How does mobile roaming work?
Roaming is defined as the ability for a cellular customer to automatically make and receive voice calls, send and receive data, or access other services when travelling outside the geographical coverage area of the home network, by means of using a network in the area visited.
Roaming is technically supported by mobility management, authentication and billing procedures. Establishing roaming between network operators is based on - and the commercial terms are contained in - Roaming Agreements.
If the network visited is outside the home country, this is known as International Roaming.
GSM Roaming, which involves roaming between GSM networks, offers the convenience of a single number, a single bill and a single phone with worldwide access to over 210 countries. The convenience of GSM Roaming has been a key driver behind the global success of the GSM Platform.
When abroad and “Calling Home”
What actually happens when you “Call Home”, and what are you paying for?
- When abroad and “Calling Home” to a friend, your call is managed by the host operator.
- The host operator passes the call via 'international transit' to your home operator.
- Your home operator connects you to your friend’s operator and establishes your call.
Who pays for what?
Steps 1 and 2 The host operator charges your home operator a wholesale rate which includes the interconnection costs (“International Transit” and costs for terminating the call) and its own network costs.
What you pay
Your next bill will include the above charges, plus other costs sustained by your operator (i.e. commercial costs, overhead costs, IT costs), plus a “profit margin” applied by your operator.
When abroad and being called from home
When a friend calls you from your home country, you are charged an international roaming price.
- A friend calls you on your mobile phone while you're roaming.
- His operator routes the call initially to your home operator (which may or may not be the same).
- Your home operator forwards the call to the host operator you are currently roaming on in the destination country, via 'international transit'.
- The host operator receives the forwarded call, connects you using its network and establishes your friend’s originated call.
Who pays for what?
Step 1 Your friend will be charged a normal call by his home operator for calling you.
Steps 2 and 3 Your home operator will charge you a tariff which includes inter alia the international transit fees to forward the call to you in the destination country and the cost for terminating the call on the host network.
Your friend pays the standard national rate (step 1).
You as a roamer pay the above charges (steps 2/3), plus other costs (i.e. commercial costs, overhead costs, IT costs), plus any additional charge to provide a reasonable return on investment by your home operator.