An Investigation of Efficient Receiver Structures for CDMA Communication

Efficient allocation of the communication resources such as frequency bandwidth is an important problem in multiple access technique. In this thesis, we explore the potential of code-division multiple-access (CDMA) as an efficient resource-sharing technique. We explore recently proposed receivers and develop a unified vector space interpretation. Bit error rates of each receiver in the simple two user case are developed and compared. The decorrelating detector is subject to a capacity decrease when the number of active interfering users is small compared to the number of potential users. We propose an algorithm to modify the decorrelating detector so that a capacity increase is achieved when the signal-to-noise ratios of interfering users are very high. We analyze the algorithm in a simple case and provide results of Monte-Carlo simulation to demonstrate the viability of the algorithm. Thesis Supervisor: Gregory W. Wornell Title: Assistant Professor of Electrical Engineering Acknowledgments I would like to thank Professor Gregory MT. Wornell, not only for his enthusiastic teaching and invaluable advice and guidances on this research, but also for his help on various other matters. His supervision has had a significant impact in many areas of my personal development. I was very fortunate to have him as my thesis supervisor. My involvement with Professor Alan. V. Oppenheim was a great experience. He showed me an uncompromising standard of a good teacher. I enjoyed working with him in 6.341, too. Thanks are due to students in DSPG, from whom I received lots of comments and ideas on my research. They provided me with a pleasant working environment. I also would like to thank Chang Yoo for his friendship and advice. My deepest thank would go to my parents and my sisters. Without their support, sacrifice, and encouragement, this thesis would not have been possible. Thank you.