wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

Communications in Medical Applications 30-5
The RSS-based approach is employed in localization systems, such as the Ekahau real-time location
system [15] or the AeroScout Visibility System [16], both based on IEEE 802.11 technology. The Ekahau
system is supported on a Wi-Fi infrastructure using an RSS fingerprinting localization technique. As
such, it uses 802.11b access points (AP) that measure the RSS of the packets sent by Wi-Fi-active RFID
tags, forwarding this data to a control platform where the localization is computed. The Ekahau system
supports a localization accuracy of 2.m. The Visibility System is a real-time localization system operating
with both TDOA and RSS techniques supported by Wi-Fi technology. Although the system includes
devices known as exciters to capture RFID responses from tags passing nearby, the localization is
mainly supported on wireless location receiver (WLR) devices measuring the TDOA and/or the RSS of
the transmissions received from tags, PDAs, laptops, etc. The information collected by WLRs and exciters
is then forwarded, using Ethernet, to the Aeroscout Engine where the localization is determined.
The manufacturer claims accuracies of 3–5.m when the TDOA localization technique is employed and
3–10.m when RSS base localization is used instead.
30.4 Clinical Monitoring
Clinical monitoring is a highly representative application of the support provided by communications
in healthcare environments. The remote collection of health data from patients at home, in healthcare
environments, and in some cases, in outdoor scenarios, allows healthcare professionals to follow their
patients’ condition in real time and with minimal intrusion, which facilitates disease management,
diagnosis, prediction, and follow-up. This improves the quality of life of elderly people and chronic
patients while promoting preventive lifestyles and early diagnosis for the general population. Besides
health motivations, clinical monitoring promotes the reduction of medical errors and the cost burden
caused by an aging society with a high incidence of chronic patients.
Both wired and wireless communication technologies have been reported in clinical applications,
such as bedside monitoring of inpatients or health monitoring using networks of sensors. Although
wired protocols are still dominant in safety-critical monitoring applications, wireless communications
are becoming a feasible alternative given their increasing performance, availability, and miniaturization.
The following subsections provide examples and an overview of clinical monitoring applications
employing wired and wireless communication technologies.
30.4.1 Controller Area Network
An example of the controller area network (CAN) technology applied to healthcare environments is the
support of networking for bedside medical instruments [17]. McKneely et al. propose a technology suite
named MediCAN• defining the hardware and the communication protocol to enable medical instrument
networking. The network architecture encompasses Hubs (bedside devices) providing connectivity
to the physical (MediCAN) instruments and gateways allowing high-level access to these instruments.
An Ethernet communication backbone connects gateways to a MediCAN server that maintains a real
time list of currently available MediCAN gateways and clients. The MediCAN technology suite defines
a set of network protocols that provide real-time client direct access to gateways and their resources
on a LAN, remote device control, and automatic remote data acquisition, among other features. The
MediCAN protocol supports data rates of up to 1.Mbps and shares the carrier-sense multiple-access protocol
with collision detection and arbitration on message priority (CSMA/CD + AMP) defined in CAN.
30.4.2 Profibus DP
A bedside patient monitoring system employing the Profibus DP fieldbus standard was proposed in [18].
The option for this fieldbus is justified by the adequacy of Profibus characteristics (e.g., determinism,
© 2011 by Taylor and Francis Group, LLC