NTT DoCoMo achieved 2.5Gbps packet transmission in the downlink while moving at 20km/h. The fourth-generation (4G) radio access field experiment took place in Yokosuka, Kanagawa Prefecture on December 14, 2005.

DoCoMo achieved a maximum 1Gbps speed in a similar field experiment on May 9, 2005. This time, by increasing the number of MIMO transmission antennas from four to six and by using 64-QAM, data volume per transmission was increased from four bits to six bits. As a result, DoCoMo achieved a maximum speed of 2.5Gbps, which is faster than the International Telecommunication Union Radiocommunication Sector (ITU-R)'s proposed standard.

Frequency spectrum efficiency, which is expressed as information bits per second per Hertz, was also increased from 10 bits per second per Hertz during the last experiment to 25 bits. This figure is the maximum frequency spectrum efficiency for 4G as defined by WINNER.

Building on the success of the field trials, DoCoMo will continue its research and development in order to actively contribute to the global standardization of 4G.

Notes

• MIMO: Multiple-Input Multiple-Output. Data transmission scheme to increase the achievable data rate, in which different data streams are spatially multiplexed using multiple transmitter and receiver antennas on the same frequency.
• QAM: Quadrature Amplitude Modulation. Modulation scheme which conveys data by changing the amplitude and phase. For example, 64QAM transmits one of 64 signal points and conveys six bits per one symbol.
• Spectral efficiency: Defined by the ratio between the transmission data rate and the channel bandwidth. The spectral efficiency of this experiment is 2.5Gbps/100MHz=25bps/Hz.
• WINNER: Wireless world INitiative NEw Radio. WINNER is a EU research project started in January 2004. This project aims to develop a ubiquitous radio system concept based on global requirements for mobile communication systems beyond 3G.