Enabling the Internet of Bodies Through Capacitive Body Channel Access Schemes

The Internet of Bodies (IoB) is an imminent extension of the vast Internet of things (IoT) domain, where wearable, ingestible, injectable, and implantable smart objects form a network in, on, and around the human body. Even though on-body IoB communications are required to occur within very close proximity of the human body, on-body wireless radio frequency (RF) IoB devices unnecessarily extend the coverage range beyond the human body due to their radiative nature. This eventually reduces energy efficiency, causes co-existence and interference issues, and exposes sensitive personal data to security threats. Alternatively, capacitive body channel communications (BCC) exhibit much less signal leakage by confining signal transmission to the human body and experience substantially less propagation loss than RF systems as body tissues has better conductivity than surrounding air. Furthermore, the BCC band (10-100 MHz) decouples the transceiver size from the carrier wavelength, eliminating the need for complex and power-hungry radio front-ends. Therefore, capacitive BCC is a key enabler to reach the ultimate design goals of ultra-low-power, high throughput, and small form-factor IoB devices. Albeit these attractive features, the communication and networking aspects of the capacitive BCC are not thoroughly explored yet. This paper is the first to model orthogonal and non-orthogonal body channel access schemes with or without cooperation among the IoB nodes. In order to address the quality of service (QoS) demand scenarios of different IoB applications, we present and formulate max-min rate, max-sum rate, and QoS sufficient operational regimes, then provide solution methodologies for optimal power and phase time allocations. Extensive numerical results are analyzed to compare the performance of orthogonal and non-orthogonal schemes with and without cooperation for various design parameters under prescribed QoS regimes.