John Keller
ARLINGTON, Va. – U.S. military researchers are asking industry to develop secure radio frequency (RF) transmitter and receiver technologies to enable the next generation of secure military tactical radio systems.
Officials of the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., have issued a solicitation (HR001120S0030) for the Wideband Secure and Protected Emitter and Receiver (WiSPER) project.
Today's military secure tactical radios achieve security by spreading transmitted content over time and operating frequency in attempts to reduce transmitted power density and operate below the adversary's receiver detection limit.
Still, spread-spectrum techniques lack sufficient complexity to evade detection by modern signals intelligence (SIGINT) receivers or interception by compromised devices.
Hypersensitive receivers use cryogenic-cooled energy detectors and cyclostationary processing over prolonged observation time to increase detection sensitivity by reducing uncorrelated noise. This technique reveals chip rate and modulation format to establish spread-spectrum transmissions. Collaborative receivers, meanwhile, involve multi-receiver networks that coherently recombine power to detect the transmitter.
Today's spread-spectrum approaches have several limitations. Narrowband signals are only spread in the time and frequency domains and contain cyclic features, for example. Narrowband RF waveform typically use fixed and limited dynamic range of less than 30 dB, leading to the inability to remain undetectable while providing persistent communications.
New chaotic waveforms that reduce cyclic features only provide marginal reduction of detectability, require higher signal-to-noise ratios to synchronize and operate, and are not sufficiently featureless to evade detection. Directional beams and reconstruction of coherent scattered signals, in addition, are impractical for today's tactical radios.
While spread-spectrum techniques minimize the signal strength to avoid detection, today's tactical radios face additional operational challenges from channel impairments that reduce the link margin of the radio.
With fixed operational frequency and bandwidth, existing tactical radios provide limited options and margins to sustain persistent transceiver operations under varying and unpredictable natural and man-made channel impairments.
Instead, the WiSPER program seeks to develop fundamentally disruptive wireless air interface transceiver technology to enable and sustain secure high-bandwidth RF communication links. The WiSPER wideband adaptive air interface also will mitigate impairment from dynamic harsh and contested environments to maintain a stable communication link.
DARPA researchers anticipate that WiSPER capabilities also will provide future U.S. warfighters with a dominant technology advantage over their adversaries. Researchers want radios small enough for portable or ground installations.
WiSPER will be a four-year, three-phase program with an 18-month first phase, an 18-month second phase, and yearlong third phase. Several phase-one contracts are expected, with a reduced number of participants in the second and third phases.
Phase 1 performers will carry the WiSPER system architecture through a conceptual design supported by modeling and simulation, culminating in a benchtop implementation and lab test.
Phase 2 performers will improve the design, culminating in a transportable implementation and field test. Phase 3 performers will further optimize the air interface to demonstrate adaptation to weather and other impairments in a portable prototype implementation.
Proposals to WiSPER will be classified at the collateral SECRET level, so performers will need collateral SECRET clearances and access to an accredited facility and secure communications.
DARPA must receive proposals by post or by courier no later than 15 July 2020 to Defense Advanced Research Projects Agency, ATTN: Program Security Officer, MTO, Reference: HR001120S0030, 675 North Randolph St., Arlington, VA 22203-2114.
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