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Power consumption requires critical consideration during system design for portable wireless communication devices as it has a direct influence on the battery weight and volume required for operation. Wideband Code Division Multiple Access (W-CDMA) techniques are favoured for use in future generation mobile communication systems. This thesis investigates novel low power techniques for use in system blocks within a W-CDMA adaptive linear minimum mean squared error (LMMSE) receiver architecture. Two low power techniques are presented for reducing power dissipation in the LMS adaptive filter, this being the main power consuming block within this receiver. These low power techniques are namely the decorrelating transform, this is a differential coefficient technique, and the variable length update algorithm which is a dynamic tap-length optimisation technique. The decorrelating transform is based on the principle of reducing the wordlength of filter coefficients by using the computed difference between adjacent coefficients in calculation of the filter output. The effect of reducing the wordlength of filter coefficients being presented to multipliers in the filter is a reduction in switching activity within the multiplier thus reducing power consumed. In the case of the LMS adaptive filter, with coefficients being continuously updated, the decorrelating transform is applied to these calculated coefficients with minimal hardware or computational overhead. The correlation between filter coefficients is exploited to achieve a wordlength reduction from 16 bits down to 10 bits in the FIR filter block. The variable length update algorithm is based on the principle of optimising the number of operational filter taps in the LMS adaptive filter according to operating conditions. The number of taps in operation can be increased or decreased dynamically according to the mean squared error at the output of the filter. This algorithm is used to exploit the fact that when the SNR in the channel is low the minimum mean squared error of the short equaliser is almost the same as that of the longer equaliser. Therefore, minimising the length of the equaliser will not result in poorer MSE performance and there is no disadvantage in having fewer taps in operation. If fewer taps are in operation then switching will not only be reduced in the arithmetic blocks but also in the memory blocks required by the LMS algorithm and FIR filter process. This reduces the power consumed by both these computation intensive functional blocks. Power results are obtained for equaliser lengths from 73 to 16 taps and for operation with varying input SNR. This thesis then proposes that the variable length LMS adaptive filter is applied in the adaptive LMMSE receiver to create a low power implementation. Power consumption in the receiver is reduced by the dynamic optimisation of the LMS receiver coefficient calculation. A considerable power saving is seen to be achieved when moving from a fixed length LMS implementation to the variable length design. All design architectures are coded in Verilog hardware description language at register transfer level (RTL). Once functional specification of the design is verified, synthesis is carried out using either Synopsys DesignCompiler or Cadence BuildGates to create a gate level netlist. Power consumption results are determined at the gate level and estimated using the Synopsys DesignPower tool.

An overwhelming number of models in the literature use average inter-cell interference for the calculation of capacity of a Code Division Multiple Access (CDMA) network. The advantage gained in terms of simplicity by using such models comes at the cost of rendering the exact location of a user within a cell irrelevant. We calculate the actual per-user interference and analyze the effect of user-distribution within a cell on the capacity of a CDMA network. We show that even though the capacity obtained using average interference is a good approximation to the capacity calculated using actual interference for a uniform user distribution, the deviation can be tremendously large for non-uniform user distributions. Call admission control (CAC) algorithms are responsible for efficient management of a network's resources while guaranteeing the quality of service and grade of service, i.e., accepting the maximum number of calls without affecting the quality of service of calls already present in the network. We design and implement global and local CAC algorithms, and through simulations compare their network throughput and blocking probabilities for varying mobility scenarios. We show that even though our global CAC is better at resource management, the lack of substantial gain in network throughput and exponential increase in complexity makes our optimized local CAC algorithm a much better choice for a given traffic distribution profile.

Approved for public release; distribution is unlimited / Establishing a full-duplex underwater network, researching and applying a CDMA protocol to this network, providing a recommendation for a full-duplex underwater network and providing recommendations for using CDMA to increase the efficiency of this network are the general scope of this thesis. A connection that allows traffic in both directions simultaneously underwater is the example of fullduplex communication. Compared to a half duplex configuration, the full duplex network underwater may provide a better networking environment. Currently, most Underwater Acoustic Networks (UANs) still utilize half-duplex network communication. CDMA is the third kind of channel partitioning protocol. Most of the wireless communication devices utilize different kinds of CDMA protocol as a reliable and faster communication. The research conducted in establishing a full-duplex UAN using CDMA may provide reliable and faster communication compared to half-duplex. / Lieutenant Junior Grade, Turkish Navy

Approved for public release, distribution is unlimited / Presently, the uniform linear array (ULA) is the most commonly used antenna system for a sectorized cell system like the commercial cellular systems. However, in many omni-directional cell communication systems, such as the ground-based military communications, interest in using the uniform circular array (UCA) has greatly increased. This thesis examines the use of an equally-spaced circular adaptive antenna array at the mobile station for a typical coded direct sequence code division multiple access (DS-CDMA) communication system. This thesis analyzed the performance of a randomly orientated adaptive UCA in the forward channel (base station to mobile station) of a coded multi-cell DS-CDMA system. Using a 3- and 4-element UCA, the ca-pacity and performance of different cellular systems under a range of shadowing conditions, with and without an-tenna sectoring at the base station, and various user capacities were simulated using the Monte Carlo simulation. The results for both ULA, as studied in [7], and UCA were compared and presented in this thesis. / http://hdl.handle.net/10945/1064 / Civilian, Defence Science and Technology Agency (Singapore)

Approved for public release, distribution is unlimited / This thesis examines a circular adaptive antenna array used at the mobile station for a typical Direct Sequence Code Division Multiple Access (DS-CDMA) cellular mobile communications system. The primary objective is to reduce co-channel interference of a wideband CDMA cellular network under a multi-path fading environment. We analyzed the performance of a randomly positioned mobile terminal with a randomly orientated adaptive antenna array in the forward channel (base-station to mobile) of a multi-cell DS-CDMA system and established four performance boundaries. A single complex circular adaptive weight in each element channel of a circular adaptive array sufficiently processes narrowband signals. However, in order to process broadband signals, a tapped-delay line (transveral filter) is required. This tapped-delay line is employed because it can adjust the frequency dependent amplitude and phase. The performance of a DS-CDMA cellular system with a mobile terminal equipped with a circular array and a tapped-delay line is analyzed. It has been demonstrated that the optimization process has been extremely computationally expensive and hence minimum taps should be used for practical considerations. The results illustrated that, in general, for a four-element circular array system, a two tapped-delay line would be sufficient to equalize the broadband signal while providing a similar performance level to that of a narrow-band adaptive array system. / http://hdl.handle.net/10945/1080 / Major, Republic of Singapore Air Force

Ma Wing Kin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. 150-155). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

by Siu-Lung Hui, Freeman. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 64-[67]). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Use of Antenna Arrays in Mobile Communications --- p.1 / Chapter 1.1.1 --- Overview --- p.1 / Chapter 1.1.2 --- Beamforming --- p.2 / Chapter 1.2 --- DS/CDMA System s and Multiple Access Interferences --- p.4 / Chapter 1.3 --- Multiuser Detection Schemes --- p.7 / Chapter 1.4 --- Outline of Thesis --- p.11 / Chapter 2 --- A Blind Adaptive Receiver with Antenna Arrays and M-ary Orthogonal Data Signals --- p.13 / Chapter 2.1 --- Introduction --- p.13 / Chapter 2.2 --- System Model --- p.15 / Chapter 2.3 --- Eigen-Analysis Algorithm --- p.21 / Chapter 2.4 --- Simulation Results --- p.92 / Chapter 2.5 --- Adaptive Algorithm --- p.27 / Chapter 2.6 --- Summary --- p.30 / Chapter 3 --- Detection with the Use of the Two-Stage Spreading Scheme --- p.32 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- System Model --- p.34 / Chapter 3.3 --- Blind Beamforming --- p.36 / Chapter 3.4 --- Blind Adaptive Multiuser Detection without Antenna Arrays --- p.38 / Chapter 3.4.1 --- Stochastic Gradient Descent Algorithm --- p.40 / Chapter 3.4.2 --- Alternative Matrix Approach --- p.41 / Chapter 3.5 --- Theoretical Combined Receiver Model --- p.41 / Chapter 3.6 --- Practical Implementation of the Receiver --- p.50 / Chapter 3.6.1 --- Combined Scheme with Adaptive Algorithms --- p.50 / Chapter 3.6.2 --- Simplified Structure --- p.52 / Chapter 3.7 --- Summary --- p.54 / Chapter 4 --- Conclusions and Future Work --- p.55 / Chapter A --- Correlation Properties --- p.58 / Chapter B --- Adaptive Algorithm --- p.62 / Bibliography --- p.64

Hu Fan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 77-81). / Abstracts in English and Chinese. / Acknowledgement --- p.i / Abstract --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Evolution of Mobile Communications --- p.1 / Chapter 1.2 --- Overview of Multicarrier Systems --- p.3 / Chapter 1.3 --- Outline of This Thesis --- p.5 / Chapter 2 --- Multicarrier Communication Systems --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Multicarrier Modulation (MCM) Scheme versus Single Carrier Modulation (SCM) Scheme --- p.8 / Chapter 2.3 --- Orthogonal Frequency Division Multiplexing (OFDM) Systems --- p.12 / Chapter 2.4 --- Multicarrier CDMA --- p.16 / Chapter 2.4.1 --- MC-CDMA --- p.17 / Chapter 2.4.2 --- MC-DS-CDMA --- p.18 / Chapter 2.4.3 --- MT-CDMA --- p.19 / Chapter 3 --- Optimization for MC-CDMA Systems --- p.22 / Chapter 3.1 --- System Model --- p.22 / Chapter 3.2 --- Optimization with Normalized Power --- p.27 / Chapter 3.2.1 --- Transmission Time Minimization --- p.27 / Chapter 3.2.2 --- Throughput Maximization --- p.32 / Chapter 3.2.3 --- Performance --- p.33 / Chapter 3.3 --- Mathematical Programming --- p.36 / Chapter 3.3.1 --- Nonlinear Programming --- p.37 / Chapter 3.3.2 --- Convex Programming --- p.39 / Chapter 3.4 --- Optimization with Power Allocation --- p.42 / Chapter 3.4.1 --- Transmission Time Minimization with Power Allocation --- p.42 / Chapter 3.4.2 --- Throughput Maximization with Power Allocation --- p.43 / Chapter 3.4.3 --- Power Minimization --- p.44 / Chapter 3.5 --- Long-range Optimization --- p.45 / Chapter 3.5.1 --- Long-range Transmission Time Minimization --- p.46 / Chapter 3.5.2 --- Long-range Throughput Maximization --- p.50 / Chapter 3.5.3 --- Long-range Power Minimization --- p.51 / Chapter 3.5.4 --- Performance --- p.53 / Chapter 4 --- Joint Scheduling and Resource Allocation --- p.58 / Chapter 4.1 --- Queueing Model --- p.58 / Chapter 4.2 --- Problem Formulation --- p.62 / Chapter 4.3 --- Suboptimal Algorithm --- p.64 / Chapter 4.4 --- Performance --- p.69 / Chapter A --- Convexity Proof of Problem (3.32) --- p.73 / Chapter B --- Convexity Proof of Problem (3.36) --- p.75 / Bibliography --- p.77

by Yooh Ji Heng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 119-128). / Appendix in Chinese. / Chapter I --- Synchronization of Multi-carrier CDMA Signals --- p.1 / Chapter 1 --- Introduction --- p.2 / Chapter 1.1 --- Spread Spectrum CDMA --- p.4 / Chapter 1.1.1 --- Direct Sequence/SS-CDMA --- p.5 / Chapter 1.1.2 --- Frequency Hopping/SS-CDMA --- p.5 / Chapter 1.1.3 --- Pseudo-noise Sequence --- p.6 / Chapter 1.2 --- Synchronization for CDMA signal --- p.7 / Chapter 1.2.1 --- Acquisition of PN Sequence --- p.7 / Chapter 1.2.2 --- Phase Locked Loop --- p.8 / Chapter 2 --- Multi-carrier CDMA --- p.10 / Chapter 2.1 --- System Model --- p.11 / Chapter 2.2 --- Crest Factor --- p.12 / Chapter 2.3 --- Shapiro-Rudin Sequence --- p.14 / Chapter 3 --- Synchronization and Detection by Line-Fitting --- p.16 / Chapter 3.1 --- Unmodulated Signals --- p.16 / Chapter 3.2 --- Estimating the Time Shift by Line-Fitting --- p.19 / Chapter 3.3 --- Modulated Signals --- p.22 / Chapter 4 --- Matched Filter --- p.23 / Chapter 5 --- Performance and Conclusion --- p.27 / Chapter 5.1 --- Line Fitting Algorithm --- p.27 / Chapter 5.2 --- Matched Filter --- p.28 / Chapter 5.3 --- Conclusion --- p.30 / Chapter II --- Security on Internet --- p.31 / Chapter 6 --- Introduction --- p.32 / Chapter 6.1 --- Introduction to Cryptography --- p.32 / Chapter 6.1.1 --- Classical Cryptography --- p.33 / Chapter 6.1.2 --- Cryptanalysis --- p.35 / Chapter 6.2 --- Introduction to Internet Security --- p.35 / Chapter 6.2.1 --- The Origin of Internet --- p.35 / Chapter 6.2.2 --- Internet Security --- p.36 / Chapter 6.2.3 --- Internet Commerce --- p.37 / Chapter 7 --- Elementary Number Theory --- p.39 / Chapter 7.1 --- Finite Field Theory --- p.39 / Chapter 7.1.1 --- Euclidean Algorithm --- p.40 / Chapter 7.1.2 --- Chinese Remainder Theorem --- p.40 / Chapter 7.1.3 --- Modular Exponentiation --- p.41 / Chapter 7.2 --- One-way Hashing Function --- p.42 / Chapter 7.2.1 --- MD2 --- p.43 / Chapter 7.2.2 --- MD5 --- p.43 / Chapter 7.3 --- Prime Number --- p.44 / Chapter 7.3.1 --- Listing of Prime Number --- p.45 / Chapter 7.3.2 --- Primality Testing --- p.45 / Chapter 7.4 --- Random/Pseudo-Random Number --- p.47 / Chapter 7.4.1 --- Examples of Random Number Generator --- p.49 / Chapter 8 --- Private Key and Public Key Cryptography --- p.51 / Chapter 8.1 --- Block Ciphers --- p.51 / Chapter 8.1.1 --- Data Encryption Standard (DES) --- p.52 / Chapter 8.1.2 --- International Data Encryption Algorithm (IDEA) --- p.54 / Chapter 8.1.3 --- RC5 --- p.55 / Chapter 8.2 --- Stream Ciphers --- p.56 / Chapter 8.2.1 --- RC2 and RC4 --- p.57 / Chapter 8.3 --- Public Key Cryptosystem --- p.58 / Chapter 8.3.1 --- Diffie-Hellman --- p.60 / Chapter 8.3.2 --- Knapsack Algorithm --- p.60 / Chapter 8.3.3 --- RSA --- p.62 / Chapter 8.3.4 --- Elliptic Curve Cryptosystem --- p.63 / Chapter 8.3.5 --- Public Key vs. Private Key Cryptosystem --- p.64 / Chapter 8.4 --- Digital Signature --- p.65 / Chapter 8.4.1 --- ElGamal Signature Scheme --- p.66 / Chapter 8.4.2 --- Digital Signature Standard (DSS) --- p.67 / Chapter 8.5 --- Cryptanalysis to Current Cryptosystems --- p.68 / Chapter 8.5.1 --- Differential Cryptanalysis --- p.68 / Chapter 8.5.2 --- An Attack to RC4 in Netscapel.l --- p.69 / Chapter 8.5.3 --- "An Timing Attack to Diffie-Hellman, RSA" --- p.71 / Chapter 9 --- Network Security and Electronic Commerce --- p.73 / Chapter 9.1 --- Network Security --- p.73 / Chapter 9.1.1 --- Password --- p.73 / Chapter 9.1.2 --- Network Firewalls --- p.76 / Chapter 9.2 --- Implementation for Network Security --- p.79 / Chapter 9.2.1 --- Kerberos --- p.79 / Chapter 9.2.2 --- Privacy-Enhanced Mail (PEM) --- p.80 / Chapter 9.2.3 --- Pretty Good Privacy (PGP) --- p.82 / Chapter 9.3 --- Internet Commerce --- p.83 / Chapter 9.3.1 --- Electronic Cash --- p.85 / Chapter 9.4 --- Internet Browsers --- p.87 / Chapter 9.4.1 --- Secure NCSA Mosaic --- p.87 / Chapter 9.4.2 --- Netscape Navigator --- p.89 / Chapter 9.4.3 --- SunSoft HotJava --- p.91 / Chapter 10 --- Examples of Electronic Commerce System --- p.94 / Chapter 10.1 --- CyberCash --- p.95 / Chapter 10.2 --- DigiCash --- p.97 / Chapter 10.3 --- The Financial Services Technology Consortium --- p.98 / Chapter 10.3.1 --- Electronic Check Project --- p.99 / Chapter 10.3.2 --- Electronic Commerce Project --- p.101 / Chapter 10.4 --- FirstVirtual --- p.103 / Chapter 10.5 --- Mondex --- p.104 / Chapter 10.6 --- NetBill --- p.106 / Chapter 10.7 --- NetCash --- p.108 / Chapter 10.8 --- NetCheque --- p.111 / Chapter 11 --- Conclusion --- p.113 / Chapter A --- An Essay on Chinese Remainder Theorem and RSA --- p.115 / Bibliography --- p.119