Opportunistic large arrays: Cooperative transmission in wireless multihop ad hoc networks to reach far distances

The technique we propose in this paper allows efficient flooding of a wireless network with information from a source, which we refer to as the leader. At the same time, it permits us to transmit reliably to far destinations that the individual nodes are not able to reach without consuming rapidly their own battery resources, even when using multihop links (the reach-back problem). The synchronization constraints are extremely loose and can be fulfilled in a distributed manner. The key idea is to have the nodes simply echo the leader's transmission operating as active scatterers while using adaptive receivers that acquire the equivalent network signatures corresponding to the echoed symbols. The active nodes in the network operate either as regenerative or nonregenerative relays. The intuition is that each of the waveforms will be enhanced by the accumulation of power due to the aggregate transmission of all the nodes while, if kept properly under control, the random errors or the receiver noise that propagate together with the useful signals will cause limited deterioration in the performance. The avalanche of signals triggered by the network leaders form the so-called opportunistic large array (OLA). The main advantages of the OLA are its great flexibility and scalability.