Mobile number portability

Mobile number portability (MNP) enables mobile telephone users to retain their mobile telephone numbers when changing from one mobile network carrier to another.

Mobile number portability is implemented in different ways across the globe. The International and European standard is for a customer wishing to port his/her number to contact the new network (recipient), which then sends the number portability request (NPR) to the current network (donor). This is known as "recipient-led" porting. The UK and India are the only exceptions to implement the donor-led system. The customer wishing to port his/her number is required to contact the donor to obtain a code (Porting Authorisation Code (PAC) in the UK and Unique Porting Code (UPC) in India) which is then given to the recipient network. The recipient continues the porting process by contacting the donor with a porting code. This form of porting is known as "donor-led" and has been criticised by some industry analysts as being inefficient, though it prevents MNP scams. It has also been observed that it may act as customer deterrent as well as allowing the donor an opportunity of "winning back" the customer. This might lead to distortion of competition, especially in the markets with new entrants that are yet to achieve scalability of operation. Based on the recommendations of the Authority on MNP, dated 8 March 2006, the Department of Telecommunications (DoT) issued guidelines for MNP implementation in the country on 1st Aug 2008. Subsequently, the DoT selected two companies as MNP Service providers each serving in a designated zone in the country. As per the instructions of DoT dated 6 May 2009, a Port Transaction Charge will be charged by the MNP Service Provider from the recipient carrier for processing each porting request. The Dipping charge shall be payable by those telecom service providers who utilize the dipping services (query response services) from the MNP Service Provider. The Porting Charge is payable by the subscriber to the recipient carrier for porting his mobile number. The port transaction charge, dipping charges and the porting charge shall be governed by the Telecom Tariff Order (TTO)/ determination by TRAI.

A significant technical aspect of MNP is related to the routing of calls or mobile messages (SMS, MMS) to a number once it has been ported. There are various flavours of call routing implementation across the globe but the International and European best practice is via the use of a central database (CDB) of ported numbers. A network operator makes copies of the CDB and queries it to find out to which network to send a call. According to RFC3482, this is also known as All Call Query (ACQ) and is highly efficient and scalable. A majority of the established and upcoming MNP systems across the world are based on this ACQ/CDB method of call routing. One of the very few countries not to use ACQ/CDB is the UK, where once a number has been ported, calls to that number are still routed via the donor network. This is also known as "indirect routing" and is highly inefficient as it is wasteful of transmission and switching capacity. Because of its donor dependent nature, indirect routing also means that if the donor network develops a fault or goes out of business, the customers who have ported numbers out of that network will lose incoming calls to their numbers. The UK telecoms regulator Ofcom completed its extended review of the UK MNP process on 29 November 2007, and mandated that ACQ/CDB be implemented for mobile to mobile ported calls by no later than 1 September 2009.

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