867 research outputs found
Interference Management with Partial Uplink/Downlink Spectrum Overlap
Simultaneous reuse of spectral resources by uplink and downlink, denoted as
in-band full duplex (FD) communication, is promoted to double the spectral
efficiency when compared to its half-duplex (HD) counterpart. Interference
management, however, remains challenging in FD cellular networks, especially
when high disparity between uplink and downlink transmission powers exists. The
uplink performance can be particularly deteriorated when operating on channels
that are simultaneously occupied with downlink transmission. This paper
considers a cellular wireless system with partial spectrum overlap between the
downlink and uplink. The performance of the system becomes, therefore, a
function of the overlap fraction, as well as the power level of both the uplink
and downlink transmissions. The paper considers the problem of maximizing an
overall network utility to find the uplink/downlink transmission powers and the
spectrum overlap fraction between the uplink and downlink spectrum in each
cell, and proposes solving the problem using interior point method. Simulations
results confirm the vulnerability of the uplink performance to the FD
operation, and show the superiority of the proposed scheme over the FD and HD
schemes. The results further show that explicit uplink and downlink performance
should be considered for efficient design of cellular networks with overlapping
uplink/downlink resources
Leveraging One-hop Information in Massive MIMO Full-Duplex Wireless Systems
We consider a single-cell massive MIMO full-duplex wireless communication
system, where the base-station (BS) is equipped with a large number of
antennas. We consider the setup where the single-antenna mobile users operate
in half- duplex, while each antenna at the BS is capable of full-duplex
transmissions, i.e., it can transmit and receive simultaneously using the same
frequency spectrum. The fundamental challenge in this system is intra-cell
inter-node interference, generated by the transmissions of uplink users to the
receptions at the downlink users. The key operational challenge is estimating
and aggregating inter-mobile channel estimates, which can potentially overwhelm
any gains from full-duplex operation.
In this work, we propose a scalable and distributed scheme to optimally
manage the inter-node interference by utilizing a "one- hop information
architecture". In this architecture, the BS only needs to know the
signal-to-interference-plus-noise ratio (SINR) from the downlink users. Each
uplink user needs its own SINR, along with a weighted signal-plus-noise metric
from its one-hop neighboring downlink users, which are the downlink users that
it interferes with. The proposed one-hop information architecture does not
require any network devices to comprehensively gather the vast inter-node
interference channel knowledge, and hence significantly reduces the overhead.
Based on the one-hop information architecture, we design a distributed power
control algorithm and implement such architecture using overheard feedback
information. We show that, in typical asymptotic regimes with many users and
antennas, the proposed distributed power control scheme improves the overall
network utility and reduces the transmission power of the uplink users.Comment: Submitted to IEEE/ACM Transactions on Networkin
Full-Duplex Non-Orthogonal Multiple Access for Modern Wireless Networks
Non-orthogonal multiple access (NOMA) is an interesting concept to provide
higher capacity for future wireless communications. In this article, we
consider the feasibility and benefits of combining full-duplex operation with
NOMA for modern communication systems. Specifically, we provide a comprehensive
overview on application of full-duplex NOMA in cellular networks, cooperative
and cognitive radio networks, and characterize gains possible due to
full-duplex operation. Accordingly, we discuss challenges, particularly the
self-interference and inter-user interference and provide potential solutions
to interference mitigation and quality-of-service provision based on
beamforming, power control, and link scheduling. We further discuss future
research challenges and interesting directions to pursue to bring full-duplex
NOMA into maturity and use in practice.Comment: Revised, IEEE Wireless Communication Magazin
Joint User Scheduling and Power optimization in Full-Duplex Cells with Successive Interference Cancellation
This paper considers a cellular system with a full-duplex base station and
half-duplex users. The base station can activate one user in uplink or downlink
(half-duplex mode), or two different users one in each direction simultaneously
(full-duplex mode). Simultaneous transmissions in uplink and downlink causes
self-interference at the base station and uplink-to-downlink interference at
the downlink user. Although uplink-to-downlink interference is typically
treated as noise, it is shown that successive interference decoding and
cancellation (SIC mode) can lead to significant improvement in network utility,
especially when user distribution is concentrated around a few hotspots. The
proposed temporal fair user scheduling algorithm and corresponding power
optimization utilizes full-duplex and SIC modes as well as half-duplex
transmissions based on their impact on network utility. Simulation results
reveal that the proposed strategy can achieve up to 95% average cell throughput
improvement in typical indoor scenarios with respect to a conventional network
in which the base station is half-duplex.Comment: To be appeared in IEEE Asilomar Conference on Signals, Systems, and
Computers, 201
Distributed Spectral Efficiency Maximization in Full-Duplex Cellular Networks
Three-node full-duplex is a promising new transmission mode between a
full-duplex capable wireless node and two other wireless nodes that use
half-duplex transmission and reception respectively. Although three-node
full-duplex transmissions can increase the spectral efficiency without
requiring full-duplex capability of user devices, inter-node interference - in
addition to the inherent self-interference - can severely degrade the
performance. Therefore, as methods that provide effective self-interference
mitigation evolve, the management of inter-node interference is becoming
increasingly important. This paper considers a cellular system in which a
full-duplex capable base station serves a set of half-duplex capable users. As
the spectral efficiencies achieved by the uplink and downlink transmissions are
inherently intertwined, the objective is to device channel assignment and power
control algorithms that maximize the weighted sum of the uplink-downlink
transmissions. To this end a distributed auction based channel assignment
algorithm is proposed, in which the scheduled uplink users and the base station
jointly determine the set of downlink users for full-duplex transmission.
Realistic system simulations indicate that the spectral efficiency can be up to
89% better than using the traditional half-duplex mode. Furthermore, when the
self-interference cancelling level is high, the impact of the user-to-user
interference is severe unless properly managed.Comment: 7 pages, 3 figures, accepted in IEEE ICC 2016 - Workshop on Novel
Medium Access and Resource Allocation for 5G Network
User Selection and Power Allocation in Full Duplex Multi-Cell Networks
Full duplex (FD) communications has the potential to double the capacity of a
half duplex (HD) system at the link level. However, in a cellular network, FD
operation is not a straightforward extension of half duplex operations. The
increased interference due to a large number of simultaneous transmissions in
FD operation and realtime traffic conditions limits the capacity improvement.
Realizing the potential of FD requires careful coordination of resource
allocation among the cells as well as within the cell. In this paper, we
propose a distributed resource allocation, i.e., joint user selection and power
allocation for a FD multi-cell system, assuming FD base stations (BSs) and HD
user equipment (UEs). Due to the complexity of finding the globally optimum
solution, a sub-optimal solution for UE selection, and a novel geometric
programming based solution for power allocation, are proposed. The proposed
distributed approach converges quickly and performs almost as well as a
centralized solution, but with much lower signaling overhead. It provides a
hybrid scheduling policy which allows FD operations whenever it is
advantageous, but otherwise defaults to HD operation. We focus on small cell
systems because they are more suitable for FD operation, given practical
self-interference cancellation limits.With practical self-interference
cancellation, it is shown that the proposed hybrid FD system achieves nearly
two times throughput improvement for an indoor multi-cell scenario, and about
65% improvement for an outdoor multi-cell scenario compared to the HD system.Comment: 15 pages, to be published in IEEE Transactions on Vehicular
Technology, 2016. arXiv admin note: text overlap with arXiv:1412.870
Full-Duplex Communications: Performance in Ultra-Dense Small-Cell Wireless Networks
Theoretically, full-duplex (FD) communications can double the
spectral-efficiency (SE) of a wireless link if the problem of self-interference
(SI) is completely eliminated. Recent developments towards SI cancellation
techniques have allowed to realize the FD communications on low-power
transceivers, such as small-cell (SC) base stations. Consequently, the FD
technology is being considered as a key enabler of 5G and beyond networks. In
the context of 5G, FD communications have been initially investigated in a
single SC and then into multiple SC environments. Due to FD operations, a
single SC faces residual SI and intra-cell co-channel interference (CCI),
whereas multiple SCs face additional inter-cell CCI, which grows with the
number of neighboring cells. The surge of interference in the multi-cell
environment poses the question of the feasibility of FD communications. In this
article, we first review the FD communications in single and multiple SC
environments and then provide the state-of-the-art for the CCI mitigation
techniques, as well as FD feasibility studies in a multi-cell environment.
Further, through numerical simulations, the SE performance gain of the FD
communications in ultra-dense massive multiple input multiple-output enabled
millimeter wave SCs is presented. Finally, potential open research challenges
of multi-cell FD communications are highlighted.Comment: Accepted for publication in IEEE Vehicular Technology Magazine,
Special Issue on 5G Technologies and Application
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
Intelligent Wireless Communications Enabled by Cognitive Radio and Machine Learning
The ability to intelligently utilize resources to meet the need of growing
diversity in services and user behavior marks the future of wireless
communication systems. Intelligent wireless communications aims at enabling the
system to perceive and assess the available resources, to autonomously learn to
adapt to the perceived wireless environment, and to reconfigure its operating
mode to maximize the utility of the available resources. The perception
capability and reconfigurability are the essential features of cognitive radio
while modern machine learning techniques project great potential in system
adaptation. In this paper, we discuss the development of the cognitive radio
technology and machine learning techniques and emphasize their roles in
improving spectrum and energy utility of wireless communication systems. We
describe the state-of-the-art of relevant techniques, covering spectrum sensing
and access approaches and powerful machine learning algorithms that enable
spectrum- and energy-efficient communications in dynamic wireless environments.
We also present practical applications of these techniques and identify further
research challenges in cognitive radio and machine learning as applied to the
existing and future wireless communication systems
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
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