by Tsan-Fai Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 64-68). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Review on spread spectrum communications --- p.1 / Chapter 1.2 --- The spread spectrum techniques --- p.2 / Chapter 1.2.1 --- Direct Sequence (DS) Systems --- p.2 / Chapter 1.2.2 --- Frequency Hopping (FH) Systems --- p.2 / Chapter 1.2.3 --- Time Hopping (TH) Systems --- p.4 / Chapter 1.2.4 --- Hybrid Systems --- p.4 / Chapter 1.3 --- Existing Applications of the spread spectrum systems --- p.5 / Chapter 1.4 --- Organization of the thesis --- p.6 / Chapter 2 --- The Concept of Duality --- p.7 / Chapter 2.1 --- Multi-Carrier Systems - An Overview --- p.7 / Chapter 2.2 --- Orthogonal Frequency Division Multiplexing --- p.8 / Chapter 2.2.1 --- Bandwidth Efficiency --- p.9 / Chapter 2.2.2 --- Spectral Efficiency --- p.10 / Chapter 2.2.3 --- Effects of fading --- p.11 / Chapter 2.3 --- Applications of OFDM in multiple access --- p.13 / Chapter 2.3.1 --- ST-CDMA --- p.13 / Chapter 2.3.2 --- MC-DS-CDMA --- p.14 / Chapter 2.3.3 --- OFDM-CDMA --- p.15 / Chapter 2.4 --- Duality - Time-Frequency Interrelation --- p.16 / Chapter 3 --- Performance of Multi-Carrier CDMA System --- p.17 / Chapter 3.1 --- System Model --- p.17 / Chapter 3.2 --- Performance Analysis --- p.20 / Chapter 3.2.1 --- Gaussian Channel --- p.20 / Chapter 3.2.2 --- Fading Channel --- p.24 / Chapter 3.3 --- Performance with Pulse Shape --- p.33 / Chapter 3.4 --- Appendix --- p.34 / Chapter 4 --- Signal Design Criteria for MC-CDMA System --- p.36 / Chapter 4.1 --- Existence of Signal Distortion --- p.37 / Chapter 4.2 --- Measures of the Signal Envelope Fluctuation --- p.38 / Chapter 4.3 --- Complementary Sequences --- p.41 / Chapter 4.4 --- Crest Factors --- p.42 / Chapter 4.4.1 --- Time-limited Pulse --- p.43 / Chapter 4.4.2 --- Ideally Band-Limited Pulses --- p.43 / Chapter 4.4.3 --- Shaped Pulses --- p.45 / Chapter 4.5 --- Spectrally Efficient Complementary (SEC) Sequences --- p.48 / Chapter 4.6 --- Construction of Spectrally Efficient Complementary(SEC) Sequences --- p.50 / Chapter 4.7 --- Generalized Multiphase Spectrally Efficient Complementary Sequences --- p.55 / Chapter 5 --- Summary and Future Extensions --- p.58 / Chapter 5.1 --- Summary of the Results --- p.58 / Chapter 5.2 --- Topics for Future Research --- p.59 / Appendix / Chapter A --- Exhaustive search of MPSEC sequences --- p.61 / Chapter B --- Papers derived from this thesis --- p.63 / Bibliography --- p.64

by Yin-Man Lee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 82-[87]). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of MC-CDMA --- p.1 / Chapter 1.2 --- System Model --- p.3 / Chapter 1.3 --- Receiver Optimization --- p.7 / Chapter 1.4 --- Transmitter Optimization --- p.9 / Chapter 1.5 --- Nonlinearly Constrained Optimization --- p.10 / Chapter 1.6 --- Outline of Thesis --- p.11 / Chapter 2 --- Centralized Transmitter Optimization for MC-CDMA Systems --- p.13 / Chapter 2.1 --- Introduction --- p.13 / Chapter 2.2 --- Problem Development --- p.15 / Chapter 2.3 --- Lagrangian Optimization Approaches --- p.16 / Chapter 2.3.1 --- Penalty Function Method --- p.17 / Chapter 2.3.2 --- Barrier Function Method --- p.19 / Chapter 2.3.3 --- Powell's Method and Augmented Lagrangian Method --- p.21 / Chapter 2.4 --- Optimal FDMA System --- p.23 / Chapter 2.5 --- Modified Centralized Optimization Schemes --- p.25 / Chapter 2.6 --- Performance --- p.27 / Chapter 2.6.1 --- Typical Behavior --- p.27 / Chapter 2.6.2 --- Average Performance --- p.32 / Chapter 2.7 --- Summary --- p.38 / Chapter 3 --- Decentralized Transmitter Optimization for MC-CDMA Sys- tems --- p.39 / Chapter 3.1 --- Introduction --- p.39 / Chapter 3.2 --- System Model --- p.41 / Chapter 3.3 --- Optimization --- p.42 / Chapter 3.3.1 --- Receiver Optimization --- p.43 / Chapter 3.3.2 --- Single-user Transmitter Optimization --- p.44 / Chapter 3.3.3 --- Decentralized Transmission Scheme --- p.45 / Chapter 3.3.4 --- Multirate Transmission with Decentralized Transmission Scheme --- p.47 / Chapter 3.4 --- Performance --- p.48 / Chapter 3.5 --- Summary --- p.57 / Chapter 4 --- Performance Evaluation of Various Adaptive Transmission Schemes --- p.59 / Chapter 4.1 --- Introduction --- p.59 / Chapter 4.2 --- Comparison of Different Adaptive Transmission Schemes --- p.61 / Chapter 4.3 --- Adaptive Transmission Schemes with K > M --- p.64 / Chapter 4.4 --- Modified Adaptive Transmission Scheme with Graceful Degrada- tion in the SNR --- p.68 / Chapter 4.5 --- Summary --- p.71 / Chapter 5 --- Conclusions and Future Work --- p.73 / Chapter 5.1 --- Conclusions --- p.73 / Chapter 5.2 --- Future Work --- p.75 / A The Hungarian Method for Optimal Frequency Assignment --- p.76 / Bibliography --- p.82

Kwan Ho-yuet. / "April 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 98-[103]). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The introduction of cellular wireless systems in the 1980s has resulted in a huge demand for personal communication services. This demand has made larger capacity systems necessary. This has been partially satisfied by the introduction of second generation digital systems. New third generation systems are now under going standardisation and will require even more efficient utilisation of the spectrum if the high bandwidth features and larger capacity are to become a reality. Motivated by these growing requirements we discuss methods of achieving large improvements in spectral efficiency and performance. Multiple-user communications over a channel can only be achieved with some form of diversity. In this work we point out that the efficient utilisation of the dimensions of space, time, and frequency will ultimately maximise the system capacity of a multiple-user system. We apply our receiver techniques solely to the base-station design where capacity limitations are currently present. We note however, that some of these techniques could also be applied at the mobile terminal receiver. We primarily focus our attention on the direct-sequence code-division multiple-access (DS/CDMA) channel, since this channel is inherently interference limited by other users in the cell of interest. We exploit a new powerful channel coding technique named " turbo coding" for its iterative decoding approach. We show how we can substitute the inner convolutional code of a turbo code encoder with the CDMA channel. By " iterative detection/decoding" or " turbo equalisation" at the receiver we achieve performance results which show the interference from other users to approach complete removal. We develop and analyse a new, low complexity, iterative interference canceller/decoder. This receiver has complexity per user linear with the memory of the channel and independent of the number of users in the system. We extend this receiver to more realistic channels that are asynchronous and include multi-path, and include spatial diversity by using an antenna array at the receiver. The CDMA channel we study exclusively uses randomly generated spreading codes. With this channel model we still achieve single user performance (no interference from other users) with a 10logL gain from L antenna elements and a gain of up to 10logP from P multi-path components. With any new receiver design, sensitivity to channel parameter errors is of paramount interest. We find that the sensitivity of our receiver is low with respect to the parameter errors induced. This is as we desire for a realisable receiver design. Finally we investigate the application of this new iterative interference canceller/decoder receiver to a number of other interference channels. These include the intersymbol interference (ISI) channel, partial response signalling (PRS), and continuous phase modulation (CPM). For these channels excellent performance improvement is generally achieved by the utilisation of the iterative interference canceller/decoder solution. / Thesis (PhD)--University of South Australia, 1999

Interference from other adjacent users in wireless applications is a major problem in direct-sequence code-division multiple-access (DS-CDMA). This is also known as the near-far problem where a strong signal from one user interferes with other users. The current approach to deal with the near-far problem in DS-CDMA systems is to use strict transmitter power control. An alternative approach is to use near-far resistant receivers. The practical near-far resistance receiver structure is the adaptive decorrelating detectors since it avoids complex matrix inversion. The existing CDMA standard known as IS-95 uses a long signature code sequence. However for simplicity, the adaptive multi-user receiver uses short signature code sequence. The problem is that adaptive receivers lose near-far resistance as the number of users increases in the system. This thesis describes a novel method of multistage decision feedback cancellation (DFC) scheme immune from the near-far problem. The performance of the new DFC structure is constructed using three different adaptive algorithms: the least mean squared (LMS), the recursive least squared (RLS) and the linearly constraint constant modulus (LCCM) adaptive algorithms. It is found that LMS adaptive algorithm provides the best result considering its simple hardware complexity. It is also found that the LMS adaptive receiver along with the DFC structure provides a better bit synchronization capability to the over all system. Since the receiver is near-far resistant, the LMS adaptive receiver along with the decision feedback cancellation structure also performs better in the presence of Rayleigh fading. / Graduation date: 1998

IS-95, an interim standard proposed for future digital personal communications systems, uses two levels of encoding of digital data for error control and compatibility with code-division multiple access (CDMA) transmission. The data is first convolutionally encoded and the resulting symbols are interleaved and then groups are encoded as orthogonal Walsh sequences. Decoding these two separate encodings is traditionally done in separate sequential steps. By combining the decoding and applying feedback of the final decision of the second level of decoding to the first level decoder it is possible to reduce the error rate of the decoder. Each Walsh sequence encodes six non-adjacent symbols of the convolutional code. The receiver computes an estimate of the probability that each of the sixty-four possible Walsh sequences has been sent, and uses this estimate as an estimate for each of the convolution symbols which specified the Walsh sequence. Since the convolution symbols are non-adjacent, it is likely that the actual value of some of the earlier symbols will have been determined by the final decoder before later symbols specifying the same Walsh sequence are used by the convolution decoder. The knowledge of the values of these symbols can be used to adjust the probability estimates for that Walsh sequence, improving the likelihood that future convolutional symbols will be correctly decoded. Specific metrics for estimating probabilities that each convolutional symbol was sent were tested with and without the proposed feedback, and error rates were estimated based on extensive computer simulations. It was found that applying feedback does improve error rates. Analytical methods were also applied to help explain the effects. / Graduation date: 1996

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): R. Clark Robertson, Tri T. Ha. Includes bibliographical references (p. 83-84). Also available online.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 111-117). Also available in electronic version. Access restricted to campus users.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, March 2004. / Thesis advisor(s): Geoffrey Xie, John Gibson. Includes bibliographical references (p. 151-152). Also available online.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 117-140).