July 6, 2021

Future of Roaming: Data-Driven Control

Every industry is embracing the use of data to make the best possible decisions, and the telco space is no different. A more globalised, contextualised view of roaming traffic is key to the highest levels of quality and accuracy, especially moving to VoLTE and 5G roaming. 

There has always been a need to control roaming. Operators want to ensure their roamers roam with the most commercially favourable networks, or that their subscribers roam with a particular network where the quality of service is expected to be higher. They normally assert this control using a Steering of Roaming (SoR) system. An SoR system will typically operate in 2 different ways:

  • Manipulate the MAP/Diameter signalling during a subscriber roaming registration to force the subscriber to register with a particular preferred network
  • Send OTA commands to update the preferred PLMN list on the SIM card to tell the device which network it should register with.

Control and Steering by Data

With 5G Standalone coming, SoR systems will need to support this as well, but conceptually the manner in which the device is steered to the desired network remains the same.

The world of roaming has evolved significantly since SoR systems were first deployed. Back then it was all about voice and SMS. Today, it is extremely data-centric, with additional complexities introduced by new technologies like VoLTE. Operators need a level of control on roaming that reflects these new realities.

SoR systems, as they are, remain entirely capable of controlling which networks a subscriber is roaming on. The techniques described above are effective in getting the subscriber to the correct network. 

But what is the correct network? 

This is not as clear as it may once have been. To really understand which network is “correct”, a global view of roaming is needed. This global view should be used to arrive at a good data-driven decision about which network a subscriber should be steered towards. There is no one size fits all – each subscriber faces unique circumstances, and this must be considered in any decision about the right network for that subscriber. 

Typically an SoR system makes decisions based on MAP and Diameter signalling. But this only tells part of the picture. If a subscriber is not able to get service on the preferred network, the SoR system can detect this based on MAP/Diameter signalling. It can then take immediate action to ensure that they can get service somewhere. But what if the subscriber fails to establish a data connection? Or they fail to register for VoLTE? From the SoR point of view, it has done its job of getting the subscriber to the right network, but it does not see further issues experienced by the subscriber. Ideally SoR would see such issues and take action to solve the problem. 

Global View of Data

This is where a global view of roaming is required. 

We need to be able to see everything that is happening in the roaming landscape to drive good decisions – visibility on a subset of protocols (MAP/Diameter) is no longer sufficient.

A global view of roaming means seeing all signalling and data related to roaming. This includes MAP and Diameter as we have today. It will include HTTP/2 when 5G Standalone is adopted for roaming. It includes GTP-C for setting up data sessions. It includes GTP-U for seeing services being used by roaming subscribers and volumes being used on each network. It includes SIP signalling for monitoring VoLTE registrations in the IMS. Any signalling related to roaming should be considered for detecting problems and making better decisions about how to control roaming. More data, with more context, and better decisions are needed for the benefit of the operator and for the benefit of their subscribers.

Use Cases

Let’s take a look at some use cases enabled by this kind of holistic roaming view:

Quality of Service

  • Subscribers that have a problem registering for VoLTE – if a subscriber roams to a VoLTE only network but fails to register in the IMS for VoLTE, this is a problem. Visibility on SIP allows for immediate action to be taken in such a case to alleviate the issue (see more here)
  • Subscribers that fail to establish a data tunnel – this is a major quality of experience issue for a subscriber. If this is detected, an immediate action should be taken to move that subscriber to a network where they can get data service.
  • Quality metrics per roaming partner allows automatically favouring networks providing a better quality of experience for our subscribers (see GRQ)

Commercial and Fraud

  • Visibility is enabled on what services are being used by roaming subscribers, eg. which OTT services are being used.
  • Silent Roamer Detection or High Data User Detection – subscriber classification can be made to enable further actions in an SoR system, or to send an SMS to silent roamers, for example.
  • Visibility on calls made by roaming subscribers. Are these devices making high volumes of calls to high cost numbers? Such behaviour could be fraud related, and such calls could be detected and blocked.


  • Real-time decisions about usage per roaming partner. Traditionally decisions based on usage are done by TAP, which can be up to 30 days old. This is too late for taking meaningful actions. By analysing the signalling in real-time, issues in relation to usage volumes can be immediately detected and immediate action can be taken.
  • Visibility on the type of access provided to subscribers on each network – who is using 2G, 3G, 4G, 5G etc. This allows the operator to quickly see which roaming partners are providing the best roaming services to their subscribers, and may wish to favour this network going forward.
  • Automatic detection of IoT devices – the global view of roaming should be applied to both inbound and outbound roaming. Detection of IoT devices that are inbound roaming is important as these devices may be consuming resources but generating little revenue. This kind of detection will become important as billing models evolve in the coming years through the Billing and Charging Evolution(BCE).

These are a small subset of use cases enabled by acquiring such a global view of roaming, many other use cases could be imagined. With the increasing complexities involved in roaming, this kind of holistic view will become essential, along with the ability to take action on this intelligence. By using this data to make better informed decisions based on a complete view of the roaming landscape, we can ensure that roaming can always be optimised between commercial and quality requirements.

Data Roaming Solutions

The Cellusys Roam Insight product provides this global visibility of roaming. The platform provides powerful roaming analytics, and the integration of this module with the Cellusys Steering of Roaming Platform makes these analytics immediately actionable. 

Together these products offer operators a single point of visibility for roaming analytics, and a single point of control for roaming that will enable them to meet their roaming needs into the future.

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July 6, 2021