Routing recommendations for low-latency 802.15.4 control networks

Inhalt:
In many applications of wireless control networks, the latency of message delivery is an important consideration. Typically, in a lighting control network where a light switch sends a wireless message to a lamp, a worst case end-to-end latency of 200 ms or better is desired, so that the working of the switch feels 'immediate' to the end user. Based on a detailed study of the latency performance of a test network located in a real-life office environment, this paper recommends that several key elements are included in a routing system designed to optimize worst case latency. In particular, it is recommended that each node maintains a list of multiple target routers that it can use to deliver a message, and that the node quickly switches to another target router if a delivery acknowledgement from the preferred router is not received. It is also shown that battery powered sensor nodes can use a fast re-try strategy to optimize latency, without great impact on their battery lifetime.