基于IEEE802.16d的MIMO-OFDM传输系统的部分算法研究与模块实现

【作者】 赵珂；

【导师】 张朝阳； 陈文正；

【作者基本信息】 浙江大学 ， 通信与信息系统， 2005， 硕士

【摘要】 无线通信的迅速发展给人类的生活带来了极大的便利，实现“任何时间、任何地点以任何方式进行信息交流”，同时也带来了对容量与质量等方面更高的需求。MIMO和OFDM的出现为系统容量和频谱利用率带来了福音。OFDM的可用信道粒度小，对付频率选择性保护衰落能力强，可以通过动态改变调制参数的方法提高频谱效率，逼近Nyquist速率。在此基础上应用MIMO有两个方向，一是依靠发送和接收分集，利用多径效应，为接收机提供多个衰落特性的信号的复本，改善在衰落无线通信环境中传输的误码性能；或创造多个并行空间信道独立地传输信息，在不增加带宽的情况下成倍地提高通信系统的容量。 本文主要研究MIMO-OFDM系统的原理和在宽带无线接入方案—城域网中的应用，因此首先介绍了WMAN的协议IEEE 802.16d，并对适用的信道模型—SUI模型进行了讨论，给出了信道的仿真方法，各参数的意义和选择。 其次，通过分析MIMO-OFDM的理论频谱效率，得出理论频谱效率与天线相关系数以及功率分配方式有关，可以根据天线相关系数来选择分集或复用方式获得不同的频谱效率。然后给出了简化功率分配方式下BLAST-OFDM的频谱效率，结果和最优功率分配方式相差无几。 然后，本文根据MIMO-OFDM的系统模型，讨论了前导字的设计准则和几种实现结构帧同步、粗符号同步的表现，并对802.16d协议的前导字结构进行了解释。同时针对分集的Alamouti-OFDM，以及复用的BLAST-OFDM，讨论并仿真了它们的编码和检测方式，给出适合实现的方法。 最后对Alamouti-OFDM，提出简化的实现空时、空频编码结构，即一根天线的发送数据经过排序和共轭变换得到另一根天线的发送数据，节省了一个IFFT模块的运算量。更多还原

【Abstract】 The fast development of wireless communication technology brings about great facility to people around the world. For it’s convenient to communicate with others anytime, anywhere, by any means. Meanwhile, it raises even larger demand on capacity and quality of communication systems. Then MIMO-OFDM technology comes with hope on increasing capacity and spectrum efficiency. OFDM has a fine channel granularity, and robustness to frequency-selective fading, which is quite competitive to optimize the spectrum efficiency tight to the Nyquist rate[7], by changing its modulation scheme adaptively. Moreover, if combined with MIMO, diversity or spatial multiplexing can be achieved. With transmit or receive diversity, duplicate fadings of transmitted signals are created between multiple antennas, thus mitigating error rate by Maximum Ratio Combing. Alternatively, different signals are sent to parallel spatial channels formed by multiple antennas to explore system capacity, without additional bandwidth[13]. To sum up, MIMO-OFDM is really promising in beyond 3G technique family.This paper focuses on architecture and application of MIMO-OFDM in broadband wireless communication systems, and the rest of it is organized as follows:First, it presents an IEEE 802.16d WirelessMAN system. After that, SUI channel modeling and corresponding parameters are discussed in detail.Then ideal and actual spectrum efficiency of MIMO-OFDM system is analyzed. It shows that the spectrum efficiency is related to correlation factor of antennas and power allocation schemes. The correlation factor is a key reference of coordinating between diversity and spatial multiplex. As an example, spectrum efficiency of ZF-VBLAST system with simplified transmit power allocation schemes is analyzed and simulated, which is comparable with optimal scheme.Next referring to a MIMO-OFDM system, the design criteria of preambles are derived. After that different patterns of preambles are discussed and simulated. Then, detect and channel estimation of an Alamouti-OFDM sytem and a BLAST-OFDM system are simulated and analyzed in both system performance and feasibility.Finally this thesis gives a simplified Alamouti-OFDM coding architect for implementation, by cutting down an IFFT module, which is really resource consuming in the whole system.更多还原