http://neasia.nikkeibp.com/wcs/leaf/CID/onair/asabt/news/310782 June 1, 2004 (TOKYO) -- NTT DoCoMo Inc revealed at the International Conference on Beyond 3G Mobile Communications-2004 (ICB3G-2004) the detailed test results of its 4G field experiment now being conducted at Yokosuka, Kanagawa prefecture. The ICB3G is an international conference on fourth-generation (4G) mobile communication systems. It was held on May 26 and 27, in Tokyo. The company said that the test achieved a maximum downstream data rate of 300Mbps with an average rate of 135Mbps in a car running at the speed of 30 kilometers per hour in areas 800m to 1km away from the 4G wireless base stations. NTT DoCoMo aims to realize much faster communication speeds by adding the multiple input, multiple output (MIMO) technology, which uses multiple antennas, to the current wireless system. The goal of the wireless data rate is as high as 1Gbps when not moving. The experiment will continue until July. The communication methods that NTT DoCoMo is using for the test are the variable spreading factor, orthogonal frequency and code division multiplexing (VSF-OFCDM) method for the downstream transmission, and the direct spread code division multiple access (DS-CDMA) method for the upstream. The error correction codes used for this system are Turbo codes. The frequency bandwidths for the test are 100MHz in width with the 4.635GHz radio signal at its center, and 30MHz in width with the 4.9GHz radio signal at its center for the downstream and upstream channels, respectively. The test of the car moving at 30 kilometers per hour achieved average data rates of 135Mbps for downstream and more than 20Mbps for upstream communications in the environment where the wireless base stations are not visible from the car because of buildings. Also, the company said that the quality test of two channels of high-definition television (HDTV) video signals distributed at 25Mbps each resulted in a stable video quality. The moving car test recorded a downstream data rate of 300Mbps even at the speed of 30kph when the wireless base stations are visible from the car. This is because the 64-Quadrature Amplitude Modulation (QAM) technique can be leveraged when the environmental conditions for communications are good. The definition of 4G that the International Telecommunication Union - Radiocommunication Standardization Sector (ITU-R) approved in June 2003 states that the data rate should be around 100Mbps when moving fast like in a train, and 1Gbps when not moving. An official at NTT DoCoMo said, "In order for us to realize 300Mbps or more, it will be necessary to make such an effort as integrating the MIMO method to the existing wireless infrastructure." Moreover, the company expressed its intention to develop relevant systems, including the MIMO technology in the future. |