Opportunistic large array concentric routing algorithm (OLACRA) for upstream routing in wireless sensor networks

An opportunistic large array (OLA) is a form of cooperative diversity in which a large group of 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 transmit energy than conventional multi-hop protocols during broadcasting. The OLA concentric routing algorithm (OLACRA) and its variants, the main contributions of this paper, leverage the concentric ring structure of the OLAs during the initialization phase to limit the node participation on the upstream connection. For the simulation scenarios considered in this paper, OLACRA is shown to save over 80% of the transmit energy relative to other OLA-based schemes. This paper analyzes the performance of OLACRA over ‘deterministic channels’ or non-faded orthogonal channels and on ‘diversity’ or Rayleigh flat-fading channels with limited orthogonality. Enhancements to OLACRA to further improve its energy efficiency by limited broadcasting in the initial upstream level and limiting the downlink ‘step-sizes’ are also considered. A simple contention avoidance scheme for WSNs with multiple flows is also proposed. In addition to this, the robustness of OLACRA over mobile channels is also studied. The protocols are tested using Monte Carlo evaluation.