1,675 research outputs found
A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles
In recent years, there has been a dramatic increase in the use of unmanned
aerial vehicles (UAVs), particularly for small UAVs, due to their affordable
prices, ease of availability, and ease of operability. Existing and future
applications of UAVs include remote surveillance and monitoring, relief
operations, package delivery, and communication backhaul infrastructure.
Additionally, UAVs are envisioned as an important component of 5G wireless
technology and beyond. The unique application scenarios for UAVs necessitate
accurate air-to-ground (AG) propagation channel models for designing and
evaluating UAV communication links for control/non-payload as well as payload
data transmissions. These AG propagation models have not been investigated in
detail when compared to terrestrial propagation models. In this paper, a
comprehensive survey is provided on available AG channel measurement campaigns,
large and small scale fading channel models, their limitations, and future
research directions for UAV communication scenarios
Performance analysis of ultra wide band indoor channel
This thesis report is submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Computer Science and Engineering, 2008.Cataloged from PDF version of thesis report.Includes bibliographical references (page 41).Research on wireless communication system has been pursued for many
years, but there is a renewed interest in ultra-wideband (UWB) technology for
communication within short range, because of its huge bandwidth and low
radiated power level. This emerging technology provides extremely high data
rate in short ranges but in more secured approach. In order to build systems
that realize all the potential of UWB, it is first required to understand UWB
propagation and the channel properties arise from the propagation. In this
research, the properties of UWB channel for indoor industrial environment
was evaluated. A few indoor channel models have been studied so far for
different environments but not for indoor industrial environment and various
data rates are obtained according to wireless channel environments.
Therefore, an accurate channel model is required to determine the maximum
achievable data rate. In this thesis, we have proposed a channel model for
indoor industrial environment considering the scattering coefficient along with
the other multipath gain coefficient. This thesis addresses scattering effect
while modeling UWB channel. Here, the performance of UWB channel model
is analyzed following the parameters, such as power delay profile and the
temporal dispersion properties which are also investigated in this paper.Kazi Afrina YasmeenA. K. M. WahiduzzamanMD. Ahamed ImtiazB. Computer Science and Engineerin
Radio channel characterisation and system-level modelling for ultra wideband body-centric wireless communications
PhDThe next generation of wireless communication is evolving towards user-centric networks,
where constant and reliable connectivity and services are essential. Bodycentric
wireless network (BCWN) is the most exciting and emerging 4G technology
for short (1-5 m) and very short (below 1 m) range communication systems. It has
got numerous applications including healthcare, entertainment, surveillance, emergency,
sports and military. The major difference between the BCWN and conventional
wireless systems is the radio channel over which the communication takes place. The
human body is a hostile medium from the radio propagation perspective and it is
therefore important to understand and characterise the effect of the human body on
the antenna elements, the radio propagation channel parameters and hence the system
performance. In addition, fading is another concern that affects the reliability and
quality of the wireless link, which needs to be taken into account for a low cost and
reliable wireless communication system for body-centric networks.
The complex nature of the BCWN requires operating wireless devices to provide
low power requirements, less complexity, low cost and compactness in size. Apart
from these characteristics, scalable data rates and robust performance in most fading
conditions and jamming environment, even at low signal to noise ratio (SNR) is
needed. Ultra-wideband (UWB) technology is one of the most promising candidate for
BCWN as it tends to fulfill most of these requirements. The thesis focuses on the characterisation
of ultra wideband body-centric radio propagation channel using single
and multiple antenna techniques. Apart from channel characterisation, system level
modelling of potential UWB radio transceivers for body-centric wireless network is
also proposed. Channel models with respect to large scale and delay analysis are derived
from measured parameters. Results and analyses highlight the consequences
of static and dynamic environments in addition to the antenna positions on the performance
of body-centric wireless communication channels. Extensive measurement
i
campaigns are performed to analyse the significance of antenna diversity to combat
the channel fading in body-centric wireless networks. Various diversity combining
techniques are considered in this process. Measurement data are also used to predict
the performance of potential UWB systems in the body-centric wireless networks.
The study supports the significance of single and multiple antenna channel characterisation
and modelling in producing suitable wireless systems for ultra low power
body-centric wireless networks.University of Engineering and Technology Lahore Pakista
Comprehensive design and propagation study of a compact dual band antenna for healthcare applications
In this paper, a dual band planar inverted F antenna (PIFA) has been investigated for cooperative on- and off-body communications. Free space and on-body performance parameters like return loss, bandwidth, radiation pattern and efficiency of this antenna are shown and investigated. The on- and off-body radio propagation channel performance at 2.45 GHz and 1.9 GHz have been investigated, respectively. Experimental investigations are performed both in the anechoic chamber and in an indoor environment. The path loss exponent has been extracted for both on- and off-body radio propagation scenarios. For on-body propagation, the path loss exponent is 2.48 and 2.22 in the anechoic chamber and indoor environment, respectively. The path loss exponent is 1.27 for off-body radio propagation situation. For on-body case, the path loss has been characterized for ten different locations on the body at 2.45 GHz, whereas for off-body case radio channel studies are performed for five different locations at 1.9 GHz. The proposed antenna shows a good on- and off-body radio channel performance
Statistical Modeling of Ultrawideband Body-Centric Wireless Channels Considering Room Volume
This paper presents the results of a statistical modeling of onbody ultrawideband (UWB) radio channels for wireless body area network (WBAN) applications. Measurements were conducted in five different rooms. A measured delay profile can be divided into two domains; in the first domain (04 ns) has multipath components that are dominant and dependent on room volume. The first domain was modeled with a conventional power decay law model, and the second domain with a modified Saleh-Valenzuela model considering the room volume. Realizations of the impulse responses are presented based on the composite model and compared with the measured average power delay profiles
Modelling and characterisation of antennas and propagation for body-centric wireless communication
PhDBody-Centric Wireless Communication (BCWC) is a central point in the development
of fourth generation mobile communications. The continuous miniaturisation of sensors,
in addition to the advancement in wearable electronics, embedded software, digital
signal processing and biomedical technologies, have led to a new concept of usercentric
networks, where devices can be carried in the user’s pockets, attached to the
user’s body or even implanted.
Body-centric wireless networks take their place within the personal area networks,
body area networks and body sensor networks which are all emerging technologies
that have a broad range of applications such as healthcare and personal entertainment.
The major difference between BCWC and conventional wireless systems is the
radio channel over which the communication takes place. The human body is a hostile
environment from radio propagation perspective and it is therefore important to understand
and characterise the effect of the human body on the antenna elements, the
radio channel parameters and hence the system performance. This is presented and
highlighted in the thesis through a combination of experimental and electromagnetic
numerical investigations, with a particular emphasis to the numerical analysis based
on the finite-difference time-domain technique.
The presented research work encapsulates the characteristics of the narrowband
(2.4 GHz) and ultra wide-band (3-10 GHz) on-body radio channels with respect to
different digital phantoms, body postures, and antenna types hence highlighting the
effect of subject-specific modelling, static and dynamic environments and antenna performance
on the overall body-centric network. The investigations covered extend further
to include in-body communications where the radio channel for telemetry with
medical implants is also analysed by considering the effect of different digital phantoms
on the radio channel characteristics. The study supports the significance of developing
powerful and reliable numerical modelling to be used in conjunction with measurement campaigns for a comprehensive understanding of the radio channel in
body-centric wireless communication. It also emphasises the importance of considering
subject-specific electromagnetic modelling to provide a reliable prediction of the
network performance
Ultra-Wideband Wireless Channels - Estimation, Modeling and Material Characterization
This licentiate thesis is focused on the characterization of ultra-wideband wireless channels. The thesis presents results on ultra-wideband communications as well as on the ultra-wideband characterization of materials. The communications related work consisted in the measurement and modeling of outdoor scenarios envisioned for infostation systems. By infostation, we mean a communication system covering a small area, i.e., ranging up to 20 m, where mobile users can pass by or stop while receiving large amounts of data in a short period of time. Considering the expected (but perhaps overly optimistic) 480 Mbps for UWB systems, it should be possible to download a complete DVD in roughly two minutes, which is something not realizable with any of the current wireless technologies. Channel models, commonly based on measurements, can be used to evaluate the performance of such systems. We therefore, we started by performing measurements at one of the scenarios where infostation systems can exist in the future, namely, petrol stations. The idealized model, was one that could correctly describe the continuous evolution of the channel impulse response for a moving user within the system’s range, and therefore it was deemed necessary to track the multipath components defining the impulse responses along a path of several meters. To solve this problem we designed a novel high-resolution scatterer detection method, which is described in Paper I, capable of tracking individual multipath components for a moving user by identifying the originating point scatterers in a two dimensional geometrical space. The same paper also gives insight on some properties of clusters of scatterers, such as their direction-selective radiated power. The scatterer detection method described in Paper I provided us with the required tools to create the channel model described in Paper II. The proposed channel model has a geometrical basis, i.e., each realization of the channel is based on a virtual map containing point scatterers that contribute to the impulse response by multipath components. Some of the particular characteristics of the model include non-stationary effects, such as shadowing and cluster’s visibility regions. At the end of Paper II, in a simple validation step, the output of the channel model showed a good match with the measured impulse responses. The second part of our work, documented in Paper III, consisted on the dielectric characterization of soil samples using microwave measurements. This project was made in cooperation with the Department of Physical Geography and Ecosystem Analysis at Lund University, which had been developing research work on methane emissions from the wetlands in Zackenberg, Greenland. In recent years, a lot of attention has been put into the understanding of the methane emissions from soils, since methane is a greenhouse gas 20 times stronger than carbon dioxide. However, whereas the methane emissions from natural soils are well documented, the reason behind this effect is an open issue. The usage of microwave measurements to monitor soil samples, aims to address this problem by capturing the sub-surface changes in the soil during gas emissions. An experiment consisting on the monitoring of a soil sample was performed, and a good correlation was found between the variations of the microwave signals and the methane emissions. In addition, the soil dielectric constant was calculated, and from that, the volumetric fractions of the soil constituents which provided useful data for the elaboration of models to describe the gas emission triggering mechanisms. Based on this laboratory experiment, a complete soil monitoring system was created and is at the time of writing running at Zackenberg, Greenland
Diversity performance of off-body MB-OFDM UWB-MIMO
This paper introduces a novel formalism to improve the performance of an off-body system by deploying multiple ultra wideband (UWB) antennas, positioned strategically on the body. A methodology is presented for determining the optimal positions of UWB antennas on the body, necessary to provide a reliable multiband orthogonal frequency division multiplexing (MB-OFDM) UWB diversity antenna system operating in the Federal Communications Commission frequency band between 3.1 and 10.6 GHz. By evaluating the diversity metric, using simulation and measurement data, it is shown that the performance of such a system is stable throughout the entire investigated frequency band for both indoor and outdoor environments. There is a good agreement between the simulated and measured diversity values with a deviation of less than 9%. Therefore, the proposed technique optimizes the antennas' positions for maximum diversity performance within a very broad frequency band, independent of the used wireless communication standard. Thus, the obtained diversity system might be used in any kind of wireless communication link within that frequency band, e.g., UWB-OFDM, UWBMB-OFDM, UWB, or even narrowband transmission
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