A residential maintenance-free long-term activity monitoring system for healthcare applications
Fafoutis et al. EURASIP Journal on Wireless Communications and
Networking
A residential maintenance-free long-term activity monitoring system for healthcare applications
Xenofon Fafoutis 0
Evgeny Tsimbalo 0
Evangelos Mellios 0
Geoffrey Hilton 0
Robert Piechocki 0
Ian Craddock 0
0 Department of Electrical and Electronic Engineering, University of Bristol , Woodland Road, BS8 1UB Bristol , UK
Demographic changes such as the ageing population and the continuous rise of chronic medical conditions such as obesity, diabetes and depression make our healthcare systems economically unsustainable. Sensing technologies are promising solutions that can provide cost-effective answers to these challenges. In this paper, we focus on long-term in-house activity monitoring that aims at early detection and prevention of such conditions. In this context, we present and experimentally evaluate an ultra low-power (less than 100-μW long-term average power consumption) on-body activity sensing prototype system that is based on Bluetooth low energy (BLE). As part of a larger smart home monitoring architecture, the role of the presented system is to collect and reliably deliver acceleration data to the upper layers of the architecture. The system evaluation incorporates a thorough power consumption study that facilitates meaningful battery lifetime estimations, an insightful coverage study in an actual residential environment, and the investigation of energy-efficient packet loss mitigation techniques.
eHealth; mHealth; Wearable technologies; Healthcare technologies; Internet of things; Bluetooth low energy
1 Introduction
Our healthcare systems are challenged by demographic
changes. The United Nations (UN) predicts that in 2050,
the proportion of the population aged over 60 in the
developed world will be 33 %, following an increasing trend [
1
].
In addition to continuously ageing populations, the rise of
chronic illness pushes the limits of our healthcare systems
which makes them unsustainable [
2
]. As medical
professionals report that early detection and prevention is more
cost-effective than treatment [
3
], there is a shift towards
encouraging people to manage their own well-being at
home. Residential healthcare is not only cost-effective,
but it is also supporting the dignity and independence
of the elderly [
4
]. Advances in Ambient Assisted Living
(AAL) [
5
], wireless sensor networks (WSN) and wearable
technologies [
6
] provide the necessary infrastructure to
support such a shift in healthcare provision.
In this context, the focus of this paper is on long-term
activity monitoring in a residential environment. The key
challenge of long-term activity monitoring is the energy
constraints of wearable hardware. Low power
consumption is a key goal of all wireless sensing systems, primarily
due to the associated costs of replacing or recharging
batteries. To make matters worse, in the context of our
application of interest, the users of the system are either
elderly or suffering from medical conditions, making the
option of user-based system maintenance unrealistic. For
these reasons, our aim is an ultra low-power system with
a long-term average power consumption of the order of
tens of microwatt. Such levels of power consumption
correspond to a long battery lifetime, hence, a system that can
support maintenance-free residential monitoring for
several months. Although only battery-powered solutions are
considered in this paper, it should be noted that such low
levels of power consumption also facilitate the realisation
of completely maintenance-free energy harvesting sensing
systems [
7
], where sensors are powered by the—typically
very limited—energy that is available in the surrounding
environment. In our proposed platform, the energy
efficiency of the wearable device is also enhanced by
exploiting the asymmetry of the network resources. Instead of
energy-consuming retransmissions, reliable
communication is achieved through incorporating energy-efficient
packet loss mitigation techniques that are primarily
supported by the mains-powered infrastructure.
The presented activity monitoring system is based on
Bluetooth low energy (BLE) and is part of a larger
platform that we call the SPHERE (a Sensor Platform for
HEalthcare in a Residential Environment) architecture [
8
].
The SPHERE architecture is a residential platform that
is armed with environmental sensors, video cameras and
on-body sensors for sensing, as well as high-performance
computing systems for real-time reasoning and
decisionmaking with machine learning algorithms. A prototype of
the SPHERE architecture is being engineered and realised
in a furnished house in the city of Bristol, UK, which,
for the remainder of the paper, will be referred to as
the SPHERE house. The purpose of the SPHERE house
is to host volunteers, so that the SPHERE technologies
can be tested on real subjects. As part of the SPHERE
architecture, the scope of the presented a (...truncated)