Research On Coexistence Of DSSS Cognitive Users And Narrow Band Authorized Users

For increasingly complex of wireless communications environment and limited ofspectrum resources, it’s needed to improve the spectrum utilization. Relies on national and theHeilongjiang province Natural Sciences Fund Project, combined spread spectrumcommunication technology and the cognitive radio technology advantages, through onselecting composite sequence and simulating different pseudo random sequence, choose m-Wcomposite sequence for system expansion frequency sequence. Through CS-CSK technology,established SS-CS-CSK cognitive radio communications system. On system error rate,composite sequence correlation, displacement capacity upgrade itemized analysis andverification. Under the condition of low bit error rate, system achieving the coexistence ofcognitive users and authorized users, increasing the system capacity and improve spectrumutilization and system efficiency. For this research is primarily carried out the following work:(1)In AWGN channel conditions, discuss the three typical sequences of pseudo randomcode，m series，Gold series, and Walsh sequences in Direct Sequence Spread Spectrum (DSSS)communication system respectively. Simulate and validate their spectral characteristics andcorrelation.(2)Based on cognitive radio concept, make the necessary theory of controllabilityanalysis and simulation verification about composite sequences m-W and G-W in DSSSsystem. The m-W sequence is the system sequence. Analyze and validate changing the cycleof m series and Walsh sequences rates can change the frequency spectrum characteristics ofstructural, which can be achieved in determining the location of narrowband authorizes users.For evade the authorized users, the system appropriate adjustments to the m and Walshsequences.(3)Build a CS-CSK model by using CSK technology when system bandwidthconstrained and spread spectrum sequence of cycles under limited circumstances. Bychanging the phases of m-W composite sequence enhance the system capacity. Simulate andanalyze cross-correlation properties, power spectrum and anti-noise performance about m-Wcomposite sequence code after CSK, and compare with traditional DSSS communicationsystems in capacity. (4)Build a SS-CS-CSK cognitive radio communication system. Analyze the spreadspectrum gain efficiency, the ability of anti-noise, efficiency of information transfer and load.Simulate and analyze system error rate, the coexistence cognitive users with narrowbandauthorizes under Gaussian channel.