34 research outputs found
Intercept Probability Analysis of Cooperative Wireless Networks with Best Relay Selection in the Presence of Eavesdropping Attack
Due to the broadcast nature of wireless medium, wireless communication is
extremely vulnerable to eavesdropping attack. Physical-layer security is
emerging as a new paradigm to prevent the eavesdropper from interception by
exploiting the physical characteristics of wireless channels, which has
recently attracted a lot of research attentions. In this paper, we consider the
physical-layer security in cooperative wireless networks with multiple
decode-and-forward (DF) relays and investigate the best relay selection in the
presence of eavesdropping attack. For the comparison purpose, we also examine
the conventional direct transmission without relay and traditional max-min
relay selection. We derive closed-form intercept probability expressions of the
direct transmission, traditional max-min relay selection, and proposed best
relay selection schemes in Rayleigh fading channels. Numerical results show
that the proposed best relay selection scheme strictly outperforms the
traditional direct transmission and max-min relay selection schemes in terms of
intercept probability. In addition, as the number of relays increases, the
intercept probabilities of both traditional max-min relay selection and
proposed best relay selection schemes decrease significantly, showing the
advantage of exploiting multiple relays against eavesdropping attack.Comment: 5 pages. arXiv admin note: substantial text overlap with
arXiv:1305.081
Energy Efficiency of Network Cooperation for Cellular Uplink Transmissions
There is a growing interest in energy efficient or so-called "green" wireless
communication to reduce the energy consumption in cellular networks. Since
today's wireless terminals are typically equipped with multiple network access
interfaces such as Bluetooth, Wi-Fi, and cellular networks, this paper
investigates user terminals cooperating with each other in transmitting their
data packets to a base station (BS) by exploiting the multiple network access
interfaces, referred to as inter-network cooperation, to improve the energy
efficiency in cellular uplink transmission. Given target outage probability and
data rate requirements, we develop a closed-form expression of energy
efficiency in Bits-per-Joule for the inter-network cooperation by taking into
account the path loss, fading, and thermal noise effects. Numerical results
show that when the cooperating users move towards to each other, the proposed
inter-network cooperation significantly improves the energy efficiency as
compared with the traditional non-cooperation and intra-network cooperation.
This implies that given a certain amount of bits to be transmitted, the
inter-network cooperation requires less energy than the traditional
non-cooperation and intra-network cooperation, showing the energy saving
benefit of inter-network cooperation.Comment: in Proceedings of the 2013 IEEE International Conference on
Communications (IEEE ICC 2013), Budapest, Hungary, June 201
Optimal Relay Selection with Non-negligible Probing Time
In this paper an optimal relay selection algorithm with non-negligible
probing time is proposed and analyzed for cooperative wireless networks. Relay
selection has been introduced to solve the degraded bandwidth efficiency
problem in cooperative communication. Yet complete information of relay
channels often remain unavailable for complex networks which renders the
optimal selection strategies impossible for transmission source without probing
the relay channels. Particularly when the number of relay candidate is large,
even though probing all relay channels guarantees the finding of the best
relays at any time instant, the degradation of bandwidth efficiency due to
non-negligible probing times, which was often neglected in past literature, is
also significant. In this work, a stopping rule based relay selection strategy
is determined for the source node to decide when to stop the probing process
and choose one of the probed relays to cooperate with under wireless channels'
stochastic uncertainties. This relay selection strategy is further shown to
have a simple threshold structure. At the meantime, full diversity order and
high bandwidth efficiency can be achieved simultaneously. Both analytical and
simulation results are provided to verify the claims.Comment: 8 pages. ICC 201
Interference-Assisted Wireless Energy Harvesting in Cognitive Relay Network with Multiple Primary Transceivers
We consider a spectrum sharing scenario, where a secondary network coexists
with a primary network of multiple transceivers. The secondary network consists
of an energy-constrained decode-and-forward secondary relay which assists the
communication between a secondary transmitter and a destination in the presence
of the interference from multiple primary transmitters. The secondary relay
harvests energy from the received radio-frequency signals, which include the
information signal from the secondary transmitter and the primary interference.
The harvested energy is then used to decode the secondary information and
forward it to the secondary destination. At the relay, we adopt a time
switching policy due to its simplicity that switches between the energy
harvesting and information decoding over time. Specifically, we derive a
closed-form expression for the secondary outage probability under the primary
outage constraint and the peak power constraint at both secondary transmitter
and relay. In addition, we investigate the effect of the number of primary
transceivers on the optimal energy harvesting duration that minimizes the
secondary outage probability. By utilizing the primary interference as a useful
energy source in the energy harvesting phase, the secondary network achieves a
better outage performance.Comment: 6 pages, 5 figures, To be presented at IEEE GLOBECOM 201
Outage Analysis of Multi-Relay Selection for Cognitive Radio with Imperfect Spectrum Sensing
In this paper, we examine the outage performance of a cognitive relay
network, which is comprised of a secondary transmitter (ST), multiple
decode-and-forward (DF) relays and a secondary destination (SD). We propose a
multi-relay selection scheme for the cognitive relay network, where multiple
relays are selected and used to participate in forwarding the secondary
transmission from ST to SD. A closed-form expression of the outage probability
for the proposed multi-relay selection under imperfect spectrum sensing is
derived in Rayleigh fading environments. For comparison purposes, the
conventional direct transmission and the best-relay selection are also
considered as benchmarks. Numerical results show that as the spectrum sensing
performance improves with an increasing detection probability and/or a
decreasing false alarm probability, the outage probabilities of the proposed
multi-relay selection as well as the direct transmission and the best-relay
selection schemes all decrease accordingly. It is also demonstrated that the
proposed multi-relay selection significantly outperforms the conventional
approaches in terms of the outage probability.Comment: 5 page
Opportunistic Adaptive Relaying in Cognitive Radio Networks
Combining cognitive radio technology with user cooperation could be
advantageous to both primary and secondary transmissions. In this paper, we
propose a first relaying scheme for cognitive radio networks (called "Adaptive
relaying scheme 1"), where one relay node can assist the primary or the
secondary transmission with the objective of improving the outage probability
of the secondary transmission with respect to a primary outage probability
threshold. Upper bound expressions of the secondary outage probability using
the proposed scheme are derived over Rayleigh fading channels. Numerical and
simulation results show that the secondary outage probability using the
proposed scheme is lower than that of other relaying schemes. Then, we extend
the proposed scheme to the case where the relay node has the ability to decode
both the primary and secondary signals and also can assist simultaneously both
transmissions. Simulations show the performance improvement that can be
obtained due to this extension in terms of secondary outage probability.Comment: 5 pages, 4 figures. Accepted for publication in Proc. IEEE
International Communications Conference (ICC), Ottawa (ON), Canada, June 201
Sensing and Sharing Schemes for Spectral Efficiency of Cognitive Radios
Increase in data traffic, number of users and their requirements laid to a necessity of more bandwidth. Cognitive radio is one of the emerging technology which addresses the spectrum scarcity issue. In this work we study the advantage of having collaboration between cognitive enabled small cell network and primary macrocell. Different from the existing works at spectrum sensing stage we are applying enhanced spectrum sensing to avoid probability of false alarms and missed detections which has impact on spectral efficiency. Later power control optimization for secondary users known as Hybrid spectrum sharing is used for further improvement of spectral efficiency. Furthermore, the failed packets of Primary users are taken care by high ranked relays which in turn decreases the average Primary user packet delay by 20% when compared between assisted Secondary user method and non-assisted Secondary user method.
Security versus Reliability Analysis of Opportunistic Relaying
Physical-layer security is emerging as a promising paradigm of securing
wireless communications against eavesdropping between legitimate users, when
the main link spanning from source to destination has better propagation
conditions than the wiretap link from source to eavesdropper. In this paper, we
identify and analyze the tradeoffs between the security and reliability of
wireless communications in the presence of eavesdropping attacks. Typically,
the reliability of the main link can be improved by increasing the source's
transmit power (or decreasing its date rate) to reduce the outage probability,
which unfortunately increases the risk that an eavesdropper succeeds in
intercepting the source message through the wiretap link, since the outage
probability of the wiretap link also decreases when a higher transmit power (or
lower date rate) is used. We characterize the security-reliability tradeoffs
(SRT) of conventional direct transmission from source to destination in the
presence of an eavesdropper, where the security and reliability are quantified
in terms of the intercept probability by an eavesdropper and the outage
probability experienced at the destination, respectively. In order to improve
the SRT, we then propose opportunistic relay selection (ORS) and quantify the
attainable SRT improvement upon increasing the number of relays. It is shown
that given the maximum tolerable intercept probability, the outage probability
of our ORS scheme approaches zero for , where is the number
of relays. Conversely, given the maximum tolerable outage probability, the
intercept probability of our ORS scheme tends to zero for .Comment: 9 pages. IEEE Transactions on Vehicular Technology, 201