Abstract: This paper introduces a new robust four way LMS and
variable step size NLMS beam forming algorithm to reduce interference in a
smart antenna system. This algorithm is able to resolve signals arriving from
narrowband sources propagating plane waves close to the array end fire. The
results of previously used adaptive algorithm have the fixed step size NLMS
will result in a trade-off issue between convergence rate and steady-state MSE
of NLMS algorithm. This issue is solved by using four way LMS and VSSNLMS
which will improve the efficiency of the convergence point. The proposed
algorithm implemented reduces the mean square error (MSE) and shows faster
convergence rate when compared to the conventional NLMS.
I. Introduction
A.
Introduction
In today’s world numbers of mobile users are increasing day
by day, hence it is necessary to serve such a huge market of mobile users with
high QOS even though the spectrum is limited. This becomes a major challenging
problem for the service providers to solve. A major limitation in capacity and
performance is co-channel interference caused by the increasing number of users
and the multipath fading and delay spread. Research efforts investigating
effective technologies to mitigate such effects have been going on and among
these methods Adaptive antenna employment is the most promising technology. This
project works on Adaptive Antenna which ensures high capacity providing with
the same Quality of Service(QOS).In a normal scenario currently the mobile
towers employ parabolic dish or a horn antenna but this suffers if the SNR is
low the signals have to be repeatedly retransmitted from mobile station to base
station. The use of Adaptive Antenna considers an array of antennas in which
the antenna will receive the delayed versions of the electromagnetic wave and
adds them to achieve high SNR.
B.
Problem Statement
In the earlier antenna radiation was directed based on
frequency or time, Therefore spectrum was not utilized efficiently because as
the number of users increases the quality of service decreases. Hence, in this
work a solution to use the Adaptive antenna frameworks have been proposed and
used as an efficient means to meet the quickly expanding the traffic volume. This issue of Technology has
discusses the importance of various advanced antenna schemes for improving the
same amount of spectrum and provides service to the large amount of mobile
users is deduced. This is done by separating the users with respect to
direction.
II.
Adaptive antenna
Adaptive antenna is the one which adapts itself to pick the
user signal in any direction without user intervention , basically it undergoes
through a two phase process:
-
Direction detection Estimation (DDE) using a
suitable algorithm and sensor data.
-
Beam forming which forms a beam in the desired
direction and nulls in the interference direction.
Direction Detection Estimation
(DDE) methods are used to detect the incoming wave and the other signals which
arrive from different parts of the space can be processed to extract different
type of data including direction desired incoming signal falling on the antenna
array.
Beam forming is a process of forming the Main beam in the desired
direction and nulls in the direction of jammers direction. The block diagram is
shown in Figure1 shows an adaptive
antenna structure with N antenna elements, DDE blocks, Adaptive signal
processor algorithms to make adaptive antenna system smart, where incoming
signal is processed by beam forming algorithms the figure also shows main beam
formed in the direction of desired signal and nulls in the jammers direction.
Fig. 1:
Adaptive Antenna
http://ijirst.org/Article.php?manuscript=IJIRSTV2I3036
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