64 research outputs found
Enhancing Physical Layer Security in AF Relay Assisted Multi-Carrier Wireless Transmission
In this paper, we study the physical layer security (PLS) problem in the dual
hop orthogonal frequency division multiplexing (OFDM) based wireless
communication system. First, we consider a single user single relay system and
study a joint power optimization problem at the source and relay subject to
individual power constraint at the two nodes. The aim is to maximize the end to
end secrecy rate with optimal power allocation over different sub-carriers.
Later, we consider a more general multi-user multi-relay scenario. Under high
SNR approximation for end to end secrecy rate, an optimization problem is
formulated to jointly optimize power allocation at the BS, the relay selection,
sub-carrier assignment to users and the power loading at each of the relaying
node. The target is to maximize the overall security of the system subject to
independent power budget limits at each transmitting node and the OFDMA based
exclusive sub-carrier allocation constraints. A joint optimization solution is
obtained through duality theory. Dual decomposition allows to exploit convex
optimization techniques to find the power loading at the source and relay
nodes. Further, an optimization for power loading at relaying nodes along with
relay selection and sub carrier assignment for the fixed power allocation at
the BS is also studied. Lastly, a sub-optimal scheme that explores joint power
allocation at all transmitting nodes for the fixed subcarrier allocation and
relay assignment is investigated. Finally, simulation results are presented to
validate the performance of the proposed schemes.Comment: 10 pages, 7 figures, accepted in Transactions on Emerging
Telecommunications Technologies (ETT), formerly known as European
Transactions on Telecommunications (ETT
Channel Impulse Response-based Distributed Physical Layer Authentication
In this preliminary work, we study the problem of {\it distributed}
authentication in wireless networks. Specifically, we consider a system where
multiple Bob (sensor) nodes listen to a channel and report their {\it
correlated} measurements to a Fusion Center (FC) which makes the ultimate
authentication decision. For the feature-based authentication at the FC,
channel impulse response has been utilized as the device fingerprint.
Additionally, the {\it correlated} measurements by the Bob nodes allow us to
invoke Compressed sensing to significantly reduce the reporting overhead to the
FC. Numerical results show that: i) the detection performance of the FC is
superior to that of a single Bob-node, ii) compressed sensing leads to at least
overhead reduction on the reporting channel at the expense of a small
( dB) SNR margin to achieve the same detection performance.Comment: 6 pages, 5 figures, accepted for presentation at IEEE VTC 2017 Sprin
Impact of workplace safety on employee retention using sequential mediation: evidence from the health-care sector
Purpose
This study aims to examine the impact of workplace safety (WPS) on employee retention (ER) in the health-care sector in Azad Jammu and Kashmir (AJ&K), Pakistan. At the same time, a mediation relationship through job satisfaction (JS) and employee loyalty (EL) was also tested.
Design/methodology/approach
Structured questionnaires were used to collect the data from 300 doctors, using purposive sampling technique analysed using partial least squares (Smart-PLS 3).
Findings
This study’s findings supported all hypotheses, such as WPS has a significant positive relationship with ER. In addition, a mediation relationship between JS and EL was also confirmed. Furthermore, a serial mediation effect of JS and EL between WPS and ER was also confirmed in this study.
Research limitations/implications
This study might not fit organisations from other regions due to regional norms. In the future, this study’s model may be tested on other regions and segments of the health-care sector, such as nurses, management staff and support staff.
Practical implications
The present study is unique because it is based on a newly formulated framework, WPS → JS → EL → ER, under the social exchange theory, which has not been tested before.
Social implications
In a safe environment, doctors will feel relaxed, stay longer and provide better services; resultantly, patients will get better treatment.
Originality/value
This study tested the sequential mediation effect through JS and EL for the first time in ER, which was missing previously, to the best of the authors’ knowledge. This will add more insights to the safety-retention literature in health-care settings. Furthermore, this study is also the first attempt to explore the relationship between WPS and ER in the health-care sector in AJ&K
Countering Active Attacks on RAFT-based IoT Blockchain Networks
This paper considers an Internet of Thing (IoT) blockchain network consisting
of a leader node and various follower nodes which together implement the RAFT
consensus protocol to verify a blockchain transaction, as requested by a
blockchain client. Further, two kinds of active attacks, i.e., jamming and
impersonation, are considered on the IoT blockchain network due to the presence
of multiple {\it active} malicious nodes in the close vicinity. When the IoT
network is under the jamming attack, we utilize the stochastic geometry tool to
derive the closed-form expressions for the coverage probabilities for both
uplink and downlink IoT transmissions. On the other hand, when the IoT network
is under the impersonation attack, we propose a novel method that enables a
receive IoT node to exploit the pathloss of a transmit IoT node as its
fingerprint to implement a binary hypothesis test for transmit node
identification. To this end, we also provide the closed-form expressions for
the probabilities of false alarm, missed detection and miss-classification.
Finally, we present detailed simulation results that indicate the following: i)
the coverage probability improves as the jammers' locations move away from the
IoT network, ii) the three error probabilities decrease as a function of the
link quality
On the Downlink Coverage Performance of RIS-Assisted THz Networks
This letter provides a stochastic geometry (SG)-based coverage probability
(CP) analysis of an indoor terahertz (THz) downlink assisted by a single
reconfigurable intelligent surface (RIS) panel. Specifically, multiple access
points (AP) deployed on the ceiling of a hall (each equipped with multiple
antennas) need to serve multiple user equipment (UE) nodes. Due to presence of
blockages, a typical UE may either get served via a direct link, the RIS, or
both links (the composite link). The locations of the APs and blockages are
modelled as a Poisson point process (PPP) and SG framework is utilized to
compute the CP, at a reference UE for all the three scenarios. Monte-Carlo
simulation results validate our theoretical analysis.Comment: Extended Arxiv version of submitted paper to IEEE Communications
Letter
Channel Impulse Response-based Physical Layer Authentication in a Diffusion-based Molecular Communication System
Consider impersonation attack by an active malicious nano node (Eve) on a diffusion based molecular communication (DbMC) system-Eve transmits during the idle slots to deceive the nano receiver (Bob) that she is indeed the legitimate nano transmitter (Alice). To this end, this work exploits the 3-dimensional (3D) channel impulse response (CIR) with L taps as device fingerprint for authentication of the nano transmitter during each slot. Specifically, Bob utilizes the Alice's CIR as ground truth to construct a binary hypothesis test to systematically accept/reject the data received in each slot. Simulation results highlight the great challenge posed by impersonation attack-i.e., it is not possible to simultaneously minimize the two error probabilities. In other words, one needs to tolerate on one error type in order to minimize the other error type
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