521 research outputs found
Improved Spectrum Mobility using Virtual Reservation in Collaborative Cognitive Radio Networks
Cognitive radio technology would enable a set of secondary users (SU) to
opportunistically use the spectrum licensed to a primary user (PU). On the
appearance of this PU on a specific frequency band, any SU occupying this band
should free it for PUs. Typically, SUs may collaborate to reduce the impact of
cognitive users on the primary network and to improve the performance of the
SUs. In this paper, we propose and analyze the performance of virtual
reservation in collaborative cognitive networks. Virtual reservation is a novel
link maintenance strategy that aims to maximize the throughput of the cognitive
network through full spectrum utilization. Our performance evaluation shows
significant improvements not only in the SUs blocking and forced termination
probabilities but also in the throughput of cognitive users.Comment: 7 pages, 10 figures, IEEE ISCC 201
RF-Powered Cognitive Radio Networks: Technical Challenges and Limitations
The increasing demand for spectral and energy efficient communication
networks has spurred a great interest in energy harvesting (EH) cognitive radio
networks (CRNs). Such a revolutionary technology represents a paradigm shift in
the development of wireless networks, as it can simultaneously enable the
efficient use of the available spectrum and the exploitation of radio frequency
(RF) energy in order to reduce the reliance on traditional energy sources. This
is mainly triggered by the recent advancements in microelectronics that puts
forward RF energy harvesting as a plausible technique in the near future. On
the other hand, it is suggested that the operation of a network relying on
harvested energy needs to be redesigned to allow the network to reliably
function in the long term. To this end, the aim of this survey paper is to
provide a comprehensive overview of the recent development and the challenges
regarding the operation of CRNs powered by RF energy. In addition, the
potential open issues that might be considered for the future research are also
discussed in this paper.Comment: 8 pages, 2 figures, 1 table, Accepted in IEEE Communications Magazin
To Stay Or To Switch: Multiuser Dynamic Channel Access
In this paper we study opportunistic spectrum access (OSA) policies in a
multiuser multichannel random access cognitive radio network, where users
perform channel probing and switching in order to obtain better channel
condition or higher instantaneous transmission quality. However, unlikely many
prior works in this area, including those on channel probing and switching
policies for a single user to exploit spectral diversity, and on probing and
access policies for multiple users over a single channel to exploit temporal
and multiuser diversity, in this study we consider the collective switching of
multiple users over multiple channels. In addition, we consider finite
arrivals, i.e., users are not assumed to always have data to send and demand
for channel follow a certain arrival process. Under such a scenario, the users'
ability to opportunistically exploit temporal diversity (the temporal variation
in channel quality over a single channel) and spectral diversity (quality
variation across multiple channels at a given time) is greatly affected by the
level of congestion in the system. We investigate the optimal decision process
in this case, and evaluate the extent to which congestion affects potential
gains from opportunistic dynamic channel switching
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