NTT DoCoMo came close to hitting another data transmission milestone at the end of last year.

The company, Japan's leading cellular carrier, managed to transmit data at close to 5Gbit/s to a receiver moving at 10 kilometres per hour, said Yoshiki Kakuda, a spokesman for the Tokyo company.

About a year earlier NTT DoCoMo succeeded in transmitting data at 2.5Gbit/s and this time managed to double that by increasing the number of MIMO (multiple in multiple out) transmitting and receiving antennas from six to 12 each and using better signal processing in the receiver. MIMO involves sending data using multiple antennas to increase the total throughput.

The result was a doubling in the amount of data transmitted in the same 100MHz chunk of radio spectrum.

NTT DoCoMo has been working on what it calls 4G (fourth-generation) technology for close to 10 years but the technology remains some way from commercialisation. The carrier had previously said it plans to launch 4G in Japan around 2010 but recently indicated it plans to wring more speed out of its WCDMA (Wideband Code Division Multiple Access) 3G network before switching to a new technology.

The carrier plans to launch a "Super 3G (third-generation)" service around 2010 that will offer data transmission at around 100Mbit/s. When NTT DoCoMo launched its 3G network in 2001, it could carry data at 384kbit/s but that was recently raised to 3.6Mbit/s with the launch of an upgrade called HSDPA (high-speed downlink packet access). Carriers in other countries are also deploying the faster technology on their networks.