When traveling abroad and wanting to stay connected using your familiar mobile phone number, or checking emails in Outlook Express from distant islands…, you might consider the service referred to as “roaming.”
This is a general term in telecommunications that refers to the expanded service area at a location that is not the original registration site. Roaming occurs when a subscriber of one service provider (SP) uses the infrastructure of another SP. This second SP does not have any service or financial agreement with the subscriber regarding the receipt and transmission of information but works with the first SP to support the user.
The focus of roaming today is on mobile networks and the Internet.
Roaming in Mobile Networks
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| Source: Rentmobilephone |
In many cases, roaming can occur in the original registration area of the phone when it transmits information through a tower of another SP—when the signal from the original SP is too weak or the number of callers is too high.
In different mobile networks, the roaming process will vary, but it generally follows this outline:
– When the mobile device is turned on or handed over to a network, the “visited” network “sees” the device and checks if it is on the registered list while attempting to identify its “home” network. If the two networks do not have an agreement to interconnect, the service cannot be maintained, and the visited network will deny access.
– In an accepted scenario, the visited network will contact the home network and request service information about the roaming device using its IMSI (International Mobile Subscriber Identity), including whether the device is allowed to roam.
– If successful, the visited network begins to maintain temporary subscriber status for the device. Meanwhile, the home network updates its information to confirm that the device is managed on the server, and the information sent to that device is ensured to be transmitted accurately.
If there is an incoming call to the roaming phone, the public telephone network will direct it to the registered SP. This SP must then forward it to the visited network (which has an agreed service). The visited network will provide a temporary internal phone number for the mobile device. Once this number is confirmed, the home network will forward incoming calls to the temporary number and relay them to the phone.
Types of Roaming:
Geographic Roaming
This type of roaming refers to the ability to transfer service from one area to another within the borders of a mobile network operator. Initially, operators often restricted services to small areas (such as a city). However, with the development of global GSM mobile network technology and decreasing costs, geographic roaming is rarely implemented, except in countries with vast geographic regions like the United States, Russia, and India, where there are many regional network operators.
In Vietnam, this is exemplified by SPs like Vinaphone and Mobifone, which previously divided regions into 1, 2, and 3. When calling locally, regionally, or across regions, customers were charged differently. Later, these SPs standardized charges across a single region for the entire territory.
The geographic roaming of a mobile network operator is also the form that EVN Telecom is implementing with its E-phone service. However, E-phone uses a fixed line but operates like a mobile network, leading to much debate, and the company had to temporarily suspend this type of roaming.
Inter-Provider Roaming
This type of roaming refers to the ability of a mobile operator to roam onto the signal of another operator within the borders of a country. For example, a Mobifone subscriber is allowed to switch to Vinaphone when the two service providers have an inter-roaming agreement. This often occurs when a new company enters the field and needs compatibility with the infrastructure of previous operators. They must request permission from these operators to allow roaming while they build their own network.
Currently, in Vietnam, the networks that support inter-roaming are Vinaphone and Mobifone based on GSM technology. However, the Ministry of Post and Telecommunications has not yet permitted these VNPT networks to roam with networks using CDMA technology, specifically S-Fone and more recently E-phone.
International Roaming
This service allows roaming onto a network of a foreign telecommunications service provider. This is a benefit for travelers and those frequently visiting different parts of the world. However, this type can encounter many issues due to different frequency bands in various countries. For example, most use the 900/1800 MHz bands, while the U.S. and some countries in the Americas use the 850/1900 MHz bands. Therefore, when purchasing a phone to travel to different countries, it is crucial to choose a model that supports 3 to 4 frequency bands.
In Vietnam, networks like Vinaphone, Mobifone, Viettel, and S-Fone have implemented international roaming services. Vinaphone is linked to 59 countries, Mobifone connects with 52 nations, Viettel is registered in 43 countries, and S-Fone also supports networks when you travel to South Korea, Taiwan, China, and Japan.
These networks do not charge a registration fee for international roaming services and only charge for service usage. The call, text, and incoming message pricing is detailed on the websites of Vinaphone, Mobifone, S-Fone. For Viettel services, customers can inquire at support centers.
To use roaming services, customers must be postpaid subscribers and visit centers to register. All charges will be billed at the end of the month. Some networks may require individual customers to deposit a certain amount beforehand, while corporate accounts or VIP subscribers may be exempt.
Roaming on the Internet
This form applies to accounts registered for Internet use. It allows global network access while traveling away from home at local or even cheaper long-distance call rates. For example, if you have registered for Internet service with a provider in Hanoi and travel to Hong Kong, instead of paying long-distance connection fees back to Hanoi, you only need to pay for the connection in Hong Kong plus a small roaming service fee.
Internet roaming occurs when Internet service providers (ISPs) have agreements to support customer access to the Internet at local rates. Specialized software allows ISPs to calculate user costs.
– Users must subscribe to an ISP that has international roaming agreements in their country.
– With this agreement, you will identify an ISP in the city you are visiting.
– In this destination, users can call the designated phone number of that ISP using their computer modem, entering login information for the network to identify your “home” ISP.
– The “foreign” ISP will contact the “home” ISP to verify the authenticity of the information.
– The “foreign” ISP will allow users to access the Internet and their mailboxes from the home server.
– Users will be charged at local call rates, and depending on the service pricing agreed upon by the two providers, the ISP may add an hourly or monthly fee.
However, if you only need to exchange emails, consider using popular free email services like Yahoo, Gmail, Hotmail, Rocketmail, etc. Hotmail supports POP3, allowing you to access up to four existing email accounts, as long as you remember the POP3 server name and your ID and password.
If you subscribe to a global service like AT&T’s WorldNet or IBM Global Network, you can access your account in various cities through a point-of-presence (POP) on the Internet without paying for long-distance calls.
Overall, as access costs around the world are generally cheaper than in Vietnam and free webmail services that support POP3, using Internet roaming seems outdated with traditional dial-up services like VNN1260. However, if you need to access the Internet in places with only telephone lines, you may find Internet roaming still convenient. VNN1260 subscribers can connect to the Internet in 150 countries that have signed agreements, including remote locations like Panama, Guam, and the Marshall Islands. For more details about this service, you can visit here.
