Biomedical Engineering Reference
In-Depth Information
communication of less than 2 m is employed in the sensor tier. Sensor tier com-
munication is characterized by following features:
• Sensor nodes are connected to the gateway in a star topology.
• Sensor nodes have limited processing capabilities and very stringent require-
ments on power consumption.
• Unlike sensor nodes, gateway nodes are allowed to have higher processing
power and higher battery power.
• Communication is mostly one directional from sensor nodes to a gateway node.
• Communication from the gateway node to sensor nodes consists mainly of
network information and feedback.
A WBAN differs from a general Wireless Sensor Network (WSN) application
because of its specific requirements. Differences between a WBAN and a more
generic WSN are listed in Table
1.1
. WBAN applications, such as microelectronic
arrays and neural recording systems, use multi-channel monitoring, which dras-
tically increases the amount of data that needs to be transmitted simultaneously.
Wireless Capsule Endoscopy (WCE) is another type of WBAN devices that
requires high data rates for high resolution video transmission. Thus, there is a
demand for high data rate transmission of medical data. For example, a 128-
channel neural recording system with eight bit sampling requires a data rate in
excess of 10 Mbps [
6
]. Use of wired connections for data transmission is not
feasible at all times. It restricts the movement of the patient and involves painful
surgical procedures (for example in WCE). Basic requirements of a WBAN are
listed below.
1. Limited transmission range (\0.01-2 m).
2. Extremely low power consumption in sleep mode (0.1-0.5 mW) for each
device for longer battery life.
3. Support of scalable data rate ranging from 1 kbps to several Mbps.
4. Quality of Service (QoS) support for better handling of critical physiological
signals.
5. Low latency over a multi-hop network.
6. Small form factor and light weight devices.
1.2 Physical Layer Wireless Technologies Used in WBAN
Applications
There are several wireless technologies currently considered for data communi-
cation in WBAN applications. This section gives a brief introduction to some of
these important wireless technologies.
