TelecomWeb reports that NTT DoCoMo today claimed that it had demonstrated a successful 2.5 Gbps downlink packet transmission while moving at 20 kilometers per hour in Yokosuka, Kanagawa Prefecture in December of last year. The article notes that the company didn't explain why it took so long to announce the test, which represents a current world record for the performance of wireless data sent to a moving vehicle.

This puts NTT DoCoMo squarely in the forefront of 4G technology -- the speed record, the company says, was achieved by increasing the number of Multiple-Input Multiple-Output (MIMO) transmission antennae from four to six, and by using 64-Quadrature Amplitude Modulation (QAM), which increased data volume per transmission from four bits to six bits.

And as Techworld.com points out, this is a vast improvement on NTT DoCoMo's last 4G demonstration earlier last year, in which the carrier reported that it had achieved speeds of 1 Gbps.

NTT DoCoMo's press release is here.