NTT DoCoMo achieved 1 Gbps real-time packet transmission in a wireless downlink at a moving speed of about 20 km/h in a field experiment on fourth-generation (4G) radio access technology. The experiment took place last month in Yokosuka, Kanagawa Prefecture.NTT DoCoMo said the 1 Gbps transmission was realized through Variable Spreading Factor-Spread Orthogonal Frequency Division Multiplexing (VSF-Spread OFDM) radio access and 4-by-4 Multiple-Input-Multiple-Output (MIMO) multiplexing. The MIMO used a technique called "adaptive selection of surviving...