Alvaro Suárez

Gradient RSSI Filter and Predictor for Wireless Network Algorithms and Protocols

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. A figure used to control the connectivity of terminals to other terminals or to an Access Point (AP) is the well known Received Signal Strength Indicator (RSSI). Managing this figure it is possible to control the availability of a service in the wireless terminal. But the problem with RSSI is the fact that it exhibits high variability in space and time. Thus it is important to filter those values in order to efficiently manage the availability of the service in the mobile terminal. For that reason in this paper we present the experimental validation of a filter and a predictor of availability of a service in the wireless terminal based on the RSSI. We test the performance of the filter and the predictor that improves significantly other filters that are also presented in the paper. The significance of our work is that our filter allows simplifying a lot of network algorithms and protocols. As an example we present a simple protocol of handover in presence of multimedia information using our filter and predictor based on RSSI.

Full Geo-localized Mobile Video in Android Mobile Telephones

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 several photo and integral video tagging mobile software but there is not a mobile application that allows the mobile users to tag the full video frames. This full tagging process allows the mobile user to tag independent video frames in order to explode the photo-video properties of the integral video. In this paper we present a mobile application and a Server application that allow the mobile user to full tag the mobile videos and share them with other users (registered in the Server). We present some tradeoffs present in the design of the tagging process.

RSSI Prediction in WiFi Considering Realistic Heterogeneous Restrictions

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 best they know how. This is a problem because different scenarios can be found based in several elements like: the particular Wireless Fidelity Network Interface Card implementation, the driver, the operating system and software monitoring implementation. This makes the utilization of the Received Signal Strength Indicator to implement higher level functions in wireless networks (like roaming management or localization of terminals) be a headache in realistic scenarios. This heterogeneity of devices, drivers… makes that the application of the Received Signal Strength Indicator be not general. In this paper we present the comparison of our new model of Received Signal Strength Indicator prediction in several realistic and heterogeneous scenarios. The experimental results indicate that we obtain in general, better results than the other models.

Pipelining-based tradeoffs for hardware/software codesign of multimedia systems

In the last years, multimedia systems are present in an ever increasing number of applications. A software implementation often can not satisfy system timing constraints. This problem can be solved by adding specific hardware to the system. Lately, it has been developed some design methodologies for this type of hardware/software systems. Our research group have developed a hardware/software codesign environment named GACSYS (GACs Codesign System) for designing this type of systems. In this article, we present our Hw/Sw partitioning tool. Main contribution of our tool is the following: it supports process-level pipelining and takes into account system power consumption. Thus, system designer can explore the design space to make new latency, area and power trade-offs.

Anticipating Performance Information of Newly Portable Computers on the WLAN for Load Balancing

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 necessary to consider the unbalance communication bandwidths and computing power of fixed and portable computers to avoid long idle times. To solve this problem, in our previous work, we developed an efficient load balancing strategy considering that no new processes are spawned in new portable computers at run time. Due to it is not realistic, in this paper we present a new method for balancing the parallel calculations when parallel processes are spawned on portable computers which uses performance information supplied by a framework based on the standard Simple Network Management Protocol (SNMP). In this way, idle times are minimized and better execution times are obtained.

An improved mechanism for controlling portable computers in limited coverage areas

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 uses performance information of slave computers supplied by a framework based on Simple Network Management Protocol (SNMP). This strategy considers the received beacon strength in the portable computers for executing this kind of applications efficiently. However, when a portable computer is located in a limited coverage area, our framework considers that this resource is unavailable, and therefore it can’t be used for parallel computing. In this paper we present a mechanism based on the extension of our SNMP framework that allows us to use the computers while there is a wireless network connection.

A library for load balancing in master/slave applications on a LAN-WLAN environment

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 consider the unbalance both processing power and communication bandwidth of fixed and portable computers to avoid long idle times. To solve this problem, in our previous work we developed an efficient load balancing method that considers the heterogeneity both in computing and in communication, and besides, it keeps in mind that the number of processes can vary at run time (processes spawned on portable computers). To program this method is a hard task because it implements a complex mechanism to estimate the data distribution which uses a framework based on simple network management protocol (SNMP) that has to synchronize with the parallel program to share performance information about computers. For that reason, we present a library that implements our method of load balancing to ease the programming.

SGLOT: A Visual Tool for Structural LOTOS Specifications

LOTOS is a Formal Description Technique (FDT) that has a strong and obscure textual algebraic notation that is difficult in readability. We have developed a tool that allows to design visual specifications and generate the LOTOS equivalent code. With this tool a lot of time is saved in the specification phase of system simulation.

EVGC: A Tool for Visualizing LOTOS Behavioural Specifications

LOTOS is a Formal Description Technique (FDT) that has an strong and obscure textual algebraic notation that difficult its readability. To solve this problem we have developed a new tool that basically facilitates this readability. This tool represents graphically textual LOTOS specifications through a graph in which real time systems requirements could be considered. We have applied this tool to the specification of different systems.