Roaming is a general term in wireless telecommunications that refers to the extending of connectivity service in a location that is different from the home location where the service was registered. The term "roaming" originates from the GSM (Global System for Mobile Communications Association) sphere. Traditional GSM Roaming is defined (cf. GSM Association Permanent Reference Document AA.39) as 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. This can be done by using a communication terminal or else just by using the subscriber identity in the visited network. Roaming is technically supported by mobility management, authentication, authorization and billing procedures. This article or section is in need of attention from an expert on the subject. ... Telecommunication involves the transmission of signals over a distance for the purpose of communication. ... The Global System for Mobile communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. ... A cellular network is a radio network made up of a number of radio cells (or just cells) each served by a fixed transmitter, normally known as a cell site or base station. ... A telecommunications network is a network of telecommunications links arranged so that messages may be passed from one part of the network to another over multiple links. ... Authentication (from Greek αυθεντικός; real or genuine, from authentes; author) is the act of establishing or confirming something (or someone) as authentic, that is, that claims made by or about the thing are true. ... In security engineering and computer security, authorization, is a part of the operating system that protects computer resources by only allowing those resources to be used by resource consumers that have been granted authority to use them. ... Billing may mean: The process of sending accounts to customers for goods or services is called billing. ...

Roaming in general

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, such as e.g. WLAN (Wireless Local Area Network) or GSM. Device equipment and functionality, such as SIM card capability, antenna and network interfaces, and power management, determine the access possibilities. The notebook is connected to the wireless access point using a PCMCIA wireless card. ... The Global System for Mobile communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. ... A Cingular Wireless mini SIM card. ... A yagi antenna Most simply, an antenna is an electronic component designed to send or receive radio waves. ... An interface defines the communication boundary between two entities, such as a piece of software, a hardware device, or a user. ... Power management is a feature of some electrical appliances, especially copiers and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power state after a period of inactivity. ...

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.
• SIM-based roaming: GSM subscriber roams onto a Public WLAN operated by 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.
• Username/password based roaming: GSM subscriber roams onto a Public WLAN operated by another Operator who has a roaming agreement with their GSM Operator.

Although these user/network scenarios focus on roaming from GSM Network Operator's network(s), clearly roaming can be bi-directional, i.e. from Public WLAN Operators to GSM Networks. Traditional roaming in networks of the same standard, e.g. from a WLAN to a WLAN or a GSM network to a GSM network, has already been described above and is likewise defined by the foreignness of the network based on the type of subscriber entry in the home subscriber register. The Global System for Mobile communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. ... The notebook is connected to the wireless access point using a PCMCIA wireless card. ...

In terms of user service scenarios, the user can have access to the same set of services, irrespective of access type. However, differentiation also exists. Service scenarios may include access to a range of different services, including:

• Access to corporate Intranet services;
• Access to operator walled garden services; and
• Access to public Internet.

In the case of session continuity, seamless access to these services across different access types is provided. An intranet is a private computer network that uses Internet protocols, network connectivity, and possibly the public telecommunication system to securely share part of an organizations information or operations with its employees. ...

Home and visited networks

The differentiation between home network and visited network is technically given by the type of subscriber entry in a specific network. If a subscriber has no entry in the home subscriber register of the network (e.g. Home Location Register (HLR) in GSM networks or local customer database in WLANs), the required subscriber data must first be requested by the visited network e.g. from the subscriber's home network in order that the subscriber can be authenticated and any authorization for using the network services can be checked. The "visiting" subscriber acquires an entry in a user database of the visited network (e.g. Visited Location Register (VLR)) and the authorized network services are enabled. For the roaming procedure in practice, the possibility of assigning the subscriber data is always indispensable in order that authentication, authorization and billing of the subscriber can be performed in the corresponding network. Thus, the term roaming is not linked to a specific network standard, but rather to the type of subscriber entry in the home subscriber register of the mobile radio network. If a subscriber can use his personal service profile, which he uses in the home network, in the visited network as well, this is also referred to as Global Service Roaming Capability. The GSM Core network is the heart of a GSM system, the most common mobile phone system in the world. ... The Global System for Mobile communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. ... The notebook is connected to the wireless access point using a PCMCIA wireless card. ... Authentication (from Greek αυθεντικός; real or genuine, from authentes; author) is the act of establishing or confirming something (or someone) as authentic, that is, that claims made by or about the thing are true. ... In security engineering and computer security, authorization, is a part of the operating system that protects computer resources by only allowing those resources to be used by resource consumers that have been granted authority to use them. ... The GSM Core network is the heart of a GSM system, the most common mobile phone system in the world. ... Authentication (from Greek αυθεντικός; real or genuine, from authentes; author) is the act of establishing or confirming something (or someone) as authentic, that is, that claims made by or about the thing are true. ... In security engineering and computer security, authorization, is a part of the operating system that protects computer resources by only allowing those resources to be used by resource consumers that have been granted authority to use them. ... Billing may mean: The process of sending accounts to customers for goods or services is called billing. ...

Roaming Agreements

The legal roaming business aspects negotiated between the roaming partners for billing of the services obtained are usually stipulated in so called roaming agreements. The GSM Association broadly outlines the content of such roaming agreements in standardized form for its members. For the legal aspects of authentication, authorization and billing of the visiting subscriber, the roaming agreements typically can comprise minimal safety standards, as e.g. location update procedures or financial security or warranty procedures. The Global System for Mobile communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. ... Authentication (from Greek αυθεντικός; real or genuine, from authentes; author) is the act of establishing or confirming something (or someone) as authentic, that is, that claims made by or about the thing are true. ... In security engineering and computer security, authorization, is a part of the operating system that protects computer resources by only allowing those resources to be used by resource consumers that have been granted authority to use them. ... Billing may mean: The process of sending accounts to customers for goods or services is called billing. ... Mobility Management is one of the major functions of a GSM or a UMTS network that allows mobile phones to work. ...

The roaming process

The details of the roaming process differ among types of cellular networks, but in general, the process resembles the following: A cellular network is a radio network made up of a number of radio cells (or just cells) each served by a fixed transmitter, normally known as a cell site or base station. ...

1. When the mobile device is turned on or is transferred via a handover to the network, this new "visited" network sees the device, notices that it is not registered with its own system, and attempts to identify its home network. If there is no roaming agreement between the two networks, maintenance of service is impossible, and service is denied by the visited network.
2. The visited network contacts the home network and requests service information (including whether or not the mobile should be allowed to roam) about the roaming device using the IMSI number.
3. If successful, the visited network begins to maintain a temporary subscriber record for the device. Likewise, the home network updates its information to indicate that the mobile is on the host network so that any information sent to that device can be correctly routed.

If a call is made to a roaming mobile, the public telephone network routes the call to the phone's registered service provider, who then must route it to the visited network. That network must then provide an internal temporary phone number to the mobile. Once this number is defined, the home network forwards the incoming call to the temporary phone number, which terminates at the host network and is forwarded to the mobile. In telecommunication, the term handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another. ... IMSI IMSI is an acronym for International Mobile Subscriber Identity. ... The public switched telephone network (PSTN) is the concatenation of the worlds public circuit-switched telephone networks, in much the same way that the Internet is the concatenation of the worlds public IP-based packet-switched networks. ... It has been suggested that Routing protocol be merged into this article or section. ...

In order that a subscriber is able to "latch" on to a visited network, a roaming agreement needs to be in place between the visited network and the home network. This agreement is established after a series of testing processes called IREG and TADIG. While the IREG testing is to test the proper functioning of the established communication links, the TADIG testing is to check the billability of the calls.

The usage by a subscriber in a visited network is captured in a file called the TAP (Transferred Account Procedure) for GSM / CIBER (Cellular Intercarrier Billing Exchange Roamer) for CDMA, AMPS etc... file and is transferred to the home network. A TAP/CIBER file contains details of the calls made by the subscriber viz. location, calling party, called party, time of call and duration, etc. The TAP/CIBER files are rated as per the tariffs charged by the visited operator. The home operator then bills these calls to its subscribers and may charge a mark-up/tax applicable locally.

Tariffs

Roaming fees are traditionally charged on a per-minute basis and they are typically determined by the service provider's pricing plan. Several carriers in the United States have eliminated these fees in their nationwide pricing plans. All of the major carriers now offer pricing plans that allow consumers to purchase nationwide roaming-free minutes. However, carriers define "nationwide" in different ways. For example, some carriers define "nationwide" as anywhere in the U.S., whereas others define it as anywhere within the carrier's network.

An operator intending to provide roaming services to visitors publishes the tariffs that would be charged in his network at least sixty days prior to its implementation under normal situations. The visited operator tariffs may include tax, discounts etc. and would be based on duration in case of voice calls. For data calls, the charging may be based on the data volume sent and received. Some operators also charge a separate fee for call setup i.e. for the establishment of a call. This charge is called a Flagfall charge.

Additional notions and types of roaming

• Regional roaming:

This type of roaming refers to the ability of moving from one region to another region inside national coverage of the mobile operator. Initially, operators may have provide commercial offers restricted to a region (sometimes to a town). Due to the success of GSM and the decrease in cost, regional roaming is rarely offered to clients except in nations with wide geographic areas like the USA, Russia, India, etc., in which there are a number of regional operators.

• National roaming:

This type of roaming refers to the ability to move from one mobile operator to another in the same country. For example, a subscriber of T-Mobile USA who is allowed to roam on Cingular Wireless's service would have national roaming rights. For commercial and license reasons, this type of roaming is not allowed unless under very specific circumstances and under regulatory scrutiny. This has often taken place when a new company is assigned a mobile telephony license, to create a more competitive market by allowing the new entrant to offer coverage comparable to that of established operators (by requiring the existing operators to allow roaming while the new entrant has time to build up its own network). In a country like India, where the number of regional operators is high and the country is divided into circles, this type of roaming is altogether too common^{[citation needed]}. T-Mobile logo T-Mobile is a multinational mobile phone operator. ... “AT&T Wireless” redirects here. ...

• International roaming:

This type of roaming refers to the ability to move to a foreign service provider's network. It is, consequently, of particular interest to international tourists and business travellers.

Broadly speaking, international roaming is easiest using the GSM standard, as it is used by over 80% of the world's mobile operators. However, even then, there may be problems, since countries have allocated different frequency bands for GSM communications (there are two groups of countries: most GSM countries use 900/1800 MHz, but the United States and some other countries in the Americas have allocated 850/1900 MHz): for a phone to work in a country with a different frequency allocation, it must support one or both of that country's frequencies, and thus be tri or quad band. Triband phones (also known as tri-band or tri-mode) are mobile phones that support the GSM 900/1800/1900 MHz bands, or alternatively the 850/1800/1900 bands. ... Quad band literally means four (4) bands. ...

• Inter-standards roaming:

This type of roaming refers to the ability to move seamlessly between mobile networks of different technologies.

Since mobile communication technologies have evolved independently across continents, there is significant challenge in achieving seamless roaming across these technologies. Typically, these technologies were implemented in accordance with technological standards laid down by different industry bodies and hence the name.

A number of the standards making industry bodies have come together to define and achieve interoperability between the technologies as a means to achieve inter-standards roaming. This is currently an ongoing effort.

• Mobile Signature Roaming:

The concept of Mobile signature Roaming is: an AP should be able to get a Mobile Signature from any end-user, even if the AP and the end-user have not contracted a commercial relationship with the same MSSP. Otherwise, an AP would have to build commercial terms with as many MSSPs as possible, and this might be a cost burden. This means that a Mobile Signature transaction issued by an Application Provider should be able to reach the appropriate MSSP, and this should be transparent for the AP(reference). The concept of Mobile signature Roaming is: an AP should be able to get a Mobile Signature from any enduser, even if the AP and the enduser have not contracted a commercial relationship with the same MSSP. Otherwise, an AP would have to build commercial terms with as many MSSPs... AP may refer to: Andhra Pradesh, A state in the Republic of India Associated Press, an American news agency AP, the United States postal abbreviation for U.S. military personnel in the Pacific Ocean region AP, the U.S. Navy hull classification symbol for transport support ships A&P, the... There are very few or no other articles that link to this one. ... AP may refer to: Andhra Pradesh, A state in the Republic of India Associated Press, an American news agency AP, the United States postal abbreviation for U.S. military personnel in the Pacific Ocean region AP, the U.S. Navy hull classification symbol for transport support ships A&P, the... An MSSP (managed security service provider) is an Internet service provider (ISP) that provides an organization with some amount of network security management, which may include virus blocking, spam blocking, intrusion detection, firewalls, and virtual private network (VPN) management. ... AP may refer to: Andhra Pradesh, A state in the Republic of India Associated Press, an American news agency AP, the United States postal abbreviation for U.S. military personnel in the Pacific Ocean region AP, the U.S. Navy hull classification symbol for transport support ships A&P, the... An MSSP (managed security service provider) is an Internet service provider (ISP) that provides an organization with some amount of network security management, which may include virus blocking, spam blocking, intrusion detection, firewalls, and virtual private network (VPN) management. ... There are very few or no other articles that link to this one. ... An MSSP (managed security service provider) is an Internet service provider (ISP) that provides an organization with some amount of network security management, which may include virus blocking, spam blocking, intrusion detection, firewalls, and virtual private network (VPN) management. ... AP may refer to: Andhra Pradesh, A state in the Republic of India Associated Press, an American news agency AP, the United States postal abbreviation for U.S. military personnel in the Pacific Ocean region AP, the U.S. Navy hull classification symbol for transport support ships A&P, the...

Roaming in Europe

In the European Union, the Regulation on roaming charges within the European Union is in force since June 30, 2007, forcing service providers to lower their roaming fees across the 27-member bloc. The regulation is setting a price cap of €0.49 (€0.46 in 2008, €0.43 in 2009) per minute for outgoing calls, and €0.24 (€0.22 in 2008, €0.19 in 2009) per minute for incoming calls - excluding tax.^[1] The Regulation (EC) No 717/2007 of the European Parliament and of the Council of 27 June 2007 on roaming on public mobile telephone networks within the Community and amending Directive 2002/21/EC is a regulation by the European Commission, primarily backed by Viviane Reding, which regulates the charges... is the 181st day of the year (182nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is now the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...

References

1. ^ [1], 'New caps on roaming charges in place for August', 08 June 2007

See also

• 802.11
• 802.11r
• Home Location Register
• Handoff
• Mobile IP
• Mobile phone
• Mobility management
• Roaming Sim
• Transferred Account Procedure
• UMTS frequency bands
• Vertical handoff
• Visiting Location Register

IEEE 802. ... This article may be too technical for most readers to understand. ... The GSM Core network is the heart of a GSM system, the most common mobile phone system in the world. ... In telecommunication, the term handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another. ... Mobile IP is an Internet Engineering Task Force (IETF) standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining their permanent IP address. ... Mobility Management is one of the major functions of a GSM or a UMTS network that allows mobile phones to work. ... UMTS frequency bands or frequency ranges are the radio spectrum frequencies designated for the operation of the UMTS / HSDPA / HSUPA / HSPA+ system for mobile phones. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The GSM Core network is the heart of a GSM system, the most common mobile phone system in the world. ...

Standardisation Organizations

• ETSI website, European Telecommunications Standards Institute.
• Direct access to ETSI standards publications.
• GSM website, Global System for Mobile communications by the GSM Association (GSMA)

The European Telecommunications Standards Institute (ETSI) is a standardization organization of the telecommunications industry (equipment makers and network operators) in Europe, with worldwide projection. ... Not to be confused with Get Some Mates The Global System for Mobile Communications (GSM) is the most popular standard for mobile phones in the world. ...

External links

• Roaming - Using my mobile abroad : are prices dropping ? - European Commission
• Mobile Europe describes how the roaming industry will cope with pending EU legislation and the arrival of mobile VoIP
• International Forum on ANSI-41 Standards Technology - Lists some of the issues in Inter-standards roaming