Research And Design Of Multi-user Transmission Methods By Exploiting Interactions Among Signals

With the rapid development of wireless communication technology and the wide use of intelligent mobile terminal equipment,the amount of data transmitted by wireless networks presents explosive growth.On the one hand,the base station and the wireless access point are intensively deployed to meet the requirements of high-rate transmission of users,resulting in interference to become an important factor affecting network performance.On the other hand,the dramatic increase in the volume of wireless services has led to an increasing scarcity of spectrum resources available for communications.Therefore,it is necessary to eliminate interference and improve spectral efficiency.The main work of this thesis is as follows:First,considering that the multi-user communication process is interfered,we will propose a Virtual Signal Division Multiple Access(VSDMA).With this scheme,the coordinating transmitter constructs a coordinating signal,and adjusts the multi-user signal relationship at the public receiver.That is,the interaction between wireless signals is used to restore the desired signals of multi-channel orthogonality in public receiver.Calculating the coordinating signal components required to restore the all desired signals,it interacts with the actual transmission signal of the desired transmitter,and can restore the desired signal that is orthogonal to each other with other desired signals at the public receiver,then the coordinating signal is obtained by synthesizing the coordinating signal components.Therefore,the coordinating transmitter only sends a signal to the receiver can restore multiple user data without interference.The proposed method can not only avoid the degradation of desired transmission’s quality incurred by adjusting the transmitted signal at the desired transmitters,but also circumvent the problem of desired signal’s power loss at the public receivers while it suppressing interference.In addition,we have done different VSDMA implementations based on orthogonal decomposition and non-orthogonal decomposition of the coordinating signal-Virtual Signal Orthogonal Decomposition based Multiple Access(VSODMA),and Virtual Signal Non-Orthogonal Decomposition based Multiple Access(VSNODMA).Compared to other interference management methods,the method can significantly improve the spectral efficiency of multi-user communication systems.In addition,based on the problem of tight spectrum resource,this paper proposes Intelligent Reflecting Surface Aided Spectrum Sharing(IRS-SS).In underlay mode,the Intelligent Reflecting Surface(IRS)is controlled by the primary user,and the primary user can enhance self-signal transmission by adjusting the reflection parameters of the IRS.Cognitive users use the openness of the IRS to achieve cognitive data transmission.In order to eliminate the interference at the primary receiver and cognitive receivers,a collaborative cognitive transmitter is selected.The collaborative cognitive transmitter obtains channel information of primary and other non-collaborative cognitive communication,and then designs precoding of each cognitive transmitter according to the information.And the equivalent interference at the primary receiver and each non-collaborative receiver can be aligned in the orthogonal direction of its desired reception signal.Last,the primary receiver and the non-collaborative cognitive receivers use matching reception,and collaborative cognitive receiver uses Zero-Forcing.This method does not need to limit the transmit power of the cognitive transmitter,and can ensure the performance of cognitive communication without interfering with the premise of authorized user communication,and realizes the frequency spectrum sharing of multi-user.The simulation results show that IRS-SS can avoid cognitive communication interference to authorized communication,and effectively manage interference between cognitive communication,significantly enhance the utilization efficiency of spectrum resources.