VHDL implementation of communication methods for the next-generation of wearable and implantable devices

Advancements in the field of wearable and implantable technologies have the potential to improve significantly the healthcare monitoring and the therapy efficiency, while reducing medical costs. To achieve a continuous, unobtrusive and local monitoring of physiological parameters, it is essential the development of highly miniaturized and energy efficient devices equipped with sensing, computing and wireless communication capabilities. Recent research effort has raised the prospect of moving beyond the well-established concept of implantable and wearable systems, through the conceptualization of the "Smart Dust". The tight resource-constraints of such systems generate many challenges, which can be addressed through new design approaches and optimization strategies, especially concerning size and power consumption. The proposed thesis project aims to examine the feasibility of communication methods for the next-generation of wearable and implantable devices. In particular, the problem of the transmission of multiple sensed signals from the same node towards the wireless channel is addressed. One promising solution consists in the implementation of the digital mixing as a method to combine multiple input signals into a single output stream. The innovative aspect of the work developed consists in the detailed investigation of the trade-offs in terms of power consumption versus error performances of digital mixing, to demonstrate its suitability for extremely resource-constrained applications. The main objective is the research of the sources of error and power consumption, along with the study of their impact on the system. This is achieved with dedicated error and power analysis, both relying on the VHDL implementation of the method under discussion. Specifically, the study of the error performance is carried out with the aid of functional simulations, whereas the power analysis is performed through the synthesis of the digital circuit. The wireless communication capabilities require to address also the issue of the choice of a suitable modulation technique for such devices. To this end, a comparative study of digital modulation techniques, where power efficiency represents the major system level metric, showcases Frequency-Shift-Keying (FSK) and On-Off-Keying (OOK) are effective solutions for the signal transmission across the wireless channel. The final BER analysis, aided by MATLAB simulations, demonstrates that FSK performs better under Additive White Gaussian Noise (AWGN). Lastly, open issues are discussed for the development of the future work.