Cellphones capable of transmitting data at blistering speeds have been demonstrated by NTT DoCoMo in Japan.
In experiments, prototype phones were used to view 32 high definition video streams, while travelling in an automobile at 20 kilometres per hour. Officials from NTT DoCoMo say the phones could receive data at 100 megabits per second on the move and at up to a gigabit per second while static. At this rate, an entire DVD could be downloaded within a minute. DoCoMo's current 3G (third generation) phone network offers download speeds of 384 kilobits per second and upload speeds of 129 kilobits per second.
The technology behind NTT DoCoMo's high-speed phone network remains experimental, but the 4G tests used a method called Variable-Spreading-Factor Spread Orthogonal Frequency Division Multiplexing (VSF-Spread OFDM), which increases downlink speeds by using multiple radio frequencies to send the same data stream.
Another wireless networking trick, called multiple-input-multiple-output (MIMO) multiplexing, was used to send data via various routes across a network, in order to further increase data capacity. For example, MIMO could enable a cellphone to receive data from more than one base station in range.
The activities "are technically impressive," says Lajos Hanzo, a communications expert at Southampton University in the UK. But Hanzo told New Scientist NTT DoCoMo will need assistance from other phone companies if it is to kick-start 4G uptake. "In today's world nobody can go it alone," he says. "And hence any standard proposal must be internationally ratified, which has not as yet take place."
Some countries have already begun cooperating on such standards. Japan and China signed a memorandum on 24 August to work together on 4G. NTT DoCoMo hopes to launch a commercial 4G network by 2010.