Abstract
Future generations of in-vehicle Intelligent Transportation Systems (ITS) will network nearby vehicles for enhanced safety and efficiency. Initially, these intelligent vehicles will utilize wireless communications to extend the perception horizon for individual drivers through warning messages of roadway hazards, including obstacles in the roadway, accidents, and hard-braking incidents. Ultimately, this communication will become a vital part of automated highway systems including cooperative driving and coordinated collision avoidance. For efficiency and cost reasons, the wireless communication is likely to be done directly between vehicles. However, direct inter-vehicle communication (IVC) presents unique security and scalability issues that must be addressed before these systems can be realized.
This dissertation describes a Communication Architecture for Reliable Adaptive Vehicular Ad hoc Networks (CARAVAN) to address these issues. CARAVAN consists of IVC-specific parameterization for the physical layer, as well as protocols for the link and the network layers of the architecture. In the development of CARAVAN, this dissertation makes the following contributions:
1. A study of the characteristics and requirements of the IVC network, elicited through analytical and simulation studies of the network
2. A description of the services needed to support the distribution of the secret spreading codes and the additional scalability requirements that arise from the use of spread spectrum, in order to use spread spectrum to provide protection against denial of Service attacks.
3. A methodology to balance the tradeoffs between radio range, spatial reuse, and multi-hop message delivery
4. A novel mapping function, which maps discrete sections of roadway to timeslots allocated to vehicles that allows for significantly lower latencies for multi-hop transmissions.
5. Novel assignment rules, which specify the timeslots a vehicle is authorized to use, that allow for significantly more efficient use of allocated spectrum.
6. Assignment rules designed to automatically adapt the timeslot allocation to varying densities of vehicle traffic.
7. Forwarding rules at the network layer, including acknowledgement processing, for the delivery of a-periodic messages to all nodes in the zone-of-relevance.
8. A network layer that leverages the benefits of varying radio ranges to reduce the latency in multi-hop message delivery.
Through simulation and analysis, the CARAVAN architecture is shown to present significant and measurable improvement over current IVC architecture proposals.
