Dynamic Channel Characteristic Analysis and Modeling of Conductive Intracardiac Communication Based on Sinusoidal Response and Impulse Response

Conductive intracardiac communication (CIC) is one of the most innovative and promising communication technologies in multi-point cardiac pacing schemes that utilize the heart as the transmission channel in recent years. Current research predominantly focuses on the static channel characteristics, with only limited investigations into the dynamic responses of amplitude-frequency and amplitude-time behaviors. Designing CIC systems solely on the basis of static properties can result in inaccurate channel estimation, distorted channel state information (CSI), elevated bit error rate (BER), and overall degradation of system communication performance. To solve the problems of dynamic channel measurement and modeling of the heart, this paper for the first time proposes a dynamic channel modeling method for CIC based on sinusoidal response and impulse response. Firstly, we develop a physical simulation and miniaturized measurement setup to measure dynamic cardiac channel, and analyze the amplitude-frequency characteristics and amplitude-time characteristics. The influence of factors such as instrument differences, heart rate, flow rate and comparative experiments of free electrodes and fixed electrodes on the channel characteristics are also discussed. Secondly, we systematically analyze the path loss, shadowing effect, multipath effect and Doppler effect of the CIC channel. Combined with the dynamic channel characteristics and parameters, we propose a composite fading dynamic channel model and analyze the BER performance of baseband signals transmission and On-Off Keying (OOK) modulation systems. We can conclude that (1) The CIC channel exhibits capacitive characteristics. The fluctuation of the channel gain of the free electrode is mainly caused by motion artifacts. The fixed electrode can effectively suppress this interference. (2) The dynamic channel gain of CIC varies periodically with the heartbeat, and the fluctuation range of the signal is less than 1-2 dB. This is due to the length change of the myocardial tissue. (3) The CIC channel still presents extremely weak shadow fading, no significant multipath, and no measurable Doppler characteristics under dynamic conditions, belonging to an extremely slow fading channel. This work provides effective dynamic channel measurements approach and parameter basis for the transceiver design of CIC and a reliable model for the simulation for CIC systems.