International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Shaped Offset QPSK (SOQPSK), as proposed and analyzed by Terrance Hill, is a family of constant envelope waveforms that is non-proprietary and exhibits excellent spectral containment and detection efficiency. Results using a conventional coherent OQPSK demodulator without any special pulse shaping to recover the SOQPSK signal have been previously presented. This paper describes a trellis detector for SOQPSK-A and SOQPSK-B that provides superior detection performance, as compared to a traditional OQPSK detector, by accounting for the pulse shaping. Analytical error performance bounds, implementation of the trellis demodulator, and computer simulation results are presented.

Radio Frequency (RF) Power Amplifiers are responsible for a considerable amount of the power consumption in the entire transmitter-receiver (transceiver) of modern communication systems. The stringent linearity requirements of multi-standard transceivers to minimize cross-talking effects makes Linear Power Amplifiers, particularly class A, the preferred choice in broadband transceivers. This linearity requirement coupled with the fact that the Power Amplifier operates at low transmit power during most of its operation makes the efficiency of the entire transceiver poor. The limited transceiver efficiency leads to a reduction in the battery life of battery operated portable devices like mobile phones; hence drastically limiting talk time. To alleviate this issue, several research groups propose solutions to improve PA power efficiency. However, these solutions usually have a low efficiency at low power and are mostly limited to narrow bandwidth applications. In this thesis, the efficiency of a class A Power amplifier in wideband wireless standards like WiMax is improved by dynamically controlling the bias current and supply voltage of the PA. An efficient supply modulator based on a switching regulator architecture is proposed for controlling the supply voltage. The switching regulator is found to be slew-limited by the bulky inductor and capacitor used to regulate the supply voltage. The proposed solution alleviates the slew rate limitation by adding a bang-bang controlled current source. The proposed supply modulator has an average power efficiency of 81.6 percent and is suitable for wireless standards with bandwidths up to 20MHz compared to the relatively lower efficiencies and bandwidths of state of the art modulators. A class-A PA is shown to promise an average power efficiency of 21.3 percent when the bias current is controlled dynamically and the supply voltage is varied using the proposed supply modulator. This is a significant improvement over the poor average efficiency of 1.06 percent for a fixed bias conventional linear class A PA. The project has been simulated using the TSMC 0.18 micrometer technology.

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Base station (BS) positioning is considered an effective method to improve the performance of a Wireless Sensor Network (WSN). The goal of this dissertation is to minimize total energy consumption and to prolong lifetime of a WSN. First, the idea of the BS positioning in WSNs through our exhaustive search algorithm is evaluated; where it is shown that the BS position has an undeniable effect on the energy efficiency and lifespan of a WSN. Then, a metric-aware optimal BS positioning and relocation mechanism for WSNs is proposed. This technique locates the BS with respect to the available energy resources and the amount of traffic travelling through the sensor nodes at the time. Moreover, a BS relocation technique is presented in response to the dynamic environment that the sensor nodes operate in. Specifically, two optimization strategies based on the value of the path loss exponent are analyzed as weighted linear or nonlinear least squares minimization problems. Lastly, a distributed algorithm is proposed that can effectively handle the required computation by exploiting the nodes cooperation. The simulation results demonstrate that the proposed BS positioning and relocation method can significantly improve the lifespan and energy efficiency in WSNs. / Communications

Wireless distributed computing networks (WDCNs) will become the next frontier of the wireless industry as the performance of wireless platforms is being increased every year and wireless industries are looking for "killer" applications for increased channel capacity. However, WDCNs have several unique problems compared with currently well-investigated methods for wireless sensor networks and wired distributed computing. For example, it is difficult for WDCNs to be power/energy efficient considering the uncertainty and heterogeneity of the wireless environment. In addition, the service model has to take account of the interference-limited feature of wireless channels to reduce the service delay. Our research proposes a two-phase model for WDCNs including the service provision phase and the service access phase according to different traffic patterns and performance requirements. For the service provision phase, we investigate the impact of communication channel conditions on the average execution time of the computing tasks within WDCNs. We then discuses how to increase the robustness and power efficiency for WDCNs subject to the impact of channel variance and spatial heterogeneity. A resource allocation solution for computation oriented WDCNs is then introduced in detail which mitigates the effects of channel variations with a stochastic programming solution. Stochastic geometry and queue theory are combined to analyze the average performance of service response time and to design optimal access strategies during the service access phase. This access model provides a framework to analyze the service access performance and evaluate whether the channel heterogeneity should be considered. Based on this analysis, optimal strategies to access the service nodes can be determined in order to reduce the service response time. In addition, network initialization and synchronization are investigated in order to build a multiple channel WDCN in dynamic spectrum access (DSA) environments. Further, an efficient primary user detection method is proposed to reduce the channel vacation latency for WDCNs in DSA environments. Finally, this dissertation presents the complete design and implementation of a WDCN on COgnitive Radio Network (CORNET). Based on SDR technologies, software dedicated to WDCNs is designed and implemented across the PHY layer, MAC layer, and application layer. System experiments are carried out to demonstrate the performance issues and solutions presented in this dissertation. Wireless distributed computing networks (WDCNs) will become the next frontier of the wireless industry as the performance of wireless platforms is being increased every year and wireless industries are looking for "killer" applications for increased channel capacity. However, WDCNs have several unique problems compared with currently well-investigated methods for wireless sensor networks and wired distributed computing. For example, it is difficult for WDCNs to be power/energy efficient considering the uncertainty and heterogeneity of the wireless environment. In addition, the service model has to take account of the interference-limited feature of wireless channels to reduce the service delay. Our research proposes a two-phase model for WDCNs including the service provision phase and the service access phase according to different traffic patterns and performance requirements. For the service provision phase, we investigate the impact of communication channel conditions on the average execution time of the computing tasks within WDCNs. We then discuses how to increase the robustness and power efficiency for WDCNs subject to the impact of channel variance and spatial heterogeneity. A resource allocation solution for computation oriented WDCNs is then introduced in detail which mitigates the effects of channel variations with a stochastic programming solution. Stochastic geometry and queue theory are combined to analyze the average performance of service response time and to design optimal access strategies during the service access phase. This access model provides a framework to analyze the service access performance and evaluate whether the channel heterogeneity should be considered. Based on this analysis, optimal strategies to access the service nodes can be determined in order to reduce the service response time. In addition, network initialization and synchronization are investigated in order to build a multiple channel WDCN in dynamic spectrum access (DSA) environments. Further, an efficient primary user detection method is proposed to reduce the channel vacation latency for WDCNs in DSA environments. Finally, this dissertation presents the complete design and implementation of a WDCN on COgnitive Radio Network (CORNET). Based on SDR technologies, software dedicated to WDCNs is designed and implemented across the PHY layer, MAC layer, and application layer. System experiments are carried out to demonstrate the performance issues and solutions presented in this dissertation. / Ph. D.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Shaped Offset Quadrature Shift Keying (SOQPSK) is a spectrally efficient modulation that has been promoted in the airborne telemetry community as a more spectrally efficient alternative for legacy PCM/FM. First generation demodulators for SOQPSK use coherent detectors which achieve good bit error rates at the expense of long synchronization times. This paper examines the performance of a noncoherent SOQPSK detector which significantly improves the signal acquisition times without impacting BER performance in the AWGN environment. The two detection methods are also compared in their ability to combat other channel impairments, such as adjacent and on-channel interference.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A simple, low cost radio frequency (RF) power and spectrally efficient integrated transceiver/modem architecture employing Feher’s patented Quadrature Phase Shift Keying (FQPSK) is described. The FQPSK signals presented in this paper are obtained by using additional post low-pass filters in the FQPSK architecture. This implementation significantly improves the spectral efficiency of the worldwide commercially standardized Gaussian Minimum Shift Keying (GMSK) systems. The Bit Error Rate (BER) performance of FQPSK in additive white Gaussian noise (AWGN) channel has been investigated by means of computer simulation and hardware prototype measurements. The results of the hardware and software simulations are compared to GMSK and QPSK/OQPSK performance. These results show that the filtered FQPSK modulated signal passing through a non-linear amplifier (NLA) can achieve a spectral efficiency improvement of about 60% over NLA filtered OQPSK and an integrated spectral efficiency improvement of 50% over GMSK and a better BER performance. In particular, 100 kb/s to 34 Mb/s hardware experimental results over 2.4 GHz NLA (saturated) 1 Watt system confirmed that FQPSK hardware systems attain a BER=f(Eb/N0) performance within 1 dB to 2 dB of predicted theoretical results.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Space agencies are under pressure to utilize better bandwidth-efficient communication methods due to the actual allocated frequency bands becoming more congested. Budget reductions is another problem that the space agencies must deal with. This budget constraint results in simpler spacecraft carrying less communication capabilities and also the reduction in staff to capture data in the earth stations. It is then imperative that the most bandwidth efficient communication methods be utilized. This paper gives the results of a computer simulation study on 8 Level Phase Shift Keying (8PSK) modulation with respect to bandwidth, power efficiency, spurious emissions, interference susceptibility and the non-constant envelope effect through a non-linear channel. The simulations were performed on a Signal Processing Worksystem (SPW: software installed on a SUN SPARC 10 Unix Station and Hewlett Packard Model 715/100 Unix Station). This work was conducted at New Mexico State University (NMSU) in the Center for Space Telemetry and Telecommunications Systems in the Klipsch School of Electrical and Computer Engineering.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Shaped Offset QPSK (SOQPSK), as proposed and analyzed by Terrance Hill, is a family of constant envelope waveforms that is non-proprietary and exhibits excellent spectral containment and detection efficiency. Results for two variants, defined as SOQPSK-A and -B, have previously been presented. However, it remains to be seen whether or not even more attractive choices exist. This paper explores the bandwidth and power efficiency trade-offs of the entire SOQPSK family using computer simulations and analytical performance bounds.

The Smartphone revolution and the Internet of Things (IoTs) have triggered rapid advances in complex system-on-chips (SoCs) that increasing provide more functionality within a tight power budget. Highly power efficient on die switched-capacitor voltage regulators suffer from large output voltage ripple preventing their widespread use in modern integrated circuits. With technology scaling and increasing architectural complexity, the number of transistors switching in a power domain is growing rapidly leading to major issues with respect to voltage noise. The large voltage and frequency guard-bands present in current microprocessor designs to combat voltage noise both degrade the performance and erode the energy efficiency of the design. In an effort to reduce guard-bands, adaptive clocking based systems combat the problem of voltage noise by adjusting the clock frequency during a voltage droop to avoid timing failure. This thesis presents an integrated power management and clocking scheme that utilizes clock-data compensation to achieve adaptive clocking. The design is capable of automatically con figuring the supply voltage given a target clock frequency for the load circuit. Furthermore, during a voltage droop the design adjusts clock frequency to meet critical path timing margins while simultaneously increasing the current delivered to the load to recover from the droop. The design was implemented in IBM's 130nm technology and simulation results show that the design is able to clock the load circuit from 30 MHz to 800 Mhz with current efficiencies as high as 97%.