Research And Implementation Of OFDM System On Software Radio Platform With GNU Radio

With the rapid development of wireless communication technology, frequencyspectrum resource is becoming more and more rare, therefore, how to make full use ofspectrum resources becomes a hot issue. Cognitive radio technology is the solution ofthis problem, and a new method of orthogonal Frequency Division Multiplexing(OFDM) technology is a kind of more mature wireless transmission technology. It has asuperior performance of the higher bandwidth efficiency and provides a considerablesolution for multipath fading, so, if we can combine the two kinds of technology, thewireless channel resources will be used more efficiently. For the OFDM technologyitself, how to adaptively choose a modulation mode and power allocation for a systemaccording to the channel condition now becomes the key to the problem.The article considers the OFDM modulation technology that is a part of thecognitive radio system. First of all, the current situation of mobile communicationtechnology and the principle of OFDM are presented in the paper, the key technologiesof OFDM system, protection interval and cyclic prefix of it are also introduced. Thenwe briefly introduce the hardware platform and SNR estimation technique, which basedon the GNU Radio and USRP software Radio platform, we have completed the adaptiveselection to which modulations for OFDM systems, the receiving terminal has done amore accurate SNR estimation algorithm. With the achievement of modulation anddemodulation, the OFDM system becomes a system that the frequency can be changedand the bandwidth can be controlled, at last the overall performance was tested, and theresult is good.