Cooperative Vehicle Platoon Intra-communications over Space-Time Correlated Rice fading Channels with co-channel Interference

Abstract

This paper investigates the performance of vehicle platoon intra-communications in the presence of node relaying cooperation. In the proposed scenario, all nodes are allowed to relay the signals of other entities towards the next/final destination. This improves channel conditions by mimicking large scale (virtual) antennas, thereby achieving the concept of cooperative diversity. The scenario considers a platoon of J vehicles assisted by a set of relay nodes. These potential relays include the same vehicles of the platoon, as well as base stations (BSs) and/or road-side units (RSUs). The objective is to evaluate the delay experienced by a packet transmitted by the leader towards all the vehicles of the formation. Each vehicle and each relayingable node is considered to relay the correctly received message to the remaining entities, but most importantly to all the vehicles of the platoon. We consider that if a given transmission attempt is not successfully received by all entities, then the transmitter and relays with a correct copy of the transmission engage in a persistent retransmission scheme that stops only when the packet has been correctly received by all the vehicles. Instantaneous and ideal feedback is used in all calculations. The criterion used to consider a packet correctly received by the destination is that the instantaneous signal-to-interference-plus-noise ratio (SINR) surpasses a reception threshold. It is assumed that the destination nodes store a copy of all the received transmissions over consecutive time slots and antenna elements. These signals are processed using ideal maximum-ratio combining (MRC) to obtain a more reliable copy of the information (i.e. using time and/or retransmission diversity). Multiple antennas are used by all the vehicles and nodes of the network under analysis. Novel spatial and temporal correlation tools are introduced in the channel model with Rice fading statistics and co-channel interference. Results suggest that RSUs can considerably reduce delay of platoons with large numbers of vehicles or large distances between elements. The degree of improvement also depends on channel correlation and the number of co-located antennas.