Read more on www.harmaninnovation.com With so much in-car infotainment, here's how to find a suitable means of communication between components.

1. innovation paper
HarmanInnovation.com
© 2014 Harman International, Inc.
Talking the Same Language

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

3. in strict real time so the established practice
of buffering allows music or video feeds
to be displayed uninterrupted even when
sufficient bandwidth is not always available
on the network. But to make it work across
a complex car entertainment system it
needs some form of time signature. This
allows precise data synchronization to
be achieved, for instance when sending
packets of data to different devices like the
front and rear audio outputs. By having
a strict time code on each piece of information, they can be played at
precisely the right time in relation to each other.
To achieve this the IEEE has developed its own Precision Time Protocol
[PTP] that provides a common time reference to all nodes on the network.
It automatically selects a device to be the master clock that then shares its
time with the other devices.
Some data, however, cannot be buffered and has to arrive strictly
on time with no delay. For this the IEEE has developed a Queuing and
Forwarding protocol [Qav]. It ensures time-sensitive data is scheduled
to travel across the network arriving in time to avoid any delay. This
overcomes one of the biggest hurdles of Ethernet, that being a delay
in data transmission at times of high network traffic. The scheduling
prioritizes streams like driver assist camera feeds or Bluetooth
microphones over data that can be buffered like entertainment streams.
Where an Ethernet-based AVB network differs from one using the
MOST®
protocol is in its bandwidth utilization. MOST shares the total
network bandwidth across all the connected devices. However, AVB
networks only use bandwidth between the source and destination
allowing for more data to be handled across the network.
The Way Forward
These technologies from the IEEE have provided vital missing links
to allow Ethernet to be used in
vehicles to provide reliable audio
and video. It now believes that if
a number of hardware suppliers
adopt them then Tier-1 suppliers
will have a wealth of choices to
provide the next generation of in car
entertainment electronics.
Harman, being a founding
member, is a strong proponent
of AVB. It believes that for the
individual companies to succeed, there needs to be an alliance like AVnu
that works across the industry providing compliance and interoperability.
Otherwise each company is trying to do this on their own with the
inevitable resulting incompatibility. This, Harman believes, would not be
good for anyone in the automotive industry.
innovation paper / Talking the Same Language
Keywords: communication, entertainment, ethernet, Precision Time Protocol, auto
infotainment, automotive infotainment systems, infotainment auto
Get more automotive infotainment insights at Harman Innovation Hub.
Robert Boatright has been with Harman for 14 years and currently holds the position
of Chief Engineer for Harman International’s CTO office. Recently, he served as Director
of Automotive Networking where he focused on putting Ethernet AVB into high-volume
production. As Director of Harman’s Corporate Technology Group, he was intimately
involved with Ethernet AVB since its inception and founded and chaired IEEE 1722 and
IEEE 1733 working groups, was vice-chair of IEEE 1722.1 working group, and was
instrumental in the founding of the AVnu Alliance.
HARMAN (www.harman.com) designs, manufactures, and markets a wide range of
infotainment and audio solutions for the automotive, consumer, and professional markets. It
is a recognized world leader across its customer segments with premium brands including
AKG®
, Harman Kardon®
, Infinity®
, JBL®
, Lexicon®
, and Mark Levinson®
and leading-edge
connectivity, safety and audio technologies. The Company is admired by audiophiles
across multiple generations and supports leading professional entertainers and the venues
where they perform. More than 25 million automobiles on the road today are equipped with
HARMAN audio and infotainment systems.
© 2014 HARMAN International Industries Incorporated. All rights reserved.
Currently the dominant
technology for infotainment
networks is MOST
®
, although
there is a growing feeling that
a lack of openness is holding
back progress.