摘要
在移动信道环境中可靠、高速的传输数据是移动通信技术发展的目标和要求，并且第四代移动通信系统要求能够以最低的代价(带宽、功率、复杂性)来为各种用户提供高质量的宽带业务，这就需要有适于移动信道的传输技术来支持。由于移动信道的多种不确定因素，正交频分复用(OFDM)技术成为适应这种信道环境的传输技术之一。OFDM是一种特殊的多载波传输方式，它使用一系列低速子载波并行传输数据，使得它具有抗多径干扰的能力、能以很高的频谱利用率实现高速数据传输等。
本文从对移动信道的特性研究出发，分析了其存在的问题，例如多径干扰、多普勒频移，然后针对这些问题提出了解决方案——采用OFDM技术作为核心技术来设计移动通信系统。文中给出了具体的设计方法，对所设计的系统进行了仿真分析，并综合性能和成本的考虑，提出了适合于本文所讨论的移动通信系统的设计方案。以下是本文所作主要工作：
通过分析移动信道的特性建立了移动通信系统信道模型；
OFDM技术与传统的并行传输技术相比，具有很大的优势，结合建立的移动信道模型，将此技术应用在移动通信系统之中；
在对OFDM技术基本原理进行分析的基础上，对OFDM移动通信系统进行建模与仿真分析：
最后，给出了详细的OFDM移动通信系统发射机和接收机的原理框图，提出了一套基于DSP&FPGA的OFDM移动通信系统硬件平台设计方案。
Data transmission in mobile channel with high speed and reliability is required in future mobile communication system. The 4th mobile communication system is expected to provide high-quality broadband services using the minimum possible resources (power, bandwidth, complexity). Toward this end, an appropriate transmission technique that matches the mobile channel characteristics is required. Taking many uncertain factors in mobile communication channel into account, OFDM (orthogonal frequency-division multiplexing) is one of the promising techniques that meet such requirements with reasonable complexity. OFDM is one of multi-carrier digital modulation techniques, in which a single high data rate data stream is transmitted using a number of lower data rate sub carriers, it has many properties, such as robustness to multi-path fading, high data rate transmission capability with high bandwidth efficiency, and so on.
Base on the study of mobile communication channel characteristics, this thesis gives an analysis on the existing problems, such as multi-path fading and Doppler frequency shift, and proposes a solution: Implanting the OFDM technique in modulator. In this thesis, detailed design architecture is given, together with a simulation analysis of the OFDM mobile communication system. With consider of cost and performance, the thesis gives a design project of OFDM mobile communication system. The thesis makes and works as follows:
At first, established the mobile channel model, through the analysis of the mobile channel characteristics;
The second, proved the advantage of OFDM througth comparing several parallel technologies, and implanting the OFDM technique in the mobile communication system modulator;
Then, this thesis gived the baseband transmission architecture of OFDM mobile communication system and established the model of OFDM mobile communication system.
At last, the thesis gives a brief introduction of the design of the hardware platform for the wireless communication system as well as the data transmission flaw.
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