Common Data Link

Abstract: A method for collecting individualized network usage data includes routing Internet communications between a plurality of local clients and a plurality of remote servers over a common data link between a router device and the Internet. For each of the plurality of clients, characteristics of that client's communications routed over the data link are monitored at the router device. A collection of statistics reflecting the monitored characteristics are maintained. From the router device, the collection of statistics are periodically communicated over the data link to an interested server.

Abstract: : With the increasing importance of sharing computer-based information between tactical platforms, the Australian Defence Force (ADF) is aware of the need to enhance its ability to distribute such information, to those who need it, in a timely fashion. There are many systems available or being developed that can contribute to meeting this requirement. This report describes the capabilities provided by a selection of technologies, considered to be of potential relevance to the ADF. This includes enhancements to Link-16, the Improved Data Modem (IDM), Link-22 and the Common Data Link (CDL). A discussion of the interoperability issues that need to be considered when implementing any such systems in the ADF, is also included.

Abstract: Sensors which collect information for intelligence, surveillance and reconnaissance generate a substantial amount of data. High data rates are required to transmit the information in reasonable time intervals. This paper describes the objectives and progress on the development of laser communication terminals for aircraft, transmitting high speed data over distances greater than 100 kilometers. The terminals are being designed and built under the Air Force Research Laboratory’s EO Sensor Technology & Evaluation Research (ESTER) program. The free space laser communication system consists of three terminals developed around commercial fiber-optic standards. They are designed to be an open system, full duplex, protocol neutral, and operate at 2.5 gigabit per second, capable of expanding to 10 gigabit per second. The terminal’s data rate can be reduced if atmospheric effects cause a significant increase in bit error rate. The free space optics are mounted in a pointing & tracking gimbal which interfaces with an avionics unit that measures aircraft GPS information. Fine pointing and tracking is maintained by using a beacon signal which switches from wide to narrow divergence when signal lock is achieved. The terminals are designed to operate in air-to-ground and air-to-air scenarios. Subsystem laboratory tests are being completed and the terminals are being prototyped. The first set of tests will be conducted between ground sites and the first flight demonstration will involve interfacing with the multi-purpose common data link (MP-CDL) on an aircraft. We provide a description of our terminal design, show our estimated operational performance, describe the results of laboratory testing, and outline the future program activities.

Abstract: Common Data Link (CDL) is the US Department of Defense's standard RF communication system for airborne intelligence, surveillance, and reconnaissance (ISR) systems. It has evolved over the past 30+ years to include a large family of data rates and waveform variants and is used in a number of applications. Two important capabilities are attracting increasing attention in recent years: networking and spectral efficiency. The current point-to-point, full-duplex architecture does not allow a moderate number of terminal modes to form an ad-hoc mesh network. Moreover, if the number of nodes within a network exceeds a small threshold, the available CDL spectrum can be easily exceeded. If not resolved, these issues will significantly limit future CDL applications and deployment. This paper discusses the history of the networking and spectrum aspects of CDL. It explains why the existing CDL architecture, if unmodified, is not suitable for the next generation ad-hoc mesh networking. It proposes a new, spectrally efficient, half-duplex CDL (HD-CDL) waveform as the candidate for the next generation wideband mesh networking data link waveform, and explains how the proposed HD-CDL extension enables CDL mesh networking. It also discusses challenges that a system integrator may face in transitioning from the current point-to-point full-duplex implementation to the proposed HD-CDL. The focus of the discussion is the physical layer specification, but other network layers and functions will also be briefly discussed.