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Richard Ball -- Electronics Weekly A fourth generation mobile phone system has achieved download speeds of 1Gbit/sec. in tests carried out by NTT DoCoMo. The Japanese company tested the 1Gbit/sec. packet transmission system with target moving at 20km/h, it said. To realize such a download speed, DoCoMo used a coding technique called variable spreading factor-spread orthogonal frequency division multiplexing (VSF-Spread OFDM). This was coupled with a 4x4 multiple input, multiple output (MIMO) antenna system. DoCoMo claimed that using a 100MHz bandwidth, the spectral efficiency of the system is 10bits/sec./Hertz, or 20 times more efficient than 3G. |