Power Allocation and Self-Scheduling for Cooperative Transmission Using Opportunistic Large Arrays

This paper introduces methods for broadcasting and upstream routing in ad hoc networks that use a form of cooperative diversity called opportunistic large arrays (OLAs). By "limiting the flood," each method saves more than half the energy compared to OLA-flooding, without requiring GPS, individual node addressing, or inter-node interaction. OLAs form in "levels," and we present a simple, distributed way for a node to learn its level. In the broadcast method, called OLA-T, a node compares its received power to a prescribed threshold to decide if it should forward. A more energy-efficient variation, OLA-VT, optimizes the thresholds as a function of level. The upstream routing method applies to the wireless sensor network topology. The OLA concentric routing algorithm (OLACRA) exploits the concentric shapes of the OLAs to guide the message upstream to the collection node. Enhancements to OLACRA are considered to further improve energy savings and reliability.