For this reason we think it is interesting to discover the main characteristics of...
Chapter
It is expected that multimedia applications will be the most abundant application in the Internet and thousands of new wireless and mobile users will produce and share multimedia streaming content ubiquitously. In this multimedia-aware system, it is important to assure the end-to-end quality level support for video and voice applications in wireles...
Chapter
Mobile WiMAX is suitable for video-on-demand as well as broadcast TV services. Delivery of video streams over an IP packet-switched network, which includes broadband wireless access, requires rate or congestion control along with methods to protect the compressed stream from the impact of channel conditions. The Chapter considers possible solutions...
Article
Full-text available
The interest in monitoring applications using underwater sensor networks has been growing in recent years. The severe communication restrictions imposed by underwater channels make that efficient monitoring be a challenging task. Though a lot of research has been conducted on underwater sensor networks, there are only few concrete applications to a...
Conference Paper
The rapid evolution of wireless communications has contributed to successful of the mobile Video Streaming service today. However, the streaming technique is necessary for receiving video efficiently because the mobiles still have limited resources. The unpredictable behavior of wireless channels can produce service disruptions, and rejection of t...
Article
Full-text available
The evolution of mobile telephones have produced smart devices that not only allows the mobile user to talk but also to use a lot of telematic services. High quality photos and videos are produced by smart mobile telephones. The Global Positioning System available in the Mobile telephones allows the user to tag their photos and videos. There are se...
Article
Full-text available
Wireless networks, and in particular Wireless Fidelity (WiFi) networks, present important problems of connectivity among wireless terminals. These problems lead to inefficiencies in the Application level. For localization algorithms in wireless networks, efficient handover protocols and multimedia delivery information, these problems must be solved...
Article
Full-text available
The quality of service (QoS) in a Wireless Fidelity (WiFi) network can not be guaranteed due to intermittent disconnections, interferences and so forth because they reduce considerably the necessary QoS for multimedia applications. For that reason it is essential a software as the one we present in this paper that evaluates if there are the appropr...
Article
Full-text available
Streaming is a technique used to transmit information over the network so that its issuing from the server, its communication along the network and its downloading and processing on the client overlapp, and moreover it must not be saved in the client memory. This technique is very effective for transmitting multimedia information (video) and is ver...
Article
A combination of wireless and wired network can be used to improve the execution time of non-scientific applications at a very reduced cost. In previous works we have presented middleware extensions to efficiently adapt the execution of MPI programs to wireless networks. In this paper we present an improvement of our previous middleware to control...
Conference Paper
Full-text available
Physical properties of wireless channels make very difficult or sometimes impossible to maintain open client sessions for interactive multimedia services. Short term client sporadic and not previsible disconnections lead to service interruptions which provoke a user headache especially if a firm real time multimedia service is used and a hard error...
Article
Full-text available
Two important high bandwidth wireless certifications in our days are Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Fidelity (WiFi). They can interoperate to form a wide geographical network in which Mobile Client (MC) can move. We suppose a combination of two WiFi Access Points (AP) and a WiMAX Base Station (BS) that interope...
Conference Paper
Fifteen papers were submitted to Topic 8. Each paper was reviewed by four of the topic chairs (a single paper received only three reviews). Three papers were ranked clearly above the others and three others were discussed in more depth between the chairs. As a result, the chairs proposed three papers for acceptance, and two more for discussion, one...
Article
Full-text available
In a Wireless Fidelity (WiFi) network it is well known that large periods of contention, the intermittent disruptions of the service and limited bandwidth represent a handicap for interactive realtime multimedia applications since they demand high troughput and real time constraints, e.g. Video on Demand (VoD) or Voice over Internet Protocol (VoIP)...
Article
Full-text available
Mobile ad hoc networks are prone by nature to path breaks and reconnections. Routing protocols such as OLSR that provide topology information with a mini-mum delay to the quick reconfiguration of path breaks are desired. Applications and protocols should be able to adapt to the dynamics of these networks. However, this is not true for most applicat...
Chapter
Full-text available
—Efficient video streaming in a mobile ad hoc network (MANET) is a challenging problem due to the dynamic nature of the network that leads to high bit error rates, unpredictable delay, jitter, throughput and packet delivery ratios and frequent short, intermittent and long-term link failures. Despite the MANET research community’s efforts, there are...
Conference Paper
Full-text available
Two important high bandwidth wireless certifications in our days are Worldwide Interoperability for Microwave Access (WiMax) and Wireless Fidelity (WiFi). They can interoperate to form a geographical wider network in wchich Mobile Client (MC) can move. We suppose a combination of two WiFi Access Points (AP) and a WiMax Base Station (BS) that intero...
Article
Full-text available
Media streaming technology consists of simultaneously downloading and reproducing multimedia objects from the Internet without the need to store all the information in the client's memory. This technology is very appropriate for client applications running on portable computing devices (cell phones and hand-held devices) due to their limited memory...
Conference Paper
Due to the great development in computer technologies and the popularity of WLANs, new services related to mobile computing can be developed. In this sense, location-based computing can be used by applications running in portable devices for taking better decisions and improving their performance. As the received signal strength (RSS) from several...
Conference Paper
Media streaming technology consists of simultaneously downloading and reproducing multimedia objects from the Internet without the need to store all the information in the client's memory. This technology is very appropriate for client applications running on portable computing devices (cell phones and hand-held devices) due to their limited memory...
Conference Paper
A network formed by desktop and portable computers is a useful environment for doing parallel computing. In this infrastructure we implement Master/Slave parallel distributed programs which exhibit strict data dependencies among iterations and parallel calculations inside an iteration. In a previous work, we developed a load balancing strategy that...
Conference Paper
At present the multimedia services are growing up over wireless networks. But the design of these services is a hard task due to the inherent restrictions and problems of these networks (as well as the restrictive computing power of wireless terminal devices). Object Oriented Programming paradigm fails when it is used to program these kind of servi...
Conference Paper
A combination of a local area network (LAN) and a wireless LAN (WLAN) is a useful environment for doing parallel computing. We use this infrastructure to implement master/slave parallel distributed programs which exhibit strict data dependences among iterations and parallel calculation inside an iteration. In this environment it is necessary to con...
Conference Paper
In the last few years the use of wireless technology has increased by leaps and bounds and as a result powerful portable computers with wireless cards are viable nodes in parallel distributed computing. In this scenario it is natural to consider the possibility of frequent failures in the wireless channel. In MPI programs, such wireless network beh...
Article
Deployment of wireless LANs includes two main design issues: selection of access point locations and access point frequency assignments. Properly solving these issues normally involves a trial and error process, and can be very time consuming. The Rollabout ...
Conference Paper
Many emerging situations and applications demand the reconciliation of the MPI model, which implicitly assumes well-connected-ness and unform network capabilities, with wireless and mobile networks that are subject to variations and intermittent connectivity. We describe middleware extensions that assist applications operating in such environments...
Conference Paper
Parallel and distributed computing over heterogeneous networks is a hot topic nowadays. We have used a combination of a Local Area Network (LAN) and a Wireless LAN (WLAN) to implement Master-Slave parallel distributed programs which exhibit dependences among iterations and parallel calculation inside an iteration. In this environment it is necessar...
Conference Paper
Full-text available
We propose a novel method for the segmentation of Multiple Sclerosis (MS) lesions in MRI. The method is based on a three-step approach: first a conventional k-NN classifier is applied to pre-classify gray matter (GM), white matter (WM), cerebro-spinal fluid (CSF) and MS lesions from a set of prototypes selected by an expert. Second, the classificat...
Conference Paper
Full-text available
In this paper, we propose a new approach to compute geodesic distance transformations in arbitrary 2D and 3D domains. The distance transformation proposed here is robust and has proved to have a computational complexity linear in the domain size. Our scheme is based on a new technique which we call occlusion points propagation, and with a higher ac...
Conference Paper
Full-text available
Fixed networks of computers constitute the lowest cost as well as the most available parallel computer, however the proliferation of wireless devices allows to expand the parallel virtual machine. These clusters are composite by resources with different performances and also are connected by communication links with different bandwidth, such as Fas...
Conference Paper
Full-text available
Traditionally, the Local Area Network (LAN) has been used for parallel programming. However, with recent advances in wireless communications, some authors think that the future of Wireless Local Area Networks (WLAN) depends on the demonstration of its application to real problems. In this paper we prove that wireless communications are suitable to...
Conference Paper
Traditionally, a local area network (LAN) has been used for parallel programming with PVM and MPI. The improvement of communications in wireless local area networks (WLANs) achieving up to 11 Mbps make them, according to some authors, candidates to be used as a resource for grid computing. In this paper we use our library based on LAM/MPI named LAM...
Conference Paper
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Heterogeneous clusters provide an attractive scalability of low cost in terms of computation power. However, these systems are much complicated to program than dedicated parallel machines due to the perfomance of nodes and traffic in the network changes randomly. Execution of a parallel application in a heterogeneous cluster without keeping in mind...
Chapter
Full-text available
Recent advances in wireless communication technology are making Wireless Local Area Networks (WLAN) an appealing vehicle for parallel and distributed network based computing. The features of the wireless physical level lead new challenges when designing parallel applications. One important challenge is to guarantee the successful completion of the...