Conference paper. This is a preview of subscription content, log in to check access. Patel, M. Cao, H. Chen, M. Springer publication Google Scholar. Pantelopoulos, A.
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IEEE Std Lee, C. Bluespec Inc. Personalised recommendations. Cite paper How to cite? On-body and off-body preliminary channel study is reported in [ 17 ]. Channel characteristics reported in [ 18 — 20 ] are based on measurements performed in anechoic chamber. Around-body channel models reported in [ 21 — 23 ] are based on measurement performed on human torso. Taparugssanagorn et al.
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However, all the parameters of reported path loss models for on-body UWB channel in the literature represent the frequency averaged path loss of the entire frequency band of corresponding measurement. Furthermore, the permittivity and the conductivity of human body are frequency dependent. Therefore, it is expected that the characteristic parameters of path loss models might be dependent on the frequency band of applied radio wave.
In these circumstances, the frequency averaged path loss derived for the entire UWB frequency band may not reflects the actual channel characteristics on the specific operating frequency band. This will introduce non-reliability in the system. In this Letter, we have experimentally determined the path loss parameters of on-body UWB channel for each frequency sub band standardised in [ 3 ].
Variation of path loss parameter values at each sub band in line-of-sight LOS and non-line-of-sight NLOS channel conditions are examined.
The variation of parameter values with the size of human body is also analysed and reported. Furthermore, the variations of parameter values at each sub band with the surrounding environments are analysed based on measurement data. The objective of this study is the experimental determination of path loss model parameters for on-body UWB channel, which will be more appropriate for the specific frequency band of interest defined in the IEEE The remaining of this Letter is organised as follows: the Section 2 provide the description of measurement setup, procedures of measurement and different channel scenarios.
The description of the antenna characteristics on the human body is also described in this section.
Security in Low Energy Body Area Networks for Healthcare
Section 3 provides the data analysis and corresponding results. The conclusion of this Letter is drawn in Section 4. The VNA was controlled from a computer connected to it through local area network. The VNA was configured to S21 parameter measurement setup with the radio channel as device under test. The frequency bandwidth B used in our measurement is 7. The resultant maximum detectable delay from 1 in our measurement is ns.
The time resolution of the measurement setup is given by the reciprocal of the frequency bandwidth that is ps in this configuration. Channel measurements are performed in a typical laboratory environment. The laboratory is consisting of different laboratory instruments, computers, workbenches, bookshelves, tables, chairs etc. The floor and roof of the laboratory is made of concrete with a ceiling of plasterboard.
Comprehensive analysis of the authentication methods in wireless body area networks
Sidewalls are made of concrete with two-third of its height covered with glass windows having aluminium frame. Total six set of measurement campaigns are carried out for the determination of path loss in LOS and NLOS scenarios on the body of three persons having different size to get the trend of path loss parameters with the size of body. The circumference of the thin, normal and fat persons at waist are 71, 81, 81 cm, respectively, while the corresponding circumference at chest are 79, 91 and 85 cm, respectively.
In LOS scenario the transmit and receive both antennas are kept on the front side of the body whereas in NLOS scenario the transmit antenna was in the front side and the receive antenna was placed on the rare surface of the body. The placements of antennas are shown in Fig. Separation between two consecutive receiver antenna positions was maintained at 5 cm, which is sufficient to get detail variation of path loss information. In all measurements, both the antennas are separated from the body by 10 mm for optimum coupling of the antenna and the body [ 26 ].
The person on whom the measurements were performed was asked to stand straight without any movement during the measurement period at a relatively free space of the room. In all channel links total 10 consecutive channel frequency responses are averaged to remove random noises and saved in computer for further analysis.
Numbers of averaged channel responses recorded from thin, normal and fat person in LOS are , , , respectively, and the same in NLOS are , , , respectively. To study the variation of path loss with surrounding environments measurements are performed on the body of same person at five different places in the laboratory.
Different places are selected based on the number of scattered objects and their arrangements near the body. The antenna required for WBAN application should be compact in size, lightweight, highly efficient in radio transmission, robust, and inexpensive. Tremendous research works are going on all over the globe for development of appropriate wearable antenna. Textile antennas are one type of antenna used in body worn systems. It is observed that the characteristics of an antenna significantly changes when placed on the body.
The frequency of operation, impedance matching and radiation pattern of the antennas having ground plane, experiences less effect when placed on body [ 27 ]. Similarly, the front—back ratio of antennas having ground plane have no significant difference when placed in free space and on the body [ 27 ]. The measured and simulated return losses S11 of the antennas are shown in Fig. It is observed that the placement of antenna on human body affects the reflection efficiency of the antenna.
An Ultra-Wideband Baseband Transmitter Design for Wireless Body Area Network | SpringerLink
To test the coupling of the antenna with the body, the return loss of the antenna at different position of the body was investigated. Due to the change in composition of different part of human body, the return loss of the antenna is different at different position on the body.
To get an optimum coupling of the antenna with the body a 10 mm thick dielectric material was attached at the rare side of the antennas. The dielectric used in our measurements is hard thermocol. Similar method was adopted in most of the literature whereas in [ 28 ] a cardboard of 5 mm thick was used as dielectric. The path loss model is the preliminary requirement for wireless communication system designers to get the knowledge of attenuation of transmitted power as it propagates away from the transmitter.
The path loss, at a distance can be calculated by averaging the squared term of the channel frequency response over the number of frequency sweep points N as. The distance dependent path loss may be expressed as.
In this measurement, the channel frequency responses are recorded for entire UWB frequency band as stated in Section 2. The frequency response for each sub bands defined in [ 3 ] have been extracted in Matlab and corresponding frequency averaged path loss for particular bands are calculated using 2.
It is observed that the path loss parameters frequency dependent varies in each frequency band. Linear regression lines by least square means are fitted to the measured path loss for obtaining path loss parameters.tax-marusa.com/order/qekyvodom/application-galaxy-note-8.php
Path loss variation of on-body UWB channel in the frequency bands of IEEE 802.15.6 standard
To study the dependency of path loss parameters with the surrounding environment, total five set of measurements are conducted in the same measurement room in LOS condition. The subject on whom the antennas were attached was asked to stand in the same way as in the previous measurement campaigns at five different places in the room. The different places are chosen based on number of scatters near the body and their geometrical arrangement.
Deviations of measured path loss from the estimated path loss are calculated for all frequency bands for all individual for both LOS and NLOS channel conditions.
The Kolmogorov Smirnov K—S test was performed to find the statistical distribution of fading term. The candidate distributions considered in K—S test are normal, lognormal, Weibul, Rayleigh and Nakagami. The parameters of the specific distributions are estimated from the measured values using maximum likelihood estimation technique. Random numbers of sufficient length are generated for a specific distribution with the estimated parameters for the distribution and K—S test was performed with the measured data.
Test was performed for times for each distributions and average passing rate of the test is observed for all channel. From the observation, it is found that the lognormal distribution gives the highest passed distribution in all channels. The parameters of the lognormal distribution is determined for all channels and reported. It is found that the mean of the lognormal distribution is zero in all observation while the standard deviations vary with the body size and channel conditions.
From the observation, it is found that in most of the channels the standard deviations of shadow fading decreases in NLOS than in LOS conditions. High value of standard deviation is found on the thin person. Variations of standard deviations are also observed for the different places in the room.
To the best of our knowledge, no one has analysed the channels in the frequency bands as defined in the IEEE The signals transmitted from the transmit antenna is significantly affected by the channel. Thus, to recover the signal at receiver it is necessary to undo the effect of channel on the transmitted signal.
Path loss is one of the important characteristics of wireless channel. The system designers for WBAN communication require the detail knowledge of the channel for efficient realisation of the system. They require the channel information for investigation of the performance of different transmission schemes as well as for the development of efficient algorithms for WBAN communication.
Variations of path loss model parameters in the frequency bands of IEEE Variation of model parameters with the surrounding environment is also observed.