Vodafone has today begun trials in Tokyo of a technology that could be used to upgrade its 3G network to offer multi-megabit-per-second data transmission.

The company will trial the technology, called HSDPA (high speed downlink packet access), for about four months, said Matthew Nicholson, a spokesman for Vodafone in Tokyo.

HSDPA is an upgrade to the existing WCDMA (Wideband Code Division Multiple Access) technology that allows data to be transmitted at speeds several times faster than the 384kbps (kilobits per second) currently available.

Several carriers around the world are looking at HSDPA. Most of them talk of an upgrade path that will initially bump transmission speeds to around 3Mbps, and later to about 14Mbps.

Among them, Japan's NTT DoCoMo has said it plans to offer commercial service by the end of March 2006, while in Europe O2 recently announced plans to offer HSDPA services, first on the Isle of Mann and then on the British mainland. Cingular Wireless LLC in the US has also talked about offering the upgrade on its 3G network in the future.

Last week Tokyo-based wholesale broadband internet provider eAccess said it hopes to begin tests of HSDPA in April, with a view to applying for a license to operate wireless services when the government offers additional wireless spectrum. Vodafone has also said it plans to test the system in New Zealand.

Other high-speed data technologies also exist, including Flash (fast low-latency access with seamless handoff) OFDM (Orthogonal Frequency Division Multiplexing), which was developed by New Jersey-based Flarion Technologies. The technology can support data transmission at about 3Mbps and Vodafone is also testing that system in Japan.