4,766 research outputs found
Performance analysis of an opportunistic relay selection protocol for multi-hop networks (Technical report)
In this technical report, we analyze the performance of an interference-aware
opportunistic relay selection protocol for multi-hop line networks which is
based on the following simple rule: a node always transmits if it has a packet,
except when its successive node on the line is transmitting. We derive
analytically the saturation throughput and the end-to-end delay for two and
three hop networks, and present simulation results for higher numbers of hops.
In the case of three hops, we determine the throughput-optimal relay positions.Comment: 4 pages, 5 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
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
Efficient and Reliable Topology Control based Opportunistic Routing Algorithm for WSNs
The opportunistic routing has advantages on improving the packet delivery
ratio between source node and candidate set (PDRsc). However, considering the
frequent topology variation in wireless sensor networks, how to improve and
control the PDR has not been investigated in detail. Therefore, in this paper,
we propose an efficient and reliable topology control based opportunistic
routing algorithm (ERTO) which takes PDRsc into account. In ERTO, the
interference and transmission power loss are taken into account during the
calculation of PDRsc. The PDRsc, the expected energy consumption, and the
relationship between transmission power and node degree are considered to
calculate the optimal transmission power and relay node degree jointly. For
improving the routing effective and reducing the calculation complexity, we
introduce the multi-objective optimization into the topology control. During
the routing process, nodes calculate the optimal transmission power and relay
node degree according to the properties of Pareto optimal solution set, by
which the optimal solutions can be selected. Based on these innovations, the
energy consumption, the transmission delay, and the throughout have been
improved greatly compared with the traditional power control based
opportunistic routing algorithms.Comment: 12 pages, 10 figures, 23 formula
Denial of Service Attack in Cooperative Networks
In Denial of Service (DoS) attack the network resources are either delayed or
refused to be assigned to the requested user [1]. This may occurs due to verity
of reasons, could be intentionally or unintentionally. The unintentional case
is quite hard to mitigate. In this paper we will refer the former case in
context of cooperative networks. In cooperative networks we relay the data via
intermediate nodes called relays. The relay selection is mechanism [2] need to
be devised with focus on mitigating such attacks. In this paper we will enhance
the relay selection mechanism address by [3] to propose the novel relay
selection with emphasis on security of Wireless Local Area Networks.Comment: Cooperative relaying and DoS attac
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
Relay-Pair Selection in Buffer-Aided Successive Opportunistic Relaying using a Multi-Antenna Source
We study a cooperative network with a buffer-aided multi-antenna source,
multiple half-duplex (HD) buffer-aided relays and a single destination. Such a
setup could represent a cellular downlink scenario, in which the source can be
a more powerful wireless device with a buffer and multiple antennas, while a
set of intermediate less powerful devices are used as relays to reach the
destination. The main target is to recover the multiplexing loss of the network
by having the source and a relay to simultaneously transmit their information
to another relay and the destination, respectively. Successive transmissions in
such a cooperative network, however, cause inter-relay interference (IRI).
First, by assuming global channel state information (CSI), we show that the
detrimental effect of IRI can be alleviated by precoding at the source,
mitigating or even fully cancelling the interference. A cooperative relaying
policy is proposed that employs a joint precoding design and relay-pair
selection. Note that both fixed rate and adaptive rate transmissions can be
considered. For the case when channel state information is only available at
the receiver side (CSIR), we propose a relay selection policy that employs a
phase alignment technique to reduce the IRI. The performance of the two
proposed relay pair selection policies are evaluated and compared with other
state-of-the-art relaying schemes in terms of outage and throughput. The
results show that the use of a powerful source can provide considerable
performance improvements.Comment: 32 pages, 7 figures, Ad Hoc Network
Low-Rate Machine-Type Communication via Wireless Device-to-Device (D2D) Links
Wireless cellular networks feature two emerging technological trends. The
first is the direct Device-to-Device (D2D) communications, which enables direct
links between the wireless devices that reutilize the cellular spectrum and
radio interface. The second is that of Machine-Type Communications (MTC), where
the objective is to attach a large number of low-rate low-power devices, termed
Machine-Type Devices (MTDs) to the cellular network. MTDs pose new challenges
to the cellular network, one if which is that the low transmission power can
lead to outage problems for the cell-edge devices. Another issue imminent to
MTC is the \emph{massive access} that can lead to overload of the radio
interface. In this paper we explore the opportunity opened by D2D links for
supporting MTDs, since it can be desirable to carry the MTC traffic not through
direct links to a Base Station, but through a nearby relay. MTC is modeled as a
fixed-rate traffic with an outage requirement. We propose two network-assisted
D2D schemes that enable the cooperation between MTDs and standard cellular
devices, thereby meeting the MTC outage requirements while maximizing the rate
of the broadband services for the other devices. The proposed schemes apply the
principles Opportunistic Interference Cancellation and the Cognitive Radio's
underlaying. We show through analysis and numerical results the gains of the
proposed schemes.Comment: 12 Pages, 9 Figures, Submitted to JSAC "Device-to-Device
Communications in Cellular Networks" on the 20th of May 201
Energy Efficiency of Opportunistic Device-to-Device Relaying Under Lognormal Shadowing
Energy consumption is a major limitation of low power and mobile devices.
Efficient transmission protocols are required to minimize an energy consumption
of the mobile devices for ubiquitous connectivity in the next generation
wireless networks. Opportunistic schemes select a single relay using the
criteria of the best channel and achieve a near-optimal diversity performance
in a cooperative wireless system. In this paper, we study the energy efficiency
of the opportunistic schemes for device-to-device communication. In the
opportunistic approach, an energy consumed by devices is minimized by selecting
a single neighboring device as a relay using the criteria of minimum consumed
energy in each transmission in the uplink of a wireless network. We derive
analytical bounds and scaling laws on the expected energy consumption when the
devices experience log-normal shadowing with respect to a base station
considering both the transmission as well as circuit energy consumptions. We
show that the protocol improves the energy efficiency of the network comparing
to the direct transmission even if only a few devices are considered for
relaying. We also demonstrate the effectiveness of the protocol by means of
simulations in realistic scenarios of the wireless network.Comment: 30 pages, 8 figure
On Green Energy Powered Cognitive Radio Networks
Green energy powered cognitive radio (CR) network is capable of liberating
the wireless access networks from spectral and energy constraints. The
limitation of the spectrum is alleviated by exploiting cognitive networking in
which wireless nodes sense and utilize the spare spectrum for data
communications, while dependence on the traditional unsustainable energy is
assuaged by adopting energy harvesting (EH) through which green energy can be
harnessed to power wireless networks. Green energy powered CR increases the
network availability and thus extends emerging network applications. Designing
green CR networks is challenging. It requires not only the optimization of
dynamic spectrum access but also the optimal utilization of green energy. This
paper surveys the energy efficient cognitive radio techniques and the
optimization of green energy powered wireless networks. Existing works on
energy aware spectrum sensing, management, and sharing are investigated in
detail. The state of the art of the energy efficient CR based wireless access
network is discussed in various aspects such as relay and cooperative radio and
small cells. Envisioning green energy as an important energy resource in the
future, network performance highly depends on the dynamics of the available
spectrum and green energy. As compared with the traditional energy source, the
arrival rate of green energy, which highly depends on the environment of the
energy harvesters, is rather random and intermittent. To optimize and adapt the
usage of green energy according to the opportunistic spectrum availability, we
discuss research challenges in designing cognitive radio networks which are
powered by energy harvesters
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