"We are investing 163 million US dollars (18.5 billion rupees) to expand base stations and bring HSPA 28.8 megabits per second.
"We are bringing coverage investment, distributed all over the country with special emphasis on the North and the East," chief executive Duminda Ratnayaka said.
Ratnayaka said expansion of its broadband services will see HSPA (high speed packet access) technology with 28.8 megabits per second speeds.
Over 500 third generation (3G) base stations will be built on existing locations.
Alcatel-Lucent has been chosen as the vendor.
UAE-based Etisalat bought the Sri Lanka unit from Millicom Cellular International when it exited Asia. The firm says the expansion will be funded by debt at 'attractive terms' as the firm was virtually debt free and its parent is rated A+ by Fitch Ratings.
"We are virtually a debt free company,