Realistic performance measurement for body-centric spatial modulation links

Spatial Modulation is a new transmission mode which increases spectral efficiency by employing information-driven transmit antenna selection. This performance is realized at a reduced hardware complexity and cost because only a single radio-frequency transmit chain is necessary. A measurement campaign is performed to assess the characteristics of spatial modulation over a body-centric communication channel, transmitting from a walking person with textile antennas integrated into the front and back sections of a garment, towards a base-station in realistic conditions. In the transmitted frames, additional spatial multiplexing as well as space-time coded data blocks are included. The off-body communication link is analyzed for line-of-sight as well as non line-of-sight radio wave propagation, comparing the characteristics of the different transmission modes under equal propagation conditions and for an equal channel capacity of 2 bit/s/Hz

Four-element ultrawideband textile cross array for dual-spatial and dual-polarization diversity

The emergence of miniaturized flexible electronics enables on-duty first responders to collect biometrical and environmental data through multiple on-body sensors, integrated into their clothing. However, gathering these life-saving data would be useless if they cannot set up reliable, preferable high-data-rate, wireless communication links between the sensors and a remote base station. Therefore, we have developed a four-element ultrawideband textile cross array that combines dual-spatial and dual-polarization diversity and is easily deployable in a first responder's garment. The impedance bandwidth of the array equals 1.43 GHz, while mutual coupling between its elements remains below -25 dB. For a maximal bit error rate of 1e-4, the array realizes a diversity gain of 24.81 dB. When applying adaptive subcarrier modulation, the mean throughput per orthogonal frequency division multiplexing (OFDM) subcarrier increases by an extra bit/symbol when comparing fourth- to second-order diversity

RSS-based secret key generation for indoor and outdoor WBANs using on-body sensor nodes

P

Improved reception of in-body signals by means of a wearable multi-antenna system

High data-rate wireless communication for in-body human implants is mainly performed in the 402-405 MHz Medical Implant Communication System band and the 2.45 GHz Industrial, Scientific and Medical band. The latter band offers larger bandwidth, enabling high-resolution live video transmission. Although in-body signal attenuation is larger, at least 29 dB more power may be transmitted in this band and the antenna efficiency for compact antennas at 2.45 GHz is also up to 10 times higher. Moreover, at the receive side, one can exploit the large surface provided by a garment by deploying multiple compact highly efficient wearable antennas, capturing the signals transmitted by the implant directly at the body surface, yielding stronger signals and reducing interference. In this paper, we implement a reliable 3.5 Mbps wearable textile multi-antenna system suitable for integration into a jacket worn by a patient, and evaluate its potential to improve the In-to-Out Body wireless link reliability by means of spatial receive diversity in a standardized measurement setup. We derive the optimal distribution and the minimum number of on-body antennas required to ensure signal levels that are large enough for real-time wireless endoscopy-capsule applications, at varying positions and orientations of the implant in the human body

Novel wearable antenna systems for high datarate mobile communication in healthcare

In critical healthcare applications, there is a need for reliable wideband mobile communication links, implemented by portable units with sufficient autonomy. We present the latest generation wearable antenna systems for invisible and comfortable integration in patients' or caregivers' garments. These active textile modules boast excellent performance and reliability, thanks to innovative antenna topologies, leveraged by the application of substrate integrated waveguide technology, pervasive integration of electronics and energy harvesters, and the application of multi-antenna processing techniques. Applications range from mobile communication links between caregivers and a coordination centre during interventions, over wireless sensor systems for patient monitoring, to relaying videos streams between a wireless endoscopy capsule and a remote control station

LTE as a potential standard for public safety indoor body-to-body networks

In this paper, a wideband indoor body-to-body communication channel is characterized and analyzed into detail by means of the RMS delay spread and the 50% correlation bandwidth. These body-to-body channel parameters are calculated based on high-resolution power delay profiles, directly provided by the Elektrobit channel sounder, and are further analyzed using a ray tracing algorithm. We have replicated a real-life rescue operation, performed by two firefighters as part of the Rapid Intervention Team searching for potential victims, operating at the same floor of an office block. Both firefighters, who were simultaneously moving around in the vicinity of each other, were equipped with two cavity-backed Substrate Integrated Waveguide textile antennas unobtrusively integrated in the front and back section of their jackets, allowing us to analyze four independent body-to-body links. Furthermore, we prove that the Long Term Evolution (LTE) and, by extension, the LTE -Device to Device (LTE-D2D) standard is compatible with this indoor body-to-body channel. This could provide high data rate indoor communication between rescuers, enabling multimedia broadcast and realtime communication of on-body sensor data in public safety networks

A wearable repeater relay system for interactive real-time wireless capsule endoscopy

Real-time wireless capsule endoscopy offers more flexibility and more precise screening options over commercially available passive endoscopy systems by allowing physicians to steer endoscopy capsules in real time. Yet, this requires reliable uninterrupted high frame-rate video streaming. In this contribution, we present a wearable repeater relay system that overcomes the impairments of the in-to-out body propagation channel and reliably relays implant data to a remote access point. The system consists of a set of wearable textile repeater nodes, exploiting receive diversity to provide a sufficiently large instantaneous carrier-to-noise ratio for live video streaming. Each wearable node, combining a dedicated receive antenna capturing the implant signal, an amplifier and an off-body transmit antenna, is fully implemented in textile materials, such that the comfort of the patient is not disturbed by the relay system. After outlining the design steps for the wearable relay node, in particular demonstrating stable robust antenna characteristics for the textile receive antenna oriented towards the body, we experimentally verify that a 6th-order diversity system provides the best compromise between user comfort and signal quality

Encrypted body-to-body wireless sensor node employing channel-state-based key generation

In this paper, experimental results are presented for an encrypted wireless link between two body-worn sensor nodes fully integrated onto textile antenna platforms. Wireless communication between two persons walking in an indoor environment occurs over a unique physical propagation channel. For the purpose of data encryption, channel measurements are performed at both sides of the link, providing highly correlated pseudo random number sequences, with envelope correlation coefficients always above 0.7. Signals captured by an eavesdropper are substantially decorrelated, with correlation coefficients always below 0.15, and are therefore not suitable for key extraction. The mutual information is also determined, providing extra insight into the key generating potential of the pseudo random sequences. Practical error free secret key generation on both sides of the link, with reconciliation by means of Hamming check bits, is performed successfully in all cases between legitimate parties. At the same time, an eavesdropper is unable to extract the secret key from measured signals, as confirmed by the key error rates, which are calculated for all possible signal combinations, resulting in a key error rate after reconciliation around 0.5 for most eavesdropper channels and remaining at least 0.3 in the worst-case scenario