Recently, interest has been shown in cognitive radio (CR) systems since they can op-
portunistically access unused spectrum bands thereby increasing usable communication
capacity. Spectrum sensing has been identified as a key function to ensure that CR can
detect spectrum holes. In a CR network, a fast and accurate spectrum sensing scheme is
important.
Spectrum sensing can be viewed as a signal detection problem. Most of the existing
spectrum sensing schemes are based on fixed sample size detectors which means that their
sensing time is preset and fixed. However, the work of Wald [27] showed that a detector
based on sequential detection requires less average sensing time than a fixed sample size
detector.
In this thesis, we have applied the method of sequential detection to reduce the average
sensing time. Simulation results have shown that, compared to the fixed sample size
energy detector, a sequential detector can reduce sensing time by up to 85% in the AWGN
channel for the same detection performance. In order to limit sensing time, especially
in a fading environment, a truncated sequential detector is developed. The simulation
results show that the truncated sequential detector requires less sensing time than the
sequential detector, but the performance degrades due to truncation. Finally, a cooperative
spectrum sensing scheme is used where each individual sensor uses a sequential detector.
The combining rule used at the fusion center is a selection combining rule. Simulation
results show that the proposed cooperative spectrum sensing scheme can reduce the sensing
time compared to the individual spectrum sensing scheme.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/3682 |
| Date | January 2010 |
| Creators | Ma, Xiao |
| Publisher | University of Canterbury. Electrical and Computer Engineering |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Xiao Ma, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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