الفهرس 
COMA Major Techniques for 3G and 4G Mobile CommunicationsOnly 14 pages are availabe for public view
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Abstract
Recently, wireless communications have shown a profound effect on our
day-to-day life. In past few years, research efforts are focused on Radio
Transmission Technologies to bridge the gap between practically feasible
channel utilization and the fundamental information theoretic limits on
channel capacity. One of the most important technology in efficient
channel utilization is ’multiuser detection’, which is now one of the state
of the art contributions in this domain.
In this thesis, CDMA techniques for 3G and 4G mobile communications,
focusing on MC-CDMA, are briefly presented. CDMA multiple-access
interference problem is presented by highlighting channel model and its
variations in accordance to using different techniques and system
parameters. Performance measures in multiuser detection are reviewed and
applied to single-user matched filter to highlight the problem. Then
multiple-access interference mitigation techniques in single-user matched
filter are reviewed. After that, the thesis focuses on the state of the art in
multiuser detectors, as a solution to this problem, with their different types
and techniques and highlighting each technique advantages and
disadvantages. Finally, the proposed design modification in one of the
multiuser detection adaptive techniques is presented. Simulation schemes
and results for typical uplink MC-CDMA system using the proposed
design in comparison to some other multiuser detectors are presented
under different system configurations and typical environment models.
In multipath environment, the proposed multiuser detector shows a good
bit error rate performance enhancement over other considered detectors
under all considered variables values. The relative performance
enhancement of the proposed detector is getting much better when the
system becomes worse, specially, under errors in amplitude estimates of
the received signals, it adds only extra 3% time overhead in detection time
over blind adaptive MMSE detector.Another modification in the proposed multiuser detector, by using its
decisions as tentative decision in multistage multiuser detector, adds much
more bit error rate performance enhancement over other considered
detectors under all considered variables values keeping the same relative
time overhead.