A simple cooperative transmission protocol for energy-efficient broadcasting over multi-hop wireless networks

Abstract: This paper analyzes a broadcasting technique for wireless multi-hop sensor networks that uses a form of cooperative diversity called opportunistic large arrays (OLAs). We propose a method for autonomous scheduling of the nodes, which limits the nodes that relay and saves as much as 32 % of the transmit energy com-pared to other broadcast approaches, without requiring global po-sitioning system (GPS), individual node addressing, or inter-node interaction. This energy-saving is a result of cross-layer interac-tion, in the sense that the medium access control (MAC) and rout-ing functions are partially executed in the physical (PHY) layer. Our proposed method is called OLA with a transmission threshold (OLA-T), where a node compares its received power to a thresh-old to decide if it should forward. We also investigate OLA with variable threshold (OLA-VT), which optimizes the thresholds as a function of level. OLA-T and OLA-VT are compared with OLA broadcasting without a transmission threshold, each in their min-imum energy configuration, using an analytical method under the orthogonal and continuum assumptions. The trade-off between the number of OLA levels (or hops) required to achieve successful net-work broadcast and transmission energy saved is investigated. The results based on the analytical assumptions are confirmed with Monte Carlo simulations