Vehicular Communications (VANET)

At present cars and other private vehicles are used daily by many peoples. The biggest problem regarding the increased use of private transport is the increasing number of fatalities that occur due to accidents on the roads; the expense and related dangers have been recognized as a serious problem being confronted by modern society. VANET provides wireless communication between moving vehicles, using a dedicated short-range communication (DSRC). DSRC is essentially IEEE 802.11a amended for the low overhead operation to 802.11p; the IEEE then standardizes the whole communication stack by the 1609 family of standards referring to wireless access in vehicular environments (WAVE). The vehicle can communicate with other vehicles, directly forming vehicle to vehicle communication (V2V), or communicate with fixed equipment next to the road, referred to as roadside unit (RSU), forming vehicle to infrastructure communication (V2I)

These communications allow vehicles to share different kinds of information like safety information for the purpose of accident prevention, post-accident investigation or traffic jams. Other types of information can be disseminated, like traveller related information, which is considered as non-safety information. The intention behind distributing and sharing the information is to provide a safety message to warn drivers about expected hazards. This helps in decreasing the number of accidents and to provide passengers with pleasant journeys.

VANET architecture

The communication between vehicles or between a vehicle and an RSU is achieved through a wireless medium called WAVE. This method of communication provides a wide range of information to drivers and travellers and enables safety applications to enhance road safety and provide comfortable driving. The main system components are the application unit (AU), OBU and RSU. Typically the RSU hosts an application that provides services, and the OBU is a peer device that uses the services provided. The application may reside in the RSU or the OBU, and the device that hosts the application is called the provider, and the device using the application is described as the user. Each vehicle is equipped with an OBU and a set of sensors to collect and process the information. Then send it on as a message to other vehicles or RSUs through the wireless medium; it also carries a single or multiple AU that uses the applications provided by the provider using OBU connection capabilities. The RSU can also connect to the Internet or to another server which allows AU’s from multiple vehicles to connect to the Internet

OnBoard unit (OBU)

An OBU is a wave device usually mounted on-board a vehicle used for exchanging information with RSUs or with other OBUs. It consists of a resource command processor (RCP) and the resources which includes a read/write memory used to store and retrieve information, a user interface, a specialized interface to connect to other OBUs and a network device for short-range wireless communication based on IEEE 802.11p radio technology. It may include another network device for non-safety applications based on other radio technologies such as IEEE 802.11a/b/g/n. The OBU connects to the RSU or other OBUs through a wireless link based on the IEEE 802.11p radio frequency channel, and is responsible for the communications with other OBUs or with RSUs; it also provides communication services to the AU and forwards data on behalf of other OBUs on the network. The main functions of the OBU are wireless radio access, ad hoc and geographical routing, network congestion control, reliable message transfer, data security and IP mobility.

Application unit (AU)

The AU is the device equipped within the vehicle that uses the applications provided by the provider using the communication capabilities of the OBU. The AU can be a dedicated device for safety applications or a normal device such as a personal digital assistant (PDA). To run the Internet, the AU can be connected to the OBU through a wired or wireless connection and may reside with the OBU in a single physical unit; the distinction between the AU and the OBU is logical. The AU communicates with the network solely via the OBU, which takes responsibility for all mobility and networking functions.

Roadside unit (RSU)

The RSU is a wave device usually fixed along the roadside or in dedicated locations, such as junctions or near parking spaces. The RSU is equipped with one network device for a dedicated short-range communication based on IEEE 802.11p radio technology and can also be equipped with other network devices so as to be used for the purpose of communication within the infrastructural network

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