what is data roaming

What is data roaming? How to reduce data charges if in Roaming?


A mobile subscriber can browse the internet, make and receive VoIP calls while roaming. This is possible because a mobile network operator supports data or the Internet.  A mobile operator defines data usage in bytes (KB, MB, GB, etc.).

On recharge, A mobile subscriber (IMSI) is assigned a data bundle, say 1GB with one-month validity.  Using mobile internet incurred in units reduction from the data bundle. If browsing a page of 10KB in a web browser, reduces the available data limit to 10KB.

Rechange may be for local or for global data plans. For example, if a T-Mobile USA subscriber is in New York, the one MB data is .025 USD while if he is in the UK per MB data is .2 USD. Generally, international data roaming plans are much costlier.  So it’s important to know, how to save data while roaming.

In this tutorial, we will explain how mobile data works over a GSM network, and what are the possible ways to reduce data roaming charges?

Why Data Roaming (International especially) is costly?

The basic principle is that the more resources you will use more you will pay.  The same applies to data roaming as well.  To access the data a mobile subscriber attaches to the mobile network.  If the sim is local (T-Mobile subscriber in New York) in that country, network packets and data bytes use only a few numbers of hopes to attach and access data.

All network elements (e.g GGSN, SGSN, HLR, etc.) and the connecting network cables belong to the local sim card provider. So no incur in any additional cost to the third party if not in roaming.

How charges are calculated in roaming?  Once a T-Mobile USA user is roaming (E.g Under International UK network),  There are three networks, a local network in the USA, a roaming network in the UK, and a transit network(s) that connects local and roaming infrastructures.  Each network charges for each byte transferred between a mobile phone and the Internet.  So costs increase to many folds.


How to reduce the cost of data roaming?

The cost saving is around three factors, reduce data usage, use alternative options for data, and buy roaming-friendly plans. In this section, we will cover each option in detail.

Reduce Data Usage – The mobile phones come with an option to switch on/off data while roaming.  If you turn off that option and a mobile phone detects that the new network is not the home network it does not attach for data. The PLMN is the information that sim cards use to drive the network change.

  • Switch Off the data option for roaming.
    • Switch Off data usage on Roaming in Android ( Galaxy S8 reference example)-
      Open settings->Tap On Connections -> Mobile Networks.  Slid the button to the left to off data while roaming.
    • Switch Off data usage for Roaming in iPhone-
      Open settings-> Select Roaming Off in Cellular Data Options. For Details Check How to change settings for data.
  • MMS and Data usage – The normal text message uses only signaling, and mostly it’s (incoming) free. But MMS uses the internet,  so with data off, the MMS will also stop.
    Another way to stop MMS (Android), Go to Message App->Settings->More Settings->Multi Media Messages. Turn off the auto retrieve.
  • Set Data Usage Warnings if the device supports.
  • Set data usage Cap, if have device has this option.

Alternative Options –  The alternative option is a WiFi network. These days you will find this option at all the places, Railway Station, Airport, Shopping Malls, Offices, etc. So  Just connect to WiFi and use the data in roaming.

SIM with Roaming Plans- Before moving abroad you can check data pack plans with the existing operator. If that does not suit you, there are options for traveling sim cards.  Generally, you can find shops at airports for travel SIM.

A travel SIM card provider is a kind of virtual network operator with the support of multi IMSIs in the card. When you land up in a country it will activate the IMSI local of that country.  So now you are local.