NTT DoCoMo, Japan's biggest mobile communications
carrier, achieved a 1Gbps packet transmission speed using 4G)
mobile communication equipment in August, the company has
said.
A downlink speed of 1Gbps was achieved in a laboratory
experiment using VSF-Spread OFDM (Variable-Spreading-factor Spread
Orthogonal Frequency Division Multiplexing) and MIMO
(multiple-input-multiple-output) technology, according to
DoCoMo.
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 250Mbps streams of data, for the
experiment, said DoCoMo spokesman Takuya Ori.
"It was a lab experiment and it was indoors, so the distance was
not that far," he said.
DoCoMo has been conducting 4G research since 1998. Earlier this
year, the company demonstrated a maximum downstream data rate of
300Mbps with an average rate of 135Mbps.
The data rate was achieved during a field experiment in a car
running at 30 kilometers per hour at distances between 800 meters
and 1 kilometer from 4G wireless base stations.
DoCoMo's 3G network offers download speeds of 384Kbps and upload
speeds of 129Kbps.
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 14Mbps 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.
Paul Kallender writes for IDG News Service