Research On Measurement And Modeling Method Of X-band Indoor Off-body Channel

With the booming development of Io T communications,the X-band has been adopted by the IEEE 802.15.6 standardization group as the recommended frequency band for off-body communications in body area networks.Usually,before designing a communication system,it is considered to be necessary to measure and model the wireless channel in the target frequency band and specific scenarios,and study the influence of the propagation characteristics on the network performance.Through the measurement and modeling of the X-band indoor wireless off-body channel,the influence of the distance,angle and height between transmit and receive antennas on the channel propagation characteristics are considered in this thesis.Three typical indoor scenarios(enclosed office,large conference room,and long and narrow corridor)have been selected as the measurement scenarios,and the most appropriate channel measurement method is selected according to the characteristics of each scenario to build an sweep frequency measurement system of X-band indoor wireless off-body channel.Taking into account the requirements of later data processing,the basic parameters of the frequency sweep measurement system are set,and the X-band wireless off-body channel measurement experiments for each indoor scenario have been designed and completed.First,the large-scale fading characteristics of X-band indoor wireless off-body channels are studied,and a new path loss model is established in this thesis.Based on the traditional floating interceptc(FI)path loss model,the influence of the rotation angle of the human body and the distance between transmit and receive antennas on the path loss is considered.Under the condition of different distances,it was found that the human occlusion factor has a sine function relationship with the angle,and the occlusion factor coefficient has an exponential function relationship with the distance.A path loss model related to the angle and distance is proposed.Under the condition of different transmitting antenna heights,the FI path loss models were fitted respectively.It is found that the path loss factor and floating intercept all show a cubic function relationship with the height,and a path loss model related to the height and distance is established.Finally,by analyzing the statistical characteristic parameters of shadow fading,these path loss models are proposed in this thesis,which have high modeling accuracy and multi-scenarios applicability.Second,the small-scale fading characteristics of X-band indoor wireless off-body channels are explored,and a new root mean square(RMS)delay spread model is established in this thesis.It is found that the measured values of path loss and RMS delay spread have the same trend under different antenna distances,angles and heights.It is assumed and proposed that there is a linear correlation between them.Therefore,the RMS delay expansion model related to path loss is proposed,and then the RMS delay expansion model related to the distance,angle and height is obtained according to the new path loss model in this thesis.Afterwards,the RMS delay spread model is proposed that in this thesis,and it is considered to be a random variable conforming to the normal distribution.The mean value is determined by the distance,angle and height between transmit and receive antennas.The standard deviation is related to the shadow fading standard deviation.It is found that the higher modeling accuracy of the path loss model,and the higher modeling accuracy of the RMS delay spread model and multi-scenario applicability of the models in this thesis,.A new path loss and RMS delay expansion model is proposed in this thesis,and environmental information is contained in practical application scenarios,so it is considered higher modeling accuracy.Several typical indoor scenarios are researched,which prove that these models in this thesis have the applicability of diverse indoor scenarios.Measuring and modeling the X-band indoor wireless off-body channel,and exploring the propagation characteristics of the channel,which will be used to achieve the optimal design of the physicallayer algorithm and the reasonable allocation of spectrum resources.The basic theory of wireless communication is enriched,and the development of wearable communication is promoted.It is considered to have very important practical significance and industrial prospects.