10 February 2018
status, and other similar information. Nearby vehicles get
the message and send out their own. All the cars within a
given area know where everyone is located and what they
Intelligent software will determine potential conflicts
and generate warnings to the drivers. Some vehicles may
tie the DSRC outputs to the ADAS that may further activate
automatic braking or engage steering control.
DSRC has been around for years, and it has been
tested and approved by the NHTSA. Chips and modules
are for sale because it’s all ready to go. However, only one
model of Cadillac has one installed. The rollout has been
stalled because a competitive technology has been put
forth by several companies.
Called cellular-V2X or just C-V2X, the technology is
based on the current cellular radio standard Long Term
Evolution (LTE). The C-V2X version of LTE permits direct
V2V, a broadcast mode, as well as connections to the
existing cellular networks to access networks that may be
As for specs, C-V2X operates in the same 5. 9 GHz
spectrum and has a similar range and data rate. One
touted feature is a lower latency (delay or response) time
than DSRC. It too will transmit and receive the BSMs and
generate warnings and vehicle action.
C-V2X has not been as widely tested as DSRC.
Nevertheless, it’s a proven wireless standard that should be
more than competitive.
What Technology Wins?
It’s difficult to predict which standard will win the
automotive marketplace. Both will serve the purpose
well. C-V2X has the advantage of being able to use the
existing cellular network infrastructure for V2I and V2X
It’s not clear at this time what standard the auto
manufacturers will adopt.
ADAS and Self-Driving Cars
Fully automated vehicles (AVs) — commonly referred
to as driverless vehicles — actually do drive themselves.
There are various stages of autonomy as shown in the
accompanying Table 1. In the simplest form, AVs are
basically an extension of ADAS that are common on many
ADAS include things like:
y Back-up camera. A dashboard screen really aids when
going in reverse.
y Lane departure warning. Cameras follow the white and
yellow stripes, and signal when you stray.
y Blind spot detection. Detects objects and vehicles on
y Adaptive cruise control. Speed is automatically
adjusted to the prevailing traffic.
y Automatic braking. Activates brakes when objects are
detected; front or back.
Additional ADAS features include:
y Tire pressure monitoring.
y Adaptive lighting. Automatic high beam control and
rotating headlights for curves.
y Driver monitoring. Detects drowsiness or inattention,
All of these features are designed for safety. They help
the driver with warnings, or may actually take control from
the driver when the driver fails to react to a potential crash
ADAS are implemented with a mix of sensors. These
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Figure 2. The major subsystems of a DSRC system
are shown here.