NTT DoCoMo is currently in the early stages of setting up an experimental pilot system for 4G services with data transfer speeds in excess of 100 Mbps downlinks and 20 Mbps uplinks.
There's one thing that NTT DoCoMo can't be accused for, and that's pessimism. Even though 3G hasn't even been launched in most parts of the world yet, combined with a veritable slew of doomsayers that predict that 3G will never be the success it was hyped to be, NTT DoCoMo is already busy setting up its own pilot system to test out 4G services with transmission speeds in in excess of 100 Mbps downlinks and 20 Mbps uplinks.
4G services aren't due to arrive anytime soon though, as the experimental system, which will incorporate base station and mobile station equipment, is meant to demonstrate key technologies for a 4G wireless communications system that NTT DoCoMo hopes to launch commercially by 2010.
4G communications will feature extremely high-quality video equal to that of high-definition television, or more than double the resolution of conventional analog television. In addition, it will enable wireless downloads at speeds exceeding 100 Mbps, about 260 times faster than DoCoMo's recently introduced 3G wireless network. This summer, DoCoMo will begin practical evaluations of key technologies for its 4G packet wireless communications system, as well as implement the experimental system to demonstrate their benefits.
A 4G wireless system offering high-speed transmission of large-capacity data requires a bandwidth of approximately 100 MHz. When using a channel with such a broad bandwidth, however, transmission quality can be impaired by multipath, the occurrence of a large number of secondary signals reflected off buildings, mountains and other surrounding objects. NTT DoCoMo's experimental 4G system employs variable spreading factor (VSF) and orthogonal frequency code division multiplexing (OFCDM) technologies to mitigate the impact of severe multipath interference and thereby achieve a broad-bandwidth, large-capacity wireless system available on a nationwide basis.
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