José Manuel Cano-García

Modeling of Current Consumption in 802.15.4/ZigBee Sensor Motes

Battery consumption is a key aspect in the performance of wireless sensor networks. One of the most promising technologies for this type of networks is 802.15.4/ZigBee. This paper presents an empirical characterization of battery consumption in commercial 802.15.4/ZigBee motes. This characterization is based on the measurement of the current that is drained from the power source under different 802.15.4 communication operations. The measurements permit the definition of an analytical model to predict the maximum, minimum and mean expected battery lifetime of a sensor networking application as a function of the sensor duty cycle and the size of the sensed data.

Modelling of Individual and Aggregate Web Traffic

This paper describes the behaviour of individual Web users as well as aggregate HTTP traffic basing on actual traces taken from a transoceanic link between Japan and USA. The proposed model characterises the traffic at different levels, ranging from packets to Web pages. Thus, the study investigates the effects of aggregation on the heavy-tailed nature and the long range dependence present in the variables which govern Internet traffic.

UMAFall: A Multisensor Dataset for the Research on Automatic Fall Detection

Abstract The progress in the field of inertial sensor technology and the widespread popularity of personal electronics such as smartwatches or smartphones have prompted the research on wearable Fall Detection Systems (FDSs). In spite of the extensive literature on FDSs, an open issue is the definition of a common framework that allows a methodical and agreed evaluation of fall detection policies. In this regard, a key aspect is the lack of a public repository of movement datasets that can be employed by the researchers as a common reference to compare and assess their proposals. This work describes UMAFall, a new dataset of movement traces acquired through the systematic emulation of a set of predefined ADLs (Activities of Daily Life) and falls. In opposition to other existing databases for FDSs, which only include the signals captured by one or two sensing points, the testbed deployed for the generation of UMAFall dataset incorporated five wearable sensing points, which were located on five different points of the body of the participants that developed the movements. As a consequence, the obtained data offer an interesting tool to investigate the importance of the sensor placement for the effectiveness of the detection decision in FDSs.

An empirical evaluation of the consumption of 802.15.4/ZigBee sensor motes in noisy environments

This paper presents an empirical study of the effects of the channel occupation on the consumption of actual IEEE 802.15.4/ZigBee motes. The study is focused on the current demanded by a sensor node in a simple beaconless star topology when the CSMA contention algorithm introduces idle times in the activity of the radio transceiver. For this purpose, the developed testbed permits to define the probability of failure of the CCA (Clear Channel Assessment) operation, which is executed by the 802.15.4 MAC layer to check the availability of the radio channel before any transmission. The obtained results evidence that the sensor lifetime can be seriously diminished for CCA failure rates higher than 30%, which can be a common situation in Wireless Sensor Networks with tens of nodes where data must be updated several times per second.

Topic-Dependent Language Model Switching for Embedded Automatic Speech Recognition

Embedded devices incorporate everyday new applications in different domains due to their increasing computational power.Many of these applications have a voice interface that uses Automatic Speech Recognition (ASR). When the complexity of the language model is high, it is common to use an external server to perform the recognition at the expense of certain limitations (network availability, latency, etc.). This paper focuses on a new proposal to improve the efficiency of the usage of the language model in a recognizer for multiple domains. The idea is based on the selection of a proper language model for each domain within the ASR system.

Characterization of battery consumption in 802.15.4/ZigBee sensor motes

Battery consumption is a key aspect in the performance of wireless sensor networks. One of the most promising technologies for this type of networks is 802.15.4/ZigBee. This paper presents an empirical characterization of battery consumption in commercial 802.15.4/ZigBee motes. This characterization is based on the measurement of the current that is drained from the power source under different operations of 802.15.4 communications. The measurements permit to define a model to predict the battery lifetime of a sensor networking application as a function of the sensor duty cycle and the size of sensed data.

Rule-Based vs. Behavior-Based Self-Deployment for Mobile Wireless Sensor Networks

In mobile wireless sensor networks (MWSN), nodes are allowed to move autonomously for deployment. This process is meant: (i) to achieve good coverage; and (ii) to distribute the communication load as homogeneously as possible. Rather than optimizing deployment, reactive algorithms are based on a set of rules or behaviors, so nodes can determine when to move. This paper presents an experimental evaluation of both reactive deployment approaches: rule-based and behavior-based ones. Specifically, we compare a backbone dispersion algorithm with a social potential fields algorithm. Most tests are done under simulation for a large number of nodes in environments with and without obstacles. Results are validated using a small robot network in the real world. Our results show that behavior-based deployment tends to provide better coverage and communication balance, especially for a large number of nodes in areas with obstacles.

Analysis of a Smartphone-Based Architecture with Multiple Mobility Sensors for Fall Detection

During the last years, many research efforts have been devoted to the definition of Fall Detection Systems (FDSs) that benefit from the inherent computing, communication and sensing capabilities of smartphones. However, employing a smartphone as the unique sensor in a FDS application entails several disadvantages as long as an accurate characterization of the patient’s mobility may force to transport this personal device on an unnatural position. This paper presents a smartphone-based architecture for the automatic detection of falls. The system incorporates a set of small sensing motes that can communicate with the smartphone to help in the fall detection decision. The deployed architecture is systematically evaluated in a testbed with experimental users in order to determine the number and positions of the sensors that optimize the effectiveness of the FDS, as well as to assess the most convenient role of the smartphone in the architecture.During the last years, many research efforts have been devoted to the definition of Fall Detection Systems (FDSs) that benefit from the inherent computing, communication and sensing capabilities of smartphones. However, employing a smartphone as the unique sensor in a FDS application entails several disadvantages as long as an accurate characterization of the patients mobility may force to transport this personal device on an unnatural position. This paper presents a smartphone-based architecture for the automatic detection of falls. The system incorporates a set of small sensing motes that can communicate with the smartphone to help in the fall detection decision. The deployed architecture is systematically evaluated in a testbed with experimental users in order to determine the number and positions of the sensors that optimize the effectiveness of the FDS, as well as to assess the most convenient role of the smartphone in the architecture.

An empirical study on the performance of bluetooth scatternets

Bluetooth scatternet technology was conceived to provide support for ad hoc multihop networking applications. Many theoretical works in the literature have been dedicated to optimize the formation and operation of Bluetooth scatternets. However, the performance of a real scatternet strongly relies on the implementation of the Bluetooth stack in the interfaces of the network nodes. By analyzing the behavior of a simple scatternet of three nodes, this paper shows evidence of the scalability and delay problems that can appear when scatternets are deployed on existing hardware interfaces.

ECA-based control interface on Android for home automation system

Historically, Embodied Conversational Agents (ECAs) have been used as virtual assistants that make easier the access to information or help in performing complex tasks. Due to their high computational requirements ECAs are usually run on desktop computers, but with the recent development of hand-held devices both in hardware and software, it becames neccessary to move ECAs to that new mobile scenario. Thus, we propose an open-source based platform for developing ECA based interfaces on Android-equipped devices. We also present a prototype for controlling a home automation system.