Fractional Fourier Transform based Beamforming for Next Generation Wireless Communication Systems

摘要

Today's mobile communication systems are primarily designed to provide cost efficient wide area coverage for a limited number of users with moderate bandwidth. The future telecommunication will provide the same services in a wireless fashion as provided by fixed network these days and thereby requiring high bandwidths. It is expected that future telecommunication users will be neither willing to sacrifice functionality for the added value of mobility nor to pay more for it - mainly because he will hardly be using any other stationary telecommunication devices. Third generation mobile systems proposals such as UMTS and IMT-2000 only partially address these requirements by providing mobile internet services. with up to 2 Mbps in certain areas. Thus future mobile and wireless applications will require significantly higher data rates and significantly reduced costs per transmitted bit as compared to third generation systems. These requirements on data rate, link quality, spectral efficiency, and mobility cannot be met with conventional beamforming. Therefore new beamforming techniques are essential to increase the spectral efficiency of wireless communication systems. This paper provides the results achieved through use of a new technique Fractional Fourier transform (FRFT) based beamforming which is especially useful in moving and accelerating source problem. The conventional Minimum Mean Squared Error (MMSE) beamforming in the frequency domain or spatial domain becomes a special case of optimal beamforming with FRFT. The advantage of the proposed optimum FRFT domain beamformer is the practical consideration that the synthesis or analysis of the FRFT can be implemented with the same complexity as the conventional Fast Fourier Transform (FFT).