Ultra Broadband And 60 Ghz Beam Forming Technology Research In The System

Ultra-Wideband (UWB) and60GHz wireless systems adopt orthogonal frequencydivision multiplexing (OFDM) and multiple antenna techniques to enhance theperformance. As one of multi-antenna techniques, beamforming (BF) shapes thetransmit signal to suppress interferences, increase signal to noise ratio (SNR) and thecoverage as well as improve the data rate.Beamforming is expected to play an important role in UWB and60GHzcommunications. Different from cellular systems, UWB and60GHz systems aresubjected to equivalent isotropic radiated power (EIRP) constraints. Therefore, it maynot be appropriate to directely apply conventional beamforming and we have tore-investigate and/or re-invent beamforming for UWB and60GHz systems. This thesisfocuses on beamforming technology for multiple-input multiple-output UWB and60GHz communications. The chapters are outlined as follows:The first chapter presents the background and the state of the art of beamformingtechniques in UWB and60GHz systems, and then describes the organization of thethesis.In chapter two, we first introduce the system model featuring multi-antennamulti-carrier beamformed transmission and detection, then we investigate channelmodels of UWB and60GHz systems, and finally we discuss conventional beamformingtechniques.In chapter three, combining the optimal beamforming (Optimal BF) and the beamswitching (BS), a hybrid beamforming algorithm is developed. Using the criteria: powergain and spectral efficiency, we compare the developed hybrid beamforming with theoptimal BF and the BS through extensive simulations. Finally, for different antennaarrays, we evaluate the performance the hybird beamforming in terms of power gainand spectral efficiency with varying the number of array elements.In chapter four, based on the existing beamforming algorithms, we propose a novelbeamforming, named as advanced antenna subset selection (AASS) to enhance the biterror rate (BER) performance subjected to transmit EIRP constraints. Furthmore, exploiting the inherent correlation between adjacent subcarriers, subcarrier-grouping isemployed to reduce the computation burden. In addition, the search strategy in AASSalgorithm is improved to enhanve the system performance. The advantages of theproposed techniques are verified through simulations over UWB and60GHz channels,respectively.The last chapter summarizes the research results obtained and points out thepossible future research directions.