Co-channel interference reduction in Optical Code Division Multiple Access systems

In this thesis few new code sets and a multi-user interference (MUI) cancellation scheme have been proposed for Optical Code Division Multiple Access (OCDMA) systems, which can be employed in the next generation of global communication networks to enhance their existing systems’ performance dramatically. The initial evaluation of the proposed code sets shows that their implementation improves the performance, decreases the BER and increases security considerably. Also the proposed MUI cancellation scheme totally removes all the cross-talk and interference between the active users within the network. These novel schemes and codes can be easily implemented in the optical packet switched networks. Optical switching has the ability of bandwidth manipulation at the wavelength level (e.g. with optical circuit/packet/burst switching); the capability to accommodate a wide range of traffic distributions, and also to make dynamic resource reservations possible. This thesis first gives a brief overview of co-channel interference reduction in OCDMA networks, then proposes two novel code sets, Uniform Cross-Correlation Modified Prime Code (UC-MPC) and Transposed UC-MPC (T-UCMPC), along with their evaluation and analysis in various systems, including IP routing over an OCDMA network. Thereafter, the new MUI cancellation scheme is proposed and then the proposed code sets and the MUI cancellation scheme are implemented and analysed in a laboratory-based experimental test bed. Finally the conclusion of this research is discussed

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

THE USE OF TUNED FRONT END OPTICAL RECEIVER AND PULSE POSITION MODULATION

The aim of this work is to investigate the use of tuned front-ends with OOK and PPM schemes, in addition to establish a theory for baseband tuned front end receivers. In this thesis, a background of baseband receivers, tuned receivers, and modulation schemes used in baseband optical communication is presented. Also, the noise theory of baseband receivers is reviewed which establishes a grounding for developing the theory relating to optical baseband tuned receivers. This work presents novel analytical expressions for tuned transimpedance, tuned components, noise integrals and equivalent input and output noise densities of two tuned front-end receivers employing bi-polar junction transistors and field effect transistors as the input. It also presents novel expressions for optimising the collector current for tuned receivers. The noise modelling developed in this work overcomes some limitations of the conventional noise modelling and allows tuned receivers to be optimised and analysed. This work also provides an in-depth investigation of optical baseband tuned receivers for on-off keying (OOK), Pulse position modulation (PPM), and Di-code pulse position modulation (Di-code PPM). This investigation aims to give quantitative predictions of the receiver performance for various types of receivers with different photodetectors (PIN photodetector and avalanche photodetector), different input transistors (bi-polar junction transistor BJT and field effect transistor FET), different pre-detection filters (1st order low pass filter and 3rd order Butterworth filter), different detection methods, and different tuned configurations (inductive shunt feedback front end tuned A and serial tuned front end tuned B). This investigation considers various optical links such as line of sight (LOS) optical link, non-line of sight (NLOS) link and optical fibre link. All simulations, modelling, and calculations (including: channel modelling, receiver modelling, noise modelling, pulse shape and inter-symbol interference simulations, and error probability and receiver calculations) are performed by using a computer program (PTC Mathcad prime 4, version: M010/2017) which is used to evaluate and analyse the performance of these optical links. As an outcome of this investigation, noise power in tuned receivers is significantly reduced for all examined configurations and under different conditions compared to non-tuned receivers. The overall receiver performance is improved by over 3dB in some cases. This investigation provides an overview and demonstration of cases where tuned receiver can be optimised for baseband transmission, offering a much better performance compared to non-tuned receivers. The performance improvement that tuned receivers offers can benefit a wide range of optical applications. This investigation also addresses some recommendations and suggestions for further work in some emerging applications such as underwater optical wireless communication (UOWC), visible light communication (VLC), and implantable medical devices (IMD). Keyword: Optical communications, Baseband receivers, Noise modelling, tuned front end, pulse position modulation (PPM)

Phase-Modulations Analyses in Coherent Homodyne Optical CDMA Network Using a Novel Prime Code Family

Abstract — This paper examines the bit-error rate (BER) for an optical direct-detection code-division multiple-access (OCDMA) system employing a novel prime code family, hereby referred to as ‘Double-Padded Modified Prime Code (DPMPC) ’ for the spreading and de-spreading operations in addition to coherent homodyne dual-balanced detection. As a coherent modulation, binary phase-shift keying (BPSK) format is deployed where the phase is modulated by either an external phase-modulator or injection-locking methods. The phase limitation and the performance for both phase-modulations including multiple access interferences (MAI) in a shot-noise limited regime are studied and moderate penalty associated with the limited phase excursion is revealed. Index Terms—Coherent balanced-detection, injection-locking, limited phase excursion, multiple access interference (MAI), optical code-division multiple-access (OCDMA). I

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion