Research Of OFDM Signal Spectrum Sensing And Hardware Implementation

Wireless communication technology is developing very rapidly in recent years,so the spectrum congestion phenomenon is caused, on the other hand, licedsed spectrum utilization is very low, the contradiction between the traditional fixed spectrum allocation mechanism and the actual needs of spectrum is increasingly significant. The concept of cognitive radio is proposed in such situation, Cognitive radio technology is an effictive way to solve the current spectrum resour ce constraints, its core idea is to use idle spectrum, at the same time monitor the spectrum, if any authorized users want to use the spectrum, the cognitive user must quit quickly, so the efficiency of utilization of spectrum is improved, spectrum sensing technology is the key techno logy to achieve this goal. At present the traditional spectrum sensing algorithms in common are: energy detection, matched filter detection, cyclostationary characteristic detection etc.Orthogonal frequency divition multiplexing(OFDM) technology is being used increasingly in many occasions, such as digital TV, audio broadcasting, wireless and broadband networks, OFDM technology will be key technology of future broadbnad wireless communication system, Therefore, spectrum sensing based OFDM system is very necessary.CPCC(Cyclic Prefix Correlation Coefficient) is selsected in this paper, which is a correlation detection method based on Cyclic Prefix,CPCC algorithm use the correlation principle of Cyclic Prefix of OFDM signal to detect signal. On condition of single path channel, estimate of the value of the correlation coefficient can be devirated from the estimated covariance matrix of received signal. If the false alarm probability is 0.05, the relationship between detection probability and SNR is simulated in matlab, then complete the design and hardware inplementation of CPCC algorithm in FPGA, mainly design all the modules with verilog HDL in the Quartus II development platform, and simulate each module using Modelsim simulation software, finally, download the program to the FPGA development board and run it, Use the Signal Tap II of Quartus II to get real-time signal data, the hardware implementation of CPCC algorithm have been finished, Modules designed in Quartus II includes: ROM module, multiplier module, control module, an adding module and a detection module. the baseband signal in this paper is generated by matlab, several test were done under different SNR, and the results consistent with the theoretical results.Through the analysis of CPCC algorithm, we can get in the noise-only case the correlation is small, but in the case the frequency if being used, the correlation is very large, CPCC algorithm is a simple and computationally efficient OFDM signal spectrum sensing method.