Solving The 4G LTE Roaming Puzzle

Solving The 4G LTE Roaming Puzzle

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GSMA statistics reliably show there are approximately 800 GSM Operators worldwide with an additional 1,250 Mobile Virtual Network Operators (MVNOs). 606 operators have launched 4G LTE networks, with the GSMA predicting an increase of a third by the end of 2020.

With 4G LTE well on its way to becoming a ubiquitous service the coalescing of new and old technologies creates its own unique challenges. As with all new technology you cannot simply deploy it in a vacuum while simultaneously disregarding what’s gone before in the way of legacy technology, and this is especially true of the mobile industry where individual operators move at their own pace with 4G LTE deployment.

Take for example 4G subscribers that roam outside their home networks with roaming agreements on offer that are established over 3G. Large Tier 1 operators have their own immutable timetables for 4G rollout and more specifically 4G roaming support, so it would be up to the smaller players to support the 3G roaming on offer.

Conversely what operator or MVNO would want to miss out on offering roaming services and the associated lucrative revenue, much of which sustains MVNO’s and smaller MNO’s? In order to maximise revenue you would ideally want to support roaming on both 3G and 4G technology.

Squire Technologies have been working with an operator in Africa who has deployed a 4G LTE network alongside their existing 3G GSM network. They ran into the roaming problem described above, i.e. that the roaming agreements in place are only running over 3G. Having invested heavily to attract 4G subscribers it fast becomes a limited service if in turn these subscribers cannot easily roam outside their home network!

The Solution

At its heart the problem is that 3G networks run on the SS7 protocol and 4G LTE networks run on the Diameter protocol. What is required is a bridge between these technologies, one that will seamlessly allow the sharing of policy, charging and authentication information. The product that supplies this functionality is a Diameter Signalling Controller (DSC) or more accurately the Interworking Function (IWF) which is a sub component of the DSC.

Squire Technologies client required several key aspects from their DSC product the SVI-DSC.


It is still early days for the 4G launch and hence the number of 4G subscribers is still relatively low. Furthermore the percentage of 4G sub-scribers that roam is approximately 10%. The key for Squire's client was that they wanted to start with support for a relatively small amount of roaming transactions with the ability to scale as and when demand increases. The Squire Technologies SVI-DSC provides this allowing for growth through a flexible licensing option.


This covers both the product and services. You are essentially connecting SS7, the established thirty-year old legacy technology with leading edge Diameter networks. Both technologies are well specified, and at the transport layer at least, interconnect is well tested. The devil of course is in the detail with the higher layers SS7 MAP/CAMEL to Diameter where you are exchanging the relevant policy, charging and authentication information. This interoperability is for the best part specified, however as with all specifications those products implemented are the vendor’s best interpretation of the specifications. To mitigate for this at a product level you need powerful message manipulation engines that allow you to pull apart messages and reassemble them in the correct format.

Cost Effective

The majority of 4G LTE deployments today are provided by the Tier 1 product vendors. They supply a full end-to-end solution from the radio interface, the EPC infrastructure to the OSS/BSS layer. As we have experienced with 3G networks those networks that opt for a single vendor can find themselves squeezed by the vendor on single function, edge of network components especially when a service is starting small. Squire Technologies recognise that network components like this can be delivered cost effectively with a clear upgrade path when the solution begins to scale.


Further to this in the legacy networks you may find part of the roaming process, in addition to the SS7 authentication and authorisation messaging, involves additional steps. There may be lookups or enquiries to a legacy billing, routing or OSS platform over say SOAP, RADIUS, SQL or LDAP. To solve such issues the SVI-DSC supports the Service Creation Toolkit. Messages triggered at the SVI-DSC are sent to the Python based toolkit where message decode, manipulation and logic can be applied to deliver the required message sequence. This sequencing can be designed and tested offline enabling smooth and rapid rollout onto the live environment.

In terms of the services provided to commission the equipment it helps to have an outfit that has been providing specialist signalling interconnect for over 15 years.

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