With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G)...With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.展开更多
A new calibration model of a radio telescope that includes pointing error is presented, which considers nonlinear errors in the azimuth axis. For a large radio telescope, in particular for a telescope with a turntable...A new calibration model of a radio telescope that includes pointing error is presented, which considers nonlinear errors in the azimuth axis. For a large radio telescope, in particular for a telescope with a turntable, it is difficult to correct pointing errors using a traditional linear calibration model, because errors produced by the wheel-on-rail or center bearing structures are generally nonlinear. Fourier expansion is made for the oblique error and parameters describing the inclination direction along the azimuth axis based on the linear calibration model, and a new calibration model for pointing is derived. The new pointing model is applied to the 40 m radio telescope administered by Yunnan Observatories, which is a telescope that uses a turntable. The results show that this model can significantly reduce the residual systematic errors due to nonlinearity in the azimuth axis compared with the linear model.展开更多
Rapid growth in mobile computing and other wireless multimedia services isinspiring many research and development activities on high-speed wireless communication systems.Main challenges in this area include the develo...Rapid growth in mobile computing and other wireless multimedia services isinspiring many research and development activities on high-speed wireless communication systems.Main challenges in this area include the development of efficient coding and modulation signalprocessing techniques for improving the quality and spectral efficiency of wireless systems. Therecently emerged space-time coding and signal processing techniques for wireless communicationsystems employing multiple transmit and receive antennas offer a powerful paradigm for meeting thesechallenges. This paper provides an overview on the recent development in space-time coding andsignal processing techniques for multiple-input multiple-output (MIMO) communication systems. Wefirst review the information theoretic results on the capacities of wireless systems employingmultiple transmit and receive antennas. We then describe two representative categories of space-timesystems, namely, the BLAST system and the space-time block coding system, both of which have beenproposed for next-generation high-speed wireless system. Signal processing techniques for channelestimation and decoding in space-time systems are also discussed. Finally, some other coding andsignal processing techniques for wireless systems employing multiple transmit and receive antennasthat are currently under intensive research are also briefly touched upon.展开更多
基金supported by the National High Technology Research and Development Program of China (863 program) of China under Grant No.2011AA010200 supported by the National Natural Science Foundation of China (NSFC) under Grant No.61771116 and No.91738102
文摘With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.
基金Supported by the National Natural Science Foundation of China
文摘A new calibration model of a radio telescope that includes pointing error is presented, which considers nonlinear errors in the azimuth axis. For a large radio telescope, in particular for a telescope with a turntable, it is difficult to correct pointing errors using a traditional linear calibration model, because errors produced by the wheel-on-rail or center bearing structures are generally nonlinear. Fourier expansion is made for the oblique error and parameters describing the inclination direction along the azimuth axis based on the linear calibration model, and a new calibration model for pointing is derived. The new pointing model is applied to the 40 m radio telescope administered by Yunnan Observatories, which is a telescope that uses a turntable. The results show that this model can significantly reduce the residual systematic errors due to nonlinearity in the azimuth axis compared with the linear model.
文摘Rapid growth in mobile computing and other wireless multimedia services isinspiring many research and development activities on high-speed wireless communication systems.Main challenges in this area include the development of efficient coding and modulation signalprocessing techniques for improving the quality and spectral efficiency of wireless systems. Therecently emerged space-time coding and signal processing techniques for wireless communicationsystems employing multiple transmit and receive antennas offer a powerful paradigm for meeting thesechallenges. This paper provides an overview on the recent development in space-time coding andsignal processing techniques for multiple-input multiple-output (MIMO) communication systems. Wefirst review the information theoretic results on the capacities of wireless systems employingmultiple transmit and receive antennas. We then describe two representative categories of space-timesystems, namely, the BLAST system and the space-time block coding system, both of which have beenproposed for next-generation high-speed wireless system. Signal processing techniques for channelestimation and decoding in space-time systems are also discussed. Finally, some other coding andsignal processing techniques for wireless systems employing multiple transmit and receive antennasthat are currently under intensive research are also briefly touched upon.
