1. Who use LinkQuest's
underwater acoustic modems?
LinkQuest's modems are used by major
offshore oil companies, commercial survey companies, government
agencies, universities and naval defense contractors. Users
GEOS, Fugro Chance, Simrad, Boeing, Oceaneering,
BP, Shell, ExxonMobil, Total, C&C Technologies, Mitsubishi,
Onyx Special Services, NOAA PMEL, NOAA AOML, NOAA NOS, NOAA National Data Buoy Center,
Canada, Japan Marine Safety
Marine Science and Technology Center, Woods
Hole Oceanographic Institution,
Marine Lab (UK), CEFAS (UK),
Institute of Marine
Research (Norway), ENEA (Italy), Australian
Institute of Marine Science,
The University of Maryland, Virginia Institute of Marine Science,
National University of Singapore, US Navy Naval Oceanographic
Navy NUWC (Naval Undersea Warfare Center) Keyport, US Navy
Coastal Systems Station, The
kind of environments have LinkQuest's
acoustic modems been used in?
underwater acoustic modems have been used very extensively in
deepwater and costal oceans, bays, harbors, lakes and rivers all
over the world. All models perform
well in near-vertical and horizontal environments. These modems have
been used extensively in horizontal environments for AUV command and
control, remote control of undersea sensors and environmental
monitoring. The UWM3000H and UWM2000H modems, tailored for long-range shallow and very-shallow water environments, perform particularly well in environments with very harsh multi-paths (acoustic signals reflected from surface, bottom and other boundaries). Field tests and customer deployments show these systems can achieve reliable communication with bit error rate of less than 10
in very shallow water, immune from the impact of very harsh multi-paths. Examples are communication in costal ocean up to 3000 meters of range at 5 meters of water depth using UWM3000H modems and communication in San Diego bay up to 1000 meters of range at 5 to 10 meters of water depth using UWM2000H modems.
3. What kind of technology
is used in the modem communication?
LinkQuest uses advanced broadband
spread spectrum technologies in its underwater acoustic modems.
The patent pending technologies are invented by its in-house
communication experts under intensive R&D. The technologies
combine the modern wireless and high speed digital communication such
as DSL with broadband underwater acoustics. The results are the
phenomenally improved reliability, data rate and user friendliness.
4. How can
LinkQuest assist customers in field deployment?
utmost pride in making systems friendly to end users and robust in
typical field deployments. Vast majority of our customers have no need
to contact LinkQuest for any after-sale support.
In order to assist field deployments when needed, LinkQuest has
implemented comprehensive test tools to collect and analyze field
data. Information such as channel conditions, noise conditions of the
surface and bottom modems, signal strengths of both modems and signal
spectrum can be easily obtained by running a few software utilities.
LinkQuest has used these tools to pin point problems such as faulty
radio modem and faulty installation caused by strong wave in
One of the software utilities in the modem even provides the range
between the modems. This effectively makes each modem a ranging
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5. Is there any need to
modify the existing software of the underwater instruments to work
with LinkQuest’s modems?
forms a completely transparent RS-232 connection between two end
equipment as if they directly connected through an RS-232
cable. As long as the user is able to set the RS-232
configuration of the instrument/application software to 9600 baud, 1
start bit, 1 stop bit, no parity bit and no flow control there is no
need to modify the instrument software. For example, LinkQuest’s
modems has been integrated seamlessly with some popular Doppler
Current Profilers and CTDs.
How many instruments
acoustic modem interface to?
With the Data Fusion option, a modem can
interface to 8 instruments using RS232 interface and sample up to 16
analog inputs simultaneously. A modem can also provide up to 1
Gbytes of permanent storage on a compact flash disk.
what is the payload data rate?
The payload data rate
is the user information data rate. With the additional 1 start
bit, 1 stop bit of the RS-232 interface and modem protocol overhead,
the RS-232 data rate becomes 9600 bits/sec. Before transmission the
RS-232 data is further modulated and coded, and the resulting acoustic
data rate is 17.8k bits/sec.
What does it mean by a bit error
rate of less than 10?
A bit error rate of
10 means there is only one bit error in 10 million user information
bits. LinkQuest's modems provides unprecedented high quality
communication for underwater environment. The quality of the
communication is similar to the quality of the modems used with
your home computer.
How does the modem deal with noisy
proprietary modulation and equalization scheme allows the modems to
work under very low SNR. LinkQuest’s modems also employ automatic
rate adaptation algorithm which reduces the data rate to 1200 baud
payload data rate when excessive noise is present. Once the noise
level is lowered, the modems automatically restores to high data rate
Do the modems utilize coded
modems utilized advanced coded communication and other error
correction methods to improve robustness through greater
signal-to-noise ratio and to achieve bit error rate of less than 10.
For purposes of fair comparison with other company’s modems, please
be sure to compare our data rate with other company modem’s highest
data rate with coded communication and be sure to ask what kind of bit
error rate is guaranteed.
Can one modem communicate with
Yes. One surface
modem can communicate with up to 25 underwater modems in a deployment.
Each modem can be configured with a unique address. For certain
models, one surface modem can communicate with up to 255 underwater
How much power is required to
transmit 1 megabytes of data?
modem takes only 20 minutes and as little as 0.3 watt-hour (3% of a
"D" cell battery) to collect 1 megabytes of data. Our UWM2000
modem takes 20 minutes and 1.2 watt-hour (12% of a "D" cell
battery) to collect the same amount of data. In other words, a
"D" cell battery is capable of transmitting 10 to 40
megabytes of data.
Does the modems have internal
The modem’s power
can be provided by the battery supply of the underwater instruments or
an external underwater DC power supply. An external underwater DC
power supply may be ordered separately through LinkQuest. LinkQuest
also provides an optional internal power supply.
What kind of modulation scheme do you use to communicate between the
LinkQuest uses a
proprietary hybrid modulation scheme which we refer to as the “Acoustic
Broadband Spread Spectrum Technology”. LinkQuest does not disclose
the specifics of its proprietary technologies.
Are LinkQuest's acoustic
modems integrated with its TrackLink USBL systems and LBL
Yes. The acoustic modems
are integrated with TrackLink 1500, 5000 and 10000 USBL positioning
systems and LinkQuest's line of LBL acoustic positioning systems.
Can I obtain any additional
technical information about the modems?
Yes. Please click on
the sidebar for the 3 technical notes below.
17. Does LinkQuest offer
any other modems other than the four standard models?
Yes. LinkQuest offers
customized design to tailor to your needs.
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