Network Issues Drive UAV Control Strategies /COTS Journal/
~ communications technologies remain a critical issue for Unmanned Aerial Vehicle control systems
~ airborne data link rates and processor speeds are in a race to enable future UAV capabilities
~ U.S. Military strategy is to relay virtually all airborne data to the ground and process it there for interpretation and decision making
~ onboard processing power will outstrip data link capabilities and
~ allow UAVs to relay the results of their data to the ground for decision making
~ requirement for data link rates in certain applications, particularly imagery collection, should drop significantly
~ secure, encrypted surveillance data, today’s advanced surveillance UAVs require a lot of communications overhead
~ if processing of data and decision making can be performed onboard UAV itself
~ rather than performed via a communication link with the ground, more efficiently craft can be used
~ communications technologies used for UAVs call for flexibility, adaptability
~ and cognitive controllability of the bandwidth, frequency and information/data flows
~ systems will be net-centric, network services—like command and control, data management and flow control—will have to be integrated into
~ systems and concepts of operations one way of addressing bandwidth and spectrum constraints is by reusing certain communications paths in new ways
~ communications technologies might be repartitioned to address apertures, RF Front ends,
~ software-defined modems/bandwidth-efficient waveforms, multiple signals in space, crossbanding,
~ digital interfaces, new communications approaches like free space optics, and hybrid approaches

Data Compression Required
~ data compression remains an important adjunct as long as band-limited communications exist
~ it is unlikely compression algorithms alone will solve the near-term throughput requirements of advanced sensors
~ compression is a concession to inadequate bandwidth
~ in the case of radio frequency (RF) data links, limited spectrum and the requirement to minimize airborne system size,
~ weight and power (SWAP) have been strong contributors for limiting data rates
~ rates up to 10 Gbits/s (40 times currently fielded capabilities) are considered possible at current bandwidths
~ by using more bandwidth-efficient modulation methods at gigahertz frequencies RF use becomes increasingly constrained by frequency congestion
~ this is especially true for 1-8 GHz range, which covers L, S and C bands
~ currently fielded digital data links provide an efficiency varying between 0.92 and 1.5 bps/Hz, where the theoretical maximum is 1.92
~ airborne optical data links, or lasercom, will potentially offer data rates
~ two to five orders of magnitude greater than those of the best future RF systems
~ lasercom data rates have held steady for two decades because their key technical challenge was adequate pointing,
~ acquisition and tracking (PAT) technology to ensure the laser link was both acquired and maintained
~ although mature RF systems are viewed as lower risk, and therefore attract investment dollars more easily,
~ Missile Defense Agency funding in the 1990s allowed a series of increasingly complex demonstrations at Gbit/s rates
~ the small apertures (3 to 5 inches) and widespread availability of low-power semiconductor lasers
~ explain why lasercom systems typically weigh 30% to 50% that of comparable RF systems and consume less power
~ the smaller apertures also provide for lower signatures, greater security, and provide more jam resistance
~ although lasercom could surpass RF in terms of airborne data transfer rate,
~ RF will continue to dominate at the lower altitudes for some time into the future because of its better all-weather capability
~ forecasters of both technologies expect that RF and optical technology development should continue to progress out to 2025