Researches On Short Range Wireless Channel Propagation Characteristics In Indoor Environments For Small Cell Scenarios

Ultra dense small cell is regarded as a key transmission technology in the current and further wireless communication systems.Its application depends on the comprehensive investigation of the propagation characteristics of the short range wireless channel in indoor environments.The short range wireless channels in indoor environments are featured with various scenarios,complicated environments and short cell coverage range,therefore,their propagation properties are different from the traditional ones.The fully understanding of the propagation characteristics of short range wireless channel in indoor environments for small cell scenarios not only has great theoretical significance,but also has high practical value.In this dissertation,the propagation characteristics of the short range wireless channel in indoor environments are researched,and extensive wireless channel measurements are conducted under typical indoor stair,corridor,office,and hospital environments.Then,the short range wireless channel power delay profile model,the receiving antenna height dependent path loss model and the root mean square delay spread model,and the body area network autoregressive channel impulse response model in indoor environments are established based on the extensive measured data,additionally,an indoor short range wireless channel simulator is developed.The main contributions of this dissertation are listed as follows.(1)A stochastic discrete tapped delay line power delay profile model under three typical indoor environments,including stair,corridor and office is proposed.The simulation of the power delay profile of the short range wireless channel in indoor environments for small cell scenarios can be realized by the proposed model.It is found that the amplitude of the proposed model at each tap and receiving point follows the Nakagami-m distribution with truncated lognormally distributed shape parameters and distance and propagation delay dependent scale parameters.The proposed model is found to be more accurate than the existing stochastic tapped delay line model of the long range wireless channel in indoor environments.(2)A receiving antenna height dependent path loss model of the short range wireless channel in indoor environments for small cell scenarios is proposed.The proposed model can describe the transmission loss caused by various heights and postures of users or states of mobile devices for small cell scenarios.By introducing the obstruction attenuation factor and receiving antenna height attenuation factor,the indirect and direct effects of receiving antenna height on the path loss are characterized,and a more accurate indoor path loss model with clear physical meaning is established.(3)Furthermore,an empirical model describing the relationship between the root mean square delay spread and path loss and a novel receiving antenna height dependent root mean square delay spread model are proposed.These models provide the method for fast calculating the root mean square delay spread,moreover,they can describe the multipath distribution variation caused by the change of the users' heights,postures and mobile devices' states for small cell scenarios.In addition,the closed form formulas for calculating the mean value and standard deviation of the root mean square delay spread are derived.They provide the method for fast estimating the degree of the multipath fading of specific indoor environments for small cell scenarios.(4)Based on the above mentioned work,the wireless channel propagation characteristics when the antenna is worn on the user are researched.An off-body channel autoregressive model in indoor environments for small cell scenarios is proposed.The channel impulse response of the short range off-body channel with rich multipath components in indoor environments for small cell scenarios can be described by the proposed model.In this model,the magnitude and phase of the poles of the autoregressive transfer function are normally distributed and uniformly distributed random variables,and the variance of the input signal follows the normal distribution.Compared with the conventional tapped delay line model,the proposed model is verified to have higher accuracy and lower complexity.(5)Based on the proposed models,a short range wireless channel simulator in indoor environments is developed.The simulations and engineering applications of the aforementioned proposed models can be realized by such a channel simulator.Its software architecture is proposed.This channel simulator can display the wireless propagation characteristics,emulate the real realistic channel,calculate the link budget and show the performance of communication signal run on the realistic channel.Compared with the existing channel simulator,it has the advantages of measurement-based,easy to realize,efficient and extensible.These researches on the wireless channel propagation characteristics,channel models and channel simulator can provide theoretical foundation,experimental basis and engineering support for the coverage planning,link-level simulation,physical layer algorithm design,performance analysis and system development of ultra dense small cells and Internet of Things in future mobile communication systems.