India, Feb. 18 -- Mention the likes of Iliad and Reliance Jio in the company of traditional telcos and you might just kill the conversation. Both operators have stormed into their respective markets with a different way of thinking about commercial offerings and technology, unencumbered by legacy baggage. The impact on the old school has been devastating.

Now you can add a new name to the list of disruptors: Rakuten. The Japanese ecommerce player, with about 100 million customers, last year announced bold plans to build a greenfield fourth mobile network in one of the world's most developed telecom markets. Last week, it published details of its network plans and the partners it would use.

For rival operators NTT DoCoMo, KDDI and SoftBank...