When traveling abroad and wanting to stay connected using your familiar mobile phone number, or checking emails in Outlook Express from remote islands, you might consider the service referred to as “roaming.”
This term is commonly used in telecommunications to denote an extended service area where connectivity is available outside the original registration location. Roaming occurs when a subscriber of one service provider (SP) utilizes the infrastructure of another SP. The second SP does not have any service or financial agreements with the subscriber for sending and receiving information but works with the first SP to assist the user.
Currently, the subjects of roaming are mobile networks and the Internet.
Roaming in Mobile Networks
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| Source: Rentmobilephone |
In many cases, roaming occurs within the original registration area of the mobile phone when it transmits information via a tower of a different SP—usually when the signal of the original SP is too weak or when there are too many callers.
In each different mobile network, the roaming process will vary, but essentially it follows these steps:
– When the mobile device is powered on or hands over (handover) to a network, the “visited” network “sees” the device and determines whether it is on the registration list and attempts to identify its “home” network. If the two networks do not have a prior “interconnection” agreement, 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 permitted to roam.
– If successful, the visited network begins to maintain temporary subscription status for the device. At the same time, the home network updates information to identify the device being managed on its server, ensuring that any information sent to that device is transmitted accurately.
If there is an incoming call to the roaming phone, the public telephone network will direct it to the SP with which it is registered. This SP must then forward it to the visited network (which has agreed to the service). The visited network will provide a temporary internal phone number for the mobile. Once this number is identified, the home network will forward the incoming call to the temporary number and then to the mobile phone.
Types of Roaming:
Geographic Roaming
This type of roaming refers to the ability to transfer service from one region to another within the national 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 large geographic areas like the United States, Russia, and India, where there are many regional network operators.
In Vietnam, this is similar to how providers like Vinaphone and Mobifone previously divided regions into 1, 2, and 3. When calling within the region, inter-region, or across regions, customers would incur different charges. Subsequently, these providers began charging based on a single region across the entire territory.
The geographic roaming of a network operator is also the model that EVN Telecom is implementing with its E-phone service. However, since E-phone uses a fixed line but operates like a mobile network, this has caused much controversy, leading the company to temporarily suspend this type of roaming.
Inter-Provider Roaming
This type of roaming refers to the ability of a mobile network operator to roam onto the network of another operator within the borders of a country. For example, a Mobifone subscriber is allowed to switch to Vinaphone when these two service providers have an inter-roaming agreement. This typically occurs when a new company enters the market and needs compatibility with the infrastructure of existing 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 allowed these VNPT networks to roam with networks that use CDMA technology, specifically S-Fone and recently E-phone.
International Roaming
This service enables roaming onto a network of a foreign telecommunications service provider. This is beneficial for travelers and those frequently visiting various places worldwide. However, this type may encounter many issues due to different frequency bands used by countries. For example, most use the 900/1800 MHz band, while the United States and some countries in the Americas use the 850/1900 MHz band. Therefore, when purchasing a phone for use in multiple countries, you need to choose one that supports 3 to 4 frequency bands.
In Vietnam, networks such as Vinaphone, Mobifone, Viettel, and S-Fone have implemented international roaming services. Vinaphone has connected to 59 countries, Mobifone to 52 countries, Viettel to 43 countries, and S-Fone also supports networks when you visit South Korea, Taiwan, China, and Japan.
These networks do not charge a registration fee for international roaming services but only charge for service usage. The charging methods for outgoing calls, text messages sent or received, and incoming calls and messages are detailed on the websites of Vinaphone, Mobifone, and S-Fone. For Viettel’s services, customers can inquire at the support center.
To use roaming services, customers must have a postpaid subscription and visit centers to register. All costs will be charged to the monthly bill. Some networks may require individual customers to deposit a certain amount beforehand, while entities such as businesses, VIP subscribers, etc., may be exempt.
Roaming on the Internet
This form applies to accounts registered for Internet use. It allows access to the global network while away from home at local or lower rates than long-distance charges. For instance, if you have an Internet account with a service provider in Hanoi and travel to Hong Kong, instead of paying long-distance connection fees back to Hanoi, you only need to pay the connection fees in Hong Kong plus a small roaming service fee.
Internet roaming is facilitated 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 an international roaming agreement in their country.
– With this agreement, you will identify an ISP in the city you are visiting.
– At the destination, users can call the designated ISP phone number through their computer’s modem, enter 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 check emails from their home mail server.
– Users will be charged at local phone rates, and depending on the service pricing agreed upon by both providers, the ISP may add additional hourly or monthly charges.
However, if you only need to exchange emails, you might consider popular free email services like Yahoo, Gmail, Hotmail, and Rocketmail. Hotmail supports POP3, allowing access to up to 4 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 incurring long-distance call charges.
Overall, since internet access fees worldwide are generally cheaper than in Vietnam and free webmail services can support POP3, using Internet roaming may seem outdated with dial-up services like VNN1260. However, in cases where you need internet access in places with only telephone lines, you might still find internet roaming 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.
