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摘 要
高速数据通信业务的不断发展使得现有的无线频谱资源非常的紧张，OFDM具有高传输速率和能有效对抗多径衰落的优点，而NC-OFDM系统既继承了OFDM系统的优点，同时又具有较强的灵活性，所以在认知无线电中得到了很广泛的应用。
本文首先对NC-OFDM和OFDM的原理、优势及其面临的巨大挑战进行了系统的介绍，由于NC-OFDM系统的处理技术是以快速傅里叶变化为基础的，所以在传输信号的过程中会有较大的旁瓣泄露，对相邻的用户产生比较大的干扰，这个问题亟待我们解决,于是在前人研究的基础之上，本文着重探讨了利用子载波加权（Sub carrier Weighting,SW）的方法来解决NC-OFDM系统中旁瓣抑制问题，子载波加权的原理是将输入的数据符号乘以一个加权系数得到输出数据符号，从而达到降低旁瓣的目的。我们通过理论研究和MATLAB的仿真，来验证子载波加权的方法能够有效的抑制NC-OFDM的旁瓣泄露，具有重大的意义。
关键字：认知无线电；非连续正交频分复用；旁瓣抑制；子载波加权
ABSTRACT
With the development of high speed data communication service, So, it is important to look for new technology to improve the utilization of spectrum resources. OFDM is good at its fast transmission rate and anti-multipath fading ability.
First of all, the paper makes a comprehensive introduction about the principle. the advantages and the huge challenges of the OFDM and NC-OFDM. While NC-OFDM inherits the advantages and the strong flexibility of OFDM system, so it is widely used in cognitive radio. However, the NC-OFDM system is based on FFT(Fast Fourier Transform) processing technology, so there is a rather huge leakage when the signals are transmitted. And also, they will bring great interference to neighboring users. The problem is urgent for us to solve. Then on the basis of previous studies, it focuses on the method of sub carriers weighting(SW) to solve the problem of side lobe suppression in NC-OFDM system. The principle of sub carrier weighting is to multiply the input data symbols by a weighted coefficient to get the output data symbols, so as to achieve the purpose of reducing the side lobe. It is of great significance to verify that the method of sub carriers weighting(SW) can effectively inhibit the NC-OFDM side lobe leakage through theoretical study and MATLAB simulation.
Key words:Cognitive Radio; Non-continuous Orthogonal Frequency Division
Multiplexing; Side lobe Suppression; Sub carriers Weighting
目 录
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