In many applications involving safety .either as warning systems or as a trigger for autonomousintervention in urban traffic and intersections, highway traffic (6+ lanes), large Freeways, and moderately congested parking lots .standard DSRC/WAVE-based V2V will not reliably support systems such as collision warning and active collision avoidance by itself.

+Since BSMsare broadcast the issue is not an explosion of communications, rather that more than ~200 radioscommunicating according to the DSRC/WAVE communications protocol will result in significant congestion in theradio.s Control Channel

+The effective delay caused by that congestion appears to grow exponentially with the number of radios sendingand receiving BSMs.

+Unfortunately, there are common traffic scenarios that might easily be populated by enough radios to cause exponential growth in critical delays. This seriously undermines the applicability of DSRC/WAVE in vehicle and traffic safety.


Given the requirement for active safety devices to operate correctly and reliably across a broad range of conditions and traffic situations, standard DSRC/WAVE V2V appears to be not robust enough to be thesingle communications or detection technology to support vehicle and traffic safety.



Urmson, who is the tech lead for the project, said that the "heart of our system" is a laser range finder mounted on the roof of the car. The device, a Velodyne 64-beam laser, generates a detailed 3D map of the environment. The car then combines the laser measurements with high-resolution maps of the world, producing different types of data models that allow it to drive itself while avoiding obstacles and respecting traffic laws.

The vehicle also carries other sensors, which include: four radars, mounted on the front and rear bumpers, that allow the car to "see" far enough to be able to deal with fast traffic on freeways; a camera, positioned near the rear-view mirror, that detects traffic lights; and a GPS, inertial measurement unit, and wheel encoder, that determine the vehicle's location and keep track of its movements.



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 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 uses 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.

Because such stations are neither associated nor authenticated, the authentication and data confidentiality mechanisms provided by the IEEE 802.11 standard (and its amendments) cannot be used. These kinds of functionality must then be provided by higher network layers.

Use of the 5.9GHz band

The IEEE 802.11p amendment allows the use of the 5.9GHz band (5.850-5.925 GHz) with 5MHz, 10MHz and 20MHz channel spacings, and specifies the requirements for using this band in the United States and in Europe.

When WiFi Will Drive - article


Some analysts see major hurdles, however. In the first place there is the money, or lack thereof. While Wi-Fi components may not be terribly expensive, large-scale public networks could put new pressures on already strained civic budgets, notes Julie Ask, senior analyst at Jupiter Research. The cost savings inherent in reducing congestion and saving lives "probably doesn't pay for this," she said. To make these uses financial feasible, she suggested, government might need to compete with the private sector, perhaps by selling commercial or residential access on the same networks.

Most 2014 GM cars will also be a Wi-Fi hotspot


Feb. 25, 2013 at 2:07 PM ET

General Motors will partner with AT&T to offer embedded 4G Internet access in .most. of the vehicles it sells in the U.S. and Canada starting next year, the maker announced during a mobile communications conference in Spain on Monday.