3,366 research outputs found
Collaborative Spectrum Sensing from Sparse Observations in Cognitive Radio Networks
Spectrum sensing, which aims at detecting spectrum holes, is the precondition
for the implementation of cognitive radio (CR). Collaborative spectrum sensing
among the cognitive radio nodes is expected to improve the ability of checking
complete spectrum usage. Due to hardware limitations, each cognitive radio node
can only sense a relatively narrow band of radio spectrum. Consequently, the
available channel sensing information is far from being sufficient for
precisely recognizing the wide range of unoccupied channels. Aiming at breaking
this bottleneck, we propose to apply matrix completion and joint sparsity
recovery to reduce sensing and transmitting requirements and improve sensing
results. Specifically, equipped with a frequency selective filter, each
cognitive radio node senses linear combinations of multiple channel information
and reports them to the fusion center, where occupied channels are then decoded
from the reports by using novel matrix completion and joint sparsity recovery
algorithms. As a result, the number of reports sent from the CRs to the fusion
center is significantly reduced. We propose two decoding approaches, one based
on matrix completion and the other based on joint sparsity recovery, both of
which allow exact recovery from incomplete reports. The numerical results
validate the effectiveness and robustness of our approaches. In particular, in
small-scale networks, the matrix completion approach achieves exact channel
detection with a number of samples no more than 50% of the number of channels
in the network, while joint sparsity recovery achieves similar performance in
large-scale networks.Comment: 12 pages, 11 figure
Compressed Sensing based Dynamic PSD Map Construction in Cognitive Radio Networks
In the context of spectrum sensing in cognitive radio networks, collaborative spectrum sensing has been proposed as a way to overcome multipath and shadowing, and hence increasing the reliability of the sensing. Due to the high amount of information to be transmitted, a dynamic compressive sensing approach is proposed to map the PSD estimate to a sparse domain which is then transmitted to the fusion center. In this regard, CRs send a compressed version of their estimated PSD to the fusion center, whose job is to reconstruct the PSD estimates of the CRs, fuse them, and make a global decision on the availability of the spectrum in space and frequency domains at a given time. The proposed compressive sensing based method considers the dynamic nature of the PSD map, and uses this dynamicity in order to decrease the amount of data needed to be transmitted between CR sensors’ and the fusion center. By using the proposed method, an acceptable PSD map for cognitive radio purposes can be achieved by only 20 % of full data transmission between sensors and master node. Also, simulation results show the robustness of the proposed method against the channel variations, diverse compression ratios and processing times in comparison with static methods
Performance Analysis of Arbitrarily-Shaped Underlay Cognitive Networks: Effects of Secondary User Activity Protocols
This paper analyzes the performance of the primary and secondary users (SUs)
in an arbitrarily-shaped underlay cognitive network. In order to meet the
interference threshold requirement for a primary receiver (PU-Rx) at an
arbitrary location, we consider different SU activity protocols which limit the
number of active SUs. We propose a framework, based on the moment generating
function (MGF) of the interference due to a random SU, to analytically compute
the outage probability in the primary network, as well as the average number of
active SUs in the secondary network. We also propose a cooperation-based SU
activity protocol in the underlay cognitive network which includes the existing
threshold-based protocol as a special case. We study the average number of
active SUs for the different SU activity protocols, subject to a given outage
probability constraint at the PU and we employ it as an analytical approach to
compare the effect of different SU activity protocols on the performance of the
primary and secondary networks.Comment: submitted to possible IEEE Transactions publicatio
On the Estimation of Channel State Transitions for Cognitive Radio Systems
Coexistence by means of shared access is a cognitive radio application. The
secondary user models the slotted primary users channel access as a Markov
process. The model parameters, i.e, the state transition probabilities
(alpha,beta) help secondary user to determine the channel occupancy, thereby
enables secondary user to rank the primary user channels. These parameters are
unknown and need to be estimated by secondary users for each channel. To do so,
the secondary users have to sense all the primary user channels in every time
slot, which is unrealistic for a large and sparsely allocated primary user
spectrum. With no other choice left, the secondary user has to sense a channel
at random time intervals and estimate the parametric information for all the
channels using the observed slots.Comment: 6 page
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