Intra-body Communication System Research Articles

Ultrasonic Indexed Modulation and Multiple Access for Intra-Body Networks

Intra-body communication (IBC) plays a significant role in future health care systems. This article proposes a pulse-based ultrasonic index modulation (UsIM) to enable high data rate and low power IBCs. Two grouping-based UsIM strategies, namely ultrasonic grouped-chip indexed modulation (UsCIM) and ultrasonic chip-group indexed modulation (UsGIM), are proposed to implement multiple access for intra-body networks (IBNs). UsCIM uses the chip indices in a group to convey additional information bits for a biosensor node, while UsGIM uses the group indices and each node occupies one chip in a group. Three receivers, including the maximum likelihood (ML), the maximum ratio combination (MRC), and the energy detection (ED) receivers, are then proposed and studied. The theoretical bit-error rate (BER) upper bound for the ML receiver, and theoretical BER expressions for the MRC and ED receivers are derived. The system performance metrics in terms of complexity, throughput and energy efficiency are analyzed. The analytical and simulation results reveal that UsGIM achieves a lower BER than UsCIM under channel fading and multipath effect. Both UsCIM and UsGIM achieve higher throughput and energy efficiency than the existing IBC systems, and both strategies are important for energy-constrained implanted IBNs.

IB-MAC: Transmission Latency-Aware MAC for Electro-Magnetic Intra-Body Communications.

Intra-body Communication (IBC) is a communication method using the human body as a communication medium, in which body-attached devices exchange electro-magnetic (EM) wave signals with each other. The fact that our human body consists of water and electrolytes allows such communication methods to be possible. Such a communication technology can be used to design novel body area networks that are secure and resilient towards external radio interference. While being an attractive technology for enabling new applications for human body-centered ubiquitous applications, network protocols for IBC systems is yet under-explored. The IEEE 802.15.6 standards present physical and medium access control (MAC) layer protocols for IBC, but, due to many simplifications, we find that its MAC protocol is limited in providing an environment to enable high data rate applications. This work, based on empirical EM wave propagation measurements made for the human body communication channel, presents IB-MAC, a centralized Time-division multiple access (TDMA) protocol that takes in consideration the transmission latency the body channel induces. Our results, in which we use an event-based simulator to compare the performance of IB-MAC with two different IEEE 802.15.6 standard-compliant MAC protocols and a state-of-the art TDMA-based MAC protocol for IBC, suggest that IB-MAC is suitable for supporting high data rate applications with comparable radio duty cycle and latency performance.

Performance Evaluation and Improvement of PER and Throughput in Galvanic-Coupling Intra-Body Communication Systems.

This study examined the following communication characteristics of contact and partially non-contact galvanic intra-body communication (IBC) systems using a human-body path loss model developed previously: 1) packet error rate (PER) calculation for the contact and partially non-contact IBC path, and PER improvement by the low-density parity check (LDPC) error correction code; and 2) signal-to-noise ratio (SNR) estimation using the blind SNR prediction method and throughput optimization using adaptive coding. The following results were obtained for these characteristics: 1) Applying the LDPC coding rate 3/4 through 1/4 can improve the required SNR by approximately 8~20 dB when PER = 10-2; and 2) the blind SNR prediction method can estimate SNR precisely, thus realizing appropriate throughput communication.

Neuro-Spike Communications With Multiple Synapses Under Inter-Neuron Interference

The nervous system is a complex intra-body communication system, called neuro-spike communications, for transferring vital information throughout the body. This system consists of unreliable neural components like axon and synapses. The nervous system can deal with the unreliability of its components by making use of multiple synapses. In this paper, we analyze the performance of neuro-synaptic channels consisting of multiple synapses. It is assumed that synaptic channels are subject to synaptic noise, random vesicle release, and inter-neuron interference. The optimal detection for two cases of multiple cooperative synapses and multiple interfering synapses is investigated. The closed-form expressions of the probability density function of variable quantal amplitude are derived that is used to calculate the probability of detection error.

Characterization of Impulse Radio Intrabody Communication System for Wireless Body Area Networks

Intrabody communication (IBC) is a promising data communication technique for body area networks. This short-distance communication approach uses human body tissue as the medium of signal propagation. IBC is defined as one of the physical layers for the new IEEE 802.15.6 or wireless body area network (WBAN) standard, which can provide a suitable data rate for real-time physiological data communication while consuming lower power compared to that of radio-frequency protocols such as Bluetooth. In this paper, impulse radio (IR) IBC (IR-IBC) is examined using a field-programmable gate array (FPGA) implementation of an IBC system. A carrier-free pulse position modulation (PPM) scheme is implemented using an IBC transmitter in an FPGA board. PPM is a modulation technique that uses time-based pulse characteristics to encode data based on IR concepts. The transmission performance of the scheme was evaluated through signal propagation measurements of the human arm using 4- and 8-PPM transmitters, respectively. 4 or 8 is the number of symbols during modulations. It was found that the received signal-to-noise ratio (SNR) decreases approximately 8.0 dB for a range of arm distances (5–50 cm) between the transmitter and receiver electrodes with constant noise power and various signal amplitudes. The SNR for the 4-PPM scheme is approximately 2 dB higher than that for the 8-PPM one. In addition, the bit error rate (BER) is theoretically analyzed for the human body channel with additive white Gaussian noise. The 4- and 8-PPM IBC systems have average BER values of 10−5 and 10−10, respectively. The results indicate the superiority of the 8-PPM scheme compared to the 4-PPM one when implementing the IBC system. The performance evaluation of the proposed IBC system will improve further IBC transceiver design.

Effects of human limb gestures on galvanic coupling intra-body communication for advanced healthcare system.

BackgroundIntra-Body Communication (IBC), which utilizes the human body as the transmission medium to transmit signal, is a potential communication technique for the physiological data transfer among the sensors of remote healthcare monitoring system, in which the doctors are permitted to remotely access the healthcare data without interrupt to the patients’ daily activities.MethodsThis work investigates the effects of human limb gestures including various joint angles, hand gripping force and loading on galvanic coupling IBC channel. The experiment results show that channel gain is significantly influenced by the joint angle (i.e. gain variation 1.09–11.70 dB, p < 0.014). The extension, as well as the appearance of joint in IBC channel increases the channel attenuation. While the other gestures and muscle fatigue have negligible effect (gain variation <0.77 dB, p > 0.793) on IBC channel. Moreover, the change of joint angle on human limb IBC channel causes significant variation in bit error rate (BER) performance.ConclusionsThe results reveal the dynamic behavior of galvanic coupling IBC channel, and provide suggestions for practical IBC system design.

Equivalent-Circuit Expression of Environmental Noise Electric Fields in Intrabody Communication Channels

In the development of intrabody communication systems, the most challenging goal is to protect against noise due to other electronic devices. In this paper, the equivalent-circuit expression of environmental noise electric fields (the so-called radiated noise) in intrabody communication channels are derived based on the theory of electrostatic fields. In addition, numerical examples are shown by means of electrostatic analysis based on the method of moments, and the results agree with those by full-wave analysis based on the finite-difference time-domain method and those by measurements. Therefore, it is concluded that the proposed circuit model can properly express the contribution of environmental noise electric fields.

Effect of transformer symmetry on intrabody communication channel measurements using grounded instruments

Transformers with one winding terminal symmetrical with respect to ground (capacitances between their terminals and ground are the same) are referred to as balun transformers, and are often used for decoupling in the measurements of the intrabody communication (IBC) system transmission characteristics. We measured IBC system amplitude and phase transmission characteristics using three types of galvanic decouplers: non-symmetric RF transformers, balun transformers with center tap grounded and balun transformers with center tap floating. Four possible electrode configurations (AA, AB, BA, and BB) and four electrode arrangements (GSGS, GSSG, SGGS, and SGSG), result in a total of 16 measurement scenarios for each of three measurement setups. We showed that the change in the measured amplitude for different signal and ground electrode arrangements while measuring with non-symmetric transformers is influenced by the transformer symmetry to the ground, and not the capacitive intrabody communication transmission characteristics. The change of the amplitude in case symmetric balun transformers are used is negligible for practical purposes.

Health Monitoring System Based on Intra-Body Communication

This paper presents a model of a Body Area Network (BAN) health monitoring system based on Intra-Body Communication. Intra-body Communication (IBC) is a communication technique that uses the human body as a medium for electrical signal communication. One of the visions in the health care industry is to provide autonomous and continuous self and the remote health monitoring system. This can be achieved via BAN, LAN and WAN integration. The BAN technology itself consists of short range data communication modules, sensors, controller and actuators. The information can be transmitted to the LAN and WAN via the RF technology such as Bluetooth, ZigBee and ANT. Although the implementations of RF communication have been successful, there are still limitations in term of power consumption, battery lifetime, interferences and signal attenuations. One of the solutions for Medical Body Area Network (MBANs) to overcome these issues is by using an IBC technique because it can operate at lower frequencies and power consumption compared to the existing techniques. The first objective is to design the IBC's transmitter and receiver modules using the off the shelf components. The specifications of the modules such as frequency, data rate, modulation and demodulation coding system were defined. The individual module were designed and tested separately. The modules was integrated as an IBC system and tested for functionality then was implemented on PCB. Next objective is to model and implement the digital parts of the transmitter and receiver modules on the Altera's FPGA board. The digital blocks were interfaced with the FPGA's on board modules and the discrete components. The signals that have been received from the transmitter were converted into a proper waveform and it can be viewed via external devices such as oscilloscope and Labview. The signals such as heartbeats or pulses can also be displayed on LCD. In conclusion, the IBC project presents medical health monitoring model that operates at the range of 21 MHz frequency and reduce the power consumption for a longer battery lifetime.

Signal measurement system for intra-body communication using optical isolation method

In this paper, we describe an induced signal measurement on the human body for developing a high-performance transceiver of an intra-body communication system. It is important to isolate awearable transceiver from an electrical instrument for precise measurement. We have developed a probe system using an optical isolation method including a laser diode, photo-diode, and optical fiber. The probe system can be successfully applied to the precise measurement of a receiving signal power at a wearable transceiver. We verify that the experimental results agree with the simulation results based on our previous channel model of intra-body communication.

Noise analysis for intra-body communication based on parasitic capacitance measurement

This paper describes noise transmission analysis for near-field intra-body communication systems based on parasitic capacitance measurement around the human body. Intra-body communication systems use the human body as the signal transmission medium. In communication systems of this type, the transmission line’s impedance balance between the signal line and the ground line is extremely degraded by human body contact. Such systems are affected by large common-mode noise from various kinds of electronic equipment in living spaces, such as lighting devices, air conditioners, liquid crystal televisions, and refrigerators. Impedance balance deteriorates as a result of adding parasitic impedance to the transmission lines. Changes in the impedance balance are estimated by measuring parasitic capacitance in the human body, transmission lines, electrodes, and floor ground. It was verified that impedance balance between the signal line and the ground line is related to the noise power of a near-field intra-body communication system. It was found that connecting a compensative electrode or a compact capacitor to a ground node is an effective way to improve impedance balance and reduce common-mode noise.

RETRACTED: Electro Optic Conversion Methods in Intra-Body Communication

Retracted paper: Galvanic coupling method has been observed to be the best method for data transmission in intra-body communication, which is proposed by Zimmerman in 1995. With the increasing transmission requirements and the development of optical fiber communication, a high speed data transmission system is required and it is possible to design an apparatus to realize the electro optic conversion. In this paper, the characteristics of the intra-body communication system are introduced. Principles and structures of the electro-optic modulation methods for intra-body communication are reviewed. Internal and external modulation methods are introduced and discussed. A system of the electro-optic and acousto-optic modulation are recommended for the intra-body communication system and discussed.

RETRACTED: Electro Optic Methods in Intra-Body Communication System

Retracted paper: Intra-body communication is proposed by Zimmerman in 1995 and the galvanic coupling has been observed to be the best method for data transmission. With the increasing transmission requirements and the development of optical fiber communication, a high speed system is possible to be designed based on the Electro optic methods. In this paper, the characteristics of the intra-body communication system are introduced. Principles and structures of optic modulation for intra-body communication are reviewed. Internal and external modulation methods are introduced and discussed. A system of the electro optic modulation is recommended and discussed.

Review of the Modeling, Simulation and Implement of Intra-body Communication

Abstract Intra-body communication (IBC) is a technology using the human body as a transmission medium for electrical signals. Compared with the short distance wireless communication technologies, it has several novel characteristics. The modeling, simulation and implement of intra-body communication are reviewed. Firstly, the transfer function of the galvanic coupling IBC was deduced, and the in vivo measurements results and the corresponding mathematical simulations results based on the proposed transfer function are discussed. Secondly, a finite-element method for modeling the whole human body is introduced, and simulations results of the galvanic coupling IBC based on the whole human body and the corresponding in vivo measurement results are discussed. Finally, the implement methods of the intra-body communication as well as a novel IBC system based on Mach–Zehnder EO modulator are introduced and analyzed, while some conclusions are achieved.

Study of Channel Characteristics for Galvanic-Type Intra-Body Communication Based on a Transfer Function from a Quasi-Static Field Model

Intra-Body Communication (IBC), which modulates ionic currents over the human body as the communication medium, offers a low power and reliable signal transmission method for information exchange across the body. This paper first briefly reviews the quasi-static electromagnetic (EM) field modeling for a galvanic-type IBC human limb operating below 1 MHz and obtains the corresponding transfer function with correction factor using minimum mean square error (MMSE) technique. Then, the IBC channel characteristics are studied through the comparison between theoretical calculations via this transfer function and experimental measurements in both frequency domain and time domain. High pass characteristics are obtained in the channel gain analysis versus different transmission distances. In addition, harmonic distortions are analyzed in both baseband and passband transmissions for square input waves. The experimental results are consistent with the calculation results from the transfer function with correction factor. Furthermore, we also explore both theoretical and simulation results for the bit-error-rate (BER) performance of several common modulation schemes in the IBC system with a carrier frequency of 500 kHz. It is found that the theoretical results are in good agreement with the simulation results.

Modeling and characterization of the electrostatic coupling intra-body communication based on Mach-Zehnder electro-optical modulation

The method of Mach-Zehnder electro-optical modulation is applied to Intra-Body Communication (IBC), where the modeling and characterization of this type of IBC are discussed. The mathematical model of the electrostatic coupling IBC based on Mach-Zehnder electro-optical modulation is developed. The main characteristics of this IBC form have been simulated within the frequency range of 200 kHz-40 MHz and compared to in-vivo measurements, with close agreements. Results show that the proposed method will help achieving good temperature characteristics, small size, and lower power consumption IBC system.

Study of Attenuation and Dispersion Through the Skin in Intrabody Communications Systems

Intrabody communication (IBC) is a technique that uses the human body as a transmission medium for electrical signals to connect wireless body sensors, e.g., in biomedical monitoring systems. In this paper, we propose a simple, but accurate propagation model through the skin based on a distributed-parameter circuit in order to obtain general expressions that could assist in the design of IBC systems. In addition, the model is based on the major electrophysiological properties of the skin. We have found the attenuation and dispersion parameters and they have been successfully compared with several published results, thus showing the tuning capability of the model to different experimental conditions. Finally, we have evaluated different digital modulation schemes in order to assess the tradeoffs between symbol rate, bit error rate, and distance between electrodes of the skin communication channel.

Measuring the Transmission Characteristic of the Human Body in an Electrostatic-Coupling Intra Body Communication System Using a Square Test Stimulus

This study employs a simple measurement methodology that is based on the de-convolution of a square test stimulus to measure the transmission characteristics of the human body channel in an electrostatic-coupling intra body communication system. A battery-powered square waveform generator was developed to mimic the electrostatic-coupling intra body communication system operating in the environment of the ground free. The measurement results are then confirmed using a reliable measuring method (single tone) and spectral analysis. The results demonstrate that the proposed measurement approach is valid for up to 32.5MHz, providing a data rate of over 16Mbps.

Analysis and Design of Wide-Band Digital Transmission in an Electrostatic-Coupling Intra-Body Communication System

SUMMARY This study develops a form of digital baseband Intra-Body communication for wideband transmission. A simplified circuit model of signal and noise is constructed to analyze the contribution of the high pass filter function of the electrostatic coupling Intra-Body communication system to wideband digital transmission in electrostatic coupling Intra-Body communication. A unit step function is presented to determine the maximum high pass 3 dB pole that can ensure favorable signal quality in a baseband Intra-Body communication system. Body noise is measured to estimate the range of the high pass 3 dB pole with good Signal to Noise Ratio. A 3.3 Volt battery-powered FPGA is experimentally implemented to confirm the feasibility of the wideband Intra-Body communication system. The experimental results indicate that the digital baseband Intra-Body communication system supports a data rate of more than 16MPS.