952 research outputs found
Sub-channel Assignment, Power Allocation and User Scheduling for Non-Orthogonal Multiple Access Networks
In this paper, we study the resource allocation and user scheduling problem
for a downlink nonorthogonal multiple access network where the base station
allocates spectrum and power resources to a set of users. We aim to jointly
optimize the sub-channel assignment and power allocation to maximize the
weighted total sum-rate while taking into account user fairness. We formulate
the sub-channel allocation problem as equivalent to a many-to-many two-sided
user-subchannel matching game in which the set of users and sub-channels are
considered as two sets of players pursuing their own interests. We then propose
a matching algorithm which converges to a two-side exchange stable matching
after a limited number of iterations. A joint solution is thus provided to
solve the sub-channel assignment and power allocation problems iteratively.
Simulation results show that the proposed algorithm greatly outperforms the
orthogonal multiple access scheme and a previous non-orthogonal multiple access
scheme.Comment: Accepted as a regular paper by IEEE Transactions on Wireless
Communication
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
A Genetic Algorithm-Based Approach to Power Allocation in Rate-Splitting Multiple Access Systems
We consider the problem of power allocation in Rate-Splitting Multiple Access
(RSMA) systems, where messages are split into common and private messages. The
common and private streams are jointly transmitted to allow efficient use of
the bandwidth, and decoded by Successive Interference Cancellation (SIC) at the
receiver. However, the power allocation between streams significantly affects
the overall performance. In this letter, we address this problem. We develop a
novel algorithm, dubbed Power Allocation in RSMA systems using Genetic
Algorithm (PARGA), to allocate the power between streams in RSMA systems in
order to maximize the user sum-rate. Simulation results demonstrate the high
efficiency of PARGA compared to existing methods.Comment: 5 pages, 5 figure
Recent advances in radio resource management for heterogeneous LTE/LTE-A networks
As heterogeneous networks (HetNets) emerge as one of the most promising developments toward realizing the target specifications of Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, radio resource management (RRM) research for such networks has, in recent times, been intensively pursued. Clearly, recent research mainly concentrates on the aspect of interference mitigation. Other RRM aspects, such as radio resource utilization, fairness, complexity, and QoS, have not been given much attention. In this paper, we aim to provide an overview of the key challenges arising from HetNets and highlight their importance. Subsequently, we present a comprehensive survey of the RRM schemes that have been studied in recent years for LTE/LTE-A HetNets, with a particular focus on those for femtocells and relay nodes. Furthermore, we classify these RRM schemes according to their underlying approaches. In addition, these RRM schemes are qualitatively analyzed and compared to each other. We also identify a number of potential research directions for future RRM development. Finally, we discuss the lack of current RRM research and the importance of multi-objective RRM studies
Medium access control protocol design for wireless communications and networks review
Medium access control (MAC) protocol design plays a crucial role to increase the performance of wireless communications and networks. The channel access mechanism is provided by MAC layer to share the medium by multiple stations. Different types of wireless networks have different design requirements such as throughput, delay, power consumption, fairness, reliability, and network density, therefore, MAC protocol for these networks must satisfy their requirements. In this work, we proposed two multiplexing methods for modern wireless networks: Massive multiple-input-multiple-output (MIMO) and power domain non-orthogonal multiple access (PD-NOMA). The first research method namely Massive MIMO uses a massive number of antenna elements to improve both spectral efficiency and energy efficiency. On the other hand, the second research method (PD-NOMA) allows multiple non-orthogonal signals to share the same orthogonal resources by allocating different power level for each station. PD-NOMA has a better spectral efficiency over the orthogonal multiple access methods. A review of previous works regarding the MAC design for different wireless networks is classified based on different categories. The main contribution of this research work is to show the importance of the MAC design with added optimal functionalities to improve the spectral and energy efficiencies of the wireless networks
Performance Analysis and Resource Allocation of STAR-RIS Aided Wireless-Powered NOMA System
This paper proposes a simultaneous transmitting and reflecting reconfigurable
intelligent surface (STAR-RIS) aided wireless-powered non-orthogonal multiple
access (NOMA) system, which includes an access point (AP), a STAR-RIS, and two
non-orthogonal users located at both sides of the STAR-RIS. In this system, the
users first harvest the radio-frequency energy from the AP in the downlink,
then adopt the harvested energy to transmit information to the AP in the uplink
concurrently. Two policies are considered for the proposed system. The first
one assumes that the time-switching protocol is used in the downlink while the
energy-splitting protocol is adopted in the uplink, named TEP. The second one
assumes that the energy-splitting protocol is utilized in both the downlink and
uplink, named EEP. The outage probability, sum throughput, and average age of
information (AoI) of the proposed system with TEP and EEP are investigated over
Nakagami-m fading channels. In addition, we also analyze the outage
probability, sum throughput, and average AoI of the STAR-RIS aided
wireless-powered time-division-multiple-access (TDMA) system. Simulation and
numerical results show that the proposed system with TEP and EEP outperforms
baseline schemes, and significantly improves sum throughput performance but
reduces outage probability and average AoI performance compared to the STAR-RIS
aided wireless-powered TDMA system. Furthermore, to maximize the sum throughput
and ensure a certain average AoI, we design a genetic-algorithm based time
allocation and power allocation (GA-TAPA) algorithm. Simulation results
demonstrate that the proposed GA-TAPA method can significantly improve the sum
throughput by adaptively adjusting system parameters.Comment: 30 pages, 12 figure
On the Throughput of Large-but-Finite MIMO Networks using Schedulers
This paper studies the sum throughput of the {multi-user}
multiple-input-single-output (MISO) networks in the cases with large but finite
number of transmit antennas and users. Considering continuous and bursty
communication scenarios with different users' data request probabilities, we
derive quasi-closed-form expressions for the maximum achievable throughput of
the networks using optimal schedulers. The results are obtained in various
cases with different levels of interference cancellation. Also, we develop an
efficient scheduling scheme using genetic algorithms (GAs), and evaluate the
effect of different parameters, such as channel/precoding models, number of
antennas/users, scheduling costs and power amplifiers' efficiency, on the
system performance. Finally, we use the recent results on the achievable rates
of finite block-length codes to analyze the system performance in the cases
with short packets. As demonstrated, the proposed GA-based scheduler reaches
(almost) the same throughput as in the exhaustive search-based optimal
scheduler, with substantially less implementation complexity. Moreover, the
power amplifiers' inefficiency and the scheduling delay affect the performance
of the scheduling-based systems significantly
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