The WSUs were configured such as end devices to deploy
a networking topology point-to-point based on a coordinator
that was implemented by the XBee radio modem of the WIU.
An end device has the following characteristics: 1) it must join
a ZigBee PAN before it can transmit or receive data; 2) cannot
allow devices to join the network; 3) must always transmit and
receive RF data through its parent; 4) cannot route data; and
5) can enter low power modes to conserve power and can be
battery powered.