2. With so much in-car infotainment, finding a suitable
means of communication between components is a big
challenge.
Consumers are demanding more and more in-car entertainment in their
vehicles, presenting manufacturers with the challenge of how to deliver
it. There have been innovations like rear seat entertainment packages
that have moved a long way since their appearance as video screens in
headrests, and are becoming increasingly sophisticated.
These days, delivering all this is not just a case of running a few more
wires for extra amplifiers and speakers. The whole
entertainment package including video screens
for DVD display needs to be interfaced with other
aspects of the car’s electronics.
Even modest cars have features that were once
exclusive to the luxury end products. These can
include reversing cameras, satellite navigation and
sensors all of which have to interface seamlessly
with the entertainment systems.
Car manufacturers have universally adopted
the Controller Area Network [CAN] concept that
has many advantages for a car. Predominantly it
reduces the amount of wiring in the vehicle saving
weight and cost. However, CAN is designed to
be low bandwidth limiting its capacity for handling
entertainment data.
Creating a Dialogue
Currently the dominant technology for
infotainment networks is MOST®
, although there
is a growing feeling that a lack of openness is holding back progress. So,
what other alternatives are there for in-car-entertainment networking. For
some time now the Institute of Electrical and Electronic Engineers [IEEE]
has been looking at good old-fashioned Ethernet as used for years on
small computer networks.
The IEEE’s Audio Video Bridging [AVB] task group has been working on
technologies designed to enable the use of this technology. It has now
proposed draft standards that, with minimal changes to existing hardware,
could allow established Ethernet technology to support the automotive
needs of the future.
There are significant challenges associated with
the task. For instance, automotive systems have
to deliver a number of requirements in real time
like indicator alerts or navigation commands. This
can be problematic with a network that relies on
buffering to bridge the gap between packets of
data. Networks can be ‘tuned’ to get around this
problem but that would require a specific design
for each installation.
A solution is the IEEE’s Stream Reservation
Protocol [SRP]. It allows bandwidth to be reserved
so endpoint applications can configure routes
eliminating the need for them to be designed in.
SRP checks that enough bandwidth is available
before transmission of audio-visual data starts.
It then locks down that capacity along the entire
path until that capacity is actively terminated.
It’s All About Timing
Entertainment data does not usually have to be
Talking the Same Language By Robert Boatright, Director, Automotive Networking, Harman International
innovation paper
Speaker A:
2 hops
Speaker B:
4 hops
Audio Processor
An example of the importance of timing
and buffering within the system: Speaker A
buffers audio until Speaker B receives
audio and presentation time is reached.
Graphics by Robert Boatright