Browsing by Author "Hasan, S. M. Shajedul"

Now showing 1 - 3 of 3
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    IEEE 802.15.4 Implementation on an Embedded Device
    Thandee, Rithirong (Virginia Tech, 2012-04-10)
    Software Defined Radio (SDR) is a growing technology that allows radio communication to become interoperable. SDR can lower the cost for a particular hardware radio to communicate with another radio that uses a different standard. In order to show the capability of SDR, this thesis shows how to implement IEEE 802.14.5, a low-rate wireless personal area network (LR-WPAN) standard, on a standalone embedded machine. The implementation is done using a universal software radio peripheral embedded, USRP E100, an open source software development toolkit for SDR, GNU Radio, and UCLA ZigBee PHY GNU Radio application. The implementation can be done on the regular non-embedded USRPs. However, without a fast host computer demodulating the packets, the USRP E100 cannot receive incoming packets. An available FPGA is used to solve this problem by doing a software-hardware hybrid design to allow the USRP E100 to communicate with other IEEE 802.15.4 devices. The final product is an IEEE 802.15.4 monitor software that detects messages from devices communicating using IEEE 802.15.4 in its range. In addition, recommendations are presented for improving SDR education and training, particularly for developers with backgrounds in disciplines other than communications engineering.
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    New Concepts in Front End Design for Receivers with Large, Multiband Tuning Ranges
    Hasan, S. M. Shajedul (Virginia Tech, 2009-04-03)
    This dissertation presents new concepts in front end design for receivers with large, multiband tuning ranges. Such receivers are required to support large bandwidths (up to 10's of MHz) over very large tuning ranges (30:1 and beyond) with antennas that are usually narrowband, or which at best support multiple narrow bandwidths. Traditional techniques to integrate a single antenna with such receivers are limited in their ability to handle simultaneous channels distributed over very large tuning ranges, which is important for frequency-agile cognitive radio, surveillance, and other applications requiring wideband or multiband monitoring. Direct conversion architecture is gaining popularity due to the recent advancements in CMOS--based RFIC technology. The possibility of multiple parallel transceivers in RF CMOS suggests an approach to antenna--receiver integration using multiplexers. This dissertation describes an improved use of multiplexers to integrate antennas to receivers. First, the notion of sensitivity--constrained design is considered. In this approach, the goal is first to achieve sensitivity which is nominally dominated by external (environmental) noise, and then secondly to improve bandwidth to the maximum possible consistent with this goal. Next, a procedure is developed for designing antenna-multiplexer-preamplifier assemblies using this philosophy. It is shown that the approach can significantly increase the usable bandwidth and number of bands that can be supported by a single, traditional antenna. This performance is verified through field experiments. A prototype multiband multimode radio for public safety applications using these concepts is designed and demonstrated.
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    Spectrum Sensing and Blind Automatic Modulation Classification in Real-Time
    Steiner, Michael Paul (Virginia Tech, 2011-04-28)
    This paper describes the implementation of a scanning signal detector and automatic modulation classification system. The classification technique is a completely blind method, with no prior knowledge of the signal's center frequency, bandwidth, or symbol rate. An energy detector forms the initial approximations of the signal parameters. The energy detector used in the wideband sweep is reused to obtain fine estimates of the center frequency and bandwidth of the signal. The subsequent steps reduce the effect of frequency offset and sample timing error, resulting in a constellation of the modulation of interest. The cumulant of the constellation is compared to a set of known ideal cumulant values, forming the classification estimate. The algorithm uses two platforms that together provide high speed parallel processing and flexible run-time operation. High-rate spectral scanning using an energy detector is run in parallel with a variable down sampling path; both are highly pipelined structures, which allows for high data throughput. A pair of processing cores is used to record spectral usage and signal characteristics as well as perform the actual classification. The resulting classification system can accurately identify modulations below 5 dB of signal-to-noise ratio (SNR) for some cases of the phase shift keying family of modulations but requires a much higher SNR to accurately classify higher-order modulations. These estimates tend toward classifying all signals as binary phase shift keying because of limits of the noise power estimation part of the cumulant normalization process. Other effects due to frequency offset and synchronization timing are discussed.