in these slides you will learn what is roaming and how it is work in simple way also with some signaling to show how the operators work together and how call & SMS routed , billing ,agreement , for any information plz contact me (rawand.ali@hotmail.com) Tel: +9647701105935

1. International Roaming
BY:Rawand Dlshad Jaf
IREG Engineer

2. Purpose of the presentation
• To Answer questions:
• ‘'What is Roaming?’’.
• Why we have ‘Roaming Agreements?
• How dose International Roaming
work?
• How do I get billed for making and
receiving calls?

3. What is Roaming?(1/1)
• “Roaming is defined as the ability for wireless customers to
automatically make and receive voice calls, send and receive
data, or access other services when travelling outside the
geographical coverage area of their own home network, by
means of using a visited network.”
simplified
• Service by a mobile network operator enabling
access to its network for subscribers to a foreign
mobile network for making and receiving calls

4. 1992
First international roaming
agreement between
Telecom Finland and
Vodafone in UK.

5. Roaming Agreement(1/1)
• 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
(International Roaming Expert Group) and
TADIG (Transferred Account Data Interchange
Group). While the IREG testing is to test the
proper functioning of the established
communication links that performed by IREG
Engineers , the TADIG testing is to check the
billability of the calls.

6. Roaming Services
• The service a roamer enjoys in a visited network
depends on three factors:
mobile station (MS) capabilities, the agreed list of
services in the roaming agreement, and the
subscription level.
Commercially available handsets generally support
the following networkcapabilities:
■ GSM
■ GSM + GPRS
■ GSM + GPRS + 3G

7. The technical aspects of international mobile
roaming
• The technical process of a roaming call is called
‘routing’.
• To understand the routing of international mobile call,
SMS and data roaming services, a basic
understanding of the signaling behind mobile phone
calls is needed. A mobile phone call requires two
different types of signals: the ‘control’ signal and the
‘voice’ signal. The control signal carries the network
data of the call. This signal allows for the mobile
phone to be identified, and records the destination,
length and geographical location of the call. The voice
signal carries the actual voice, SMS or data message.
•

8. How dose International Roaming work?(10/1)
The details of the roaming process differ among types
of cellular networks, but in general, the process
resembles the following:
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.

9. How dose International Roaming work? (10/2)
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, and here location
update process complete (LU).

10. HLR
MSC/VLR
IMSI
418 05
Is
roaming
allowed?
Copy of the HLR
Profile (data)
will
be stored in
Stock. VLR
Roamer Location Update
(10/3)
Signaling

11. Calling home: how does it work? (10/4)
• If you are calling back home, then the visited operator
analyses the dialed number , and decides how best to
route the call and the call will be routing to home
through a third operator called ‘carrier or international
transit’ .
• Remember, when you call home or any other country,
you have to type in the international access code and
the correct country code along with the telephone
number, omitting the leading zero.
• For example, to dial the IRAQ mobile number 0770
XXX XXXX from another country, you dial +964 770
XXX XXXX. If you are calling a landline, you may need
to include an area code.

12. Calling home: how does it work? (10/5)

13. Receiving calls: how does it work? (10/6)
• When someone calls you the call will be routed to the
operator whose network you are using in the visited
country (How?)

14. Receiving calls: how does it work? (10/7)
• If you remember when the Roamer try to make Location
Update the visit network MSC/ VLR (Mobile Switch
center/Visitor location register) will contacts the home
network HLR (Home location register) through GMSC
(gate way MSC) and requests service information
Likewise, the home network HLR updates its information
(address of the host VLR) to indicate that the mobile is
on the Visit network so that any Call or data can be
correctly routed to the roamer.
• Don't forget; all international signaling between two
operators transferring by the carrier.

15. Receiving calls: how does it work? (10/8)
HLR
GWMSC
MSISDN
0770…
MSC/VLR
Originating
Leg
Roaming Call
Forwarding Leg
Signaling
Voice

16. Receiving Call from another Roamer? (10/9)
When a Aisacell outbound Roamer -A- (let say in UK) calling
another Asiacell outbound Roamer roamer –B- in another country
(let say in USA) the call flow will be :
• A will dial B number with (+964 770 XXX XXXX) and the call will
be routed through host GMSC to Asiacell in IRAQ and after that
our GMSC will asking the location of B number from the home
HLR and it will know that B is roaming in USA so the call will
forward to USA (routed again) through asiacell and transferring
be the carrier.

17. Receiving Call from another Roamer? (10/10)
HLR
GWMSC
MSC/VLR
A
MSC/VLR
B
MSISDN
+964 770….
Roaming Call
Forwarding Leg
Signaling
Voice

18. How do I get billed for making and receiving calls?(2/1)
• When you use your phone while roaming (both making
and receiving calls), the visited operator will keep a
record of your calls. It will send these records, along
with the corresponding charges, to your home
operator.
Your home operator will aggregate these call charges,
and reflect them in your next bill. All charges will
appear in your home currency - your home operator
will convert the foreign operator charges for you
automatically.
It can take some time for the call charges to be sent to
your home operator by the visited operator.

19. How do I get billed for making and receiving calls?
(2/2)

20. •Thank you for you time
Please don’t hesitate to contact me if you need any
more information
www.rawand.ali@asiacell.com
Kirkuk region
IREG Eng