Cables, fibre and interconnection points give African networks their paths between markets. Wholesale roaming and international voice depend on a further layer, which decides whether traffic can use those paths and how that traffic is accounted for. In a group with several mobile operators, that layer can be handled subsidiary by subsidiary or centrally.
Between a signed agreement and the first roamer
Inter-operator tariffs (IOTs) are the wholesale rates a visited operator charges a home operator for allowing its subscribers to roam on the visited network. The two operators negotiate them, and the service itself still has to be proven on both networks before the first roamer connects.
In VoLTE roaming, that proof is specified by the GSMA’s IR.25, which lists test cases for IMS registration, calls between roaming subscribers and to local numbers, SMS, emergency calls, lawful interception and supplementary services. It sets prerequisites for the visited network and the home network, and provides for testing contacts and USIM data to be exchanged before testing begins.
Once the tests have been passed, the service is opened to subscribers, and the usage that follows is reconciled between the two partners.
Roaming for five mobile operators
Within Yas (formerly AXIAN Telecom), the IOTs and international roaming agreements of the five mobile operators, in Senegal, Togo, Tanzania, Madagascar and Comoros, are negotiated and managed centrally by Silver Links, the group’s wholesale carrier.
“Our centralised roaming model gives international partners a single point of contact to negotiate across Yas mobile operations.”
Mamadou Sellou Diallo
Head of Group Roaming, Silver Links
The technical side is coordinated centrally too. Service opening helps align each commercial agreement with the operational readiness of the networks. The reconciliation of roaming tariffs is centralised as well.
International partners deal with a more consistent interface across the group’s markets. Each partner’s own network still takes part in the testing and the reconciliation.
International voice through a dedicated gateway
The group’s international voice traffic goes through a dedicated International Voice Gateway, managed by Silver Links, the exclusive carrier of the Yas operating companies. The gateway is the group’s coordinated framework for international voice interconnections, traffic flows and the commercial conditions attached to them.
Voice performance depends on traffic volumes, routing efficiency, service quality, commercial conditions and carrier relationships. Each carrier relationship should answer a defined need, such as coverage, call quality, cost or commercial terms. Where the need is unclear, the route and its agreement should be reviewed.
The service layer is part of international connectivity
The infrastructure layer decides which paths exist and where traffic is exchanged, from submarine cable redundancy to IP transit and peering. The service layer decides what can travel over them, through the agreements, interconnections, tests and settlement that bind networks run by different operators. Judging a roaming or voice service means reading both together.
A 2025 European Commission study, conducted by MOZARK with nearly 50 SIM cards across 20 EU Member States, puts figures on the distance between what a visited network can offer and what a roamer receives. Download speeds were poorer than on the home network in 76% of test cases and poorer than on the visited network in 80%. The study covers European networks and does not identify the causes of the difference.
International voice is the other half of that service layer. International carriers and major mobile network operators can establish direct interconnections with the Silver Links wholesale platform for international voice traffic to and from the Yas operating companies.
