Riccardo Cavallari

A Survey on Wireless Body Area Networks: Technologies and Design Challenges

Interest in Wireless Body Area Networks (WBANs) has increased significantly in recent years thanks to the advances in microelectronics and wireless communications. Owing to the very stringent application requirements in terms of reliability, energy efficiency, and low device complexity, the design of these networks requires the definition of new protocols with respect to those used in general purpose wireless sensor networks. This motivates the effort in research activities and in standardisation process of the last years. This survey paper aims at reporting an overview of WBAN main applications, technologies and standards, issues in WBANs design, and evolutions. Some case studies are reported, based on both real implementation and experimentation on the field, and on simulations. These results have the aim of providing useful insights for WBAN designers and of highlighting the main issues affecting the performance of these kind of networks.

Experimental characterization of Low Power Listening in BAN

This paper presents an implementation of a Low Power Listening-based (LPL) Medium Access Control (MAC) protocol on a platform for Body Area Network (BAN) applications. LPL exploits the transmission of a burst of short packets, called preambles, to synchronize the transmitter and the receiver. In this way, devices are able to spend most of the time in sleeping mode, providing longer lifetime and energy saving. Experiments on the field have been conducted by considering different scenarios and results, in terms of average energy consumed per packet, packet loss rate and average delay, have been investigated. Conclusions regarding the proper parameters setting depending on the application requirements were derived. This work has been performed in the framework of the FP7 Integrated Project, WiserBAN.

Cost/speed analysis of mobile wireless DTNs under random waypoint mobility

We study a wireless network comprising an infinite number of nodes moving in ℝ2 according to a Random Waypoint (RWP) mobility model. Each node is equipped with a radio transceiver with transmission range R; a transmission across a distance d incurs a quadratic cost d2. We assume that a packet is generated at one node and must be delivered to a destination located at an infinite distance in the direction of the positive x-axis through a combination of wireless transmissions and physical transports on the buffers of nodes. A routing rule specifies when a wireless transmission should take place. Given this setting, we develop an analytic framework, using tools from stochastic geometry and Markov chains theory, to evaluate, with certain approximations, the tradeoff between the speed with which the packet travels toward the destination and the transmission cost incurred per unit of distance. Simulation results show a good match with the analytical results.

On the performance of IEEE 802.15.6 CSMA/CA with priority for query-based traffic

This paper presents a mathematical model to characterise the performance of a IEEE 802.15.6 Body Area Network (BAN), using a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol, when a query-based traffic is established. According to the latter, the BAN coordinator periodically triggers nodes, which will immediately start the CSMA/CA protocol, in order to send their data to the coordinator. The model evaluates the packet success probability and the mean delay of packets received from the coordinator. Each node is characterised by a User Priority (UP) value, which affects the Medium Access Control (MAC) protocol parameters. A set of experiments on a real platform has been performed to validate the model. This work can be considered the starting point for a development of a more elaborate mechanism to optimise the UP assignment in order to achieve the performance imposed by the application.

Experimental characterisation of energy consumption in Body Area Networks

This paper addresses the issue of power consumption in the field of Wireless Body Area Networks (WBAN). It presents a methodology used to perform real-time measurements of the energy consumption of a deployed WBAN, and describes how to design Medium Access Control (MAC) protocols, able to satisfy different application requirements in terms of lifetime, but also of latency. More precisely we analyse the performance of two MAC protocols, one based on low power listening and the other one based on the IEEE 802.15.6 standard, and we discuss their applicability to two specific scenarios. The evaluation is performed through experiments carried out on a hardware platform intended for WBANs, while the application scenarios are inspired by those defined in the FP7 EC Project, WiserBAN. Results obtained allow us to draw conclusions and considerations regarding energy consumption in realistic scenarios and provide significant inputs to WBAN designers.

Low Power Listening in BAN: Experimental Characterisation

This paper presents an implementation of a Low Power Listening-based LPL Medium Access Control MAC protocol on a platform for Body Area Network BAN applications. LPL exploits the transmission of a burst of short packets, called preambles, to synchronize the transmitter and the receiver. In this way, devices are able to spend most of the time in sleeping mode, providing longer lifetime and energy saving. Experiments on the field have been conducted by considering different scenarios and results, in terms of average energy consumed per packet transmitted/received, packet loss rate, average delay and network throughput, have been investigated. Conclusions regarding the proper parameters setting depending on the application requirements were derived. This work has been performed in the framework of the FP7 Integrated Project, WiserBAN.

Performance of a lamp post wireless backbone with Delay Tolerant offload

This paper presents a preliminary work based on the idea of offloading part of the traffic carried by a wireless multi-hop backbone on the lamp posts on a urban street to improve its throughput. Under some circumstances one or more nodes of the backbone may be congested, this could lead to packet losses. In order to overcome this situations, the backbone may decide to offload part of its traffic to the mobile nodes on the street (pedestrians and vehicles). These nodes form a Delay Tolerant Network (DTN) that delivers the offloaded data to the sink. Within this paper we characterise advances that the DTN offload brings to the performance of such a system under different operational conditions.