Simulation Study on BER Performance of DS-UsWB Intrabody Communication

The water content of human soft tissues is as high as 65%, so ultrasound has advantages in low attenuation, low risk of disease, and limited interference range in human soft tissues, making it advantageous for communication in the body. However, the ultrasonic human channel has the characteristics of dense multipath, so the signals that reach the receiver through multiple paths of reflection and refraction overlap to generate multipath interference, which affects communication reliability. The existing research avoids multipath overlap and its interference by emitting extremely short pulses of ultrasound, but it is difficult to achieve ultra wideband ultrasound probes with large directional angles. The actual pulse width generated by the probe is not small enough, so multipath overlap will occur at the receiver and the interference cannot be ignored in signal judgment. In order to study the distribution characteristics of multipath interference in the body and its impact on wideband ultrasound human body communication, this paper used the k-Wave simulation toolkit to model the ultrasound human body channel in 3D. Then the channel impulse response was obtained through simulation experiments, and the statistical characteristics of multipath delay distribution were analyzed and curve fitting was performed. Based on the decision mechanism of the receiver, the multipath interference of the human channel was estimated, and the lower bound of the bit error rate (BER) for direct sequence spread spectrum ultrasonic broadband (DS-UsWB) was derived. The effectiveness of this lower bound of BER was verified through Monte Carlo experiments. Experimental results indicate that multipath interference cannot be ignored when the signal-to-noise ratio is low, and the communication performance can be improved by adjusting spread spectrum code length.