Case studies

Preparation Is not Just Sensible, but Essential

Bringing three products together to enable VoLTE roaming.

About the client

Under NDA.

Regions served

South America

Provided solutions


The customer was evolving from 3G to 4G mobile networks aiming particularly to provide VoLTE calls, who will benefit from high-definition speech quality and shorter connection setup times. This reflects global trends, with most providers shutting down their outdated 2G and 3G legacy networks, to free up cash and radio spectrum capacity in readiness for moving toward 5G.

With network operators around the world moving to 4G and VoLTE calling – particularly in the US, the destination of choice for 1.5 million Colombian travelers in 2021 according to Statista, and therefore a key market – the customer was keen to offer a higher-quality VoLTE service to its roaming subscribers. The customer also recognized some potential pitfalls, which could lead to poorer service quality and the risk of losing subscribers.

First, when VoLTE roaming subscribers are connected to a local network, the choice is made intelligently, based on services, quality, costs, and underlying VoLTE agreements. Subscribers roaming on VoLTE could therefore experience a lower level of service than on legacy networks if VoLTE Steering of Roaming (SoR) is not properly accounted for. Furthermore, with wholesale pricing for Circuit Switch calls being typically five times that for VoLTE, margins are reduced when roaming calls are made on non-VoLTE connections – also generating a financial impact to operators.

Second, providers have a regulatory duty to alert end-users with a Welcome SMS alert when connecting to a roaming network and communicate the applicable roaming fees. On a VoLTE network, if the connection is not detected, no Welcome SMS message is triggered, and regulations will not be met.

Third, subscribers dialing home from abroad risk making mistakes by not using the right international dialing codes and calling local home numbers instead, or have many short codes for value-added services not being recognized at all by providers abroad. Typically, 17% of local numbers and 100% of short-code numbers are expected to fail. However, when it comes to VoLTE, calls are redirected to the home network provider, as per the S8 Home Routing model (S8HR), and the home network faces the challenge of providing the best experience to its subscribers by correcting their calls as appropriate.

Meanwhile, the customer decided to address the above challenges using a virtualized platform. Transitioning from physical hardware in this way improves operational efficiency and helps them reduce their overall TCO.



The solution drew on three of our roaming products for Steering of Roaming, Welcome SMS and Call Correction, to address the key issues listed above, and provide, in total, a solution that would provide the customer’s subscribers a reliable and consistently high-quality service when roaming on VoLTE networks.

In addition to complying with roaming guidelines, TOMIA’s IPN can consider commercial relationships with roaming partners, so, if the customer’s parent company has negotiated a better wholesale rate or traffic deal with one preferred partner, it can also influence the IPN’s network selection. Particularly, it can steer VoLTE-capable devices to VoLTE networks and take advantage of much lower wholesale pricing.

To ensure the customer’s compliance with its national regulator, we used our Sparx campaign management tool to send a VoLTE Welcome SMS, as well as personalized, timed and context-driven campaigns whenever the subscriber connects to a new roaming network.

We spent the first month of the project gathering information to understand the specifics of the customer’s systems and discussing the approach, before installing the products and, most importantly, integrating them into the customer’s network. The greatest complexity arose – as usual – from the many different data flows, between multiple network elements that needed integration.



With the customer planning to shut down its 2G network by the end of 2023, and 3G by end-2025, careful advanced preparation like this is not just sensible, but essential.

The solution goes live in the next few weeks, and is set to deliver a number of clear benefits:

  • Regulatory and reputational. The customer will comply with the requirement to deliver a Welcome SMS and tariff information to roamers arriving at their travel destinations, avoiding fines and customer complaints.
  • Revenue. Wholesale cost optimization by steering VoLTE capable devices to VoLTE networks (i.e. lower wholesale prices for voice calls). Also, completing misdialed calls contributes additional retail revenue, and avoids subscribers resorting to using local SIM cards.
  • Operational. By exploiting the advantages of a virtualized environment, the customer will have the agility to adapt to new demands, and also reduce its overall total cost of ownership.  
  • Service delivery. Subscribers will benefit from continuity of the voice service, as well as enjoy the same experience when roaming as they do at home – notably in the USA, the most popular travel destination for Colombians.
From our client

Nam vulputate erat sed ipsum convallis, vitae egestas justo fringilla. Integer in rutrum nibh. Nulla eu urna egestas, venenatis enim a, imperdiet magna. Aenean a nisl accumsan, varius odio commodo, egestas purus. Vivamus accumsan erat felis, in tempus sapien vehicula at. In et lacinia est, non malesuada quam.

Maison John

Chief Technology Officer
Our customers

Case studies

VoLTE Is Vital to Ensure Continuity of Voice Services

Be ready for the 2G/3G networks sunset with no interruption to service.

Read the Success Story
Pain-Free Calling Home Process

Using VoLTE VHE to help roaming subscribers dial home as if they’d never left.

Read the Success Story
5G NSA Analytics to Improve Roaming QoS

Analytics plays a fundamental role in measuring and ensuring SLAs.

Read the Success Story

Interested in learning more?

Connect with a TOMIA expert today

Contact Us