Enhancement of Space-Time Receiver Structure with Multiuser Detection for Wideband CDMA Communication Systems
Wideband CDMA (WCDMA) which has been accepted as one of the radio access technology for third generation (3G) systems has many advantages such as efficient spectrum utilization and variable user data rates. However, multiple access interference (MAI) is a major constraint limiting the capacity of...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
2006
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/208/1/549041_FK_2006_32.pdf |
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| Summary: | Wideband CDMA (WCDMA) which has been accepted as one of the radio access
technology for third generation (3G) systems has many advantages such as
efficient spectrum utilization and variable user data rates. However, multiple
access interference (MAI) is a major constraint limiting the capacity of the
system. Multiuser detection and smart antenna technologies are capable of
increasing the system capacity through mitigation of such impairment.
In this thesis, a combination of spatial signal processing with temporal signal
processing is proposed. Additionally, the space-time receiver structure is
combined with multiuser detection to further enhance the system. We propose and
analyze different combined space-time linear multiuser detection configurations in
an uplink mobile radio communications channel that incorporates the spatial
temporal parameters. The performance of these receivers is evaluated as a
function of the number of antenna elements, Rake fingers and number of users.
We consider two different pilot symbol assisted adaptive beamforming
algorithms, Least Mean Square (LMS) and Recursive Least Square (RLS). The
algorithms are used to adjust the weights of the antenna array to form the
appropriate beam patterns to track the desired user and null interfering users. The
adaptive algorithms are evaluated as a function of the number of iterations it takes
to converge and its transmission performance are compared. Additionally, two
different linear multiuser detection techniques, Decorrelator and linear Minimum
Mean Square Error (MMSE) strategies are used in conjunction with the combined
receiver structure.The proposed combined Space Time Multiuser Detector which is suitable for
WCDMA systems is shown to provide significant gain in transmission
performance and system capacity. It is shown via simulation that the combined
RLS adaptive algorithm with the linear MMSE multiuser detector provides the
best overall performance. The simulation result also shows that the combined
receiver structure is robust in the presence of strong interference due to high data
rate users. |
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