18 research outputs found
Buffer-Aided Relay Selection Algorithms for Physical-Layer Security in Wireless Networks
In this work, we consider the use of buffer-aided relays, linear precoding
techniques and multiple antennas for physical-layer security in wireless
networks. We develop relay selection algorithms to improve the secrecy-rate
performance of cooperative multi-user multiple-antenna wireless networks. In
particular, we propose a novel finite buffer-aided relay selection algorithm
that employs the maximum likelihood (ML) criterion to select sets of relays
which fully exploit the flexibility offered by relay nodes equipped with
buffers. Numerical results show the benefits of the proposed techniques as
compared to prior art.Comment: 5 pages, 3 figures in WSA 201
Coordinate Tomlinson-Harashima Precoding Design for Overloaded Multi-user MIMO Systems
Tomlinson-Harashima precoding (THP) is a nonlinear processing technique
employed at the transmit side to implement the concept of dirty paper coding
(DPC). The perform of THP, however, is restricted by the dimensionality
constraint that the number of transmit antennas has to be greater or equal to
the total number of receive antennas. In this paper, we propose an iterative
coordinate THP algorithm for the scenarios in which the total number of receive
antennas is larger than the number of transmit antennas. The proposed algorithm
is implemented on two types of THP structures, the decentralized THP (dTHP)
with diagonal weighted filters at the receivers of the users, and the
centralized THP (cTHP) with diagonal weighted filter at the transmitter.
Simulation results show that a much better bit error rate (BER) and sum-rate
performances can be achieved by the proposed iterative coordinate THP compared
to the previous linear art.Comment: 3 figures, 6 pages, ISWCS 2014. arXiv admin note: text overlap with
arXiv:1401.475
Study of Joint MSINR and Relay Selection Algorithms for Distributed Beamforming
This paper presents joint maximum signal-to-interference-plus-noise ratio
(MSINR) and relay selection algorithms for distributed beamforming. We propose
a joint MSINR and restricted greedy search relay selection (RGSRS) algorithm
with a total relay transmit power constraint that iteratively optimizes both
the beamforming weights at the relays nodes, maximizing the SINR at the
destination. Specifically, we devise a relay selection scheme that based on
greedy search and compare it to other schemes like restricted random relay
selection (RRRS) and restricted exhaustive search relay selection (RESRS). A
complexity analysis is provided and simulation results show that the proposed
joint MSINR and RGSRS algorithm achieves excellent bit error rate (BER) and
SINR performances.Comment: 7 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1707.0095
Multi-User Flexible Coordinated Beamforming using Lattice Reduction for Massive MIMO Systems
The application of precoding algorithms in multi-user massive multiple-input
multiple-output (MU-Massive-MIMO) systems is restricted by the dimensionality
constraint that the number of transmit antennas has to be greater than or equal
to the total number of receive antennas. In this paper, a lattice reduction
(LR)-aided flexible coordinated beamforming (LR-FlexCoBF) algorithm is proposed
to overcome the dimensionality constraint in overloaded MU-Massive-MIMO
systems. A random user selection scheme is integrated with the proposed
LR-FlexCoBF to extend its application to MU-Massive-MIMO systems with arbitary
overloading levels. Simulation results show that significant improvements in
terms of bit error rate (BER) and sum-rate performances can be achieved by the
proposed LR-FlexCoBF precoding algorithm.Comment: 5 figures, Eusipc
Study of BEM-Type Channel Estimation Techniques for 5G Multicarrier Systems
In this paper, we investigate channel estimation techniques for 5G
multicarrier systems. Due to the characteristics of the 5G application
scenarios, channel estimation techniques have been tested in Orthogonal
Frequency Division Multiplexing (OFDM) and Generalized Frequency Division
Multiplexing (GFDM) systems. The orthogonality between subcarriers in OFDM
systems permits inserting and extracting pilots without interference. However,
due to pulse shaping, subcarriers in GFDM are no longer orthogonal and
interfere with each other. Due to such interference, the channel estimation for
GFDM is not trivial. A robust and low-complexity channel estimator can be
obtained by combining a minimum mean-square error (MMSE) regularization and the
basis expansion model (BEM) approach. In this work, we develop a BEM-type
channel estimator along with a strategy to obtain the covariance matrix of the
BEM coefficients. Simulations show that the BEM-type channel estimation shows
performance close to that of the linear MMSE (LMMSE), even though there is no
need to know the channel power delay profile, and its complexity is low.Comment: 2 figures, 7 page
Study of Robust Distributed Beamforming Based on Cross-Correlation and Subspace Projection Techniques
In this work, we present a novel robust distributed beamforming (RDB)
approach to mitigate the effects of channel errors on wireless networks
equipped with relays based on the exploitation of the cross-correlation between
the received data from the relays at the destination and the system output. The
proposed RDB method, denoted cross-correlation and subspace projection (CCSP)
RDB, considers a total relay transmit power constraint in the system and the
objective of maximizing the output signal-to-interference-plus-noise ratio
(SINR). The relay nodes are equipped with an amplify-and-forward (AF) protocol
and we assume that the channel state information (CSI) is imperfectly known at
the relays and there is no direct link between the sources and the destination.
The CCSP does not require any costly optimization procedure and simulations
show an excellent performance as compared to previously reported algorithms.Comment: 3 figures, 7 pages. arXiv admin note: text overlap with
arXiv:1707.00953
Iterative Detection and Decoding Algorithms using LDPC Codes for MIMO Systems in Block-Fading Channels
We propose iterative detection and decoding (IDD) algorithms with Low-Density
Parity-Check (LDPC) codes for Multiple Input Multiple Output (MIMO) systems
operating in block-fading and fast Rayleigh fading channels. Soft-input
soft-output minimum mean-square error receivers with successive interference
cancellation are considered. In particular, we devise a novel strategy to
improve the bit error rate (BER) performance of IDD schemes, which takes into
account the soft \textit{a posteriori} output of the decoder in a block-fading
channel when Root-Check LDPC codes are used. A MIMO IDD receiver with soft
information processing that exploits the code structure and the behavior of the
log likelihood ratios is also developed. Moreover, we present a scheduling
algorithm for decoding LDPC codes in block-fading channels. Simulations show
that the proposed techniques result in significant gains in terms of BER for
both block-fading and fast-fading channels.Comment: 17 pages, 4 figures, IEEE Transactions on Vehicular Technology, 201
Study of Opportunistic Cooperation Techniques using Jamming and Relays for Physical-Layer Security in Buffer-aided Relay Networks
In this paper, we investigate opportunistic relay and jammer cooperation
schemes in multiple-input multiple-output (MIMO) buffer-aided relay networks.
The network consists of one source, an arbitrary number of relay nodes,
legitimate users and eavesdroppers, with the constraints of physical layer
security. We propose an algorithm to select a set of relay nodes to enhance the
legitimate users' transmission and another set of relay nodes to perform
jamming of the eavesdroppers. With Inter-Relay interference (IRI) taken into
account, interference cancellation can be implemented to assist the
transmission of the legitimate users. Secondly, IRI can also be used to further
increase the level of harm of the jamming signal to the eavesdroppers. By
exploiting the fact that the jamming signal can be stored at the relay nodes,
we also propose a hybrid algorithm to set a signal-to-interference and noise
ratio (SINR) threshold at the node to determine the type of signal stored at
the relay node. With this separation, the signals with high SINR are delivered
to the users as conventional relay systems and the low SINR performance signals
are stored as potential jamming signals. Simulation results show that the
proposed techniques obtain a significant improvement in secrecy rate over
previously reported algorithms.Comment: 8 pages, 3 figure
Flexible Widely-Linear Multi-Branch Decision Feedback Detection Algorithms for Massive MIMO Systems
This paper presents widely-linear multi-branch decision feedback detection
techniques for large-scale multiuser multiple-antenna systems. We consider a
scenario with impairments in the radio-frequency chain in which the in-phase
(I) and quadrature (Q) components exhibit an imbalance, which degrades the
receiver performance and originates non-circular signals. A widely-linear
multi-branch decision feedback receiver is developed to mitigate both the
multiuser interference and the I/Q imbalance effects. An iterative detection
and decoding scheme with the proposed receiver and convolutional codes is also
devised. Simulation results show that the proposed techniques outperform
existing algorithms.Comment: 3 figures, 9 pages. arXiv admin note: text overlap with
arXiv:1308.272
Study of Adaptive Activity-Aware Constellation List-Based Detection for Massive Machine-Type Communications
In this work, we propose an adaptive list-based decision feedback detector
along with an -norm regularized recursive least-squares algorithm that
only requires pilot symbols (AA-CL-DF). The proposed detector employs a list
strategy based on the signal constellation points to generate different
candidates for detection. Simulation results show that the proposed AA-CL-DF
successfully mitigates the error propagation and approaches the performance for
the oracle LMMSE algorithm.Comment: 7 pages, 7 figure