NTT DoCoMo, Japan's biggest mobile communications carrier, has achieved a 1Gbit/s packet transmission speed using fourth-generation (4G) mobile communication equipment. The company said that it reached this landmark in August, although it's only just released the information.

The company said that the downlink speed of 1Gbit/s had been achieved in a laboratory experiment using VSF-Spread OFDM (Variable-Spreading-factor Spread Orthogonal Frequency Division Multiplexing) and MIMO (multiple-input-multiple-output) technology.

VSF-Spread OFDM enables downlink connections of extremely high speeds. MIMO is a technique for boosting wireless bandwidth and range by taking advantage of multiplexing, which involves sending information in multiple paths so that each carries more information.

The transmitted data was carried in a single beam, but the amount of data was too big for a single antenna so scientists used four antennas, each sending 250Mbit/s streams of data, for the experiment, said DoCoMo spokesman Takuya Ori.

"It was a lab experiment and it was indoors, so the distance wasn't that far," he said.

DoCoMo has been conducting 4G research since 1998. Earlier this year, the company demonstrated a maximum downstream data rate of 300Mbit/s with an average rate of 135Mbit/s. The data rate was achieved during a field experiment in a car running at a speed of 30 kilometres per hour at distances between 800 metres and 1 kilometre from 4G wireless base stations.

DoCoMo's 3G network offers download speeds of 384Kbit/s and upload speeds of 129Kbit/s. The company plans to introduce a more advanced packet-based data service network technology called HSDPA (High Speed Downlink Packet Access) in 2005 that will have a 14Mbit/s speed for both downlink and uplink, according to DoCoMo spokesman Takumi Suzuki.

NTT DoCoMo's experiments are part of its research into developing a global standard for 4G transmission and networks with the International Telecommunication Union. Research in Japan is conducted in cooperation with Japan's Ministry of Internal Affairs and Communications.

DoCoMo would like to begin commercial services based on 4G in 2010, Suzuki said.