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Full-Text Articles in Engineering
Frequency Agile Ofdm System For Radio Communication In High Frequency Bands, Erin E. Hill
Frequency Agile Ofdm System For Radio Communication In High Frequency Bands, Erin E. Hill
Electrical & Computer Engineering Theses & Dissertations
High Frequency (HF) radio communication existed as the primary source of over-the-horizon communication for decades prior to the wide implementation of satellite and cellular networks. Even today, should satellite communication become unavailable, the robust backup of HF vitally supports long distance data transmission without the need of a cellular infrastructure. This capability is of particular importance to naval applications while at sea. Frequency choice, however, becomes critical in supporting reliable HF communication as too high of a frequency will not return to earth and too low of a frequency will result in high absorption rates within the atmosphere. A potential …
Performance Of Cognitive Radio Networks With Unknown Dynamic Primary User Signals, Sara L. Macdonald
Performance Of Cognitive Radio Networks With Unknown Dynamic Primary User Signals, Sara L. Macdonald
Electrical & Computer Engineering Theses & Dissertations
The current static assignment of RF spectrum in the United States and other parts of the world has led to a large portion of the RF spectrum to be geographically and temporally underutilized. While the amount of RF spectrum is finite, the demand for spectrum continues to increase making it necessary to increase utilization of many bands. Several innovative methods for allowing licensed primary users (PUs) to share spectrum with unlicensed secondary users (SUs) have being proposed. Of these methods Cognitive Radio (CR) has emerged as a promising technology that enables SUs to dynamically access spectrum after first sensing the …
Recurrent Neural Networks And Matrix Methods For Cognitive Radio Spectrum Prediction And Security, Alexander M. Glandon
Recurrent Neural Networks And Matrix Methods For Cognitive Radio Spectrum Prediction And Security, Alexander M. Glandon
Electrical & Computer Engineering Theses & Dissertations
In this work, machine learning tools, including recurrent neural networks (RNNs), matrix completion, and non-negative matrix factorization (NMF), are used for cognitive radio problems. Specifically addressed are a missing data problem and a blind signal separation problem. A specialized RNN called Cellular Simultaneous Recurrent Network (CSRN), typically used in image processing applications, has been modified. The CRSN performs well for spatial spectrum prediction of radio signals with missing data. An algorithm called soft-impute for matrix completion used together with an RNN performs well for missing data problems in the radio spectrum time-frequency domain. Estimating missing spectrum data can improve cognitive …
Detection Of Ofdm Signals Using Pilot Tones And Applications To Spectrum Sensing For Cognitive Radio Systems, Ahmed Temtam
Detection Of Ofdm Signals Using Pilot Tones And Applications To Spectrum Sensing For Cognitive Radio Systems, Ahmed Temtam
Electrical & Computer Engineering Theses & Dissertations
Nowadays there are an increasing number of wireless devices which support wireless networking and the need for higher data rate communication is increasing rabidly. As more and more systems go wireless, approaching technologies will face spectral crowding and existence of wireless devices will be an important issue. Because of the limited bandwidth availability, accepting the request for higher capacity and data rates is a challenging task, demanding advanced technologies that can offers new methods of using the available radio spectrum. Cognitive radio introduces a key solution to the spectral increasing issue by presenting the opportunistic usage of spectrum that is …
Enhancing Spectrum Utilization In Dynamic Cognitive Radio Systems, Dusadee Treeumnuk
Enhancing Spectrum Utilization In Dynamic Cognitive Radio Systems, Dusadee Treeumnuk
Electrical & Computer Engineering Theses & Dissertations
Cognitive radio (CR) is regarded as a viable solution to enabling flexible use of the frequency spectrum in future generations of wireless systems by allowing unlicensed secondary users (SU) to access licensed spectrum under the specific condition that no harmful interference be caused to the licensed primary users (PU) of the spectrum. In practical scenarios, the knowledge of PU activity is unknown to CRs and radio environments are mostly imperfect due to various issues such as noise uncertainty and multipath fadings. Therefore, important functionalities of CR systems are to efficiently detect availability of radio spectrum as well as to avoid …
Spectrum Adaptation In Cognitive Radio Systems With Operating Constraints, Deepak R. Joshi
Spectrum Adaptation In Cognitive Radio Systems With Operating Constraints, Deepak R. Joshi
Electrical & Computer Engineering Theses & Dissertations
The explosion of high-data-rate-demanding wireless applications such as smart-phones and wireless Internet access devices, together with growth of existing wireless services, are creating a shortage of the scarce Radio Frequency (RF) spectrum. However, several spectrum measurement campaigns revealed that current spectrum usage across time and frequency is inefficient, creating the artificial shortage of the spectrum because of the traditional exclusive "command-and-control" model of using the spectrum. Therefore, a new concept of Cognitive Radio (CR) has been emerging recently in which unlicensed users temporarily borrow spectrum from the licensed Primary Users (PU) based on the Dynamic Spectrum Access (DSA) technique that …
Analysis And Optimization Of Dynamic Spectrum Sharing For Cognitive Radio Networks, Manish Wadhwa
Analysis And Optimization Of Dynamic Spectrum Sharing For Cognitive Radio Networks, Manish Wadhwa
Electrical & Computer Engineering Theses & Dissertations
The goal of this dissertation is to present the analysis and optimization of dynamic spectrum sharing for cognitive radio networks (CRNs). Spectrum scarcity is a well known problem at present. In order to deal with this problem, dynamic spectrum sharing (DSS) was proposed. DSS is a technique where cognitive radio networks dynamically and opportunistically share the channels with primary users. The major contribution of this dissertation is in analyzing the problem of dynamic spectrum sharing under different scenarios and developing optimal solutions for these scenarios. In the first scenario, a contention based dynamic spectrum sharing model is considered and its …