Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...
Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...
Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...
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UAS ROADMAP <strong>2005</strong><br />
controllability <strong>of</strong> the bandwidth, frequency, and information/data (e.g. differentiated services, separate<br />
routing <strong>of</strong> data based on priority, latency, etc) flows. This means that the systems will be net-centric and<br />
that network services like C2, data management and flow control, etc., will have to be integrated into the<br />
systems and concepts <strong>of</strong> operations. In-flight entertainment and finance-based systems will not handle<br />
these issues well for military applications. The personal information services providers might provide<br />
technology paths forward, but major portions <strong>of</strong> the government will need to invest in the net-centric<br />
solutions required by the U.S. Government. One way <strong>of</strong> addressing bandwidth and spectrum constraints<br />
is by re-using certain communications paths in new ways (e.g. tactical radios used as orderwires for<br />
directional links, tightly coupled RF backup links for free space optics (lasercomm), etc.).<br />
Communications technologies might be repartitioned to address apertures, RF Front ends, s<strong>of</strong>tware<br />
defined modems/bandwidth efficient waveforms, multiple signals in space, crossbanding, digital<br />
interfaces, new communications approaches (e.g. free space optics), and hybrid approaches.<br />
4.2.1<br />
4.2.2<br />
Data Links<br />
Airborne data link rates and processor speeds are in a race to enable future UA capabilities. Today, and<br />
for the near-term, the paradigm is to relay virtually all airborne data to the ground and process it there for<br />
interpretation and decision-making. Eventually, onboard processing power will outstrip data link<br />
capabilities and allow UA to relay the results <strong>of</strong> their data to the ground for decision making. At that<br />
point, the requirement for data link rates in certain applications, particularly imagery collection, should<br />
drop significantly. Meanwhile, data compression will remain relevant as long as band-limited<br />
communications exist, but it is unlikely compression algorithms alone will solve the near term throughput<br />
requirements <strong>of</strong> advanced sensors. A technology that intentionally discards information is not the<br />
preferred technique. For now, compression is a concession to inadequate bandwidth.<br />
In the case <strong>of</strong> radio frequency (RF) data links, limited spectrum and the requirement to minimize airborne<br />
system size, weight, and power (SWAP) have been strong contributors for limiting data rates. Rates up to<br />
10 Gbps (40 times currently fielded capabilities) are considered possible at current bandwidths by using<br />
more bandwidth-efficient modulation methods. At gigahertz frequencies however, RF use becomes<br />
increasingly constrained by frequency congestion. This is especially true for the 1-8 GHz range which<br />
covers L, S, and C bands. Currently fielded digital data links provide an efficiency varying between 0.92<br />
and 1.5 bps/Hz, where the theoretical maximum is 1.92.<br />
Airborne optical data links, or lasercom, will potentially <strong>of</strong>fer data rates two to five orders <strong>of</strong> magnitude<br />
greater than those <strong>of</strong> the best future RF systems. However, lasercom data rates have held steady for two<br />
decades because their key technical challenge was adequate pointing, acquisition, and tracking (PAT)<br />
technology to ensure the laser link was both acquired and maintained. Although mature RF systems are<br />
viewed as lower risk, and therefore attract investment dollars more easily, Missile Defense Agency<br />
funding in the 1990s allowed a series <strong>of</strong> increasingly complex demonstrations at Gbps rates. The small<br />
apertures (3 to 5 inches) and widespread availability <strong>of</strong> low power semiconductor lasers explains why<br />
lasercom systems typically weigh 30 to 50 percent that <strong>of</strong> comparable RF systems and consume less<br />
power. The smaller apertures also provide for lower signatures, greater security, and provide more jam<br />
resistance.<br />
Although lasercom could surpass RF in terms <strong>of</strong> airborne data transfer rate, RF will continue to dominate<br />
at the lower altitudes for some time into the future because <strong>of</strong> its better all-weather capability. Thus, both<br />
RF and optical technology development should continue to progress out to 2025.<br />
Network-Centric Communications<br />
There are several areas <strong>of</strong> networking technology development that should be identified as critical to the<br />
migration path <strong>of</strong> UAS and their ability to provide network services, whether they be transit networking<br />
or stub networking platforms. Highflying UAS, such as the Global Hawk or Predator, have the ability to<br />
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