Max O. Munoz

Numerical Analysis and Characterization of THz Propagation Channel for Body-Centric Nano-Communications

This paper presents the characteristics of electromagnetic waves propagating inside human body at Terahertz frequencies and an initial study of the system performance of nano-network. It has been observed that the path loss is not only the function of distance and frequency but also related to the dielectric loss of human tissues. Numerical results have been compared with analytical studies and a good match has been found which validates the proposed numerical model. Based on the calculation of path losses and noise level for THz wave propagation, the channel capacity is studied to give an insight of future nano-communications within the human body. Results show that at the distance of millimeters, the capacity can reach as high as 100 Terabits per second (Tbps) depending on the environment and exciting pulse types.

Exploring Physiological Parameters in Dynamic WBAN Channels

On-body radio propagation in the 2.45-GHz industrial-scientific-medical frequency band (2.40-2.48 GHz) was investigated during three different activities: jogging, rowing and cycling. Four different links were examined, from the waist to the wrist, ankle, chest and back; it was observed that the channel behavior could be related to the repetitive nature of the activities. Furthermore, combinations of the wrist, ankle, and chest channels could potentially be used to identify the activity, while the waist-back channel shows little variation between activities (roughly 2 dB, compared to 6-15 dB for the other links). The results also show that dynamic on-body radio channels contain rich biomechanical information, such as motion pattern, heartbeat, and breathing process. It is demonstrated that physiological and kinetic features can, therefore, be extracted through some known signal-processing techniques. For example, the repetitive nature of the activities introduces harmonics into the signal via fading, which correspond to the speed of motion. In addition, the mechanical motion of the torso during respiration and cardiac activity also introduce harmonics due to changes in the path loss, albeit with low magnitudes. The detection of such signals is discussed.

On-Body Channel Measurement Using Wireless Sensors

The on-body channel was characterised at various points on the human torso in an anechoic chamber using a pair of wireless sensor modules. The performance of wireless IEEE 802.15.4 sensor nodes operating in the 2.45 GHz ISM frequency band (2.40-2.4835 GHz) is presented over each of the 16 different channels. It is shown that the response at individual carrier frequencies is dependent not only on the initial antenna response, as determined by the on-body measurement in isolation, but also on the overall system performance. Measurement results are also compared with those from the conventional technique using a Vector Network Analyzer.

Wearable wireless sensors for healthcare applications

Recent activities at Queen Mary, University of London, relating to wearable wireless sensors research for healthcare applications are reviewed in this paper. The monitoring of blood glucose levels using non-invasive radio-based sensors is discussed. The analysis of on-body radio propagation channels is then presented, with an emphasis on variations related to activity.

Effects of non-flat interfaces in human skin tissues on the in-vivo Tera-Hertz communication channel

Abstract The influence of the interface type between the epidermis and dermis layers within the human skin tissue is investigated in this paper by introducing two models with different interfaces ( i.e. , 3-D sine and 3-D sinc function). By comparing the power loss of both models, it is evident that the common flat model is sufficient in case of electromagnetic communication links studies within the human tissue without the need of complicated detailed models. There is no significant difference between the power loss results of the flat model to the mean value of the power loss of the stratified model with sinc interface while the difference between the flat one from the stratified model with sine interface is less than 5 dB. However, the influence of the roughness can be presented by the deviation. From the numerical analysis, it is shown that for sine model it reaches almost 10 dB at a distance of 600 μ m , when the span changes. Meanwhile, the impact of the antenna location is demonstrated by placing the antennas (dipoles) in two different locations, which shows limited effects (the difference is less than 3 dB). Finally, the impact of the sweat duct is studied, showing its close relationship with the state of the sweat duct that the sweat-filled sweat duct working as PEC would reduce the power loss by almost 5 dB compared with the normal sweat duct without sweat.

Compressive sensing applied to fingerprint-based localisation

Accurate localisation has always been a hot topic for indoor environment. Recently, compressive sensing has been applied to fingerprinting based localisation and achieved good performance. This paper provides an overview of the state-of-the-art compressive sensing based indoor localisation techniques and an introduction to potential solutions to challenges faced by current systems. The main focus is on the drawbacks of the existing techniques and possible future development.

Millimeter-Wave Offset Fresnel Zone Plate Lenses Characterization

Fresnel Zone Plate Lenses (FZPLs) are transparent-opaque lenses that filter the desirable phase. The centred Fresnel lenses have a strong back radiation towards the feed. In order to solve this drawback, offset feeding or offset pointing lenses are used. In this work, both offset FZPLs are studied using an optical physics method and experimentally characterized in the millimeter band. Two prototypes have been manufactured and measured, presenting a narrow beamwidth. The characteristics of pointing of this beam are studied depending on the feed gain. This work shows the pointing characteristics of the lenses, simply moving the lens in a plane.

Physiological Features from an On-Body Radio Propagation Channel

A pair of low-power wireless sensor nodes, operating in the 2.45 GHz ISM band, are used to record the radio propagation of a particular on-body channel, the waist-chest channel. The recorded time-sampled radio link data is analysed in the frequency domain. It is shown that the wave propagation along the human bodys surface embeds not only the radio channel characteristics, but also physiological features.

A Compact and Low-Profile MIMO Antenna Using a Miniature Circular High-Impedance Surface for Wearable Applications

A new miniature circular high-impedance surface (HIS) is used to design a compact and low-profile multi-in multi-out (MIMO) antenna for wearable applications. The antenna is designed to operate from 2.4 to 2.49 GHz for wireless local area network application. By employing a pair of degenerated characteristic modes of a circular loop antenna, the MIMO antenna can achieve a good port-to-port isolation (>15 dB) without increasing its geometric size. A four-element HIS is chosen to match the antenna profile, and a 2 dBi antenna gain improvement is observed. The design was optimized considering the effect of packaging and then a prototype with the optimal parameters was fabricated and tested. Measurement results are in good agreement with simulation results. Furthermore, the loading effect due to lossy human tissue is also considered and the results show that the antenna has a robust performance against the human phantom and a low specific absorption rate can also be obtained.

Modelling of skin tissue for body-centric communications at terahertz frequencies

Summary form only given. In the recent years, there has been a significant amount of interest in body-centric applications. The in/on/off-body radio communications have been extensively studied and characterized at microwave frequencies for a wide range of applications, which include healthcare, military and lifestyle. The next generation of wearable technology will be operating at higher frequencies (millimeter wave and terahertz frequencies) and will offer a new set of applications not only for imaging, but also for sensing and communicating. The development of wearable terahertz-based devices that can automatically detect abnormal physiological parameters, such as skin cancer cells or track glucose changes, is a continuous challenge for research. It has been shown that the interconnection of nano-machines can support short-range communication between micro and nano-devices [1]. In order to understand and properly characterize the effects of electromagnetic wave propagation and the body, the design and simulation at terahertz frequencies will require the use of highly detailed 3D-tissue models which need to include the effects of the inhomogeneous anisotropic media, thus suitable radio propagation models can be derived. High-resolution and three-dimensional images of the human tissues can be acquired using optical coherence tomography which records the magnitude and relative location of the backscattered wave produced by microstructures of the tissue. In [2, 3], 3D images of the skin and finger-pad ridges were created from cross-sectional images depicting the different layers of the skin, namely dermis, epidermis, stratum corneum and the spiraling sweat ducts. Recently, the reported images were used in [4] to create a detailed simulation model of the skin and to understand the electromagnetic properties in the frequency range of 100-450 GHz. The results have shown that the morphological features of the skin and the structure of the sweat ducts play an important role in the reflectance spectrum. Feasibility studies for nano-communications and analytical models for path loss have been proposed in [5] and [6], respectively. Implanted miniature terahertz units could operate as sensing units (e.g., continuous glucose monitoring within the subcutaneous layer) and communicate with on-body devices; however, the radiation performance of such devices will significantly depend on the tissue models being used. In addition, tissue models considering effective dielectric properties would only deliver misleading results not only on the radiation performance of in-body antennas, but also on the design of future terahertz applications.