Energy-Efficient Strategies for Cooperative Communications in Wireless Sensor Networks

An opportunistic large array (OLA) is a group of simple, inexpensive relays or forwarding nodes that operate without any mutual coordination, but naturally fire together in response to energy received from a single source or another OLA. Therefore, OLAs do a form of cooperative transmission. OLAs, when used for broadcasting, form concentric rings around the source, and have been shown to use less energy than conventional multi-hop protocols. This paper proposes two energy efficient schemes: OLA-T for general OLA transmission and OLACRA for upstream routing in the topology of wireless sensor networks. OLA-T uses a transmission threshold to suppress nodes that would make weak contributions. OLA Concentric Routing Algorithm (OLACRA) exploits the concentric ring shapes of broadcast OLAs to limit flooding on the upstream connection. OLACRA-T is OLACRA with a transmission threshold. OLACRA-T and other variations of OLACRA are evaluated in terms of energy savings relative to a full flooding approach and probability of successful upstream routing. OLA-T and OLACRA-T are shown to save over 50% and 75%, respectively, of the energy relative to OLA flooding.