Safer driving — and safer self-driving — call for car-to-car communications with no lag. Will it be cellular or dedicated short-range communications (DSRC)? Cellular chip supplier Qualcomm just announced a chip that will do both, bridging the two. Cellular telematics could get information that’s not time-critical, while DSRC would send and receive info directly from nearby cars about speed, slippery roads, sudden braking, and cars running stop signs or red lights.
The Qualcomm Technologies 9150 C-V2X cellular vehicle-to-everything (V2X) chip will be available to automakers in sampling quantities in the second half of 2018, along with a reference design to help automakers speed the system into production. The chip integrates the DSRC radio; cellular would be handed off to the car’s telematics system.
Why the Need for Cellular and/or DSRC
Ninety-five percent of automobile fatalities are attributed to driver error. (The remainder would be a catastrophic failure of a car component or, say, a tree falling on an occupied car in a storm.) If nearby cars can communicate their status, the cellular and/or V2X systems can alert the driver and respond. If the car immediately ahead starts to skid, brake heavily, or switch from an adjacent lane without looking, the V2X-equipped car could alert the driver and then take some action, such as pre-charging the brakes and then braking briskly, if both DSRC or rear-facing radar shows no car tailgating you.
There has been talk of cellular-t0-cellular communication without V2X, because telematics is already on a healthy minority of cars. Virtually every GM car now on the road has OnStar telematics, although it’s not clear existing cars could be modded to get useful alerts via the cellular system. Cellular also has a lag — hysteresis — because it goes from car to cell tower to other cars.
V2X communicates directly with nearby cars. That includes V2V, or vehicle-to-vehicle; V2I, or vehicle-to-infrastructure; and V2P, or vehicle-to-pedestrian (via phone). The traffic signal tells cars when the light is changing and in which direction; a portable V2I transceiver would warn of a closed lane for construction. A fully mobile unit might travel in a police car and warn of an accident blocking the right lane and shoulder on the northbound side of the highway.
DSRC Can Be Via Cellular, Dedicated Radio, or Both
Last year, I test drove the Audi Traffic Light Information V2I (vehicle-to-infrastructure) system via cellular modem. The car received information on when traffic lights were about to change to red and later back to green. I found the countdown timer accurate to within about a second. When going to green, Audi deliberately did not count down the last several seconds visually, because drivers might try to tromp the throttle immediately and collect a red light-runner. If the information via cellular was delayed by a couple hundred milliseconds — there was no indication it was — it wouldn’t have been safety-critical.
I also drove, early this year, at a V2X demo in Washington. It was a government-run event and lacked the slickness of the Audi demo. But the alerts came through clearly and quickly as we snaked among traffic barricades dropped off at RFK Stadium after the inauguration. The scenarios included a lane closure because of construction, a red light, and a lane curve (slow-down) warning. These were only alerts, but in a production car they could also slow the vehicle, provided it had clear information on which lanes were closed, or that the light was now red and you risked a traffic citation.
DSRC may be a key factor in safe autonomous driving. Prototype cars rely on radar, optical, and lidar sensors to locate other cars as well as road edges and obstructions. If cars constantly send out, via DSRC, their position, speed, and rate of acceleration or deceleration, that may enable self-driving with more confidence in rain, snow, or heavy fog.
What Qualcomm Brings to the Party
Qualcomm’s involvement gives DSRC further legitimacy. It promotes development of dedicated short-range communications along both cellular and the 5.9 GHz radio band. Integration of the radio will help bring costs down faster, enough so that cellular-only DSRC may be just a short-term solution.
The 5.9 GHz radio would be superior for fastest transmission of time-critical events, such as the car ahead braking hard, skidding, or running a red light. In heavy rain or fog, it could report cars just ahead and which lane they’re in, so you’d be careful coming up too fast. (Some would argue this would encourage driving closer to the limits in low-visibility conditions.) Cellular would provide more range and warn of events farther ahead, such as a bridge out, a car pulled over on the shoulder, or the precise location of an accident that happened a minute before.
In some minds, DSRC might let a large vehicle (an 18-wheeler) signal a car behind when it’s safe to pass on a two-lane road, or it might not, since the car ahead might have legal liability if there wasn’t enough room for safe passing.