OPAG: Opportunistic Data Aggregation in Wireless Sensor Networks

We propose Opportunistic Data Aggregation (OPAG) that incurs no computation error and tolerates moderate message losses in wireless sensor networks (WSNs). OPAG performs in-network data aggregation in two layers: (1) at the data-aggregation layer, aggregation results are computed accurately; and (2) at the data-routing layer,a WSN node may send intermediate/partial results to its aggregation node using multi-path routing in order to tolerate message losses.By space-multiplexing messages (i.e., padding multiple partial results or sensor readings in a single message), OPAG opportunistically exploits a multi-path routing scheme, which is more energy-efficient than retransmission. This is based on a key observation that, when sending a message, the radio may consume much more energy in idle listening during the backoff period and the time to wait for its acknowledgment than transmitting the data bits.We implemented OPAG on TinyOS 2.x and TMote Sky Mote, and evaluated its performance on the Motelab Testbed at Harvard University.When a network is relatively well connected, OPAG can reduce the energy consumption by 33% at the expense of slightly higher relative errors, compared to TAG with reliable transmission.Compared to synopsis diffusion, OPAG can reduce the aggregation errors by 50% while consuming roughly the same amount of energy.