Dynamic Channel Modeling and OFDM System Analysis for Capacitive Coupling Body Channel Communication

A Re-Configurable Body Channel Transceiver Towards Wearable and Flexible Biomedical Sensor Networks

Body channel communication (BCC) has become a promising candidate in wireless body area networks (WBAN) due to its advantages in energy efficiency and security. However, BCC transceivers face two challenges: diverse application requirements and varying channel conditions. To overcome these challenges, this article proposes a re-configurable architecture for BCC transceivers (TRXs), whose key parameters and communication protocols can be software-defined (SD) according to the requirements. In the proposed TRX, the programmable direct-sampling receiver (RX) is a combination of a programmable low-noise amplifier (LNA) and a fast-convergent successive approaching register analog-to-digital converter (SAR ADC), to achieve simple but energy-efficient data reception. The programmable digital transmitter (TX) is essentially implemented by a 2-bit DAC array to transmit either wide-band carrier-free signals like 4-level pulse amplitude modulation (PAM-4) or non-return-to-zero (NRZ) or narrow-band carrier-based signals like on-off keying (OOK) or frequency shift keying (FSK). The proposed BCC TRX is fabricated in a 180-nm CMOS process. Through an in-vivo experiment, it achieves up to 10-Mbps data rate and 119.2 pJ/bit energy efficiency. Moreover, the TRX is able to communicate under long-distance (1.5 m) and body-shielding conditions by switching its protocols, which shows the potential to be deployed in all categories of WBAN applications.

Technological Requirements and Challenges in Wireless Body Area Networks for Health Monitoring: A Comprehensive Survey

With the rapid growth in healthcare demand, an emergent, novel technology called wireless body area networks (WBANs) have become promising and have been widely used in the field of human health monitoring. A WBAN can collect human physical parameters through the medical sensors in or around the patient’s body to realize real-time continuous remote monitoring. Compared to other wireless transmission technologies, a WBAN has more stringent technical requirements and challenges in terms of power efficiency, security and privacy, quality of service and other specifications. In this paper, we review the recent WBAN medical applications, existing requirements and challenges and their solutions. We conducted a comprehensive investigation of WBANs, from the sensor technology for the collection to the wireless transmission technology for the transmission process, such as frequency bands, channel models, medium access control (MAC) and networking protocols. Then we reviewed its unique safety and energy consumption issues. In particular, an application-specific integrated circuit (ASIC)-based WBAN scheme is presented to improve its security and privacy and achieve ultra-low energy consumption.

A Time-Frequency Measurement and Evaluation Approach for Body Channel Characteristics in Galvanic Coupling Intrabody Communication

Intrabody communication (IBC) can achieve better power efficiency and higher levels of security than other traditional wireless communication technologies. Currently, the majority of research on the body channel characteristics of galvanic coupling IBC are motionless and have only been evaluated in the frequency domain. Given the long measuring times of traditional methods, the access to dynamic variations and the simultaneous evaluation of the time-frequency domain remains a challenge for dynamic body channels such as the cardiac channel. To address this challenge, we proposed a parallel measurement methodology with a multi-tone strategy and a time-parameter processing approach to obtain a time-frequency evaluation for dynamic body channels. A group search algorithm has been performed to optimize the crest factor of multitone excitation in the time domain. To validate the proposed methods, in vivo experiments, with both dynamic and motionless conditions were measured using the traditional method and the proposed method. The results indicate that the proposed method is more time efficient (Tmeas=1 ms) with a consistent performance (ρc > 98%). Most importantly, it is capable of capturing dynamic variations in the body channel and provides a more comprehensive evaluation and richer information for the study of IBC.

Body-Area Powering With Human Body-Coupled Power Transmission and Energy Harvesting ICs

This paper presents the body-coupled power transmission and ambient energy harvesting ICs. The ICs utilize human body-coupling to deliver power to the entire body, and at the same time, harvest energy from ambient EM waves coupled through the body. The ICs improve the recovered power level by adapting to the varying skin-electrode interface parasitic impedance at both the TX and RX. To maximize the power output from the TX, the dynamic impedance matching is performed amidst environment-induced variations. At the RX, the Detuned Impedance Booster (DIB) and the Bulk Adaptation Rectifier (BAR) are proposed to improve the power recovery and extend the power coverage further. In order to ensure the maximum power extraction despite the loading variations, the Dual-Mode Buck-Boost Converter (DM-BBC) is proposed. The ICs fabricated in 40 nm 1P8M CMOS recover up to 100 μW from the body-coupled power transmission and 2.5 μW from the ambient body-coupled energy harvesting. The ICs achieve the full-body area power delivery, with the power harvested from the ambiance via the body-coupling mechanism independent of placements on the body. Both approaches show power sustainability for wearable electronics all around the human body.

Investigation and Modeling of Multi-Node Body Channel Wireless Power Transfer

Insufficient power supply is a huge challenge for wireless body area network (WBAN). Body channel wireless power transfer (BC-WPT) is promising to realize multi-node high-efficiency power transmission for miniaturized WBAN nodes. However, the behavior of BC-WPT, especially in the multi-node scenario, is still lacking in research. In this paper, the inter-degeneration mechanism of a multi-node BC-WPT is investigated based on the intuitive analysis of the existing circuit model. Co-simulation in the Computer Simulation Technology (CST) and Cadence platform and experiments in a general indoor environment verify this mechanism. Three key factors, including the distance between the source and the harvester, frequency of the source, and area of the ground electrodes, are taken into consideration, resulting in 15 representative cases for simulation and experiments studies. Based on the simulation parameters, an empirical circuit model to accurately predict the received power of multiple harvesters is established, which fits well with the measurement results, and can further provide guidelines for designs and research on multi-node BC-WPT systems.

Comparable Investigation of Characteristics for Implant Intra-Body Communication Based on Galvanic and Capacitive Coupling

Implanted devices have important applications in biomedical monitoring, diagnosis and treatment, where intra-body communication (IBC) has a decent prospect in wireless implant communication technology by using the conductive properties of the human body to transmit a signal. Most of the investigations on implant IBC are focused on galvanic coupling type. Capacitive coupling IBC device seems hard to implant, because the ground electrode of it seemingly has to be exposed to air. Zhang et al. previously proposed an implantable capacitive coupling electrode, which can be totally implanted into the human body [1], but it lacks an overall characteristic investigation. In this paper, a comparable investigation of characteristics for implant intra-body communication based on galvanic and capacitive coupling is conducted. The human arm models are established by finite element method. Meanwhile, aiming to improve the accuracy of the model, electrode polarization impedance (EPI) is incorporated into the model, and the influences of electrode polarization impedance on simulation results are also analyzed. Subsequently, the corresponding measurements using porcine are conducted. We confirm good capacitive coupling communication performances can be achieved. Moreover, some important conclusions have been included by contrastive analysis, which can be used to optimize implant intra-body communication devices performance and provide some hints for practical IBC design. The conclusions also indicate that the implant IBC has promising prospect in healthcare and other related fields.