773 research outputs found
Joint SIC and Relay Selection for Cooperative DS-CDMA Systems
In this work, we propose a cross-layer design strategy based on a joint
successive interference cancellation (SIC) detection technique and a
multi-relay selection algorithm for the uplink of cooperative direct-sequence
code-division multiple access (DS-CDMA) systems. We devise a low-cost greedy
list-based SIC (GL-SIC) strategy with RAKE receivers as the front-end that can
approach the maximum likelihood detector performance. %Unlike prior art, the
proposed GL-SIC algorithm %exploits the Euclidean distance between users of
interest, multiple %ordering and their constellation points to build an
effective list %of detection candidates. We also present a low-complexity
multi-relay selection algorithm based on greedy techniques that can approach
the performance of an exhaustive search. %A cross-layer %design strategy that
brings together the proposed GL-SIC algorithm %and the greedy relay selection
is then developed. Simulations show an excellent bit error rate performance of
the proposed detection and relay selection algorithms as compared to existing
techniques.Comment: 5 figures, conferenc
Power Control and Performance Analysis of Outage-Limited Cellular Network with MUD-SIC and Macro-Diversity
In this paper, we analyze the uplink goodput (bits/sec/Hz successfully
decoded) and per-user packet outage in a cellular network using multi-user
detection with successive interference cancellation (MUD-SIC). We consider
non-ergodic fading channels where microscopic fading channel information is not
available at the transmitters. As a result, packet outage occurs whenever the
data rate of packet transmissions exceeds the instantaneous mutual information
even if powerful channel coding is applied for protection. We are interested to
study the role of macro-diversity (MDiv) between multiple base stations on the
MUD-SIC performance where the effect of potential error-propagation during the
SIC processing is taken into account. While the jointly optimal power and
decoding order in the MUD-SIC are NP hard problem, we derive a simple on/off
power control and asymptotically optimal decoding order with respect to the
transmit power. Based on the information theoretical framework, we derive the
closed-form expressions on the total system goodput as well as the per-user
packet outage probability. We show that the system goodput does not scale with
SNR due to mutual interference in the SIC process and macro-diversity (MDiv)
could alleviate the problem and benefit to the system goodput
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
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
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 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
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
Joint PIC and relay selection based on greedy techniques for cooperative DS-CDMA systems
In this work, we propose a cross-layer design strategy based on the parallel
interference cancellation (PIC) detection technique and a multi-relay selection
algorithm for the uplink of cooperative direct-sequence code-division multiple
access (DS-CDMA) systems. We devise a low-cost greedy list-based PIC (GL-PIC)
strategy with RAKE receivers as the front-end that can approach the maximum
likelihood detector performance. We also present a low-complexity multi-relay
selection algorithm based on greedy techniques that can approach the
performance of an exhaustive search. Simulations show an excellent bit error
rate performance of the proposed detection and relay selection algorithms as
compared to existing techniques.Comment: 5 figures, 2 tables, 5 page
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
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
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