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connecting to more than one node, can act as network routers, passing internet data packets between the
multiple connected nodes. In this way UA can contribute their unused bandwidth to the overall carrying
capacity of the GIG, Figure C-4 illustrates this transition. The next several paragraphs describe current
and future CDL programs and some IP convergent strategies.
Baseline Common Data Link. The program originated in 1979 as a collaborative effort between the
USAF, Assistant Secretary of Defense (ASD), and the National Security Agency (NSA) in support of the
U-2 collection mission. Success onboard this and other platforms subsequently resulted in the Office of
the ASD (OASD)/Command, Control, Communications, and Intelligence (C3I) issuing a December 1991
policy memorandum mandating CDL as the DoD interoperability standard for LOS communications of
airborne ISR sensor data to surface-based (land/sea) processing terminals. A June 2001 policy update
further extended the CDL standard to include air-to-air and BLOS relayed ISR applications.
UAS ROADMAP 2005
APPENDIX C - COMMUNICATIONS
Page C-8
CDL terminals typically support full duplex, jam-resistant, secure digital communications in either X or
Ku-band at selectable data rates ranging from 0.2-2 Mbit/s on the forward link (command/control data)
and with return link (sensor data) rates from 10-274 Mbit/s. In recent years, CDL applications have been
extended to a variety of manned and unmanned tactical platforms, fueled by affordability advances led by
the tactical common data link (TCDL) program which introduced intermediate-level performance and
interoperability at the lower (< 45 Mbit/s) CDL data rates. Continuing advances and leveraging of
commercial microelectronics have since extended similar technology-cost advantages to full-rate CDL
applications. Although most CDL applications employ point-to-point radio links between the ISR
collection platform and processing terminal, emerging applications entail point-to-multipoint
(simplex/broadcast) operations to multiple receive-only terminals. Additional ongoing CDL capability
enhancements include:
Increased forward and return link data rates (up to 45 Mbit/s, 1096 Mbit/s respectively) to address
evolving forward link applications and bandwidth demands posed by high performance hyper-spectral
and multi-sensor platforms.
Enhanced point-to-multipoint capabilities providing full duplex, low-latency network
communications between a central (collection or fusion) node and its multiple (sensor or user) client
nodes.
Advanced Waveforms providing variable bandwidth on demand (ranging from 10Kbit/s – 274
Mbit/s), optimized for IP-based data transfer, and enhanced RF link range/weather/jamming
performance.
System architecture/software migration to JTRS SCA compliance. Although envisioned objective
capabilities pose software/waveform portability and interoperability advantages, current JTRS
technology base and associated performance does not currently meet user and system throughput
requirements.
Transition to IP-based user interfaces. Historically, CDL based systems were not networked on either
the air or surface ends of the link. The approach taken by the platform/ integrating contractor towards
integration of multiple sensors/functions into the CDL interface would generally entail optimization
for the specific program application, although often at the expense of compounding or precluding
interoperability with other programs/Services. Custom conventions generally would entail the
methods by which multi-sensor data would be multiplexed external to CDL and bit-stuffing or other
means by which the aggregate would be bandwidth matched to the one or multiple CDL synchronous
channels. The recent trend within CDL, now motivated by the OSD mandate, requires the provision
of an IP-based CDL user interface to the platform. This should effectively eliminate custom platform
integration conventions helping to establish CDL as part of a seamless GIG communications
infrastructure.
Variant CDL Program Descriptions
Tactical Common Data Link. Provides simplex or, full duplex, and jam-resistant links for tactical UA
and other applications, with initial prototype demonstrations supporting 200 Kbit/s forward link and 10.7
Mbit/s return link rates. Ongoing developments are currently expanding to full rate capabilities (up to 45
Mbit/s forward link and 274 Mbit/s return link). The Army's Tactical Unmanned Aerial Vehicle (TUAV)
Operational Requirements Document (ORD) requires TCDL, as does Fire Scout. Both the Army and the
CDL Program Office are pursuing miniaturization of the TCDL for tactical UA applications.
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