Simulation Research On Cognitive Radio Frequency Hopping Communication System Performance

As one of the spread spectrum technologies,due to its good performance on anti-interference,resistance to intercept and information transmission security between users,frequency hopping communication has been widely used in military and civilian applications.But with the continuous development in jamming technology,the anti-jamming capability of wireless communication equipment is also improved.Moreover,due to the limited spectrum of wireless communication,the allocation of spectrum resources has become increasingly intense.On the other hand,some spectrum bands that have been allocated are very low efficient,as a reault of which if we use the cognitive radio technology to perceive the channel environment,we can increase the specturm efficiency.Based on Matlab software,we implement the simulation system of cognitive frequency hopping communications and investigate the influence exerted by several interference signals in the Rayleigh fading channel in this thesis.Firstly,the thesis introduces the important parameters,system configuration and mathematical model of the conventional frequency hopping communication system,as well as the analysis of its anti-jamming performance in jamming channel..Secondly,the thesis compares the detection performance of different spectrum sensing methods through the simulation.The simulation results show that,with the increase of the channel signal-to-noise ratio(SNR)in the AWGN channel,the detection capability of the sensor is enhanced.Further we compare the perceptive ability of single user in AWGN and Rayleigh fading channel.The simulation results show that the detection performance of AWGN channel is better.In addition,compared with the single user perception,multi-user collaborative perception can get more information of channel environment and therefore behaves better.But in the actual communication environment,signals received by different nodes may experience different path loss and multipath fading.Through the simulation,the thesis compares the performance of three kinds of commonly used hard decisions as well the SNR-based weighted cooperative spectrum sensing(WCSS).The simulation results show that the detection performance of soft fusion is better than that of the hard fusion,in which the MRC guideline is superior to the EGC guideline,and the WCSS guideline is superior to the other three hard fusion strategies.Finally,the thesis implements the system simulation model under Rayleigh fading channel by sending the random data stream and adding different jamming signals.The bit error rate(BER)performances of the conventional FH system,single user sprectrum sensing cognitive FH system and multi-user cooperative sprectrum sensing cognitive FH system are simulatied,and the effect of spectrum sensing time interval on the anti-interference performance of cognitive hopping system is simulated,too.The simulation results show that compared with the conventional FH system,the anti-jamming capability of CFH system is improved obviously.In addition,CFH system based on MRC guideline possesses the lowest error rate and the best anti-jamming performance.And when the spectral perception time interval increases,the sensitivity of the communication system to the change of the channel environment is reduced,and the anti-interference performance of the cognitive hopping system is weakened.