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An MMSE channel estimation algorithm based on the conjugate gradient method for OFDM systems
Shigenori Kinjo 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
In this report, we propose a new scheme in order to implement an MMSE channel estimator for OFDM systems. We know that the time domain maximum likelihood estimator (MSE) can achieve highly accurate impulse response estimation by using a time domain long preamble of an OFDM frame. On the other hand, the impulse response estimation based on the minimum mean square error (MMSE) criterion can achieve superior channel estimation in low SNR conditions; however, it requires prior statistical information such as delay profiles of channels. In addition, the computational complexity becomes large because of the inverse matrix calculation. In order to overcome these implementation issues, we propose to estimate the statistical values based on the observed information of the channel. In addition, we show that we can suppress the increase of the computational complexity for the matrix inverse calculation by applying the conjugate gradient method while achieving the same performance with the ideal MMSE estimator.
Tatsuto Kinjo,Tomonobu Senjyu,Naomitsu Urasaki,Hideki Fujita 전력전자학회 2004 ICPE(ISPE)논문집 Vol.- No.-
Utilizations of renewable energy are coming up from view points of environmental conservation and depletion of fossil fuel. However, the generated power from renewable energies is always fluctuating due to environmental status. Energy storage system is indispensable to compensate these fluctuating components. Superconducting magnetic energy storage (SMES) unit is useful for the compensation of fluctuating power since one is capable of controlling both active and reactive power simultaneously and quickly.<br/> This paper presents the series and parallel compensation using SMES (SPC-SMES), which consist of series inverter, parallel inverter, two-quadrant DC-DC converter, and superconductingcoil. The control systems for the active and reactive power of SPC-SMES are also proposes, and are verified the effectiveness through an instantaneous value analysis based computer simulations for case of wind power generation system.