DIFI Lays the Building Blocks for Ground Tech Interoperability

When things just work, isn’t that really a thing of beauty? When things work, we’re able to do more, to achieve more. We progress. We improve. However, sometimes to get things to work, often means people and organizations collaborating and working together for the greater good. In the ground segment of the satellite industry, it has previously been dominated by proprietary systems and technology. While this approach is understandable, customers perhaps would prefer a different approach, greater interoperability, that will make it easier for them to make key tech decisions going forward.

Industry group DIFI, which is embracing a message of interoperability, seems to be going from strength to strength. Founded in August 2021, the Digital Intermediate Frequency Interoperability Consortium is an independent group advocating for interoperability between satellite and ground system networks. DIFI set out to establish an interoperable digital interface/radio frequency (IF/RF) standard based on digital radio standard VITA 49.2, which is well adopted by the industry.

The consortium made good progress last year and in August, released the IEEE-ISTO Std 4900-2021: Digital IF Interoperability 1.1 Standard, an updated version of the initial 1.0. With 54 members now in tow, Version 1.1 of the specification has seen 800 downloads, and the group is releasing open-source software to help companies with compliance and certification testing.

DIFI’s goal is to provide interoperability at the digital IF level of the system. Legacy systems that use analog L-band for IF transport provide a natural interoperability. However, when IF signals are digitized for transport, there are many ways to define the packet structure. The DIFI standard specifies that packet structure to ensure interoperability.

In the big picture, standardization helps give satcom customers the confidence to transition to digital infrastructure since, with DIFI compliance, they can be assured that they will not get locked in to one vendor. It also helps the vendor community to know that if they invest in digital IF-based products, there will be a market for their products.

“This new standard is just the first step for ground tech interoperability. DIFI is about supporting a movement within the industry away from proprietary systems towards open solutions that will allow the industry to interoperate, both within dedicated satellite networks and across the rest of the communications industry networks. It will also enable the industry to scale our infrastructure to support the bandwidth and capabilities of future software-defined satellites and LEO/MEO constellations,” says Stuart Daughtridge, chairman of DIFI and senior vice president for Advanced Technologies at Kratos.

Several companies have announced they are using and working on DIFI 1.1 compliant products, while its received considerable support from the armed forces, too. The U.S. Navy is a founding member and the U.S. Army requested DIFI compliance in the EDIM (Enterprise Digital IF Multi-Carrier) modem pre-solicitation announcement that was released in October last year. The army has since released two more requests for information pertaining to two DIFI-compliant devices, one focused on Digital IF Converter (IFC) and another on Digital IF Combiner-Divider.

DIFI chose to have the specification and certification software freely available via its website in order to avoid any limitations on adoption. However, as the group gains acceptance, evolution of the specification and certification processes will affect the entire industry. It is the group’s hope that most companies will want to be part of shaping this evolution.

While DIFI has made strong progress so far, further adoption of the standard will be key. It must continue to adapt to the full range of industry use cases while retaining backwards compatibility. The group is also working to create a third-party certification process to provide end users with assurance that DIFI-compliant products will interoperate.

Scalability, the Cloud and Happy Customers

On the back of significant technological changes, open standards are increasingly important, Daughtridge explains.

“In the past, satellites were very bandwidth limited. As a result, optimizing for bandwidth efficiency was more important and valuable than following standards to achieve interoperability between systems. The newer satellite architectures and constellations have changed all of that. Now, the ability to cost-effectively scale operations is the most important factor that will drive future profitability,” says Daughtridge.

Standards create value by enabling scale through interoperability. This could be interoperability within the telco industry as a whole via the MEF (Metro Ethernet Forum) and 3GPP standards, or within the supply chain that DIFI offers. There are other standards that have been available, although they haven’t always been implemented in a standard way, notes Daughtridge. This is one of the elements that the group is working to assure through certification.

“The ground tech environment has evolved from a bespoke system to a commodity environment to a much more open environment, allowing for more interoperability and seamless transitions. There are also lower operating costs for providers like ourselves,” says Rob Rainhart, COO at HawkEye 360 and DIFI member. “Operators continue to look for ways to drive down these costs and consolidate the ground to a hosted environment, and to do that you have to have standards. DIFI propels that kind of vision forward.”

The satellite industry is advancing in technology and capabilities. There are new constellations in multiple orbits, alongside new standards in the ground segment. Bringing these together, what heightened capabilities are on the cards?

For ST Engineering iDirect, it’s a future where satellite connectivity can be established from a cloud environment through the digital interface directly to the antennas. This is something the company successfully demonstrated together with Microsoft Azure last September. The two proved the ability of a virtual modem to extract information from a high-speed satellite connectivity link. They showcased a virtualized SCPC modem receiving satellite signals digitally via an ethernet cable. Signals from satellites today are traditionally connected to physical modems via analog cables that are not directly compatible with cloud-based networks. This demonstration showed that, in the future, it’s possible for virtual modems to run on third-party cloud infrastructure replacing the need for a physical on-premise satellite modem.

Converting hardware into software installed and managed remotely via third-party data centers would give satellite operators more flexibility over their networks and speed up how quickly they can respond to customer demands.

“A virtualized modem located in the cloud that can send satellite signals from a cloud environment through the digital interface directly to the antennas would further reduce the complexity of operations and improve the flexibility of service provisioning. It would provide the opportunity in the future to buy the modem capability via a service model whereby service providers would buy a subscription and pay only for the needed capabilities,” explains Frederik Simoens, CTO of ST Engineering iDirect and DIFI member.

What’s Next?

If this standard is just the first step, then what is next for ground tech interoperability, and how could it impact the industry going forward? Surely, all parts of the system — of the combined space and ground network – must support connectivity, service levels and scale. After all, if a standards group is only focused on infrastructure vendors, wouldn’t this raise the chance of not meeting the industry-wide needs of operators? Would it satisfy the scalability requirements that lead to broad acceptance as a true standard?

The mobile industry saw massive growth and expansion of their markets when it moved from 2G proprietary architectures to interoperable 3G standards-based architectures. The satellite industry is at a moment of transition from 2G to 3G, from proprietary networks to the wide adoption of telecom and satellite industry standards. This transition is just starting, yet momentum is building, and the industry can use this to drive growth in the long run.

“The entire satellite industry is going through a digital transformation, not just satcom. In fact, the Earth Observation and new space market led that transformation. Their very low-cost satellites drove the need for very low-cost launch services and more flexible, lower cost digital ground infrastructures. Software-defined payloads are driving that need for flexibility, responsiveness and speed in the satcom world. So too is the Ground-as-a-Service model,” says Daughtridge.

Government and defense missions are also driving transformation with their need for multi-domain/multi-orbit missions and more. Interoperable ground systems are essential for all parts of the satellite industry across a wide variety of use cases, and that is why it is important to have all parts of the market represented within DIFI.

“The entire ecosystem needs to be on board to make the virtualization of the ground segment a success. Different industry segments must work together to implement the standard. If we only cloudify the modem side, then we cannot create a fully digital teleport,” says ST Engineering iDirect’s Simoens.

In order to fully virtualize the ground segment and create a digital teleport, the next area of development will need to look at how modulators and demodulators interface with other key parts of the teleport such as antennas, amplifiers and frequency converters. Different industry segments must work together to implement the standard: cloud providers, satellite ground platform manufacturers, teleport operators, antenna manufacturers, and ground segment ODU (outdoor unit) manufacturers. If the antennas and amplifiers aren’t cloudified too, they won’t be able to speak the digital language, and the teleport will not be virtualized. All parts of the ecosystem will need to be engaged to complete the puzzle.

DIFI is an important part of the interoperability challenge when it comes to virtualizing modem technology. However, there are many other aspects to interoperability. The integration of satellite with terrestrial networks, for instance, requires interoperability at the management and orchestration layer. Here, the standardization work being done within 3GPP- non-terrestrial networks (NTN) looks promising. Another area is space/ground convergence, which requires tighter interaction between the satellite and ground assets. The standardization on how these different components should interface is currently being examined.

“Standardization will play an integral role in the evolution we are seeing in the industry,” says HawkEye 360’s Rainhart. “There is demand for faster processing and processing that can take place across different environments, and you need a set of standards in order to move that needle forward.” VS