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Chapter 2
Wireless Network Concepts
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2.2 Node Types
In addition to running an application (e.g. temperature measurement), each node of a
wireless network has a networking role. Most IEEE 802.15.4-based networks can
contain three types of node, differentiated by their networking roles, as described
below (ZigBee RF4CE is an exception):
The roles of the above node types will become more apparent in Section 2.4 on
network topologies.
2.3 Network Identification
A wireless network must have a unique identifier which allows it to be distinguished
from other networks in the same operating neighbourhood. IEEE 802.15.4-based
protocols use a 16-bit value called the PAN ID. This identifier is used by the lower
levels of the software stack to identify the network - for example, in the delivery of
messages sent between nodes. It can be pre-defined in the user application or chosen
by the PAN Co-ordinator, but it must not clash with the PAN ID of a neighbouring
network.
A wireless network protocol may also use its own network identifier (in addition to the
PAN ID) - for example, in the JenNet-IP protocol, a 32-bit Network Application ID is
implemented at the application level.
Node Type Description
Co-ordinator A wireless network has one and only one Co-ordinator, or PAN Co-ordinator. This
node has a role in starting and forming the network, and can also have a routing role
(passes messages from one node to another). Messages can also originate and
terminate here.
Router This node passes messages from one node to another. Messages can also originate
and/or terminate at a Router. This node type is also sometimes referred to as a Local
Co-ordinator.
End Device This node is simply a place where messages can originate and/or terminate (the
node does not have a routing role). In order to conserve power, an End Device can
sleep when it is not required to be active.
Table 2: Node Types in a Wireless Network