2,748 research outputs found
Max-Min SNR Signal Energy based Spectrum Sensing Algorithms for Cognitive Radio Networks with Noise Variance Uncertainty
This paper proposes novel spectrum sensing algorithms for cognitive radio
networks. By assuming known transmitter pulse shaping filter, synchronous and
asynchronous receiver scenarios have been considered. For each of these
scenarios, the proposed algorithm is explained as follows: First, by
introducing a combiner vector, an over-sampled signal of total duration equal
to the symbol period is combined linearly. Second, for this combined signal,
the Signal-to-Noise ratio (SNR) maximization and minimization problems are
formulated as Rayleigh quotient optimization problems. Third, by using the
solutions of these problems, the ratio of the signal energy corresponding to
the maximum and minimum SNRs are proposed as a test statistics. For this test
statistics, analytical probability of false alarm () and detection ()
expressions are derived for additive white Gaussian noise (AWGN) channel. The
proposed algorithms are robust against noise variance uncertainty. The
generalization of the proposed algorithms for unknown transmitter pulse shaping
filter has also been discussed. Simulation results demonstrate that the
proposed algorithms achieve better than that of the Eigenvalue
decomposition and energy detection algorithms in AWGN and Rayleigh fading
channels with noise variance uncertainty. The proposed algorithms also
guarantee the desired in the presence of adjacent channel
interference signals
Eigenvalue-based Cyclostationary Spectrum Sensing Using Multiple Antennas
In this paper, we propose a signal-selective spectrum sensing method for
cognitive radio networks and specifically targeted for receivers with
multiple-antenna capability. This method is used for detecting the presence or
absence of primary users based on the eigenvalues of the cyclic covariance
matrix of received signals. In particular, the cyclic correlation significance
test is used to detect a specific signal-of-interest by exploiting knowledge of
its cyclic frequencies. The analytical threshold for achieving constant false
alarm rate using this detection method is presented, verified through
simulations, and shown to be independent of both the number of samples used and
the noise variance, effectively eliminating the dependence on accurate noise
estimation. The proposed method is also shown, through numerical simulations,
to outperform existing multiple-antenna cyclostationary-based spectrum sensing
algorithms under a quasi-static Rayleigh fading channel, in both spatially
correlated and uncorrelated noise environments. The algorithm also has
significantly lower computational complexity than these other approaches.Comment: 6 pages, 6 figures, accepted to IEEE GLOBECOM 201
Cooperative spectrum sensing: performance analysis and algorithms
The employment of cognitive (intelligent) radios presents an opportunity to efficiently
use the scarce spectrum with the condition that it causes a minimal disturbance
to the primary user. So the cognitive or secondary users use spectrum sensing
to detect the presence of primary user.
In this thesis, different aspects related to spectrum sensing and cognitive radio
performance are theoretically studied for the discussion and in most cases, closedform
expressions are derived. Simulations results are also provided to verify the
derivations.
Firstly, robust spectrum sensing techniques are proposed considering some realistic
conditions, such as carrier frequency offset (CFO) and phase noise (PN).
These techniques are called the block-coherent detector (N2
-BLCD), the secondorder
matched filter-I (SOMF-I) and the second-order matched filter-II (SOMF-II).
The effect of CFO on N2
-BLCD and SOMF-I is evaluated theoretically and by simulation
for SOMF-II. However, the effect of PN is only evaluated by simulation for
all proposed techniques.
Secondly, the detection performance of an energy detector (ED) is analytically
investigated over a Nakagami-m frequency-selective (NFS) channel.
Thirdly, the energy efficiency aspect of cooperative spectrum sensing is addressed,
whereby the energy expenditure is reduced when secondary users report their test
statistics to the fusion center (FC). To alleviate the energy consumption overhead,
a censored selection combining based power censoring (CSCPC) is proposed. The
accomplishment of energy saving is conducted by not sending the test statistic that
does not contain robust information or it requires a lot of transmit power. The detection
performance of the CSCPC is analytically derived using stochastic geometry
tools and verified by simulation. Simulation results show that that the CSCPC
technique can reduce the energy consumption compared with the conventional techniques
while a detection performance distortion remains negligible.
Finally, an analytical evaluation for the cognitive radio performance is presented
while taking into consideration realistic issues, such as noise uncertainty (NU) and
NFS channel. In the evaluation, sensing-throughput tradeoff is used as an examination
metric. The results illustrate the NU badly affects the performance, but the
performance may improve when the number of multipath increases
DVB-T signal detection for indoor environments in low-SNR regime
The problem of coexistence between the primary
(licensed) and secondary (non-licensed) users can be solved
in various ways. One of them assumes the application of the
detailed Radio Environment Maps being a kind of database,
where some crucial information about the licensed
transmission can be stored. In this paper we propose the
new methods for signal detection in low signal-to-noise
regime and compare it through hardware experiment with
other known techniques used for spectrum sensing.Peer ReviewedPostprint (author’s final draft
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