NTT DoCoMo Inc., the nation's biggest mobile phone carrier, plans to spend about 1.5 times its annual profit to strengthen its network as it banks on a surge in smartphone use to end a four-year decline in revenue.

The carrier may raise capital outlays to about ¥730 billion in the 12 months starting April 1, from a previous plan for ¥700 billion, Chief Financial Officer Kazuto Tsubouchi said Feb. 14 in Tokyo. The company is maintaining its target to increase operating profit 3.4 percent to ¥900 billion in the next fiscal year, he said, without elaborating.

DoCoMo is adding wireless capacity as more of its 58 million customers stream or download video, swelling an onslaught of data that in January contributed to a fifth service disruption in eight months. Revenue from data transmission has exceeded that for voice at the carrier since the quarter that ended last March 31, according to figures from the company.