P3: A Practical Packet Pipeline using synchronous transmissions for wireless sensor networks

While high throughput is the key for a number of important applications of sensor networks, performance of the state-of-the-art approach is often poor in practice. This is because if even one of the channels used in its pipeline is bad, the pipeline stalls and throughput degrades significantly. In this paper, we propose a new protocol called P3 (Practical Packet Pipeline) that keeps its packet pipeline flowing despite the quality differences among channels. P3 exploits sender and receiver diversities through synchronous transmissions (constructive interference), involving concurrent transmissions from multiple senders to multiple receivers at every stage of its packet pipeline. To optimize throughput further, P3 uses node grouping to enable the source to transmit in every pipeline cycle, thus fully utilizing the transmission capacity of an underlying radio. Our evaluation results on a 139-node testbed show that P3 achieves an average goodput of 178.5 Kbps while goodput of the state-of-the-art high throughput protocol PIP (Packets In Pipeline) is only 31 Kbps. More interestingly, P3 achieves a minimum goodput of about 149 Kbps, while PIP's goodput reduces to zero in 65% of the cases.