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 communication 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 the 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.
Contents
LIST OF TABLES..........................................................................................................IV
LIST OF FIGURES.........................................................................................................V
ACKNOWLEDGEMENTS...........................................................................................IX
ABSTRACT......................................................................................................................X
LIST OF ACRONYMS..................................................................................................XI
1 MEETING THE CHALLENGES OF INTER-VEHICLE COMMUNICATION
1
1.1 CHALLENGES OF MOBILE AD HOC WIRELESS NETWORKS...................................4
1.2 ADDITIONAL REQUIREMENTS OF IVC NETWORKS...............................................6
1.3 MEETING THESE CHALLENGES WITH CARAVAN...............................................7
2 LITERATURE REVIEW AND CARAVAN PREREQUISITES.........................9
2.1 OVERVIEW OF INTER-VEHICLE COMMUNICATION...............................................9
2.2 OVERVIEW OF IVC-SUPPORTED FUNCTIONS......................................................12
2.3 INTELLIGENT HIGHWAY OVERVIEW...................................................................14
2.3.1 Intelligent Highway Entities.....................................................................18
2.3.2 Data Flow.................................................................................................25
2.4 COMMUNICATIONS ARCHITECTURE...................................................................26
2.4.1 OSI Reference Model................................................................................26
2.4.2 Advantages of a Layered Architecture......................................................29
2.5 IVC AND COMPUTER SECURITY.........................................................................30
2.5.1 Availability Threats to Vehicular Communication Networks...................31
2.5.2 Integrity Threats to Vehicular Communication Networks........................33
2.5.3 CARAVAN Security Services and Mechanisms.........................................34
2.6 NETWORK MODEL.............................................................................................36
2.6.1 Unit Disk Graphs......................................................................................37
2.6.2 Graph Theory Concepts............................................................................38
2.6.3 Mobility Model..........................................................................................40
2.6.4 The Wireless Network Model and CARAVAN..........................................42
2.7 PHYSICAL LAYER...............................................................................................43
2.8 LINK LAYER PROTOCOLS...................................................................................44
2.8.1 Link Layer Challenges and Functionality.................................................45
2.8.2 First-Come, First-Served Approach.........................................................47
2.8.3 Pre-Allocated Approach...........................................................................50
2.9 NETWORK LAYER..............................................................................................52
2.9.1 Virtual Network Backbones......................................................................54
2.9.2 CARAVAN
