Why should you care about VITA 49? I may just be the next big thing in software defined radio. Here is a gentle introduction.
When I was discovering my new Flex 6300 radio last year, I learned that it used something called VITA 49 protocol for communicating with the outside world over Ethernet. I didn’t pay much attention at the time. But, as I explored how to apply spatial interference filtering techniques, I suddenly realized the power of VITA 49.
The VITA Radio Transport protocol has been developed by government contractors over the past ten years to enable interoperability and advanced features between diverse radio gear. VRT, or VITA 49, is an infrastructure standard for open interfaces between different components of a radio system.
Traditionally, radios whether digital or analog have had stovepipe design, a connect-the-dots series of components all strung together. Typically, all the connections have been unique to the design in terms of things like control signal levels and even digital protocols. Now that the ADC is moving to the antenna, all signals in the SDR become digital, and the great thing about VITA 49 is that it does digital wiring over networks.
VRT enables digital signals to be linked and transported over networks. Radios can be comprised of multiple front and back ends to perform various functions “off the shelf”. These connections can be made across various physical and network layers.The trick is to put data (RF, IF, Baseband Display, Other) into structured packets each with an identifying header, context information and timestamp. The latest version of VITA 49 adds support for transmitting and control.
Roger Hosking of Pentek has a great video explaining VITA 49. You should take a look.
About VITA 49 Digital and Distributed Wiring
In its first release, VRT simply assembled IF data as a payload in a transport layer packet. These are accompanied by context packets containing meta data such as frequency, sampling rate, etc. Each packet is timestamped and serialized. The most popular format for sending these packets is multi-cast UDP over any network.
The coming second release of VITA 49 adds support for transmitting and also radio control. Additionally, different kinds of signals can be sent instead of just IF data – even spectrum display data.
What is there about VITA 49 that makes it great for spatial interference filtering? In the first instance, the timestamps on the packets. Signals coming from two VITA 49 radios can be combined to do spatial filtering because the timestamps enable phase coherence. Secondly, you can select data from multiple receivers to do various forms of advanced beamforming.
Take a few minutes to learn more about VRT. Now, the downside of VRT is that it is very open and extensible. Hopefully manufacturers who adopt VITA 49 will publicly document their extensions and applications.