3,621 research outputs found
Resource Allocation for Device-to-Device Communications Underlaying Heterogeneous Cellular Networks Using Coalitional Games
Heterogeneous cellular networks (HCNs) with millimeter wave (mmWave)
communications included are emerging as a promising candidate for the fifth
generation mobile network. With highly directional antenna arrays, mmWave links
are able to provide several-Gbps transmission rate. However, mmWave links are
easily blocked without line of sight. On the other hand, D2D communications
have been proposed to support many content based applications, and need to
share resources with users in HCNs to improve spectral reuse and enhance system
capacity. Consequently, an efficient resource allocation scheme for D2D pairs
among both mmWave and the cellular carrier band is needed. In this paper, we
first formulate the problem of the resource allocation among mmWave and the
cellular band for multiple D2D pairs from the view point of game theory. Then,
with the characteristics of cellular and mmWave communications considered, we
propose a coalition formation game to maximize the system sum rate in
statistical average sense. We also theoretically prove that our proposed game
converges to a Nash-stable equilibrium and further reaches the near-optimal
solution with fast convergence rate. Through extensive simulations under
various system parameters, we demonstrate the superior performance of our
scheme in terms of the system sum rate compared with several other practical
schemes.Comment: 13 pages, 12 figure
Joint Optimization of Resource Allocation and User Association in Multi-Frequency Cellular Networks Assisted by RIS
Due to the development of communication technology and the rise of user
network demand, a reasonable resource allocation for wireless networks is the
key to guaranteeing regular operation and improving system performance. Various
frequency bands exist in the natural network environment, and heterogeneous
cellular network (HCN) has become a hot topic for current research. Meanwhile,
Reconfigurable Intelligent Surface (RIS) has become a key technology for
developing next-generation wireless networks. By modifying the phase of the
incident signal arriving at the RIS surface, RIS can improve the signal quality
at the receiver and reduce co-channel interference. In this paper, we develop a
RIS-assisted HCN model for a multi-base station (BS) multi-frequency network,
which includes 4G, 5G, millimeter wave (mmwave), and terahertz networks, and
considers the case of multiple network coverage users, which is more in line
with the realistic network characteristics and the concept of 6G networks. We
propose the optimization objective of maximizing the system sum rate, which is
decomposed into two subproblems, i.e., the user resource allocation and the
phase shift optimization problem of RIS components. Due to the NP-hard and
coupling relationship, we use the block coordinate descent (BCD) method to
alternately optimize the local solutions of the coalition game and the local
discrete phase search algorithm to obtain the global solution. In contrast,
most previous studies have used the coalition game algorithm to solve the
resource allocation problem alone. Simulation results show that the algorithm
performs better than the rest of the algorithms, effectively improves the
system sum rate, and achieves performance close to the optimal solution of the
traversal algorithm with low complexity.Comment: 18 page
QoS-aware User Association and Transmission Scheduling for Millimeter-Wave Train-ground Communications
With the development of wireless communication, people have put forward
higher requirements for train-ground communications in the high-speed railway
(HSR) scenarios. With the help of mobile relays (MRs) installed on the roof of
the train, the application of Millimeter-Wave (mm-wave) communication which has
rich spectrum resources to the train-ground communication system can realize
high data rate, so as to meet users' increasing demand for broad-band
multimedia access. Also, full-duplex (FD) technology can theoretically double
the spectral efficiency. In this paper, we formulate the user association and
transmission scheduling problem in the mm-wave train-ground communication
system with MR operating in the FD mode as a nonlinear programming problem. In
order to maximize the system throughput and the number of users meeting quality
of service (QoS) requirements, we propose an algorithm based on coalition game
to solve the challenging NP-hard problem, and also prove the convergence and
Nash-stable structure of the proposed algorithm. Extensive simulation results
demonstrate that the proposed coalition game based algorithm can effectively
improve the system throughput and meet the QoS requirements of as many users as
possible, so that the communication system has a certain QoS awareness.Comment: 14 page
Resource Allocation for Device-to-Device Communications in Multi-Cell Multi-Band Heterogeneous Cellular Networks
Heterogeneous cellular networks (HCNs) with millimeter wave (mm-wave)
communications are considered as a promising technology for the fifth
generation mobile networks. Mm-wave has the potential to provide multiple
gigabit data rate due to the broad spectrum. Unfortunately, additional free
space path loss is also caused by the high carrier frequency. On the other
hand, mm-wave signals are sensitive to obstacles and more vulnerable to
blocking effects. To address this issue, highly directional narrow beams are
utilized in mm-wave networks. Additionally, device-to-device (D2D) users make
full use of their proximity and share uplink spectrum resources in HCNs to
increase the spectrum efficiency and network capacity. Towards the caused
complex interferences, the combination of D2D-enabled HCNs with small cells
densely deployed and mm-wave communications poses a big challenge to the
resource allocation problems. In this paper, we formulate the optimization
problem of D2D communication spectrum resource allocation among multiple
micro-wave bands and multiple mm-wave bands in HCNs. Then, considering the
totally different propagation conditions on the two bands, a heuristic
algorithm is proposed to maximize the system transmission rate and approximate
the solutions with sufficient accuracies. Compared with other practical
schemes, we carry out extensive simulations with different system parameters,
and demonstrate the superior performance of the proposed scheme. In addition,
the optimality and complexity are simulated to further verify effectiveness and
efficiency.Comment: 13 pages, 11 figures, IEEE Transactions on Vehicular Technolog
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