Alternating cooperative transmissions for a strip-shaped sensor network

Abstract

We analyze a medium access control (MAC)-free ¿alternating sets¿ transmission strategy for a two-dimensional strip-shaped network. This may be viewed as a broadcast strategy if the entire network has a strip shape, or it may be viewed as a unicast strategy if there is a set of pre-designated cooperators along a conventional multi-hop route, which we refer to as a cooperative route. When there are repeated transmissions, the key advantage of the approach is that it drains the energies of the participating nodes uniformly and in an energy efficient fashion, thereby increasing the network longevity for energy constrained networks. The strategy is based on a very low-overhead form of cooperative diversity called the Opportunistic Large Array (OLA). In the initial transmission, an SNR (¿transmission¿) threshold is used to define mutually exclusive sets of nodes, such that the union of the sets includes all the nodes in the network or cooperative route. Only one of the sets is used for the first transmission. The next transmission uses the next set, and so on. In other words, for two sets, the proposed Alternating OLA with Transmission Threshold (A-OLA-T) basically alternates the transmitting set of nodes (or OLAs) during each transmission cycle. Previously, we analyzed A-OLA-T under the continuum assumption (very high node density) for disc-shaped networks. In this paper, we analyze the performance of the two-set A-OLA-T for strip-shaped networks.