NTT DoCoMo hits 300Mbps in 4G research

Even if it was only a test in an ideal setting, NTT DoCoMo Inc. beat its own projected maximum transmission speed for new 4G (fourth generation) mobile broadband phones.

At last week's International Conference on Beyond 3G Mobile Communications in Tokyo, the Japanese operator said it achieved a maximum downstream data rate of 300Mbps (bits per second), with an average rate of 135Mbps. The data rate was achieved during a field experiment in a car running at a speed of 30 kilometers per hour at distances between 800 meters and 1 kilometer from 4G wireless base stations.

Until now, NTT DoCoMo has only talked about download speeds of 100Mbps. And while acknowledging 300Mbps data rate achieved during the field tests, NTT DoCoMo spokesman Takumi Suzuki said the speed was "not a normal rate but a temporary rate within a very limited environment," adding that the operator's planned data rate for 4G network service remains at 100Mbps.

NTT DoCoMo, which has been conducting 4G research since 1998, demonstrated a data rate of 100Mbps for the downlink and a rate of 20Mbps for the uplink in October 2002.

New 4G technology is being designed to provide, above all, higher data rates than the 3G (third generation) systems currently being rolled out around the world. 3G systems offer download speeds of 384Kbps and upload speeds of 129Kbps. The technology, however, is capable of a theoretical speed up to 2Mbps in a stationary position under ideal conditions.

At its Yokosuka research center, NTT DoCoMo has been testing VSF-OFCDM (Variable Spreading Factor Orthogonal Frequency and Code Division Multiplexing) and VSF-CDMA (Variable Spreading Factor Code Division Multiple Access) technologies. VSF-OFCDM enables downlink connections of extremely high speeds, both indoors and outdoors, while VSF-CDMA supports high-speed, high-efficiency packet transmissions for the uplink.

At the Telecom World 2003 exhibition in Geneva last October, NTT DoCoMo Executive Vice President and Chief Technology Officer Kota Kinoshita said the operator is targeting commercial service by 2010. According to Kinoshita, discussions are already underway with the International Telecommunication Union (ITU) about service requirements and spectrum.