TOKYO -- Online retailer Rakuten aims to become Japan's fourth major mobile carrier, angling for a slice of wireless spectrum and gearing up to invest heavily in infrastructure.
NTT Docomo, KDDI and SoftBank Group control 90% of Japan's cellular market. There are some competitors -- including mobile virtual network operators, which rent network infrastructure -- offering low-cost smartphone plans, but the trio has protected their market share by offering similar inexpensive services. Opening a chink in their armor would usher in a new era of competition, and likely push down fees.
