节点文献
MIMO-OFDM系统峰均比抑制问题研究及算法实现
Research and Algorithm Realization of PAPR Restrain in MIMO-OFDM Systems
【作者】 王克融；
【导师】 黎锁平；
【作者基本信息】 兰州理工大学 ， 信号与信息处理， 2010， 硕士
【摘要】 多输入多输出正交频分复用(MIMO-OFDM)系统由于能够提高系统容量和效率并能抵抗多径衰落,频谱利用率高,成为新一代高速宽带无线通信系统的关键技术之一,并得到人们越来越多的关注。在MIMO-OFDM系统中,由于利用IFFT变换将发送符号序列进行了OFDM调制,从而使MIMO-OFDM系统也具有峰均功率比(PAPR)过高的问题,从而严重影响MIMO-OFDM系统的性能。现有的MIMO-OFDM系统中的峰均比算法大多是将OFDM系统中的峰均比算法直接应用到各个天线上,并没有考虑MIMO-OFDM系统本身的固有特性,这样不仅计算量大而且增加了边带信息传输量,降低了有效数据的传输效率。本文从MIMO-OFDM系统本身的固有特性出发,综合分析了MIMO-OFDM系统的峰均比抑制问题,通过借鉴目前已有的峰均比抑制方案,在证明和分析了经过正交空时编码的信号与其共轭信号具有相同的峰均功率比以及采用正交空时编码结构的发送信号在前后符号周期之间具有共轭对称性的基础上,提出了低复杂度的MIMO-OFDM系统中的选择性映射算法,并用Matlab软件对算法性能进行了仿真验证。仿真结果表明,本文提出的算法性能明显优于现有算法,不仅能显著降低算法复杂度,减少迭代运算量,同时还对峰均比抑制效果有较小的改善,从而提高了系统的性能。另外,针对空频编码MIMO-OFDM系统,将STBC MIMO-OFDM中的跨天线排序算法的原理应用到空频编码MIMO-OFDM系统中,提出了空频编码MIMO-OFDM系统中的子载波排序最优算法及其次优算法。仿真结果表明这两种算法均比原始信号具有更好的峰均比特性。
【Abstract】 Multi-input Multi-output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) can increase the system capacity and efficiency, resists the multi-path fading, has high use ratio of frequency spectrum at the same. So it is regarded as a key technology of the fourth generation mobile communication system, and it gets more and more attention.However, MIMO-OFDM system have the shortcoming of high peak to average power ration (PAPR) because the IFFT transform in modulation of the sending symbol sequence, this disadvantage affect the performance of MIMO-OFDM systems seriously. The existing MIMO-OFDM system PAPR algorithm is mostly apply the PAPR algorithm of OFDM system to each antenna directly without taking into account of the character of the MIMO-OFDM system, so that algorithm not only need large quantity of calculation but also increase the amount of sideband information transmission reducing transmission efficiency.In this paper, on the base of the character of MIMO-OFDM system we mostly analyze the PAPR restrain algorithms of MIMO-OFDM system. Then the proof and analysis of the signal that through the orthogonal space-time coding has the same PAPR with its conjugate signal, and the orthogonal space-time code structure has the character of conjugate and symmetry is given firstly. Based on that and a Low-complexity PAPR reduction algorithm for MIMO-OFDM system is proposed. The simulation result shows that this algorithm is better than the present algorithm, it not only reduce computational complexity significantly and reduce the amount of iteration computation but also improved PAPR reduction effect slightly at the same time. So this algorithm can improve performance of the system. In addition, aiming at the SFBC MIMO-OFDM system, we apply the principle of cross-antenna rotation and inversion algorithm in STBC MIMO-OFDM to the SFBC MIMO-OFDM system, propose the sub-carrier rotation optimal and suboptimal algorithm in SFBC MIMO-OFDM system. The simulation result shows that algorithm have better PAPR than original signal.