February 2018 9
OPEN COMMUNICATION ; BY LOU FRENZEL W5LEF
But that’s not all. In the coming years, we will
be seeing new wireless systems incorporated into
every vehicle for improving safety and for aiding in
the implementation of self-driving cars. Some of this
technology has already been defined, but decisions about
what standards to use and when are still up in the air. Here
is an update on this communications technology.
Why Connect Cars?
Why do we want vehicles to speak to one another?
The main reason is to improve safety. Statistics say that
about 35,000 to 40,000 people are killed each year
in auto accidents and millions of others are injured.
The government -- in this case, the National Highway
Transportation Safety Administration (NHTSA) -- believes
that communications between vehicles and other sites can
aid significantly in reducing the death rate and injury level.
Figure 1 illustrates the concept where cars are talking
to one another automatically and to nearby information
sources. Direct car-to-car communications is called vehicle-to-vehicle (V2V). Vehicle to nearby road side units is
referred to as vehicle-to-infrastructure (V2I). A vehicle-to-everything is known as V2X.
With V2V, cars will be able to tell others nearby their
exact location as well as their speed, brake, or turn status
and other factors. The vehicles will also get traffic, road
conditions, weather, and other information via V2I roadside
units or remotely from a V2X network.
With this added information, the driver can make
better decisions. Even automatic actions in Advanced
Driver Assistance Systems (ADAS) can take place,
enhancing the driver’s ability and managing errors. Overall,
safety should be greatly improved.
DSRC is Ready Now
DSRC stands for Dedicated Short Range
Communications. It’s one of the wireless technologies
developed for and approved by the NHTSA. DSRC is a
variant of Wi-Fi designated by its IEEE standard 802.11p.
It operates in 75 MHz of spectrum in the 5.9 GHz
unlicensed band and uses OFDM modulation.
Seven 10 MHz channels have been defined,
and data rates can range from about 3 Mbps to
27 Mbps. The range can be as far as 300 meters
to one kilometer. Figure 2 shows the basic
components of a DSRC system.
The radios transmit a Basic Safety Message
(BSM) ten times a second. It contains the GPS
location, speed, direction, brake status, turn
ars are already loaded with communications technology. AM, FM, and satellite
radios are common, as is a GPS receiver for the navigation system. Some vehicles
also have digital HD radio capability. Then, there is Bluetooth connectivity for
hands-free operation of your phone or for patching your music to the vehicle sound system.
Cellular technology is also common in some newer vehicles; GM’s OnStar is one example.
Embedded Wi-Fi to LTE hot spots is another.
Connected Cars are Coming
Embedded radios promise to improve safety.
Figure 1. Eventually, all vehicles will have some
V2X communications capability. However, V2X
will not work successfully until the majority of
vehicles have it.