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In this paper, a cyber-physical system (CPS) is considered, whose state estimation is done by a central controller (CC) using the measurements received from a wireless powered sensor network (WPSN) over fading channels. An adversary injects false data in this system by compromising some of the idle sensor nodes (SNs) of the WPSN. Using the WPSN for transmitting supervision and control data, in the aforementioned setting, makes the CPS vulnerable to both error and false data injection (FDI). The existing techniques of launching stealthy FDI attack are not applicable to the aforementioned network due to the random nature of wireless channels, which is used for both transmitting control and false data. The objectives of the adversary and the CC to launch stealthy FDI attack and to detect the same, respectively, are found to be depending on the powers they use for transmitting data over wireless channels. The transmit powers of the CC, and the adversary that fulfill their respective objectives are derived by modeling their interaction as a Bayesian Stackelberg game. Based on their objectives, novel utility functions are defined for the CC and the adversary. Subsequently, the equilibrium of the proposed game is obtained by solving a non-convex bi-level quadratic-quadratic program. Finally, the analytical results are verified and compared with other state-of-art techniques by applying them in a realistic smart grid simulations.

In this article, we summarize the research conducted for YFRFs of Visvesvaraya PhD Programme. The research work is mainly focused on the design and analysis of wireless communication networks. We also explore the spectral and energy efficiency aspects of future generation networks like smart grid communications. This research is useful for improving the performance of current and future generation of communication systems.

Introduction: In this paper, we consider a fundamental problem of testing faced by the health staff on testing COVID 19 patients. In general, the number of testing kits or testing capabilities is limited, and the number of COVID 19 patients is much larger than that. This paper tries to answer this fundamental question that how to perform COVID 19 testing to reduce the death rate. Materials and Methods: We consider that the survival rate of patients is dependent over two parameters: their age and severity of symptoms at a time. Based on these observations, we propose a survival rate function. Using the survival rates, the death rate for an individual is obtained. MATLAB was used for plotting the graphs. Results: It is shown by numerical results that by using the proposed mechanism, the average death rate can be significantly reduced. Conclusion: It is proposed to conduct the testing for those patients who lie in the high death rate regimen.

We consider a cognitive radio (CR) network with simultaneous wireless information and power transfer (SWIPT) system having one base station (BS) with multiple antennas that acts as a secondary transmitter, one desired information receiver (IR) acting as secondary receiver, multiple primary users (PUs) having licenses band of spectrum, and multiple energy harvesting receivers (EHRs). The EHRs harvests energy from the BS and eavesdrop the information from signal. In order to extract the information and then harvest energy from that signal, power splitting is considered in each EHR. On the basis of an imperfect channel state information (CSI) in IR, selection of the best transmit antenna at the BS is made. The effect of path loss on the system is also considered. The derivation of analytical expression in closed-form is provided for the exact secrecy outage probability (SOP) of the network. The derived expression highlights the variation in the secrecy outage of the considered CR SWIPT system relying on imperfect CSI with respect to the system parameters, which is depicted through numerical analysis. Furthermore, we derive the asymptotic SOP and study the effects of different system parameters on the secrecy diversity order and secrecy array gain.

In this work, the authors consider the communication network of a power substation, where multiple intelligent electronic devices (IEDs) transmit their delay sensitive control and monitoring messages to a common receiver over a wireless network; in the presence of a broadband jammer, which is capable of jamming multiple channels simultaneously. The objective of the IEDs is to successfully transmit their messages within a specified time, whereas the jammer wants to obstruct IED's transmission. A novel utility function is designed for the players, that addresses the time-critical nature of communication. Due to the conflicting interest of the IEDs and the jammer, they model the interaction between them as a repeated Bayesian zero-sum game, which also addresses the repeated interaction among the IEDs and the jammer, and the unavailability of exact information about the jammer. The equilibrium strategies for both the scenarios of perfect and imperfect monitoring are derived and verified through simulation results. Further, the performance of the proposed game model in various scenarios is thoroughly compared in the result section. Finally, the efficacy of the proposed defence strategies is tested in a practical communication network of a power substation under jamming, which is simulated in Optimised Network Engineering Tool (OPNET).

We propose to use 1-bit feedforward information at the free-space optical (FSO) receiver to improve its error performance. We concentrate upon M -ary pulse amplitude modulation (PAM) signaling and design an error-optimal PAM constellation for providing efficient 1-bit feedforward information to the receiver. A maximum likelihood detector is derived, and the symbol error rate of the considered FSO system is analytically obtained in closed form by using a union-bound approach. It is shown by using the analysis and simulation that 1-bit feedforward can significantly improve the performance of PAM in FSO systems.

In this paper, the effect of jamming in a free-space optical (FSO) communication system that employs optical space shift keying (OSSK) is studied. The optical link suffers from saturated atmospheric turbulence (AT). Hence, the channel fading coefficients follow negative exponential probability density function (PDF). Along with additive Gaussian noise, the jammer, under consideration, is an additional source of noise, and jamming signals also suffer from saturated AT. Thus, the jamming channel also follows the negative exponential PDF. A multiple-input single-output (MISO) FSO system is used to mitigate the effects of jammer and channel fading. Explicitly, we employ a 2 × 1 MISO-OSSK system for analysis and derive a closed-form expression of bit error rate (BER) of the considered system. Moreover, the jammer’s effect is also studied numerically under the gamma-gamma (GG) fading channel.

In this paper, we study the effect of a beamforming scheme for a multiple-input-single-output (MISO) uplink free-space optical (FSO) communication system with nonorthogonal multiple access (NOMA) over negative exponential fading channels. 1-bit feedback about the channel state information is required by the proposed beamforming scheme. The feedback is considered to be error-free in this work; however, an error due to successive interference cancellation (SIC) is taken into consideration. It is inferred by bit error rate (BER) analysis that a higher weight given to the channel with higher channel gain and a slightly lower weight given to the channel with lower channel gain gives the best performance as compared to all arbitrary schemes in a 2 × 1 FSO-NOMA system. Further, it is also analytically shown that using a 1-bit feedback-based beamforming scheme in an FSO-NOMA system suppresses the effect of SIC error; hence the BER performance of both the transmitters (TXs) is the same, which is not the case for a conventional NOMA scheme. A simplified asymptotic upper bound of BER of the proposed scheme is obtained by using the order statistics, and an optimized beamforming vector is found by minimizing this upper bound. It is then established analytically as well as through simulations that the beamforming vector is independent of average signal-to-noise ratio as long as the two channels remain independent and identically distributed. We further compare the proposed scheme with an FSO-NOMA system without feedback and beamforming and with single-input single-output FSO system using 4-ary pulse amplitude modulated signaling. It is shown by simulations that the proposed scheme outperforms both of them and has a huge coding gain advantage. A numerical analysis of this scheme is also provided for gamma-gamma (GG) and log-normal (LN) turbulence regime. The proposed scheme is extended to 3 × 1 and 4 × 1 MISO systems, and it is revealed that the performance of the system degrades as the number of TX increases.

International audience; In the last decade Internet of Things (IoT) grew up in an exponential behavior with applications requiring long range and low power wireless transmissions. Factory of the Future (FoF), also called Industry 4.0, aims to use IoT technologies to enhance productivity, therefore adding high reliability constraints. Several IoT standards were proposed and LoRa has emerged as a high potential candidate for a variety of applications. LoRa modulation is based on a chirp spread-spectrum technique and offers efficient transmission up to 50 kbps over several kilometers. The performance of LoRa in terms of symbol or bit error probability has been theoretically analyzed in few recent papers for a Gaussian channel. However, the industrial environment is often corrupted with impulsive non Gaussian noise generated by high-power equipment. In this paper, the impact of impulsive noise, modeled by the Middleton Class-A noise, is introduced and the robustness of a LoRa communication is studied. Compared to the Gaussian case, simulations show that impulsive noise may severely degrade system performance. This Signal-to-Noise Ratio loss can reach up to 10 dB, but increasing the spreading factor can reduce the noise impact.

In this paper, we propose a virtual full-duplex (VFD) multi-hop cooperative relaying network using buffer-aided halfduplex (HD) relays. Firstly, for a given multi-hop network, the links are partitioned into three groups and then information is transmitted over a single time slot using two selected best links, which enhances the network coverage and reliability of the system. The Markov chain approach is used to analyze the state transition matrix which models the evolution of buffer states. An analytical expression of steady state probability is obtained, using which the outage probability of the system is evaluated. Numerical results validate our analytical findings and it shows that the proposed relaying scheme offers a better outage performance as compared to that of the conventional buffer-aided max-link relay selection scheme in a multi-hop communication system.

Multi-hop relaying is used to extend the reach of wireless communication systems whereas cooperative relaying is used to improve the performance gain by exploiting the spatial diversity. In this study, the authors combine these two techniques to improve the range as well as the performance gain of cognitive radio networks (CRNs). Selective decode-and-forward relays are considered and two relay selection schemes are used to study the performance of multi-hop CRNs over Rayleigh fading channels. The exact outage probability and throughput of the considered system are derived for both the schemes by considering the effect of both peak-power and peak-interference constraints. By using the derived outage probability, the diversity gains for both considered schemes are determined. Numerical results show that the outage probability monotonically improves, whereas the throughput has concave behaviour with respect to increasing number of relaying hops.

Multihop relaying is used for increasing the communication range of cognitive radio networks. To circumvent the implied loss in throughput due to multihop relaying, in this paper, we propose incremental relaying (IR) for cooperative multihop cognitive radio networks (CMHCRNs). Two IR protocols that select a relay from the qualified relays (the relays whose received signal-to-noise-ratio (SNR) values are greater than a predefined threshold) in each hop are proposed to study the performance of the considered CMHCRN. The first protocol is named IR-based highest SNR (IR-HSNR) protocol that selects a relay with best SNR to the destination. Another one, termed IR-based highest transmit power (IR-HTP) protocol, selects a relay with the highest available transmit power. Expressions for the exact outage probability and throughput are derived for both routing protocols by considering both peak–power and peak–interference constraints. Moreover, closed-form expressions for floor values of outage probability and throughput are derived for both the protocols. It is shown through numerical results that throughput of the considered system shows a concave behavior with respect to number of relaying hops for both the proposed protocols. It is further observed that the performance of the IR-HSNR is superior to that of the IR-HTP, whereas the latter has lower implementation complexity.

In this paper, we present a method of utilizing channel diversity to improve the secrecy outage probability and the intercept probability in a cognitive radio (CR) network. With the presence of channel diversity, an intended receiver can achieve a relatively better secrecy outage probability and intercept probability. We consider a CR network in which a single antenna, which maximizes the secrecy capacity, is selected at the CR transmitter. To demonstrate the advantages of our proposed framework, we derive new exact closed-form expressions for the secrecy outage probability and the intercept probability of the secondary network in Rayleigh fading. The positive impact of the number of receive antennas and the negative impact of the number of primary users on the secondary network are shown. The derived secrecy outage probability is found to be in precise agreement with simulation results. The numerical results strongly support our conclusion that maximal-ratio combining of channel diversity can enhance the physical layer security of a multiantenna based CR network. Furthermore, the numerical results reveal the impact of the primary network on the secondary network in the presence of a multiantenna wiretap channel.

We study the secrecy performance of one bit imperfect feedback-based diagonal precoder for Alamouti multiple-input single-output (MISO) system in the presence of a single antenna equipped eavesdropper. An error-tolerant weighting (ETW) scheme is employed for transmit power allocation. The exact and asymptotic closed-form expressions of the secrecy outage probability (SOP) of the considered MISO system are derived with the ETW scheme. Also, the SOPs of uniform power allocation (UPA) scheme and best transmit antenna selection (BTAS) scheme with erroneous feedback are derived. Analysis shows that the proposed ETW scheme provides a significant secrecy performance gain in comparison to UPA scheme and remains insensitive to feedback error, unlike the BTAS scheme.

In this paper, an underlay-based cognitive radio network (CRN) consisting of a secondary transmitter (ST), a secondary receiver (SR), an energy harvesting node (EHN), and a primary transmitter-receiver pair, is considered. The EHN is an energy constrained node and is thereby, assumed to have a power splitter at its receiver to decode information and harvest energy simultaneously from the received RF signal. The EHN behaves maliciously and decodes ST’s messages when it is granted with a permission to (only) harvest energy from the received RF signal, thereby reducing the secrecy capacity of the ST-SR link. Since both ST and EHN are selfish with conflicting interests, we model the interaction between them as a Stackelberg game (SG). Further, we analyze the behavior of the nodes in a non-cooperative game (NCG) theoretic framework and prove the existence of a unique Nash equilibrium (NE) strategy. Simulation results show that the SG framework performs better than the NCG framework, in terms of the achievable secrecy capacity of the ST-SR link. Thereby the proposed SG model is applied to the considered CRN with multiple STs and a unique equilibrium is found. In case the STs possess limited channel state information (CSI), we model the competition among the STs as a Bayesian game and found its equilibrium solution, known as Bayesian NE (BNE). Simulation results demonstrate that BNE performs better than the NE when the STs possess limited CSI.

This paper presents novel experimental results for a 10 Gb/s triple-hop relay-based all-optical free space optical (FSO) system by employing the amplify-and-forward relaying scheme. We provide a mathematical framework for the end–end signal-to-noise ratio (SNR) and the bit-error rate (BER) performance and confirm that the derived analytical results reasonably match experimental results especially at relatively high SNR. The evaluated BER performances under different atmospheric turbulence regimes (modeled by the Gamma–Gamma distribution) show that the considered relay-assisted FSO system offers a significant performance improvement for weak-to-strong turbulence regimes, even without knowledge of the channel state information. More precisely, at a target BER of 10–5 , the proposed scheme offers ∼5 and ∼4 dB of SNR gains compared to the direct transmission for turbulence strengths $\ {\boldsymbol C}_{\boldsymbol n}^2$ of $3.8 \times {10^{ - 10}}\,{{\rm{m}}^{ - 2/3}}$ and $5.4\times 10^{-12}\,{{\rm{m}}^{ - 2/3}}$ , respectively.

Optical space shift keying (OSSK) is a multiple transmit aperture based scheme which attains improved spectral efficiency in optical wireless communication (OWC). In addition to atmospheric turbulence (AT), pointing error (PE), which originates due to vibrations or building sway, has potential to deteriorate the performance of OWC link. This paper discusses the effect of AT and PE jointly on the performance of OSSK scheme. An analytical framework is proposed for evaluating average bit error rate (ABER), coding gain, and diversity order of OSSK scheme. It is found by analysis that for low PE, error performance of OSSK in weak AT condition is poorer than that in strong and moderate AT conditions. However, for high PE, the trend is the reverse. ABER, coding gain, and diversity order for pulse amplitude modulation (PAM) over AT and PE are also derived in order to compare its performance with the same rate OSSK scheme. The analysis shows that OSSK is less sensitive to PE severity as compared to PAM. Also, the diversity order of OSSK is independent of AT and PE, whereas the diversity order of PAM depends on both AT and PE, which makes OSSK a suitable modulation scheme for the practical scenario.

This paper presents experimental results for an all-optical free-space optical (FSO) relay-assisted system by employing an all-optical regenerate and forward (AORF) scheme in order to increase the transmission link span. The ultra-short pulse (i.e., 2 ps) regeneration technique based on Mamyshev method is adopted. We have developed a dedicated experimental test-bed composed of optical fiber components and FSO links to demonstrate the proposed scheme and evaluate its performance in terms of the Q-factor and bit error rate (BER) under turbulence regimes for both single and dual-hop network architectures. We show that, using the AORF a hundred times improvement in the BER performance is achieved compared to the amplify-and-forward scheme for a fixed signal-to-noise ratio under turbulence conditions.

We analyze the outage performance of a buffer- aided dual-hop decode-and-forward cooperative relaying network with co-channel interference (CCI) and additive white Gaussian noise (AWGN) at the relay and the destination nodes. We propose a max-signal-to-interference plus noise ratio (max- SINR) relaying protocol in which the data transmission takes place in the link having the maximum SINR among the available source-relay and relay-destination links. It is assumed that the envelopes of the desired signal and the interfering signal follow asymmetric channel configuration with Rayleigh distributed fading. We consider a finite size data buffer equipped at the relay nodes. A discrete Markov chain approach is adopted to model the evolution of the relay buffers' status and to derive a closed-form expression for the outage probability. Numerical results demonstrate that in the cooperative networks with CCI and AWGN, employing a data buffer at the relays and adopting the max- SINR relaying protocol lead to an improvement in the performance of outage in comparison to the max-min relaying protocol without a buffer. The buffer-aided relaying protocol can improve the reliability of a cooperative network with CCI and AWGN as compared to the non buffer-aided relaying protocol.

This paper outlines experimental investigation of the performance of the wireless optical network based on an all-optical triple-hop free space optical (FSO) communications employing amplify-and-forward relaying under the influence of atmospheric turbulence. We present new results for the bit error rate (BER) performance for seven possible turbulence network scenarios for relay-assisted FSO link and validate them with numerical simulations based on Gamma-Gamma turbulence model showing a good agreement between them. We also show results, which elucidate the impact of non-homogeneous turbulence along the entire transmission link span for the multiple-hop relay-assisted FSO system. More specifically we show that the BER performance considerably deteriorates for the case where turbulence is near to the receiver end. We outline that for a target BER of 10−4 the signal-to-noise ratio penalty can be as high as 9 dB compared to the case with no turbulence.

In this paper, imperfect feedback-based linear precoding schemes are proposed for multiple-input-multiple-output (MIMO) wireless communication systems, where input symbol streams are encoded by using generalized-orthogonal space-time block codes. The imperfect feedback information drastically degrades the system performance. Therefore, to overcome the effect of erroneous feedback information, error-tolerant weighting (ETW) schemes are implemented by employing diagonal precoder. The communication links are assumed to be Nakagami- $m$ distributed for accurately characterizing practical wireless channels under different fading scenarios. Exact and asymptotic symbol-error-rate (SER) expressions of the considered MIMO system are derived under imperfect feedback with the help of order statistics. The most appropriate values of the transmit weights of the precoder matrix are obtained by minimizing the derived average SER over fixed and adaptive signal-to-noise ratio. Further, we study the trade-off between the proposed optimal and suboptimal feedback-based precoding schemes. Moreover, the ergodic-rate of the ETW schemes is also derived with imperfect feedback for arbitrary MIMO system by using the moment generating function approach. The simulated and analytical results show that a significant performance gain is achieved by the ETW schemes as compared to the uniform power allocation and existing precoding techniques under erroneous feedback information.

Cell signalling plays a vital role in development, sustaining, differentiation, and reproduction of cells. Pathways involved in signalling networks are quite interwoven and complex. Complexity encountered in understanding these pathways is often reduced with the help of Boolean circuit representation. In this study, the authors provide communication aspect of the signalling pathways that have two input Boolean logic AND/OR implemented at the rear effector protein. Communication is assumed to be taking place in extracellular and intracellular environment. The two environments are connected using a receptor protein acting as relay between a molecular source and effector protein. Each relay detects molecules from outside environment and stimulates the production of signals in the intracellular space. These signals/molecules further activate the effector protein which acts as a Boolean switch driven by AND/OR logic. Assuming Poisson reception at the relay as well as at the receiver, the authors provide probability of error of the AND and OR Boolean logic communication systems. Furthermore, reliability and some capacity bounds are deduced for the given Boolean communication system.

In this paper, we propose a simple and a low cost 1 Gbps Ethernet free-space optical (FSO) communications link, which can be used both for the last meter and last mile access networks. In the emerging fifth generation wireless systems, which require at least an order of magnitude increase in the peak data rates and three orders of magnitude increase in network capacity with reduced latency, deploying multiple technologies will play a crucial role to meet these requirements. One possible complementary wireless technology to the radio frequency is the unlicensed FSO, which can bridge the gap between the existing RF wireless and optical fibre communication networks by providing high data rates, low installation costs and high energy efficiency. In this work, we propose a high-speed FSO system, which can be readily implemented using off the shelf components, and assess its performance experimentally under turbulence and fog conditions using the dedicated indoor atmospheric chamber. We show that, the proposed system under the turbulence condition with a scintillation index of 0.43 offers almost the same data rate (i.e., ∼99%) as the link under a clear channel, while the packeterror-rate reduces from 10−3 to 2 × 10−2.

The concept of hybrid free space optical/radio frequency (FSO/RF) communications has been considered for the last mile access network applications. The existing schemes mostly use two separate transceiver antennas for outdoor terrestrial links of few kilometres long. In this paper, we propose and investigate a single hybrid FSO/RF antenna that could be used in high-speed access networks. We outline the design procedures based on the concept of Cassegrain antenna, and show how the FSO transceiver is incorporated into the original design. The proposed antenna is fabricated and extensive measurements are carried out for the radiation pattern, return loss, RF signal-to-noise ratio and the FSO received power. By performing link budget analysis and the results obtained from experiments, we demonstrate the operation of proposed hybrid antenna with 1 × 3 single-input multiple-output configuration and an equal gain combining at the receiver under moderate regime turbulence regime.

In this letter, a cognitive radio-based simultaneous wireless information and power transfer system consisting of one base station, one desired information receiver, multiple primary users, and multiple energy harvesting receivers is considered. Each link in the system suffers from small scale fading and path loss. We focus on the secrecy outage in this network, keeping in mind that the multiple energy harvesting receivers may act as potential eavesdroppers. A closed-form analytical expression for the exact secrecy outage probability is derived, and some useful insights are obtained. Numerical and Monte Carlo simulation results are presented to validate our analysis.

In this study, the authors have analysed the performance of selection relaying at each hop in a decode-and-forward (DF)-based multi-hop cognitive radio (CR) system deploying cooperative spectrum sensing. The decisions on spectrum availability are taken by a number of sensing CRs (SCRs) at the first level and are sent to a fusion centre (FC) over pre-existing clusters of relaying CRs (RCRs). The RCRs are being used in a secondary role for relaying the spectrum decision besides sensing their own area primary user. The decision of each SCR is relayed to FC one-by-one via number of RCR clusters by selecting a maximum signal-to-noise ratio link at each cluster independently. The selected RCR forwards the decision to the next level using DF protocol. The closed-form expressions for probability of missed detection and false alarm are derived at the FC. An optimal combining rule is devised at the FC. A comparative graphical analysis of power saving in case of multi-hop transmission to that of single-hop transmission is also presented. The number of hops for the considered system is optimised based on a trade-off relation between error rate and transmission delay.

In this paper, we consider a single-relay-based decode-and-forward (DF) cooperative multiple-input multiple-output (MIMO) system in which the source, the relay, and the destination are equipped with $N_{s}$ , $N_{r}$ , and $N_{d}$ antennas, respectively. We propose a joint antenna and path selection scheme, which jointly selects the single-transmit and single-receive antenna pairs, along with the selection of either a direct path that consists of source–destination channels or a cooperative path that consists of source–relay and relay–destination channels. The proposed selection scheme is based on the maximization of minimum of maximums (max-min-max) criterion of instantaneous signal-to-noise ratio (SNR). The analysis in this paper is based on the assumptions that all the channels follow independent Rayleigh fading. A closed-form expression of the symbol error rate (SER) for the proposed scheme in a cooperative MIMO system with $M$ -ary phase-shift keying is derived. We extract the analytical diversity order from the derived SER and show that the proposed selection scheme achieves the diversity order of $N_{s}N_{d}+N_{r}\mathrm{min}(N_{s},N_{d})$ in the considered cooperative MIMO system. Closed-form expressions of bandwidth efficiency (BE) and ergodic capacity $(C_{t})$ are derived for the proposed scheme. An optimized selection parameter from the specific set of values is numerically evaluated by maximizing a heuristic utility function $(C_{t}\times \mbox{BE}/\mbox{SER})$ . By using the already-gathered information about the maximum instantaneous SNR of every hop, a power adaptation scheme that maximizes the instantaneous SNR in the cooperative path is proposed and analyzed. The proposed power adaptation scheme, which is applied only in the event of selection of a cooperative path, outperforms the uniform-power-distribution-based DF cooperative MIMO system.

Cooperative spectrum sensing in a multihop cognitive radio (CR) network based on multiple antennas using an improved energy detector is studied in this paper. The improved energy detector uses the $p$ th power of the absolute value of samples of primary user's (PU's) signals. We replace the conventional energy detector by an improved energy detector to enhance the performance of CR. Analytical expressions of the probability of false alarm and missed detection in each CR are derived. Furthermore, we extend our study to a multihop cooperative diversity system containing multiple multihop secondary transmission paths between the PU and the fusion center. Performance analysis of multihop cooperative diversity is discussed using an improved energy detector. We introduce a framework to derive a closed-form expression of the optimal number of multihop cooperative diversity branches by minimizing the total error rate. An efficient quick spectrum sensing algorithm is proposed, which requires fewer than the total number of cooperative multihop diversity branches. It is shown, through various numerical examples, that by using the optimal number of secondary transmission paths, it is possible to perform quick spectrum sensing while satisfying an upper bound on the total error rate.

In this paper, we investigate relay-assisted visible light communications (VLC) where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The focus of the paper is on analysis of the behavior of the mobile user acting as a relay while considering a realistic locations of the receivers and transmitters on a standard mobile phone, more specifically with two photodetectors on both sides of a mobile phone and a transmitting LED array located upright. We also investigate dependency of the bit error rate (BER) performance on the azimuth and elevation angles of the mobile relay device within a typical office environment. We provide a new analytical description of BER for AF and DF-based relays in VLC. In addition we compare AF and DF-based systems and show that DF offers a marginal improvement in the coverage area with a BER < 10–3 and a data rate of 100 Mb/s. Numerical results also illustrate that relay-based systems offer a significant improvement in terms of the coverage compared to direct non-line of sight VLC links.

In this paper, we propose, for decode-and-forward cooperative networks, a relaying scheme which is based on giving a priority to the status of relay buffers along with the highest channel gain of wireless links. Specifically, we divide the set of relay buffer status into three priority classes: i) the first priority is given to relay buffers which are full, ii) the second priority to relay buffers which are empty, and iii) the third priority to relay buffers which are neither full nor empty. Within a priority class, a relay node is selected corresponding to the link having the highest channel gain. We adopt a Markov chain approach to analyze the state transition matrix that models the evolution of the relay buffer status. Analytical expressions for the outage probability and the diversity order are derived. The proposed scheme is illustrated with an example and analytical expressions for the steady-state probability vector are obtained. It is also shown that the states having the same probabilities can be grouped. Furthermore, we explain the construction of the reduced state transition matrix. Our analytical and simulation results demonstrate that the proposed scheme has the potential to provide better outage performance over the conventional maxlink scheme.

In this paper, we propose an imperfect quantized feedback-based diagonal precoding scheme for generalized orthogonal space-time block codes in an $N \times 1$ multiple-input single-output (MISO) wireless communication system employing $M$ -QAM constellation. It is well known that a feedback-based precoding scheme aids channel adaptive signaling in wireless communication system and capitulates large improvements in almost all performance metrics. However, a practical feedback link is susceptible to error due to wireless channel fading and leads to wrong precoder selection. Therefore, a signal-to-noise ratio (SNR) adaptive error-tolerant weighting scheme is introduced which provides significant gain in comparison with another proposed arbitrarily fixed SNR error-tolerant weighting scheme. At first, a tight approximate closed-form expression of average symbol-error-rate (SER) and an exact analytical expression of outage probability are derived under imperfect feedback information with the help of order statistics. By minimizing the derived average SER, optimized transmit weights for the diagonal precoding matrix (based on feedback bits) are obtained. Later, a closed-form expression of the ergodic capacity with erroneous feedback bits for arbitrary MISO system is also provided by using the moment generating function approach. Further, numerical results show that the considered error-tolerant schemes outperform the uniform power allocation scheme in term of all the investigated performance metrics.

Wireless communications and power line communications (PLC) are essential components for smart grid communications. This paper analyses the performance of a dual-hop wireless-power line mixed communication setup employing a decode-and-forward relay in terms of analytical average bit error rate (BER), outage probability, and average channel capacity. The Nakagami-m distribution captures the wireless channel fading; whereas the PLC channel gain is characterized by the Log-normal distribution. The additive PLC channel noise is assumed to be Bernoulli-Gaussian distributed. Approximate closed-form expression of the average BER and exact closed-form expression of the outage probability are derived for the considered system. Further, we obtain an approximate closed-form expression of the capacity of the wireless-power line mixed system in terms of the Meijer-G function. It is observed that the system performance deteriorates as the impulsive noise index and the arrival probability of the impulsive component of the PLC additive noise increase. (C) 2018 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

Power line communication (PLC) is the use of power lines for the purpose of electronic data transmission. The presence of additive noise, namely, background noise and impulsive noise, significantly affects the performance of a PLC system. While the background noise is modeled by Nakagami- $m$ distribution, the impulsive noise is modeled using Middleton class A distribution. In this letter, we study the performance of a PLC system under the combined effect of Nakagami- $m$ background noise and Middleton class A impulsive noise assuming binary phase shift keying signaling. The probability density function of decision variable under the influence of additive noise (sum of background noise and impulsive noise) is derived. We also derive an analytical expression for the average bit error rate of the considered PLC system. The analytical expressions are validated by close matching to the simulation results. The analysis presented in this letter closely predicts the behavior of the PLC system under the combined effect of background and impulsive noises.

The error performance of the free space optical (FSO) link suffers from the atmospheric turbulence. By employing an additional transmit aperture at the transmitter along with Alamouti code, the error rate of the FSO communication system can be significantly improved. However, the pointing errors, generated because of the building sway, has the potential to eradicate the benefits of the Alamouti scheme. Therefore, for a general and realistic study of the FSO based Alamouti scheme, the effect of pointing errors in the Gamma-Gamma fading atmospheric fluctuations is considered in this paper. Specifically, we derive the symbol error rate and the average capacity of the Alamouti scheme over the Gamma-Gamma fading FSO links with pointing errors. The moment generating function (MGF) of the scheme is derived in terms of the Meijer-G function. An MGF based approach is used to derive the ergodic capacity of the scheme. The effect of pointing errors over the performance of the scheme is analyzed under different scenarios and it is observed that the pointing errors significantly degrade the diversity of the considered FSO system.

In free space optical (FSO) communication systems, atmospheric turbulence is the major cause of bit error rate (BER) performance degradation. The error performance of the system can be significantly improved with the help of spatial diversity by employing multiple transmit or receive apertures. However, correlation of channels under turbulence in the case of small separation between transmit apertures can substantially reduce the benefits of spatial diversity. Still, a thorough analysis of the system performance in terms of diversity order and coding gain for the FSO multiple-input single-output (MISO) system under turbulence influenced correlated channels has not been studied when the repetition coding is used to achieve improved BER performance. In this paper, we provide unique results of the BER performance analysis of the considered correlated FSO-MISO system over Gamma–Gamma distributed turbulence channel. Using the joint moment generating function of received signal-to-noise ratio (SNR), a novel generalized approximate BER expression is derived, followed by convergence test of the power series based BER expression using the Cauchy's ratio test. Then, an asymptotic analysis at high SNR is performed to obtain a novel closed-form expression for BER of FSO-MISO system. We also derive expressions for coding gain, diversity gain, and coding gain loss due to correlation in channels. Although the effect of correlation in channels on the BER performance of the system is analyzed under different scenarios, while it is observed that it does not affect the diversity order; it significantly degrades the coding gain of the considered system.

The performance of a free-space optical (FSO) communication system is significantly affected by atmospheric turbulence (AT) and pointing errors (PEs) apart from the additive noise which follows the Gaussian distribution. Optical pre-amplifier is an essential component of FSO systems for improving the receiver sensitivity. However, optical pre-amplification results into amplified spontaneous emissions (ASEs) which dominate the receiver thermal and shot noises. The square law photodetection process at the receiver in a FSO system necessitates the consideration of Chi- square statistics for the decision variable; contrary to the Gaussian approximation that is widely used in literature. In this paper, we evaluate the bit error rate (BER) performance of a FSO system assuming non-return-to-zero on-off keying modulation in the presence of ASE noise under Gamma-Gamma ($\Gamma\Gamma$) AT and PEs. We also derive an expression of asymptotic BER for the considered FSO system for large values of signal-to-noise ratio in terms of simple elementary functions. A further insight into the system is provided by performing the diversity analysis.

This paper investigates the performance dependence of a hybrid free space optical (FSO)/radio frequency (RF) communication system on the data rate, link distance and link availability. In existing hybrid FSO/RF systems with hard switching, an algorithm is used to switch between FSO and RF and vice versa based on the feedback of the channel state information. In particular, two methods based on time hysteresis (TH) and power hysteresis (PH) are widely used in hard switching protocols. Although switching parameters including the time and power thresholds have been studied, the effect of link parameters has not been investigated in the literature. In this paper, we analyse the performance of a hybrid FSO/RF system under realistic channel conditions for both TH and PH switching schemes. By means of analysis and simulation, we show that increasing the data rate of individual FSO or RF link does not necessarily result in higher data rate and improved link availability in a hybrid FSO/RF system.

To increase the communication range of multi-hop cognitive radio networks (CRNs) while avoiding the implied loss in throughput, use of incremental relaying has been suggested. In this paper, we discuss an incremental relaying (IR) protocol for cooperative multi-hop CRNs (CMHCRNs). A CMHCRN with multiple decode-and-forward relays in each hop is considered. In each hop, the relays whose received signal-to-noise-ratio (SNR) values are greater than a predefined threshold constitute a qualified relay set (QRS). The performance of an IR protocol that selects a relay from the QRS that has the highest SNR to the destination at each hop of the CMHCRN is analyzed. Both peak transmit power and peak interference power constraints are taken into account. The end-to-end outage probability and throughput expressions are derived for the considered network over Rayleigh fading channels. Closed-form expressions for floor values of outage probability and throughput are also derived. Based on the derived expressions, we demonstrate that with increase in number of hops, throughput first increases and then decreases.

The realization of a smart grid requires deployment of sensors or measurement devices (MDs) that generate data; this data is securely collected in a central controller or power operator (PO) for further processing. AsMDs are scattered over a large geographical area, they need help of relaying nodes or data concentrators (DCs) to forward their data to the PO. However, the DC nodes are third party devices and are not reliable. In this work, we consider the DC to be an energy harvesting node and is assumed to have a power splitter at its receiver to decode information and harvest energy simultaneously from the MD transmission using simultaneous wireless information and power transfer (SWIPT) technique. However, the DC tends to eavesdrop on the received data, thus reducing the secrecy capacity of MD-PO links. Since both MDs and the DC are selfish with conflicting interests, we model the interaction between them as a non-cooperative Stackelberg game. The objective of the MDs is to maximize the secrecy capacity of their links to the PO, whereas the DC aims at maximizing the information it can decode from the received MDs' signal. The existence of a unique equilibrium point is proved through mathematical analysis. Further, a distributed algorithm is proposed, following which the players will attain the equilibrium of the game as predicted by analytical results. Simulation results validate the analytical results and demonstrate that the proposed framework improves the secrecy capacity of the considered network significantly.

In this paper, we investigate the performance of power line communication (PLC) network in the presence of jamming attacks. The legitimate nodes of the PLC network try to communicate with the anchor node of the network while the jamming node attempts to degrade the system performance. The fading, attenuation and colored noise of the PLC channel with dependence on the frequency and transmission distance are taken into account. To investigate the jamming problem, we frame the adversarial interaction into a Bayesian game, where the PLC network tries to maximize the overall expected network capacity and the jammer node has the opposite goal. In the Bayesian game, both players have imperfect knowledge of their opponents. We study effects of total power available to the players on the equilibrium of the game by formulating it into zero-sum and non-zero-sum games, respectively. It is found that under some network setup, there exists a threshold power for which the actual gameplay of the legitimate nodes does not depend upon the actions of the jamming node, and vice versa. This allows us to choose the appropriate power allocation schemes given the total power and the action of the jamming node in some cases. This is a post-peer-review, pre-copyedit version of an article published in [International Conference on Decision and Game Theory for Security]. Locked until 4.10.2018 due to copyright restrictions. The final authenticated version is available online at: https://link.springer.com/chapter/10.1007%2F978-3-319-68711-7_5

In this letter, we propose a beamforming and combining scheme for a two-way amplify-and-forward protocol-based communication between two multi-antenna earth stations, via a single antenna satellite relay. Under the shadowed-Rician fading, an approximate expression for the symbol error rate of the scheme is obtained based on the moment generating function (MGF) of the instantaneous received signal-to-noise ratio. The proposed expression of MGF contains finite number of summations of the Meijer-G function. By using an asymptotic property of the Meijer-G function, the analytical diversity order of the proposed scheme is also obtained. It is shown by simulations that the considered two-way satellite relaying scheme can overcome the shadowing with improved diversity by increasing the number of antennas at the earth stations.

In this paper, we consider the transmission of signals in a hybrid satellite-terrestrial cooperative system. In particular, we address the problem of beamforming and combining based amplify-and-forward (AF) relaying in a hybrid satellite-terrestrial cooperative system. In this set-up, a multiple antenna based relay node forwards the received satellite signals to the destination, by using a beamforming vector, and multiple antenna based destination node uses maximal ratio combining. The approximate average symbol error rate of the considered beamforming and combining based hybrid AF cooperative scheme for M-ary phase shift keying constellation is derived; analytical diversity order of the hybrid system is also obtained. Moreover, diversity calculations for some specific antenna configurations are shown for providing useful insight of the proposed scheme, at high signal-to-noise ratio.

In this paper, the maximal ratio combining (MRC) scheme in Shadowed-Rician (SR) fading land mobile satellite (LMS) channels is studied. The MRC scheme for SR fading LMS channels has been studied in existing literature; however, most of the existing analytical results are in the form of infinite power series, which are not in closed-form. In this paper, we derive approximate closed-form expressions of the probability density function and cumulative distribution function of the received signal-to-noise ratio of the MRC based receiver in SR fading LMS channels. Then we provide approximate closed-form expressions of the bit error rate (BER), outage probability, and capacity of the considered scheme. One of the derived closed-form BER expressions is found useful for obtaining the analytical diversity order and coding gain of the considered MRC scheme.

In this paper, we study hop-by-hop beamforming and combining in a decode-and-forward (DF) multiple-input multiple-output (MIMO) relay network, with two antennas at each node, over Nakagami-m fading channels. We derive a closed-form expression of the approximate average bit error rate of the considered cooperative scheme with M-ary phase shift keying constellation. In addition, analytical outage probability and diversity order of the considered DF MIMO relay system are also obtained.

In this paper, the transmission of signals in a hybrid satellite-terrestrial link is considered. In particular, we address the problem of amplify-and-forward (AF) relaying in a hybrid satellite-terrestrial link, where a masked destination node receives the relayed transmission from a terrestrial link and direct transmission from the satellite link. The satellite-relay and satellite-destination links are assumed to follow the Shadowed-Rician fading; and the channel of the terrestrial link between the relay and destination is assumed to follow the Nakagami-m fading. The average symbol error rate of the considered AF cooperative scheme for M-ary phase shift keying constellation is derived for these generalized fading channels. Moreover, analytical diversity order of the hybrid system is also obtained.

In this paper, decode-and-forward (DF) based cooperation in a multiple antenna based wireless communication system is studied. In particular, we address the problem of beamforming and combining in a DF multiple-input multiple-output (MIMO) relay network with transmission path selection. A maximum eigenvalue based criterion is used for selection of best transmission path between source and destination nodes. We derive the average bit error rate of the considered cooperative scheme for binary phase shift keying constellation over Rayleigh fading channels. In addition, analytical diversity order of the beamforming and combining based DF MIMO relay system is obtained, for some special cases.

In this letter, we derive the probability density function (PDF) and cumulative distribution function (CDF) of the minimum of two non-central Chi-square random variables with two degrees of freedom in terms of power series. With the help of the derived PDF and CDF, we obtain the exact ergodic capacity of the following adaptive protocols in a {decode-and-forward} (DF) cooperative system over dissimilar {Rician} fading channels: (i) constant power with optimal rate adaptation; (ii) optimal simultaneous power and rate adaptation; (iii) channel inversion with fixed rate. By using the analytical expressions of the capacity, it is observed that the optimal power and rate adaptation provides better capacity than the optimal rate adaptation with constant power from low to moderate signal-to-noise ratio values over dissimilar Rician fading channels. Despite low complexity, the channel inversion based adaptive transmission is shown to suffer from significant loss in capacity as compared to the other adaptive transmission based techniques over DF Rician channels.

In this paper, we derive a differential decoder for the subcarrier intensity modulation (SIM) based differential phase shift keying (DPSK) scheme in free space optical (FSO) multiple-input multiple-output (MIMO) communication system. The proposed differential decoder avoids requirement of the knowledge of irradiance fluctuations in the receiver contrary to the existing selection combining (SC) based decoder of SIM DPSK. Moreover, the proposed differential decoder enables the SIM DPSK scheme to outperform the non-coherent decoding based pulse position modulation scheme. We theoretically analyze the bit error rate (BER) performance of the SIM differential binary phase shift keying modulation scheme with differential decoding over FSO MIMO links which follow the Gamma-Gamma distribution. On the basis of the analytical BER, the analytical diversity order of the proposed differential decoder is obtained.

Optical pre-amplifier forms an important component of a free space optical (FSO) communication system for improving the receiver sensitivity. The use of an optical pre-amplifier results into amplified spontaneous emissions (ASE) which dominates the receiver thermal and shot noises. The square law photodetector at the receiver in a FSO system necessitates the consideration of Chi-square statistics for the decision variable contrary to the Gaussian approximation that is widely used in literature. In this paper, we evaluate the bit error rate performance of a FSO system assuming non-return-to-zero on-off keying modulation in the presence of ASE noise under the combined effect of very strong turbulence (modeled by negative exponential distribution) and pointing errors. A further insight into the system is provided by performing the diversity analysis.