3,957 research outputs found
Successive Interference Cancellation in Heterogeneous Cellular Networks
At present, operators address the explosive growth of mobile data demand by
densification of the cellular network so as to reduce the transmitter-receiver
distance and to achieve higher spectral efficiency. Due to such network
densification and the intense proliferation of wireless devices, modern
wireless networks are interference-limited, which motivates the use of
interference mitigation and coordination techniques. In this work, we develop a
statistical framework to evaluate the performance of multi-tier heterogeneous
networks with successive interference cancellation (SIC) capabilities,
accounting for the computational complexity of the cancellation scheme and
relevant network related parameters such as random location of the access
points (APs) and mobile users, and the characteristics of the wireless
propagation channel. We explicitly model the consecutive events of canceling
interferers and we derive the success probability to cancel the n-th strongest
signal and to decode the signal of interest after n cancellations. When users
are connected to the AP which provides the maximum average received signal
power, the analysis indicates that the performance gains of SIC diminish
quickly with n and the benefits are modest for realistic values of the
signal-to-interference ratio (SIR). We extend the statistical model to include
several association policies where distinct gains of SIC are expected: (i)
minimum load association, (ii) maxi- mum instantaneous SIR association, and
(iii) range expansion. Numerical results show the effectiveness of SIC for the
considered association policies. This work deepens the understanding of SIC by
defining the achievable gains for different association policies in multi-tier
heterogeneous networks.Comment: submitted for journal publication, 13 pages, 6 figure
Relaying Strategies for Uplink in Wireless Cellular Networks
In this paper, we analyze the impact of relays on the uplink performance of
FDMA cellular networks. We focus our analysis on Decode and Forward techniques,
with the aim of measuring the improvements which can be achieved in terms of
throughput and energy saving. We apply a stochastic geometry based approach to
a scenario with inter-cell interference and reuse factor equal to 1. The first
goal of this work is to observe what is the impact of various relay features,
such as transmission power, location and antenna pattern, when a half-duplex
constraint is imposed. The second goal is to determine how much relaying can be
beneficial also for users who are not at the cell edge, and who can therefore
use a direct link towards the base station. We show that if more refined
decoding techniques, such as Successive Interference Cancellation and
Superposition Coding, are properly used, considerable gains can be obtained for
these mobiles as well.Comment: 30 pages, 10 figure
Distributed Iterative Detection Based on Reduced Message Passing for Networked MIMO Cellular Systems
This paper considers base station cooperation (BSC) strategies for the uplink
of a multi-user multi-cell high frequency reuse scenario where distributed
iterative detection (DID) schemes with soft/hard interference cancellation
algorithms are studied. The conventional distributed detection scheme exchanges
{soft symbol estimates} with all cooperating BSs. Since a large amount of
information needs to be shared via the backhaul, the exchange of hard bit
information is preferred, however a performance degradation is experienced. In
this paper, we consider a reduced message passing (RMP) technique in which each
BS generates a detection list with the probabilities for the desired symbol
that are sorted according to the calculated probability. The network then
selects the best {detection candidates} from the lists and conveys the index of
the constellation symbols (instead of double-precision values) among the
cooperating cells. The proposed DID-RMP achieves an inter-cell-interference
(ICI) suppression with low backhaul traffic overhead compared with {the
conventional soft bit exchange} and outperforms the previously reported
hard/soft information exchange algorithms.Comment: 9 pages, 6 figures. IEEE Transactions on Vehicular Technology, 201
Full-Duplex eNodeB and UE Design for 5G Networks
The recent progress in the area of self-interference cancellation (SIC)
design has enabled the development of full-duplex (FD) single and multiple
antenna systems. In this paper, we propose a design for FD eNodeB (eNB) and
user equipment (UE) for 5G networks. The use of FD operation enables
simultaneous in-band uplink and downlink operation and thereby cutting down the
spectrum requirement by half. FD operation requires the same subcarrier
allocation to UE in both uplink and downlink. Long Term Evolution LTE) uses
orthogonal frequency division multiple access (OFDMA) for downlink. To enable
FD operation, we propose using single carrier frequency division multiple
access SC-FDMA) for downlink along with the conventional method of using it for
uplink. Taking advantage of channel reciprocity, singular value decomposition
(SVD) based eamforming in the downlink allows multiple users (MU) to operate on
same set of subcarriers. In uplink, frequency domain minimum mean square error
(MMSE) equalizer along with successive interference cancellation with optimal
ordering (SSIC-OO) algorithm is used to decouple signals of users operating in
the same set of subcarriers. The work includes simulations showing efficient FD
operation both at UE and eNB for downlink and uplink respectively.Comment: 7 pages and 6 figures, Accepted and will also be available in
proceedings of Wireless Telecommunications Symposium (WTS) 201
Performance Analysis of Non-Orthogonal Multicast in Two-tier Heterogeneous Networks
With the explosive growth of mobile services, non-orthogonal
broadcast/multicast transmissions can effectively improves spectrum efficiency.
Nonorthogonal multiple access (NOMA) represents a paradigm shift from
conventional orthogonal multiple-access (OMA) concepts and has been recognized
as one of the key enabling technologies for fifth-generation (5G) mobile
networks. In this paper, a two-tier heterogeneous network is studied, in which
the wireless signal power is partitioned by the NOMA scheme. Moreover, the
coverage probability, the average rate and the average QoE are derived to
evaluate network performance. Simulation results show that compared with the
OMA method, non-orthogonal broadcast/multicast method improve both the average
user rate and QoE in the two-tier heterogeneous network
Femtocell Architectures with Spectrum Sharing for Cellular Radio Networks
Femtocells are an emerging technology aimed at providing gains to both
network operators and end-users. These gains come at a cost of increased
interference, specifically the cross network interference between the macrocell
and femtocell networks. This interference is one of the main performance
limiting factors in allowing an underlaid femtocell network to share the
spectrum with the cellular network. To manage this interference, we first
propose a femtocell architecture that orthog- onally partitions the network
bandwidth between the macrocell and femtocell networks. This scheme eliminates
the cross network interference thus giving the femtocells more freedom over
their use of the spectrum. Specifically, no interference constraint is imposed
by the cellular network allowing femto users to transmit at a constant power on
randomly selected channels. Although simple, this scheme is enough to give
gains up to 200% in sum rate.
We then propose a second architecture where both networks share the bandwidth
simultaneously. A femtocell power control scheme that relies on minimal
coordination with the macrocell base station is used in conjunction with an
interference sensing channel assignment mechanism. These two schemes together
yield sum rate gains up to 200%. We then develop a technique for macro users to
join a nearby femtocell and share a common chan- nel with a femtocell user
through the use of successive interfer- ence cancellation. By adding this
mechanism to the power control and channel assignment schemes, we show sum rate
gains over 300% and up to 90% power savings for macrocell users.Comment: 9 pages, 8 figures, Accepted to the International Journal of Advances
in Engineering Sciences and Applied Mathematics special issue on
Multi-Terminal Information Theor
Detection and Estimation Algorithms in Massive MIMO Systems
This book chapter reviews signal detection and parameter estimation
techniques for multiuser multiple-antenna wireless systems with a very large
number of antennas, known as massive multi-input multi-output (MIMO) systems.
We consider both centralized antenna systems (CAS) and distributed antenna
systems (DAS) architectures in which a large number of antenna elements are
employed and focus on the uplink of a mobile cellular system. In particular, we
focus on receive processing techniques that include signal detection and
parameter estimation problems and discuss the specific needs of massive MIMO
systems. Simulation results illustrate the performance of detection and
estimation algorithms under several scenarios of interest. Key problems are
discussed and future trends in massive MIMO systems are pointed out.Comment: 7 figures, 14 pages. arXiv admin note: substantial text overlap with
arXiv:1310.728
Performance of Network-Assisted Full-Duplex for Cell-Free Massive MIMO
Network assisted full-duplex (NAFD) is a spatial-division duplex technique
for future wireless networks with cell-free massive multiple-input
multiple-output (CF massive MIMO) network, where a large number of remote
antenna units (RAUs), either using half-duplex or full-duplex, jointly support
truly flexible duplex including time-division duplex, frequency-division duplex
and full duplex on demand of uplink and downlink traffic by using network MIMO
methods. With NAFD, bi-directional data rates of the wireless network could be
increased and end-to-end delay could be reduced. In this paper, the spectral
efficiency of NAFD communications in CF massive MIMO network with imperfect
channel state information (CSI) is investigated under spatial correlated
channels. Based on large dimensional random matrix theory, the deterministic
equivalents for the uplink sum-rate with minimum-mean-square-error (MMSE)
receiver as well as the downlink sum-rate with zero-forcing (ZF) and
regularized zero-forcing (RZF) beamforming are derived. Numerical results show
that under various environmental settings, the deterministic equivalents are
accurate in both a large-scale system and system with a finite number of
antennas. It is also shown that with the downlink-to-uplink interference
cancellation, the uplink spectral efficiency of CF massive MIMO with NAFD could
be improved. The spectral efficiencies of NAFD with different duplex
configurations such as in-band full-duplex, and half-duplex are compared. With
the same total numbers of transmit and receive antennas, NAFD with half-duplex
RAUs offers a higher spectral efficiency. To alleviate the uplink-to-downlink
interference, a novel genetic algorithm based user scheduling strategy (GAS) is
proposed. Simulation results show that the achievable downlink sum-rate by
using the GAS is greatly improved compared to that by using the random user
scheduling
Full-Duplex Transceiver for Future Cellular Network: A Smart Antenna Approach
In this paper, we propose a transceiver architecture for full-duplex (FD)
eNodeB (eNB) and FD user equipment (UE) transceiver. For FD
communication,.i.e., simultaneous in-band uplink and downlink operation, same
subcarriers can be allocated to UE in both uplink and downlink. Hence, contrary
to traditional LTE, we propose using single-carrier frequency division multiple
accesses (SC-FDMA) for downlink along with the conventional method of using it
for uplink. The use of multiple antennas at eNB and singular value
decomposition (SVD) in the downlink allows multiple users (MU) to operate on
the same set of ubcarriers. In the uplink, successive interference cancellation
with optimal ordering (SSIC-OO) algorithm is used to decouple signals of UEs
operating in the same set of subcarriers. A smart antenna approach is adopted
which prevents interference, in downlink of a UE, from uplink signals of other
UEs sharing same subcarriers. The approach includes using multiple antennas at
UEs to form directed beams towards eNode and nulls towards other UEs. The
proposed architecture results in significant improvement of the overall
spectrum efficiency per cell of the cellular network.Comment: arXiv admin note: text overlap with arXiv:1506.0213
Large-Scale NOMA: Promises for Massive Machine-Type Communication
We investigate on large-scale deployment of non-orthogonal multiple access
(NOMA) for improved spectral and power efficiency in cellular networks to
provide massive wireless connectivity (e.g. for machine-type communication
[mMTC]). First, we describe the basics of single-antenna NOMA technology and
its extension to co-located multiple-antenna NOMA as well as coordinated
multipoint transmission (CoMP)-enabled NOMA technologies. Then we discuss some
of the practical challenges of large-scale deployment of NOMA such as the
inter-NOMA-interference (INI), inter-cell interference, and hardware
implementation complexity. To this end, we present one key enabling technique
to overcome the challenges of large-scale deployment of NOMA. Generally
speaking, for a feasible large-scale NOMA implementation, sophisticated
diversity enhancing techniques can be used to compensate for the degradation in
coding gain and to decrease the complexity resulting from excessive INI and
increased level of required successive interference cancellation (SIC).
Furthermore, to massively extend NOMA over the network coverage area, NOMA
transmitters have to cooperate in a generalized manner to serve all nearby
users simultaneously
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