IEEE 802.11p

IEEE 802.11p is an approved amendment to the IEEE 802.11 standard to add wireless access in vehicular environments (WAVE), a vehicular communication system. It defines enhancements to 802.11 (the basis of products marketed as Wi-Fi) required to support Intelligent Transportation Systems (ITS) applications. This includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure, so called V2X communication, in the licensed ITS band of 5.9 GHz (5.85-5.925 GHz). IEEE 1609 is a higher layer standard based on the IEEE 802.11p. It is also the base of a European standard for vehicular communication known as ETSI ITS-G5.

At some point, 802.11p was considered for dedicated short-range communications (DSRC), a U.S. Department of Transportation project based on the Communications access for land mobiles (CALM) architecture of the International Organization for Standardization for vehicle-based communication networks, particularly for applications such as toll collection, vehicle safety services, and commerce transactions via cars. The ultimate vision was a nationwide network that enables communications between vehicles and roadside access points or other vehicles. This work built on its predecessor ASTM E2213-03 from ASTM International.

In Europe, 802.11p was used as a basis for the ITS-G5 standard, supporting the GeoNetworking protocol for vehicle to vehicle and vehicle to infrastructure communication. ITS G5 and GeoNetworking is being standardised by the European Telecommunications Standards Institute group for Intelligent Transport Systems.

As the communication link between the vehicles and the roadside infrastructure might exist for only a short amount of time, the IEEE 802.11p amendment defines a way to exchange data through that link without the need to establish a basic service set (BSS), and thus, without the need to wait for the association and authentication procedures to complete before exchanging data. For that purpose, IEEE 802.11p enabled stations use the wildcard BSSID (a value of all 1s) in the header of the frames they exchange, and may start sending and receiving data frames as soon as they arrive on the communication channel.

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