Two Energy-Saving Schemes for Cooperative Transmission with Opportunistic Large Arrays

An opportunistic large array (OLA) is a form of cooperative diversity in which a large group of simple, inexpensive relays or forwarding nodes operate without any mutual coordination, but naturally fire together in response to energy received from a single source or another OLA When used for broadcast, OLAs form concentric rings around the source, and have been shown to use less energy than conventional multi- hop protocols. This paper proposes two schemes, one for general OLA transmission and one specifically for upstream routing in the topology of wireless sensor networks, that each save over 50% of the energy of flooding. The OLA-T scheme uses a transmission threshold to suppress nodes that would make weak contributions. The OLA Concentric Routing Algorithm (OLACRA) takes advantage of the concentric ring structure of broadcast OLAs to limit flooding on the upstream connection. Combination of these two schemes and variations of OLACRA are evaluated in terms of energy savings and probability of successful upstream routing.