Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : BER analysis of TDD downlink multiuser MIMO systems with imperfect channel state information | Zhou et al. EURASIP Journal on Advances in Signal Processing 2011 2011 104 http content 2011 1 104 o EURASIP Journal on Advances in Signal Processing a SpringerOpen Journal RESEARCH Open Access BER analysis of TDD downlink multiuser MIMO systems with imperfect channel state information Baolong Zhou1 2 Lingge Jiang1 Shengjie Zhao2 and Chen He1 Abstract In downlink multiuser multiple-input multiple-output MU-MIMO systems the zero-forcing ZF transmission is a simple and effective technique for separating users and data streams of each user at the transmitter side but its performance depends greatly on the accuracy of the available channel state information CSI at the transmitter side. In time division duplex TDD systems the base station estimates CSI based on uplink pilots and then uses it through channel reciprocity to generate the precoding matrix in the downlink transmission. Because of the constraints of the TDD frame structure and the uplink pilot overhead there inevitably exists CSI delay and channel estimation error between CSI estimation and downlink transmission channel which degrades system performance significantly. In this article by characterizing CSI inaccuracies caused by CSI delay and channel estimation error we develop a novel bit error rate BER expression for M-QAM signal in TDD downlink MU-MIMO systems. We find that channel estimation error causes array gain loss while CSI delay causes diversity gain loss. Moreover CSI delay causes more performance degradation than channel estimation error at high signal-to-noise ratio for time varying channel. Our research is especially valuable for the design of the adaptive modulation and coding scheme as well as the optimization of MU-MIMO systems. Numerical simulations show accurate agreement with the proposed analytical expressions. Keywords BER channel estimation error delay MU-MIMO TDD zero forcing 1. Introduction Owing to their high spectral efficiency multiple-input multiple-output
