Implementation Of SDR MIMO System And Research On Beamforming

As the spectrum resources are constrained today, Multi-input Multi-output (MIMO) technology attracts much attention by virtue of multiply increasing system capacity without increasing the system bandwidth. Along with the increasing demand for MIMO technology, research on MIMO technology becomes an important research hotspot. However, most of ex-isting researches are performed or verified by computer simulation, because of the drawback that the computer simulation can't accurately simulate real communication environment, an effective development method for real communication system is particularly necessary.Software Defined Radio (SDR) technology is a scheme to construct and deploy wireless communication systems. It has brought great convenience to the research on MIMO technol-ogy, sped up the development progress, reduced development costs and made the real re-search environment available for most communication researchers. This paper introduces a SDR platform constructed by the open source software GNU Radio and the Universal Soft-ware Radio Peripheral (USRP). By means of programming on GNU Radio, a basic 2×1 MIMO communication system is designed and implemented, which achieves reliable com-munication in real environment. Besides, this work lays the foundation for the follow-up study of MIMO technology.In addition, the beamforming technique in multi-user MIMO systems is also studied in this paper. Beamforming is a key technique in multi-user MIMO systems to eliminate multi-user interference, and has a broad application space in user-intensive micro-cell and wireless LAN. Almost all the beamforming schemes achieve the aim of eliminating inter-user interference by means of shaping the transmit signal according to the Channel State Information (CSI). However, when the number of users is much larger than number of base station antennas in multi-user MIMO systems, user selection algorithm is essential in order to focus the limited transmit power on users with good channel state and low inter-user interference. Based on fully analysis and research on existing beamforming schemes and user selection algorithms, a typical user selection procedure is summarized, and a Long Step User Selection (LSUS) algorithm for UBF is proposed. Several simulation results are demonstrated to verify the superior perfor-mance of UBF-LSUS scheme in terms of channel capacity and convergence rate.