12,038 research outputs found
Energy-Efficient Cooperative Cognitive Relaying Schemes for Cognitive Radio Networks
We investigate a cognitive radio network in which a primary user (PU) may
cooperate with a cognitive radio user (i.e., a secondary user (SU)) for
transmissions of its data packets. The PU is assumed to be a buffered node
operating in a time-slotted fashion where the time is partitioned into
equal-length slots. We develop two schemes which involve cooperation between
primary and secondary users. To satisfy certain quality of service (QoS)
requirements, users share time slot duration and channel frequency bandwidth.
Moreover, the SU may leverage the primary feedback message to further increase
both its data rate and satisfy the PU QoS requirements. The proposed
cooperative schemes are designed such that the SU data rate is maximized under
the constraint that the PU average queueing delay is maintained less than the
average queueing delay in case of non-cooperative PU. In addition, the proposed
schemes guarantee the stability of the PU queue and maintain the average energy
emitted by the SU below a certain value. The proposed schemes also provide more
robust and potentially continuous service for SUs compared to the conventional
practice in cognitive networks where SUs transmit in the spectrum holes and
silence sessions of the PUs. We include primary source burstiness, sensing
errors, and feedback decoding errors to the analysis of our proposed
cooperative schemes. The optimization problems are solved offline and require a
simple 2-dimensional grid-based search over the optimization variables.
Numerical results show the beneficial gains of the cooperative schemes in terms
of SU data rate and PU throughput, average PU queueing delay, and average PU
energy savings
Interference-Assisted Wireless Energy Harvesting in Cognitive Relay Network with Multiple Primary Transceivers
We consider a spectrum sharing scenario, where a secondary network coexists
with a primary network of multiple transceivers. The secondary network consists
of an energy-constrained decode-and-forward secondary relay which assists the
communication between a secondary transmitter and a destination in the presence
of the interference from multiple primary transmitters. The secondary relay
harvests energy from the received radio-frequency signals, which include the
information signal from the secondary transmitter and the primary interference.
The harvested energy is then used to decode the secondary information and
forward it to the secondary destination. At the relay, we adopt a time
switching policy due to its simplicity that switches between the energy
harvesting and information decoding over time. Specifically, we derive a
closed-form expression for the secondary outage probability under the primary
outage constraint and the peak power constraint at both secondary transmitter
and relay. In addition, we investigate the effect of the number of primary
transceivers on the optimal energy harvesting duration that minimizes the
secondary outage probability. By utilizing the primary interference as a useful
energy source in the energy harvesting phase, the secondary network achieves a
better outage performance.Comment: 6 pages, 5 figures, To be presented at IEEE GLOBECOM 201
Big Data analytics and Cognitive Computing: future opportunities for Astronomical research
The days of the lone astronomer with his optical telescope and photographic
plates are long gone: Astronomy in 2025 will not only be multi-wavelength, but
multi-messenger, and dominated by huge data sets and matching data rates.
Catalogues listing detailed properties of billions of objects will in
themselves require a new industrial-scale approach to scientific discovery,
requiring the latest techniques of advanced data analytics and an early
engagement with the first generation of cognitive computing systems.
Astronomers have the opportunity to be early adopters of these new technologies
and methodologies: the impact can be profound and highly beneficial to
effecting rapid progress in the field. Areas such as SETI research might
favourably benefit from cognitive intelligence that does not rely on human bias
and preconceptions.Comment: 4 pages, 1 figure. Paper presented at 2nd Radio and Antenna Days of
the Indian Ocean (RADIO 2014
Throughput Maximization for UAV-Aided Backscatter Communication Networks
This paper investigates unmanned aerial vehicle (UAV)-aided backscatter communication (BackCom) networks, where the UAV is leveraged to help the backscatter device (BD) forward signals to the receiver. Based on the presence or absence of a direct link between BD and receiver, two protocols, namely transmit-backscatter (TB) protocol and transmit-backscatter-relay (TBR) protocol, are proposed to utilize the UAV to assist the BD. In particular, we formulate the system throughput maximization problems for the two protocols by jointly optimizing the time allocation, reflection coefficient and UAV trajectory. Different static/dynamic circuit power consumption models for the two protocols are analyzed. The resulting optimization problems are shown to be non-convex, which are challenging to solve. We first consider the dynamic circuit power consumption model, and decompose the original problems into three sub-problems, namely time allocation optimization with fixed UAV trajectory and reflection coefficient, reflection coefficient optimization with fixed UAV trajectory and time allocation, and UAV trajectory optimization with fixed reflection coefficient and time allocation. Then, an efficient iterative algorithm is proposed for both protocols by leveraging the block coordinate descent method and successive convex approximation (SCA) techniques. In addition, for the static circuit power consumption model, we obtain the optimal time allocation with a given reflection coefficient and UAV trajectory and the optimal reflection coefficient with low computational complexity by using the Lagrangian dual method. Simulation results show that the proposed protocols are able to achieve significant throughput gains over the compared benchmarks
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