Routing on a Logical Grid in Sensor Networks

We present a protocol for routing data messages from any sensor to the base station in a sensor network. The protocol maintains an incoming spanning tree whose root is the base station. The spanning tree is constructed as follows. First, each sensor in the network is assigned a unique identifier as if the sensors form a logical two-dimensional grid. Second, each sensor, other than the base station, uses its own identifier to compute the identifiers of its “potential parents” in the spanning tree. Third, the base station starts to periodically send “connected messages”. When a sensor receives a connected message from anyone of its potential parents, the sensor makes this potential parent its parent in the tree and starts to periodically send connected messages. This routing protocol has three advantages over earlier protocols: overhead of the protocol is very small, the protocol balances the load over the whole network, and the protocol has nice fault-tolerance and security properties. We have implemented this protocol over a sensor network that consisted of about 50 MICA2 motes and observed that the protocol delivers 72% – 99% of the messages to the base station under heavy and bursty traffic (that generated 100 data messages per 15 seconds). We also ran the same experiment on a version of the distance vector routing protocol and observed that this protocol can delivery only 34% of the messages to the base station.