Bit Error Probability for Direct-Sequence / Spread-Spectrum Multiple-Access communications with Random Signature Sequence

• Main Authors: Chien, Tze Zen, 簡子仁
• Other Authors: Kou, Foon Yeon
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/96656095018149727998

碩士 === 中原大學 === 電機工程研究所 === 82 === In the last decade, various techniques have been developed to calculate the data bit error probability caused by multiple-access interference (MAI) for direct-sequence / spread-spectrum multiple-access (SS/SSMA) communication systems with random signature sequence. However, it is computationally difficult in the exact calculation, so emphasis has been on approximations and bounds. First, we inquire the model of DS/SSMA communication systems and derive the expression of the MAI. Random variables characterizing various aspects of the MAI are in terms of the random signature sequences, the data bits, the correlation functions of the chip waveform, and the propagation delays. Second, improved Gaussian approximation is developed to find bit error probability for DS/SSMA communication systems in conjunction with aperiodic autocorrelation function of the first signature sequence by using the central limit theorem. The accuracy of the improved Gauusian approximation with no noise for data bit error probability is greater than that offered by a widely used Gaussian method which we call the " standard Gaussian approximation " . This method can also be applied in a straightforward manner to derive the relation between the bit error probability and signal-to-noise ratio for DS/ SSMA communication systems with additive white Gaussian noise. The calculation for the improved Gaussian approximation is very complicated, so it takes long time to calculate the data bit error probability and the accuracy for the simple difference approximation is not very good. We derive a simple and accurate approximation for DS / SSMA communication systems by using the difference approximation and compare the results with the improved Gaussian approximation and simple difference approximation.