602 research outputs found
User-Centric Joint Access-Backhaul Design for Full-Duplex Self-Backhauled Wireless Networks
Full-duplex self-backhauling is promising to provide cost-effective and
flexible backhaul connectivity for ultra-dense wireless networks, but also
poses a great challenge to resource management between the access and backhaul
links. In this paper, we propose a user-centric joint access-backhaul
transmission framework for full-duplex self-backhauled wireless networks. In
the access link, user-centric clustering is adopted so that each user is
cooperatively served by multiple small base stations (SBSs). In the backhaul
link, user-centric multicast transmission is proposed so that each user's
message is treated as a common message and multicast to its serving SBS
cluster. We first formulate an optimization problem to maximize the network
weighted sum rate through joint access-backhaul beamforming and SBS clustering
when global channel state information (CSI) is available. This problem is
efficiently solved via the successive lower-bound maximization approach with a
novel approximate objective function and the iterative link removal technique.
We then extend the study to the stochastic joint access-backhaul beamforming
optimization with partial CSI. Simulation results demonstrate the effectiveness
of the proposed algorithms for both full CSI and partial CSI scenarios. They
also show that the transmission design with partial CSI can greatly reduce the
CSI overhead with little performance degradation.Comment: to appear in IEEE Trans. on Communication
Heterogeneous Services Provisioning in Small Cell Networks with Cache and Mobile Edge Computing
In the area of full duplex (FD)-enabled small cell networks, limited works
have been done on consideration of cache and mobile edge communication (MEC).
In this paper, a virtual FD-enabled small cell network with cache and MEC is
investigated for two heterogeneous services, high-data-rate service and
computation-sensitive service. In our proposed scheme, content caching and FD
communication are closely combined to offer high-data-rate services without the
cost of backhaul resource. Computing offloading is conducted to guarantee the
delay requirement of users. Then we formulate a virtual resource allocation
problem, in which user association, power control, caching and computing
offloading policies and resource allocation are jointly considered. Since the
original problem is a mixed combinatorial problem, necessary variables
relaxation and reformulation are conducted to transfer the original problem to
a convex problem. Furthermore, alternating direction method of multipliers
(ADMM) algorithm is adopted to obtain the optimal solution. Finally, extensive
simulations are conducted with different system configurations to verify the
effectiveness of the proposed scheme
Distributed Virtual Resource Allocation in Small Cell Networks with Full Duplex Self-backhauls and Virtualization
Wireless network virtualization has attracted great attentions from both
academia and industry. Another emerging technology for next generation wireless
networks is in-band full duplex (FD) communications. Due to its promising
performance, FD communication has been considered as an effective way to
achieve self-backhauls for small cells. In this paper, we introduce wireless
virtualization into small cell networks, and propose a virtualized small cell
network architecture with FD self-backhauls. We formulate the virtual resource
allocation problem in virtualized small cell networks with FD self-backhauls as
an optimization problem. Since the formulated problem is a mixed combinatorial
and non-convex optimization problem, its computational complexity is high.
Moreover, the centralized scheme may suffer from signaling overhead, outdated
dynamics information, and scalability issues. To solve it efficiently, we
divide the original problem into two subproblems. For the first subproblem, we
transfer it to a convex optimization problem, and then solve it by an efficient
alternating direction method of multipliers (ADMM)-based distributed algorithm.
The second subproblem is a convex problem, which can be solved by each
infrastructure provider. Extensive simulations are conducted with different
system configurations to show the effectiveness of the proposed scheme
Ultra-Dense 5G Small Cell Deployment for Fiber and Wireless Backhaul-Aware Infrastructures
In this paper, we study the cell planning problem for a two-tier cellular
network containing two types of base stations (BSs)-- i.e. with fiber backhaul,
referred to as wired BSs (W-BSs), and BSs with wireless backhaul, referred to
as unwired-BSs (U-BSs). In-band full-duplex wireless communications is used to
connect U-BSs and W-BSs. We propose an algorithm to determine the minimum
number of W-BSs and U-BSs to satisfy given cell and capacity coverage
constraints. Furthermore, we apply our proposed non-dominated sorting genetic
algorithm II (NSGA-II) to solve both cell planning and joint cell and backhaul
planning problem to minimize the cost of planning, while maximizing the
coverage simultaneously. Additionally, the considered cell planning program is
developed into an optimization by including the problem of minimizing the cost
of fiber backhaul deployment. In order to analyze the performance of the
proposed algorithm, we study three different deployment scenarios based on
different spatial distributions of users and coverage areas. The results show
the superiority of our proposed NSGA-II algorithm for both cell planning and
joint cell and backhaul planning to other well-known optimization algorithms.
The results also reveal that there is a trade-off between cell deployment costs
and SINR/rate coverage, and W-BSs are placed in congested areas to consume less
resources for wireless backhauls. Similarly, a trade-off between cell and fiber
deployment costs and SINR/rate coverage is observed in planning. We show that
for realistic scenarios desirable solutions can be selected from the Pareto
front of the introduced multi-objective problem based on given cellular
operator policies
Joint Downlink Cell Association and Bandwidth Allocation for Wireless Backhauling in Two-Tier HetNets with Large-Scale Antenna Arrays
The problem of joint downlink cell association (CA) and wireless backhaul
bandwidth allocation (WBBA) in two-tier cellular heterogeneous networks
(HetNets) is considered. Large-scale antenna array is implemented at the macro
base station (BS), while the small cells within the macro cell range are
single-antenna BSs and they rely on over-the-air links to the macro BS for
backhauling. A sum logarithmic user rate maximization problem is investigated
considering wireless backhauling constraints. A duplex and spectrum sharing
scheme based on co-channel reverse time-division duplex (TDD) and dynamic soft
frequency reuse (SFR) is proposed for interference management in two-tier
HetNets with large-scale antenna arrays at the macro BS and wireless
backhauling for small cells. Two in-band WBBA scenarios, namely, unified
bandwidth allocation and per-small-cell bandwidth allocation scenarios, are
investigated for joint CA-WBBA in the HetNet. A two-level hierarchical
decomposition method for relaxed optimization is employed to solve the
mixed-integer nonlinear program (MINLP). Solutions based on the General
Algorithm Modeling System (GAMS) optimization solver and fast heuristics are
also proposed for cell association in the per-small-cell WBBA scenario. It is
shown that when all small cells have to use in-band wireless backhaul, the
system load has more impact on both the sum log-rate and per-user rate
performance than the number of small cells deployed within the macro cell
range. The proposed joint CA-WBBA algorithms have an optimal load approximately
equal to the size of the large-scale antenna array at the macro BS. The cell
range expansion (CRE) strategy, which is an efficient cell association scheme
for HetNets with perfect backhauling, is shown to be inefficient when in-band
wireless backhauling for small cells comes into play.Comment: IEEE Transactions on Wireless Communications, to appea
Analysis of Massive MIMO-Enabled Downlink Wireless Backhauling for Full-Duplex Small Cells
Using tools from stochastic geometry, we develop a framework to model the
downlink rate coverage probability of a user in a given small cell network
(SCN) with massive MIMO-enabled wireless backhauls. The considered SCN is
composed of a mixture of small cells that are configured in either in-band or
out-of-band backhaul modes with a certain probability. The performance of the
user in the considered hierarchical network is limited by several sources of
interference such as the backhaul interference, small cell base station
(SBS)-to-SBS interference and the SI. Moreover, due to the channel hardening
effect in massive MIMO, the backhaul links experience long term channel effects
only, whereas the access links experience both the long term and short term
channel effects. Consequently, the developed framework is flexible to
characterize different sources of interference while capturing the
heterogeneity of the access and backhaul channels. In specific scenarios, the
framework enables deriving closed-form coverage probability expressions. Under
perfect backhaul coverage, the simplified expressions are utilized to optimize
the proportion of in-band and out-of-band small cells in the SCN in
closed-form. Finally, few remedial solutions are proposed that can potentially
mitigate the backhaul interference and in turn improve the performance of
in-band FD wireless backhauling. Numerical results investigate the scenarios in
which in-band wireless backhauling is useful and demonstrate that maintaining a
correct proportion of in-band and out-of-band FD small cells is crucial in
wireless backhauled SCNs.Comment: 15 pages, 7 figures, IEEE Transactions on Communication
Max-Min Rates in Self-backhauled Millimeter Wave Cellular Networks
This paper considers the following question for viable wide-area millimeter
wave cellular networks. What is the maximum extended coverage area of a single
fiber site using multi-hop relaying, while achieving a minimum target per user
data rate? We formulate an optimization problem to maximize the minimum
end-to-end per user data rate, and exploit unique features of millimeter wave
deployments to yield a tractable solution. The mesh network is modeled as a
ring urban-canyon type deployment, where is the number of hops back to
the fiber site. The total number of relays per fiber site grows as . We
consider both integrated access-backhaul (IAB) and orthogonal access-backhaul
(OAB) resource allocation strategies, as well as both half and full duplex base
stations (BSs). With a few validated simplifications, our results are given as
simple closed-form expressions that are easy to evaluate even for large
networks. Several design guidelines are provided, including on the choice of
routing and scheduling strategy, the maximum allowable self-interference in
full duplex relays and role of dual connectivity to reduce load imbalance
across BSs. For example, we show that for certain load conditions there is very
little gain to IAB (as considered for 5G) as opposed to tunable OAB (using
separate spectrum for access and backhaul links); the latter being
significantly simpler to implement.Comment: under review, major revision, submitted to IEEE Trans. Wireless
Commu
A Survey of Millimeter Wave (mmWave) Communications for 5G: Opportunities and Challenges
With the explosive growth of mobile data demand, the fifth generation (5G)
mobile network would exploit the enormous amount of spectrum in the millimeter
wave (mmWave) bands to greatly increase communication capacity. There are
fundamental differences between mmWave communications and existing other
communication systems, in terms of high propagation loss, directivity, and
sensitivity to blockage. These characteristics of mmWave communications pose
several challenges to fully exploit the potential of mmWave communications,
including integrated circuits and system design, interference management,
spatial reuse, anti-blockage, and dynamics control. To address these
challenges, we carry out a survey of existing solutions and standards, and
propose design guidelines in architectures and protocols for mmWave
communications. We also discuss the potential applications of mmWave
communications in the 5G network, including the small cell access, the cellular
access, and the wireless backhaul. Finally, we discuss relevant open research
issues including the new physical layer technology, software-defined network
architecture, measurements of network state information, efficient control
mechanisms, and heterogeneous networking, which should be further investigated
to facilitate the deployment of mmWave communication systems in the future 5G
networks.Comment: 17 pages, 8 figures, 7 tables, Journal pape
Fronthaul-Aware Group Sparse Precoding and Signal Splitting in SWIPT C-RAN
We investigate the precoding, remote radio head (RRH) selection and signal
splitting in the simultaneous wireless information and power transferring
(SWIPT) cloud radio access networks \mbox{(C-RANs)}. The objective is to
minimize the power consumption of the SWIPT C-RAN. Different from the existing
literature, we consider the nonlinear fronthaul power consumption and the
multiple antenna RRHs. By switching off the unnecessary RRHs, the group
sparsity of the precoding coefficients is introduced, which indicates that the
precoding process and the RRH selection are coupled. In order to overcome these
issues, a group sparse precoding and signal splitting algorithm is proposed
based on the majorization-minimization framework, and the convergence behavior
is established. Numerical results are used to verify our proposed studies.Comment: Accepted by IEEE Globecom 201
Wireless Backhaul in 5G and Beyond: Issues, Challenges and Opportunities
With the introduction of new technologies such as Unmanned Aerial Vehicle
(UAV), High Altitude Platform Station (HAPS), Millimeter Wave (mmWave)
frequencies, Massive Multiple-Input Multiple-Output (mMIMO), and beamforming,
wireless backhaul is expected to be an integral part of the 5G networks. While
this concept is nothing new, it was shortcoming in terms of performance
compared to the fiber backhauling. However, with these new technologies, fiber
is no longer the foremost technology for backhauling. With the projected
densification of networks, wireless backhaul has become mandatory to use. There
are still challenges to be tackled if wireless backhaul is to be used
efficiently. Resource allocation, deployment, scheduling, power management and
energy efficiency are some of these problems. Wireless backhaul also acts as an
enabler for new technologies and improves some of the existing ones
significantly. To name a few, rural connectivity, satellite communication, and
mobile edge computing are some concepts for which wireless backhauling acts as
an enabler. Small cell usage with wireless backhaul presents different security
challenges. Governing bodies of cellular networks have standardization efforts
going on especially for the Integrated Acces-Backhaul (IAB) concept, and this
is briefly mentioned. Finally, wireless backhaul is also projected to be an
important part of the beyond 5G networks, and newly developed concepts such as
cell-free networking, ultra-massive MIMO, and extremely dense network show this
trend as well. In this survey, we present the aforementioned issues,
challenges, opportunities, and applications of wireless backhaul in 5G, while
briefly mentioning concepts related to wireless backhaul beyond 5G alongside
with security and standardization issues
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