Research On Interference Analysis And Cancellation Algorithms For CDMA Mobile Communication Systems

CDMA (Code Division Multiple Access) becomes main stream in the 3rd generation mobile communication systems due to its attractive features, such as simple frequency deployment, high spectrum efficiency, multipath fading mitigation, soft hand-off and macro-diversity. This dissertation focuses on the wideband CDMA based technologies, including interference cancellation and receiver techniques.The effect of quantization and finite wordlength on the performance of RAKE receiver and Viterbi decoder is addressed for fixed-point simulations in cdma2000-1x downlink. Selections of parameters as ADC wordlength, channel estimation interval length, mobile velocity and pilot power gain factor on the system performance are investigated via simulations. Detailed discussions and comparisons of results between the floating-point and fixed-point simulations lead to some important conclusions, which provide references for practical systems. Furthermore, based on statistical analyses of quantization errors, mathematic relationship is obtained between the quantization SNR and the wordlength of the baseband sampled signal. Design methods of special filters improving the quantization SNR hence the equivalent quantizer wordlength are proposed, which not only demonstrate good performance but also enable easy ASIC implementation.As for continuous pilot aided DS-CDMA systems, statistical properties of pilot interference, multiple access interference (MAI), multipath interference (MPI) and background noise are investigated in detail for both single-cell and multiple-cell environments under the conditions of uniform multipath intensity profile and ideal/non-ideal channel estimation, which leads to average symbol error probabilities for DS-CDMA systems with/without pilot cancellation evaluated via numerical results and system simulations. Besides, based on the statistical analysis of moving averaging channel estimation error, mathematic relationship is obtained between the pilot power gain factor and the variance of channel estimation error.Based on theoretical analyses, two practical algorithms—symbol-level and chip-level pilot cancellation schemes are proposed and their equivalence is also verified. Simulation results show that the symbol-level pilot cancellation scheme can not only improve the RAKE receiver performance but also enable relatively low implementation complexity. Besides, this algorithm can be extended to multiple-cell environments to effectively eliminate the pilot interference from...