Sergio González-Valenzuela

Mobility Support for Health Monitoring at Home Using Wearable Sensors

We present a simple but effective handoff protocol that enables continuous monitoring of ambulatory patients at home by means of resource-limited sensors. Our proposed system implements a 2-tier network: one created by wearable sensors used for vital signs collection, and another by a point-to-point link established between the body sensor network coordinator device and a fixed access point (AP). Upon experiencing poor signal reception in the latter network tier when the patient moves, the AP may instruct the sensor network coordinator to forward vital signs data through one of the wearable sensor nodes acting as a temporary relay if the sensor-AP link has a stronger signal. Our practical implementation of the proposed scheme reveals that this relayed data operation decreases packet loss rate down to 20% of the value otherwise obtained when solely using the point-to-point, coordinator-AP link. In particular, the wrist location yields the best results over alternative body sensor positions when patients walk at a 0.5 m/s.

Body Area Networks

Body area network (BAN) technology has emerged in recent years as a subcategory of wireless sensor network technology targeted at monitoring physiological and ambient conditions surrounding human beings and animals. However, BAN technology also introduces a number of challenges seldom seen before due to the scarcity of hardware and radio communication resources and the special properties of the radio environment under which they operate. In this chapter, we review the foundations of BANs along with the most relevant aspects relating to their design and deployment. We introduce current, state-of-the-art applications of BAN, as well as the most challenging aspects concerning their adoption and gradual deployment. We also discuss issues pertaining to sensor node communications, trade-offs, and interfacing with external infrastructure, in addition to important aspects relating to wearable sensor technology, enabling software and hardware, as well as future trends and open research issues in BANs.

Employing IEEE 802.15.4 for Quality of Service Provisioning in Wireless Body Area Sensor Networks

A wireless body area sensor network (WBASN) is a wireless networking technology that interconnects tiny nodes with sensing capabilities in, on or around a human body. The vital-sign information collected by these sensors can then be used by care-givers to assess the health of a patient. Therefore, it is necessary to provide reliable communication services to prioritized WBASN data streams with quality of service (QoS) guarantees. However, existing research has not devoted enough attention to this issue. This paper proposes a QoS provisioning framework for WBASN traffic employing the IEEE 802.15.4 super-frame structure in the beacon-enabled mode. A method of prioritizing WBASN traffic is proposed, along with algorithms for admission control and scheduling. Computer simulations reveal that our scheme is able to guarantee a 100% time constraint compliance ratio for traffic in contention access periods, and a 99.2% to 99.9% constraint compliance ratio for traffic in contention-free periods, while still admitting and accommodating tens of WBASN traffic streams.

A wireless sensor system for motion analysis of Parkinson's disease patients

We describe the initial design, implementation and testing of a wearable sensor system employed for human motion analysis. Our proposed system is part of an ongoing investigation aimed at efficiently timing the self-administration of prescription drugs in Parkinsons disease patients by using wireless sensors to capture distinctive motion patterns that indicate the onset of dyskinesia lapses as the prescription drug wears off. Our prototype incorporates three pairs of accelerometer/gyroscope sensors, each connected to a wireless node equipped with an IEEE 802.15.4 radio. Sensor data are transmitted to a computer that is employed for visualization. We describe practical experience encountered during the initial development of our prototype, and outline the potential battery and bandwidth conservation benefits introduced by employing popular signal processing methods.

Directional source grouping for multi-agent itinerary planning in wireless sensor networks

As software entities that migrate among nodes, mobile agents (MAs) are able to deliver and execute codes for flexible application re-tasking, local processing, and collaborative signal and information processing. In contrast to the conventional wireless sensor network operations based on the client-server computing model, recent research has shown the efficiency of agent-based data collection and aggregation in collaborative and ubiquitous environments. In this paper, we consider the problem of calculating multiple itineraries for MAs to visit source nodes in parallel. Our algorithm iteratively partitions a directional sector zone where the source nodes are included in an itinerary. The length of an itinerary is controlled by the angle of the directional sector zone in such a way that near-optimal routes for MAs can be obtained by selecting the angle efficiently in an adaptive fashion. Simulation results confirm the effectiveness of the proposed algorithm as well as its performance gain over alternative approaches.

Wireless Body Area Network Node Localization Using Small-Scale Spatial Information

We present a new scheme to automatically identify the locations of wearable sensor nodes in a wireless body area network (WBAN). Instantaneous atmospheric air pressure readings are compared to map nodes in physical space. This enhancement enables unassisted sensor node placement, providing a practical solution to obtain and continuously monitor node locations without anchor nodes or beacons. To validate this localization scheme, a statistical analysis is conducted on a set of air pressure sensors and a prototype WBAN to examine the performance and limitations. Based on a 60 cm separation between nodes, indicative of the expected separation between limbs and placement positions along a patients body, the measurements consistently exceeded p -value reliability within a 95% confidence interval. We also present and experimentally demonstrate an enhancement aiming to reduce false-positive (Type I) errors in conventional accelerometer-based on-body fall detection schemes. Our statistical analysis has shown that by continuously monitoring the patients limb positions, the WBAN would be better able to discriminate “fall-like” motions from actual falls.

Software Agent-based Intelligence for Code-centric RFID Systems

Radio frequency identification (RFID) is a kind of electronic identification technology that is becoming widely deployed. Due to its intrinsic small size and low cost features, the RFID technology can be readily integrated into various systems for future smart environment applications, whereby vital information is retrieved by diverse types of communications networks. In order to launch a specific service in an existing RFID system, object identification is first performed to retrieve the corresponding service codes from a backend database. However, the critical gaps that may exist in the identification recognition and subsequent handover of service codes from a database to a service machine can make it challenging to offer a good quality of service. This paper introduces a Code-centric RFID System based on an agent intelligence scheme that can potentially achieve faster service response. In this system, we replace traditional ID numbers with codes that indicate the service that the RFID tag bearer needs for improved system response.

Applications of Mobile Agents in Wireless Networks and Mobile Computing

Abstract We examine the applicability of mobile software codes to perform networking tasks in wireless and mobile computing environments. We contend that the advent of wireless technologies during the past decade has turned computer networks increasingly complex to manage. In particular, factors such as context awareness and user mobility are now crucial in the design of communications protocols used by portable devices with moderate to severe bandwidth and battery power limitations. Unlike hard-coded communication protocols that fulfill a specific need, mobile software agents can be deployed to deal with a range of tasks and can be designed to efficiently adapt to diverse circumstances. We present our latest advancements in the areas of mobile ad hoc networking and wireless sensor networks using mobile agents (MAs). We also elaborate on the importance of engineering an efficient migration strategy as the single most distinctive proceeding that an MA performs to operate efficiently. In addition, we describe the Wiseman system for scripting MAs that can perform networking tasks in both homogeneous and heterogeneous wireless network environments. Monitoring, tracking, and E-healthcare applications are discussed and evaluated at length.

Multipoint-to-Point Routing with QoS Guarantees Using Mobile Agents

To overcome the shortcomings of existing IP networks and to facilitate the overall quality-of-service (QoS) provisioning in the near-future networks, new technologies such as Multi-Protocol Label Switching (MPLS) and Differentiated Services (Diffserv) have been proposed for support of differentiation of classes of services and guarantee of QoS. Diffserv and MPLS, however, require improved capabilities from the current routing algorithms. In this paper, we investigate such an improvement by developing algorithms for determining the optimal multipoint-to-point (mp2p) routes through the use of mobile software agents. We present an mp2p routing scheme using a mobile intelligent agent system, called WAVE. The agents work in a highly distributed and parallel manner, cooperating to determine optimal routes in an mp2p connection scenario. This work aims at closing the gap between the theoretical routing research based on mobile agents, and practical routing requirements for real world networks that are likely to be deployed during the forthcoming years.

Design, Implementation and Case Study of WISEMAN: WIreless Sensors Employing Mobile AgeNts

We describe the practical implementation of Wiseman: our proposed scheme for running mobile agents in Wireless Sensor Networks. Wiseman’s architecture derives from a much earlier agent system originally conceived for distributed process coordination in wired networks. Given the memory constraints associated with small sensor devices, we revised the architecture of the original agent system to make it applicable to this type of networks. Agents are programmed as compact text scripts that are interpreted at the sensor nodes. Wiseman is currently implemented in TinyOS ver. 1, its binary image occupies 19Kbytes of ROM memory, and it occupies 3Kbytes of RAM to operate. We describe the rationale behind Wiseman’s interpreter architecture and unique programming features that can help reduce packet overhead in sensor networks. In addition, we gauge the proposed system’s efficiency in terms of task duration with different network topologies through a case study that involves an early-fire-detection application in a fictitious forest setting.