正交频分复用技术仿真与信道估计研究

发布时间：2018-06-09 22:37

本文选题：OFDM + 信道估计　；参考：《吉林大学》2014年硕士论文

【摘要】：如今通信技术正发生着日新月异的变化，为人类社会的发展做出了巨大的贡献。然而，人们对通信质量的要求也在日益提高。因此，如何不断的提高通信系统的性能一直是众多研究者面临的课题。本论文选择通信系统中的OFDM（正交频分复用）系统，深入研究了其无线信道、基本原理和信道估计算法等技术，并基于传统的DFT信道估计算法，提出一种改进方法。改进算法可以进一步消除噪声的影响，具有很好的使用价值。 OFDM技术是一种多载波传输方案，并且具有广泛发展前景。MIMO-OFDM（多输入多输出正交频分复用）是应用于下一代蜂窝通信（3GPP-LTE，移动WiMAX，IMT-Advanced）、无线局域网（IEEE802.11a，IEEE802.11n）、无线局域网络（MB-OFDM）和广播（DAB数字音频广播，DVB数字视频广播，，DMB数字多媒体广播）的一种关键技术。信道估计技术作为正交频分复用技术的一项关键技术，在无线移动通信系统中成为一个新的研究热点。在OFDM系统中，发射机将信息比特序列调制成PSK/QAM符号，然后对相应的符号执行IFFT将其变换成时域信号，最后通过一个（无线）信道将它们发射出去。接收的信号通常因受到信道特性的影响而失真。为了恢复发送的比特信息，在接收机必须对信道的影响进行估计和补偿。本文首先介绍了无线信道建模的基本概念，并对无线信道的衰落现象进行了建模。介绍了衰落信道的分类：大尺度衰落和小尺度衰落。并分别对大尺度和小尺度衰落的各种模型分别进行了建模和仿真。然后，文章又介绍了OFDM通信系统的基本原理和OFDM信号的产生和其基本特征。分析了可以抵抗系统多径效应的机制的插入保护间隔(GI)与循环前缀(CP)技术以及具体实现插入循环前缀的方法。又分析了系统中的各项关键技术，并对各项技术建立数学模型。最后，本文介绍了被广泛应用于信道估计的两种技术：最小二乘LS和最小均方差MMSE技术。然后研究了能够提高LS或MMSE信道估计性能的基于DFT的信道估计技术。并提出一种改进的基于DFT的信道估计方法，最后对该改进算法进行仿真研究，通过仿真实验比较证明了该算法的优越性，具有很好的使用价值。
[Abstract]:Nowadays, communication technology is changing with each passing day, and has made great contribution to the development of human society. However, people's demand for communication quality is also increasing. Therefore, how to continuously improve the performance of communication systems has been a topic facing many researchers. In this paper, OFDM (orthogonal Frequency Division Multiplexing) system is selected for communication system. The wireless channel, basic principle and channel estimation algorithm are studied in detail. Based on the traditional DFT channel estimation algorithm, an improved method is proposed. The improved algorithm can further eliminate the influence of noise and has a good use value. OFDM technology is a multi-carrier transmission scheme. MIMO-OFDM (multiple input and multiple output orthogonal Frequency Division Multiplexing) is widely used in the next generation cellular communications (3GPP-LTEN, mobile WiMAXPIMT-Advanced WLAN, IEEE802.11aEIEEE802.11nPU, WLAN / MB-OFDM) and DVB DVB digital video broadcasting (DMB). A key technology of digital multimedia broadcasting. As a key technology of orthogonal frequency division multiplexing (OFDM), channel estimation has become a new research hotspot in wireless mobile communication systems. In OFDM system, the transmitter modulates the sequence of bits into PSK / QAM symbols, then performs Ifft on the corresponding symbols to transform them into time-domain signals, and then transmits them over a (wireless) channel. The received signal is usually distorted by channel characteristics. In order to recover the transmitted bit information, the channel influence must be estimated and compensated in the receiver. Firstly, the basic concept of wireless channel modeling is introduced, and the fading phenomenon of wireless channel is modeled. This paper introduces the classification of fading channels: large scale fading and small scale fading. The models of large scale fading and small scale fading are modeled and simulated respectively. Then, the paper introduces the basic principle of OFDM communication system, the generation of OFDM signal and its basic characteristics. The techniques of insertion protection interval (Gi) and cyclic prefix (CPP) which can resist the multipath effect of the system and the method of inserting cyclic prefix are analyzed. The key technologies of the system are analyzed, and the mathematical model of each technology is established. Finally, this paper introduces two techniques widely used in channel estimation: least square LS and minimum mean square error (MMSE). Then the DFT-based channel estimation technology which can improve the performance of LS or MMSE channel estimation is studied. An improved channel estimation method based on DFT is proposed. Finally, the simulation of the improved algorithm is carried out. The simulation results show that the algorithm is superior and has good practical value.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

【参考文献】