A major concern at NTT DoCoMo Inc., Japan’s largest mobile carrier, is to avoid becoming a “dumb pipe,” a telecommunications highway that merely carries data and voice communication between devices without offering much in terms of additional value.

It’s a legitimate concern in the era of the smartphone which has diminished the role of carriers while increasing the strain on networks to handle massive amounts of data. In the pre-smartphone age, DoCoMo controlled nearly every service within its network from offering ringtones...