Mobile numberportability

© Tech Mahindra Limited 2011 © Tech Mahindra Limited 2010

Mobile Number Portability: Riding the wave Author Krishnan V, Bhaswar Sanyal

Abstract: After a prolonged deliberation, the Mobile Number Portability has been tabled on the Indian Telecom space and it is set to liberalize the final frontiers of competition in the Telephony space. Subscribers have been unwillingly tied on to service providers irrespective of deteriorating service standards, thanks to locked in number series per provider. Now MNP is going to change that all for good. This paper explains the underlying MNP technology and its impact to the telephony ecosystem. The paper also deals with how Tech Mahindra, a R&D and engineering services powerhouse, can shape this evolution.

1 © Tech Mahindra Limited 2011

Table of Contents

Technical Abstract ........................................................................................ 2 Acronyms .................................................................................................... 3 Number Portability technical aspect ............................................................... 4 Mobile Number Portability regulatory guidelines in India ................................. 9 NPDB interfaces ......................................................................................... 10

STP based Triggerless Translation ............................................................. 10 MNP Business Opportunities ....................................................................... 15 Tech Mahindra’s role in MNP ...................................................................... 17 References ................................................................................................ 18


Technical Abstract Lock in of mobile number series with Telecom Service Providers has always been an impediment to ushering in healthy competition between the mobile carriers. While India has seen a rapid growth in the penetration of Telephony services, the same exponential growth is seen lacking when it comes to quality of service offered or openness of transaction with the large players. Though the initial enrolment of subscribers to specific carriers has an atmosphere of enthusiasm and a promise of quality around it, subsequently there is marked degradation in quality of service. Customers are discouraged to switch service providers as that would involve changing numbers and possibility of lost calls for the end user.

Mobile Number Portability (MNP) is a technology that enables subscribers to switch their service providers while retaining their mobile numbers. Deceptively trivial in terms of nomenclature, the underlying technology that realizes this is quite complex and neatly integrated into the telephony infrastructure. We attempt to demystify some of those.

The other significant aspect is the fact that MNP has reached the Indian shores. The TSP’s have been mandated to adopt MNP soon and it is expected to create lot of action and opportunity. The country as of June, 2010 had 635.5 million mobile subscribers, as quoted by TRAI. Going by the Telecom Regulatory Authority of India (TRAI) guidelines, mobile users will be allowed to use the same mobile number even if providers use different mobile technologies like CDMA (code division multiple access) or GSM (Global System for Mobile Communications). We are thus looking into an opportunity of substantial dimension and Tech Mahindra’s leadership in the Telecom services space should be well leveraged to ride this wave.


Acronyms ACQ ‐ All Call Query CAP ‐ CAMEL application Part CDMA ‐ Code Division Multiple Access CdPN ‐ Called Party Number CS1 ‐ Capability set1 DOT ‐ Department of TelecomDPC ‐ Destination Point code GSM ‐ Global system for mobile Communication HLR ‐ Home Location Registrar IETF ‐ Internet Engineering Task Force ISUP ‐ ISDN User Part LRN ‐ Location Routing Number MAP ‐ Mobile Application Part MSC ‐ Mobile Switching centre MSISDN‐ Mobile Station Integrated Services Digital Network B MSISDN‐ "called party Subscriber” MSISDN NP ‐ Number Portability NPDB ‐ Number Portability Database OPC ‐ Originating Point code QoR ‐ Query on Release SCP ‐ Service Control Point Sigtran‐ Signalling Transport SMSC ‐ Short Message Service Center SPNP ‐ Service Provider number Portability SCF ‐ Service Control Function STP ‐ Signal Transfer point TRAI ‐ Telecom Regulatory authority of India


Number Portability technical aspect Number Portability has to ensure that call routing for all mobile sessions Voice, SMS, MMS should be enabled with routing to the ported network for the same called subscriber number. IETF defines three types of number portability (NP): Service provider number portability (SPNP), location portability and service portability.

The current paper focuses on the SPNP, which is the agenda set by TRAI to the service provider bodies in India. SPNP allows subscribers to switch service providers while retaining the same phone number. The technology challenges towards implementation come through complexities in number administration, network signalling functions, call routing, billing and service management.

A translation element is necessitated in the network as the mobile number addressing scheme becomes a virtual address. Central to the address translation scheme is the NP translation database hereafter to be termed as NPDB (Number Portability Database).The network classification is done as follows:

Donor Network: The network that first assigns a telephone number to a

subscriber from one of its administered ranges

New Serving Network: The network of the current service provider serving the ported number.

Old Serving Network: The network prior to porting in of the number to the current network. It is not necessarily the Donor network as multiple provider switches is feasible.


The implementation of the routing is through four different schemes:

A. All Call query (ACQ)

The Originating Network receives a call from the caller and sends a query to a centrally administered Number Portability Database (NPDB), a copy of which is usually residing on a network element within its network (like SCP).

The NPDB returns the routing number associated with the dialed directory number. A LRN prefix is usually added to the B‐MSISDN for the ported out number.

The Originating Network uses the routing number to route the call to the new serving network. Based on the LRN prefix (Location Routing Number) the originating network will route the call to the recipient network.

As donor network doesn’t get involved in the entire call flow ACQ scheme is called direct routing.


B. Query on Release (QoR)

The Originating Network receives a call from the caller and routes the call to the donor network.

The donor network releases the call and indicates that the dialed directory number has been ported out of that switch.

The Originating Network sends a query to its copy of the centrally administered NPDB.

The NPDB returns the routing number associated with the dialed directory number.

The Originating Network uses the routing number to route the call to the new serving network.

The QOR mechanism can hold out to be a smart implementation when the MNP porting figures are low. There are no unnecessary SCP queries for B party subscribers that are not ported yet, which is likely to save ample processing capacity on the network as well as associated call setup delay.

However as the porting figures rise (which is close to 25% in most mature MNP markets), the cost of call setup and subsequent release in case of ported out numbers is likely to take an adverse hit on the network utilisation as well as setup cost.

Thus for a future proof implementation ACQ is the recommended scheme.


C. Call Dropback

The Originating Network receives a call from the caller and routes the call to

the donor network.

The donor network detects that the dialed directory number has been ported out of the donor switch and checks with an internal network‐specific NPDB.

The internal NPDB returns the routing number associated with the dialed directory number.

The donor network releases the call by providing the routing number.

The Originating Network uses the routing number to route the call to the new serving network.

D. Onward routing (OR)

The Originating Network receives a call from the caller and routes the call to the donor network.

The donor network detects that the dialed directory number has been ported out of the donor switch and checks with an internal network‐specific NPDB.

The internal NPDB returns the routing number associated with the dialed directory number.

The donor network uses the routing number to route the call to the new serving network.


Again from the point of evaluating the efficiency of OR implementation, the scheme is heavily resource intensive with non‐optimal utilisation. In circumstances of ported out numbers, there are redundant pairs of voice circuits that are kept engaged for the same call between the Originating Switch, Donor Switch and Recipient switch. The switching matrix as well as the CPU of the donor switch will be kept loaded for the entire duration of the call, for which it is no longer responsible.

Except the ACQ scheme all other schemes initiate a call to the Donor network, only to be released or rerouted back to the serving network. Thus ACQ is the most efficient scheme with the most optimal use of the switching and associated network facilities. The ACQ scheme queries the NPDB to retrieve the routing information. The centralized NPDB contains the ported number information from multiple networks.

Number Portability implementation through NPDB is also called an ‘Off‐switch’ solution, which essentially implies that databases with routing information are separated from the switches. The ‘Off‐Switch’ solution are based out of the STP/SCP capabilities in a network, wherein the IN/ SCP (Service Control Point) hosting the central database. The centralized database is usually a time‐sync copy of the national number portability database maintained by the regulatory body where every ported‐out and ported‐in number needs to be registered.


Mobile Number Portability regulatory guidelines in India

Out of several types of number portability DoT has recommended Service Provider Number Portability (SPNP) for all mobile service operators.

MNP will be restricted only for intra circle operators.

MNP will be allowed between CDMA and GSM operators.

ACQ (All Call Query) direct routing method is to be adopted to implement MNP.

The Department of Telecoms (DoT) in India has awarded licenses for two mobile number portability clearinghouse vendors to operate clearinghouses in two zones within the country.

Syniverse Technologies India (North‐West zone ) and MNP Interconnection, a joint venture by US‐based Telcordia Technologies(South‐East zone), would act as the clearing houses in the respective zones to manage porting activities.

These CCH will download the MNP database in operators NPDB on daily basis and also manage the communication channels from the SP’s to the NPDB.

Major Mobile Operators in India: Aircel , Bharat Sanchar Nigam Ltd (BSNL) , Bharti Cellular Ltd (Airtel) , BPL Mobile , Idea Cellular , Mahanagar Telephone Nigam Limited (MTNL) , Reliance Telecom Ltd , Spice Telecom Ltd , Tata Teleservices , Virgin Mobile , Vodafone Essar .


NPDB interfaces

STP based Triggerless Translation

As we attempt a deep dive into the subject we did like to gather our attention more towards the MNP (specifically for the GSM Mobile) implementations and the underlined technologies that piece it up together.

MNP translations are performed by the signalling network layer (e.g., Signalling Transfer Points (STPs) or signalling gateways). ISUP IAM messages are examined to determine if the CdPN field has already been translated, and if not, an NPDB query is performed. The modified IAM message is forwarded by the signalling node on to the designated DPC in a transparent manner to continue call setup. The NPDB can be integrated with the signalling node or, accessed via an Application Programming Interface (API) locally, or by a query to a remote NPDB using a proprietary protocol. Clarification of key MNP nodes is as follows;

MCH (Central Clearing House): MCH will be talking to NPGW of all operators to download the porting data on daily basis over IP through SOAP/XML protocol.


NPGW (NP Gateway): Connects to the BOSS layer to affect a southbound provisioning of ported in subscribers onto HLR and as well talk to STP NEM (Network Element Manager) to download porting data.

STP NEM (Network Element Manager): Part of service providers core network NEM would be centralized node which will be dumping data in to STP NPDB.

STP NPDB (Number Portability Database): Part of SP’s core network and connected to other core elements like MSC/MSS, IN, HLR, SMSC, MMSC, and SGSN. STP will refer its own NPDB to know the porting status of called party for all scenarios which require NP check like Calls, SMS, and MMS etc. Connectivity: IP/TDM, Protocol: All GSM protocols (MAP, CAP, CS1+, CS1, CS2, INAP, SIGTRAN etc.

Below depicts the call flow for an ACQ scheme for ported out subscribers from the donor network for calls made by Post‐paid subscribers.

In the above flow:

An originating call is placed

Visited Mobile Services Switching Centre (VMSC) can send the GSM MAP Send Routing Information (SRI) message to the MNP‐SRF when receiving a call from the network.

The MNP‐SRF interrogates an internal or integrated NPDB for the RN of the MNP‐SRF of the wireless Current Serving Network and prefixes the RN to the


dialed wireless directory number in the global title address information in the SCCP Called Party Address (CdPA) parameter.

This SRI message will be routed to the MNP‐SRF of the wireless Current Serving Network, which then responds with an acknowledgement by providing the RN plus the dialed wireless directory number as the Mobile Station Roaming Number (MSRN). The GMSC of the wireless donor network formulates the ISUP IAM with the RN plus the dialed wireless directory number in the CdPN parameter and routes the call to the wireless Current Serving Network.

A GMSC of the wireless Current Serving Network receives the call and sends an SRI message to the associated MNP‐SRF where the global title address information of the SCCP CdPA parameter contains only the dialled wireless directory number. The MNP‐SRF then replaces the global title address information in the SCCP CdPA parameter with the address information associated with a Home Location Register (HLR) that hosts the dialed wireless directory number

STP forwards the message to that HLR after verifying that the dialed wireless directory number is a ported‐in number.

The HLR then returns an acknowledgement by providing an MSRN

STP then passes on the MSRN information to the GMSC handling the call.

The GMSC then routes the call to the VMSC that currently serves the mobile station that is associated with the dialed wireless directory number.


When the same call is placed by a prepaid subscriber the IN/SCP gets involved in the call flow as below

The essence of the call flow is that the NPDB is used to modify the SCCP Called Party Address parameter in the GSM MAP messages so that they can be redirected to the wireless serving network.

There is also a network option to add a new ISUP parameter called Number Portability Forwarding Information parameter. This parameter has a four‐bit Number Portability Status Indicator field that can provide an indication whether number portability query is done for the called directory number and whether the called directory number is ported or not if the number portability query is done.

All of the NP enhancements for a ported number can only be used in the country that defined them. This is because number portability is supported within a nation. Within each nation, the telecommunications industry or the regulatory bodies can decide which method or methods to use.

For Mobile Number Portability in the CDMA domain wherein the ported number is from a GSM to CDMA operator the end user has an additional onus of switchover to a GSM band handset. This is an additional capital cost to be borne by the subscriber.


In terms of MNP call flow for the CDMA network the NPDB interface will handle the ported number translation with the termination call translation being handled by the GMSC query to the NPDB much as in a GSM network. Only the Routing Instructions will ride the ANSI IS‐41 protocol stack converging through ANSI SCCP and ANSI TCAP as depicted below.


MNP Business Opportunities To understand the opportunities in the field of MNP it is imperative to understand the challenges faced for implementing and sustaining the MNP scheme. Cutting across all service providers or the central regulatory body for sustaining the MNP infrastructure, the identified cost element would be as follows:

Centralized NPDB setup cost

Upgrading the Signaling infrastructure to support NPDB routing

Network interface and software upgrade for supporting elements in the MNP ecosystem like HLR, MSC, GMSC, SMSC, MMSC, STP, Signaling gateway etc

Upgrade of BOSS component software

System for provisioning of NPDB and the UI interfaces

Customer Relationship Management (CRM) enhancement

IVR/IP interface upgrade for interactive provisioning and support

Software and system upgrade maintenance lines to keep up with regulatory changes

Thus there is a broad spectrum of activities in the Software services and Network Integration space that need to be put in place for a sustainable MNP ecosystem. As India heads for a billion mobile subscriber counts and a continuous pressure of churn due to price pressure or otherwise, there is a likelihood of frenzied activity in the MNP space. As knowledge and understanding of the scheme becomes a commonplace the volume in the MNP space will gain critical mass.

Software services bodies like Tech Mahindra can shoulder the responsibility of de‐entangling the back‐office complexities of the MNP scheme. Depending on the maturity levels of MNP ecosystem, a new porting request can take 2 hrs in the US to a span of 5 days in UK. The challenge is likely to be even severe in India in its nascent stage in MNP implementation. Our long experience and maturity levels in optimizing complex software components and process can go a long way to shape up the system. Let’s understand that end customer satisfaction and confidence shall be the only key to success for this new scheme and budding service providers in the Telecom provider space can gain a significant mass of subscribers only when a healthy competition is put in place.

MNP also impacts the internet telephony or VOIP business. A VOIP originated voice call with a termination on traditional mobile operator need to be aware of the porting status of the mobile subscriber before the call can be routed. Thus VOIP now need to know the current serving network for call routing purposes. Immense opportunities exists in creating a Voice Network Query service, which helps VOIP


providers to query the GSM network to find out the home network of a ported number.

The final word is today with ever diminishing ARPU’s for traditional telephony providers around the world , there are only 2 paths for survival, one is to aggressively promote data services, the other is to facilitate a healthy subscriber churn across providers, so that the one with the best of services attracts the most numbers. MNP levels the playing field, giving all market players a relatively equal opportunity to acquire customers.


Tech Mahindra’s role in MNP With over a two decade leadership and large talent pool catering to the product engineering space for the Telecom vertical, Tech Mahindra is well equipped with the right capability to serve the MNP value chain. Some of the capability areas aligned with the MNP market demands are as follows:

Infrastructure Management: The NPDB infrastructure and its fault tolerant availability needs a robust IMS practise which Tech Mahindra has in place.

Switching and signalling expertise: Tech Mahindra is one of the most respected names in the Switching and Signalling capability domain in terms of product engineering, R&D and SI practices. The backbone to MNP implementation is a complex mesh of Signalling layer capabilities that needs deep domain knowledge of signalling.

Application development: MNP enablement and mass penetration needs intuitive CRM and interactive applications portfolio. The capability can be further extended to NP query optimisation

Billing: Monetizing the MNP business through BSS enablers and appropriate Rating and Charging of rerouted traffic is essential for ensuring the revenue stream post porting migration. Our BOSS capabilities are in line with the required capabilities.

Testing and Verification: Finally the entire upgrade path and continuous regulatory evolution around this space need to be well managed through a fool‐proof QA cycle which the Tech Mahindra’s testing services with various in‐house automation tools and well equipped IOT labs can very efficiently manage.

The crux of the statement is Tech Mahindra has what this industry needs for a successful implementation of MNP and a symbiotic relationship can be woven between Tech Mahindra, Service providers, TEM and NP Clearing Houses to script the success story.


References

1. IETF

RFC 3482: Number Portability in the Global Switched Telephone Network

2. Gartner report on Indian Cellular services

Documents

Mobile numberportability