8 August 2012, 11 am
Beamforming techniques offer array gain and spatial multiplexing gain in multiple input multiple output (MIMO) systems. Wireless systems with massive numbers of transmit antennas (Massive MIMO) are attractive to increase the channel capacity and/or energy efficiency. However, the downlink channel state information (CSI) estimation sequence suffers increased loss in terms of lower MAC efficiency and calculation complexity. This paper proposes a CSI feedback scheme based random beamforming weights for massive MIMO when the number of users is small. In the proposed scheme, the CSI estimation beams are randomly determined and the number of beams for CSI estimation is limited. By iteratively revising the random beamforming weight, the access point can obtain the CSI of the signal space of all transmit antennas. Simulation results show that the achievable bit rate of the proposed method approaches that of the full antenna CSI.
Dr. Riichi Kudo received the B.S. and M.S. degree in geophysics from Tohoku University, Japan, in 2001 and 2003, respectively. In 2003, he joined NTT Network Innovation Laboratories, Yokosuka, Japan. He has been engaged in the MIMO communication systems and the beamforming methods. He received the Young Engineer Award from the Institute of Electronics, Information and Communication Engineers (IEICE), Tchnical Commitee of Antenna and Propagation, Technical Commitee on Optical Communication Systems, and IEEE AP-S Japan Chapter, Japan, in 2006, 2009, 2010, and 2011 and received the IEICE Best Paper Award in 2011. He is a visiting fellow at the Centre for Communications Research (CCR), University of Bristol. His current research interest is channel state information estimation for massive MIMO systems.