Wednesday, June 22, 2005

NTT DoCoMo Achieves 1 Gbps in 4G Field Test

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 symbol replica candidate" (ASESS) based on Maximum Likelihood Detection with QR decomposition and the M-algorithm (QRM-MLD), which was developed by DoCoMo.

NTT DoCoMo said its new algorithm reduces the large computational complexity of the original MLD method while maintaining almost the same achievable throughput performance. Frequency spectrum efficiency, which is expressed as information bits per second per Hertz, is 10 bits per second per Hertz, about 20 times that of 3G radio networks' spectrum efficiency.

During an earlier trial in July 2003, DoCoMo achieved 100 Mbps and 20 Mbps data rate transmission in the downlink and uplink, respectively, in outdoor environments using the same 100MHz bandwidth.

DoCoMo's field trials are part of its program to develop a 4G global standard in cooperation with the International Telecommunication Union Radiocommunication Sector. The telecommunications council of Japan's Ministry of Internal Affairs and Communications aims to see 4G services commercialized in Japan by 2010.

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