Award Date

12-2011

Degree Type

Thesis

Degree Name

Doctor of Philosophy in Electrical Engineering

Department

Electrical and Computer Engineering

First Committee Member

Ebrahim Saberinia, Chair

Second Committee Member

Shahram Latifi

Third Committee Member

Peter Stubberud

Graduate Faculty Representative

Sidkazem Taghva

Number of Pages

78

Abstract

The main challenge in any cognitive radio system is to maximize secondary users throughput while limiting interference imposed on licensed users. In this regard, finding the optimal sensing and transmission timing strategies and accurate sensing techniques are of great importance in a cognitive radio network.

In this thesis, we study a sensing-transmission scheme for secondary user in a cognitive radio system where the secondary user senses every primary channel independently and transmits a signal for a fixed duration if it finds the channel empty and stays idle for another fixed duration if it senses the channel busy. We obtain optimal idle and transmission durations which maximize access opportunity of the secondary user while keeping the interference ratios on the primary channels below some thresholds. Our results show that unless we have an error free perfect channel sensing, adding the idle duration improves the performance of the system.

We also study a cooperative spectrum sensing scheme for cognitive radio systems where each sensor transmits multi-bit quantized information to a fusion center where the decision about the availability or occupancy of the channel is made. We compare iii the performance of our proposed multi-bit combining scheme with hard and soft combining schemes and show that with transmission of a few bits of information from each sensor , the system can achieve an error rate very close to the optimal soft combining scheme.

Keywords

Applied sciences; Cognitive radio networks; Radio — Transmitters and transmission; Radio frequency allocation; Spectrum sensing; Transmission timing

Disciplines

Controls and Control Theory | Electrical and Computer Engineering | Signal Processing

Language

English


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