A Research On Spectrum Sensing Of Cognitive Radio

Cognitive radio, as an emerging technology in the field of wireless communication, is a strong technological support for solving the shortage of spectrum, realizing dynamic management of spectrum and enhancing the use of spectrum. Spectrum sensing is one of the key technologies of cognitive radio. This paper deals with the realization of spectrum sensing technology targeted at both single user and multi-user, and investigates the realization of spectrum sensing technology under OFDM and UWB, the two major transmission schemes adopted in cognitive radio.As to the realization of the technology targeted at single user, the author taps into the algorithms of energy detection, matched filtering detection, cyclostationary feature detection, analyzes the performance of the algorithms through computer simulation, and conducts quantitative analysis on the effect of factors, including noise uncertainty, frequency offset, and sampling clock offset, on the above three algorithm. As to the realization of the technology targeted at multi-user, the author focuses on cooperative detection algorithm, and analyzes the performance of the algorithms through computer simulation under the AND and OR fusion rules. The application backgroud of two fusion rules is presented.In the research of spectrum sensing problem of cognitive radio based on OFDM, the paper breifly introduces the basic priciple of OFDM, derives the OFDM signal model based on IFFT/FFT, analyzes the technical advantages of OFDM applied to cognitive radio, and dwells on the spectrum sensing problems based on the various prior knowledge of primary user's signals. In the condition that the signal model and operating frequecy of the primary user are known, the paper respectively builds the tonal signal model and AR stochastic process, and designes the single carrier individual detection algorithm based on LMP test. The performance of the algorithms is analyzed with central limit theorem and verified through computer simulation. In the condition that only the operating frequecy of the primary user is known, the paper designes the multi-carrier joint detection algorithm based on energy detection through building the optimization model between the communicaion capacity and interference. The nonconvex optimization problem included in the algorithm is converted to the convex optimization problem through utilizing the forced constrainted condition according with the practical application. And the performance of the algorithm is verified through computer simulation.In the research of spectrum sensing problem of cognitive UWB radio, the paper briefly introduces the UWB, MB-OFDM and WiMax, analyzes the feasibilty of combination between UWB and cognitive radio, the coexistence problem between CUWB and WiMax, the signal detection of the WiMax uplink and downlink, and closed form expression of detection performance. The estimator-correlator is reduced to the energy detector for practical application and its performance is analyzed based on the computing results of the power of WiMax uplink. The performance results indicate that the MB-OFDM receiver based on energy detector will enable robust detection of the WiMax uplink signal.At last, it summarizes the whole paper and outlines the work for further study.