Design And Implementation Of Cognitive Radio

Currently, there is a serious spectrum usage imbalances, on the one hand, theexisting fixed spectrum allocation scheme has basically been completed to allocatethe available spectrum, but in today’s society, people’s demand for increasingcommunication, but not much spectrum can be used; another, the spectrum is notallocated to the communication has been occupied, only some of the spectrum isused or substantially at a specific time, resulting in a waste of spectrum. Therefore,we need a more flexible spectrum usage scenarios.Cognitive radio is made, so that people see the kind of dynamic spectrumaccess method, the assigned spectrum, not only has communication licensesauthorized users can use when idle spectrum, unlicensed cognitive users can alsouse this spectrum. For cognitive user first needs to access frequency band isdetected, to determine whether the presence of an authorized user to determine theaccess frequency spectrum of the idle, i.e., the first step towards the need fordynamic spectrum access spectrum sensing a communication environment.On this basis, the need to support flexible cognitive radio transmissionscheme of the physical realization of dynamic spectrum access holes. In the fieldof wireless communications, OFDM technology for its outstanding advantageshave been adopted multiple criteria. Flexible configuration of OFDM subcarriers isalso an ideal characteristic of the physical cognitive radio transmission scheme, thespectrum sensing based on the OFDM sub-carriers by closing the open cavity ofthe transmitted signal spectrum to achieve a dynamic spectrum access procedure.As the theoretical research, domestic and foreign research institutions anduniversities have begun to develop cognitive radio platform validation. Since pureprocessing speed wireless software platform developed to meet the requirements ofhigh-speed, long development cycles pure hardware platform, poor scalabilitycharacteristics, at present, most of the software development methods are used inradio way through low-cost terminal equipment, and complete the sampling signaldown-conversion feature, the baseband signal into a digital signal, the computersoftware is responsible for the signal processing part of the way quick verificationalgorithm has been widely adopted by members of university research.Based on the above considerations, the paper-based Universal Software RadioPeripheral (USRP), designed to achieve a cognitive OFDM system, which aims toachieve a complete design of dynamic spectrum access physical transmissionscheme, and in a real radio channel, the system is tested validation stu dy of cognitive radio dynamic spectrum access can be achieved and performance issues,signal baseband of the system on the computer is complete, use IT++library,using C++language is written, sampling and down-conversion by the USRPachieved using USRP hardware drivers (UHD) library function to write the controlsystem to send and receive mechanism, modular, verifiable, scalability and so on..