NTT DoCoMo begins experimental 4G network construction

With its third-generation (3G) wireless service barely off the ground, NTT DoCoMo Inc. has begun research and development on fourth-generation (4G) packet wireless technology and started constructing an experimental network system, the company said Monday.

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 such 4G networks will be capable of data transmission at speeds of up to 100M bps (bits per second) downstream and 20M bps upstream when they are commercialized around 2010.

Tokyo-based 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 W-CDMA (Wideband Code Division Multiple Access) 3G network that began commercial service in October last year.

The high speeds will also 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 dipped its toes into the 4G water and begun working on related technologies with Hewlett-Packard Co. as early as November 2000. The two companies announced the work in June last year and said they are working together to develop a better way of delivering streaming media to cell 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 100M-bps speed goal for the systems by 2010.