Spreading the spectrum amongst friends.
Armada International › Vol. 33 Nbr. 4, August 2008
Linked as:
Summary
Tactical Radios 2009
See the full content of this document
Extract
Spreading the spectrum amongst friends.
Wideband transmission is once again coming to the fore in tactical communication. This is not a new development, as research at the laboratories of MIT, Magnavox, ITT and Sylvania as far back as the 1950s lead to early spread-spectrum technology. And now, somewhat ironically, today's military communication hardware is increasingly relying on software, and tactical radios are juggling their waveforms to find comfortable talking space.
The electromagnetic spectrum is finite. There is only so much space in which to push across all the voice, text, data, imagery and other information that must be shared within a battlespace without eventually stringing up a few wires here and there. Add to this the fact that urban, jungle and dense woodland environments as well as inclement weather situations all work against the radio wave's journey. Compounding these communication headaches are those who bring along their kit to disrupt, jam or intercept another's message traffic. Combine these obstacles, and the simple act of passing a 'yes' or a 'no' across a 20-metre stretch during a firefight can become a true nightmare. Solutions ... Fortunately, never before have armies around the world enjoyed such a wide equipment selection in the tactical radio domain. A score of companies in Europe, the United States, Russia, Australia, the Middle East and Asia are producing a host of products ranging from hand-held systems through to vehicular and fixed radios. The imperative to handle large quantities of voice, data and video imagery is pushing electronic engineers to crowd increased capabilities into radios that must somehow remain lightweight, robust and small enough to ensure that they do not burden the soldiers or the vehicles that they will equip. Europe plays host to several tactical radio manufacturers. Selex Communications produces the High Frequency/Very High Frequency (HF/VHF) CNR-2000 manpack and vehicle-mounted tactical combat net radio. The CNR-2000 covers a frequency range of 1.6 to 60 MHz and pushes either ten or 25 Watts of power. The radio weighs 3.7 kg and includes Transmission Security (Transec) and Communications Security (Comsec) encryption parameters. The radio supports the following: CW (Continuous Wave--J2A), USB/LSB/FM voice, FSK (Frequency Shift Keying), NPSK (Phase Shift Keying) and NQAM (Quadrature Amplitude Modulation). Up to ten hours of battery life is possible, and the radio also contains an embedded Global Positioning System (GPS), HF-to-HF and VHF-to-HF rebroadcast capabilities and third-generation ALE (Automatic Link Establishment). Selex also produces the Vehicle Integrated Personal Role Radio (PRR), which provides communication between troops and supporting vehicles. The vehicle PRR operates across two to four MHz, has a range of around 500 metres and employs Direct-sequence Spread Spectrum (DSSS) modulation. DSSS multiplies the data being transmitted through the use of a 'noise' signal that is much higher in frequency than the original signal, thereby spreading the signal's energy into a much wider band. DSSS provides some resistance to both deliberate and unintentional jamming, allows the sharing of a single channel amongst multiple users and its use of a pseudonoise code reduces the signal-to-back-ground noise ratio (making it a very quiet, stealthy signal). Many GPS and satellite navigation sys...See the full content of this document
Sponsored links
