Analysis of spatial pipelining in Opportunistic Large Array broadcasts

The Opportunistic Large Array (OLA) is a simple form of cooperative transmission, in which a group of single-antenna nodes decode the same packet, then a short time later relay the packet simultaneously in orthogonal channels. The authors have previously shown that OLA transmissions can be adequately synchronized so they appear to a receiver as having come from a real array antenna doing transmit diversity. OLAs have been considered as a basis for rapid single-packet broadcasting in multi-hop networks, however, there are few studies that consider the long range, intra-flow interference produced by OLAs transmitting previous packets from the same source. We show that the broadcast throughput from a single source is always degraded if the source transmits a packet before previous co-channel packets have finished propagating across the network. The infinite disc case is treated theoretically, while the finite disc case is treated numerically.