Welcome to ZenUnwired; a blog dedicated to tracking developments in technology and strategy, and to deciphering the impact of these developments on wired and wireless ISP's, device manufacturers, OS and application developers, and most importantly - you.

Monday, May 7, 2012

Roaming - A High Level Overview

How do you define "Roaming"?
The term "Roaming" originates from the GSM (Global System for Mobile Communications), and is defined as the ability for a cellular customer to automatically make and receive voice calls, send and receive data, or access other services when travelling outside the geographical coverage area of the home network, by means of using a visited network. Establishing roaming between network operators is based on a Roaming Agreement.


If I am a customer with a mobile phone, what does Roaming mean to me?
If you have a mobile phone you can take it with you when traveling to another region or country and you can place or receive calls without changing the SIM card.

What are the different types of Roaming?
  1. If the visited network is in the same country as the home network, this is known as National Roaming (e.g., Sprint and Verizon)
  2. If the visited network is outside the home country, this is known as International Roaming (e.g., Vodafone UK and AT&T USA)
  3. If the visited network is of a different technology, this is known as Inter-Standard Roaming (e.g., CDMA and GSM)
A distinction is also made between Inbound and Outbound roaming:
  • Inbound - when the operator acts as the "Visited Network"
  • Outbound - when the operator act as the "Home Network"
How does International Roaming work?
Cell phone carriers from most countries have roaming agreements that basically allow you to use their wireless network when traveling abroad. Generally you do not need to do anything - the foreign carrier will take over so to speak and you will see another carrier name on your cell phone's screen once you are in another country. What you do have to do is call your wireless carrier before leaving your country and activate your roaming service. This is not a default feature (it implies extra costs).

Do carriers implement all Roaming partnerships the same way?
No. There are different models that could apply when you are ready to establish a roaming partnership with another provider. These models include
  • Bilateral Model: Roaming implemented directly between two operators without using an intermediary
  • Roaming Hub Model: Hub providers offer a mobile operator instant global roaming through a single contract.
  • Sponsor Model:  Allows a mobile operator to establish roaming using the International Mobile Subscriber Identity (IMSI) of a sponsored Operator - a quickly and cost efficient way to expand coverage worldwide.
Each model has its own advantages and disadvantages, and you have to select the best one that fits your business strategy.

If I have International Roaming enabled, will my mobile phone work everywhere?
It depends. Sometimes the cellular network used in the country you're traveling to is not the same as the one used by your carrier. In this case you must have a cell phone supporting both networks. Call your wireless carrier for specific info.

How do I make calls while in another country?
Note that you cannot dial the numbers in your phone agenda as they are - you must add/drop some digits depending on the location you are at, and the country you are dialing to.

How do people from my home country call me?
People from home can call you AS IF YOU WERE HOME. In other words they do not need to add any digits to the number they usually dial when calling you.

Who pays international charges for calls I receive? Does this change if I an unlimited plan?
You do. Unlimited plans generally are applicable only when you are within your home country. You will be charged for each call – usually by the minute – for any calls made or received while you are traveling outside your home country