OFDM-based cognitive radio for DSA networks

摘要: With the advent of new high data rate wireless applications, as well growth existing services, demand for additional bandwidth is rapidly increasing. Existing “command-and-control” spectrum allocations defined by government regulatory agencies, such federal communications commission (FCC), prohibit unlicensed access to licensed spectrum, constraining them instead several heavily populated, interference-prone frequency bands. However, it has been shown that not utilized efficiently across time and frequency. Therefore, FCC currently working on concept users “borrowing” from incumbent license holders temporarily improve utilization. This called dynamic (DSA). Cognitive radios offer versatile, powerful, portable transceivers enabling DSA. dissertation investigates physical layer techniques enhance a cognitive radio performance. Multi-carrier techniques, orthogonal division multiplexing (OFDM), support huge rates are robust channel impairments. with growing access, may be difficult any single transmission obtain large contiguous block in DSA environment. proposes novel non-contiguous OFDM (NC-OFDM) technique, where implementation achieves via collective usage number subcarriers while simultaneously avoiding interference transmissions turning off corresponding these Moreover, performance proposed NC-OFDM technique compared other multi-carrier code multiple (MC-CDMA). One major drawbacks an signal exhibit peak-toaverage power ratio (PAPR) values resulting expensive transceivers. presents extensive overview taxonomy PAPR reduction algorithms literature. five reducing viz., subcarrier phase adjustment algorithm, adaptive-mode variable throughput low correlation sequences-based algorithm. Due noncontiguous nature environment, statistical properties different signal. Additionally, conventional need carefully chosen modified used lay out design requirements implements fast Fourier transform (FFT) modulating demodulating efficient general FFT pruning algorithm improving efficiency evaluation arithmetic operations, when deactivated. Given employing quickly adapt changing operating hardware resources small form factor limited, would beneficial.