In applications where a device must transmit data to many remotes, AODV routing requires performing one route discovery for each destination device to establish a route. If there are more destination devices than there are routing table entries, new routes overwrite established AODV routes, causing route discoveries to occur more regularly. This can result in larger packet delays and poor network performance.
Zigbee source routing helps solve these problems. In contrast to many-to-one routing that establishes routing paths from many devices to one data collector, source routing allows the collector to store and specify routes for many remotes.
To use source routing, a device must use the API mode, and it must send periodic many-to-one route request broadcasts (AR command) to create a many-to-one route to it on all devices. When remote devices send RF data using a many-to-one route, they first send a route record transmission. The route record transmission is unicast along the many-to-one route until it reaches the data collector. As the route record traverses the many-to-one route, it appends the 16-bit address of each device in the route into the RF payload. When the route record reaches the data collector, it contains the address of the sender, and the 16-bit address of each hop in the route. The data collector can store the routing information and retrieve it later to send a source routed packet to the remote as shown in the following images.
The data collector sends a many-to-one route request broadcast to create reverse routes on all devices.
A remote device sends an RF data packet to the data collector. This is prefaced by a route record transmission to the data collector.
After obtaining a source route, the data collector sends a source routed transmission to the remote device.