Improving the ability of a submarine to communicate with other
naval assets when submerged has always represented a significant
challenge to the sub-sea systems community, chiefly because the
electrical conductivity of salt water creates an invisible shield
that most electromagnetic transmissions find extremely difficult -
if not impossible - to penetrate.
Traditionally, maritime commanders relied on one-way transmissions
using relatively slow shore-to-submarine radio broadcasts, normally
at frequencies in the Very Low Frequency (3-30 kHz) band, to pass
orders and other mission-critical information to boats on covert
operations.
Electromagnetic waves at these frequencies can penetrate water to a
depth of between 10 m and 40 m, which is sufficient for submarines
operating near the surface. Although vessels operating at greater
depths can receive and transmit messages in other bands via
cable-linked antenna buoys floating on or near the surface, this
practice exposes them to a serious risk of detection by enemy sonar
or radar.
Mechanically-generated sound waves, on the other hand, can travel
very great distances in water. Data is encoded in the acoustic
wave's amplitude, phase or frequency. Rudimentary analogue
underwater telephones have been used with mixed success for many
years; however, their ease of detection, propensity to distortion
and data loss, and frustratingly poor range has necessitated the
development of more capable systems.
Underwater acoustic communications can be affected by a range of
influences including ambient noise, path loss, high and variable
propagation delay, and the Doppler Effect (the change in frequency
and wavelength of a wave as an observer moves relative to the
source of the wave). All can result in degraded performance and
interference in the transmission.
These factors in turn affect the spatial and temporal variability
of the acoustic channel, making the bandwidth available for the
acoustic channel very limited and dependent on range and frequency.
A long-range system operating over tens of kilometres will use only
a small bandwidth of a few kilohertz, while a short-range system
will use many hundreds of kilohertz of bandwidth. Either system
will still use a very low baud (bits per second) rate, but a
consequence is the severely reduced ability to transmit larger
volumes of data.
During the Cold War, nuclear-powered submarines from the Soviet
Union, UK and United States navies were employed on long solo
patrols with a requirement to remain silent throughout. Detailed
pre-planning of missions was essential to allow boats to operate
without the need for regular instructions and operational updates
from headquarters.
Since 1991 and the demise of the Soviet Union, the role of the
submarine has changed. The ability to influence littoral areas
means that, as well as continuing its bluewater sea-denial
strategy, the submarine has now become more involved in surface
fleet operations and land-attack campaigns. In order to become a
multirole platform and engage in fleet-based activities, the
submarine must link up to the network-centric battlespace and
communicate with naval or other assets on a regular basis and be
able to send and receive relatively large amounts of data
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© 2007 Jane's Information Group
We have any current research on this form of communication
technology?
This is particularly important for us as our submarines operate in
shallow but busy waters with lots of civilian and foreign naval
traffic. Hard to avoid collateral damage in such situations.
PS. Mods, any way to restart expired threads? Because its a good
idea to lump newer info with relevant older topics.