Improved Blind Beamforming of Eigen-based Schemes in OFDM Systems with Virtual Carriers

• Main Authors: Wei-min Kan, 甘偉民
• Other Authors: Yung-fang Chen
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/30443312009420209421

碩士 === 國立中央大學 === 通訊工程學系在職專班 === 103 === The Orthogonal frequency division multiplexing (OFDM) communication system is adopted for transmission by Evolved-Universal Terrestrial Radio Access Network (E-UTRAN). A former research, “Adaptive Antenna Arrays for Interference Cancellation in OFDM Communication Systems With Virtual Carriers”, can cancel strong co-channel interferences to achieve competitive performances. This research is based on Eigen-analysis and it estimates the spatial correlation matrix of signal-plus-interference-plus-noise by choosing samples from information subcarriers (nonzero-value) and estimates the spatial correlation matrix of interference-plus-noise by selecting samples from virtual subcarriers (zero-value) in one OFDM symbol duration. The solution of the beamforming weight vector by Eigen-analysis is the “largest” generalized eigenvector corresponding to the estimated matrix pencil. Unfortunately, those schemes look perfect but their performances become worse as the increasing of subcarriers. In this thesis, we find out the reason for bad performances and utilize the “idle data subcarriers” to enhance the estimation of spatial correlation matrix. Besides, we propose the “2D-grouping” method to improve the bad performance problem even the subcarrier number equals to 2048 that is the maximal number of subcarriers in E-UTRAN. Finally, this thesis also develops the scheme to decide the grouping range in frequency and time domains by a serious of experiments.