2,824 research outputs found
Edge Computing Aware NOMA for 5G Networks
With the fast development of Internet of things (IoT), the fifth generation
(5G) wireless networks need to provide massive connectivity of IoT devices and
meet the demand for low latency. To satisfy these requirements, Non-Orthogonal
Multiple Access (NOMA) has been recognized as a promising solution for 5G
networks to significantly improve the network capacity. In parallel with the
development of NOMA techniques, Mobile Edge Computing (MEC) is becoming one of
the key emerging technologies to reduce the latency and improve the Quality of
Service (QoS) for 5G networks. In order to capture the potential gains of NOMA
in the context of MEC, this paper proposes an edge computing aware NOMA
technique which can enjoy the benefits of uplink NOMA in reducing MEC users'
uplink energy consumption. To this end, we formulate a NOMA based optimization
framework which minimizes the energy consumption of MEC users via optimizing
the user clustering, computing and communication resource allocation, and
transmit powers. In particular, similar to frequency Resource Blocks (RBs), we
divide the computing capacity available at the cloudlet to computing RBs.
Accordingly, we explore the joint allocation of the frequency and computing RBs
to the users that are assigned to different order indices within the NOMA
clusters. We also design an efficient heuristic algorithm for user clustering
and RBs allocation, and formulate a convex optimization problem for the power
control to be solved independently per NOMA cluster. The performance of the
proposed NOMA scheme is evaluated via simulations
Resource Allocation for Downlink NOMA Systems: Key Techniques and Open Issues
This article presents advances in resource allocation (RA) for downlink
non-orthogonal multiple access (NOMA) systems, focusing on user pairing (UP)
and power allocation (PA) algorithms. The former pairs the users to obtain the
high capacity gain by exploiting the channel gain difference between the users,
while the later allocates power to users in each cluster to balance system
throughput and user fairness. Additionally, the article introduces the concept
of cluster fairness and proposes the divideand- next largest difference-based
UP algorithm to distribute the capacity gain among the NOMA clusters in a
controlled manner. Furthermore, performance comparison between multiple-input
multiple-output NOMA (MIMO-NOMA) and MIMO-OMA is conducted when users have
pre-defined quality of service. Simulation results are presented, which
validate the advantages of NOMA over OMA. Finally, the article provides avenues
for further research on RA for downlink NOMA.Comment: 5G, NOMA, Resource allocation, User pairing, Power allocatio
Resource Allocation Optimization for Users with Different Levels of Service in Multicarrier Systems
We optimize the throughput of a single cell multiuser orthogonal frequency
division multiplexing system with proportional data rate fairness among the
users. The concept is to support mobile users with different levels of service.
The optimization problem is a mixed integer nonlinear programming problem,
which is computationally very expensive. We propose a novel and efficient
near-optimal solution adopting a two-phase optimization approach that separates
the subcarrier and power allocation. In the first phase, we relax the strict
proportional data rate requirements and employ an iterative subcarrier
allocation approach that coarsely satisfies desired data rate proportionality
constraints. In the second phase, we reallocate the power among the users in an
iterative way to further enhance the adherence to the desired proportions by
exploiting the normalized proportionality deviation measure. The simulation
results show that the proposed solution exhibits very strong adherence to the
desired proportional data rate fairness while achieving higher system
throughput compared to the other existing solutions.Comment: Resource Allocation in MU-OFD
Uplink Non-Orthogonal Multiple Access for 5G Wireless Networks
Orthogonal Frequency Division Multiple Access (OFDMA) as well as other
orthogonal multiple access techniques fail to achieve the system capacity limit
in the uplink due to the exclusivity in resource allocation. This issue is more
prominent when fairness among the users is considered in the system. Current
Non-Orthogonal Multiple Access (NOMA) techniques introduce redundancy by
coding/spreading to facilitate the users' signals separation at the receiver,
which degrade the system spectral efficiency. Hence, in order to achieve higher
capacity, more efficient NOMA schemes need to be developed. In this paper, we
propose a NOMA scheme for uplink that removes the resource allocation
exclusivity and allows more than one user to share the same subcarrier without
any coding/spreading redundancy. Joint processing is implemented at the
receiver to detect the users' signals. However, to control the receiver
complexity, an upper limit on the number of users per subcarrier needs to be
imposed. In addition, a novel subcarrier and power allocation algorithm is
proposed for the new NOMA scheme that maximizes the users' sum-rate. The
link-level performance evaluation has shown that the proposed scheme achieves
bit error rate close to the single-user case. Numerical results show that the
proposed NOMA scheme can significantly improve the system performance in terms
of spectral efficiency and fairness comparing to OFDMA.Comment: Presented in the International Symposium on Wireless Communications
Systems (ISWCS), 201
Energy Efficiency with Proportional Rate Fairness in Multi-Relay OFDM Networks
This paper investigates the energy efficiency (EE) in multiple relay aided
OFDM system, where decode-and-forward (DF) relay beamforming is employed to
help the information transmission. In order to explore the EE performance with
user fairness for such a system, we formulate an optimization problem to
maximize the EE by jointly considering several factors, the transmission mode
selection (DF relay beamforming or direct-link transmission), the helping relay
set selection, the subcarrier assignment and the power allocation at the source
and relays on subcarriers, under nonlinear proportional rate fairness
constraints, where both transmit power consumption and linearly rate-dependent
circuit power consumption are taken into account. To solve the non-convex
optimization problem, we propose a low-complexity scheme to approximate it.
Simulation results demonstrate its effectiveness. We also investigate the
effects of the circuit power consumption on system performances and observe
that with both the constant and the linearly rate-dependent circuit power
consumption, system EE grows with the increment of system average channel-to
noise ratio (CNR), but the growth rates show different behaviors. For the
constant circuit power consumption, system EE increasing rate is an increasing
function of the system average CNR, while for the linearly rate-dependent one,
system EE increasing rate is a decreasing function of the system average CNR.
This observation is very important which indicates that by deducing the circuit
dynamic power consumption per unit data rate, system EE can be greatly
enhanced. Besides, we also discuss the effects of the number of users and
subcarriers on the system EE performance.Comment: 35 pages, 15 fihures, submitted to IEEE Journa
Adaptive Subcarrier and Bit Allocation for Downlink OFDMA System with Proportional Fairness
This paper investigates the adaptive subcarrier and bit allocation algorithm
for OFDMA systems. To minimize overall transmitted power, we propose a novel
adaptive subcarrier and bit allocation algorithm based on channel state
information (CSI) and quality state information (QSI). A suboptimal approach
that separately performs subcarrier allocation and bit loading is proposed. It
is shown that a near optimal solution is obtained by the proposed algorithm
which has low complexity compared to that of other conventional algorithm. We
will study the problem of finding an optimal sub-carrier and power allocation
strategy for downlink communication to multiple users in an OFDMA based
wireless system. Assuming knowledge of the instantaneous channel gains for all
users, we propose a multiuser OFDMA subcarrier, and bit allocation algorithm to
minimize the total transmit power. This is done by assigning each user a set of
subcarriers and by determining the number of bits and the transmit power level
for each subcarrier. The objective is to minimize the total transmitted power
over the entire network to satisfy the application layer and physical layer. We
formulate this problem as a constrained optimization problem and present
centralized algorithms. The simulation results will show that our approach
results in an efficient assignment of subcarriers and transmitter power levels
in terms of the energy required for transmitting each bit of information, to
address this need, we also present a bit loading algorithm for allocating
subcarriers and bits in order to satisfy the rate requirements of the links
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
Interference Management in NOMA-based Fog-Radio Access Networks via Joint Scheduling and Power Adaptation
Non-Orthogonal Multiple Access (NOMA) and Fog Radio Access Networks (FRAN)
are promising candidates within the 5G and beyond systems. This work examines
the benefit of adopting NOMA in an FRAN architecture with constrained capacity
fronthaul. The paper proposes methods for optimizing joint scheduling and power
adaptation in the downlink of a NOMA-based FRAN with multiple resource blocks
(RB). We consider a mixed-integer optimization problem which maximizes a
network-wide rate-based utility function subject to fronthaul-capacity
constraints, so as to determine i) the user-to-RB assignment, ii) the allocated
power to each RB, and iii) the power split levels of the NOMA users in each RB.
The paper proposes a feasible decoupled solution for such non-convex
optimization problem using a three-step hybrid centralized/distributed
approach. The proposed solution complies with FRAN operation that aims to
partially shift the network control to the FAPs, so as to overcome delays due
to fronthaul rate constraints. The paper proposes and compares two distinct
methods for solving the assignment problem, namely the Hungarian method, and
the Multiple Choice Knapsack method. The power allocation and the NOMA power
split optimization, on the other hand, are solved using the alternating
direction method of multipliers (ADMM). Simulations results illustrate the
advantages of the proposed methods compared to different baseline schemes
including the conventional Orthogonal Multiple Access (OMA), for different
utility functions and different network environments
Enhanced Uplink Resource Allocation in Non-Orthogonal Multiple Access Systems
Non-orthogonal multiple access (NOMA) is envisioned to be one of the most
beneficial technologies for next generation wireless networks due to its
enhanced performance compared to other conventional radio access techniques.
Although the principle of NOMA allows multiple users to use the same frequency
resource, due to decoding complication, information of users in practical
systems cannot be decoded successfully if many of them use the same channel.
Consequently, assigned spectrum of a system needs to be split into multiple
subchannels in order to multiplex that among many users. Uplink resource
allocation for such systems is more complicated compared to the downlink ones
due to the individual users' power constraints and discrete nature of
subchannel assignment. In this paper, we propose an uplink subchannel and power
allocation scheme for such systems. Due to the NP-hard and non-convex nature of
the problem, the complete solution, that optimizes both subchannel assignment
and power allocation jointly, is intractable. Consequently, we solve the
problem in two steps. First, based on the assumption that the maximal power
level of a user is subdivided equally among its allocated subchannels, we apply
many-to-many matching model to solve the subchannel-user mapping problem. Then,
in order to enhance the performance of the system further, we apply iterative
water-filling and geometric programming two power allocation techniques to
allocate power in each allocated subchannel-user slot optimally. Extensive
simulation has been conducted to verify the effectiveness of the proposed
scheme. The results demonstrate that the proposed scheme always outperforms all
existing works in this context under all possible scenarios.Comment: 13 page
Power Minimization Techniques in Distributed Base Station Antenna Systems using Non-Orthogonal Multiple Access
This paper introduces new approaches for combining non-orthogonal multiple
access (NOMA) with distributed base station (DBS) deployments. The purpose of
the study is to unlock the true potentials of DBS systems in the NOMA context,
since all previous works dealing with power minimization in NOMA are performed
in the CBS (centralized base station) context. This work targets a minimization
of the total transmit power in each cell, under user rate and power
multiplexing constraints. Different techniques are designed for the joint
allocation of subcarriers, antennas and power, with a particular care given to
insuring a moderate complexity. Results show an important gain in the total
transmit power obtained by the DBS-NOMA combination, with respect to both
DBS-OMA (orthogonal multiple access) and CBS-NOMA deployment scenarios.Comment: Submitted pape
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