August 01, 2017
无线技术注定要引发汽车行业的变革
By
Avinash Ghirnikar, Director of Technical Marketing of Connectivity Business Group, Marvell
In the early 1980s, Renault made it possible to lock and unlock the doors on its Fuego model utilizing a radio transmitter. Within a decade, other vehicle manufacturers embraced the idea of remote key-less entry and not long after that it became a standard feature.
But the industry swiftly moved to RF technology, in order to make it easier to use. Although each manufacturer favored its own protocol and coding system, they adopted standard low-power RF frequency bands, such as 315 MHz in the US and 433 MHz in Europe. As concerns about theft emerged, they incorporated encryption and other security features to fend off potential attacks. They have further refreshed this technology as new threats appeared, as well as adding features such as proximity detection to remove the need to even press the key-fob remote's button.
With Bluetooth, an app on the user's smartphone can not only unlock the car doors, but also handle tasks such as starting the heater or air-conditioning to make the vehicle comfortable ready for when the driver and passengers actually get in.
Access to the functions located on dashboard through Bluetooth has made it possible for vehicle occupants to hook up their phone handsets easily. Initially, it was to support legal phone calls through hands-free operation without forcing the owner to buy and install a permanent phone in the vehicle itself. But the wireless connection is just as good at relaying high-quality audio so that the passengers can listen to their favorite music (stored on portable devices). We have clearly move a long way from the CD auto-changer located in the trunk. Bluetooth is a prime example of the way in which RF technology, once in place, can support many different applications - with plenty of potential for use cases that have not yet been considered. Through use of a suitable relay device in the car, Bluetooth also provides the means by which to send vehicle diagnostics information to relevant smartphone apps.
Wi-Fi is able to provide a more robust data pipe, thus enabling even richer applications and a tighter integration with smartphone handsets. One use case that seems destined to change the cockpit experience for users is the emergence of screen projection technologies. Through the introduction of such mechanisms it will be possible to create a seamless transition for drivers from their smartphones to their cars.
If a pothole opens up or cars have to break suddenly to avoid an obstacle, they can send out wireless messages to nearby vehicles to let them know about the situation.
IEEE 802.11p Wireless Access in Vehicular Environments (WAVE) operates in the 5.9 GHz region of the RF spectrum, and is capable of supporting data rates of up to 27 Mbit/s. One of the key additions for transportation is scheduling feature that let vehicles share access to wireless channels based on time.
On a freeway, the relative velocity of an approaching transmitter can exceed 150 mph. Such a transmitter may be in range for only a few seconds at most, making ultra-low latency crucial.
Traffic signals, for example, can let vehicles know when they are likely to change state. Vehicles leaving the junction can relay that data to approaching cars, which may slow down in response. By slowing down, they avoid the need to stop at a red signal - and thereby cross just as it is turning to green. The overall effect is a significant saving in fuel, as well as less wear and tear on the brakes. In the future, such wireless-enabled signals will make it possible improve the flow of autonomous vehicles considerably.
Pedestrians and cyclists may signal their presence on the road with the help of their own Bluetooth devices. The messages picked up by passing vehicles can be relayed using V2V communications over WAVE to extend the range of the warnings. Roadside beacons using Bluetooth technology can pass on information about local points of interest - and this can be provide to passengers who can subsequently look up more details on the Internet using the vehicle's built-in Wi-Fi hotspot.
