Bluetooth!
A New Technology for Transportation?
By Ron Whitelock, Director IMSA Ontario Section
You undoubtedly have a Bluetoothequipped phone; maybe Bluetooth
in your new car. Certainly, a Bluetooth mouse! But where does Bluetooth fit into transportation?
Transportation technology has
originated from many and assorted
sources outside of itself. The traffic
world has always sought out worthy and affordable technology. For
example, radar detectors grew out
of a military invention in WWII;
similarly magnetometers were used
to detection submarines; and let’s
us not forget the video revolution?
And probably the most significant
technology to be embraced by
transportation – the microprocessor.
Within a couple short years after
Intel invented it, microprocessors
began showing up in traffic signal
controllers. And now we have another technology – Bluetooth.
The origin of the name Bluetooth
is interesting. According to Wikipedia, “The word Bluetooth is an
anglicized version of the Scandinavian Blåtand/Blåtann, the epithet
of the tenth-century King Harald I
of Denmark and parts of Norway
who united dissonant Danish tribes
into a single kingdom. The implication is that Bluetooth does the same
with communications protocols,
uniting them into one universal
standard.”
Bluetooth technology is a shortrange wireless standard. Its introduction was to create a ‘cable-less’
short range connection for electronic devices to communicate with
each other. From mobile phones
and headsets; to MP3 players and
car audio systems; to PCs and mice
and printers, Bluetooth technology
allows these devices to connect
without the use of wires.
Created by Ericsson (a Swedish
company!) in 1994, Bluetooth is a
packet-based protocol with a masPage 20
IMSA Jul Aug 11.indd 20
ter-slave structure. One master can
communicate with up to 7 slaves;
all devices share the master’s clock.
Packet exchange is based on the
clock, defined by the master, which
ticks at 312.5 µs intervals. Two clock
ticks make up a slot of 625 µs; two
slots make up a slot pair of 1250 µs.
In the simple case of single-slot packets the master transmits in even slots
and receives in odd slots; the slave,
conversely, receives in even slots
and transmits in odd slots. Packets
may be 1, 3 or 5 slots long but in all
cases the master’s transmission will
begin in even slots and the slave’s
transmission in odd slots.
Some of Bluetooth’s key features
is its robustness, low complexity,
low power and low cost. Designed
to operate in noisy environments,
Bluetooth devices operate in the
unlicensed Industrial, Scientific and
Medical [ISM] band at 2.4GHz, and
avoids interference from other signals by hopping to a new frequency
after transmitting or receiving a
packet.
One unique feature of Bluetooth
devices, which the transportation
industry takes advantage, is that
each radio has a unique MAC [Media Access Control] address.
Mostly unseen beyond the boundaries of the PC World magazine world,
Bluetooth wireless communications
has recently penetrated the traffic
management world.
In the past, it has been a significant
challenge to capture travel time
and origin-destination [O-D] data.
Today, however, with many vehicles
on our road networks carrying Bluetooth devices to connect cell phones
to ear phones, or iPod’s to the car’s
radio system, these devices can be
‘tracked’ via the MAC address as it
travels through our transportation
networks.
Using the unique MAC address,
a device can be identified at one
location with a date/time stamp
then relocated later at another point,
sometime in the future and some
distance away. Compare these two
time values and locations, presto
you have travel time and origindestination information.
Penetration rates (the number of vehicle using Bluetooth) are approximately 6-8% in the US. In Ontario,
where legislation make hands-free
cell phone use mandatory, rates are
over 25%. In most instances, these
penetration rates create enough
‘probes’ to obtain useful data for
many of our transportation applications. So let your imagination
wonder! Professor Bullock did.
In an unique application of this
capability, Professor Darcy Bullock
of Purdue and his team made effective use of this ‘tracking’ capability. They recorded travel time
(and waiting times) as passengers
entered an airport, navigated the
security check and arrived at their
gate.
If you were to conduct an internet
search for ‘Bluetooth + travel time’,
you will discover a new world
of Bluetooth and its applications.
Another small step for transportation!
Something to think about!
Ron Whitelock
Director IMSA Ontario Section
Member EAC
Member Wire and Cable Committee
Comments welcomed. Ron may be
reached at:
[email protected].
IMSA Journal
5/19/11 1:40:43 PM