滤波多音（FMT）调制系统无线仿真平台及关键技术研究

【作者】 王秋瑾；

【导师】 高振明；

【作者基本信息】 山东大学 ， 通信与信息系统， 2005， 硕士

【摘要】 社会进步与全面信息化对通信提出了越来越高的要求,单纯的语音服务已经不能满足人们需要,能够通过无线网络随时随地获得多媒体业务的接入成为人们对通信技术的要求,而电子技术、多媒体技术、移动通信技术的发展使其成为可能。目前,在第三代移动通信系统(3G)走向商用化的情况下,下一代移动通信系统正成为研究的热点,其数据传输速率可以达到10Mbps至100Mbps,能有效地对抗多径衰落,具有非常高的频带利用率。 多载波传输技术能够在保持较高信息传输速率的同时,有效地克服多径传播造成的符号间干扰(ISI)。正交频分复用(OFDM)作为一种多载波调制技术,成为下一代通信研究中的一个热点。其凭借信号本身的特点能够高速传输数据信息,有效地对抗多径衰落:但是它也存在许多需要解决的关键问题,如容易受频率偏移和相位噪声影响,有较大的峰值平均功率比(PAPR)等。这些问题都制约着OFDM在无线信道中的应用,现在人们对OFDM所进行的研究也主要集中在这些领域。 滤波多音调制(FMT)相对于OFDM是一种新兴的多载波技术。该技术的主要特点是通过滤波器组滤波使得各子载波具有很高的频谱约束性,从而对系统频率偏差不敏感。FMT克服了OFDM易受频率偏差影响的缺点,但也由滤波器组在系统中引入了ISI。因此,FMT中需要引入子信道均衡技术来消除滤波器组的影响。 本论文首先介绍了两种多载波传输技术——OFDM和FMT的基本原理和系统有效实现结构,对两种技术的子信道划分方式、系统实现结构、复杂度以及频谱利用率和抗干扰性能进行比较。然后对FMT的几种关键技术,主要是滤波器组设计、均衡器设计问题进行研究,寻找适合FMT系统的高性能滤波器组和简单有效的均衡方案。在此基础上,建立FMT系统无线通信仿真平台。通过该平台进行实验,得到FMT系统在频偏和多径信道下的性能仿真结果,表明FMT在抵抗频偏方面比OFDM具有优势,而且适合室内及近距离进行无线传输。 由于FMT宽带信号的各个子载波有着相对独立的信道衰落,使之能够根据各个子信道的实际衰落情况灵活选择调制方式,分配发送功率和比特,即自适应更多还原

【Abstract】 With the progress of the world, people need high quality and transmission rate of communications, and simple voice service can’t meet the requirement It is possible to get multimedia service with wireless network at anytime and any places, for that electronic, multimedia and mobile communication has developed rapidly. Up to now, 3G has been launched into business in many countries, and researches are focus on the next generation communication system, called 4G, which is characteristic of the good resistance to multipath decay and high efficiency of frequency. The data rate of 4G is ranging from 10Mbps to 100Mbps.Multicarrier technique provides high data rate and efficiently avoiding intersymbol inference (ISI) arosing by multipath propagation. As one of the multicarrier techniques, OFDM has many advantages, such as high data rate and resisting multipath decay, and it has become a hot field in the researches of 4G. On the other hand, there are many problems of OFDM, for example: high sensitivity to frequency offset and great peak to average power ratio (PAPR), etc. All these issues restrict the applications of OFDM in wireless environments to some extent, so lots of researchers pay attention to them.Comparing to OFDM, a new multicarrier technique FMT is characteristic of the significantly lower spectral overlapping between adjacent subchannels. FMT overcomes the weakness of being sensitive to frequency offset in OFDM, but the using of filter banks bring ISI to the system. For this reason, equalizer is necessary in FMT system to eliminate the interference from filter banks.In this thesis, after introducing the basic theory and structure of OFDM and FMT, we compare these two different multicarrier techniques with the way separating subchannels, structure of the system, complexity, efficiency of frequency and performance to interfere, including ISI and ICI. Several key parts in FMT system are discussed, such as the design of filter banks and equalizers. By setting up a simulation platform of FMT system, we get the performance in wireless different environments with frequency offset or multipath interference. The results of simulation indicate that FMT show better performance than OFDM through decaying channels with frequency offset; FMT is a feasible wireless solution in indoor environments or with shortdistance propagation.The independency of decay in different subchannels makes it possible that taking different modulation schemes, loading different transmission power and bits in subchannels according to the real character of them. This loading scheme is called adaptive modulation technique. In chapter 5, many adaptive loading algorithms are discussed, which has been proposed to take into application before. Based on equal power adaptive bit loading algorithm, we put forward an easy, efficient algorithm, called SDR-based adaptive bit loading algorithm. Results of simulation indicate that this algorithm enhances the resistance ability to decay of FMT system, and keeps data rate highly and reliability.We discussed some key issues in this thesis, and only a part of simulation results are showed. Some issues in the FMT system are not discussed, such as time and frequency synchronization, channel estimation and channel coding, which will be researched in the following work.更多还原