الفهرس 
1 IntroductionOnly 14 pages are availabe for public view
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Abstract
With the advent of new high data rate wireless applications, as well as growthof existing wireless services, demand for additional bandwidth is rapidly increasing. Multi-carrier techniques, such as Orthogonal Frequency Division Multiplexing (OFDM), support huge data rates that are robust to channel impairments. However, with a growing demand for spectrum access, it may be difficult for any single transmission to obtain a large contiguous frequency spectrum block in a Dynamic Spectrum Allocation (DSA) environment. This led to another form of OFDM, which is non-contiguous OFDM (NC-OFDM), where the implementation achieves high data rates via collective usage of a large number of non-contiguous subcarriers while simultaneously avoiding any interference to the existing transmissions by turning off the subcarriers corresponding to these spectrum bands. One of the major drawbacks of an OFDM signal is that it may exhibit large Peak-to-Average Power Ratio (PAPR) values resulting in expensive transceivers. This thesis introduces a proposed adaptive technique for reducing the number of side information bits required in the subcarrier phase adjustment technique for PAPR reduction of an OFDM signal. Moreover, the inefficient use of radio spectrum is becoming a serious problem as more and more wireless systems are being developed to operate in crowded spectrum bands. Cognitive radio offers a novel solution to overcome the underutilization problem by allowing secondary usage of the spectrum resources along with highly reliable communication. Spectrum sensing is a key enabler for cognitive radio. It identifies the idle spectrum and provides awareness regarding the radio environment, which is essential for the efficient secondary use of the spectrum and coexistence of different wireless systems. This thesis also introduces a proposed adaptive spectrum sensing technique that changes the sensing time according to SNR value
IIIof the received signal for improving the utilization and throughput of the secondary network.