Roaming

Roaming is a wireless telecommunication term typically used with mobile devices, such as mobile phones. It refers to a mobile phone being used outside the range of its native network and connecting to another available cell network. In more technical terms, roaming refers to the ability for a cellular customer to automatically make and receive voice calls, send and receive data, or access other services, including home data services, when travelling outside the geographical coverage area of the home network, by means of using a visited network. For example: should a subscriber travel beyond their cell phone company's transmitter range, their cell phone would automatically hop onto another phone company's service, if available. The process is supported by the Telecommunication processes of mobility management, authentication, authorization and accounting billing procedures (known as AAA or 'triple A'). Roaming is divided into "SIM-based roaming" and "username/password-based roaming", whereby the technical term "roaming" also encompasses roaming between networks of different network standards, e.g. WLAN (Wireless Local Area Network) or GSM (Global System for Mobile Communications). Device equipment and functionality, such as SIM card capability, antenna and network interfaces, and power management, determine the access possibilities. Using the example of WLAN/GSM roaming, the following scenarios can be differentiated (cf. GSM Association Permanent Reference Document AA.39): SIM-based (roaming): GSM subscriber roams onto a public WLAN operated by: their GSM operator, or another operator who has a roaming agreement with their GSM operator. Username/password based roaming: GSM subscriber roams onto a public WLAN operated by: their GSM operator, or another operator who has a roaming agreement with their GSM operator. Although these user/network scenarios focus on roaming from GSM network operator's networks, clearly roaming can be bi-directional, i.e. from public WLAN operators to GSM networks.