Conductive Intracardiac Communication Based on LC-PPM Modulation and Demodulation Method

Conductive intracardiac communication (CIC) is crucial for synchronizing dual-chamber leadless pacemakers (LLPMs) but struggles with high in vivo channel attenuation and microwatt-level power constraints, leading to synchronization loss. To address these challenges, this paper proposes a highly reliable, low-power low duty cycle pulse position modulation (LC-PPM) method. By utilizing an ultra-low duty cycle transmission mechanism, LC-PPM significantly minimizes average power consumption while maintaining a high instantaneous signal-to-noise ratio. Based on this method, a corresponding CIC communication system featuring a highly energy-efficient transceiver is designed. The transmitter implements a carrier phase-aligned mechanism to eliminate energy fluctuations. Meanwhile, the receiver employs a hybrid architecture that decouples synchronization and demodulation. It uses preamble interval matching and a 'windowed resynchronization' mechanism to establish a stable time base and resolve clock offsets under low signal-to-noise ratios. Ex vivo porcine heart experiments demonstrate that at a data rate of 62.5 kbps, the LC-PPM system maintains a near 100 % symbol synchronization rate (SSR) for bit energies above 31.6 pJ. Achieving the standard 10-4 bit error rate (BER) requires an average energy per bit of only 112.2 to 141.3 pJ, improving energy efficiency by 7 to 8 dB over conventional on-off keying (OOK). This approach offers a promising, high-reliability physical layer solution for next-generation LLPMs.