Softbank president Masayoshi Son (right) introduces the world's first smartphone featuring a nuclear radiation detector, in Tokyo in May. The Japanese mobile phone operator is to acquire one of its smaller rivals, fourth-ranked eAccess Ltd, for $2.3 bn, the companies say.

Japanese mobile phone operator Softbank is to acquire one of its smaller rivals, fourth-ranked eAccess Ltd, for $2.3 billion, the companies said Monday.

will make eAccess a wholly owned subsidiary through a stock swap and hopes to use the company's available bandwidth to cope with sharply rising data traffic as Japan's huge rapidly adopts smartphones.

Tokyo-based Softbank, one of Asia's biggest Internet conglomerates, said the swap ratio values eAccess at 52,000 yen ($667) per share, making the company worth about 180 billion yen.

Softbank and eAccess will share base stations, saving Softbank new , one of the largest expenses for mobile operators.

Softbank was once the only Japanese mobile operator to offer the wildly popular iPhone, but now has a rival after KDDI Corp., the country's second-largest carrier, also struck a deal to carry Apple's handsets.

The buyout is expected to further intensify competition among industry leader NTT DoCoMo Inc., KDDI Corp. and Softbank.

Softbank and eAccess had a combined 34.3 million subscribers as of the end of August, the Nikkei daily said, still short of KDDI Corp. with 35.9 million subscribers.

Market leader DoCoMo has 60.6 million subscribers.

The deal is expected to be completed in February next year.