2,439 research outputs found
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 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
Effective Capacity in Wireless Networks: A Comprehensive Survey
Low latency applications, such as multimedia communications, autonomous
vehicles, and Tactile Internet are the emerging applications for
next-generation wireless networks, such as 5th generation (5G) mobile networks.
Existing physical-layer channel models, however, do not explicitly consider
quality-of-service (QoS) aware related parameters under specific delay
constraints. To investigate the performance of low-latency applications in
future networks, a new mathematical framework is needed. Effective capacity
(EC), which is a link-layer channel model with QoS-awareness, can be used to
investigate the performance of wireless networks under certain statistical
delay constraints. In this paper, we provide a comprehensive survey on existing
works, that use the EC model in various wireless networks. We summarize the
work related to EC for different networks such as cognitive radio networks
(CRNs), cellular networks, relay networks, adhoc networks, and mesh networks.
We explore five case studies encompassing EC operation with different design
and architectural requirements. We survey various delay-sensitive applications
such as voice and video with their EC analysis under certain delay constraints.
We finally present the future research directions with open issues covering EC
maximization
A Buffer-aided Successive Opportunistic Relay Selection Scheme with Power Adaptation and Inter-Relay Interference Cancellation for Cooperative Diversity Systems
In this paper we consider a simple cooperative network consisting of a
source, a destination and a cluster of decode-and-forward half-duplex relays.
At each time-slot, the source and (possibly) one of the relays transmit a
packet to another relay and the destination, respectively, resulting in
inter-relay interference (IRI). In this work, with the aid of buffers at the
relays, we mitigate the detrimental effect of IRI through interference
cancellation. More specifically, we propose the min-power scheme that minimizes
the total energy expenditure per time slot under an IRI cancellation scheme.
Apart from minimizing the energy expenditure, the min-power selection scheme,
also provides better throughput and lower outage probability than existing
works in the literature. It is the first time that interference cancellation is
combined with buffer-aided relays and power adaptation to mitigate the IRI and
minimize the energy expenditure. The new relay selection policy is analyzed in
terms of outage probability and diversity, by modeling the evolution of the
relay buffers as a Markov Chain (MC). We construct the state transition matrix
of the MC, and hence obtain the steady state with which we can characterize the
outage probability. The proposed scheme outperforms relevant state-of-the-art
relay selection schemes in terms of throughput, diversity and energy
efficiency, as demonstrated via examples.Comment: Preliminary results of this article have been presented in the IEEE
International Symposium on Personal Indoor and Mobile Radio Communications,
8-11 September, 2013, London, United Kingdo
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
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
Virtual Full-Duplex Buffer-Aided Relaying in the Presence of Inter-Relay Interference
In this paper, we study virtual full-duplex (FD) buffer-aided relaying to
recover the loss of multiplexing gain caused by half-duplex (HD) relaying in a
multiple relay network, where each relay is equipped with a buffer and multiple
antennas, through joint opportunistic relay selection (RS) and beamforming (BF)
design. The main idea of virtual FD buffer-aided relaying is that the source
and one of the relays simultaneously transmit their own information to another
relay and the destination, respectively. In such networks, inter-relay
interference (IRI) is a crucial problem which has to be resolved like
self-interference in the FD relaying. In contrast to previous work that
neglected IRI, we propose joint RS and BF schemes taking IRI into consideration
by using multiple antennas at the relays. In order to maximize average
end-to-end rate, we propose a weighted sum-rate maximization strategy assuming
that adaptive rate transmission is employed in both the source to relay and
relay to destination links. Then, we propose several BF schemes cancelling or
suppressing IRI in order to maximize the weighted sum-rate. Numerical results
show that our proposed optimal, zero forcing, and minimum mean square error
BF-based RS schemes asymptotically approach the ideal FD relaying upper bound
when increasing the number of antennas and/or the number of relays.Comment: Accepted for publication to IEEE Transactions on Wireless
Communication
Cooperative Wireless Backhauling
We consider wireless backhauling for a scenario where two small-cell base
stations (SC-BSs) employ the same time and frequency resources for offloading
their data to a common macro-cell base station (MC-BS). The two SC-BSs allocate
a part of the shared resource to exchange data in order to be able to cooperate
to boost the backhaul capacity. For this scenario, we develop the optimal
transmission strategy which, based on the channel state information, determines
whether the SC-BSs should exchange data and cooperate or transmit their data
independently to the MC-BS. Our numerical results demonstrate the superiority
of the proposed cooperative~wireless backhauling protocol compared to existing
protocols in the literature
Localisation, Communication and Networking with VLC: Challenges and Opportunities
The forthcoming Fifth Generation (5G) era raises the expectation for
ubiquitous wireless connectivity to enhance human experiences in information
and knowledge sharing as well as in entertainment and social interactions. The
promising Visible Light Communications (VLC) lies in the intersection field of
optical and wireless communications, where substantial amount of new knowledge
has been generated by multi-faceted investigations ranging from the
understanding of optical communications and signal processing techniques to the
development of disruptive networking solutions and to the exploitation of joint
localisation and communications. Building on these new understandings and
exciting developments, this paper provides an overview on the three
inter-linked research strands of VLC, namely localisation, communications and
networking. Advanced recent research activities are comprehensively reviewed
and intriguing future research directions are actively discussed, along with
the identifications of a range of challenges, both for enhancing the
established applications and for stimulating the emerging applications
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
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