Reasearch On Key Technologies Of Transform Domain Communication Systems

The electromagnetic environment is increasingly complex due to the rapid development of wireless communication technology.Moreover,given the limitations of the frequency spectrum,it becomes obvious that the current frequency resource become more and more precious.How to improve the spectrum utilization rate has always been the research focus in the wireless communication area.A multiple access technology with dynamic spectrum access features called transform domain communication system(TDCS)has been proposed to address the above problem.It has unique advantages in anti-jamming communication and spectrum sharing communications.This thesis are mainly fouce on the anti-interference performance and spectrum utilization of TDCS in the complex electromagnetic environment.As a low probability of intercept(LPI)and anti-jamming technology,the performance of TDCS is highly related to the spectrum estimation and pseudo-random(PR)sequences design.This theise first introduces the basic principles of orthogonal frequency division multiplexing(OFDM)based TDCS,then discuss the key technologies of TDCS,including spectrum sensing,modulation and phase mapping.The results shows that traditional OFDM architecture based TDCS has shortcomings in multiple access performance and anti-jamming suppress of Chirp interference.To address the problem of poor performance of TDCS multiple access and improve the system capacity,a structure based on clustering is proposed in this theise.In clustering TDCS,TDCS first divides the entire spectrum band into spectrum bins,then theose spectrum bins will be divided into different groups(cluster).In addtion,each cluster will be assigned with different users,and interference cancellation and sequence design are applied for each cluster to improve its performance.The simulation shows that the proposed method can greatly improve the system capacity.Software Defined Radio(SDR)is increasingly used as a prototyping tool in industrial or academic fields,which is also a ideal prototype implementation platform for TDCS systems.A practical testbed design for TDCS based spectrum sharing system with over two National Instruments PXIe devices and six USRP RIO devices is presented in this theise.Details of system design as well as main implementation technologies are described.System performance is also validated through both theoretical analysis and simulation results under realistic channel conditions.