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

30-6 Industrial Communication Systems
robustness, redundancy, and support for high-speed cyclical data transmission) to the requirements of a
bedside communication application. The proposed system includes a bedside monitor, an actuator unit,
an environment unit, and a central monitor. The bedside monitor collects the patient’s vital signals,
enabling the measurement of parameters, such as heart rate (number of heart beats per minute, pulse),
end-tidal lung volume (liters per minute), respiration rate (number of breaths per minute), and systolic
and diastolic arterial blood pressure values (mmHg). The remote control of bedside devices (e.g., infusion
pumps) is enabled by the actuator unit, which can drive digital and analog outputs. Environmental
parameters (e.g., temperature) and discrete inputs (e.g., nurse call button) are monitored using the environmental
unit. These devices (slaves) are placed nearby a patient’s bed and are connected to the central
monitor (master) by a Profibus DP network operating at 1.5.Mbps. The central monitor provides functions
like real-time reception and a display of bedside data of up to 16 patients, signal interpretation,
and alarming with event logging, etc. Redundancy can be provided by interconnecting devices using
a two-wire cable on a bus topology.
30.4.3 IEEE 802.15.4
The IEEE 802.15.4 is a low-power, low-cost PAN technology with application in smart home health
monitoring and in BANs. Both Dagtas et al. [19] and Junnila et al. [20] propose a smart home
wireless health monitoring system based on ZigBee technology. However, their architectures are
different: the first employs three tiers for data collection and processing while the second uses a
two-tiered approach. The first tier of the Dagtas et al. monitoring system corresponds to the mobile
device worn by the patient that collects signals from wired and wireless sensors. This device periodically
transmits raw data to a local server for storage and processing (second tier). Here, further
processing is carried out and the resulting data are transmitted to the service provider center for
storage, expert review, and diagnosis (third tier). The UUTE home network [20] encompasses sensor
nodes, a coordinator, a home client, and a server. Sensor nodes communicate directly with
the coordinator, responsible for setting up and managing the ZigBee network. Additionally, the
coordinator provides information to the home client about sensors that joined/left the network and
forwards data from/to the ZigBee network. The home client operates as a processing unit for the
data coming from the ZigBee sensor network, stores it locally, provides a user interface, and acts
as a gateway to a remote UUTE server where data are stored for redundancy (and future analysis).
The UUTE home network employs nonbeaconed ZigBee communications, offers no guarantees of
data delivery, and as two-way communication is desired, has no support for power consumption
optimization.
The architectures of the BANs proposed by Monton et al. [21] and Lo et al. [22] are very similar.
A BAN encompasses a set of sensors (ECG, temperature, SpO 2 , etc.) equipped with wireless transceivers
that periodically transmit data to a local central device (e.g., PDA) where data are processed
and transmitted to a server for long-term storage. Monton et al. define a proprietary BAN protocol
compatible with IEEE 802.15.4 and ZigBee that operates using the beaconed mode of IEEE 802.15.4.
At the beginning, a sensor node associates with the coordinator (central node) and waits for beacons
by enabling the receiver the instant immediately before the beacon transmission. In addition
to information on the instant of the next beacon transmission, beacons can transport commands for
the sensor nodes (configuration, activation/deactivation, and data transmission). After the activation
of the sensor node, data collection begins from the attached sensor(s) until a complete data frame
is filled. This frame is sent to the central node when a data transmission command is received. The
central node stores sensor data and makes it available to the outside world using the Session Initiation
Protocol (SIP) over technologies, such as the IEEE 802.11 (Wi-Fi) and GPRS. The BAN proposed by
Lo et al. employs standard IEEE 802.15.4 communications, including context-aware sensors (e.g.,
accelerometer) that are used in multisensor data fusion for false alarm detection and bandwidth
usage minimization.
© 2011 by Taylor and Francis Group, LLC