Tse Hok Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 68-69). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background Study --- p.4 / Chapter 2.1 --- Channel Assignment in Multicarrier CDMA Systems --- p.4 / Chapter 2.1.1 --- Channel Throughput --- p.5 / Chapter 2.1.2 --- Greedy Approach to Channel Assignment --- p.6 / Chapter 2.2 --- Generalised Assignment Problem --- p.7 / Chapter 2.2.1 --- Branch and Bound Approach for GAP --- p.8 / Chapter 2.2.2 --- Genetic Algorithm for GAP --- p.10 / Chapter 2.3 --- Negative Cycle Detection --- p.11 / Chapter 2.3.1 --- Labeling Method --- p.11 / Chapter 2.3.2 --- Bellman-Ford-Moore algorithm --- p.13 / Chapter 2.3.3 --- Amortized Search --- p.14 / Chapter 3 --- Multi-objective Assignment Problem --- p.15 / Chapter 3.1 --- Multi-objective Assignment Problem --- p.16 / Chapter 3.2 --- NP-Hardness --- p.18 / Chapter 3.3 --- Transformation of the Multi-objective Assignment Problem --- p.19 / Chapter 3.4 --- Algorithm --- p.23 / Chapter 3.5 --- Example --- p.25 / Chapter 3.6 --- A Special Case - Linear Objective Function --- p.32 / Chapter 3.7 --- Performance on the assignment problem --- p.33 / Chapter 4 --- Goal Programming Model for Channel Assignment Problem --- p.35 / Chapter 4.1 --- Motivation --- p.35 / Chapter 4.2 --- System Model --- p.36 / Chapter 4.3 --- Goal Programming Model for Channel Assignment Problem --- p.38 / Chapter 4.4 --- Simulation --- p.39 / Chapter 4.4.1 --- Throughput Optimization --- p.40 / Chapter 4.4.2 --- Best-First-Assign Algorithm --- p.41 / Chapter 4.4.3 --- Channel Swapping Algorithm --- p.41 / Chapter 4.4.4 --- Lower Bound --- p.43 / Chapter 4.4.5 --- Result --- p.43 / Chapter 4.5 --- Future Works --- p.50 / Chapter 5 --- Extended Application on the General Problem --- p.51 / Chapter 5.1 --- Latency Minimization --- p.52 / Chapter 5.2 --- Generalised Assignment Problem --- p.53 / Chapter 5.3 --- Quadratic Assignment Problem --- p.60 / Chapter 6 --- Conclusion --- p.65 / Bibliography --- p.67

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 88-91). Also available via the Internet.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [111]-119).

Code division multiple access (CDMA) is a well-known radio communication technique that allows multiple users to share the same spectrum simultaneously. It is an alternative to frequency division and time division multiple access scheme. Its numerous advantages have merited being the main air-interface choice for the third generation (3G) mobile communication system. Nevertheless, due to the use of same frequency, the capacity of CDMA air-interface is interference limited. This problem is minimised by use of power control scheme. Power Control reduces the interference in the system by adjusting the transmitted power according to the received Signal-to-Interference (SIR) ratio. The main difficulty to achieve this scheme is that mobile terminals experience different radio propagation channel. For success completion of this task, two objectives have been identified for power control. First assure that the received signal matches the required SIR at physical layer and secondly adjust the required SIR of users at system layer to an acceptable value so that the terminals in the system are capable of achieving. In this thesis both objectives are discussed and analysed through analytical and simulation methods. At physical layer, two analytical methods based on non-linear control theory are proposed to combat the fast fading channel propagation. The proposed methods are a fast solution to assess the performance of the Closed Loop Power Control compared to the usual lengthy simulation process. At system level, a new distributed power algorithm for reverse link that adjusts the SIR target of the mobile terminal at the base station is proposed. This algorithm brings the performance of the distributed algorithm closer to the optimal solution provided by the non-feasible centralised power control algorithm in current technology.

The goal for the third generation (3G) of mobile communications system is to seamlessly integrate a wide variety of communication services such as high-speed data, video and multimedia traffic as well as voice signals for transmission on a Wideband Code Division Multiple Access (WCDMA) air interface. CDMA suffers from interference and in this thesis multiuser detection for the mobile uplink has been considered. A thorough comparative study for different multiuser detection methods is done. RAKE-IC as an architecture for mixing the ideas of RAKE receiver, and parallel Interference Cancellation, are introduced. The basic concept is to maximize the signal to noise ratio of all users in the system by using adaptive algorithms. The structure of RAKE-IC has been extended to multi-stages and several adaptive algorithms are implemented. An iterative method for interference cancellation has been considered and its convergence issue has been analytically studied. An improvement in convergence using the Rayleigh-Ritz theorem is proposed which in consequence increases the convergence speed in synchronous scenarios. Using analytical methods another improvement using the Gershgorin theorem has been proposed which does not impose a great complexity in the system, yet works well even in asynchronous environments. A suboptimum search algorithm for correcting the reliable detected information has been introduced with the property that its structure can be combined well with the iterative detectors. This combination achieves a better performance than partial parallel interference cancellation method even in rather low interference regions of operation. The structure of the sub-optimum search algorithm has been extended to multiple stages and its performance in terms of bit error rate has been analytically derived in closed form that shows good agreement with the simulation results. Considering the power profile of the users and by sacrificing a little performance, the suboptimum search structure has been further simplified. Key words: Multiuser Detection, WCDMA and Interference Cancellation.

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The initial code acquisition techniques for direct sequence code division multiple access (DS/CDMA) communication networks are investigated in this thesis. Conventional methods of code acquisition, which are basically based on the auto correlation and cross correlation properties of spreading codes, fail in the presence of multiple access interference (MAI) and the near-far effect. This fact motivates the study for interference resistant acquisition algorithms in the hostile channel environment. Training-based acquisition is investigated and the effect of training sequence structure on acquisition performance is discussed. A new training sequence architecture is proposed which results in a shorter acquisition time. Demands for high bit rate services and needs for more efficient exploitation of resources lead to the study of acquisition algorithms that do not need the preamble or training sequences. In this context, blind adaptive algorithms for code acquisition are investigated. The mismatch problem of blind algorithms is addressed and a novel method of mismatch problem handling for Constraint Minimum Output Energy (C-MOE) is proposed. The algorithm results in good acquisition performance under different channel conditions and system loadings. The idea of joint acquisition and demodulation of data, where the outcome of the acquisition mode is an interference suppressor filter, is also discussed. It is shown that in this class of receivers, a one-step constraint acquisition process is not sufficient for handling both the mismatch problem and exploiting the multi-path diversity. Therefore, a novel receiver is proposed which is able to handle the mismatch problem as well as the channel diversity. This receiver is based on a two- step constraint minimum output energy algorithm and comparatively provides a good acquisition and demodulation performance.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A radiolocation problem using DS-CDMA waveforms with array-based receivers is considered. It is assumed that M snapshots of N(s) Nyquist sample long data are available, with a P element antenna array. In the handshaking radiolocation protocol assumed here, data training sequences are available for all K users. As a result, the received spatial-temporal matrix R ∈ C^(MN(s)x P) is approximated by a sum of deterministic signal matrices S(k)^b ∈ C^(MN(s) N(s)) multiplied by unconstrained array response matrices A(k) ∈ C^(N(s)x P). The unknown delays are not estimated directly. Rather, the delays are implicitly approximated as part of the symbol-length long channel, and solutions sparse in the rows of A are thus sought. The resulting ML cost function is J = ||R - ∑(k=1)^K S(k)^bA(k)||(F). The Generalized Successive Interference Cancellation (GSIC) algorithm is employed to iteratively estimate and cancel multiuser interference. Thus, at the k-th GSIC iteration, the index p(k) = arg min(l ≠ p(1),...,p(k-1)) {min(A(l)) ||R^k-S(l)^bA(l)||(F)} is computed, where R^k = ∑(l=1)^(k-1) S(pl)^bÂ(pl). Matching pursuits is embedded in the GSIC iterations to compute sparse channel/steering vector solutions Â(l). Simulations are presented for DS-CDMA signals received over channels computed using a ray-tracing propagation model.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy