Design And Implementation Of Sefdm Communication System Based On Sparse Code Division Multiple Access

With the development of the times,people are increasingly relying on wireless communication technology,which also promotes the development of wireless communication technology.In particular,communication systems require higher transmission rates,access to more users,and reduced time to user access to the system.In order to fulfill these requirements,it is not only necessary to make the communication system use a more efficient transmission system,but also needs to use a wider bandwidth and occupy more resources.At present,spectrum resources have reached a point of extreme shortage.Only by making spectrum resources more efficient,communication systems can meet the increasing demands of users.The SEFDM communication system based on sparse code division multiple access combines the advantages of sparse code division multiple access to accommodate multiple users,SEFDM transmission speed and high spectrum utilization,which can meet the needs of current wireless communication development.This paper focuses on the SEFDM communication system based on sparse code division multiple access,focusing on its low-complexity and high-reliability demodulation algorithm,and implementing it with software-defined radios.First of all,this paper analyzes the background of the topic,clarifies the current technical needs,and finds the significance of conducting research.By establishing a transmission system that meets the requirements of mass user access,high transmission speed and high spectral efficiency in the development of wireless communication systems,this paper proposes a SEFDM communication system design scheme based on sparse code division multiple access.Secondly,the SEFDM communication system based on sparse code division multiple access is modeled and divided into two parts: transmitter and traditional receiver.The transmitter part mathematically models the high-order modulation process and subcarrier mapping process of sparse code division multiple access,and the transmitter part also mathematically describes the process of SEFDM modulation.The receiver section uses a classic cascaded demodulation scheme.The typical demodulation algorithm of the multiple access transmission scheme used by the receiver is modeled and simulated.The actual simulation diagram is given and the simulation results are analyzed.According to the demodulation problem existing in the traditional receiver structure,the receiver design focuses on two directions of high reliability and low complexity detection.In this paper,two joint demodulation algorithms are proposed,which are joint decoding algorithm based on sorting and mapping and joint demodulation algorithm based on parallel maximum likelihood estimation.And the system model of these two demodulation algorithms is described.These two algorithms reduce the complexity of the demodulation algorithm.According to the system pre-defined codebook used,the actual computational space is pre-exhausted to achieve pre-loading and reduce the time of a single operation.The parallel computing optimization is also carried out for the hardware implementation of the algorithm,and the hardware resources are fully utilized to accelerate the running speed of the demodulation algorithm.This paper also simulates and analyzes the performance of these two demodulation algorithms.Finally,the proposed access transport system is implemented using a USRP device.In this paper,the design of the equivalent digital up-and-down frequency converter enables the system to transmit and receive correctly.In this paper,a joint orthogonal and non-orthogonal frame structure design scheme is proposed to solve the problem that the channel estimation is interfered by inter symbol in the process of non-orthogonal transmission.The signal packet decision based on this frame structure and the error estimation in time-frequency domain and synchronization algorithm are completed.Use the official development tools in Matlab to configure and debug the parameters of the system,complete the construction of the actual transceiver system,and test the actual parameters.After the actual system test and analysis,it shows that the transmitter and receiver modules designed by the paper can support the operation of the system well in the scenario of massive user access,high-speed information transmission and high spectral efficiency.