The goal of the project is to investigate link and routing protocols for multi-hop wireless sensor networks that use a type of cooperative transmission called opportunistic large arrays (OLAs). An OLA is a large group of simple, inexpensive relays or forwarding nodes that behave without coordination between each other, but they naturally fire together in response to energy received from a single source or another OLA. Each node has just one antenna, however because the nodes are separated in space, they collectively provide diversity protection from multipath fading and they can reap the spectrum efficiency of a multiple-input-multiple-output (MIMO) system. It has been shown that under sufficient conditions during broadcast, OLAs form concentric rings that cover the whole network. Even when flooding the whole network, OLA networks have been shown theoretically to have significant advantages over conventional multi-hop networks in terms of reduced transmit energy, lower node complexity, better connectivity, and shorter end-to-end delay. Reduced energy consumption means sensor batteries last longer.
The project will further reduce the energy consumption of OLA networks by limiting the flood to be more like a river, many nodes wide, exploiting the ring structure to guide a message up to the sink. Developed protocols will exploit the trade-off between diversity and spatial multiplexing within OLAs to achieve connectivity while maximizing throughput. OLA link layer protocols will enable the river to flow around obstacles such as blockages or clusters of destroyed nodes, and resolve the situation when rivers collide.
