22,648 research outputs found
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
SoftNull: Many-Antenna Full-Duplex Wireless via Digital Beamforming
In this paper, we present and study a digital-controlled method, called
SoftNull, to enable full-duplex in many-antenna systems. Unlike most designs
that rely on analog cancelers to suppress self-interference, SoftNull relies on
digital transmit beamforming to reduce self-interference. SoftNull does not
attempt to perfectly null self-interference, but instead seeks to reduce
self-interference sufficiently to prevent swamping the receiver's dynamic
range. Residual self-interference is then cancelled digitally by the receiver.
We evaluate the performance of SoftNull using measurements from a 72-element
antenna array in both indoor and outdoor environments. We find that SoftNull
can significantly outperform half-duplex for small cells operating in the
many-antenna regime, where the number of antennas is many more than the number
of users served simultaneously
Throughput and Coverage for a Mixed Full and Half Duplex Small Cell Network
Recent advances in self-interference cancellation enable radios to transmit
and receive on the same frequency at the same time. Such a full duplex radio is
being considered as a potential candidate for the next generation of wireless
networks due to its ability to increase the spectral efficiency of wireless
systems. In this paper, the performance of full duplex radio in small cellular
systems is analyzed by assuming full duplex capable base stations and half
duplex user equipment. However, using only full duplex base stations increases
interference leading to outage. We therefore propose a mixed multi-cell system,
composed of full duplex and half duplex cells. A stochastic geometry based
model of the proposed mixed system is provided, which allows us to derive the
outage and area spectral efficiency of such a system. The effect of full duplex
cells on the performance of the mixed system is presented under different
network parameter settings. We show that the fraction of cells that have full
duplex base stations can be used as a design parameter by the network operator
to target an optimal tradeoff between area spectral efficiency and outage in a
mixed system.Comment: 9 Pages, a short version of this paper has been accepted in ICC 201
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
Joint Backhaul-Access Analysis of Full Duplex Self-Backhauling Heterogeneous Networks
With the successful demonstration of in-band full-duplex (IBFD) transceivers,
a new research dimension has been added to wireless networks. This paper
proposes an interesting use case of this capability for IBFD self-backhauling
heterogeneous networks (HetNet). IBFD self-backhauling in a HetNet refers to
IBFD-enabled small cells backhauling themselves with macro cells over the
wireless channel. Owing to their IBFD capability, the small cells
simultaneously communicate over the access and backhaul links, using the same
frequency band. The idea is doubly advantageous, as it obviates the need for
fiber backhauling small cells every hundred meters and allows the access
spectrum to be reused for backhauling at no extra cost. This work considers the
case of a two-tier cellular network with IBFD-enabled small cells, wirelessly
backhauling themselves with conventional macro cells. For clear exposition, the
case considered is that of FDD network, where within access and backhaul links,
the downlink (DL) and uplink (UL) are frequency duplexed (,
respectively), while the total frequency spectrum used at access and backhaul
() is the same. Analytical expressions for coverage and average downlink
(DL) rate in such a network are derived using tools from the field of
stochastic geometry. It is shown that DL rate in such networks could be close
to double that of a conventional TDD/FDD self-backhauling network, at the
expense of reduced coverage due to higher interference in IBFD networks. For
the proposed IBFD network, the conflicting aspects of increased interference on
one side and high spectral efficiency on the other are captured into a
mathematical model. The mathematical model introduces an end-to-end joint
analysis of backhaul (or fronthaul) and access links, in contrast to the
largely available access-centric studies.Comment: Remodeled using different large-scale path loss exponents for the
Macro Base Station tier and the Pico Base Station Tier. Other formatting
improvements. Submitted to IEEE Transactions on Wireless Communicatio
Full-Duplex Cloud Radio Access Networks: An Information-Theoretic Viewpoint
The conventional design of cellular systems prescribes the separation of
uplink and downlink transmissions via time-division or frequency-division
duplex. Recent advances in analog and digital domain self-interference
interference cancellation challenge the need for this arrangement and open up
the possibility to operate base stations, especially low-power ones, in a
full-duplex mode. As a means to cope with the resulting downlink-to-uplink
interference among base stations, this letter investigates the impact of the
Cloud Radio Access Network (C-RAN) architecture. The analysis follows an
information theoretic approach based on the classical Wyner model. The
analytical results herein confirm the significant potential advantages of the
C-RAN architecture in the presence of full-duplex base stations, as long as
sufficient fronthaul capacity is available and appropriate mobile station
scheduling, or successive interference cancellation at the mobile stations, is
implemented.Comment: To appear in IEEE Wireless Communications Letter
Harvest the potential of massive MIMO with multi-layer techniques
Massive MIMO is envisioned as a promising technology for 5G wireless networks
due to its high potential to improve both spectral and energy efficiency.
Although the massive MIMO system is based on innovations in the physical layer,
the upper layer techniques also play important roles in harvesting the
performance gains of massive MIMO. In this article, we begin with an analysis
of the benefits and challenges of massive MIMO systems. We then investigate the
multi-layer techniques for incorporating massive MIMO in several important
network deployment scenarios. We conclude this article with a discussion of
open and potential problems for future research.Comment: IEEE Networ
On Improving Capacity of Full-Duplex Small Cells with D2D
The recent developments in full duplex (FD) communication promise doubling
the capacity of cellular networks using self interference cancellation (SIC)
techniques. FD small cells with device-to-device (D2D) communication links
could achieve the expected capacity of the future cellular networks (5G). In
this work, we consider joint scheduling and dynamic power algorithm (DPA) for a
single cell FD small cell network with D2D links (D2DLs). We formulate the
optimal user selection and power control as a non-linear programming (NLP)
optimization problem to get the optimal user scheduling and transmission power
in a given TTI. Our numerical results show that using DPA gives better overall
throughput performance than full power transmission algorithm (FPA). Also,
simultaneous transmissions (combination of uplink (UL), downlink (DL), and D2D
occur 80% of the time thereby increasing the spectral efficiency and network
capacity.Comment: Submitted to IEEE Globecom Conference 201
Area Spectral Efficiency and Coverage for Mixed Duplexing Networks with Directional Transmissions
In this paper, we consider a system of small cells assuming full duplex (FD)
capable base stations (BSs) and half duplex (HD) user equipment (UEs). We
investigate a mixed duplexing cellular system composed of FD and HD cells, when
BSs are using directional transmissions. A stochastic geometry based model of
the proposed system is used to derive the coverage and area spectral efficiency
(ASE) of both BSs and UEs. The effect of FD cells on the performance of the
mixed system is presented under different degree of directionality at the BSs.
We show that enabling directional transmissions at the BSs yields significant
ASE and coverage gain in both downlink and uplink directions. With directional
transmissions, the ASE increases rapidly with the number of FD cells while the
drop in the coverage rate due to FD operations reduces significantly.Comment: will be appeared in the proceedings of IEEE PIMRC 201
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