（毕业设计论文）《TDD_MIMO信道非互易性补偿算法研究》.doc

TDD MIMO信道非互易性补偿算法研究 摘 要 为实现高速无线数据传输，MIMO技术作为一种有效的手段得到了广泛的研究，并被新一代无线通信系统所采用。基于时分双工（TDD）技术的MIMO系统可以利用上下行信道的互易性，使得基站能够直接基于检测到的上行信道状态信息制定下行发射预处理策略，而不需要额外的反馈开销。但是信道估计不准确及射频器件的非理想特性将导致信道互易性的丧失，使TDD系统的优势无法发挥。 本文分析了信道估计不准确及I/Q不平衡对TDD-MIMO信道互易性的影响，在此基础上提出了一种基于时域截短的信道估计算法及对IQ不平衡的补偿算法，并在两发两收的TDD-MIMO系统中进行了仿真分析。本文主要内容如下： 研究了TDD-MIMO系统中的多种信道估计方法，分析了由于信道估计误差造成的TDD-MIMO系统容量损失，并提出一种基于时域截短的信道估计方法，仿真结果表明，该方法具有复杂度低及显著性改善性能的优点； 建立了仅接收端存在I/Q不平衡时MIMO系统等效信道模型，通过容量分析和仿真研究了I/Q不平衡带来的TDD-MIMO信道互易性损失，并通过信道估计对仅接收端存在I/Q不平衡的情况进行补偿，能够有效地补偿I/Q不平衡造成的信道互易性损失； 推导了收、发端都存在I/Q不平衡时MIMO系统等效信道模型，通过容量分析和仿真，表明I/Q不平衡会带来明显的TDD-MIMO信道互易性损失，分别对已知I/Q不平衡参数及未知参数两种情况下造成的TDD-MIMO信道互易性损失出补偿方法，仿真结果表明，这些算法能够有效地补偿信道互易性损失，显著地改善了系统误码率和容量性能。 关键词：信道估计 时域截断插值 I/Q不平衡 信道互易性 补偿算法 Abstract As an effective way to achieve high data rates, MIMO technique has been widely studied and employed in new-generation of wireless communications systems. By using channel reciprocity in time division duplex(TDD) MIMO systems, base station(BS) can make transmit strategies according to the channel state information (CSI) through reverse link channel estimation. But channel estimation errors and radio frequency(RF) front-end imperfections will destroy channel reciprocity. This thesis analyzes the impact of channel estimation errors and I/Q imbalance on channel reciprocity in TDD-MIMO systems. In the thesis, channel estimation method based on time domain truncation and I/Q imbalance compensation algorithms are proposed, and have simulated in a 2×2 TDD-MIMO system. The main contributions are as follows: Several conventional channel estimation methods for MIMO-OFDM systems are studied and discussed, and the lose of channel reciprocity capacity with imprecise channel estimation is analyzed, a new channel estimation method based on time domain truncation is proposed. Simulation results show that the method can improve the performance with low complexity. The equivalent model of MIMO systems with I/Q imbalance in receiver is derived, the lose of c