4 research outputs found
Time-Scale Domain Characterization of Time-Varying Ultrawideband Infostation Channel
The time-scale domain geometrical-based method for the characterization of the time varying ultrawideband (UWB) channel typical of an infostation channel is presented. Compared to methods that use Doppler shift as a measure of time-variation in the channel this model provides a more reliable measure of frequency dispersion caused by terminal mobility in the UWB infostation channel. Particularly, it offers carrier frequency independent method of computing wideband channel responses and parameters which are important for ultrawideband systems. Results show that the frequency dispersion of the channel depends on the frequency and not on the choice of bandwidth. And time dispersion depends on bandwidth and not on the frequency. It is also shown that for time-varying UWB, frame length defined over the coherence time obtained with reference to the carrier frequency results in an error margin which can be reduced by using the coherence time defined with respect to the maximum frequency in a given frequency band. And the estimation of the frequency offset using the time-scale domain (wideband) model presented here (especially in the case of multiband UWB frequency synchronization) is more accurate than using frequency offset estimate obtained from narrowband models
Modeling spatial aspects of mobile channel for low antenna height environments, Journal of Telecommunications and Information Technology, 2006, nr 2
It is essential to have deep understanding of the mobile radio channel in particular for radio communication modeling and advanced technology system design. Models for the mobile radio channel are vital for the study of smart antenna systems, both for the design of algorithms, system-testing purposes, and for network planning. This paper provides an intensive study of the spatial characteristics of the mobile channel for low antenna height cellular environments, i.e., picocells and microcells, assuming Gaussian distributed scatterers. We investigate previous work on the angle of arrival (AoA) statistics for Gaussian distributed scatterers and make appropriate comments. Further, we employ the recently proposed eccentro-scattering physical channel model, as a generalized model, to derive the probability density function (pdf) of AoA of the multipaths at base station (BS) assuming Gaussian distributed scatterers around both BS and mobile station (MS). We found that the pdf of AoA at BS is directly affected by the standard deviation of the scatterers’ density and the size of the scattering disc. The derived formulas, in closed form, can be used further for performance assessment of smart antennas and beamwidth design purposes
Geometry-based stochastic physical channel modeling for cellular environments
Telecommunication has experienced significant changes over the past few years and its
paradigm has moved from wired to wireless communications. The wireless channel
constitutes the basic physical link between the transmitter and the receiver antennas.
Therefore, complete knowledge of the wireless channel and radio propagation
environment is necessary in order to design efficient wireless communication systems.
This PhD thesis is devoted to studying the spatial and temporal statistics of the wireless
channel in cellular environments based on a geometry-based stochastic physical channel
modeling approach. Contributions in this thesis report include the following:
• A new physical channel model called the eccentro-scattering model is proposed
to study the spatial and temporal statistics of the multipath signals in cellular
environments.
• Generic closed-form formulas for the probability density function (pdf) of angle
of arrival (AoA) and time of arrival (ToA) of the multipath signals in each cellular
environment are derived. These formulas can be helpful for the design and
evaluation of modern communication systems.
• A new Gaussian scattering model is proposed, which consists of two Gaussian
functions for the distribution of scatterers around base station (BS) and mobile
station (MS) and confines these scatterers within a scattering disc.
• The effect of mobile motion on the spatial and temporal statistics of the
multipath signals in cellular environments is discussed. Three motion scenarios are
considered for the possible trajectory of the mobile unit. Furthermore, two different
cases are identified when the terrain and clutter of mobile surrounding have
additional effect on the temporal spread of the multipath signals during motion.
• The physical channel model is employed to assess the performance of a RAKE
receiver in cellular environments.
• Comparisons between uniform scattering and Gaussian scattering, which are the
two assumptions for the distribution of scatterers usually used in the derivation of
the pdf of AoA, are also presented.
• An overview of earlier physical channel models and comparisons between these
models and with the proposed model are presented