L. Van Biesen

Ultra-wideband channel model for communication around the human body

Using ultra-wideband (UWB) wireless sensors placed on a person to continuously monitor health information is a promising new application. However, there are currently no detailed models describing the UWB radio channel around the human body making it difficult to design a suitable communication system. To address this problem, we have measured radio propagation around the body in a typical indoor environment and incorporated these results into a simple model. We then implemented this model on a computer and compared experimental data with the simulation results. This paper proposes a simple statistical channel model and a practical implementation useful for evaluating UWB body area communication systems.

An ultra-wideband body area propagation channel Model-from statistics to implementation

Body worn wireless sensors for monitoring health information is a promising new application. In developing these sensors, a communication channel model is essential. However, there are currently few measurements or models describing propagation around the body. To address this problem, we have measured electromagnetic waves near the torso and derived relevant statistics. We find that components diffracting around the body are well modeled using correlated log normal variables, and a Nakagami-m distribution can be used to incorporate the influence of arm motions. We have implement this model and evaluated it in terms of important communication metrics. This paper describes body area propagation statistics and proposes a suitable computer model implementation.

Fingerprinting Localization in Wireless Networks Based on Received-Signal-Strength Measurements: A Case Study on WiMAX Networks

This paper considers the problem of fingerprinting localization in wireless networks based on received-signal-strength (RSS) observations. First, the performance of static localization using power maps (PMs) is improved with a new approach called the base-station-strict (BS-strict) methodology, which emphasizes the effect of BS identities in the classical fingerprinting. Second, dynamic motion models with and without road network information are used to further improve the accuracy via particle filters. The likelihood-calculation mechanism proposed for the particle filters is interpreted as a soft version (called BS-soft) of the BS-strict approach applied in the static case. The results of the proposed approaches are illustrated and compared with an example whose data were collected from a WiMAX network in a challenging urban area in the capitol city of Brussels, Belgium.

Characterization of the ultra wideband body area propagation channel

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. In developing these sensors, detailed knowledge of the communication channel is essential. However, there are currently very few measurements describing propagation around the body. To address this problem, we have measured electromagnetic waves traveling near the torso to derive a simple pathless law. The pathless law is then extended to include the influence of arm movements and a surrounding office environment. This paper describes our measurement campaign and the basic characteristics of the body area radio channel.

Ultra wide-band body area channel model

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. However, there are currently no models describing the radio channel around the human body making it difficult to design a suitable communication system. To address this problem, we have simulated electromagnetic wave propagation around the body and incorporated these results into a simple model. We then compared this model with measurements taken around the human torso and with previous studies in the literature. This paper proposes a simple statistical channel model useful for evaluating both UWB and (after resampling) narrow-band body area communication systems.

Estimation of the transfer function of a subscriber loop by means of a one-port scattering parameter measurement at the central office

In order to qualify a subscriber loop for xDSL transmission, the channel capacity has to be estimated, which depends on the transfer function of the network. A method is provided to estimate the transfer function of the subscriber loop only measuring the one-port scattering parameter at the central office. We consider three types of networks according to their topology: a single line, a homogeneous network with a bridged tap, and a cascade of two line sections. For each type of network a parametric model is derived of its one-port scattering parameter and transfer function based on the physical line model VUB0. The model for the scattering parameter is used to identify the network based on the corresponding measurements by means of a maximum-likelihood estimator. The estimated parameters are substituted in the transfer function model, which is needed for the capacity estimation. The proposed models and estimators are validated by measurements and simulations. For the measurements, which were performed with a network analyzer, three types of twisted-pair cables were used: British Telecom (BT), Deutsch Telekom (FT), and Belgacom.

Identification of transfer functions with time delay and its application to cable fault location

A Gaussian frequency-domain maximum likelihood estimator (MLE) to estimate the transfer function of linear continuous-time systems with time delay is presented. The stochastic framework is an errors-in-variables model, which means that the input as well as the output of the system is disturbed with noise. The estimator is applied to a practical measurement problem, namely the estimation of the location of discontinuities, e.g. faults in electrical cables from a reflectogram. Experimental results for coaxial lines show that it is possible to identify simultaneously the location of the discontinuity and a rational approximation of the generator mismatch, the fault impedance, and some of the cable parameters. >

Robust Tracking in Cellular Networks Using HMM Filters and Cell-ID Measurements

A localization algorithm based on cell identification (Cell-ID) information is proposed. Instead of building the localization decisions only on the serving base station, all the detected Cell-IDs (serving or nonserving) by the mobile station are utilized. The statistical modeling of user motion and the measurements are done via a hidden Markov model (HMM), and the localization decisions are made with maximum a posteriori estimation criterion using the posterior probabilities from an HMM filter. The results are observed and compared with standard alternatives on an example whose data were collected from a worldwide interoperability for microwave access network in a challenging urban area in the Brussels capitol city.

Preprocessing of Signals for Single-Ended Subscriber Line Testing

A preprocessing algorithm is proposed to visualize the time-domain one-port scattering parameter of a subscriber line measured at the Central Office. To overcome the high line attenuation and the mismatch between the line and the measurement instrument, a preprocessing algorithm is developed to obtain numerically the impulse response of the one-port scattering parameter. The algorithm will search for a quasi-optimal base impedance for the scattering parameter; then, it will de-noise and de-alias the impulse response and will provide an estimate for the first meaningful significant reflection

Identification of parametric models for ultrasonic wave propagation in the presence of absorption and dispersion

Acoustic wave propagation in an absorptive and dispersive medium is usually described using models derived from a nearly local form of the Kramers-Kronig relationship, e.g., Q- and relaxation models. A modeling approach based on rational transfer function models for the generalized Hookes law is presented. The assumptions and restrictions of models based on the nearly local absorption-dispersion relations and rational transfer function models are discussed. Using identification techniques, it is experimentally shown that the rational transfer function models explain the ultrasonic wave propagation in an absorptive-dispersive medium much better than the classical Q-models.<<ETX>>