# Moving Ad Hoc Networks--A Comparative Study
## 3 Vehicular Ad-Hoc Networks (VANET)
* Although the rapid movement of vehicle nodes poses serious challenges to the onboard self-organizing network because vehicles are always driving on the road, the movement of the vehicle nodes is regular, such that the topology changes of the nodes are regular and predictable. Figure 6: VANET Architecture. Vehicle self-organizing networks have abundant external auxiliary equipment. The vehicle-mounted Global Positioning System (GPS) can provide VANET with accurate timing and vehicle location information. The use of electronic maps brings convenience to the VANET networking and routing protocol design. Various functional sensors can be installed on the vehicle to collect the speed, acceleration, direction, and other status information of the vehicle node. * The communication module in the general MANET is powered by a battery; as such energy saving becomes a key consideration in the protocol design process. In the on-vehicle ad hoc network, the vehicle itself provides power for various devices, which reduces the energy consumption and device volume requirements of the communication equipment. The numerous applications are defined by the emerging VANET technologies for driver assistance, efficient traffic, and safety, etc. In VANET (both Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I)) several potential applications are available. Based on safety-related applications (safety-related and non-safety-related) or on communication methods (Vehicle-to-Vehicle, and Vehicle-to-RSU) the following applications are being considered. * Safety: For the reduction of injuries, saving lives, and the reduction of the number of accidents, VANET technologies are applied. These include collision warnings, accident warnings, lane departure warnings, obstacle detection, vehicle breakdown, work zone warnings, and so on. * Periodic Messages: Information which is related to vehicles, such as position, speed, and direction, is to be known by the vehicles from another environment for decision-making, to try to avoid a hazardous situation occurring. Thus, the periodic messages are said to be an important message type that supports the decision that can be taken in safety applications; therefore, it might direct it to an unwanted consumption of bandwidth, especially in vast surroundings, to increase the probability of a storm problem occurring. * Event-Driven Messages: These messages are only sent when a dangerous situation occurs. Otherwise, they will not be sent. Event-based messages are likely to take a higher priority. The main problem with these letters is the increased guarantee of message delivery to all known vehicles. * Entertainment/Information Applications: One unsafe application, also known as an information/entertainment application, is to provide drivers with a comfortable ride by using traffic efficiency. Examples include explaining a restaurant menu and its prices, providing passengers with information to find the nearest gas station that provides information about the current weather conditions in a particular area, providing information about available parking spaces in the nearest parking lot,  
Figure 7: Characteristics of VANET. providing seamless access to internet service facilities while traveling, and providing games for online occupants, coupling/decapper tools, payment for parking, Electronic Toll Collection (ETC) and workshop communications. * Traffic Efficiency: VANET technology can play an important role in improving flow efficiency and reducing flow congestion. Examples include electronic toll collection, traffic management, cooperative adaptive cruise control, and traffic jam-related information, etc. * Driver Assistance: The provision of good communications and accurate data to vehicles for improving security, privacy, and safety [16] can be performed by VANET. Examples include parking information, digital road map downloading, automatic emergency calls, real-time traffic information, a navigation system and various warning information, etc [17,18]. * Routing protocols used in VANET.