Military
The Challenge
The US Navy needed to
establish a reliable
45Mbps microwave radio
link between a fixed site
on shore and a mobile
Test Ship for use in their
Pacific Sea Test Range.
The Solution
Working with the Navy
and their chosen
contractors, Harris Stratex
Networks provided
Eclipse Nodal Wireless
system which was
integrated into a novel
stabilized tracking system
that enabled reliable
communications to be
maintained between ship
and shore despite the
movement of the ship.
Stabilized Ship-to-Shore Link for U.S. Navy
Introduction
The Test Ship
NSWC Corona Division Telecom
engineering has designed a state-of-the-art
45Mbps (DS3) ship-to-shore, line-of-sight
communications link for the Self Defense
Test Ship (SDTS), which is an unmanned
vessel remotely controlled from shore
during live fire operations at the Navy’s
Pacific Sea Test Range.
In March 2003 the decommissioned
Spruance-class destroyer USS Paul F.
Foster was turned over to Naval Surface
Warfare Center Port Hueneme Division to
serve as the Navy’s new Self Defense Test
Ship (SDTS) on the waters of the Pacific
Sea Test Range off the coast of Southern
California.
This communications link will be one of the
longest ship-to-shore microwave links in the
world, spanning up to 50 miles.
The SDTS is used as a test platform for
various US Navy defensive weapon
systems. It operates unmanned, under
remote control during these tests.
The SDTS provides a flexible test platform
with reduced safety constraints associated
with manned ships.
During a typical live fire test, various threats
are actually aimed at a decoy barge towed
150 feet behind the unmanned SDTS,
protecting the ship and its assets.
Communication Link
The Result
The Eclipse system is
able to select the best
signal operating between
four independent links
that are separated
spatially and by frequency
to ensure a high
availability
communications link over
50 miles of water.
What makes Eclipse especially
useful is the common interface
between ODU & INU regardless
of the RF frequency choice.
Flexible network interfaces and
frequency diversity are other
reasons why Eclipse is an
excellent choice for microwave
system engineers.
The Navy is using the Eclipse platform from
Harris Stratex Networks to provide wireless
communications between the SDTS and a
shore communications site.
Equipment located on the ship and shorebased tower will be installed on stabilized
tracking pedestals to enable the
communications link to be maintained as
the SDTS moves about within the test
range area.
The Navy desired to use cost-effective
commercially-available microwave systems,
but needed to be able to support a complex
path protection scheme to increase link
reliability and the integration with a stabilized
antenna pointing system to enable
communications to be maintained with the
test ship regardless of its position and attitude
within the test range. This increased link
reliability enabled constant remote control of
the ship's maneuvering and weapon systems
during operations at sea.
Greg Garnier
Civil Engineer Corps
US Navy
Eclipse Dual Diversity
Harris Stratex Networks supplied a system
that is comprised of a total of four
microwave links operating in parallel in sets
of two.
Each set is comprised of two frequency
diverse links operating in the 5 and 7 GHz
bands.. Traffic is duplicated over each link,
with the best quality signal being selected at
the remote site.
Frequency diversity operates on the
premise that since each link operates on a
different channel frequency (in this case in
entirely different frequency bands) the
www.harrisstratex.com
Page 1 of 2
2/8/2007
propagation characteristics of each will be
very different, with fading of each link being
uncorrelated to the other.
Consequently, when the signal received
from one radio (the 5GHz link for example)
is degraded, the signal from diversity link
(the 7GHz link) will be less affected. The
selection between the two available paths is
performed automatically by an external
switch/router.
The Eclipse advanced Nodal
wireless system enables
optimized backhaul networks, by
supporting multiple radio paths
from a single, modular indoor
unit, with traffic routing
performed internally under
software control.
Eclipse provides professionalgrade wireless connections in
frequency bands from 5 to
40GHz, for TDM
(PDH/SDH/SONET) and Data
(Fast and Gigabit Ethernet)
applications.
A single shore communications tower will
host both sets of links, while the ship-based
equipment will be split between the forward
mast and aft masts respectively. This
enables the link to be maintained during
ship maneuvering when either of the two
ship-mounted sets is obscured from the
shore site by the ship infrastructure. The
system will automatically switch between
the fore and aft diversity radio outdoor unit
(ODU) set when blockage or path failure
occurs.
Stabilized Platforms
Microwave radio systems are traditionally
designed to operate on fixed links between
two fixed sites, so special arrangements
were made to ensure that the antennas at
each end of the link remained aligned while
The pedestal is able to automatically lock
onto and track the signal using a
combination of the radio received signal
level (obtained from the ODU AGC
monitoring point) and the ship’s GPS
positioning system. This enables free, 360
degree movement and also allows the link
to cope with changes in elevation and
azimuth caused by the pitch and roll
movement of the ship.
The Result
the SDTS moved around the test range.
To achieve this, the ship and shore
antennas and RF outdoor units (ODUs)
were mounted on special stabilized
pedestals, of the type that have been used
for ship-based satellite communications
systems.
Each diversity ODU set is mounted on a
separate pedestal, which remains locked
onto the signal received from the
corresponding set at the far end of the link.
The US Navy benefited from the flexibility
provided by Eclipse to support frequency
diversity paths operating in separate
frequency bands. Eclipse was able to
support dual diversity functionality, enabling
a resilient high speed point to point link to
be established to ensure constant
command and control of the SDTS.
Copyright © 2007 Harris Stratex Networks,
all rights reserved.
www.harrisstratex.com
Page 2 of 2
2/8/2007