Study On Channel Modeling And Channel Capacity Of Radio Vortex Communications

As a novel communication technology,radio vortex adopts the physical property of orbital angular momentum as a new dimension for multiplexing,can simultaneously transmit multiple channels of information in the same frequency band,and improve the capacity of the communication system greatly.It not only breaks through the capacity bottleneck of traditional wireless communication systems,but also solves the shortage problem of spectrum resources effectively.In this thesis,the channel model and channel capacity of radio vortex are studied in depth from a theoretical perspective.The main research contents of this thesis are as follows:1.According to the signal characteristics of radio vortex communications,the vortex signal model is modeled from the perspectives of theoretical analysis and practical applications.The model is employed to describe the essential characteristics of the vortex signals.The simulation results show that it is difficult to distinguish between the vortex signals and the conventional radio signals in the time domain or the frequency domain.However,all the signals are easily distinguished in the vortex phase domain.Therefore,the characteristics of the modeled vortex signal can be shown through three-dimensional graphics.2.For the modeling problem of radio vortex communication channel,the model characteristics of the Laguerre-Gaussian mode in the optical field are studied.Based on which,the free-space vortex channel is modeled from theoretically combined with the traditional free space propagation model.The model is employed to describe the propagation characteristics of the vortex channel in a free-space scenario.Compared with the existing vortex channel model,the proposed model not only includes the traditional free-space propagation model,but also the influence of topological charge on the fading characteristics of the vortex channel.Simulation results show that the free-space vortex channel model could characterize the vortex channel in free space.3.For the current situation of spectrum resources shortage,the application of orbital angular momentum in wireless communication systems is studied.Furthermore,the system model of the radio vortex system and its implementation method are proposed.Specifically,the vortex modulation and demodulation methods and the methods of orbital angular momentum multiplexing and demultiplexing are proposed.From the perspective of system implementation,the vortex antenna is designed to realize the modulation of the vortex signals,and the azimuth integral method is proposed to realize the demodulation of the vortex signals.Based on this idea,the channel capacity of the radio vortex system is analyzed,and the capacity formula is given.Simulation results show that the proposed radio vortex system could achieve higher capacity and better bit error rate performance than that of conventional wireless communication systems by multiplexing the orbital angular momentum with the same number of channels.4.For the applications of multi-antenna technology,the combination of orbital angular momentum and traditional multiple-input multiple-output system is studied.The system model of the radio vortex–multiple-input multiple-output(RV–MIMO)system is proposed.Multiple vortex antennas are utilized to construct a uniform circular array(UCA)at the transceiver in free space,and the transmission and reception of the vortex signals are realized.The channel model of the RV–MIMO system is modeled to analyze the channel capacity.By changing the relative position of the transmitting and receiving antennas,the optimal phase conditions required for the maximum capacity of the channel are analyzed and derived.Moreover,the channel capacity of the fixed UCA and the movable UCA at the receiver are simulated.The results show that the channel capacity of the proposed RV–MIMO system is higher than that of the conventional MIMO system.In summary,the thesis studies the signal and channel models of the radio vortex communications,and analyzes the channel capacity of the radio vortex and RV–MIMO systems.The proposed models and methods have both theoretical and practical significance.