access to the information needed by the war fighter. Drawing on these services, the end user will receive information in the format and time of his choosing (Smart Pull).
Common Data Link
Today’s CDL provides the only means to meet ongoing, wide band, communications requirements. CDL is the DoD mandated standard for wireless data link communications of high capacity airborne ISR sensor data. Data link interoperability is governed by compliance with CDL specifications that address waveforms, associated protocols, and external (platform/sensor/network) interfaces. CDL is a full duplex, although asymmetric, wide-band data link that connects the UA to its control station either directly or via SATCOM. The control station generally transmits command and control data at 200Kbit/s and receives sensor product at up to 274 Mbit/s.
Information exchanges occur primarily between the UA, its control station, and specially designed external interfaces, such as Air Traffic Control voice radio and video feeds. UA products, after being processed, flow to external nodes from the control station servers through network connections. In its current form CDL provides a closed circuit between the UA and its control station, carrying commands, status, and sensor products. The control station, as an edge device on the GIG then provides this information to the user community, while keeping the UA isolated from the GIG. CDL equipped UA must transition from a closed circuit, merely using communications services, to a network node, actually providing communications services.
The first step to achieving net-centricity involves net enabling the interfaces. This means creating IP based network connections and routers between UA subsystems and the on board data link with corresponding network interfaces between the control station data link, control station subsystems, and the GIG. This changes the paradigm from that of a closed circuit to that of a network node. Functions and products of UA implemented as network nodes would be accessible to other authorized nodes on the GIG, not just to the control station. The UA itself becomes an edge device on the GIG.
The second step involves UA that can connect directly to more than one node on the GIG. During times when the demand on the data links is low, such as during cruise portions of the mission, UA capable of 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.
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