Research On Various Postures Channel Modeling And Characteristics Based On Human Body Communication

With the continuous development and application of wearable devices,the continuous combination of biomedical field and communication technology,the development of wireless body area network has gradually attracted people's attention.Human body communication technology,which takes human body as communication medium,has the advantages of low power consumption,low radiation,high efficiency and strong anti-interference compared with traditional communication methods,and is more suitable for practical application.In order to consider the influence of human body posture on human body channel,a more practical human electromagnetic model is constructed.In this paper,we will study the influence of human posture on the channel from two aspects:dynamic posture and static postureFirstly,starting from the electromagnetic characteristics of human tissues,the paper analyzes the mechanism of the relative dielectric constant and conductivity of human tissues changing with the frequency,age and other parameters,and points out the propagation mode and mechanism of electromagnetic wave around human body in the frequency range of 10-50 MHz,from the propagation part of body surface,the absorption characteristics of electromagnetic wave in the body and the diffraction characteristics caused by encountering shielding objects.Secondly,the mathematical expression of the body surface path loss model is obtained through simulation and fitting,and the body surface non-direct link is included in the research scope,pointing out that the non-direct link still conforms to the transmission characteristics of the surface communication.In addition,the direct-link and the non-direct link are compared and analyzed,and the conclusion that the surface distance and the straight-line distance have different effects on the path loss characteristics is obtained.In the second part of the article,the possible postures of human body are divided into two parts: dynamic and static postures.The dynamic simulation analysis of the human body's single continuous movement posture includes two typical large-scale movements:arm swinging and leg kicking.Through electromagnetic simulation,the influence ofhuman body's movement on the inherent channel and active channel of the body surface is observed,and obtain the conclusion that the human body's movement will significantly reduce the loss of part of the link path,and the influence of the earth on the electromagnetic wave is considered,the gain of leg link transmission is from specular reflection of electromagnetic wave.Next,the static postures such as sitting,lying are simulated,and the power delay distribution(PDP)characteristics of different postures are combined.The cumulative distribution function(CDF)including path gain,peak time and other parameters is fitted to get a complete mathematical model under various postures characteristics.