7,944 research outputs found
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
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
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
Optimal time sharing in underlay cognitive radio systems with RF energy harvesting
Due to the fundamental tradeoffs, achieving spectrum efficiency and energy
efficiency are two contending design challenges for the future wireless
networks. However, applying radio-frequency (RF) energy harvesting (EH) in a
cognitive radio system could potentially circumvent this tradeoff, resulting in
a secondary system with limitless power supply and meaningful achievable
information rates. This paper proposes an online solution for the optimal time
allocation (time sharing) between the EH phase and the information transmission
(IT) phase in an underlay cognitive radio system, which harvests the RF energy
originating from the primary system. The proposed online solution maximizes the
average achievable rate of the cognitive radio system, subject to the
-percentile protection criteria for the primary system. The
optimal time sharing achieves significant gains compared to equal time
allocation between the EH and IT phases.Comment: Proceedings of the 2015 IEEE International Conference on
Communications (IEEE ICC 2015), 8-12 June 2015, London, U
Generic Multiuser Coordinated Beamforming for Underlay Spectrum Sharing
The beamforming techniques have been recently studied as possible enablers
for underlay spectrum sharing. The existing beamforming techniques have several
common limitations: they are usually system model specific, cannot operate with
arbitrary number of transmit/receive antennas, and cannot serve arbitrary
number of users. Moreover, the beamforming techniques for underlay spectrum
sharing do not consider the interference originating from the incumbent primary
system. This work extends the common underlay sharing model by incorporating
the interference originating from the incumbent system into generic combined
beamforming design that can be applied on interference, broadcast or multiple
access channels. The paper proposes two novel multiuser beamforming algorithms
for user fairness and sum rate maximization, utilizing newly derived convex
optimization problems for transmit and receive beamformers calculation in a
recursive optimization. Both beamforming algorithms provide efficient operation
for the interference, broadcast and multiple access channels, as well as for
arbitrary number of antennas and secondary users in the system. Furthermore,
the paper proposes a successive transmit/receive optimization approach that
reduces the computational complexity of the proposed recursive algorithms. The
results show that the proposed complexity reduction significantly improves the
convergence rates and can facilitate their operation in scenarios which require
agile beamformers computation.Comment: 30 pages, 5 figure
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