2,445 research outputs found
Study of Switched Max-Link Buffer-Aided Relay Selection for Cooperative MIMO Systems
In this paper, we investigate relay selection for cooperative
multiple-antenna systems that are equipped with buffers, which increase the
reliability of wireless links. In particular, we present a novel relay
selection technique based on switching and the Max-Link protocol that is named
Switched Max-Link. We also introduce a novel relay selection criterion based on
the maximum likelihood (ML) principle denoted maximum minimum distance that is
incorporated into. Simulations are then employed to evaluate the performance of
the proposed and existing techniques.Comment: 8 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1707.0095
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
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 Buffer-Aided Space-Time Coding for Multiple-Antenna Cooperative Wireless Networks
In this work we propose an adaptive buffer-aided space-time coding scheme for
cooperative wireless networks. A maximum likelihood receiver and adjustable
code vectors are considered subject to a power constraint with an
amplify-and-forward cooperation strategy. Each multiple-antenna relay is
equipped with a buffer and is capable of storing the received symbols before
forwarding them to the destination. We also present an adaptive relay selection
and optimization algorithm, in which the instantaneous signal to noise ratio in
each link is calculated and compared at the destination. An adjustable code
vector obtained by a feedback channel at each relay is employed to form a
space-time coded vector which achieves a higher coding gain than standard
schemes. A stochastic gradient algorithm is developed to compute the parameters
of the adjustable code vector with reduced computational complexity. Simulation
results show that the proposed buffer-aided scheme and algorithm obtain
performance gains over existing schemes.Comment: 7 pages, 2 figure
Energy Efficiency Optimization for MIMO Broadcast Channels
Characterizing the fundamental energy efficiency (EE) limits of MIMO
broadcast channels (BC) is significant for the development of green wireless
communications. We address the EE optimization problem for MIMO-BC in this
paper and consider a practical power model, i.e., taking into account a
transmit independent power which is related to the number of active transmit
antennas. Under this setup, we propose a new optimization approach, in which
the transmit covariance is optimized under fixed active transmit antenna sets,
and then active transmit antenna selection (ATAS) is utilized. During the
transmit covariance optimization, we propose a globally optimal energy
efficient iterative water-filling scheme through solving a series of concave
fractional programs based on the block-coordinate ascent algorithm. After that,
ATAS is employed to determine the active transmit antenna set. Since activating
more transmit antennas can achieve higher sum-rate but at the cost of larger
transmit independent power consumption, there exists a tradeoff between the
sum-rate gain and the power consumption. Here ATAS can exploit the best
tradeoff and thus further improve the EE. Optimal exhaustive search and
low-complexity norm based ATAS schemes are developed. Through simulations, we
discuss the effect of different parameters on the EE of the MIMO-BC.Comment: submitted for possible publication, 26 pages, 10 figure
Resource Allocation and Interference Mitigation Techniques for Cooperative Multi-Antenna and Spread Spectrum Wireless Networks
This chapter presents joint interference suppression and power allocation
algorithms for DS-CDMA and MIMO networks with multiple hops and
amplify-and-forward and decode-and-forward (DF) protocols. A scheme for joint
allocation of power levels across the relays and linear interference
suppression is proposed. We also consider another strategy for joint
interference suppression and relay selection that maximizes the diversity
available in the system. Simulations show that the proposed cross-layer
optimization algorithms obtain significant gains in capacity and performance
over existing schemes.Comment: 10 figures. arXiv admin note: substantial text overlap with
arXiv:1301.009
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
Study of Relay Selection for Physical-Layer Security in Buffer-Aided Relay Networks Based on the Secrecy Rate Criterion
In this paper, we investigate an opportunistic relay and jammer scheme along
with relay selection algorithms based on the secrecy rate criterion in
multiple-input multiple-output buffer-aided down link relay networks, which
consist of one source, a number of relay nodes, legitimate users and
eavesdroppers, with the constraints of physical layer security. The
opportunistic relay and jammer scheme is employed to improve the transmission
rate and different relay selection policies are performed to achieve better
secrecy rate with the consideration of eavesdroppers. Among all the
investigated relay selection policies, a relay selection policy which is
developed to maximize the secrecy rate based on exhaustive searches outperforms
other relay selection policies in terms of secrecy rate. Based on the secrecy
rate criterion, we develop a relay selection algorithm without knowledge of the
channels of the eavesdroppers. We also devise a greedy search algorithm based
on the secrecy rate criterion to reduce the computational complexity of the
exhaustive search technique. Simulations show the superiority of the secrecy
rate criterion over competing approaches.Comment: 6 pages, 3 figure
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
Dual-Function MIMO Radar Communications System Design Via Sparse Array Optimization
Spectrum congestion and competition over frequency bandwidth could be
alleviated by deploying dual-function radar-communications systems, where the
radar platform presents itself as a system of opportunity to secondary
communication functions. In this paper, we propose a new technique for
communication information embedding into the emission of multiple-input
multiple-output (MIMO) radar using sparse antenna array configurations. The
phases induced by antenna displacements in a sensor array are unique, which
makes array configuration feasible for symbol embedding. We also exploit the
fact that in a MIMO radar system, the association of independent waveforms with
the transmit antennas can change over different pulse repetition periods
without impacting the radar functionality. We show that by reconfiguring sparse
transmit array through antenna selection and reordering waveform-antenna
paring, a data rate of megabits per second can be achieved for a moderate
number of transmit antennas. To counteract practical implementation issues, we
propose a regularized antenna selection based signaling scheme. The possible
data rate is analyzed and the symbol/bit error rates are derived. Simulation
examples are provided for performance evaluations and to demonstrate the
effectiveness of proposed DFRC techniques
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