The network is being built at the company's research and development centre at the Yokosuka Research Park outside of Tokyo and will incorporate both experimental base station and mobile terminals, said Tomoko Honma, a company spokeswoman. NTT DoCoMo said it expects 4G networks will be capable of data transmission at speeds of up to 100Mbps downstream and 20Mbps upstream when they are commercialised around 2010.
NTT DoCoMo expects to begin practical evaluations of key technologies for 4G around the middle of this year.
To carry data at such a high speed, 4G networks will require more bandwidth than today's cellular systems. Each 4G channel is expected to occupy around 100MHz of spectrum - 20 times that of the carrier's Wideband Code Division Multiple Access (W-CDMA) 3G network that began commercial service in October last year.
However, the high speeds will pose new problems for engineers, such as being much more susceptible to interference from signals reflected off buildings, mountains and other objects near the user. To get around this, DoCoMo is planning to experiment with different techniques for encoding and transmitting the signal.
NTT DoCoMo has already begun working on 4G related technologies with Hewlett-Packard to develop a better way of delivering streaming media to mobile phones and mobile devices.
Fourth-generation networks are expected to combine today's 3G networks with wireless LAN systems. A working group of The International Telecommunication Union Radiocommunication sector (ITU-R) held discussions on 4G systems in Tokyo last year and set the 100Mbps speed goal for the systems by 2010.