Mobile Roam

Mobile Roam


As the world shrinks, your mobile services expand

Your customers travel to the ends of the earth on business and pleasure – and they expect their mobile phones to work everywhere they go. BT enables you to provide the global mobile connection today’s expanding marketplace demands.

Forget about the headaches of multiple contracts and incompatible technology. We offer a managed service that evolves with the requirements of your organisation and your customers.

Key benefits

Delivering the freedom to roam

BT enables you to offer a more complete mobile communications infrastructure service to your customers. We can:

  • Maximise your roaming revenue potential by enabling you offering your customers a mobile communication package with a truly global reach.
  • Increase your revenue through our customer tailored charging structure either pay-per-message or a flat monthly fee, enabling more effective cost management and simplifying the billing process on your side.
  • Enable you to offer your customers enhanced service management and planning by utilizing BT’s proven business communication track record and capabilities.
  • Support you in building a long-term relationship with your roaming partners by providing tailored, scalable technology able to evolve with their needs.
  • Help you provide a one-stop-shop for all your customers’ mobile roaming requirements through our comprehensive service.

Key features

BT equips you for enhanced roaming

Be confident in the service you provide your customers. Through our comprehensive package, you will be able to offer them:

  • Robust communications relay: secure and resilient transit points.
  • Versatile connections: direct 64 kbit/s access to mobile communications, or indirect connections via a third-party operator.
  • SMS filtering: protection from unwanted messages.
  • 24/7 support: comprehensive technical assistance provided by our advanced UK network operations centre.
  • Proactive monitoring: additional peace of mind and consistently enhanced operations through our automated link assessments.
  • ITU-T/ANSI translation: seamless transatlantic connection to the US mobile signalling standard – offering an extremely valuable roaming route.

Detailed description

Consistent performance wherever you roam

BT Mobile Roam is an SS7 signalling service. It offers mobile network operators the opportunity to join a global inter-operator hub offering global network coverage in 199 countries. 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. To use the BT Mobile Roam service, however, the mobile network operator must have signalling access to BT’s switches (UK or Europe), either directly or indirectly via a third network (e.g. a local carrier). BT then acts as a signalling hub to roaming partners around the globe.

BT Mobile Roam provides access to the networks of 622 GSM mobile operators in most of the world’s countries, and can add new networks as required. Through us, operators can confidently negotiate roaming agreements secure in the knowledge that signalling will be supported.

Every SS7 link in the BT network acts as a signalling relay point (SRP). The capacity and quality of each one is continuously monitored by industry recognised systems, such as Tektronix GeoProbe and SIGNET. These links use signalling connection control parts (SCCP) to provide secure and robust message transfer, offering yet more consistency and reliability.

BT does not allow use of its Signalling Transfer Point (STP) capability to forward roaming messages. In other words, only planned and agreed routes are possible. These measures maintain network integrity and capacity control in order to provide consistent service quality.

International Telecommunication Standardisation Sector ITU-T and American National Standards Institute (ANSI) signalling translation is available as part of our service (known as BT Roam Translate). This provides a high-quality, cost-effective means of connection throughout North American, and the financial benefits of this highly lucrative transatlantic roaming route.

We also understand that the migration of existing connections is a vital consideration for mobile network operators. Therefore, BT provides both project and network management support for throughout the design, implementation, testing and maintenance of our service.

Technical specifications

Global reach for all your customers

In order to offer a truly synchronised ANSI and ITU-T network, roaming, addressing and message format translation is required. The BT Mobile Roam ITU-T/ANSI signalling translation service provides this protocol converter. We can then enable the two systems to communicate seamlessly.

BT Mobile Roam ITU-T/ANSI translation feature uses a highly resilient transatlantic connection. Four routed T1 lines carry signals over two transatlantic cables and three US domestic carriers.

The translation is performed in the US in a fully-mated Tandem environment ensuring ultra-high availability and reliability. The majority of traffic in North America is delivered over direct connections and in all cases is routed to provide the best possible availability.

Both symmetric and asymmetric routing is supported – the complexity of wireless number transmission renders asymmetric routing an unavoidable reality in multiple service provider markets. Our global reach and experience ensures we can work with all carriers involved to ensure the optimum service is provided.

The migration process includes:

Step 1: Once contracts are signed and roaming partner lists provided, BT creates a detailed network plan in consultation with the mobile network operator.

This plan provides a detailed implementation process, setting out each step of the migration and providing timeframes.

For each mobile network operator roaming partner, BT provides details of which BT nodes to send traffic to. This can either be as primary, secondary routes or shared routes – depending on your individual need and capability.

Migration is normally carried out in the following way:

  • Outbound traffic from mobile network operator is split into five groups of roaming partners to be migrated seven days apart.
  • Inbound traffic migration begins with all roaming partners and signalling providers asked to change their routing to direct mobile network operator traffic to BT.

Step 2: The interconnect network is then established and tested.

Wherever possible, existing bandwidth is used to connect to the nearest BT nodes. This maximises time and reduces the cost to our customer. BT uses dedicated GSM signalling links from our Point of Presence (PoP) to two or more of the eight BT SCCP nodes. The mobile network operator can also connect directly to our Signal Transfer Point (STP) if preferred.

Step 3: One small network will be migrated over to the BT network and tested. BT’s network account manager and a dedicated project manager provide support where necessary as the end-to-end connection is established. Once traffic is successfully flowing in both directions, this test network is monitored for one week before migration of larger roaming partners begins.

Step 4: The remaining networks are migrated according to the implementation plan. Capacity is carefully monitored during this process, and the network augmented if required.

Note that outbound routing is under both mobile network operator and BT control. Return routing, however, is not. We will need an updated IR21 and letter of authority to approach other signalling carriers to migrate return traffic via BT.

BT’s experience is that full migration of more than 200 roaming partners takes three months. If only large roaming partners are to be migrated to BT, this can take between four to six weeks to migrate fully.

We work closely with you during this period to monitor the migration of roaming partners – and we send reminders to those that are slow in moving the return traffic.

Why BT

Where we roam others follow

BT Mobile Roam makes use of our extensive SS7 signalling network, which evolved out of our international voice business. International GSM roaming started in early 1991 and now signalling traffic from BT Mobile Roam dominates the SS7 network in terms of capacity and complexity.

BT has been running the SS7 GSM network for more than 17 years, and has access to a large pool of knowledge and resources in order to support our customers. In addition, BT has invested extensively in its network monitoring, planning, people and capacity management positions. As a result, we are not only a vital signalling network for BT’s GSM mobile network operator customers, but also the same network that supports BT voice business.


Available globally. Please contact your BT account manager for specific country information.



Mobile Roam brochure


A unified roaming service offering your customers enhanced mobile connection around the world.