Abstract-In-network data aggregation is a promising communication mechanism to reduce bandwidth requirements of applications in vehicular ad-hoc networks (VANETs). Many aggregation schemes have been proposed, often with varying features. Most aggregation schemes are tailored to specific application scenarios and for specific aggregation operations. Comparative evaluation of different aggregation schemes is therefore difficult. An application centric view of aggregation does also not tap into the potential of cross application aggregation. Generic modeling may help to unlock this potential. We outline a generic modeling approach to enable improved comparability of aggregation schemes and facilitate joint optimization for different applications of aggregation schemes for VANETs. This work outlines the requirements and general concept of a generic modeling approach and identifies open challenges. Vehicular ad-hoc networking (VANET) enables vehicles to communicate with each other on the road. Many applications have been envisioned for this kind of mobile ad-hoc communication. Intersection collision warning, lane merge assistance, smart traffic management, and emergency vehicle warnings are just a few examples of potential applications that promise to enhance road safety, support drivers, or provide infotainment services. Currently, many research projects and field operational trials prepare the deployment of VANET technology in Europe (e.g., CVIS, PRE-DRIVE C2X, simTD), the USA (e.g., VSC, VSC-A), and Japan (e.g., SKY). A major challenge in the deployment of VANETs is the efficient usage of available bandwidth considering the large number of envisioned applications and the even larger number of potential nodes (vehicles and roadside units). Especially the use of multi-hop dissemination of information that is required by some of the applications creates a huge scalability problem. Thus the development of efficient routing and dissemination protocols has been a major research focus [1] . In-network aggregation is a communication paradigm that has the potential to enhance the scalability of multi-hop communication and, by reducing the required bandwidth per application, enable the coexistence of different applications in the same network. Instead of many nodes sending single messages of similar nature, which are all forwarded individually, data items from multiple messages can be combined into one aggregated message that represents the accumulated content of the single messages. Consider for example a traffic jam warning application. A vehicle inside a traffic jam detects it by realizing that it is not moving and that its neighbors are also not moving or only moving at slow speed. Without aggregation, the vehicle now sends a warning message reporting the condition and use geobroadcast to disseminate it to vehicles approaching the traffic jam. Other vehicles in the traffic jam will also start generating such warning messages. This traffic information data needs to be disseminated over multiple hops to be useful for car navigation. Instead of forwarding many messages with similar content and, thereby, congesting the wireless medium, vehicles can aggregate their own view of the current situation with warnings received from other vehicles. Such an aggregated message received by a vehicle further away from the traffic jam could contain the information that the traffic jam is 6 kilometers long, its location, and that it contains 312 vehicles traveling at an average speed of 3.2 km/h. Thus in-network aggregation has many benefits. Mainly bandwidth requirements can be reduced and less resources are required at receiving nodes, because fewer messages need to be processed and evaluated. Reduced processing and communication requirements also imply reduced energy requirements for on-board units. Moreover, aggregation is inherently privacy friendly, because aggregated information cannot be directly linked to individual vehicles and drivers anymore. These benefits are well recognized in the VANET research community (cf. Sec. II). But current aggregation schemes and their aggregation functions are often tailored to specific scenarios and information types. As an advantage, these schemes are presumably optimized to their scenarios and applications. The downside is that it is inherently difficult to compare the performance and accuracy of different aggregation schemes. Furthermore, due to missing standards and high specialization, these aggregation schemes cannot support multiple applications simultaneously, thus limiting the overall beneficial impact of aggregation. We argue that a generic modeling approach for data aggregation in VANETs is required to address these issues and unlock the full potential of in-network aggregation in vehicular networks. Our contribution in this paper is the concept for a modeling framework for aggregation mechanisms that can, in a next step, be used as basis for the design of more generic 2010 IEEE Vehicular Networking Conference 978-1-4244-9525-2/10/$26.00 ©2010 IEEE 78
The work in REF portrayed the requirements and introduced modeling approach and facilitated joint optimization.
On the potential of generic modeling for VANET data aggregation protocols
2010 IEEE Vehicular Networking Conference
2010 IEEE Vehicular Networking Conference
Computer Science