Why do I see large delays when sending rapid Broadcast packets - using an address of 0xFFFF?
Unlike unicast transmission that supports acknowledgment of data delivery to avoid unnecessary retires, Broadcast transmission needs to be repeated three times by all nodes for every instance in order to make sure that it reaches all corners of network.
Each radio must keep a table of the packet that it has already re-broadcast. This prevents endless repeating of broadcast packets. A node that transmits the broadcast creates an entry in a local broadcast transmission table. The table size is limited (usually to about 8 entries) and must hold a packet until it's propagatoin is compelted. This effectively limits the application broadcast transmissions to not more than once per second.
Zigbee networks are not ideal for high data throughput. If constant streaming type data is desired, it is recommended to use Unicast addressing and limit the number of hops in the network or to use the Digimesh protocol which does not have these limitations. Digimesh will run on the same hardware platform and can be loaded using the Digi XCTU tool.
Aug 23, 2017