Singaporean operator StarHub is rolling out a femtocell service that allows mobile subscribers to make calls at home using their broadband Internet connections instead of the cellular network.

StarHub's Home Zone service costs S$16.05 (US$10.62) per month with a 1-year contract. Users must also have a mobile-phone and broadband Internet accounts with StarHub for the service to work.

Each Home Zone account can support up to four StarHub mobile phone numbers.

When Home Zone users are at home, voice calls, text messages and video calls are sent over the broadband Internet connection. Users connect their mobile phones to the Internet using small, cellular base stations, called femtocells, that redirect calls over the Internet. An audio message that is played before each outgoing call and a new network name appear on the phone to alert users when their phones are connected to the femtocell.

The idea is that users who frequently make cell phone calls from home may save money by avoiding charges for cellular airtime with the femtocell service.

But there is a limit. StarHub still charges full mobile data rates for mobile downloads, MMS messages, and surfing the Internet using the cell phone.

The IDG News Service is a Network World affiliate.