ZFR1800 Series Wireless Field Bus System Technical Bulletin 67
Parent and Child Devices
In a wireless ZigBee network, a parent is a device that assigns unique network
addresses to other child nodes as they join the network. Any coordinator or router
can be a parent to other routers and end devices, but the coordinator is always a
parent device. When a router or end device joins the network, it selects a parent
from a group of routers or the coordinator. The selected parent may not always be
the closest node because the router or end device selects a parent based on signal
strength and its proximity to the coordinator. Once the router joins the network, it
no longer relies on its parent for communication; however, once an end device
joins, it continues to rely on its parent for all two-way communication.
In a ZigBee network, each coordinator and router has six addresses to give other
routers that want to join the network and 14 addresses for end devices. Once a
device has given out all of its available addresses, the device cannot give out more
addresses to add other devices to the network.
Note: This address limitation is based on the ZigBee Home Automation Profile.
Self-Healing, Multi-Hop Network
The ZigBee network is further characterized as a self-healing, multi-hop network.
If a wireless communication path experiences interference or drops out, the
network automatically reroutes the message through an alternate path to form a
new wireless communication path. Each message is received, then retransmitted as
it hops along from node to node until it reaches its final destination. Within a
ZigBee network, a single message is allowed to hop 10 times between the source
and destination node.
End Devices, Parent and Target Routers
An end device communicates through its parent router. This parent may also be the
target of the data. To illustrate, consider the partial wireless system shown in
Figure 22. The following parent and target relationships exist:
• For WRZ Sensor A1 and A2, Router A is both the parent and target node.
• For WRZ Sensor A3, Router A is its target node and Router D is its parent
node.
• For WRZ Sensor A4, Router B is its parent node and Router A is its target
node. If Router B becomes unreachable, Sensor A4 automatically finds a new
parent, which is Router C in this example. It then forwards its data through its
new parent, Router C, on to Router D, then finally to its target, Router A.
To Next Page
Loading...
Need help?
General
