Mobile Sampling of Sensor Field Data Using Controlled Broadcast

1. Mobile Sampling of Sensor Field Data Using Controlled Broadcast Investigators: Sol M. Shatz, Department of Computer Science Primary Grant Support: U. S. Army Research Office • A mobile object (car) is traveling along a path, and at some specific time/location (for example, T0) it decides to take a sample of the sensor field, i.e., collect sensor data from near-by sensor nodes. The larger circle denotes the sampling region. Each sensor in that region will consequently be activated and reply with its locally sensed data. • One challenge is in controlling the process that sensors use to respond to a request for sensor data from a mobile sink. This entails controlling how sensors route their sensed data to the mobile object. • Goal #1: Reduce message transmission • Goal #2: Reduce packet collisions • Concept of Band: Band i (0<i<N+1) = {(x,y) coordinates | a sensor node located at position (x,y) will receive the sampling signal with a signal-strength greater than or equal to SISi but less than SISi-1} where SIS represents sampling initiation signal strength. • Basic protocol: • Band scheduling: For sensor nodes in band i, there exists a specific time window, called the band’s stage and denoted Si, during which these nodes can report/broadcast their own sensor readings. Outside of this time window, these sensor nodes can only forward packets that originated in other (higher) bands. • Result #1: • The studied algorithm produced far less total messages sent (received) for serving each mobile sampling task than conventional flooding and counter-based broadcast, both under the simplified MAC protocol and collision/decay MAC protocol. • Result #2: • The packet collision rate also deceases significantly by employing the band scheduling method. • Some Future Goals: • Data aggregation using possible band scheduling arrangement. • Coordinating multiple sampling tasks that overlap with each other.