Performance of a Spectrally Encoded Multi-carrier Phase Shift Keying Communications System in a Frequency-Selective, Slowly-Fading Multipath Channel

This research examines the performance of a spectrally encoded, multi-carrier, phase shift keying communications system in a frequency-selective, slowly-fading multipath channel. The specific communications system modeled is the transform domain communication system (TDCS) originally researched as an interference avoidance technique. Previous TDCS research assumed an additive white Gaussian noise channel, which is not representative of a realistic environment. This thesis presents overviews of previous TDCS research, the multipath fading channel, and the RAKE receiver. Analysis and Matlab simulations compare the performance of spectrally encoded and un-encoded signals through a multipath fading channel using an L-diversity TDCS RAKE receiver. Encoded signals take on the spectral shape of the multipath fading channel transfer function. Un-encoded signals have a flat magnitude spectrum. The research also evaluates the interference rejection capability of spectrally encoded signals in a multipath channel. Research results indicate for diversities ranging between 2 and 50, spectrally encoded signals need 1.0 to 2.75dB less transmitted normalized bit energy to noise power spectral density ratios to achieve the same probability of bit error as un-encoded signals. Results also demonstrate that spectrally encoded TDCS signals retain the interference rejection capability

Hardware Realization of a Transform Domain Communication System

The purpose of this research was to implement a Transform Domain Communication System (TDCS) in hardware and compare experimental bit error performance with results published in literature. The intent is to demonstrate the effectiveness or ineffectiveness of a TDCS in communicating binary data across a real channel. In this case, an acoustic channel that is laden with narrowband interference was considered. A TDCS user pair was constructed to validate the proposed design using Matlab™ to control a PC sound card. The proposed TDCS design used the Bartlett method of spectrum estimation, the spectral notching algorithm found in TDCS literature, quadrature phase shift keying, and minimum mean square error transverse equalization to mitigate the effects of noise and intersymbol interference. Water-filling was evaluated as an alternative to spectral notching for performing waveform design and is shown to perform equivalently. Validated software was migrated to code suitable for use onboard a Digital Signal Processor Starter Kit (DSK). Two DSK boards were used, one for transmission and reception, and bit error performance results were obtained. Bit error analysis reveals that the TDCS hardware performs approximately the same as literature suggests

State-of-the-art in Power Line Communications: from the Applications to the Medium

In recent decades, power line communication has attracted considerable attention from the research community and industry, as well as from regulatory and standardization bodies. In this article we provide an overview of both narrowband and broadband systems, covering potential applications, regulatory and standardization efforts and recent research advancements in channel characterization, physical layer performance, medium access and higher layer specifications and evaluations. We also identify areas of current and further study that will enable the continued success of power line communication technology.Comment: 19 pages, 12 figures. Accepted for publication, IEEE Journal on Selected Areas in Communications. Special Issue on Power Line Communications and its Integration with the Networking Ecosystem. 201

Interference Mitigation in WAIC Systems

Advancements in the field of wireless communications in the last few decades have made it an indispensable part of how human made entities, and by extension, humans interact with each other. The inherent lack of the need for significant physical infrastructure brings with it great advantages in terms of mobility, operational and maintenance costs, and overall reliability and flexibility. The characteristics of wireless techniques make for an attractive proposition for enabling operational communications in aircrafts. However, wireless networks bring with them their own set of challenges in terms of range, dependability or susceptibility to interference and security. The main objective of this thesis is to evaluate different wireless communications techniques for their feasibility to be employed as Wireless Avionics Intra-Communications (WAIC) systems. The major hindrance in ensuring reliable communications in this regard comes from the operation of the existing Radio Altimeter systems in the allotted frequency band of 4.2 - 4.4 GHz. WAIC systems based on wireless techniques such as Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiplexing (OFDM) have been simulated in MATLAB for the analysis. The performance of the WAIC systems in the presence of interference from Altimeter signals and Additive White Gaussian Noise (AWGN) has been evaluated and studied

Interference Suppression in Multiple Access Communications Using M-Ary Phase Shift Keying Generated via Spectral Encoding

A conceptual transform domain communication system (TDCS) is shown capable of operating successfully using M-Ary phase shift keying (MPSK) data modulation in a multiple access environment. Using spectral encoding, the conceptual TDCS provides an effective means for mitigating interference affects while achieving multiple access communications. The use of transform domain processing with MPSK data modulation (TD-MPSK) provides higher spectral efficiency relative to other modulation techniques (antipodal signaling and cyclic shift keying) considered previously for TDCS applications. The proposed TD-MPSK technique uses spectral encoding for both data and multiple access phase modulations. Demodulation of the spectrally encoded TD-MPSK communication symbols is accomplished using conventional, multi-channel time domain correlation techniques. Analytic expressions for TD-MPSK probability of symbol error (PE) and probability of bit error (PB) are derived and validated using simulated results over the range of signal-to-noise ratios typically considered for communications. This validation includes scenarios with: 1) multiple access interference, 2) spectral notching, 3) jamming present and 4) combinations of all three. For a J/S of 3.14 dB and a Eb/N0 of 6 dB, PB dropped by up to a factor of 3 for TD-QPSK in a MA environment for the case when spectral notching was present versus the case when spectral notching wasn\u27t present. The cross-correlation between communication symbols of different synchronous users can be made identically zero through proper selection of multiple access phase codes (orthogonal signaling). For a synchronous network containing orthogonal users, PE and PB are unaffected as the number of orthogonal network users increases. For a J/S of 3.14 dB and a Eb/N0 of 6 dB, PB dropped by a factor of 12 for TD-QPSK in a MA environment for the case when spectral notching was present versus the case when spectral notching wasn\u27t present

Wavelet Domain Communication System (WDCS): Packet-Based Wavelet Spectral Estimation and M-ARY Signaling

A recently proposed Wavelet Domain Communication System (WDCS) using transform domain processing demonstrated excellent interference avoidance capability under adverse environmental conditions. This work extends previous results by: 1) incorporating a wavelet packet decomposition technique, 2) demonstrating M-Ary signaling capability, and 3) providing increased adaptivity over a larger class of interference signals. The newly proposed packet-based WDCS is modeled and its performance characterized using MATLAB®. In addition, the WDCS response to two scenarios simulating Doppler effects and physical separation of transceivers are obtained. The fundamental metric for analysis and performance evaluation is bit error rate (Pb). Relative to the previous non-packet WDCS, the proposed packet-based WDCS provides improved/comparable bit error performance in several interference scenarios single-tone, multiple-tone, swept-tone, and partial band interference is considered. Interference avoidance capability was characterized for a bit energy-to-noise power level (Eb/N0) of 4.0 dB and interference energy-to-signal energy (I/E) ratios ranging from 0.0 dB to 16.0 dB. For binary, 4-Ary, and 8-Ary CSK data modulations, the packet-based WDCS exhibited average Pb improvements of 6.7, 9.2, and 12.0 dB, respectively, for partial band and swept-tone interference. For single and multiple-tone interference, improvements of 8.0, 12.4, and 15.7 dB were realized. Furthermore, bit error sensitivity analyses indicate the WDCS communicates effectively under non-ideal real-world conditions (transceivers located in dissimilar environments) while exhibiting average Pb improvements of 5.4, 5.1, and 5.8 dB, relative to systems having no interference suppression

Interference Mitigation in WAIC Systems

Advancements in the field of wireless communications in the last few decades have made it an indispensable part of how human made entities, and by extension, humans interact with each other. The inherent lack of the need for significant physical infrastructure brings with it great advantages in terms of mobility, operational and maintenance costs, and overall reliability and flexibility. The characteristics of wireless techniques make for an attractive proposition for enabling operational communications in aircrafts. However, wireless networks bring with them their own set of challenges in terms of range, dependability or susceptibility to interference and security. The main objective of this thesis is to evaluate different wireless communications techniques for their feasibility to be employed as Wireless Avionics Intra-Communications (WAIC) systems. The major hindrance in ensuring reliable communications in this regard comes from the operation of the existing Radio Altimeter systems in the allotted frequency band of 4.2 - 4.4 GHz. WAIC systems based on wireless techniques such as Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiplexing (OFDM) have been simulated in MATLAB for the analysis. The performance of the WAIC systems in the presence of interference from Altimeter signals and Additive White Gaussian Noise (AWGN) has been evaluated and studied

An Investigation of Ultra-Wideband Filters for Cognitive Radio Networks

The requirement for radio spectrum has been increasing and this has resulted in the materialization of wireless applications with enhanced features and higher data rate. The spectrum is scant, and the current radio spectrum regulation is making its use inefficient. This necessitates the development of new dynamic spectrum allocation policies to better exploit the existing spectrum. According to the present spectrum allocation regulations, specific frequency bands are allocated to particular services and only approved users are granted access to licensed bands. Cognitive radio (CR) is expected to modernize the mode spectrum is allocated. In a CR network, the intelligent radio part allows secondary users (unlicensed users) to access spectrum bands allocated to the licensed primary users with the avoidance of interference. A solution to this inefficiency has been highly successful in the ISM (2.4 GHz), the U-NII (5–6 GHz), and microwave (57–64 GHz) bands, by making the unused spectra accessible on an unlicensed basis. However, in order to obtain spectra for unlicensed operation, new sharing concepts have been introduced to allow the usage of spectra by secondary users under the prerequisite that they limit their interference to the primary users. This would start by studying techniques employed in the design of UWB filters. This study is aimed to investigate the filters for overlay and underlay CR. This paper presents a comparative study of ultra-wideband filters for Cognitive Radio Networks