Research On The Multi-mode Modulation Communication System Based On Cognitive Radio

With the rapid development of wireless communication technology as well as thepopularity of smart terminal equipment, people have much higher demand for thequality of the wireless communication. However, the shortage of the spectrum resourcesand low spectrum utilization restrict the development and application of wirelesscommunication. Cognitive radio is a spectrum sharing technology, which candynamically perceive the spectrum environment, purposefully change certain operatingparameters (such as transmit power, carrier frequency, and modulation techniques, etc.)in real-time while not affecting the authorized users, then opportunistically access theidle spectrum, and finally improve the spectrum utilization.This paper mainly studies the design and implementation of the multi-modemodulation techniques in cognitive radio system based on the USRP software radioplatform. It firstly introduces the background and key technologies of cognitive radio,presents the GNU Radio and USRP’s Universal Software Radio platform, then analyzesMPSK、MQAM and OFDM digital modulation technique principles in detail, andimplements the MPSK and OFDM modulation types on the GNU Radio platform.Secondly, this paper discusses the adaptive technology of cognitive radio systems andanalyzes two SNR estimation algorithms. Finally, it presents multi-modes’ designs ofcognitive radio modulation scheme and gives the specific implementation in the GNURadio and USRP platform. The system solution can dynamically select the systemoperating frequency, modulation method, and transmission rates according to theallocated channel information and channel estimation.