Cooperative Unicasting in Large Wireless Networks

Abstract

This paper investigates the potential gains of half-duplex unicast strategies in a large wireless network consisting of clusters in which a source node attempts to transmit a message with the aid of other inactive -potential relays- nodes within the cluster. The network is modeled as an independently marked Poisson point process and a slow-fading scenario is considered. A two-phase transmission protocol is studied and an achievable (upper) bound on the asymptotic error probability of any cluster in the network is derived in terms of the outage probability (OP). The proposed scheme takes advantage of the spatial distribution of the cooperating nodes to create a distributed virtual antenna array, thus improving the OP over direct transmission (DT) through cooperative diversity. Finally, we obtain a converse (lower) bound on the OP of any unicast strategy when restricting all admissible protocols to belong to the same -still quite general- class of half-duplex codes that includes the one studied.