AC Summer 08 WIN-T Online - United States Army Signal Center of ...

and will also significantly reduce the
delays associated with two-hop
communications associated with a
hub-based architecture. Operationally,
a mesh architecture is crucial
for transport of time critical data, but
may also be required to support
certain types of communications
such as duplex voice.
Depending on the frequency
band used (Ku-band), mesh communications
may not be possible for
small terminal to small terminal
communications. Small tactical
mobile SOTM terminals typically
have reduced aperture antennas and
may require more power than is
available from the satellite to close a
one hop link.
In these instances, the NCW
Hub-Assist mode will dynamically
route packets through the Net
Control terminal or alternative NC
to reliably maintain communications.
The NC and alternate NCs
serve as store and forward hubs to
assist NMs and route traffic to the
destination node when the link
cannot be directly closed in a singlehop
link.
NCW will not be new to the
field when it will be introduced
under the WIN-T Increment 2
program in FY 11. Early NCW
releases are in use today in the
Mounted Battle Command on-the-
Move program and a quick reaction
program called Triton. The integration,
small scale fielding, and
operational lessons learned have
been invaluable in identifying
technical and operational issues
early and provide improvements to
the system as the WIN-T program
moves forward. Periodic technical
and field tests continue at the C4ISR
OTM Test Bed, Fort Dix, N.J., to
mature the system into a high
performance and reliable WIN-T
communications network.
Statutory challenges
The WIN-T design will capitalize
on ubiquitous commercial Kuband
satellites and military Ka-band
aboard Wideband Global SATCOM
satellites to provide high bandwidth
SOTM capabilities. From a regulatory
perspective, both Ku and Ka
bands present unique challenges to
the Army.
Commercial Ku-band
Within the Fix Satellite Service
Ku-band, there are approximately
220 geosynchronous satellites listed
as operational. This density of
satellites makes adjacent satellite
interference a very significant issue,
especially when using small aperture
SOTM terminals. The current
criteria established for SOTM by
both the FCC (continental United
States) and ITU (outside of the
continental United States), however,
were principally adapted for
shipborne applications and do not
consider ground mobile environments.
PM WIN-T has formally
proposed that the regulatory limits
be changed from the rigid go/no-go
off-axis power spectral density
profile to an approach using a
statistical model. The statistical
model approach would require a
very low probability of exceeding
the off-axis power spectral density
profile caused by momentary
pointing errors due to movement of
the vehicle or ground mobile platform
on which the antenna is
mounted. These proposals are
currently being evaluated at ITU
working groups.
Regardless of changes to the
FCC/ITU criteria, dynamic spreading
of the radio frequency signal will
be required when using Ku-Band.
The WIN-T NCW design has implemented
seven unique spreading
factors which range from 0 to +12 dB
and which are computed based on
the power required to close the link
and the aperture parameters. NCW
optimizes the available satellite
bandwidth by spreading the signal
the minimum amount needed to
avoid ASI.
These changes are distributed,
every 400 milliseconds, to each node
in the network, from the network
controller via the Forward Order
Wire channel. Each of the SOTM
terminals planned for WIN-T
Increment 2 will comply with the
current criteria established by the
FCC and ITU.
Military Ka-band
For military Ka-band, the
interference environment is not as
severe. The performance criterion
for all earth terminals for military
Ka-band is codified in MIL-STD-188-
164A. Currently, Ka-Band off-axis
limits have not been established in
MIL-STD-188-164A. However, there
is an ITU Radio Regulation that
imposes the requirements for
coordination between geostationarysatellite
networks sharing the same
frequency bands.
Currently, the Army is analyzing
the ITU Radio Regulation and
will propose to the MIL-STD community
a maximum permissible offaxis
power spectral density from
SOTM earth stations. This will
promote quasi-free interference
satellite operations while maintaining
reasonable SOTM spectral
efficiency.
Summary
Substantial progress has been
realized with respect to addressing
the technical, operational and
statutory challenges associated with
deploying a SOTM based solution to
enable BLOS communications on
warfighting platforms. The initial
widescale deployment of this
capability will occur with the WIN-T
Increment 2 fieldings of PoP and
SNE CIs in FY11. The TCN CI,
which will be owned and operated
by Signal Corps personnel, will also
use the SOTM technology to enable
the entire WIN-T WAN to operate
on the move. During the course of
FY 08 -10, PM WIN-T will continue
to mature each of the SOTM components,
integrate them into functional
B-kit configurations, and subject
them to both developmental and
operational tests.
In addition, several new
advanced NCW features are being
considered for implementation.
Many of these features are being
implemented to take advantage of
new WGS capabilities, including
variable size bandwidth segments
and gain states, not available on
many commercial satellites. Other
features include improvements
related to ease of use and maintain-
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