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This paper describes an extensive propagation channel measurement campaign in a warehouse environment for line-of-sight (LOS) and nonline-of-sight (NLOS) scenarios. The measurement setup employs a vector network analyzer operating in the 2–8-GHz frequency band combined with an $8 \times 8$ virtual multiple-input multiple-output (MIMO) antenna array. We develop a comprehensive statistical propagation channel model based on high-resolution extraction of multipath components and subsequent spatiotemporal clustering analysis. The intracluster direction of departure (DoD), direction of arrival (DoA), and the time of arrival (ToA) are independent, both for the LOS and NLOS scenarios. The intracluster DoD and DoA can be approximated by the Laplace distribution, and the intracluster ToA can be approximated by an exponential mixture distribution. The intercluster analysis, however, shows a dependency between the cluster DoD, DoA, and ToA. To capture this dependency, we separately model the clusters caused by single and multiple bounce scattering along the aisles in the warehouse. The intercluster DoD distribution follows a Laplace distribution, while the cluster DoA conditioned on the DoD is approximated by a Gaussian mixture distribution. The model was validated using the capacity and delay-spread values. [ABSTRACT FROM AUTHOR]

Ultrawideband (UWB) radio technology for wireless implants has gained significant attention. UWB enables the fabrication of faster and smaller transceivers with ultralow power consumption, which may be integrated into more sophisticated implantable biomedical sensors and actuators. Nevertheless, the large path loss suffered by UWB signals propagating through inhomogeneous layers of biological tissues is a major hindering factor. For the optimal design of implantable transceivers, the accurate characterization of the UWB radio propagation in living biological tissues is indispensable. Channel measurements in phantoms and numerical simulations with digital anatomical models provide good initial insight into the expected path loss in complex propagation media like the human body, but they often fail to capture the effects of blood circulation, respiration, and temperature gradients of a living subject. Therefore, we performed UWB channel measurements within 1–6 GHz on two living porcine subjects because of the anatomical resemblance with an average human torso. We present for the first time, a path loss model derived from these in vivo measurements, which includes the frequency-dependent attenuation. The use of multiple on-body receiving antennas to combat the high propagation losses in implant radio channels was also investigated. [ABSTRACT FROM PUBLISHER]

Radio propagation in confined spaces is consequent upon reflections by the boundaries. In such cases, the relative position and polarization of antennas becomes important. This paper investigates the effect of antenna position and polarization on ultra-wideband radio propagation in underground mines and tunnels. Analysis is based on channel measurements, over 2.4 to 4 GHz frequency band, in three tunnels of varying cross-sectional dimensions and lengths. Effects of mounting antennas on ceiling versus walls and horizontal versus vertical polarization are compared in terms of path loss and time dispersion. Results show that average path loss is more sensitive to antenna position and polarization, than is time dispersion. The effect of polarization is found to be dependent upon antenna position. Horizontal polarization results in less average path loss when the antennas are mounted close to the ceiling, whereas vertical polarization results in less average loss when mounted close to a side wall. It is demonstrated that carefully considering antenna position and polarization can result in more efficient and cost-effective deployment of UWB systems in underground environments. [ABSTRACT FROM PUBLISHER]

An experimental study of the time reversal (TR) technique is presented in a single-input–single-output configuration over the frequency range of 2–12 GHz. A special emphasis of this work is to investigate and compare impulse response (IR) and TR characteristics for omnidirectional biconical and directional spiral antennas over realistic indoor ultrawideband (UWB) channels in both line-of-sight (LOS) and non-line-of-sight (NLOS) environments. We discuss the effects of channel multipath dispersion and antenna frequency-dependant delay distortions on the received responses in both time and frequency domains. The effectiveness of TR for waveform compression is characterized by computing root mean square delay spread and peak-to-average power ratio. Our study suggests that the effectiveness of time reversal is subject to a tradeoff between competing effects—namely, compensation of spectral phase variation (which leads to compression) and aggravation of spectral amplitude structure (which opposes compression). Although TR is a powerful technique for compensation of phase distortions associated with broadband frequency-independent antennas (as shown in LOS experiments with spiral antennas), it shows only modest performance in compressing time spread associated with multipath delays. [ABSTRACT FROM PUBLISHER]

In ultra-wideband (UWB) wireless propagation channels, each multipath component (MPC) can exhibit delay dispersion or, equivalently, frequency dependence; even more, this dispersion can be different for different MPCs. While this effect is understood to have important implications for UWB system design, extraction of the frequency-dependence parameters from measurements has been lacking. This paper will provide both the theoretical tools for the parameter extraction, and provide experimental results of such parameters in UWB indoor channels. We first develop a method that extracts a single MPC. Based on the image principle, the method identifies locations and intensity of radio sources including both original and image sources (corresponding to MPCs) by a distributed antenna array. We show that the method provides spatial resolution better than 0.5 m and is robust against possible measurement errors. Having applied the method to the measured channels in indoor line-of-sight scenarios, we track the detected image sources over (partially overlapping) frequency subbands to obtain frequency dependent properties of their intensity and location. The variation of the source intensity over the frequency was found to be significant. Furthermore, the locations of the image sources can vary as the frequency changes. Comparison of the results with models that do not describe varying per-path frequency dependence revealed noticeable difference in the shape of the CIRs, and as a result, in the delay spread and the number of significant delay bins for Rake reception. [ABSTRACT FROM PUBLISHER]

A three-dimensional convex polyhedral beam-tracing method for modeling ultrawideband indoor radio channels is presented.The model enables a fast and unambiguous generation of all propagation paths between the transmitter and the receiver over an 850-MHz bandwidth. To validate the model, its results are compared with measurements. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:904-909, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26670 [ABSTRACT FROM AUTHOR]

A discrete finite time domain pulse is designed under the constraint of the Federal Communications Commission (FCC) ultrawideband (UWB) spectral mask. This pulse also enjoys the advantage of having a linear phase over the frequency band of interest and is orthogonal to its shifted version of one or more baud time. The finite time pulse is designed by an optimization method and concentrates its energy in the allowed bands specified by the FCC. Finally, an example is presented to illustrate how these types of wideband pulses can be transmitted and received with little distortion. [ABSTRACT FROM AUTHOR]

Wireless body area network (WBAN) is a new enabling system with promising applications in areas such as remote health monitoring and interpersonal communication. Reliable and optimum design of a WBAN system relies on a good understanding and in-depth studies of the wave propagation around a human body. However, the human body is a very complex structure and is computationally demanding to model. This paper aims to investigate the effects of the numerical model's structure complexity and feature details on the simulation results. Depending on the application, a simplified numerical model that meets desired simulation accuracy can be employed for efficient simulations. Measurements of ultra wideband (UWB) signal propagation along a human arm are performed and compared to the simulation results obtained with numerical arm models of different complexity levels. The influence of the arm shape and size, as well as tissue composition and complexity is investigated. [ABSTRACT FROM PUBLISHER]

Given the trend towards a user-centric concept in mobile communications, body area networks have received increasing attention within the wireless personal and body area networks community. In this paper, an experimental investigation is presented to derive suitable radio propagation models for ultra wideband (UWB) body-centric wireless communications. The performance of the body-centric UWB radio channel is investigated by considering several on-body links, including different body postures. System-level modeling of potential multiband orthogonal frequency-division multiplexed UWB system has been conducted and system performance is measured using bit error rate (BER) and signal-to-noise ratio. The conducted system analysis demonstrated that for 78% in the static case and 75% and 61% for stable and unstable transmitter locations in the pseudodynamic in-motion scenarios (respectively) of the specified on-body radio links, the BER is equal to or less than 0.1%. This demonstrates promising applications of the proposed UWB body-centric radio system. Based on these results, clear recommendations are given for best on-body locations leading to optimal system performance. [ABSTRACT FROM AUTHOR]

We have characterized the effect of human presence on path gain and time dispersion over ultrawideband (UWB) channels within the passenger cabin of a typical midsize airliner. We measured a few hundred channel frequency responses over the range 3.1-6.1 GHz between various locations within a Boeing 737-200 aircraft, with and without volunteers occupying the passenger seats. The links were deployed in a point-to-multipoint configuration with the transmitting antenna along the centre-line of the forward part of the cabin at either the ceiling or headrest level and the receiving antenna at the headrest or armrest level at selected locations throughout the rest of the cabin. As the density of occupancy increased from empty to full, path gain dropped by no more than a few dB on the ceiling-to-headrest paths but dropped by up to 10 dB on the ceiling-to-armrest and headrest-to-armrest paths. The gain reduction reached its maximum at the mid-point of the cabin and decreased thereafter. In all cases, increasing the density of occupancy caused the distance dependence of the rms delay spread to decrease greatly, the decay rate of the scattered components in the power delay profile (PDP) to almost double and the number of significant paths to drop by almost half. The results suggest that human presence substantially affects both path gain and time dispersion within the aircraft and should therefore be considered when assessing the performance of in-cabin wireless systems. [ABSTRACT FROM AUTHOR]

An experimental investigation to characterize the transient and spectral behavior of the ultrawideband (UWB) on-body radio propagation channel for body-centric wireless communications is presented. The measurements were performed considering over thirty on-body links in the front of human body in the anechoic chamber, and in indoor environment. Two different pairs of planar antennas have been used, namely, CPW-fed planar inverted cone antennas (PICA), and miniaturized CPW-fed tapered slot antennas (TSA). A path loss model is extracted from measured data, and a statistical study is performed on the time delay parameters. The goodness of different statistical models in fitting the root mean square (RMS) delay has been evaluated. Results demonstrate that the TSA, due to its more directive radiation behavior is less affected from the reflections from body parts and surrounding environment. The antenna shows significant size reduction and improved time delay behavior, and hence is an ideal candidate for UWB body area networks (BAN). [ABSTRACT FROM AUTHOR]

Wireless Body Area Networks (WBANs) are becoming an increasingly important part of the wireless communication system. In such a communication system various electronic devices carried by a person on his body can be connected. In this paper, we investigate the UWB body area propagation channel. The channel characterization is based on UWB on-body channel measurements. This paper describes the measurement campaign and the basic characteristics of the body area propagation channel extracted from measurement data. [ABSTRACT FROM AUTHOR]

A fundamental step in ultrawideband (UWB) communication system design involves the characterization of the indoor propagation channel. In this paper, we show that the UWB propagation channel parameters can be accurately predicted by employing ray tracing (RT) simulation carried out at various frequencies over the signal bandwidth. It is important to note that the determination of the rays reaching a given location is made only once, as the RT algorithm is independent of frequency. A parallel ray approximation (PRA) is used to significantly improve the computational efficiency of the RT based method. Moreover the accuracy of the approximation is verified through a measurement campaign. [ABSTRACT FROM AUTHOR]

This article presents a simplified approach for characterization of ultra wideband (UWB) through-the-wall propagation. The simplified approach requires spectrum analyzer rather than vector network analyzer. A minimum phase retrieval method based on Hilbert transform is used to retrieve the phase information. The proposed method is shown to be applicable to the insertion transfer function. While linear phase component cannot be retrieved, important factors for UWB receiver design such as group delay ripple and dispersion effect can be retrieved. In noisy channels, phase retrieval could be superior to direct phase measurements. Estimation of linear phase component can be achieved through matching the measured phase with the retrieved phase. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 465–470, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23107 [ABSTRACT FROM AUTHOR]

The design of a novel ultrawideband printed-circuit antenna is presented. By using a stepped-patch in combination with multiple resonating elements, a bandwidth of more than 150% is obtained. The performance is demonstrated through measurements and calculations with a commercially available field solver. A phase center analysis shows very small variations over the entire available bandwidth. [ABSTRACT FROM AUTHOR]

Given the trend towards a user-centric concept in mobile communications, body area networks have received increasing attention within the wireless personal area community. Researchers and designers have been investigating radio propagation characterisation and modelling owing to its importance in developing and designing efficient and reliable radio systems. The paper presents an experimental investigation of ultra-wideband (UWB) on-body radio propagation. Channel models with respect to large scale and delay analysis have been derived from measured parameters. Effects of different antenna types on channel behaviour are also demonstrated. Results and analyses highlight the consequences of changes in body postures and positions in addition to antenna orientations on the communication channels. Measurement data are also used in predicting the performance of potential UWB wireless systems and their applications in body-centric networks. It is indicated that bi-phase modulation for UWB body-centric networks performs better than pulse position modulation systems. The study also concludes that the use of hybrid antenna types for different on-body links will provide better system performance. [ABSTRACT FROM AUTHOR]

A time domain (TD) solution for the analysis of multiple diffraction of spherical waves after an array of nonperfectly conducting wedges with different interior angles is presented.The proposed TD solution is based on the representation of the inverse Laplace transform of the corresponding frequency domain solution in closed form, as it is given by a hybrid of the uniform theory of diffraction (UTD)-physic optics (PO) solution. The new formulation, validated with the results from technical literature, does not need to incorporate the TD version of the higher-order diffraction coefficients and allows for the calculation of large number of wedges. It has the major advantage in terms of the mathematical complexity and computation efficiency when compared with other TD solutions. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1006–1008, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25094 [ABSTRACT FROM AUTHOR]

Compared to narrowband antennas, ultrawideband (UWB) antennas have particular characteristics which involve new ways to model them. This paper introduces the use of parametric modeling to efficiently model transfer functions (and associated impulse responses) of UWB antennas, and to determine an equivalent circuit of their input impedance. [ABSTRACT FROM AUTHOR]

Using the reverberation chamber to obtain antenna radiation efficiency is considered. The reverberation chamber, which has for many years been used for electromagnetic compatibility measurements, can also be used with great advantage for antenna measurements since it simulates effectively a uniform multipath propagation environment. How a reverberation chamber can be used to measure the ultra-wideband (UWB) antenna efficiency in a very short time is described. The procedure based on time domain is described and some experimental results are given and compared to measurements obtained by the Wheeler cap method extended by Schantz to UWB antennas. [ABSTRACT FROM AUTHOR]