Citation
Ravari, Arastoo Rostami
(2005)
Channel Modeling and Direction-of-Arrival Estimation in Mobile Multiple-Antenna Communication Systems.
PhD thesis, Universiti Putra Malaysia.
Abstract
Antennas that are able to adaptively direct the transmitted (and received) energy are
of great interest in future wireless communication systems. The directivity implies
reduced transmit power and interference, and also a potential for increased capacity.
This thesis treats some modeling and estimation problems in mobile communication
systems that employ multiple antennas, primarily at the base stations. With multiple
antennas at the receive side, the spatial dimension is added, and processing is
performed in both the temporal and spatial domains. The potential benefits are
increased range, fading diversity and spatially selective transmission. Specifically,
the problems dealt in this thesis are mainly related to the uplink transmission from
mobile to the base station. Two main topics are studied, channel modeling and
estimation of channel parameters.
This thesis first describes the modeling of the reflected power distribution due to the
scatterers close to the mobile stations, in terms of the received signal azimuth at the
base station with multiple-antenna. As a more realistic channel modeling, a multipath fading deterministic channel model is proposed to generate properly
correlated faded waveforms with appropriate power distribution through azimuth
spread of received signal. The purpose of the proposed channel model is to model
fading received signal waveforms with Laplacian distribution of power through
received signal azimuth spread.
This thesis is divided into two parts; in the first part multipath fading by local
scattering are used to derive a channel model including the spatial dimension for non
frequency-selective fading. This means that the mobile is not modeled as a point
source but as a cluster of a large number of independent scatterers with small time
delay spread to take into account angular spreading of the signal. Properly correlated
fading waveforms are obtained by taking into account the angular spread of the
scattered signals from a particular distribution of scatterers. By appropriate scaling
of the array response vector (ARV) based on non-equal locations for various
received signal components as a function of distance from the transmitter, the
reflected power from a given scatterer is no longer constant but varies as a function
of the distance from the transmitter. Our proposed channel model is able to produce
fading signal waveform which agrees with the results of reflected angular power
dispersions measured in the field, e.g. Laplacian distribution of power in azimuth. It
is also shown that the channel response can be modeled as a complex Gaussian
vector.
Although the channel will be frequency selective in the case of multipath
propagation with considerable time spread, this can be modeled as having more than one cluster of scatterers. By employing Walsh-Hadamard codewo VdLrs)l
wideband multipath fading model is achieved.
It is shown that the statistical properties of proposed model such as signal
waveform's correlation, autocorrelation and crosscorrelation between generated
paths, are in good agreement with the theory in space and time domain. The model
can be applied to evaluate smart antenna systems and beamforming algorithms in the
uplink by generating uncorrelated multipaths Rayleigh fading waveforms with
certain spatio-temporal correlation and spatial coordinates relative to base stations to
simulate received signals from mobiles and interferers. Bit-error-rate (BER)
performance analysis of uniform linear array antenna (ULA) based on correlation -
matrix is also presented as an application of our proposed model for multipleantenna
evaluations. Our simulated results show 5% improvement than other
published related works.
One problem when modeling frequency selective fading is that each cluster has to be
assigned spatial parameters. Since the joint spatial and temporal characteristics are
unknown, non-parametric channel estimation approaches are required in this case in
order to estimate the channel parameter, which is the subject of the second part.
The second part of the thesis deals with channel parameter estimation of distributed
scattering sources. Because of local scattering around the transmitter the signal
waveforms appears spatially distributed at the receiver. The characterization of the
spatial channel, in particular mean direction of arrival and spatial spread, is of prime
interest for system optimization and performance prediction. Low-complexity spectral-based estimators are used for the estimation of direction and spatial spread
of the distributed source by employing the proposed channel model for simulation.
Estimated parameters from recent measurements ([PMFOO]) are compared with
estimated parameters from model generated waveforms as well as theoretical
distribution of received signal's angular spread. Good agreement between them is
observed which shows the correctness of our proposed channel model for simulating
spatio-temporally correlated received signal at an antenna array. The estimated
parameter error improved by 5% over the other published related works.
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Additional Metadata
Item Type: |
Thesis
(PhD)
|
Subject: |
Antennas (Electronic) - Telecommunication systems - Case studies |
Subject: |
Phased array antennas - Telecommunication systems - Case studies |
Call Number: |
FK 2005 2 |
Chairman Supervisor: |
Professor Borhanuddin Bin Mohd Ali, PhD |
Divisions: |
Faculty of Engineering |
Depositing User: |
Nur Izyan Mohd Zaki
|
Date Deposited: |
06 May 2010 08:51 |
Last Modified: |
03 Jan 2023 03:22 |
URI: |
http://psasir.upm.edu.my/id/eprint/5975 |
Statistic Details: |
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