599 research outputs found
Resource Allocation in Multi-carrier Full-duplex Networks
학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 2. 박세웅.Recent advances in the physical layer have demonstrated the feasibility of in-band wireless full-duplex for a node to simultaneously transmit and receive on the same frequency band.
While the full-duplex operation can ideally double throughput,
the network-level gain of full-duplex in large-scale networks remains unclear due to the complicated resource allocation in multi-carrier environments.
In this dissertation, we tackle three different resource allocation problems in multi-carrier full-duplex networks.
Firstly, we investigate the power allocation problem in three-node
full-duplex OFDM networks where one full-duplex node
transmits to a half-duplex node while receiving from another half-duplex node at the same time.
We formulate the sum-rate maximization problem with and without joint decoding, and develop a
low-complexity solution for each case.
Through simulations, we evaluate our proposed solutions and demonstrate the full-duplex gain in various scenarios.
Secondly, we consider the resource allocation problem in full-duplex OFDMA networks where both the base station and mobile nodes are full-duplex capable.
We propose a joint solution to the subcarrier assignment and power allocation problem by establishing a necessary condition for the sum-rate optimality.
We show that our algorithm is provably efficient in achieving \emph{local Pareto optimality} under certain conditions that are frequently met in practice.
Through extensive simulations, we show that our algorithm empirically achieves near-optimal performance.
Lastly, we investigate the resource allocation problem in full-duplex OFDMA networks where the base station is full-duplex capable while mobile nodes are conventional half-duplex nodes.
Specifically, we consider two different cases where i) the BS knows all channel gains and ii) the BS obtains limited channel information through channel feedback from each node.
In the former case, we design a sequential resource allocation algorithm which assigns subcarriers to uplink nodes first and downlink nodes or vice versa.
In the latter case, we propose a low-overhead channel feedback protocol where downlink nodes can estimate inter-node interference by overheating feedback messages transmitted by uplink nodes.
We evaluate our solutions under various scenarios through simulations.1 Introduction
1.1 Motivation
1.2 Background and Related Work
1.3 Contributions and Outline
2 Power Allocation with Inter-node Interference in Full-duplex OFDM Networks
2.1 Introduction
2.2 System Model and Problem Formulation
2.3 Power Allocation with Joint Decoding
2.3.1 Convex Problem and Dual Formulation
2.3.2 Optimal Power Allocation via Dual Optimization
2.4 Power Allocation without Joint Decoding
2.4.1 Necessary Conditions for Local Optimality
2.4.2 Optimality of FDMA Power Allocation
2.4.3 NP-hardness of Finding Optimal Power Allocation
2.4.4 Partial FDMA Power Allocation
2.5 Performance Evaluation
2.6 Summary
3 Resource Allocation in Full-duplex OFDMA Networks
3.1 Introduction
3.2 System Model
3.3 Necessary Condition for Optimality
3.4 Proposed Resource Allocation Algorithm
3.4.1 Power Allocation
3.4.2 Subcarrier Assignment
3.5 Local Pareto Optimality
3.6 Performance Bound
3.7 Performance Evaluation
3.7.1 Simulation Results
3.8 Summary
4 Resource Allocation with Inter-node Interference in Full-duplex OFDMA Networks
4.1 Introduction
4.2 System Model and Problem Formulation
4.3 Resource Allocation with Full CSI
4.3.1 Subcarrier Assignment Condition
4.3.2 Proposed Resource Allocation Algorithms
4.3.3 Asymtotic Analysis of Full-duplex Gain
4.4 Resource Allocation with Limited CSI
4.4.1 Challenge of Channel Feedback
4.4.2 Proposed Feedback Protocol
4.4.3 Calculation of Thresholds
4.4.4 Performance Analysis and Optimal Feedback Probability
4.5 Performance Evaluation
4.5.1 Simulation Setting
4.5.2 Simulation Results: Full CSI
4.5.3 Simulation Results: Limited CSI
4.6 Summary
5 Conclusion
5.1 Research Contributions
5.2 Future Research DirectionsDocto
Optimization Framework and Graph-Based Approach for Relay-Assisted Bidirectional OFDMA Cellular Networks
This paper considers a relay-assisted bidirectional cellular network where
the base station (BS) communicates with each mobile station (MS) using OFDMA
for both uplink and downlink. The goal is to improve the overall system
performance by exploring the full potential of the network in various
dimensions including user, subcarrier, relay, and bidirectional traffic. In
this work, we first introduce a novel three-time-slot time-division duplexing
(TDD) transmission protocol. This protocol unifies direct transmission, one-way
relaying and network-coded two-way relaying between the BS and each MS. Using
the proposed three-time-slot TDD protocol, we then propose an optimization
framework for resource allocation to achieve the following gains: cooperative
diversity (via relay selection), network coding gain (via bidirectional
transmission mode selection), and multiuser diversity (via subcarrier
assignment). We formulate the problem as a combinatorial optimization problem,
which is NP-complete. To make it more tractable, we adopt a graph-based
approach. We first establish the equivalence between the original problem and a
maximum weighted clique problem in graph theory. A metaheuristic algorithm
based on any colony optimization (ACO) is then employed to find the solution in
polynomial time. Simulation results demonstrate that the proposed protocol
together with the ACO algorithm significantly enhances the system total
throughput.Comment: 27 pages, 8 figures, 2 table
Resource allocation in OFDMA networks with half-duplex and imperfect full-duplex users
Recent studies indicate the feasibility of in-band fullduplex (FD) wireless
communications, where a wireless radio transmits and receives simultaneously in
the same band. Due to its potential to increase the capacity, analyzing the
performance of a cellular network that contains full-duplex devices is crucial.
In this paper, we consider maximizing the weighted sum-rate of downlink and
uplink of a single cell OFDMA network which consists of an imperfect FD
base-station (BS) and a mixture of half-duplex and imperfect full-duplex mobile
users. To this end, the joint problem of sub-channel assignment and power
allocation is investigated and a two-step solution is proposed. A heuristic
algorithm to allocate each sub-channel to a pair of downlink and uplink users
with polynomial complexity is presented. The power allocation problem is
convexified based on the difference of two concave functions approach, for
which an iterative solution is obtained. Simulation results demonstrate that
when all the users and the BS are perfect FD nodes the network throughput could
be doubled, Otherwise, the performance improvement is limited by the inter-node
interference and the self-interference. We also investigate the effect of the
self-interference cancellation capability and the percentage of FD users on the
network performance in both indoor and outdoor scenarios.Comment: 6 pages, 8 figures, Accepted in IEEE International Conference on
Communication (ICC), Malaysia, 201
Low Complexity WMMSE Power Allocation In NOMA-FD Systems
In this paper we study the problem of power and channel allocation with the
objective of maximizing the system sum-rate for multicarrier non-orthogonal
multiple access (NOMA) full duplex (FD) systems. Such an allocation problem is
non-convex and, thus, with the goal of designing a low complexity solution, we
propose a scheme based on the minimization of the weighted mean square error,
which achieves performance reasonably close to the optimum and allows to
clearly outperforms a conventional orthogonal multiple access approach.
Numerical results assess the effectiveness of our algorithm.Comment: 5 pages conference paper, 3 figures. Submitted on ICASSP 202
Enhancing Physical Layer Security in AF Relay Assisted Multi-Carrier Wireless Transmission
In this paper, we study the physical layer security (PLS) problem in the dual
hop orthogonal frequency division multiplexing (OFDM) based wireless
communication system. First, we consider a single user single relay system and
study a joint power optimization problem at the source and relay subject to
individual power constraint at the two nodes. The aim is to maximize the end to
end secrecy rate with optimal power allocation over different sub-carriers.
Later, we consider a more general multi-user multi-relay scenario. Under high
SNR approximation for end to end secrecy rate, an optimization problem is
formulated to jointly optimize power allocation at the BS, the relay selection,
sub-carrier assignment to users and the power loading at each of the relaying
node. The target is to maximize the overall security of the system subject to
independent power budget limits at each transmitting node and the OFDMA based
exclusive sub-carrier allocation constraints. A joint optimization solution is
obtained through duality theory. Dual decomposition allows to exploit convex
optimization techniques to find the power loading at the source and relay
nodes. Further, an optimization for power loading at relaying nodes along with
relay selection and sub carrier assignment for the fixed power allocation at
the BS is also studied. Lastly, a sub-optimal scheme that explores joint power
allocation at all transmitting nodes for the fixed subcarrier allocation and
relay assignment is investigated. Finally, simulation results are presented to
validate the performance of the proposed schemes.Comment: 10 pages, 7 figures, accepted in Transactions on Emerging
Telecommunications Technologies (ETT), formerly known as European
Transactions on Telecommunications (ETT
Performance Trade-off Between Uplink and Downlink in Full-Duplex Communications
In this paper, we formulate two multi-objective optimization problems (MOOPs)
in orthogonal frequency-division multiple access (OFDMA)-based in-band
full-duplex (IBFD) wireless communications.~The aim of this study is to exploit
the performance trade-off between uplink and downlink where a wireless radio
simultaneously transmits and receives in the same frequency.~We consider
maximizing the system throughput as the first MOOP and minimizing the system
aggregate power consumption as the second MOOP between uplink and
downlink,~while taking into account the impact of self-interference~(SI)~and
quality of service provisioning.~We study the throughput and the transmit power
trade-off between uplink and downlink via solving these two problems.~Each MOOP
is a non-convex mixed integer non-linear programming~(MINLP)~which is generally
intractable. In order to circumvent this difficulty, a penalty function is
introduced to reformulate the problem into a mathematically tractable
form.~Subsequently,~each MOOP is transformed into a single-objective
optimization problem~(SOOP)~via the weighted Tchebycheff method which is
addressed by majorization-minimization~(MM)~approach. Simulation results
demonstrate an interesting trade-off between the considered competing
objectives.Comment: This paper is accepted by IEEE International Conference on
Communications (ICC
Multi-Objective Optimization for Energy-and Spectral-Efficiency Tradeoff in In-band Full-Duplex (IBFD) Communication
The problem of joint power and sub-channel allocation to maximize energy
efficiency (EE) and spectral efficiency (SE) simultaneously in in-band
full-duplex (IBFD) orthogonal frequency-division multiple access (OFDMA)
network is addressed considering users' QoS in both uplink and downlink. The
resulting optimization problem is a non-convex mixed-integer non-linear program
(MINLP) which is generally difficult to solve. In order to strike a balance
between the EE and SE, we restate this problem as a multi-objective
optimization problem (MOOP) which aims at maximizing system's throughput and
minimizing system's power consumption, simultaneously. To this end, the
\epsilon constraint method is adopted to transform the MOOP into
single-objective optimization problem (SOOP). The underlying problem is solved
via an efficient solution based on the majorization minimization (MM) approach.
Furthermore, in order to handle binary subchannel allocation variable
constraints, a penalty function is introduced. Simulation results unveil
interesting tradeoffs between EE and SE.Comment: This paper is accepted by IEEE Global Communications Conference 201
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