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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

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Robert J. McLaughlin. / "This report is based on a thesis submitted to the Department of Electrical Engineering, M.I.T., June 1958, in partial fulfillment of the requirements for the degree of Master of Science." / Bibliography: p. 33. / Army Signal Corps Contract DA36-039-sc-78108. Dept. of the Army Task 3-99-20-001 and Project 3-99-00-000.

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The radio interface greatly affects performance of wireless communication systems. Hard-wired communication links use transmission lines to connect communication terminals. The propagation characteristics of radio frequency signals on these transmission lines are well known. In wireless communication systems, however, the transmission line with a known impulse response is replaced by a radio channel with an impulse response that is constantly changing as the users roam throughout the coverage area. The varying impulse response is due to the multiple path propagation of the signals from the transmitter to the receiver. The design of emerging small cellular (commonly known as microcellular) wireless systems is limited by the multipath propagation characteristics of the channel. Once these propagation conditions are understood, systems may be designed more efficiently in terms of cell layout, interference reduction, and system performance. This thesis presents a technique for automated propagation prediction in outdoor microcellular radio channels using ray tracing. The basic method is to integrate site-specific environmental data with a geometrical optics model to trace the propagation of energy from the transmitter to the receiver. Software written in C++ is used to automatically trace rays that are reflected, transmitted, scattered, or diffracted as they propagate through the channel. The automated software uses AutoCAD® to maintain the site-specific building data incorporated into the model. Details of the building database, propagation model, and software implementation are included in this thesis. The accuracy of the model and its software implementation is tested against wide band measurements taken on the Virginia Tech campus. Results, included here, indicate that the received signal can be accurately predicted in both line-of-sight and obstructed microcell topographies. / Master of Science

The surest way to increase the capacity of a wireless system is by getting the transmitters and receivers closer to each other, which creates the dual bene¯ts of higher quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hotspots, distributed antennas, or relays. Compared to these deployments, a less expensive alternative for cellular operators is the recent concept of femtocells { also called home base-stations { which are end consumer installed data access points in the desire to get better indoor voice and data coverage. A two-tier network consisting of a conventional macrocell overlaid with shorter range wireless hotspots o®ers poten- tial capacity bene¯ts with low upfront costs to cellular operators. This dissertation addresses the key technical challenges inherent to a femtocell-aided cellular network, speci¯cally managing radio interference and providing reliable coverage at either tier, for di®erent physical layer technologies. Speci¯c contributions include 1) an uplink capacity analysis and interference avoidance in two-tier networks employing Code Di- vision Multiple Access (CDMA), 2) a decentralized power control scheme in two-tier networks with universal frequency reuse, 3) a coverage analysis of multi-antenna two- tier networks, and 4) spectrum allocation in two-tier networks employing Orthogonal Frequency Division Multiple Access (OFDMA). The goal of this research is to inspire and motivate the use of decentralized interference management techniques requir- ing minimal network overhead in ongoing and future deployments of tiered cellular architectures. / text

M.Ing. / The increase of interest in the development of radio communications, both terrestrial and satellite is reaching far and beyond the most optimistic expectations. There has been an accelerated emergence of newer technologies, all claiming highly coveted radio frequency spectrum resources. With the push for the development of location based services, utilizing satellite com- communications for military purposes and later for civilian use; there has been a parallel development in terrestrial communications technology making it possible to implement cost efficient reliable user systems for voice and data services ...

Shen Fangzhong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 55-57). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iii / List of Figures --- p.vi / List of Tables --- p.ix / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Motivation --- p.1 / Chapter 1.2. --- Related Work --- p.2 / Chapter 1.3. --- Our Work --- p.2 / Chapter 1.4. --- Some Assumptions --- p.2 / Chapter 1.4.1. --- Beamforming --- p.2 / Chapter 1.4.2. --- Downlink Channel --- p.2 / Chapter 1.4.3. --- Single Cell --- p.3 / Chapter 1.5. --- Thesis Road Map --- p.3 / Chapter Chapter 2. --- Preliminaries of Cell Sectoring --- p.4 / Chapter 2.1. --- Introduction --- p.4 / Chapter 2.2. --- Beamforming --- p.4 / Chapter 2.2.1. --- Linear Array --- p.5 / Chapter 2.2.2. --- Circular Array --- p.8 / Chapter 2.2.3. --- Butler Beamforming Network --- p.9 / Chapter 2.2.4. --- Dynamic Beamforming --- p.10 / Chapter 2.3. --- Power Control --- p.16 / Chapter Chapter 3. --- Dynamic Cell Sectoring --- p.19 / Chapter 3.1. --- Introduction --- p.19 / Chapter 3.2. --- Minimum Total Transmission Power sectoring --- p.21 / Chapter 3.2.1. --- Problem Statement --- p.21 / Chapter 3.2.2. --- Shortest Path Problem Formulation --- p.23 / Chapter 3.2.3. --- Shortest Path Algorithm and Complexity --- p.26 / Chapter 3.2.4. --- Graph Reduction --- p.28 / Chapter 3.2.5. --- Example --- p.30 / Chapter 3.3. --- Power Equalization Sectoring --- p.33 / Chapter 3.3.1. --- Relationship Between MinTTP Sectoring and PE Sectoring --- p.33 / Chapter 3.3.2. --- Power Equalization Sectoring Algorithm --- p.36 / Chapter 3.4. --- Numerical Results --- p.37 / Appendix --- p.44 / Chapter Chapter 4. --- Resectoring Algorithms --- p.46 / Chapter 4.1. --- Introduction --- p.46 / Chapter 4.2. --- Nyquist Sampling Theorem --- p.47 / Chapter 4.3. --- MinTTP Resectoring --- p.47 / Chapter 4.4. --- PE Resectoring --- p.43 / Chapter 4.5. --- Handoff --- p.48 / Chapter 4.5.1. --- Handoff Load --- p.49 / Chapter 4.6. --- Performance --- p.49 / Chapter Chapter 5. --- Conclusion and Future Work --- p.53 / Chapter 5.1. --- Thesis Summary --- p.53 / Chapter 5.2. --- Future Work --- p.54 / Bibliography --- p.55

Cheung Shun Keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 80-83). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The Problem --- p.1 / Chapter 1.2 --- Overview of CDMA --- p.2 / Chapter 1.3 --- Problems Encountered in Direct-Sequence (DS)CDMA --- p.3 / Chapter 1.3.1 --- Multipath Fading Scenario in DS-CDMA Cellular Mo- bile Communication --- p.3 / Chapter 1.3.2 --- Near-Far Problem --- p.4 / Chapter 1.4 --- Delimitation and Significance of the Thesis --- p.5 / Chapter 1.5 --- Summary --- p.7 / Chapter 1.6 --- Scope of the Thesis --- p.8 / Chapter 2 --- Literature Review of Blind Space-Time Processing in a wire- less CDMA Receiver --- p.9 / Chapter 2.1 --- General Background Information --- p.9 / Chapter 2.1.1 --- Time Model of K-User Chip-Synchronous CDMA --- p.9 / Chapter 2.1.2 --- Dispersive Channel Modelling --- p.10 / Chapter 2.1.3 --- Combination of K-user CDMA Time Model with the Slow Frequency-Selective Fading Channel Model to form a completed Chip-Synchronous CDMA Time Model --- p.13 / Chapter 2.1.4 --- Spatial Channel Model with Antenna Array [9] --- p.15 / Chapter 2.1.5 --- Joint Space-Time Channel Model in Chip-Synchronous CDMA --- p.19 / Chapter 2.1.6 --- Challenges to Blind Space-Time Processing in a base- station CDMA Receiver --- p.23 / Chapter 2.2 --- Literature Review of Single-User-Type Detectors used in Blind Space-Time DS-CDMA RAKE Receivers --- p.25 / Chapter 2.2.1 --- A Common Problem among the Signal Processing Schemes --- p.28 / Chapter 3 --- "Novel ""Self-Decorrelation"" Technique" --- p.29 / Chapter 3.1 --- "Problem with ""Blind"" Space-Time RAKE Processing Using Single- User-Type Detectors" --- p.29 / Chapter 3.2 --- "Review of Zoltowski & Ramos[10,11,12] Maximum-SINR Single- User-Type CDMA Blind RAKE Receiver Schemes" --- p.31 / Chapter 3.2.1 --- Space-Time Data Model --- p.31 / Chapter 3.2.2 --- The Blind Element-Space-Only (ESO) RAKE Receiver with Self-Decorrelation Pre-processing Applied --- p.32 / Chapter 3.3 --- Physical Meaning of Self-Decorrelation Pre-processing --- p.35 / Chapter 3.4 --- Simulation Results --- p.38 / Chapter 4 --- """Fractional Self-Decorrelation"" Pre-processing" --- p.45 / Chapter 4.1 --- The Blind Maximum-SINR RAKE Receivers in Chen et. al.[l] and Wong et. al.[2] --- p.45 / Chapter 4.2 --- Fractional Self-Decorrelation Pre-processing --- p.47 / Chapter 4.3 --- The Blind Element-Space-Only (ESO) RAKE Receiver with Fractional Self-Decorrelation Pre-processing Applied --- p.50 / Chapter 4.4 --- Physical Meaning of Fractional Self-Decorrelation Pre-processing --- p.54 / Chapter 4.5 --- Simulation Results --- p.55 / Chapter 5 --- Complexity Analysis and Schematics of Proposed Techniques --- p.64 / Chapter 5.1 --- Computational Complexity --- p.64 / Chapter 5.1.1 --- Self-Decorrelation Applied in Element-Space-Only (ESO) RAKE Receiver --- p.64 / Chapter 5.1.2 --- Fractional Self-Decorrelation Applied in Element-Space- Only (ESO) RAKE Receiver --- p.67 / Chapter 5.2 --- Schematics of the Two Proposed Techniques --- p.69 / Chapter 6 --- Summary and Conclusion --- p.74 / Chapter 6.1 --- Summary of the Thesis --- p.74 / Chapter 6.1.1 --- The Self-Decorrelation Pre-processing Technique --- p.75 / Chapter 6.1.2 --- The Fractional Self-Decorrelation Pre-processing Tech- nique --- p.76 / Chapter 6.2 --- Conclusion --- p.78 / Chapter 6.3 --- Future Work --- p.78 / Bibliography --- p.80 / Chapter A --- Generalized Eigenvalue Problem --- p.84 / Chapter A.1 --- Standard Eigenvalue Problem --- p.84 / Chapter A.2 --- Generalized Eigenvalue Problem --- p.84