Research On Wireless Propagation Models Of Indoor Complex Human-Cyber-Physical Scenarios

Indoor wireless communication technology plays a key role in up-to-date and future wireless communication systems.With the advances of technology,indoor wireless communication has gradually evolved from traditional voice,data and multimedia services to new indoor scenarios based on the combination of 5G technology and artificial intelligence,Internet of Things,cloud computing,big data and edge computing.A large number of humans,objects,and equipment in production,activities,connections,and interactions are in these scenarios and they are forming indoor complex human-cyber-physica scenarios.Indoor wireless channels are featured with a variety of scenarios,abundant multipaths and small enclosed structures,influence of human and object presence on propagation characteristics of wireless channels in such environments are more significant than in outdoor and traditional indoor environments.Hence,a comprehensive understanding of propagation characteristics of indoor complex human-cyber-physical scenarios has great theoretical significance and applicable value.This thesis concentrates on the scientific problem of propagation models of indoor complex human-cyber-physical scenarios,and extensive wireless channel measurements are performed under typical indoor environments including meeting room,corridor,stairwell and office.The investigated frequencies range from popular frequencies such as 2.6GHz and 3.5GHz to the potential frequencies such as 9?12GHz.Propagation characteristics of wireless channels in scenarios with different occupant densities,hand-held terminals and obstructed line-of-sight cases are investigated.Models of different properties for indoor wireless channels with human presence are proposed.The main work and contributions are listed as follows:(1)A path loss model for three typical indoor environments,including conference rooms,stairs and corridors,under different occupant densities is proposed,which provides a solution for the accurate prediction of path loss in indoor complex human-cyber-physical scenarios.In this model,the power delay function is modeled as a superposition of a reverberation component whose path loss is independent of distance and dependent of occupant density,and a primary component that follows the log-distance decaying,then the path loss is obtained by integration.Model parameters are fitted based on a large number of measurement results.Predicted values of this model are in good agreement with the measurement data.Compared to the existing log-distance path loss models,the proposed model can accurately predict the path loss with clearer explications about the abnormal value of the path loss factor,and can extract the fading characteristics of primary component by removing the influence of the reverberation component,in order to provide a more accurate model for the link budget of typical indoor complex human-cyber-physical scenarios.(2)Further,a reverberation time model containing the number of people and environmental factors is proposed.The model provides a method for fast calculation of the reverberation time in indoor complex scenarios,and solves the problem of modeling changes caused by the increase or decrease in the number of people in the room or changes in the environment.Validation shows that the proposed model has higher accuracy than existing models.The model can also be easily extended to similar scenarios,and adaptation to scenarios of the model can be achieved by updating the number of people factor and the environmental factor of the scenario.In addition,the prediction method of power delay propfile is improved,and the complexity of modeling algorithm of Nakagami-m distribution factor is reduced by introducing the reverberation time parameter.(3)Analysis and modeling of propagation characteristics in Massive MIMO indoor office environment are performed.In a typical office environment,a measurement platform consisting of a 32-antenna Massive MIMO array and multi-antenna handsets with different numbers of antennas is mounted.Channel measurements and channel frequency response modeling at 3.5GHz are carried out.The research results show that the channel ergodic capacity increases with the increase of the number of terminal antennas.In the hand-held situation,the average of the traversal capacity is not significantly different from the normal situation,but the channel performance is further degraded in the low-capacity section.(4)On the basis of the above work,a wireless propagation model for indoor environment containing user's hand-held effect factor is proposed.The model fully considers the user's hand-held effect,correlation effects at receiver and transmitter,and coupling effects.And it models the handheld effect factors as random variables with amplitudes that follow a log-normal distribution and phases that follow a uniform distribution.The coupling effect factor is modeled as a random variable whose amplitude follows the Nakagami-m distribution and whose phase follows the uniform distribution.The predicted ergodic capacity and interruption capacity values of the model are consistent with the measurement.Compared to the existing Kronecker model and Weichselberger model,the model has higher accuracy,clearer physical meaning and stronger scalability.(5)A wireless propagation model for X-band indoor complex human-cyber-physical scenarios is proposed.The model uses particle filtering method to enable the dynamic prediction of channel parameters in complex human-cyber-physical scenarios.The primary decaying mechanism of the multipath component is used to establish the state equation,and dynamic prediction model in the time-delay domain is performed.The model can accurately predict the power delay spectrum and average delay parameters.Compared with the traditional TDL and other static models,it can enable dynamic measuring and real-time modeling.The measurement is helpful for the systematic study of indoor wireless propagation characteristics in higher frequency bands.The proposed model can be used in providing support to the development of algorithms such as sensory data collection and active channel measurement in typical complex human-cyber-physical scenarios such as massive machine communications.The work and contributions on propagation characteristics of indoor wireless channels of the thesis can provide important support for the coverage planning,physical layer design,system simulation and development in future mobile communication systems.