| Summary: | In this thesis, the effects of the Maximum Ratio Combining (MRC) and Interference
Rejection Combining (IRC) smart antennas on the capacity of the 3rd Generation (3G)
Wideband Code Division Multiple Access (WCDMA) cellular systems are investigated.
By exploiting the signal characteristics in the spatial dimension, the MRC and IRC
antennas are designed to receive signals in selective directions and reduce interferences in
certain areas respectively. When these smart antennas are used along with the Rake
receiver that extracts the useful information of signals in the temporal domain and the
WCDMA technology, the system capacity can be increased significantly.
In order to estimate and compare the system capacity improvements these
techniques offer, a software platform was designed to simulate the interference limited
uplink direction of a WCDMA system at the chip level. In this simulation platform, the
logical channel structure of the WCDMA air interface and a flexible antenna model that
can be easily configured were implemented in detail to accurately obtain capacity results.
In addition, realistic system conditions were emulated by considering practical channel
models, a multiple-cell configuration, the user voice activity factor and tight power
control.
Based on the simulated results, the advantages of using the IRC antennas, as
compared to the MRC antennas, are presented in terms of improvements in system
capacities. It is shown that the MRC and IRC smart antennas have their own advantages
under different multipath channel environments. Furthermore, the performance
evaluation results have indicated that turbo codes provide the most significant
improvement over the convolutional codes when used for the high rate multimedia users. The relationship between the numbers of low rate and high rate users a system can
accommodate concurrently is also established from the results.
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