It is
important to characterise the indoor radio propagation channel to ensure
satisfactory performance of a wireless communication system. Site measurements
can be costly; propagation models have been developed as a suitable low-cost
alternative. The existing models can be classified into two major classes:
statistical models and site-specific propagation models. Statistical models
rely on measurement data; site-specific propagation models are based on
electromagnetic wave propagation theory. The ray-tracing technique is very
useful in site-specific propagation modelling. This paper gives an overview of
indoor propagation modelling and concentrates on a discussion of the
ray-tracing modelling technique because of its practical appeal and its
applicability to any environment
Friday, 17 July 2015
Crowd monitoring using image processing
The
understanding of crowd behaviour in semi-confined spaces is an important part
of the design of new pedestrian facilities, for major layout modifications to
existing areas and for the daily management of sites-subject to crowd traffic.
Conventional manual measurement techniques are not suitable for comprehensive
data collection of patterns of site occupation and movement. Real-time
monitoring is tedious and tiring, but safety-critical. This paper presents some
image processing techniques being developed at King's College London which,
using existing closed-circuit television systems, can support both data
collection and on-line monitoring of crowds. The application of these methods
could lead to a better understanding of crowd behaviour, improved design of the
built environment and increased pedestrian safety
Characterisation of propagation in 60 GHz radio channels
Narrowband
as well as wideband measurements have been performed in various indoor and outdoor
environments in order to enable the development of reliable prediction models
for 60 GHz radio channels. In addition, results of deterministic modelling on
the basis of geometric ray-tracing have been compared with measurement results,
showing that simple ray-tracing can be used to estimate both the narrowband and
wideband characteristics of a 60 GHz radio channel.
Website: https://www.arjonline.org/engineering/american-research-journal-of-electronics-and-communication-engineering/
Website: https://www.arjonline.org/engineering/american-research-journal-of-electronics-and-communication-engineering/
Passive intermodulation interference in communication systems
In
multifrequency communications environments, such as land mobile radio sites,
satellite earth stations, ships and surveillance aircraft, passive
intermodulation products (PIMP) generated by nonlinear materials and metallic
contacts can cause serious radio interference. This problem is well known and a
wide range of coaxial cables, connectors and materials have been investigated.
The paper gives an overview of passive intermodulation interference in
communication systems. It describes briefly the theory of intermodulation,
types of passive nonlinearities, mechanisms responsible for the generation of
PIMP, guidelines for minimising PIMP generation and techniques for locating
PIMP sources.
Website: https://www.arjonline.org/engineering/american-research-journal-of-electronics-and-communication-engineering/
Website: https://www.arjonline.org/engineering/american-research-journal-of-electronics-and-communication-engineering/
PCB design techniques for lowest-cost EMC compliance
Application
of good EMC (electromagnetic compatibility) practices to the design of printed
circuit boards (PCBs) usually helps to achieve the EMC performance required of
equipment and systems at much lower cost than alternative EMC measures at
higher levels of integration, such as whole-product shielding. EMC design is a
complex topic, but the proven best EMC practices for generalised PCB layout can
be fairly simply stated and grouped into five techniques, which interact with
each other to give dramatic improvements in EMC performance.
Website: https://www.arjonline.org/engineering/american-research-journal-of-electronics-and-communication-engineering/
Website: https://www.arjonline.org/engineering/american-research-journal-of-electronics-and-communication-engineering/
Monday, 29 June 2015
Analysis on the Basis of Volterra Series Signal–To–Noise Ratio of Nonlinear Device in the Conditions of the Stochastic Resonance Effect
In
modern conditions the problem of providing of reliable communication of data at
presence of interferences is considered one of major problems. Error-correcting
codes, optimal filters are created, and are used by the detection method of
accumulation, the probabilistic approach to suppressing random disturbances.
etc. [1,2,3].
At
the same time, researches by physicists at the end of the XX century [2],
resulted in paradoxical conclusions. The noise on the input of the nonlinear
systems possessing the effect of the so-called stochastic resonance (SR),
allows to stand out a weak (as compared to the noise) signal from additive
signal–noise mixture. The SR effect characterizes the response of the nonlinear
system on a weak input signal. Thus data-output of the nonlinear system, such
as an amplification factor and signal-to-noise ratio, at certain terms have the
distinctly expressed maximum [4,5].
Effects of Distributed Generation on System Power Losses and Voltage Profiles
Although
it is considered that DG reduces losses and improves system voltage profile,
this paper shows that this is usually true. The paper presents voltage
stability index based approach which utilizes combine sensitivity factor
analogy to optimally locate and size a multi-type DG in 48-bus Belin
distribution test system with the aim of reducing power losses and improving
the voltage profile. The multi-type DG can operate as; type 1 DG (DG generating
real power only), and type 2 DG (DG generating both real and reactive power).
It further shows that the system losses are reduced and the voltage profile
improved with the location of type 2 DG than with the location of type 1 DG. It
reaches a point where any further increase in number of DGs in the network
results for minimizing power losses and voltage profiles improvement.
Website: http://www.arjonline.org/engineering/american-research-journal-of-electrical-engineering/
Website: http://www.arjonline.org/engineering/american-research-journal-of-electrical-engineering/
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