MIMO-OFDM Subband Beamforming
Date Issued
2015
Date
2015
Author(s)
Ma, Shih-Hsun
Abstract
In a wireless communication link, multiple-input multiple-output (MIMO) techniques have been developed to increase throughput and reliability of data transmission by employing multiple antennas at the transmitter and the receiver sides. Other than MIMO technique, orthogonal frequency-division multiplexing (OFDM) is also a promising technique and widely adopted in many recent and future wireless communication standards since it can make very efficient use of available spectrum and be easily combined with other existing communication techniques. Specifically, transmit beamforming and receive beamforming are simple and popular methods for performance enhancement in multiple-input multiple-output and orthogonal frequency-division multiplexing (MIMO-OFDM) systems. However, the optimal beamforming scheme requires channel state information in form of the beamforming vectors for each OFDM subcarriers, which is referred to as subcarrier-wise beamforming. In this thesis, a subband beamforming is developed for MIMO-OFDM systems to maximize the mutual information. It is shown that the proposed scheme can provide the performance approaching that of the subcarrier-wise beamforming, while reducing both computational complexity and feedback requirements significantly. Besides, two implementation structures are developed to implement the proposed subband beamforming and compared with the existing schemes . Moreover, computational complexity and feedback requirements among various beamforming schemes are discussed. Numerical simulations show that the proposed scheme provides a better performance/feedback trade-off than existing beamforming schemes.
Subjects
multiple-input multiple-output (MIMO)
orthogonal frequency-division multiplexing (OFDM)
frequency-selective Rayleigh fading channel
beamforming
Type
thesis
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