Come January and all mobile phone users will have 11-digit mobile numbers instead of their 10-digit numbers currently.

The Department of Telecommunications (DoT) has amended the National Numbering Plan 2003 for migration to an 11-digit numbering plan in mobile services by prefixing the number '9' to the existing two-digit PLMN Access Code.

A PLMN is identified by the Mobile Country Code (MCC) and the Mobile Network Code (MNC). Every service provider has its own PLMN, which interconnects with other PLMNs and public switched telephone networks (PSTNs) for telephone communications, or with internet service providers for data and internet access.

The proposed migration from the existing 10-digit number to an 11-digit numbering plan is likely to be implemented from January 1, 2010, according to an internal DoT note.

A new numbering plan was required because India's mobile subscriber base has grown at a faster pace than expected. The numbering plan that is applicable now was formulated in 2003 on a forecast of 50 per cent teledensity by 2030.

This allowed for 750 million telephone connections, comprising an anticipated 300 million basic and 450 million cellular mobile connections.

With India adding over 10-14 million mobile subscribers each month, the wireless subscriber base has already crossed 500 million, a year ahead of the target. Therefore, DoT has to re-examine plans to accommodate more subscribers.

This is not the first time phone numbers will be modified. A few years ago, the government had prefixed the number '2' to all BSNL and MTNL fixed-line phones across the country to accommodate more connections.