Chinmoy Kundu

Secrecy Outage of Dual-Hop AF Relay System With Relay Selection Without Eavesdropper's CSI

We evaluate the upper bound, lower bound and an approximate expression for secrecy outage probability of a dual hop Amplify-and-forward (AF) relay system when the single cooperating relay among the relays is selected without the knowledge of eavesdroppers instantaneous channel state information (CSI). This situation arises when eavesdropper is not a legitimate node, or being a trusted node, it acts maliciously and does not share its instantaneous CSI. We also obtain the tighter bounds in high signal-to-noise ratio (SNR) of the source to relay links and in high SNR of the relay to destination links. We show that when the SNR of the source to relay links tends to zero, it becomes the bottle neck for secure communication, and the secrecy outage tends to 1. We show that the approximate expression follows the simulated outage closely and the outage decreases with an increase in the number of relays and increases with an increase in the required secrecy rate.

Physical Layer Security in Cooperative Energy Harvesting Networks With a Friendly Jammer

In this letter, we consider a cooperative wireless network consisting of a source, multiple intermediate energy harvesting nodes, and a destination, in the presence of a passive eavesdropper. First, the intermediate nodes use the time switching-based relaying protocol to harvest energy from the source signal. Then, a pair out of intermediate nodes are selected as a relay and a jammer to transmit confidential and jamming signals to the destination and eavesdropper. Under these assumptions, we evaluate the system performance in terms of secrecy outage probability.

Secure Full-Duplex Small-Cell Networks in a Spectrum Sharing Environment

In this paper, we propose three relay selection schemes for full-duplex heterogeneous networks in the presence of multiple cognitive radio eavesdroppers. In this setup, the cognitive small-cell nodes (secondary network) can share the spectrum licensed to the macro-cell system (primary network) on the condition that the quality-of-service of the primary network is always satisfied subjected to its outage probability constraint. The messages are delivered from one small-cell base station to the destination with the help of full-duplex small-cell base stations, which act as relay nodes. Based on the availability of the networks channel state information at the secondary information source, three different selection criteria for full-duplex relays, namely: 1) partial relay selection; 2) optimal relay selection; and 3) minimal self-interference relay selection, are proposed. We derive the exact closed-form and asymptotic expressions of the secrecy outage probability for the three criteria under the attack of non-colluding/colluding eavesdroppers. We demonstrate that the optimal relay selection scheme outperforms the partial relay selection and minimal self-interference relay selection schemes at the expense of acquiring full channel state information knowledge. In addition, increasing the number of the full-duplex small-cell base stations can improve the security performance. At the illegitimate side, deploying colluding eavesdroppers and increasing the number of eavesdroppers put the confidential information at a greater risk. Besides, the transmit power and the desire outage probability of the primary network have great influences on the secrecy outage probability of the secondary network.

Secrecy performance of dual-hop decode-and-forward relay system with diversity combining at the eavesdropper

We have considered a dual-hop wireless network consisting of a decode-and-forward (DF) relay in presence of an eavesdropper. Relay can correctly decode and retransmit only if the received signal-to-noise ratio (SNR) meets a particular threshold. The eavesdropper can tap signals both from the relay and the source. The performance of the maximal ratio combining (MRC) and selection combining (SC) diversity at the eavesdropper is investigated. Whether knowledge of channel state information (CSI) at the transmitter is available or not is considered for the performance evaluation in secrecy outage probability and ergodic secrecy rate. Asymptotic analyses of performances are provided. We show that direct link has a significant impact on system secrecy. It is found that secrecy performances are the best if the relay is always able to decode correctly. We also found that knowledge of CSI helps to achieve better secrecy at lower rate. It is observed that unbalance created due to constraint on either of the source-relay link average SNR or relay-destination link average SNR does not yield similar secrecy outage performance but both can limit the secrecy outage performance. On the contrary, it is found that only source-relay link quality can limit the ergodic secrecy rate performance.

Secrecy Outage of Dual-Hop Amplify-and-Forward System and Its Application to Relay Selection

We evaluate the bounds on the secrecy outage probability of a dual hop Amplify-and-forward (AF) system with an eavesdropper tapping the second hop, when all the links undergo Rayleigh fading. An approximate expression of outage is also obtained when the signal-to-noise ratio of the first hop is high. Based on the developed outage expressions we evaluate the bounds and the approximate outage for optimal relay selection when full instantaneous channel state information (FCSI) i.e. of all the links is available. We also propose a novel relay selection scheme when only statistical channel state information (SCSI) of all the links is available. The proposed scheme can be used in networks where feedback of FCSI to the decision making node is power intensive and CSI of the eavesdropper cannot be obtained at all instants. In the results section we show that the approximate expression follows the simulations exactly and the outage for relay selection in FCSI decreases with an increase in the number of relays.

Majority logic fusion of censored decisions in wireless sensor networks with Rayleigh fading

In this paper, we consider a binary decision fusion problem for a wireless sensor network, with flat Rayleigh fading, where the sensors make local binary decisions on the status of a common binary phenomenon. A training-based channel estimator is used at the fusion center (FC) to estimate the complex Gausssian fading coefficients characterizing the (direct) links between sensors and FC. This (estimated) channel state information is used, by proper thresholding, to censor the sensors. On the other hand, a locally optimal decision threshold is considered for binary quantization at the sensors. The average detection error probability at the FC, under the use of a majority logic fusion rule, is selected as a qualitative measure of system performance and is evaluated by simulation. The impact of the choice of the censoring threshold on the average detection error probability, under several values of channel estimation error, channel SNR, and sensor SNR, is studied.

Optimal Power Allocation for Multiuser Secure Communication in Cooperative Relaying Networks

We consider a cooperative relaying network in which a source communicates with a group of users in the presence of one eavesdropper. We assume that there are no source-user links and the group of users receive only retransmitted signal from the relay. Whereas, the eavesdropper receives both the original and retransmitted signals. Under these assumptions, we exploit the user selection technique to enhance the secure performance. We first find the optimal power allocation strategy when the source has the full channel state information (CSI) of all links. We then evaluate the security level through: 1) ergodic secrecy rate and 2) secrecy outage probability when having only the statistical knowledge of CSIs.

Joint Optimal Power Allocation and Relay Location for Amplify-and-Forward Multihop Relaying over Lognormal Channel

In this paper, a joint optimization of power allocation (PA) and relay location is proposed for Amplify-and-Forward (AF) multihop relaying over independent lognormal fading channels. The proposed optimization method maximizes the end-to-end (e2e) average signal-to- noise ratio (ASNR) having constraints on total transmit power with no per terminal maximum limit and assuming fixed e2e distance. Optimal parameters do not depend on instantaneous channel state information (ICSI) and can reduce complexity and power consumption. Optimal PA for maximizing e2e instantaneous SNR (ISNR) is also derived considering same constraints. Outage performance of joint optimization method based on ASNR and optimization method based on ISNR is compared. It is observed that joint optimization not only performs better than equal allocation, it can also outperform PA based on ISNR when link unbalance is large.

Distributed detection using MRC with censored sensors and rayleigh faded communications

In this paper, we consider the problem of fusing decisions in a distributed detection system when the local binary decisions made at the sensors, relative to observations of a common binary phenomenon, are transmitted over wireless links subject to Rayleigh flat fading and additive noise. A training-based channel estimator is used at the fusion center (FC) to estimate the complex Gaussian fading coefficients characterizing the channels between the sensors and the FC. We use channel state information (CSI) on the fading coefficients for censoring the sensors. Locally optimal decision threshold is considered for binary quantization at the sensors. The detection error probability, using a maximal ratio combining (MRC) fusion rule, is selected as a qualitative measure of system performance and is evaluated by means of simulations. We also use majority logic fusion at the FC to compare detection error probability with MRC after censoring sensors. We study the effects, on the system performance, of the channel estimation error, the channel signal-to-noise ratio (SNR), the sensor SNR, and the number of selected sensors.

Distributed detection with censoring of sensors in Rayleigh faded channel

This paper considers the problem of fusing decisions in a distributed detection system when the local binary decisions made at the sensors, relative to observations of a common binary phenomenon, are transmitted over Rayleigh faded channel subject to additive noise. We use a training-based channel estimator at the fusion center (FC) to estimate the complex Gaussian fading coefficients characterizing the channels between the sensors and the FC. Channel state information (CSI) is used on the fading coefficients for censoring the sensors. Locally optimal decision threshold is considered for binary quantization at the sensors. The detection error probability is selected as a qualitative measure of system performance in the presence of majority logic fusion at the FC and is evaluated by means of simulations. We study the effects of the channel estimation error, the channel signal-to-noise ratio (SNR), the sensor SNR, and the number of selected sensors on the system performance.