Faster Information Propagation on Highways: a Virtual MIMO Approach

In vehicular communications, traffic-related information should be spread over the network as quickly as possible to maintain a safe and reliable transportation system. This motivates us to develop more efficient information propagation schemes. In this paper, we propose a novel cluster-based cooperative information forwarding scheme, in which the vehicles opportunistically form virtual antenna arrays to boost one-hop transmission range and therefore accelerate information propagation along the highway. Both closed-form results of the transmission range gain and the improved Information Propagation Speed (IPS) are derived and verified by simulations. It is observed that the proposed scheme demonstrates the most significant IPS gain in moderate traffic scenarios, whereas too dense or too sparse vehicle density results in less gain. Moreover, it is also shown that increased mobility offers more contact opportunities and thus facilitates information propagation.Comment: IEEE 2014 Global Telecommunications Conference (GLOBECOM 2014) - Communication Theory Symposiu

Impact of Asymmetric Traffic Densities on Delay Tolerant Vehicular Ad Hoc Networks

Vehicular networking can be achieved with short, medium, or long-range communication technologies. However, there are trade-offs in the adoption of these technologies including data capacity, continuity of connections, energy use and contention with other users. We focus on short range technologies that support both near-neighbor communication, for safety applications, and multihop communications for message propagation. Due to frequent network partitioning, opportunistic message exchange is required for message propagation. Earlier studies reveal that messages are suitably propagated in both directions of traffic as vehicle traffic density increases. In this paper we consider asymmetries in traffic density caused by directionality. For example, ‘rush hour ’ traffic fills one direction of a roadway while the other direction can be sparse. Performance analysis indicates that data dissemination under asymmetry produces a corresponding asymmetry in message propagation in the direction of higher-density traffic. This result is framed in the context of traffic density regimes and is useful in the design of vehicular networks that leverage short range communications. For a fixed traffic density in one direction, an increase in density from 0 to 20 vehicles/km in the other direction, yields a corresponding increase of 500 m/s to 1000 m/s in the messaging performance depending upon the regime