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BT uses outsourced network services from Epsilon to support its migration from TDM to IP and delivers IP-based Sigtran signalling for its growing mobile customer base

International communications services provider BT selected Epsilon to extend its IP signalling infrastructure and serve more mobile network operators (MNOs) on IP. It is in the midst of its migration from TDM to IP and was looking for a way to add new IP capabilities efficiently.

Almost all international network operators have begun their transition to an all-IP infrastructure but many are being challenged to make this transition seamless and cost-effective. IP offers them the ability to deliver new services and capture new revenue but managing both TDM and IP networks during this transition can be difficult and resource-intensive.

TDM is reliable and delivers valuable but declining revenue while in the mobile world LTE deployments are ushering in the need for new IP networks. Increasingly, MNOs want to use IP networks to deliver services and service providers like BT need to accelerate their adoption of IP and enable their customers with IP networking.


The challenge for BT was to offer MNOs more services on IP and deliver its Roam Connect service using IP-based Sigtran signalling rather than TDM. Signaling underpins voice and messaging services and MNOs often use wholesale providers like BT to connect these services globally.

The market for Sigtran signalling services is growing but at this point in time, it would be costly to overhaul its entire signalling infrastructure and then operate both TDM and IP-based signalling services. As IP is phased in and TDM phased out, both networks often have to be operated in parallel, which leads to cost-inefficiencies and a challenging environment for monetising new services.

It also needed a solution that could scale to match growth in its business as well as the on-going migration of TDM to IP amongst existing customers. The migration from TDM to IP has been happening for a long time but this is accelerating and service providers need to be prepared to scale up their services to match customer demand.

Overall, BT needed to expand its Sigtran signalling capabilities but do it in a way that was efficient, flexible and ready to grow with IP adoption. The key was to add these new capabilities without adding complexity to its operation.


Epsilon delivered outsourced TDM to IP conversion services that enable BT to offer more Sigtran signalling services to its customers. 
Its Roam Connect service offers mobile network operators the opportunity to join a global inter-operator hub offering global network coverage. Subscribers can then roam seamlessly between networks on both an inbound and outbound basis. The service is accessed either directly through terrestrial and satellite links, or indirectly through a third-party operator. 
By outsourcing TDM to IP conversion services to Epsilon, BT is able to support its hub approach and give customers greater choice in terms of network technology to interconnect with. The outsourced option means BT does not need CAPEX-intensive investments in IP infrastructure or allocated internal resource to developing these conversion services. It simplifies their approach to operating both TDM and IP infrastructure while giving them the ability to scale up the service with growth.
When BT’s Sigtran signalling business reaches a size where it feels owning this infrastructure will deliver the required return on investment, it can take over the conversion services. With an outsourced solution, it can also continue to develop its IP infrastructure in parallel while Epsilon ensures that the customer only sees seamless service delivery.
One of the benefits for BT is the ability to offer satellite TDM offload to far-reaching African and Middle Eastern customers and give them the widest scope of technical solutions for rapid interconnection. This expands what BT can offer customers and will drive new business opportunities in the future.

Epsilon understands how to make the move from TDM-to-IP seamless and simple. They offered us a solution that was quickly deployed and ready to serve our growing IP customer base.

Mike BygateNew Voice Business Manager AT BT


  • Flexibility
    The Epsilon model allows BT the ability to change and develop as customer demand for IP increases and its business grows
  • Efficiency
    Using an outsourced solution means reducing demands on CAPEX and internal resource while increasing IP capabilities
  • Simplicity
    An outsourcing partner can add new capabilities without the need to design, build, and manage new infrastructure
  • Scalability
    As demand for IP services grow, Epsilon can scale its services to match its customer’s appetite for IP services
  • Time-to-Market
    An outsourced networking solution meant BT could integrate network capabilities into its offering rapidly and deliver services quickly
  • Experience
    Epsilon is supporting service providers around the world as they migrate from TDM to IP with a team of dedicated experts in IP

Network outsourcing accelerates the adoption and delivery of IP services and enables operators to monetise IP faster and more efficiently. The management of both TDM and IP networks in parallel can be challenging, as they require expertise and resource to operate. This is where Epsilon’s outsourcing model can streamline the migration and ensure the profitability of new IP services.

Jerzy SzlosarekCEO at Epsilon


As the adoption of IP continues, Epsilon is positioned to support operators with both TDM and IP services. While today operators may need support in delivering new IP services, they are also looking at efficient ways to begin decommissioning TDM networks.
When IP becomes the primary network technology, Epsilon is ready to support operators with outsourced TDM services that help to efficiently move to an all-IP world. End of life technologies are far more difficult to support internally and Epsilon has the expertise to manage this infrastructure on behalf of customers
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