Ramona Rosini

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.

Body-to-Body communications: A measurement-based channel model at 2.45 GHz

This paper presents a channel characterisation for Body-to-Body communications. Starting from indoor real-time measurements at 2.45 GHz, the radio channel was modeled, both in Line-of-Sight (LOS) and Non Line-of-Sight (NLOS) conditions, through a mean channel gain component plus a fading contribution, the latter arising from the body movements. The body shadowing effect was also evaluated considering the orientation of one human body with respect to another one. Two different antennas were employed in the measurements, to assess their impact on the radio channel characteristics.

Body-to-Body Indoor Channel Modeling at 2.45 GHz

This paper presents an indoor Body-to-Body narrowband channel model based on experimental data, acquired through a real-time dynamic measurement campaign at 2.45 GHz. The radio channel was investigated under different communication conditions, according to the movement performed by some human subjects and to their mutual position. Several node locations were considered, and two antenna types were used to assess the impact of their radiation characteristics on channel properties. For each investigated link, the channel power transfer function was modeled as composed by a channel gain and a small-scale fading contribution, the latter arising from the multipaths due to the environment and the humans motion. The shadowing effect of the body was also evaluated considering that the body itself can act as an obstacle to the communication, according to its spatial orientation. Every model component was characterized for each scenario, highlighting how a specific movement results in different effects on channel dynamic properties.

Comparing On-Body dynamic channels for two antenna designs

This paper presents the characterisation of the transmission channel for On-Body communications at 2.45 GHz. Starting from real-time dynamic measurements, performed both in indoor and anechoic, the channel was characterised considering three different components: a mean channel gain, a shadowing and a fast fading contributions. The antenna effect on channel characteristics was accounted for, repeating all acquisitions with two different designs: one normally and the other one tangentially polarized with respect to the body surface.

Design of a body area network for medical applications: the WiserBAN project

This paper deals with some preliminary results achieved in the framework of the FP7 project WiserBAN (Smart miniature low-power wireless microsystem for Body Area Networks), aiming at the creation of a low-power and miniature microsystem targeting wearable and implanted devices for medical applications. The results achieved in the first year of the project, related to the radio channel characterization and protocol design, are reported. Different Medium Access Control protocols, based on existing and emerging standards, are proposed and their performance are compared. Results show that the proposed protocols allow to satisfy the end users requirements.

Comparing off-body dynamic channel model with real-time measurements

This paper presents a novel approach for modelling the influence of body dynamics on the radiation pattern of wearable antennas in Body Area Networks (BANs), particularly in off-body radio channels. The modelling of wearable antennas in BANs has been separated into antennas in the vicinity of the body (full wave simulations), including body dynamics (motion capture), and an indoor environment (clusters of scatterers). An anechoic and indoor scenarios are simulated, for a walking body, and for 3 on-body antenna placements (i.e., Arm, Head and Torso). The comparison of a path loss between simulated results and real-time measurements shows a good agreement, with an average difference of 4.5 dB (standard deviation of 0.1 dB) for the example case of the node on the Head, in an indoor environment.

A Correlation Model for Nonstationary Time-Variant On-Body Channels

The temporal variation of spatial correlation between on-body radio links is empirically characterized for different walking scenarios. Nonstationary behaviors are highlighted, and a model is proposed for the long-term fading correlation.