Increase in System Utilization Rate and Selection of Optimum Code Rate in Turbo-Coded DS-CDMA Systems

• Main Authors: Ciou-huei Lai, 賴秋惠
• Other Authors: Kuen-tsair Lay
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/25193735636782752093

碩士 === 國立臺灣科技大學 === 電子工程系 === 98 === In wireless transmission systems, the resources are limited. We hope to increase the system capacity under the limited resources.In this thesis, we discuss the efficiency of direct sequence code division multiple access (DS-CDMA) systems in multiuser situations. We use the cascade of a cyclic error correction (CEC) code and a turbo code to reduce the bit error rate of systems. By puncturing, we can adjust the code rate of the turbo code. Then, by proper choice of code rate, higher data transmission rate can be achieved. 　　We consider two kinds of channels: additive white Gaussian noise (AWGN) channels and Rayleigh fading channels. Where in the fading is bit-by-bit. In Rayleigh fading channels, because the bit error rate is large when the multiuser interference increases in the system, we try to reduce it by the diversity scheme. We also use the queueing models to predict the blocking probability of systems. Finally, we consider two kinds of cases to find the optimal code rate. One is to decide the optimal code rate based on the acceptable blocking probability. The other one is to decide the optimal code rate based on both the blocking probability and the data transmission rate.