LTE control signalling vendor Diametriq announced today that its Diameter Interworking System now supports the ability for prepaid subscribers to roam between 3G and LTE networks.

The addition of a newly developed CAMEL/WIN spec that translates to diameter in LTE networks is being touted by the company at the LTE North America 2013 conference in Dallas this week. Diametriq was formed in 2012 from the 4G signalling assets of IntelliNet Technologies Inc., which specialized in diameter signalling, SS7 and data offload, but sold the offload assets to Ruckus Wireless.

Even with the rapid growth of LTE worldwide, the stages of development in any particular market, or across markets, is uneven, according to Anjan Ghosal, president of CEO of Diametriq.

“The realization has come that not everybody is going to build out at the same pace. Some operators are looking at building out their network over the next five years,” Ghosal said. “What that leaves is some big coverage holes for folks that want to get LTE as much as possible.”

He said that Diametriq sees three key drivers for LTE interworking with legacy networks:

The desire of operators with LTE networks to have the ability for customers to fall back to 3G.

In markets such as Europe, where many operators don’t have LTE networks, they still want their customers who travel abroad to LTE markets to be able to access the faster networks when available.

Reluctance on the part of carriers to invest in entirely new roamer steering or analytics technologies for 4G networks, rather than figuring out ways for 4G signaling to be converted to 3G and maintain the legacy systems for some time to come.

“We offer a cost-effective alternative to upgrading a legacy system or purchasing a new one,” Ghosal said.

The CAMEL/WIN specification was developed by Diametriq in conjunction with a major Tier One operator, the company said, but it can be integrated into any vendor’s Diameter Signalling Controller.

The CAMEL protocol allows home networks to monitor and control calls made by a prepaid user in legacy networks, but “unfortunately, not enough effort has been spent in looking at inter-networking in CAMEL and diameter,” Ghosal said. He noted that postpaid subscribers often have all-you-can-eat plans that don’t require strict limitations on roaming, but the signalling for prepaid is far more complex, with authentication and validation with every phone call and the need to track whether a subscriber reaches their limit and needs to be cut off or can continue to be serviced. While prepaid is a smaller market segment than postpaid in the U.S., Ghosal pointed out, outside the U.S. the majority of users in a market may very well be prepaid subscribers.

Ghosal said that at some point, Diametric will probably put the work it has done on CAMEL/WIN-to-diameter mapping in the public domain, “but it’s a little early for that right now.”

“To built these specs, you need to have a very, very deep understanding of not just the message flow, but what each part of the message does,” Ghosal said. “Since we come from that background, we know.”