The originating network will perform number portability database query to get the location routing number to route the call directly to the recipient network. Location routing number is a 4-digit unique number allotted by DoT to all mobile operators for each circle to identify individual networks. All ported number calls are routed on the basis of location routing number. So when the MNP database receives a query for a given mobile station international subscriber directory number (MSISDN), the database returns the MSISDN prefixed with location routing number.
Mobile number portability was started as a pilot project in Haryana on November 25, 2010 and has been implemented across the nation from January 20, 2011. The detailed MNP process is shown in Fig. 6.
At present, the only restriction is that mobile number portability is allowed within the same circle (intracircle operators). Recently, the government of India approved New Telecom Policy-2012 (NTP), which aims to abolish roaming charges across the country and facilitate nationwide (inter-circle) mobile number portability, i.e., one-nation-one-number with free roaming. This will allow users to change the operator without changing their mobile number even if they move from one circle to another. DoT has been asked to start nationwide MNP implementation and it is expected that the inter-circle MNP will start very soon.
Network architecture for MNP
Network architecture for MNP is shown in Fig. 7. The network is deployed in a redundant and synchronised way in two different geographical areas—one as a production site and the other as a disaster recovery site—to avoid interruption in service due to failure of one site.
Depending upon the requirement and network topology, the service provider can either directly connect to the central number portability database (CNPDB) or deploy separate local number portability database (LNPDB) and connect it to the CNPDB through its number portability gateway. The CNPDB and LNPDB should be syn-chronised.
When a call is originated, the visited mobile switching centre interrogates an internal (LNPDB) or external database (CNPDB) to get the location routing number of the correct terminating network. The CNPDB can be integrated with the signaling transfer point and accessed via an application programming interface locally, or a query can be made to a remote CNPDB through number portability gateway using protocols like simple object access protocol and extensible markup language. Here MNP translations are performed by the signaling transfer points. The signaling transfer point receives the location routing number query from the visited mobile switching centre and routes it to the appropriate signal control point.
The signal control point is a high-transaction-oriented server that receives number portability requests from the visited mobile switching centre and passes on the mobile station routing number information to the gateway mobile switching centre handling the call. The gateway mobile switching centre then routes the call to the currently serving visited mobile switching centre of the recipient operator.
The road ahead
About a year into its operation in India, the service provider number portability has failed to enthuse customers. It is expected to gain momentum once the National Telecom Policy’s proposals of abolishing the inter-circle roaming charges and extending MNP to national level are implemented.
The author joined Bharat Sanchar Nigam Limited as junior telecom officer and is currently working in Ludhiana, Punjab. He holds Ph.D. degree in electronics engineering from Indian Institute of Technology-BHU, Varanasi, India, and has authored and co-authored more than 25 research papers