Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...

UAS ROADMAP 2005
The family of standard CDL waveforms 4 provides an exceptional range of features that allow CDL to be
tailored to meet many program, platform, and operational needs. Because of this flexibility, a transmitting
terminal and an associated receiving terminal may both be compliant with the CDL Waveform
Specification, but may not be interoperable because they are designed or configured to conform to
different parts of the specification. The need to standardize the user systems interface to the
communications system has resulted in the approval of Annex B of the CDL specification. The following
section describes the key parts of Annex B.
STANAG 7085 (Interoperable Data Links for Imaging Systems)
The CDL specification has been made available to NATO in the form of STANAG 7085. STANAG
7085 is currently based on Revision E of the CDL Specification. Release of the newer Revision F to
NATO is in progress.
CDL Terminal Interoperability
In the OSI reference model, the physical layer (layer 1) provides the physical means for transmitting
digital data from one computer to another and regulates the transmission of the stream of data over a
physical medium. In CDL terms, the physical layer is composed of a pair of radio terminals (e.g., an
airborne terminal and a surface terminal, or two airborne terminals) and the complex radio waveform that
establishes the link between the two terminals. Interoperability profile compliant systems will use the
CDL Spec Annex B to define the physical layer. In addition, compliant systems will implement one or
more external IEEE 802.3 100BaseTX Ethernet ports for interconnection with external Ethernet-based
local area networks.
Data Signal Framing
The OSI reference model data link layer (layer 2) establishes the procedures and protocols for
transmitting data over the physical layer. Among these functions is packaging the bits into packets, cells,
or frames for transmission, and for recovering the data at the receiving terminal. Layer 2 protocols have
means for detecting and correcting errors that may occur during transmission. In the CDL context, layer 2
also provides a means for the receiving terminal to identify the beginning of a frame of data in the
unbroken stream of bits received over the link. CDL layer 2 networking protocols are specified in
appendix II and annexes A, B, C, and D of the CDL waveform specifications. Annex A details the
ATM/CTFF framing procedure used by some CDL systems. Annex B details the Ethernet/GFP framing
procedure.
No changes are required in the Ethernet or GPF protocols (Layer 2) to support either IPv4 or IPv6 (Layer
3). Only the IPv4 Header Compression (Layer 3) feature will have to be turned off or updated to support
the new IPv6 header compression scheme if desired.
Data framing with Ethernet
Interoperability profile compliant systems will, as a minimum, implement layer 2 framing of data using
IEEE 802.3 100BaseTX Ethernet (up to 100 Mbps), as defined in the CDL waveform specifications,
appendix II, annex B. Further, interoperability profile compliant systems will implement the specific
Ethernet datagram structure defined in annex C. These requirements, however, do not preclude system
architectures from implementing additional layer 2 framing procedures.
Generic Framing Procedure (GFP)
Standards Profile compliant systems will as a minimum implement international telecommunications
union (ITU) generic framing procedure as defined in the CDL waveform specifications appendix II,
4 Defined in Waveform Specification for the Common Data Link (CDL), Specification Number 7681990, Revision F,
available through the Air Force Aeronautical Systems Center (ASC/RAJD).
APPENDIX E – INTEROPERABILITY STANDARDS
Page E-5