Open Interface Standardization
Open Interface Standardization
Based on ANSI-VITA 49.0-2009
ANSI/VITA 49.0-2009 is not itself a waveform standard, but rather, is a standardized process for defining waveforms. As such, ANSI/VITA 49.0-2009 offers an ideal starting point for defining waveform objects and vectors to be incorporated into an open commercial interface standard for MILSATCOM Digital IF.
Complex Envelope Sampling
Complex sampling, “real and imaginary,” “in-phase and quadrature,” is a fundamental aspect of Digital IF implementation.
The Complex Sampling Plane
Digital IF Conversion to RF
RF Conversion to Digital IF
The Digital IF standardized interface will gather groups of contiguous complex digital samples into frames.
Frame Overlap and Windowing
These complex sample frames will overlap and be "windowed" for efficient digital processing and more reliable monitoring.
Frequency Bins via FFT / IFFT
Digital IF waveform frames will be conveyed over a standardized interface as complex frequency “bins” rather than complex time “samples.” Advantages include sampling efficiency, overall computational load, out-of-band noise control, dynamic range preservation, frequency agility and flexibility of implementation.
Context Data & MetaData
Digital IF allows waveform vector frames to be arbitrarily “tagged” with context data and Metadata. Examples include amplitude reference levels, waveform power level, over-the-air center frequency, equipment designators, terminal designators, link ID, satellite ID, transponder ID, control metrics or any number of parameters required, now or in the future, to support desired features.
Once each waveform vector frame is tagged, it must then be “encapsulated” or “packaged for transport.” The method of choice is to use an internet protocol (IP) encapsulation process. IP is a well established standard with a bountiful supply chain and a clear growth path. IP allows for switches to be used in near-term terminal architectures, but also offers the ability to upgrade to an IP switch-based architecture in the more distant future for a richer terminal feature set.
Ethernet transport also leverages an independent mature technology base. Ethernet also has a clear growth path, with higher transport rates planned for the future. IP encapsulation makes it possible to be flexible in terms of Ethernet implementation. For example, 100BaseT, 1000T and 10 Gbit Ethernet can be used, depending on the required RF bandwidth. Furthermore, Ethernet can be implemented either in twisted pair, in fiber, or in an Ethernet backplane, and all are standardized. It is also possible to accommodate secure Digital IF transport wirelessly.
Control, Monitoring and Alarm (CMA) can take many forms, and CMA requirements vary a great deal between terminal appliances. However, once an IP network is established for Digital IF waveform transport, a separate CMA network is unnecessary. CMA should be conveyed through the same network. The clear path to unified CMA is an SNMPv3 interface. As a bare minimum, each terminal appliance on the Digital IF network should have a fully functional SNMPv3 interface. Each terminal appliance can have its own MIB, but universal SNMPv3 access is the common denominator that enables secure centralized terminal control.
Commercial and Open
A commercial open standard is central to achieving maximum return on a modest MILSATCOM Digital IF investment. The standardization process engages the stakeholders in formal and meaningful collaboration. A commercial open standard then establishes a vehicle for interoperability, facilitating plug-and-play compatibility. A commercial open standard serves as a reference point to simplify Government procurement, whether COTS or open competition. And a commercial open standard fosters innovation and competition by opening the field of development to new industry stakeholders.
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