03802 Appendix a Mnp

Mobile Number Portability

Appendix A

This chapter is designed to provide the student with an overviewof the Mobile Number Portability functionality.

OBJECTIVES:Upon completion of this chapter the student will be able to:

• Explain how the Mobile Number Portability is performed.

• List the different routing scenarios.

• Explain the NP structure.

WCDMA Systems HLR Operation, CN2.0 / GSM HLR Operation, R9.1

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Appendix A Mobile Number Portability

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Appendix A

Mobile Number Portability

Table of Contents

Topic Page

NUMBER PORTABILITY.......................................................................1

GENERAL.......................................................................................................................1

CONCEPT ......................................................................................................................1

TECHNICAL SOLUTION.......................................................................4

DIRECT ROUTING.........................................................................................................4

INDIRECT ROUTING .....................................................................................................6

INDIRECT ROUTING WITH REFERENCE TO THE SUBSCRIPTIONNETWORK .....................................................................................................................7

SEND ROUTING INFORMATION..........................................................9

OTHER TRAFFIC CASES..............................................................................................9

SCCP OR TCAP ANALYSIS ...............................................................10

NP STRUCTURE .................................................................................11

SRF...............................................................................................................................11

MAPfu ...........................................................................................................................12

ACRONYMS AND ABBREVIATIONS.................................................13


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NUMBER PORTABILITY

GENERAL

Number portability (NP) is a function that allows the subscriberto retain their subscriber number (MSISDN) when they changetheir service provider (Service Provider Portability, for examplechange from operator A to operator B) within one country.Number Portability is a network feature, not a subscriberservice, which is agreed between different network operators inthe same country.

CONCEPT

The performance of number portability is based on a modifiedFlexible Numbering Register (FNR). FNR was introduced inGSM with Ericsson’s release R6.1 and is still available underthe name “Flexible allocation of MSISDN”.

The advantages of this solution are:

• It can interwork with non-Ericsson nodes.

• The FNR has the same platform as other CME20 nodes(HLR, MSC/VLR).

• Flexible Numbering functionality and NP database areimplemented in the same node.

There are some differences from what we got in previousMobile Number Portability releases:

General improvements:

• Improved measurement capability through new counters

• Fraud prevention – a new mechanism to prevent portedsubscribers from sending SMS messages via the operator’sSMS service center

Database improvements:

• The capacity has been improved from 4 million to 16million subscriber numbers, and from 512 to 16,384 groupnumbers.

• The storage capacity for Home PLMN Network DestinationCodes (NDC) has been increased from 32 NDCs to 64NDCs.


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• The maximum length of network prefixes has been increasedfrom 4 digits to up to 10 digits.

Traffic improvements:

• Extended support for Translation Type (TT) handling, as itis possible to define up to eight incoming to outgoing TTrelations and outgoing SSN (TTIN->TTOUT + SSNOUT)

• Extended support of generic IMSIs, with a capability ofdefining up to sixteen network routing number prefixes togeneric IMSI relations

• Database mismatch detection

• Support of number portability information in SRI-ACK(Send Routing Information, Acknowledgment)

For implementing NP the following principles are used:

• Default Address: The address that is used to route messagesfor which no information is stored in the MNP database.

• Ported number: A number that was first served by networkA, that now is served by network B while still is being usedby the same subscriber.

• Originating network: The network where the calling party islocated

NOTE: For incoming calls to the routing domain, theoriginating network is effectively the first network receiving thecall within the routing domain. For example, for incominginternational calls, the originating network is effectively thenetwork containing the inter-national switching center (ISC). Ina PLMN, the equivalent function is contained in the GatewayMobile-services Switching Center (GMSC).

• Donor network: The network from which a number isported.

• Recipient network: The network that receives the portednumber and serves it.

• Prefix: Digits, used for routing purposes, which identify anetwork operator. The prefix is used for B numbers as wellas for C7 addresses.

• MNP Database: A database from where the condition of thesubscriber (home, imported, exported, or in other network)and the prefix of the network where the call can be routed isstored.

• Home subscriber: That subscriber whose MSISDN belongsto a number series assigned to the mobile operator and thathas not been ported.


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• Exported subscriber: That subscriber whose MSISDNbelongs to a number series assigned to the mobile operatorand that has been ported to another network operator.

• Imported subscriber: That subscriber whose MSISDNbelongs to a number series initially assigned to anothermobile operator and that has been ported to our network.

• Subscriber in Other Network: That subscriber whoseMSISDN belongs to a number series assigned to anotheroperator, and that has not been ported or has been ported to athird operator.

Some general network prerequisites are needed for the NPsolution:

• Standardized solution uses Concatenated Addressing (that is,a prefix) independently of the approach.

• The prefix is agreed in length and meaning among thePLMN operators in the country, together with the NationalTelecom Regulatory body (CMT in Spain, OFTEL in UK,etc). This prefix will be included in the routing data of thesignaling messages when needed.

• Transit networks have to support routing of calls based onthis prefix.

• Operators exchange information about ported subscribers,either directly among them, or by means also of acentralized national database for ported numbers.

• The largest portability domain is a country.

• The ported subscriber is using an IMSI (SIM/USIM card) ofthe recipient network.

Ericsson’s solution fulfills the requirements on NP, for the threebasic NP approaches (behavior can be chosen depending oncustomer/national telecom reasons, full compatibility amongthese possibilities within the portability domain, that is,country).


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TECHNICAL SOLUTION

Mobile Number Portability implementation is based on amodified FNR node. This has the capability to detect portednumbers, route the SCCP messages and to force the GMSC toforward the call to the network where the subscriber has his / hersubscription.

When a SCCP message is received in the FNR, the CdPA isextracted. If found to be an exported number, the message isrelayed to the recipient FNR containing CC +NPREFIX +NDC+SN or answered to the originating GMSC.

DIRECT ROUTING

The query to the FNR database is done in the network thatoriginates the call or non-call related messages. The message isdirectly addressed from the originating network to the networkwhere the called subscriber has presently his/her subscription,optimizing in this way the routing of messages.

A very common special case is when the originating network isequal the donor network.

1. In the originating network the Send Routing Information(SRI) message is sent from GMSC to FNR: In the NPdatabase the MSISDN included in the called address ischecked to see whether this E.164 number belongs to a:

• Home or imported subscriber or

• To an exported subscriber and/or

• To a subscriber in another network

If MSISDN number corresponds to a home or importedsubscriber: The SRI is transferred to the destination HLR.


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Figure A - 1 Number Portability Direct Routing Method callsetup.

2. If the MSISDN number corresponds to an exportedsubscriber or to a subscriber belonging to another network:The SRI is answered. The SRIack is sent back to GMSCwith a prefixed MSISDN as a roaming number. The prefix isused to point out to the destination network

The GMSC proceeds with the call, routing towards thedestination network.

3. In the destination network the prefix is removed and the callproceeds normal. GMSC sends the SRI to the FNR. FNRtransfers the SRI to the corresponding HLR. HLR requests aroaming number in VLR. HLR answers the SRI with theRoaming Number received from the MSC/VLR.

In this scenario, Imported and Exported subscribers, andsubscribers ported between other network operators, aredefined in the FNR as individual entries. Home and Other(Home in another network) subscribers have to be stored inthe FNR as series.


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INDIRECT ROUTING

Call or non-call related messages are routed to the network thatowns the MSISDN series the subscriber belongs to (the donornetwork). The interrogation to the FNR database is done in thisnetwork and in the case the subscriber has been exported, themessage is relayed to the network where the subscriber haspresently his/her subscription. The call is first routed to a GMSCin the donor network according the B-number (MSISDN).

1. A Send Routing Information (SRI) message is sent fromGMSC to FNR: In the NP database, the MSISDN included inthe called address is checked to see whether this E.164 numberbelongs to a:

• Home subscriber

Or

• To an exported subscriber

A message to a subscriber in another network should neveroccur because the call was already routed to the donor networkor number range owner network.

Originating Network

Donor Network

GMSCFNR1

Recipient Network

MSC VLR

HLRGMSC

2

FNR

3

GMSC

Figure A - 2 Number Portability Indirect Routing Method callsetup.

If MSISDN number corresponds to a home subscriber: The SRIis transferred to the destination HLR.


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If the MSISDN number corresponds to an exported subscriberthe SRIack message is sent back to the GMSC. The calledaddress is changed including a prefixed MSISDN as RoamingNumber to reach the recipient network.

2. The GMSC sends the IAM message with the prefixedMSISDN to the recipient network.

3. The GMSC in the recipient network receives the IAMmessage from the donor GMSC and removes the prefix.

Call proceeding is normal. GMSC sends the SRI to the FNR.This message is called Second Query. At this point thesubscriber status must be Imported, if not the DatabaseMismatch Detection Error function is activated.

FNR transfers the SRI to the corresponding HLR. HLR answersthe SRI with the Roaming Number received from the MSC/VLR

In this scenario, Imported and Exported subscribers, have to bedefined in the FNR with individual entries. Series of Homesubscribers have to be stored in the FNR.

INDIRECT ROUTING WITH REFERENCE TO THE SUBSCRIPTIONNETWORK

Call or non-call related messages are routed to the network thatowns the MSISDN series the subscriber belongs to (the donornetwork or number range owner network). The interrogation tothe FNR database is done in this network and in the case thesubscriber has been exported the message is relayed to thenetwork where the subscriber has presently his/her subscription.

1. The call is first routed to a GMSC in the number rangeowner network according the B-number (MSISDN).

2. A Send Routing Information (SRI) message is sent fromGMSC to FNR: In the NP database, the MSISDN checked tosee whether this E.164 number belongs to a:

• Home subscriber

Or

• To an exported subscriber

A message to a subscriber in another network should neveroccur because the call was already routed to the donor networkor number range owner network. If MSISDN number


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corresponds to a home subscriber: The SRI is transferred to thedestination HLR.

3. If the MSISDN number corresponds to an exported subscriberor to a subscriber belonging to another network: The SRI istransferred to the FNR of the recipient network. The calledaddress is changed including the prefix of the recipient network.

Figure A - 3 Number Portability Indirect Routing with Referenceto the Subscription Network Method call setup.

4. The FNR of the recipient network answers the SRI back tothe number range owner network. GMSC. FNR includes aprefixed MSISDN as Roaming Number.

5. GMSC in the recipient network receives the IAM messagefrom the donor GMSC and removes the prefix.

6. Call proceeding is normal. GMSC send the SRI to the FNR.This message is called Second Query. At this point thesubscriber status must be Imported, if not the DatabaseMismatch Detection Error function is activated.

FNR transfers the SRI to the corresponding HLR. HLR answersthe SRI with the Roaming Number received from theMSC/VLR.

In this scenario, Imported and Exported subscribers, have to bedefined in the FNR with individual entries. Series of subscribershave to be stored in the FNR.


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SEND ROUTING INFORMATION

An AXE parameter (SRIMNGNTFOREXP) control thedifferent behavior of the FNR when treating SRI messages forexported subscribers in the different scenarios below.

• For Direct Routing the SRI message is answered back with aSRI-acknowledgement message, including in the parameterfield MSRN a combination of the MSISDN and theassociated prefix.

• For Indirect Routing the SRI message is relayed to thecorresponding network replacing the called party address bya combination of the MSISDN an the associated prefix(U.K.).

In some cases the translation type (TT) in SCCP address ischanged to TT1 to prevent circular routing. TT1 is set byapplication parameters. The routing tables in the C7 networkhave to be adapted.

OTHER TRAFFIC CASES

Other traffic cases are treated similarly to the call setup withSRI messages. An example is delivery of SMS.

Please note that Location Updating is not a traffic case for NPbecause the subscriber’s identification is based on IMSI and thisbelongs to the numbering plan from the recipient network. NPgives solution for messages routed withMSISDN as calls and SMS.

Note. - When talking about call related messages, the standardSend Routing Information operation as well as the Ericssonproprietary one, Routing Information Request, are concernedwhile non call related messages SRI-SMS, CCBS, IN queries inHLR are concerned.


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SCCP OR TCAP ANALYSIS

Messages can be analyzed on two different levels:

• Analysis on SCCP level is performed in order to extract theMSISDN from the SCCP address. The type of subscriber(home, exported, imported or other) is determined analyzingthis MSISDN.

• Analysis on TCAP level is required when the operation codeof the message as well as the type of subscriber is requiredto decide how to proceed with the message.

FNR attaches to SCCP and to TCAP with two differentSubsystem Numbers (SSN) that are defined by applicationparameters.

When the message is relayed from SCCP User to TCAP User,the TT of the called party address of the message is modified.

The value of this TT is established by application parameter.

MTP

SCCP

TCAP

SSN1 SSN2

NP Data Base

MAP SRI handlerSRF

Figure A – 4 Number Portability Internal Structure.


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NP STRUCTURE

NPF will consist of two subsystems, each with an own SCCPnumber. The first subsystem will be a signal relay function(SRF); this will inherit the FNF subsystem number if this isavailable in the network or alternatively, set by exchangeparameter. The second subsystem is the MAP analysis function(MAPfu or TCAP-user).

SRF

SRF is a user of SCCP; however, it forms a logical extension toSCCP Global Title Translation. SRF receives all MAP messagesrouted on MSISDN and obtains subscriber portability statusfrom the database.

If the subscriber is exported, a check is made on the method ofNPF operation. If Exported-SRI-relayed mode is used, themessage is relayed towards the recipient network.

Alternatively, if Exported SRI-acknowledged mode is in use themessage is passed to MAPfu for subsequent analysis and actionbecause at this stage the specific type of MAP message is notknown.

If the portability status indicates a home subscriber the messageis routed towards the appropriate subscribers HLR. This routingis performed on the SCCP layer either via MSISDN or, if FNFfunctionality is available, via a derived MGT.

If a subscriber portability status indicates imported and the MAPmessage origin is derived to be from the own network, themessage is routed to the appropriate HLR as in the case for ahome subscriber as indicated above. Alternatively, if themessage originated from an external network the message ispassed to the MAPfu in order to derive the type of MAPmessage. This only happens for incoming TT=0. When thenetwork does not support optimal routing TT=0 can be eithercall related or non-call related and the operation code must beanalyzed.

For calls towards Other subscribers, the message is passed toMAPfu for subsequent analysis and action as the specific typeof MAP message is not known.


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MAPfu

This subsystem is a TCAP user and is used to establish the typeof MAP message. For the mobile number portability functionthe only MAP analysis required is merely in order to establishwhether a received message is a SRI distinguishing between callrelated and non-call related.

SRI and RIR (Ericsson variant protocol) will be answered back

If a SRI is received for an exported subscriber a SRI-ACK isgenerated containing routing digits that allow the inquiringGMSC to forward the call to the recipient network.

If a SRI is received from an external network for an importedsubscriber a SRI-ACK is generated containing a definedintermediate routing number. This is returned using the CgPA ofthe GMSC initiating the SRI enquiry as the destination CdPAwithin the SCCP layer of the returned SRI-ACK.

If the received message is not a SRI and the subscriberportability status indicates an imported subscriber, the messageis relayed to the appropriate HLR. Alternatively, if it is anexported subscriber the message is relayed to the recipientnetwork.


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ACRONYMS AND ABBREVIATIONS

AXE 10 Ericsson’s telecommunication platform

AUC Authentication Centre

CAS Customer Administration System

CCBS Completion of Calls to Busy Subscriber (service)

CCS Common Channel signaling Subsystem

ETSI European Telecommunications Standard Institute

FNR Flexible Numbering Register

FNS Flexible Numbering Register Subsystem

GMSC Gateway Mobile service Switching Centre

GSM Global System for Mobile communication

GT Global Title

HLR Home Location Register

IMSI International Mobile Subscriber Identity

MAP Mobile Application Part

MAPfu MAP analysis function of MNP

MGT Mobile Global Title

MSC Mobile services Switching Centre

MSISDN Mobile Station ISDN Number

MSISDNS MSISDN Series

MTP Message Transfer Part

NDC National Destination Code

NP Number Portability

NPREFIX Network PREFIX

PLMN Public Land Mobile Network

SCP Service Control Point


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SCCP Signaling Connection Control Part

SMS Short Message Service

SOG Service Order Gateway

SRF Signaling Relay Function

SSF Service Switching Function

STP Signaling Transfer Point

VLR Visitor Location Register


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Documents

03802 Appendix a Mnp