40 research outputs found
Spatio-Temporal processing for Optimum Uplink-Downlink WCDMA Systems
The capacity of a cellular system is limited by two different phenomena, namely
multipath fading and multiple access interference (MAl). A Two Dimensional (2-D)
receiver combats both of these by processing the signal both in the spatial and temporal
domain. An ideal 2-D receiver would perform joint space-time processing, but at the
price of high computational complexity. In this research we investigate computationally
simpler technique termed as a Beamfom1er-Rake. In a Beamformer-Rake, the output of a
beamfom1er is fed into a succeeding temporal processor to take advantage of both the
beamformer and Rake receiver. Wireless service providers throughout the world are
working to introduce the third generation (3G) and beyond (3G) cellular service that will
provide higher data rates and better spectral efficiency. Wideband COMA (WCDMA)
has been widely accepted as one of the air interfaces for 3G. A Beamformer-Rake
receiver can be an effective solution to provide the receivers enhanced capabilities
needed to achieve the required performance of a WCDMA system.
We consider three different Pilot Symbol Assisted (PSA) beamforming techniques,
Direct Matrix Inversion (DMI), Least-Mean Square (LMS) and Recursive Least Square
(RLS) adaptive algorithms. Geometrically Based Single Bounce (GBSB) statistical
Circular channel model is considered, which is more suitable for array processing, and
conductive to RAKE combining. The performances of the Beam former-Rake receiver are
evaluated in this channel model as a function of the number of antenna elements and
RAKE fingers, in which are evaluated for the uplink WCDMA system. It is shown that,
the Beamformer-Rake receiver outperforms the conventional RAKE receiver and the
conventional beamformer by a significant margin. Also, we optimize and develop a
mathematical formulation for the output Signal to Interference plus Noise Ratio (SINR)
of a Beam former-Rake receiver.
In this research, also, we develop, simulate and evaluate the SINR and Signal to Noise
Ratio (Et!Nol performances of an adaptive beamforming technique in the WCDMA
system for downlink. The performance is then compared with an omnidirectional antenna
system. Simulation shows that the best perfom1ance can be achieved when all the mobiles
with same Angle-of-Arrival (AOA) and different distance from base station are formed in
one beam
A New Combination of RAKE Receiver and Adaptive Antenna Array Beamformer for Multiuser Detection in WCDMA Systems
The aim of this paper is to combine smart antenna beamforming and RAKE receiver in wideband code division multiple access (WCDMA). The proposed method combines spatial diversity as well as temporal diversity to improve the performance and overcome both interferences and multipath fading. This investigation has focused on one of the new proposed blind beamforming algorithms. It is based on constrained constant modulus (CCM) algorithm which is used for deriving a recursive-least-squares (RLS-) type optimization algorithm. We illustrate the comparison of bit error rate (BER) of the proposed receiver with simple correlator and also 1D-RAKE receiver in multiuser detection (MUD) WCDMA. The simulation results show that the proposed 2D-RAKE receiver offers lower BER rather than conventional ones, that is, it is an effective solution for decreasing the effect of interference and increasing the capacity, in a joint state
Spatio-Temporal processing for Optimum Uplink-Downlink WCDMA Systems
The capacity of a cellular system is limited by two different phenomena, namely
multipath fading and multiple access interference (MAl). A Two Dimensional (2-D)
receiver combats both of these by processing the signal both in the spatial and temporal
domain. An ideal 2-D receiver would perform joint space-time processing, but at the
price of high computational complexity. In this research we investigate computationally
simpler technique termed as a Beamfom1er-Rake. In a Beamformer-Rake, the output of a
beamfom1er is fed into a succeeding temporal processor to take advantage of both the
beamformer and Rake receiver. Wireless service providers throughout the world are
working to introduce the third generation (3G) and beyond (3G) cellular service that will
provide higher data rates and better spectral efficiency. Wideband COMA (WCDMA)
has been widely accepted as one of the air interfaces for 3G. A Beamformer-Rake
receiver can be an effective solution to provide the receivers enhanced capabilities
needed to achieve the required performance of a WCDMA system.
We consider three different Pilot Symbol Assisted (PSA) beamforming techniques,
Direct Matrix Inversion (DMI), Least-Mean Square (LMS) and Recursive Least Square
(RLS) adaptive algorithms. Geometrically Based Single Bounce (GBSB) statistical
Circular channel model is considered, which is more suitable for array processing, and
conductive to RAKE combining. The performances of the Beam former-Rake receiver are
evaluated in this channel model as a function of the number of antenna elements and
RAKE fingers, in which are evaluated for the uplink WCDMA system. It is shown that,
the Beamformer-Rake receiver outperforms the conventional RAKE receiver and the
conventional beamformer by a significant margin. Also, we optimize and develop a
mathematical formulation for the output Signal to Interference plus Noise Ratio (SINR)
of a Beam former-Rake receiver.
In this research, also, we develop, simulate and evaluate the SINR and Signal to Noise
Ratio (Et!Nol performances of an adaptive beamforming technique in the WCDMA
system for downlink. The performance is then compared with an omnidirectional antenna
system. Simulation shows that the best perfom1ance can be achieved when all the mobiles
with same Angle-of-Arrival (AOA) and different distance from base station are formed in
one beam
Spatial filtering for pilot-aided WCDMA systems: a semi-blind subspace approach
This paper proposes a spatial filtering technique for
the reception of pilot-aided multirate multicode direct-sequence
code division multiple access (DS/CDMA) systems such as wideband
CDMA (WCDMA). These systems introduce a code-multiplexed
pilot sequence that can be used for the estimation of the
filter weights, but the presence of the traffic signal (transmitted
at the same time as the pilot sequence) corrupts that estimation
and degrades the performance of the filter significantly. This is
caused by the fact that although the traffic and pilot signals are
usually designed to be orthogonal, the frequency selectivity of the
channel degrades this orthogonality at hte receiving end. Here,
we propose a semi-blind technique that eliminates the self-noise
caused by the code-multiplexing of the pilot. We derive analytically
the asymptotic performance of both the training-only and
the semi-blind techniques and compare them with the actual simulated
performance. It is shown, both analytically and via simulation,
that high gains can be achieved with respect to training-onlybased
techniques.Peer Reviewe
Space time transceiver design over multipath fading channels
Imperial Users onl