NTT DoCoMo has beat its own projected maximum transmission speed for fourth-generation mobile broadband phones.
The Japanese operator said it achieved 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 going at 30kms per hour at distances between 800m and 1km from 4G wireless base stations.
Until now, NTT DoCoMo has only talked about download speeds of 100mbps. 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.
The technology for 4G is being designed to provide, above all, higher data rates than the 3G systems already being rolled out around the world. 3G systems offer download speeds of 38kbps and upload speeds of 129kbps. The technology, however, is capable of a theoretical speed up to 2mbps in a stationary position under ideal conditions.
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.
John Blau writes for IDG News Service