717 research outputs found
Optimal Resource Allocation for Power-Efficient MC-NOMA with Imperfect Channel State Information
In this paper, we study power-efficient resource allocation for multicarrier
non-orthogonal multiple access (MC-NOMA) systems. The resource allocation
algorithm design is formulated as a non-convex optimization problem which
jointly designs the power allocation, rate allocation, user scheduling, and
successive interference cancellation (SIC) decoding policy for minimizing the
total transmit power. The proposed framework takes into account the
imperfection of channel state information at transmitter (CSIT) and quality of
service (QoS) requirements of users. To facilitate the design of optimal SIC
decoding policy on each subcarrier, we define a channel-to-noise ratio outage
threshold. Subsequently, the considered non-convex optimization problem is
recast as a generalized linear multiplicative programming problem, for which a
globally optimal solution is obtained via employing the branch-and-bound
approach. The optimal resource allocation policy serves as a system performance
benchmark due to its high computational complexity. To strike a balance between
system performance and computational complexity, we propose a suboptimal
iterative resource allocation algorithm based on difference of convex
programming. Simulation results demonstrate that the suboptimal scheme achieves
a close-to-optimal performance. Also, both proposed schemes provide significant
transmit power savings than that of conventional orthogonal multiple access
(OMA) schemes.Comment: Accepted for publication, IEEE TCOM, May 17, 201
Energy Efficiency Optimization for NOMA UAV Network with Imperfect CSI
Unmanned aerial vehicles (UAVs) are developing rapidly owing to flexible
deployment and access services as air base stations. However, the channel
errors of low-altitude communication links formed by mobile deployment of UAVs
cannot be ignored. And the energy efficiency of the UAVs communication with
imperfect channel state information (CSI) hasnt been well studied yet.
Therefore, we focus on system performance optimization in non-orthogonal
multiple access (NOMA) UAV network considering imperfect CSI between the UAV
and users. A suboptimal resource allocation scheme including user scheduling
and power allocation is designed for maximizing energy efficiency. Because of
the nonconvexity of optimization function with an probability constraint for
imperfect CSI, the original problem is converted into a non-probability problem
and then decoupled into two convex subproblems. First, a user scheduling method
is applied in the two-side matching of users and subchannels by the difference
of convex programming. Then based on user scheduling, the energy efficiency in
UAV cells is optimized through a suboptimal power allocation algorithm by
successive convex approximation method. The simulation results prove that the
proposed algorithm is effective compared with existing resource allocation
schemes.Comment: to appear in IEEE Journal on Selected Areas in Communication
Power-Efficient Resource Allocation for MC-NOMA with Statistical Channel State Information
In this paper, we study the power-efficient resource allocation for
multicarrier non-orthogonal multiple access (MC-NOMA) systems. The resource
allocation algorithm design is formulated as a non-convex optimization problem
which takes into account the statistical channel state information at
transmitter and quality of service (QoS) constraints. To strike a balance
between system performance and computational complexity, we propose a
suboptimal power allocation and user scheduling with low computational
complexity to minimize the total power consumption. The proposed design
exploits the heterogeneity of QoS requirement to determine the successive
interference cancellation decoding order. Simulation results demonstrate that
the proposed scheme achieves a close-to-optimal performance and significantly
outperforms a conventional orthogonal multiple access (OMA) scheme.Comment: 7 Pages, 5 figures, accepted to IEEE GLOBECOM 201
Resource Allocation in Full-Duplex Mobile-Edge Computing Systems with NOMA and Energy Harvesting
This paper considers a full-duplex (FD) mobile-edge computing (MEC) system
with non-orthogonal multiple access (NOMA) and energy harvesting (EH), where
one group of users simultaneously offload task data to the base station (BS)
via NOMA and the BS simultaneously receive data and broadcast energy to other
group of users with FD. We aim at minimizing the total energy consumption of
the system via power control, time scheduling and computation capacity
allocation. To solve this nonconvex problem, we first transform it into an
equivalent problem with less variables. The equivalent problem is shown to be
convex in each vector with the other two vectors fixed, which allows us to
design an iterative algorithm with low complexity. Simulation results show that
the proposed algorithm achieves better performance than the conventional
methods
A Survey on Non-Orthogonal Multiple Access for 5G Networks: Research Challenges and Future Trends
Non-orthogonal multiple access (NOMA) is an essential enabling technology for
the fifth generation (5G) wireless networks to meet the heterogeneous demands
on low latency, high reliability, massive connectivity, improved fairness, and
high throughput. The key idea behind NOMA is to serve multiple users in the
same resource block, such as a time slot, subcarrier, or spreading code. The
NOMA principle is a general framework, and several recently proposed 5G
multiple access schemes can be viewed as special cases. This survey provides an
overview of the latest NOMA research and innovations as well as their
applications. Thereby, the papers published in this special issue are put into
the content of the existing literature. Future research challenges regarding
NOMA in 5G and beyond are also discussed.Comment: to appear in IEEE JSAC, 201
Energy-Efficient Resource Allocation in NOMA Heterogeneous Networks
Non-orthogonal multiple access (NOMA) has attracted much recent attention
owing to its capability for improving the system spectral efficiency in
wireless communications. Deploying NOMA in heterogeneous network can satisfy
users' explosive data traffic requirements, and NOMA will likely play an
important role in the fifth-generation (5G) mobile communication networks.
However, NOMA brings new technical challenges on resource allocation due to the
mutual cross-tier interference in heterogeneous networks. In this article, to
study the tradeoff between data rate performance and energy consumption in
NOMA, we examine the problem of energy-efficient user scheduling and power
optimization in 5G NOMA heterogeneous networks. The energy-efficient user
scheduling and power allocation schemes are introduced for the downlink 5G NOMA
heterogeneous network for perfect and imperfect channel state information (CSI)
respectively. Simulation results show that the resource allocation schemes can
significantly increase the energy efficiency of 5G NOMA heterogeneous network
for both cases of perfect CSI and imperfect CSI
Non-Orthogonal Multiple Access: Common Myths and Critical Questions
Non-orthogonal multiple access (NOMA) has received tremendous attention for
the design of radio access techniques for fifth generation (5G) wireless
networks and beyond. The basic concept behind NOMA is to serve more than one
user in the same resource block, e.g., a time slot, subcarrier, spreading code,
or space. With this, NOMA promotes massive connectivity, lowers latency,
improves user fairness and spectral efficiency, and increases reliability
compared to orthogonal multiple access (OMA) techniques. While NOMA has gained
significant attention from the communications community, it has also been
subject to several widespread misunderstandings, such as The above statements are actually false, and this paper aims at
identifying such common myths about NOMA and clarifying why they are not true.
We also pose critical questions that are important for the effective adoption
of NOMA in 5G and beyond and identify promising research directions for NOMA,
which will require intense investigation in the future.Comment: To appear in the IEEE Wireless Communication
Full-Duplex Non-Orthogonal Multiple Access for Modern Wireless Networks
Non-orthogonal multiple access (NOMA) is an interesting concept to provide
higher capacity for future wireless communications. In this article, we
consider the feasibility and benefits of combining full-duplex operation with
NOMA for modern communication systems. Specifically, we provide a comprehensive
overview on application of full-duplex NOMA in cellular networks, cooperative
and cognitive radio networks, and characterize gains possible due to
full-duplex operation. Accordingly, we discuss challenges, particularly the
self-interference and inter-user interference and provide potential solutions
to interference mitigation and quality-of-service provision based on
beamforming, power control, and link scheduling. We further discuss future
research challenges and interesting directions to pursue to bring full-duplex
NOMA into maturity and use in practice.Comment: Revised, IEEE Wireless Communication Magazin
Robust and Secure Resource Allocation for Full-Duplex MISO Multicarrier NOMA Systems
In this paper, we study the resource allocation algorithm design for
multiple-input single-output (MISO) multicarrier non-orthogonal multiple access
(MC-NOMA) systems, in which a full-duplex base station serves multiple
half-duplex uplink and downlink users on the same subcarrier simultaneously.
The resource allocation is optimized for maximization of the weighted system
throughput while the information leakage is constrained and artificial noise is
injected to guarantee secure communication in the presence of multiple
potential eavesdroppers. To this end, we formulate a robust non-convex
optimization problem taking into account the imperfect channel state
information (CSI) of the eavesdropping channels and the quality-of-service
(QoS) requirements of the legitimate users. Despite the non-convexity of the
optimization problem, we solve it optimally by applying monotonic optimization
which yields the optimal beamforming, artificial noise design, subcarrier
allocation, and power allocation policy. The optimal resource allocation policy
serves as a performance benchmark since the corresponding monotonic
optimization based algorithm entails a high computational complexity. Hence, we
also develop a low-complexity suboptimal resource allocation algorithm which
converges to a locally optimal solution. Our simulation results reveal that the
performance of the suboptimal algorithm closely approaches that of the optimal
algorithm. Besides, the proposed optimal MISO NOMA system can not only ensure
downlink and uplink communication security simultaneously but also provides a
significant system secrecy rate improvement compared to traditional MISO
orthogonal multiple access (OMA) systems and two other baseline schemes.Comment: Submitted for possible publicatio
Fundamental Green Tradeoffs: Progresses, Challenges, and Impacts on 5G Networks
With years of tremendous traffic and energy consumption growth, green radio
has been valued not only for theoretical research interests but also for the
operational expenditure reduction and the sustainable development of wireless
communications. Fundamental green tradeoffs, served as an important framework
for analysis, include four basic relationships: spectrum efficiency (SE) versus
energy efficiency (EE), deployment efficiency (DE) versus energy efficiency
(EE), delay (DL) versus power (PW), and bandwidth (BW) versus power (PW). In
this paper, we first provide a comprehensive overview on the extensive on-going
research efforts and categorize them based on the fundamental green tradeoffs.
We will then focus on research progresses of 4G and 5G communications, such as
orthogonal frequency division multiplexing (OFDM) and non-orthogonal
aggregation (NOA), multiple input multiple output (MIMO), and heterogeneous
networks (HetNets). We will also discuss potential challenges and impacts of
fundamental green tradeoffs, to shed some light on the energy efficient
research and design for future wireless networks.Comment: revised from IEEE Communications Surveys & Tutorial
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