开题报告 英文翻译_英文翻译及开题报告

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在现代通信系统中，如何高速和可靠地传输信息成为人们关注的一个焦点。虽然现在数据传输理论和实践已经取得了相当大的进展，但是随着通信的发展，特别是无线通信业务的增长，可以利用的频率资源日趋紧张。OFDM调制技术的出现为实现高效的抗干扰调制技术和提高频带利用率开辟了一条的新路径。正交频分复用（OFDM，Orthogonal Frequency Division Multiplexing）是当前一种非常热门的通信技术。它即可以被看作是一种调制技术，也可以被看作是一种复用技术。由于它具有抗多径衰落和频谱利用率高的特点，因此被广泛应用于高速数字通信领域，比如应用于IEEE 802.11a无线局域网（WLAN）的物理层等等。本文叙述了正交频分复用技术的产生背景、发展历史、基本原理和OFDM系统的实现方法。其中OFDM的原理部分介绍了OFDM的系统组成、调制方式、信道的分配以及使用OFDM技术的优势与不足所在，指出在短波通信中采用OFDM体制需要解决的几个关键性技术。最后总结了OFDM系统的性能特点以及在实际中的应用, 并且展望了今后的无线移动技术的发展前景。

关键词：正交频分复用；调制；解调；4G

In modern communication system, how to transmit information with high speed reliablely become a focus that people pay attention to.Though now, data transmiion theory and practice have gotten fairly big progre, but along with the development of communication, especially the increase of wirele communication busine but with a view to with frequency resource become tense day by day.The appearance of OFDM modulation technology is the modulation technology of interference rejection that realizes efficiency with raising the utilization rate of frequency band have opened up a new route.Because of wirele environment where multipath maybe significant, Orthogonal Frequency Division Multiplexing(OFDM), a special form of multicarrier modulation(MCM), where a single data stream is transmitted over a number of lower rate subcarriers has recently received considerable attention for its robustne to multipath selective fading and high bandwidth efficiency.It can be seen as either a modulation technique or a multiplexing technique.This paper has narrated orthogonality frequency to divide, use again the technical realization method that produces the system of background, development history,basic principle and OFDM.In which, the principle system of OFDM that has introduced OFDM partially forms and makes the distribution of way and channel as well as uses insufficient place and the advantage of OFDM technology, point out in some crucialne technologies that short wave solves in communication with OFDM system needs.Have summarized the performance characteristic of OFDM system as well as the application in reality finally, and have looked ahead in the future wirele move technology develop prospect.Keywords:

OFDM（Orthogonal Frequency Division Multiplexing）；Demodulation；4G Modulation；