BioComm: Biocompatible Physical Layer Design for Wireless Intra-Body Communications

In-vivo Wireless Nanosensor Networks (iWNSNs) consist of nano-sized communicating devices with unprecedented sensing capabilities that operate inside the human body in real-time. The current state-of-the-art in nanoelectronics and nanophotonics points to the Terahertz (THz) band (0.1-10 THz) and the optical frequency bands (infrared, 30-400 THz, and visible, 400-750 THz) as the promising spectral bands for nanosensor communications. In this paper, we propose and analyze a biocompatible modulation technique for iWNSNs. A mathematical framework is formulated to optimize the parameters of an adaptive Time Spread On-Off Keying (OOK) pulse-based modulation. This optimization considers both the physics of the intra-body optical channel and the light-matter interactions, along with the resulting photo-thermal effects in biological tissues. The outcomes of the analytical optimization model are validated through extensive numerical simulations. The results highlight a trade-off between link efficiency and the biocompatibility of the transmitted signals. Numerical analysis shows that the proposed biocompatible modulation technique can easily achieve a Bit Error Rate (BER) of $10<^>{-2}$ before coding, within the bio-safety measures, indicating a reliable intra-body channel for data transmission. This means that the channel can effectively convey information, such as health monitoring data or control signals for medical devices, without significant data loss or corruption.