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Cognitive radio networks have recently been proposed as a promising approach to overcome the serious problem of spectrum scarcity. Other emerging concept for innovative spectrum utilization is femtocells. Femtocells are low-power and short-range wireless access points installed by the end-user in residential or enterprise environments. A common feature of cognitive radio and femtocells is their two-tier nature involving primary and secondary users (PUs, SUs). While this new paradigm enables innovative alternatives to conventional spectrum management and utilization, it also brings its own technical challenges. A main challenge in cognitive radio is the design of efficient resource (spectrum) trading methods. Game and microeconomics theories provide tools for studying the strategic interactions through rationality and economic benefits between PUs and SUs for effective resource allocation. In this thesis, we investigate some efficient game theoretic and microeconomic approaches to address spectrum trading in cognitive networks. We propose two auction frameworks for shared and exclusive use models. In the first auction mechanism, we consider the shared used model in cognitive radio networks and design a spectrum trading method to maximize the total satisfaction of the SUs and revenue of the Wireless Service Provider (WSP). In the second auction mechanism, we investigate spectrum trading via auction approach for exclusive usage spectrum access model in cognitive radio networks. We consider a realistic valuation function and propose an efficient concurrent Vickrey-Clarke-Grove (VCG) mechanism for non-identical channel allocation among r-minded bidders in two different cases. The realization of cognitive radio networks in practice requires the development of effective spectrum sensing methods. A fundamental question is how much time to allocate for sensing purposes. In the literature on cognitive radio, it is commonly assumed that fixed time durations are assigned for spectrum sensing and data transmission. It is however possible to improve the network performance by finding the best tradeoff between sensing time and throughput. In this thesis, we derive an expression for the total average throughput of the SUs over time-varying fading channels. Then we maximize the total average throughput in terms of sensing time and the number of SUs assigned to cooperatively sense each channel. For practical implementation, we propose a dynamical programming algorithm for joint optimization of sensing time and the number of cooperating SUs for sensing purpose. Simulation results demonstrate that significant improvement in the throughput of SUs is achieved in the case of joint optimization. In the last part of the thesis, we further address the challenge of pricing in oligopoly market for open access femtocell networks. We propose dynamic pricing schemes based on microeconomic and game theoretic approaches such as market equilibrium, Bertrand game, multiple-leader-multiple-follower Stackelberg game. Based on our approaches, the per unit price of spectrum can be determined dynamically and mobile service providers can gain more revenue than fixed pricing scheme. Our proposed methods also provide residential customers more incentives and satisfaction to participate in open access model.

Cognitive radio has recently been proposed as a promising approach for efficient utilization of radio spectrum. However, there are several challenges to be addressed across all layers of a cognitive radio system design, from application to hardware implementation. From the physical layer point-of-view, two key challenges are spectrum sensing and an appropriate signaling scheme for data transmission. The modulation techniques used in cognitive radio not only should be efficient and flexible but also must not cause (harmful) interference to the primary (licensed) users. Among all the proposed signaling schemes for cognitive radio, orthogonal frequency division multiplexing (OFDM) has emerged as a promising one due to its robustness against multipath fading, high spectral efficiency, and capacity for dynamic spectrum use. However, OFDM suffers from high out-of-band radiation which is due to high sidelobes of subcarriers. In this thesis, we consider spectral shaping in OFDM-based cognitive radio systems with focus on reducing interference to primary users created by by out-of-band radiation of secondary users' OFDM signal. In the first part of this research, we first study the trade-o between time-based and frequency-based methods proposed for sidelobe suppression in OFDM. To this end, two recently proposed techniques, active interference cancellation (AIC) and adaptive symbol transition (AST), are considered and a new joint time-frequency scheme is developed for both single-antenna and multi-antenna systems. Furthermore, knowledge of wireless channel is used in the setting of the proposed joint scheme to better minimize interference to the primary user. This scheme enables us to evaluate the trade-o between the degrees of freedom provided by each of the two aforementioned methods. In the second part of this research, a novel low-complexity technique for reducing out-of-band radiation power of OFDM subcarriers for both single-antenna and multi-antenna systems is proposed. In the new technique, referred to as a phase adjustment technique, each OFDM symbol is rotated in the complex plane by an optimal phase such that the interference to primary users is minimized. It is shown that the phase adjustment technique neither reduces the system throughput, nor does increase the bit-error-rate of the system. Moreover, the performance of the technique in interference reduction is evaluated analytically in some special cases and is verified using numerical simulations. Due to high sensitivity of OFDM systems to time and frequency synchronization errors, performance of spectral shaping techniques in OFDM is significantly affected by timing jitter in practical systems. In the last part of this research, we investigate the impact of timing jitter on sidelobe suppression techniques. Considering AIC as the base method of sidelobe suppression, we first propose a mathematical model for OFDM spectrum in presence of timing jitter and evaluate the performance degradation to AIC due to timing jitter. Then, a precautionary scheme based on a minimax approach is proposed to make the technique robust against random timing jitter.

A model of the electromechanical characteristics, electrostatic characteristics and coil eddy current losses of a reed relay was developed. These characteristics were returned from reed and coil dimensions. The model was intended as an aid to the design of reed relays for Radio Frequency (RF) and high voltage applications. An electromechanical model of a reed switch and coil was developed using a combination of an axisymmetric finite element model and analytical methods. The characteristics returned from this model were operate, release and differential amp turns, contact gap and contact force. Inclusion of results for contact resistance against contact force yielded the contact resistance characteristics. Electrostatic force between reed contacts was calculated and a criteria for contact arcing in a vacuum applied to allow prediction of breakdown voltage in an evacuated reed switch. The above elements were incorporated in a "Reed Switch Design Program" in which operating, contact resistance and breakdown voltage characteristics were calculated from reed and coil dimensions. Results were found to be in agreement with measured values for three reed switch types. Eddy current losses in relay coils were investigated through experimental measurement of losses occurring in coils mounted around a copper conductor carrying a high frequency current. The losses occurring in the coil were found to present an effective resistance to the current in the conductor. The influence of coil dimensions and the magnetic properties of the conductor on losses were observed. An analytical model of eddy current losses was derived from first principals results and were found concordant with those measured. An "RF Reed Relay Design Program" embodying the eddy current loss model and preceding work was created to demonstrate how relay performance (and efficiency) can be enhanced by tuning reed and coil dimensions. An example of its successful application to product development at Crydom Magnetics Ltd is presented. Proposals for future work are included.

Orthogonal Frequency Division Multiplex (OFDM) is a flexible, robust multi-carrier modulation scheme. The orthogonal spectral shaping and spacing of OFDM sub-carriers ensure that their spectra can be over-lapped without leading to undesirable inter-carrier interference. Conventional OFDM systems have non-band limited Sinc(x) shaped subcarrier spectra. An alternative form of OFDM, referred to hereafter as Spectrally Shaped OFDM, employs band limited Nyquist shaped sub-carrier spectra. The research described in this thesis investigates the strengths and weaknesses of Spectrally Shaped OFDM as a potential modulation scheme for future mobile radio applications. From this research a novel Digital Signal Processing architecture for modulating and demodulating Spectrally Shaped OFDM sub-carriers has been derived which exploits the combination of a complex Discrete Fourier Transform (DFT) and PolyPhase Network (PPN) filter. This architecture is shown to significantly reduce the minimum number of computations required per symbol compared to previous designs. Using a custom coded computer simulation, the effects of varying the key parameters of the novel architecture's PolyPhase Filter (PPN) filter an the overall system complexity, spectral performance and system signal-to-distortion have been extensively studied. From these studies it is shown that compared to similar conventional OFDM systems, Spectrally Shaped OFDM systems possess superior out-of-band spectral qualities but significantly worse Peak-to-Average-Power-Ratio (PAPR) envelope performance. lt is also shown that the absolute value of the end PPN filter coefficients (dependent on the roll-off factor of the sub-carrier spectral shaping) dictate the system signal-to-distortion ratio when no time-domain windowing of the PPN filter coefficients is applied. Finally the effects of a both time and frequency selective fast fading channels on the modulation scheme's uncoded Bit Error Rate (BER) versus Signal-to-Noise (SNR) performance are simulated. The results obtained indicate that Spectrally Shaped OFDM is more robust (lower BER) to frequency-selective fading than time-selective fading.

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The intrinsic power and subtle influence of broadcasting is not readily recognized by the average consumer of mass media. This circumstance has an abusive potential for those wishing to use the electronic media for ulterior motives. Such was the case between 1933 and 1945 when the Nazis unleashed their manipulative mass media campaign that helped facilitate totalitarian control over the German people. This dissertation is the study of its radio component. Special emphasis is placed on the origins, construction, and subsequent implementation of Nazi broadcast rhetoric heard on domestic and short wave radio during the twelve-year period of the Third Reich. <br>In refusing the notion that a solitary critical perspective can be used in the creation of political consciousness and culture, I admit to using any theoretical insight or concept that sheds light on rhetorical efforts. In the practice of criticism, I believe this is the function of rhetorical theory. Therefore, the following selected theoretical methods are employed: <br>Crable’s theory of rhetoric as organization is shown as an appropriate means of describing the radio divisions within the bureaucratic Propaganda Ministry. <br>Bitzer’s work on the significance of the rhetorical situation is applied to the simple act of listening to finely crafted radio programming in Nazi Germany. <br>The speaker’s link between rhetoric and ideology is explained with McGee’s “ideograph” theory. <br>The construction of a new language suited to the goals of the Nazis is analyzed by examples of Burke’s unifiers and McGuire’s close textual work on Mein Kampf. <br>Marcuse divides the language into pragmatic and mythical layers, while the rhetoric and motivations of eight American “radio traitors,” who served as Nazi broadcasters, are investigated and tied into the overall propaganda scheme. The consequences of this inquiry indicate that the National Socialists, with Dr. Goebbels’ masterful propagandistic insights, tapped into the needs of a post-World War I German society and rebuilt a nationalistic spirit that unfortunately led to war and greater devastation than had been seen some three decades earlier. The new medium of radio, as a major source of information or mis-information, played no small part in this tragic outcome. / McAnulty College and Graduate School of Liberal Arts / Communication and Rhetorical Studies / PhD / Dissertation