On-body Communication Research Articles

Switchable on/off-body communication at 2.45 GHz using textile microstrip patch antenna on stripline

The potential of employing textile materials to realise a switchable on- and off-body communication system at 2.45 GHz is demonstrated. It is based on an aperture-coupled rectangular textile microstrip patch antenna mounted on textile stripline with a pin diode switching network. Simulations and measurements are presented which show good agreement. On-body communication through a 600 mm-long stripline shows a transmission loss of around −5 dB. Off-body communication via the patch antenna shows a bandwidth from 2.4–2.48 GHz with a boresight gain of 1.48 dBi.

Small Multi-Band Antenna with Tuning Function for Body-Centric Wireless Communications

The research on body-centric wireless communications (BCWCs) is becoming very hot because of numerous applications, especially the application of E-health systems. Therefore, a small multi-band and low-profile planar inverted-F antenna (PIFA) with tuning function is presented for BCWCs in this paper. In order to achieve multi-band operation, there are two branches in the antenna: the longer branch low frequency band (950-956MHz), and the shorter branch with a varactor diode embedded for high frequency bands. By supplying different DC voltages, the capacitance of the varactor diode varies, so the resonant frequency can be tuned without changing the dimension of the antenna. While the bias is set at 6V and 14V, WiMAX and ISM bands can be covered, respectively. From the radiation patterns, at 950MHz, the proposed antenna is suitable for on-body communications, and in WiMAX and ISM bands, they are suitable for both on-body and off-body communications.

Diversity antenna combining slot-loop DRA for BAN applications

A compact dual pattern diversity antenna combining a slot loop and a dielectric resonator antenna (DRA) is presented for body area network (BAN) applications at 2.4 GHz. A common bandwidth of 1.5% is obtained with an isolation of −12dB. The slot loop provides slightly asymmetric broadside radiation patterns while purely symmetric end-fire type radiation patterns are obtained with the DRA. The diversity gain performance of the antenna has been tested in receiving mode for three different on-body communication channels.

PERFORMANCE EVALUATION OF UWB ON-BODY COMMUNICATION UNDER WIMAX OFF-BODY EMI EXISTENCE

A study of UWB on-body communication system performance, with the WiMax ofi-body electromagnetic interference (EMI) existence, is presented. Firstly, a compact UWB antenna with good on-body performance is verifled and chosen as our reference antenna. Using this realistic antenna, channel transfer function (CTF) of UWB on-body channel in an indoor room is investigated by measurements. Based on the measured data, the parameters of its pathloss model and its power delay proflle (PDP) model are extracted respectively. Secondly, a new body channel communication system model, composed of the on-body and ofi-body dual-link channel, together with UWB and WiMax signal models are presented. Finally, UWB on-body communication performances under difierent WiMax ofi-body EMI levels are studied by simulation. Simulated results show that this on-body system performance is quite limited and easily afiected by the ofi-body WiMax EMI. It is pointed out that the existing UWB on-body communication abilities should be greatly improved when WiMax ofi-body EMI signals are considered.

Diversity Measurements for On-Body Channels Using a Tri-Polarization Antenna at 2.45 GHz

Characteristics and diversity performance for on-body communication systems using a tri-polarization antenna are investigated based on measurements at 2.45 GHz. A disk-loaded monopole has been used as a transmitter, and a low-profile planar tri-polarization antenna as a three-branch receiver. Measurements were conducted for six typical on-body scenarios, where standing and sitting postures are considered. Envelope correlation and cross-polar discrimination (XPD) are calculated from measurement data. The tri-polarization diversity performance is evaluated by diversity gain, when different signal combing techniques are employed. Diversity gain is high for the non-line-of-sight scenarios and increases with increasing mobility. Tri-polarization diversity outperforms dual-polarization diversity in terms of up to 16.33 dB higher path gain due to the full utilization of polarization resource of electromagnetic wave and the avoidance of polarization mismatch for the dynamic on-body channels.

Wearable Endfire Textile Antenna for On-Body Communications at 60 GHz

A textile endfire antenna operating in the 60-GHz band is proposed for wireless body area networks (BANs). The permittivity of the textile substrate has been accurately characterized, and the Yagi-Uda antenna has been fabricated using an ad hoc manufacturing process. Its performance in terms of reflection coefficient, radiation pattern, gain, and efficiency has been studied in free space and on a tissue-equivalent phantom representing the human body. It is shown that the antenna is matched in the 57-64-GHz band. Its measured on-body efficiency and maximum gain equal 48.0% and 11.9 dBi, respectively. To our best knowledge, this is the first textile antenna for on-body wireless communications reported at millimeter waves.

Special issue on "Towards the connected body: advances in body communications"

Body area networks (BANs) are quickly becoming a key technology for wireless communications. They consist of body-worn or implanted sensors that wirelessly communicate, leading either to inor on-body communications between sensors, or to off-body communications with devices located in the close vicinity. BAN’s potential applications include, among others, m-health information systems collecting vital parameters in real-time, high-speed connections over the body surface for multimedia transfers or human body interactions with its environment for augmented reality devices. Several technologies are currently under development in order to enable these communications, either narrowband (including RFID technologies), or ultra-wideband (IR-UWB). The latter could be advantageously coupled with positioning algorithms for simultaneous body motion capture. However, in practice, numerous challenges still need to be tackled in order to make BANs viable. The sensor’s autonomy, size, and cost are critical parameters which can only be optimized by adopting an interdisciplinary approach, where the propagation phenomena, the coding or relaying strategies, the MAC protocols, and the network topology are strongly interrelated. The coexistence issue with other networks also seems to be crucial, especially in the hospital environment. This special issue goes through all the layers of telecommunication systems dedicated to body communications, from channel models for onor off-body communications, to global telecare systems based on Bluetooth, smartphones, and GPS. The article “Experimental characterization of an UWB channel for body area networks” by P. Chiang et al. presents UWB channel measurement campaigns, for both onand off-body communications. The measured path loss and multipath analysis suggest that a LOS UWB channel is excellent for low-power, high-data-rate transmission, while NLOS and on-body channels need to be reconfigured to operate at a lower data rate due to high path loss. The article “An analytical modeling of polarized timevariant on-body propagation channels with dynamic body scattering” by L. Liu et al. presents an analytical model of the on-body scattering and propagation on the trunk of a walking person. The results act as an example of how analytical models can provide efficient yet precise predictions of time-variant, on-body propagation to understand the mechanisms underlying the propagation characteristics. The article “In-body Path Loss Models for Implants in Heterogeneous Human Tissues using Implantable Slot Dipole Conformal Flexible Antennas” by F. Axisa et al. discusses the path loss of implant communication channel for a 6-year male child with slot dipole conformal antennas at 2.45 GHz via 3D electromagnetic simulations. The article proves that exponential attenuation model is well applicable to the heterogeneous model as well, but homogeneous phantom may underestimate the pathloss compared with more realistic heterogeneous phantom. The article “Secure Precise Clock Synchronization for Interconnected Body Area Networks” by D. Sanchez et al. tackles secure time synchronization in BANs. A combination of secure pairwise synchronization, rate adaptive time synchronization, and μTESLA is used to achieve energy efficient, accurate, and secure synchronization between BAN nodes. In “Emergency Handling for MAC protocol in Human Body Communication (HBC-MAC)” by O. Buyanjargal et al., a specific emergency handling operation is proposed for BAN’s MAC protocol in order to meet the emergency requirements for BAN without wasteful dedicated slots for emergency in each superframe. The article “Impact of the Environment and the Topology on the Performance of Hierarchical Body Area Networks” by J.-M. Dricot et al. addresses the throughput and energy consumption of various BAN topologies * Correspondence: pdedonck@ulb.ac.be Universite libre de Bruxelles, Bruxelles, Belgium Full list of author information is available at the end of the article De Doncker et al. EURASIP Journal on Wireless Communications and Networking 2011, 2011:203 http://jwcn.eurasipjournals.com/content/2011/1/203

On-Body Transmission at 5.2 GHz: Simulations Using FDTD With a Time Domain Huygens' Technique

On-body communications systems are heavily influenced by the effects of the human body and cannot be analyzed without taking these into account. This, however, leads to a large problem which is a challenge to model. In this paper a transmission scenario is modeled which includes transmit and receive cavity backed slot (CBS) antennas on the body of a male adult. The slots are backed with cavities in order to get unidirectional radiation patterns and decrease the near field body interaction of the slots. The scenario is simulated with finite difference time domain (FDTD) method in combination with a time domain Huygens' (TDH) technique in order to reduce the computational load. A cylindrical numerical phantom including 15 different tissue types is modeled to represent the upper body of a male. The predicted transmission coefficient, return loss and radiation patterns obtained using the TDH method are shown to be in agreement with the resource intensive direct FDTD approach but are obtained in approximately 30% of the time.

A Compact UWB Antenna for On-Body Applications

A new compact planar ultrawideband (UWB) antenna designed for on-body communications is presented. The antenna is characterized in free space, on a homogeneous phantom modeling a human arm, and on a realistic high-resolution whole-body voxel model. In all configurations it demonstrates very satisfactory features for on-body propagation. The results are presented in terms of return loss, radiation pattern, efficiency, and E-field distribution. The antenna shows very good performance within the 3-11.2 GHz range, and therefore it might be used successfully for the 3.1-10.6 GHz IR-UWB systems. The simulation results for the return loss and radiation patterns are in good agreement with measurements. Finally, a time-domain analysis over the whole-body voxel model is performed for impulse radio applications, and transmission scenarios with several antennas placed on the body are analyzed and compared.

An Improved Antenna Mounting for Ultra-Wideband On-Body Communications and Channel Characterization

The electromagnetic coupling of antennas with the human body is a well-known, but often neglected, problem in body area network (BAN) communications. The resulting distortion of the antenna's free-space characteristics may, in turn, demand more complex terminals to cope with the different conditions encountered as antennas are mounted on different parts of the body and/or varying separations from the skin. Therefore, in this paper, we propose a mounting method to provide a more stable response and to reduce the antenna's coupling to the body for ultra-wideband (UWB) BAN applications. The proposed mounting method is evaluated on two UWB BAN antennas, characterizing the antennas coupling with the body by analyzing variations in the antennas reflection coefficient between 4-9 GHz, when mounted at different distances from the skin and at different locations on the body. The modified mounting method was found to increase the correlation coefficient between the antenna's reflection coefficient when in free space and mounted using 5 mm of spacer, for the two antennas, from 0.22 and 0.13, to 0.66 and 0.90. The free-space characteristics of the modified antennas are also tested, showing a reduction of up to 4.7 dB of radiated power into the body.

Simulation and Measurement of Dynamic On-Body Communication Channels

A study is presented of wireless on-body communication links, with the body in motion. This paper compares simulations and measurements of the path gain (PG) on moving male and female bodies. Simulations using avatars derived from an animation software have been performed at 2.45 GHz. Male and female avatars walking and a male rising from a chair have been simulated and the results are compared with measurements carried out in an anechoic chamber. The results show that good agreement between simulation and measurement of slow fading features can be achieved for a reasonable computational effort.

Polarisation diversity performance for on-body communication applications

This study reports on the measured polarisation diversity performance of on-body communication channels at 2.45 GHz. To perform the measurements, a new dual-polarised antenna was designed and fabricated. The antenna provides polarisations both normal and parallel to the body surface. Measurements were carried out with a subject wearing this antenna and moving in a laboratory environment. Diversity gains were then calculated for both the polarisation states based on the measured data. Reasonable gains of around 5 dB were achieved for the dynamic on-body channels, while static channels show little improvement.

Transmit–receive diversity for 2×2 multiple-input multiple-output channel in body area networks

Body-centric communication is an important part of 4G personal communication systems. The principal goal of this study is to investigate the effect of multiple-input multiple-output (MIMO)-diversity for on-body communication channels. The MIMO-diversity gain (DG) is calculated by plotting the cumulative distribution functions. The DG values for 2×2 MIMO system are calculated, which are equivalent to the DGs achievable by an equivalent diversity system of order 4. The power imbalance and the correlation among the subchannels is also presented and a comparison of 2×2, 2×1 and 1×2 systems is done on the basis of diversity performance.

Characterization of MB-OFDM-Based Ultrawideband Systems for Body-Centric Wireless Communications

This letter aims to investigate the optimum locations for ultrawideband (UWB) nodes placement on the body for reliable and power-efficient body-centric wireless communications. System-level modeling is analytically and numerically performed on the basis of multiband orthogonal frequency division multiplexed (MB-OFDM) system. System performance is evaluated for different parts of the body based on real-time measurements. Results and analyses, based on signal-to-noise ratio (SNR) and bit error rate (BER), demonstrated that BER is less than or equal to 0.1% for 96.43% of lower-body locations (for on-body communications) and 83.68% of the human trunk ones (for off-body communications), respectively, with low power requirements.

Path gain models for on-body communication systems at 2.4 and 5.8 GHz

In this paper, a couple of path gain models for on-body communication systems are analyzed and compared. The study is focused on the characterization of the propagation channel between two wearable devices placed on a human body, and operating at 2.4 and 5.8 GHz. Wearable wireless low-cost commercial modules and low-profile annular ring slot antennas were used, and measurements were performed for different radio links on a human body. Measurement results have been compared with CST Microwave Studio simulations by resorting to simplified body models like flat, cylindrical, spherical, and ellipsoidal canonical geometries. Characteristic parameters appearing in the propagation models have been calculated for the analyzed on-body channels and summarized in a concluding table.

Performance of Ultra Wideband On-Body Communication Based on Statistical Channel Model

Ultra wideband (UWB) on-body communication is attracting much attention in biomedical applications. In this paper, the performance of UWB on-body communication is investigated based on a statistically extracted on-body channel model, which provides detailed characteristics of the multi-path-affected channel with an emphasis on various body postures or body movement. The possible data rate, the possible communication distance, as well as the bit error rate (BER) performance are clarified via computer simulation. It is found that the conventional correlation receiver is incompetent in the multi-path-affected on-body channel, while the RAKE receiver outperforms the conventional correlation receiver at a cost of structure complexity. Different RAKE receiver structures are compared to show the improvement of the BER performance.

Investigation of on-body Bluetooth transmission

The development of communication devices, especially cellular phones has necessitated the advances of several portable and wearable technologies, such as Bluetooth headsets within wireless body area networks (WBAN). Such wearable devices use the human body as a communication channel; hence, a comprehensive understanding of the transmission mechanism between such devices is vital. This study presents an investigative study to characterise the electromagnetic transmission between a body-mounted Bluetooth headset antenna and a mobile phone handset antenna. Commercially used antennas have been used to study various factors affecting on-body communication links including handset-to-body separation and presence of blocking objects. A thorough numerical modelling, supported by the measurements, has been carried out to demonstrate the importance of surface waves in the on-body Bluetooth transmission.

Characterization of On-Body Communication Channel and Energy Efficient Topology Design for Wireless Body Area Networks

Wireless body area networks (WBANs) offer many promising new applications in the area of remote health monitoring. An important element in the development of a WBAN is the characterization of the physical layer of the network, including an estimation of the delay spread and the path loss between two nodes on the body. This paper discusses the propagation channel between two half-wavelength dipoles at 2.45 GHz, placed near a human body and presents an application for cross-layer design in order to optimize the energy consumption of different topologies. Propagation measurements are performed on real humans in a multipath environment, considering different parts of the body separately. In addition, path loss has been numerically investigated with an anatomically correct model of the human body in free space using a 3-D electromagnetic solver. Path loss parameters and time-domain channel characteristics are extracted from the measurement and simulation data. A semi-empirical path loss model is presented for an antenna height above the body of 5 mm and antenna separations from 5 cm up to 40 cm. A time-domain analysis is performed and models are presented for the mean excess delay and the delay spread. As a cross-layer application, the proposed path loss models are used to evaluate the energy efficiency of single-hop and multihop network topologies.

Onbody Diversity and Angle-of-Arrival Measurement Using a Pattern Switching Antenna

Diversity is one of the methods to overcome the multipath effect in the mobile environment. A pattern diversity antenna with four beams was used to investigate the diversity performance in the onbody environment. A switched diversity combining method-switch-and-stay strategy-was used to analyze the data. Finding an angle of arrival (AoA) of different multipath components is very useful since it allows optimization of the base-station antenna radiation patterns and can be used to locate and track the handsets that operate in a particular cell. Similarly, in onbody communications, knowing the AoA enables determining the position of the antennas relative to each other and supports the design of antennas with optimized radiation patterns. Diversity and AoA measurements have been performed for five randomly movements body channels. In diversity measurements, the antenna beams are switched quickly considerably faster than the body movements. The results show that significanct gains are achieved for non-line-of-sight channels and no gain is obtained for the LOS channel since the signal is received by the same beam during the measurement. During AoA measurements, the 2-D process is chosen in which the angles are in a 2-D plane around the ground plane of the antenna. The main propagation paths of the transmitted signal are limited to a limited interval of the AoA range. These AoA estimates for onbody propagation channels can be used for designing better fixed beam and pattern diversity antennas.

Characteristics of Cavity Slot Antenna for Body-Area Networks

Antennas and the propagation characteristics for body-area networks have become an active area of research. In this paper, a cavity slot antenna is proposed for onbody communications at 2.45 GHz. First, the antenna characteristics (input impedance, radiation pattern, and efficiency) are calculated by the finite-difference time-domain method. The results show that the proposed antenna has a relatively high efficiency of more than 50% even in the vicinity of the human body. Next, the onbody radio wave-propagation characteristics are investigated through numerical simulation and experimental measurements of the electric-field distributions around a phantom with a simplified shape of a human arm. Both sets of results are then compared and discussed. Finally, good agreement between the measured and the calculated results is confirmed.