1) Optimal routing (OR) is a value-added service that allows calls between roaming subscribers within the same country to be directly routed between serving networks, avoiding international call legs and saving costs. 2) OR requires maintaining a real-time database of inbound roamers including location, serving network, and other data extracted from signaling messages. 3) Typical OR implementations route calls to a special platform housing the roamer database, which analyzes the destination and routes internally or obtains a local number from the destination network.

1. Roaming Value-Added Services
BY:Rawand Dlshad Jaf
IREG Engineer

2. Roaming in GSM Network
International roaming offers a great opportunity for wireless
service providers to improve revenues and generate more profits.
They are continuously exploring new ways to attract more roamers
to their networks.
As you know the roamer set the hand to network register
automatically according to the Signal Strength, Reselection may
be happens when the roamer moves and the Roamer don't have
the loyally to any network out side home country.
But the question is how we can attract the roamer to manually
network selection
The Ans .”by Cost of usage, Service , Discount,…ECT” And VAS

3. Optimal Routing
What happens when Roamer calling another Roamer in the
same Country?
MSC/VLR
HLR
MSC/VLR
1-Dial
B
2-Call route to home network
MSC/VLR
3 6
3-Sending
routin Info
6-Provide by
MSRN.
4-asking MSRN
5-MSRN
8
Call Route to B
B
A
Country X
Country B

4. Optimal Routing
This is surly not an efficient routing because is require tow
international call legs , for that we need optimal routing (OR) as
value add service to attract & retain Roamers in Visit net.
OP allows a call to routed directly from originating MSC to MSC
currently serving roamer for that the international call will be
avoided saving cost and OP can be applied to following scenarios:
1- Inbound Roamer to Roamer call in same Country and network.
2- Inbound Roamer to Roamer call in same Country but other
network.
3-A local Subscriber calling Inbound roamer in same network.

5. Implementation
• Usually access code is used fallowed by the regular B party
international number.
• All the OR call are routed to a special Platform which enable the OR,
there could be several different ways to implement OR in the
network.
• The three important requirement for any OR implementation are:
1. Acquire, maintain, and manage the data for all inbound roamers currently in
the network in real time.
2. Analysis of the B party number to check if it is an inbound roamer currently
in a network implementing OR or in any other PLMN within the same country,
where the call could be routed locally.
3. If OR is possible, then acquire MSRN from the serving MSC to route the call
locally.

6. The key roaming procedures, such as location update, insert subscriber
data, authentication, and cancel location messages provide all the
critical information to build the database for OR purposes (by extract
the signaling messages from the CCS7 links carrying MAP traffic to
partner networks).
For example, by decod-ing a UL/ISD procedure, the following
parameters can be extracted.
■ Subscriber’s IMSI
■ MSISDN
■ HLR address
■ Serving MSC/VLR address
■ Timestamp for first and subsequent UL
How can I get a database for OR?

7. Typical implementation. (Roamers under Same
Operator)
Mobile/inbound RoamerMobile/inbound Roamer
Fixed lineFixed line
OR
pattform
OR
pattform
1-IAM,B party
number.
1-IAM,B party
number.
Roamer data
base
Roamer data
base
2-Get IMSI
<VLR/MSC>
2-Get IMSI
<VLR/MSC>
3-IMSI, VLR/MSC3-IMSI, VLR/MSC
MSCMSC
VLRVLR
4-AskthMSRN
4-AskthMSRN
5-ResponseMSRN
5-ResponseMSRN
5-IAM
(M
SRN
)
5-IAM
(M
SRN
)
B inbound RoamerB inbound Roamer
<OR access code><B party international number><OR access code><B party international number>

8. Typical implementation. (Roamers in same
country but under different Operators)
Mobile/inbound RoamerMobile/inbound Roamer
OR
pattform
OR
pattform
1-IAM,B party
number.
1-IAM,B party
number.
Roamer data
base
Roamer data
base
2-Get IMSI
<VLR/MSC>
2-Get IMSI
<VLR/MSC>
3-HLR3-HLR
MSCMSC
VLRVLR
8-IAM
(M
SRN)
8-IAM
(M
SRN
)
B inbound RoamerB inbound Roamer
Fixed lineFixed line
HLRHLR
4-SRI (MSISDN)
4-SRI (MSISDN)
5- Ask MSRN5- Ask MSRN
6- MSRN6- MSRN
7- MSRN
7- MSRN
Home networkHome network