The Roadmap to 4G After Achieving 2.5Gbps Transmissions

4G is considered the most important development for the future. To this end, NTT DoCoMo has been racking up steady achievements, succeeding in outdoor experiments to attain packet signal transmissions at a maximum rate of 1 Gbps in May 2005 and a world's-first packet signal downlink speed of 2.5 Gbps in December 2005. What impact does this successful 2.5 Gbps packet signal transmission have?
"Success in our 2.5 Gbps transmission experiment means that we are close to the peak for efficiency in frequency utilization for 4G mobile phones. This can be considered one of the milestones in achieving 4G. In addition, we have also developed ASESS technology with the capability of separating a signal using just a quarter of the computational power required by previous methods. The possibility of packaging this signal separation technology - previously requiring a supercomputer - in a mobile terminal is now clear, and so our future plans are focused on optimizing the technology in a variety of propagation environments."

So what is the next step towards 4G?
"There are still a number of problems to be solved to materialize 4G technology. One major point is packaging it all into a mobile terminal. Specifically, we have to develop a way of packaging into a terminal the MIMO multiplexing technology that enables transmitting different signals from multiple antennas on the same frequency at the same time. Additionally, since MIMO requires high processing speed which in turn requires more power, the issue of power supply becomes another barrier. The recent 2.5 Gbps transmission experiment was our response to the challenge of achieving the full limit of frequency spectrum efficiency in mobile communications, and we believe we have cleared it. It is certainly no exaggeration to say that the door to 4G is definitely opening."

4G mobile phone services are expected to start in 2010, but the technology required is already taking concrete form at NTT DoCoMo.