2,082 research outputs found
Study of Switched Max-Link Relay Selection for Cooperative Multiple-Antenna Systems
In this work, we present a switched relaying framework for multiple-input
multiple-output (MIMO) relay systems where a source node may transmit directly
to a destination node or aided by relays. We also investigate relay selection
techniques for the proposed switched relaying framework, whose relays are
equipped with buffers. In particular, we develop a novel relay selection
protocol based on switching and the selection of the best link, denoted as
Switched Max-Link. We then propose the Maximum Minimum Distance (MMD) relay
selection criterion for MIMO systems, which is based on the optimal Maximum
Likelihood (ML) principle and can provide significant performance gains over
other criteria, along with algorithms that are incorporated into the proposed
Switched Max-Link protocol. An analysis of the proposed Switched Max-Link
protocol and the MMD relay selection criterion in terms of computational cost,
pairwise error probability, sum-rate and average delay is carried out.
Simulations show that Switched Max-Link using the MMD criterion outperforms
previous works in terms of sum-rate, pairwise error probability, average delay
and bit error rate.Comment: 15 pages, 13 figure
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
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
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
Higher Order Statistics in Switched Diversity Systems
We analyze the level crossing rate (LCR) and the average fade duration of the
output signal-to-noise-ratio (SNR) in generalized switched diversity systems.
By using a common approach, we study these higher order statistics for two
different kinds of configurations: (1) Colocated diversity, i.e. receiver
equipped with multiple antennas, and (2) Distributed diversity, i.e. relaying
link with multiple single-antenna threshold-based decode-and-forward (DF)
relays. In both cases, we consider the switched diversity combining strategies
Selection Combining and Switch \& Stay Combining (SSC). Whenever using
threshold-based techniques such as DF or SSC, the output SNR is a discontinuous
random process and hence classic Rice approach to calculate the LCR is not
applicable. Thus, we use an alternative formulation in terms of the one and
two-dimensional cumulative distribution functions of the output SNR. Our
results are general, and hold for any arbitrary distribution of fading at the
different diversity branches. Moreover, we develop a general asymptotic
framework to calculate these higher order statistics in high mean SNR
environments which only needs of the univariate probability density function
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
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
Adaptive Full-Duplex Jamming Receiver for Secure D2D Links in Random Networks
Device-to-device (D2D) communication raises new transmission secrecy
protection challenges, since conventional physical layer security approaches,
such as multiple antennas and cooperation techniques, are invalid due to its
resource/size constraints. The full-duplex (FD) jamming receiver, which
radiates jamming signals to confuse eavesdroppers when receiving the desired
signal simultaneously, is a promising candidate. Unlike existing endeavors that
assume the FD jamming receiver always improves the secrecy performance compared
with the half-duplex (HD) receiver, we show that this assumption highly depends
on the instantaneous residual self-interference cancellation level and may be
invalid. We propose an adaptive jamming receiver operating in a switched FD/HD
mode for a D2D link in random networks. Subject to the secrecy outage
probability constraint, we optimize the transceiver parameters, such as
signal/jamming powers, secrecy rates and mode switch criteria, to maximize the
secrecy throughput. Most of the optimization operations are taken off-line and
only very limited on-line calculations are required to make the scheme with low
complexity. Furthermore, some interesting insights are provided, such as the
secrecy throughput is a quasi-concave function. Numerical results are
demonstrated to verify our theoretical findings, and to show its superiority
compared with the receiver operating in the FD or HD mode only
Study of Interference Cancellation and Relay Selection Algorithms Using Greedy Techniques for Cooperative DS-CDMA Systems
In this work, we study interference cancellation techniques and a multi-relay
selection algorithm based on greedy methods for the uplink of cooperative
direct-sequence code-division multiple access (DS-CDMA) systems. We first
devise low-cost list-based successive interference cancellation (GL-SIC) and
parallel interference cancellation (GL-PIC) algorithms with RAKE receivers as
the front-end that can approach the maximum likelihood detector performance and
be used at both the relays and the destination of cooperative systems. Unlike
prior art, the proposed GL-SIC and GL-PIC algorithms exploit the Euclidean
distance between users of interest and the potential nearest constellation
point with a chosen threshold in order to build an effective list of detection
candidates. A low-complexity multi-relay selection algorithm based on greedy
techniques that can approach the performance of an exhaustive search is also
proposed. A cross-layer design strategy that brings together the proposed
multiuser detection algorithms and the greedy relay selection is then developed
along with an analysis of the proposed techniques. Simulations show an
excellent bit error rate performance of the proposed detection and relay
selection algorithms as compared to existing techniques.Comment: 6 figures in Eurasip Journal on Wireless Communications and
Networking, 2016. arXiv admin note: text overlap with arXiv:1410.0444,
arXiv:1406.023
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
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