NTT DoCoMo Inc., Japan’s biggest mobile carrier, is to spearhead the rollout of an advanced version of its third-generation (3G) services called Super 3G, a company spokesman said Wednesday.

Mobile carriers are expected to roll out Super 3G in the coming years as a defensive measure against the increasing speeds of other wireless technologies such as wireless LAN (WLAN) and the long-range WiMax standard, according to analysts.

The move will be a low-cost upgrade to the company’s current 3G Wideband Code Division Multiple Access (WCDMA) network. The upgrade, which will offer 100Mbps downlink and 50Mbps uplink speeds, will be rolled out in metropolitan areas initially and be operational by 2008, said spokesman Takumi Suzuki.

DoCoMo will not need to replace much equipment to improve the network, which can be completed more easily than the company’s 3G network, he said.

“We needed three years to get our 3G network running, but this network will take a much shorter time. We are targeting the 2007 to 2010 period,” he said.

Getting such a network running so quickly will probably prove difficult, said Kirk Boodry, telecom analyst with Dresdner Kleinwort Wasserstein (Japan) Ltd. in Tokyo.

DoCoMo will have spent about