NTT Docomo, Japan’s number one operator by subscribers, aims to unveil a 150Mb/s LTE-based service by the end of the year, according to Engadget.

The initial rollout, says the report, will focus on the cities of Nagoya, Osaka and Tokyo.

The Japanese operator has apparently not decided on which frequencies it will use for the faster “Xi” branded 4G service, but there is some speculation it will re-farm some 1700MHz spectrum assets currently used for 3G.

It is also unclear as to exactly how Docomo will achieve these speeds. Earlier this year the operator announced plans to deploy LTE-Advanced services by 2015, which would increase theoretical peak speeds beyond the 100 Mb/s it is reported to be planning this year.

Complementing its plans to boost Xi speeds this year, NTT Docomo says it aims to double the number of LTE Xi base stations from 24,400 in March to 50,000 by the end of 2013.

NTT Docomo has 10 million subscribers to its LTE service since launch in 2010.

The LTE announcements come shortly after the Japanese operator announced its “2013 summer lineup” of new devices, which includes nine smartphones and one tablet. Each support LTE.