Roaming SIM

Roaming SIMs can be defined as mobile phone SIM cards that operate on more than one network within their home country. They currently have two main applications, least cost call routing for roaming mobile calls and machine to machine.

Using a normal network locked SIM, travellers for instance, can use their own mobile phone (if it's enabled for roaming), in any country that has a roaming agreement with their home network. This manifests itself to most users when they receive a text message welcoming the traveller to a local network. However, once they return home their SIM will only work on the network with which they have a contract.

A roaming SIM however, also known as a global roaming SIM, will work with which ever network it can detect, at home or abroad.

Roaming mobile calls

The use of roaming SIM cards in its most common form is in normal voice applications such as mobile phone calls. The common application of Roaming SIMs for voice is where mobile calls are automatically routed to, and made on a least cost network. This typically means that incoming calls are free, no matter which network a mobile user is on. This also means that a caller enjoys the cheapest cost when making a call, significantly reducing call costs, especially compared to normal network charges for International Roaming.

Global roaming SIMs are very often combined with callback technology, whereby the user dials a number in the normal way, but the call is intercepted by an application on the SIM card and turned from an outbound call to an inbound call which the user answers. This is to take advantage of the fact that inbound call charges are typically lower than outbound ones. Telecom North America is one of the providers in the US using this technology.

Some providers achieve this automatic call interception and callback by encoding a program onto the Sim card. For example BackChat Mobile in Australia utilises this method to intercept the call and send a network command to trigger the callback.

Increasingly, data services are being added to roaming SIm cards to reduce the cost of roaming data charges.

Machine to machine

This technology is also used in a number of machine to machine applications where devices communicate with one another, for example in vehicle tracking systems, amongst other things, where complete network coverage is required but can only be achieved by using all the available networks. A roaming SIM, for example provided in the US by Neometry, can switch to any network, ensuring the best coverage. The cheap calls associated with Roaming SIMS are also paramount to enable certain machine to machine applications to be economically viable. It is anticipated that our exposure to Roaming SIMS, applied in a range of scenarios, will become prevalent as more and more applications for them are brought to market.

Alternatives

For some applications (particularly where regular travel between two countries is the main purpose) a Dual SIM can be considered as an alternative.