57,196 research outputs found
Energy Efficiency in MIMO Underlay and Overlay Device-to-Device Communications and Cognitive Radio Systems
This paper addresses the problem of resource allocation for systems in which
a primary and a secondary link share the available spectrum by an underlay or
overlay approach. After observing that such a scenario models both cognitive
radio and D2D communications, we formulate the problem as the maximization of
the secondary energy efficiency subject to a minimum rate requirement for the
primary user. This leads to challenging non-convex, fractional problems. In the
underlay scenario, we obtain the global solution by means of a suitable
reformulation. In the overlay scenario, two algorithms are proposed. The first
one yields a resource allocation fulfilling the first-order optimality
conditions of the resource allocation problem, by solving a sequence of easier
fractional problems. The second one enjoys a weaker optimality claim, but an
even lower computational complexity. Numerical results demonstrate the merits
of the proposed algorithms both in terms of energy-efficient performance and
complexity, also showing that the two proposed algorithms for the overlay
scenario perform very similarly, despite the different complexity.Comment: to appear in IEEE Transactions on Signal Processin
Cooperative Cognitive Relaying Under Primary and Secondary Quality of Service Satisfaction
This paper proposes a new cooperative protocol which involves cooperation
between primary and secondary users. We consider a cognitive setting with one
primary user and multiple secondary users. The time resource is partitioned
into discrete time slots. Each time slot, a secondary user is scheduled for
transmission according to time division multiple access, and the remainder of
the secondary users, which we refer to as secondary relays, attempt to decode
the primary packet. Afterwards, the secondary relays employ cooperative
beamforming to forward the primary packet and to provide protection to the
secondary destination of the secondary source scheduled for transmission from
interference. We characterize the diversity-multiplexing tradeoff of the
primary source under the proposed protocol. We consider certain quality of
service for each user specified by its required throughput. The optimization
problem is stated under such condition. It is shown that the optimization
problem is linear and can be readily solved. We show that the sum of the
secondary required throughputs must be less than or equal to the probability of
correct packets reception.Comment: This paper was accepted in PIMRC 201
Outage Analysis for SWIPT-Enabled Two-Way Cognitive Cooperative Communications
In this paper, we study a cooperative cognitive radio network (CCRN) where
the secondary user-transmitter (SU-Tx) assists bi-directional communication
between a pair of primary users (PUs) following the principle of two-way
relaying. In return, it gets access to the spectrum of the PUs to enable its
own transmission to SU-receiver (SU-Rx). Further, in order to support
sustainable operation of the network, SU-Tx is assumed to harvest energy from
the RF signals received from the PUs, using the technique of simultaneous
wireless information and power transfer (SWIPT). Assuming a decode-and-forward
behaviour and power-splitting based relaying protocol at SU-Tx, closed form
expressions for outage probability of PU and SU are obtained. Simulation
results validate our analytical results and illustrate spectrum-efficiency and
energy-efficiency advantages of the proposed system over one-way relaying.Comment: 15 pages, 5 figures, Submitted to IEEE Transactions on Vehicular
Technolog
Resource Allocation in Wireless Networks with RF Energy Harvesting and Transfer
Radio frequency (RF) energy harvesting and transfer techniques have recently
become alternative methods to power the next generation of wireless networks.
As this emerging technology enables proactive replenishment of wireless
devices, it is advantageous in supporting applications with quality-of-service
(QoS) requirement. This article focuses on the resource allocation issues in
wireless networks with RF energy harvesting capability, referred to as RF
energy harvesting networks (RF-EHNs). First, we present an overview of the
RF-EHNs, followed by a review of a variety of issues regarding resource
allocation. Then, we present a case study of designing in the receiver
operation policy, which is of paramount importance in the RF-EHNs. We focus on
QoS support and service differentiation, which have not been addressed by
previous literatures. Furthermore, we outline some open research directions.Comment: To appear in IEEE Networ
Outage Analysis for SWIPT-Enabled Two-Way Cognitive Cooperative Communications
In this paper, we study a cooperative cognitive radio network (CCRN) where
the secondary user-transmitter (SU-Tx) assists bi-directional communication
between a pair of primary users (PUs) following the principle of two-way
relaying. In return, it gets access to the spectrum of the PUs to enable its
own transmission to SU-receiver (SU-Rx). Further, in order to support
sustainable operation of the network, SU-Tx is assumed to harvest energy from
the RF signals received from the PUs, using the technique of simultaneous
wireless information and power transfer (SWIPT). Assuming a decode-and-forward
behaviour and power-splitting based relaying protocol at SU-Tx, closed form
expressions for outage probability of PU and SU are obtained. Simulation
results validate our analytical results and illustrate spectrum-efficiency and
energy-efficiency advantages of the proposed system over one-way relaying.Comment: 15 pages, 5 figures, Submitted to IEEE Transactions on Vehicular
Technolog
Improving performance of far users in cognitive radio: Exploiting NOMA and wireless power transfer
In this paper, we examine non-orthogonal multiple access (NOMA) and relay selection strategy to benefit extra advantage from traditional cognitive radio (CR) relaying systems. The most important requirement to prolong lifetime of such network is employing energy harvesting in the relay to address network with limited power constraint. In particular, we study such energy harvesting CR-NOMA using amplify-and-forward (AF) scheme to improve performance far NOMA users. To further address such problem, two schemes are investigated in term of number of selected relays. To further examine system performance, the outage performance needs to be studied for such wireless powered CR-NOMA network over Rayleigh channels. The accurate expressions for the outage probability are derived to perform outage comparison of primary network and secondary network. The analytical results show clearly that position of these nodes, transmit signal to noise ratio (SNR) and power allocation coefficients result in varying outage performance. As main observation, performance gap between primary and secondary destination is decided by both power allocation factors and selection mode of single relay or multiple relays. Numerical studies were conducted to verify our derivations.Web of Science1211art. no. 220
Survey of Spectrum Sharing for Inter-Technology Coexistence
Increasing capacity demands in emerging wireless technologies are expected to
be met by network densification and spectrum bands open to multiple
technologies. These will, in turn, increase the level of interference and also
result in more complex inter-technology interactions, which will need to be
managed through spectrum sharing mechanisms. Consequently, novel spectrum
sharing mechanisms should be designed to allow spectrum access for multiple
technologies, while efficiently utilizing the spectrum resources overall.
Importantly, it is not trivial to design such efficient mechanisms, not only
due to technical aspects, but also due to regulatory and business model
constraints. In this survey we address spectrum sharing mechanisms for wireless
inter-technology coexistence by means of a technology circle that incorporates
in a unified, system-level view the technical and non-technical aspects. We
thus systematically explore the spectrum sharing design space consisting of
parameters at different layers. Using this framework, we present a literature
review on inter-technology coexistence with a focus on wireless technologies
with equal spectrum access rights, i.e. (i) primary/primary, (ii)
secondary/secondary, and (iii) technologies operating in a spectrum commons.
Moreover, we reflect on our literature review to identify possible spectrum
sharing design solutions and performance evaluation approaches useful for
future coexistence cases. Finally, we discuss spectrum sharing design
challenges and suggest future research directions
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
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