Applications and communication patterns for WSN N. Reijers Consensus day TU Delft February 7, 2003

WSN applications and traffic MAC simulation requires generating realistic WSN traffic Routing Data aggregation OS Expected to have special characteristics

Application scenarios Intruder detection Forest fire detection Cattle herd Battle field Fire rescue Environmental monitoring Condition based maintenance Airconditioning sensors

Application types 3 types of applications Detection Tracking Active Passive Monitoring Push Pull Communication Event Periodic/event Periodic Query/response

Example: Sheep tracking Farmers want to know: Rough location of their sheep When a sheep wanders off from the herd When a sheep is lying on its back Sensor nodes spread throughout the meadow Sheep carry a node that periodically sends a beacon pulse

Sheep tracking approaches Raw data to sink Very inefficient Active node Cheap in terms of communication Rough location estimate Local triangulation More expensive in terms of communication More accurate location

Active node Sink Sheep

Active node Sink Sheep

Local triangulation Sink Sheep

WSN application characteristics Activity is often very localized both in space and time High latency is tolerable Available bandwidth >> required bandwidth Messages local or node->sink sink->node are rare

Application model Capture charateristics in application scenarios Generate traffic which is typical for WSN Scenario description Network description Traffic generation Active areas

Network model Number of nodes Placement of nodes Random Grid Radio range Number of sinks Placement of sinks Center / edge / corner

Traffic generation (1) Generate random messages Rate (msgs/sec) Type, selected according to given ratio Local broadcast Local unicast Node -> sink Sink -> node Sink -> all % 50 % 12 % 0 %

Traffic generation (2) For each message type, specify Message size Allowed latency For node->sink messages specify aggregation type None Concatenation Averaging

Active areas Active areas appear randomly Rate (new areas/sec) Avg lifetime Avg size 2 nd set of parameters for active areas Traffic generated for active areas is added to normal traffic

Conclusion Specific characteristics of WSN applications localized activity latency available bandwidth >> required bandwidth messages local or node->sink sink->node are rare Traffic generation algorithm to model these