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Wireless Body Area Networks (WBANs) comprise a network of sensors subcutaneously implanted or placed near the body surface and facilitate continuous monitoring of health parameters of a patient. Research endeavours involving WBAN are directed towards effective transmission of detected parameters to a Local Processing Unit (LPU, usually a mobile device) and analysis of the parameters at the LPU or a back-end cloud. An important concern in WBAN is the lightweight nature of WBAN nodes and the need to conserve their energy. This is especially true for subcutaneously implanted nodes that cannot be recharged or regularly replaced. Work in energy conservation is mostly aimed at optimising the routing of signals to minimise energy expended. In this paper, a simple yet innovative approach to energy conservation and detection of alarming health status is proposed. Energy conservation is ensured through a two-tier approach wherein the first tier eliminates `uninteresting' health parameter readings at the site of a sensing node and prevents these from being transmitted across the WBAN to the LPU. A reading is categorised as uninteresting if it deviates very slightly from its immediately preceding reading and does not provide new insight on the patient's well being. In addition to this, readings that are faulty and emanate from possible sensor malfunctions are also eliminated. These eliminations are done at the site of the sensor using algorithms that are light enough to effectively function in the extremely resource-constrained environments of the sensor nodes. We notice, through experiments, that this eliminates and thus reduces around 90% of the readings that need to be transmitted to the LPU leading to significant energy savings. Furthermore, the proper functioning of these algorithms in such constrained environments is confirmed and validated over a hardware simulation set up. The second tier of assessment includes a proposed anomaly detection model at the LPU that is capable of identifying anomalies from streaming health parameter readings and indicates an adverse medical condition. In addition to being able to handle streaming data, the model works within the resource-constrained environments of an LPU and eliminates the need of transmitting the data to a back-end cloud, ensuring further energy savings. The anomaly detection capability of the model is validated using data available from the critical care units of hospitals and is shown to be superior to other anomaly detection techniques., 23 pages, 18 figures. (Full Abstract : https://seemandhar.herokuapp.com/wban)

In this paper, the physical-layer security (PLS for an underlay cognitive radio network (CRN with multiple non colluding eavesdroppers is studied. We assume that a secondary user (SU transmitter communicates with an SU receiver over a cascaded -fading channel and under the threat of eavesdropping. A cooperative jammer exists to improve the SUs security by harvesting energy from the SU transmitter using power splitting technique. This harvested energy is utilized to generate jamming signals to deteriorate the eavesdroppers reception quality. Moreover, the eavesdroppers are assumed to be randomly distributed according to a homogeneous Poisson point process (HPPP, in which the kth closest eavesdropper to the SU transmitter will be selected in our analysis. Additionally, the legitimate receiver is assumed to harvest energy from the SU transmitter using power splitting technique. In this context, we propose an optimum power splitting factor at the legitimate receiver that achieves the best privacy while constraining the amount of the harvested energy. Furthermore, on enhancing system security, we investigate the effectiveness of the jamming technique. The impact of distances over security is also examined. The results reveal an improvement in privacy as the legitimate receiver utilizes the adaptable power splitting factor. PLS is evaluated in terms of the probability of non-zero secrecy capacity and the intercept probability.

In this letter, we consider a secure underlay cognitive radio network consisting of a secondary source-destination pair and a primary transmitter-receiver pair in the presence of a primary passive eavesdropper. Herein, a secondary multi-antenna full-duplex destination node acts as a jammer to the primary eavesdropper in an effort to improve the physical layer security of the primary network. In return for this favor, the energy constrained secondary source gets access to the primary network to transmit its own information so long as the interference to the latter is below a certain level. In light of the aforementioned, we evaluate the system performance in terms of the outage probability for the secondary network, the secrecy outage probability, and the probability of non-zero secrecy capacity for the primary network. Numerical results are provided to verify the correctness of the proposed analytical framework.

In this article, we investigate a spectral and energy-efficient wireless body area network (WBAN) for smart healthcare applications. Herein, we primarily focus on improving the spectrum utilization by intelligently sharing spectrum resources through cognitive radio (CR) technology, allowing various sensor nodes in the underlying network to co-exist without compromising on their quality-of-service (QoS). We prioritize the sensor nodes based on their applications (medical/non-medical) and thereby categorize them into primary and secondary users to implement an on-body CR-WBAN. Furthermore, two energy harvesting (EH) protocols namely time-switching cooperation (TSC) and power-splitting cooperation (PSC) are employed to facilitate the secondary node cooperation with the primary network in return for spectrum access. For both the primary and secondary networks, we derive useful expressions for the outage probability. To provide more insights into the proposed CR-WBAN, the throughput and energy efficiency performances assuming a delay-limited scenario are investigated. The impact of key parameters are demonstrated to provide guidelines for the practical design of spectral and energy-efficient WBANs. The accuracy of our proposed analytical framework is verified through Monte Carlo simulations.

The present work investigates the physical layer security of wireless communication systems over non-homogeneous fading environments, i.e., $\eta$ η - $\mu$ μ and $\lambda$ λ - $\mu$ μ fading models, which are typically encountered in realistic wireless transmission scenarios in the context of conventional and emerging communication systems. This study considers a single-input multiple-output system that consists of a single-antenna transmitter, a multi-antenna legitimate receiver, and an active multi-antenna eavesdropper. To this end, novel exact analytical expressions are derived for the corresponding average secrecy capacity and secrecy outage probability, which are corroborated by respective results from computer simulations. Capitalizing on the offered results, the physical layer security is quantified in terms of different parameters, which leads to useful insights on the impact of non-homogeneous fading environment and the number of employed antennas on the achieved physical layer security levels of the underlying system configuration. The offered results and insights are useful for the design of such systems as well as for the computational requirements and sustainability relating to such systems, since emerging communications are largely characterized by stringent quality of service and complexity requirements.

This study investigates the performance of a cooperative non-orthogonal multiple access cognitive network with imperfect successive interference cancellation under Rayleigh fading conditions. Specifically, the authors consider an underlay cognitive network that consists of a primary transmitter–receiver pair and a secondary system where a source node communicates with two destinations nodes directly and indirectly through a relay node selected from a set of decode-and-forward relays. A partial relay selection scheme is used to determine the best relay. The authors present an analytical framework, with closed-form analytical expressions for the outage probabilities at the two destinations as well the primary destination. Moreover, to simplify the analysis and to provide further insights into the impact of key system parameters, asymptotic studies of the outage probabilities were carried out. To this end, the authors focus on two cases: (i) the maximum allowable transmit power of the secondary network grows sufficiently large and (ii) the interference power approaches infinity. Finally, Monte Carlo simulations are provided in an effort to assess the accuracy of the proposed mathematical framework.

This correspondence focuses on the analysis of average symbol error rate (ASER) of $M$ -ary phase-shift keying (MPSK) over $\boldsymbol {\kappa }$ - $\boldsymbol {\mu }$ , $ \boldsymbol {\eta }$ - $ \boldsymbol {\mu }$ , and $\boldsymbol {\alpha }$ - $\boldsymbol {\mu }$ fading channels subject to imperfect carrier phase recovery. The random phase noise is considered to be Tikhonov (or von Mises) distributed. Specifically, exact expressions for the ASER i) under non-fading scenario, ii) under $\boldsymbol {\kappa }$ - $\boldsymbol {\mu }$ , iii) $ \boldsymbol {\eta }$ - $ \boldsymbol {\mu }$ , and iv) $\boldsymbol {\alpha }$ - $\boldsymbol {\mu }$ fading channels, as well as v) their corresponding asymptotic behavior for high signal-to-noise ratio, (SNR) values are analytically obtained and evaluated. The derived expressions support arbitrary values of the fading parameters, namely $\boldsymbol {\alpha }$ , $ \boldsymbol {\kappa }$ , $\boldsymbol {\eta }$ and $ \boldsymbol {\mu }$ , and they are validated by reducing them to particular cases, for which results are available in the literature, and by means of simulations. Several important conclusions concerning the system performance as a function of the channel parameters and loop SNR are drawn.

In this paper, we propose a relay-assisted device-to-device (D2D) communication as an underlay in a cellular network, where two sequential best relay nodes based on different selection criteria are chosen. Novel analytical expressions of the secrecy outage probability (SOP) and the probability of nonzero secrecy capacity (PNSC) are derived to evaluate the secrecy performance of the cellular network. In addition, we derive a simple and explicit approximation of the SOP in the high signal-to-noise ratio (SNR) to gain some insights on how various system parameters affect the aforementioned secrecy performance. Also, for the sake of comparison, the analytical SOP expression when only the cellular network exists, i.e., without the interference of the D2D communication, is obtained. Furthermore, to assess the usefulness of the cooperation between the D2D communication and the cellular network, we derive an analytical expression for the mutual outage probability (MOP) which represents the true outage probability across both the cellular and D2D networks. An asymptotic analysis of the MOP in the high SNR regime is obtained and the diversity order is derived. Finally, our proposed mathematical framework is compared with Monte-Carlo simulations to verify the accuracy of the derivations.

In this article, we investigate the performance of a piece-wise linear model of energy harvesting-based multiuser overlay spectrum sharing system. Herein, an energy-constrained secondary node acts as a cooperative relay to assist the information transmission between a primary transmitter and multiple primary receivers. In return for the cooperation, the secondary node enjoys access to the primary user’s spectrum for its own information transfer. Specifically, by employing a time-switching based receiver, the secondary node harvests energy from the received radio-frequency signal of primary transmitter during a dedicated energy harvesting phase. In the subsequent information transfer phase, the secondary node splits the harvested power to forward the primary data as well as its own information intended for another secondary user. We analyze the impact of decoding primary’s information at the secondary receiver on the performance of secondary network. Importantly, we propose an improved energy harvesting-based relaying scheme which makes an efficient use of available degrees of freedom and thereby enhances the performance of both primary and secondary networks significantly. For this analytical framework, we derive the expressions of outage probability for primary and secondary networks. Numerical and simulation results are obtained to extract various useful insights and to validate our theoretical developments.

This paper aims to propose and analyze an energy-and spectrum-efficient wireless body area network (WBAN) for smart healthcare applications. On one hand, we focus on improving the spectrum utilization in WBANs by incorporating an overlay cognitive radio (CR) paradigm that allows the co-existence of various sensor nodes as primary and secondary users based on their applications i.e., medical or non-medical. On the other hand, we employ an energy harvesting (EH) based time-switching cooperation protocol through the secondary device to improve energy efficiency. We evaluate the performance of the proposed overlay CR WBAN in terms of outage probability, throughput and energy efficiency, and thereby provide practical design guidelines in IoT-based e-healthcare framework. Above all, we assess the correctness of the proposed analytical framework when compared to Monte Carlo simulations.

This paper investigates the secrecy performance of multiple-input multiple-output systems under generalized $\alpha -\mu $ fading conditions. To this end, we focus on two distinct scenarios: 1) the transmitter has knowledge of the channel state information (CSI) of the eavesdropper channel and 2) the transmitter is not aware of the CSI of the wiretap link. By considering transmit antenna selection in the underlying system, we develop closed-form analytical expressions for the lower bound of the secrecy outage probability (SOP) and the probability of the strictly positive secrecy capacity. Furthermore, two novel approaches are proposed to derive an analytical expression of the average secrecy capacity (ASC). First, the ASC is expressed as a function of the average capacity of the desired link and an interaction term regarded as the ASC loss. Second, the ASC is expressed in terms of the average capacities of the desired and eavesdropper links, plus an interaction term that can be regarded as some sort of ASC gain due to the statistical independence between the desired and eavesdropper links. In addition, asymptotic studies of the SOP and the ASC at high signal-to-noise ratio are carried out, which precisely reveal the secrecy diversity and array gains.

In this paper, we investigate the performance of a relay selection scheme in a buffer-aided multi-relay network with coded transmissions. We consider: 1) two different coding schemes, i.e., Turbo codes and distributed Turbo codes (DTC) and 2) quasi-static Rayleigh fading channels, where all the links are independent but asymmetric. For each of the aforementioned schemes, we analyze the performance of the system in terms of the average throughput and average delay. In addition, simple and explicit approximations of the asymptotic throughput for infinite buffer size and the high signal-to-noise ratio (SNR) regime are obtained. Our analysis of the asymptotic throughput provides the maximum achievable diversity gain of the system, and the accuracy of the derived analytical framework is assessed when compared to the Monte-Carlo simulations.

In this letter, we study the performance of digital communication systems considering the general and versatile α-η-κ-μ fading model, which was recently proposed in the literature. To this end, novel and exact expressions for the outage probability, average channel capacity, and average error rate of a variety of modulation formats are derived for arbitrary values of the fading parameters. Moreover, an asymptotic outage analysis is carried out in order to get further insight as to how the fading parameters impact system performance. Monte Carlo simulations are provided to validate the proposed analytical framework.

The impact of outdated channel state information on two sequential relay selection schemes for device-to-device underlaid cellular networks over mixed fading channels is investigated. To this end, the mutual outage probability (MOP) is analyzed in which an easy-to-evaluate analytical expression for the MOP is derived. Moreover, an asymptotic analysis of the MOP at high signal-to-noise ratio is provided, and the diversity order is evaluated.

In this letter, the performance of digital communications systems over $\alpha $ - $\kappa $ - $\mu $ fading channels is analyzed in terms of outage probability, average channel capacity, and average error rate for a variety of modulation formats. To this end, novel and exact expressions for the aforementioned performance metrics are derived, based on which an asymptotic analysis is carried out. The derived expressions are valid for arbitrary values of the fading parameters, namely $\alpha $ , $\kappa $ , and $\mu $ , and their accuracies are validated through Monte Carlo simulations.

In this correspondence, the physical layer security of wireless systems under generalized $\boldsymbol {\alpha }$ - $\boldsymbol {\kappa }$ - $\boldsymbol {\mu }$ and $\boldsymbol {\alpha }$ - $\boldsymbol {\eta }$ - $\boldsymbol {\mu }$ fading with arbitrary fading parameters is analyzed in terms of the secrecy outage probability (SOP). To this end, novel analytical expressions for the lower bound of the SOP are derived. Moreover, an asymptotic secrecy analysis is investigated for each corresponding SOP to get the secrecy diversity gain. Monte Carlo simulations are provided to assess the accuracy of the proposed analytical framework.

In this paper, the performance of a digital communication system subject to $\kappa-\mu$ Extreme fading conditions is investigated. Specifically, exact and novel analytical expressions for the normalized average channel capacity and average error rate are derived assuming arbitrary fading parameters. An asymptotic error analysis is also performed in order to get further insights for the system performance. Finally, our analytical results are corroborated through Monte Carlo simulations. Although the derived expressions of the exact performance metrics include an infinite series, it is worth noting that they all converge rapidly and steadily after a few terms. In light of this, a truncation error analysis on one of the underlying performance metrics under investigation is provided and it is shown that the relative error is less or equal to 0.001% for as many as 10 terms.

In this paper, we consider an overlay cognitive satellite-terrestrial relay network comprising a primary satellite source-receiver pair and a secondary transmitter-receiver pair on the ground while taking into account the practical relay transceiver hardware impairments. Herein, a primary satellite source communicates with its terrestrial user by utilizing both direct and relay links, using an amplify-and-forward based cooperative communication technique. Considering distortion noises in relay signal processing, we obtain new closed-form expressions for the outage probability of primary satellite network and secondary terrestrial network and explicitly derive the asymptotic outage behaviour for primary network by adopting pertinent heterogeneous fading models. Both primary and secondary networks satisfy their quality-of-service criteria for the low data rate requirements only. However, for the high data rate requirements, a ceiling effect is shown to occur which eventually makes the spectrum sharing infeasible.

We introduce the {\alpha}-{\kappa}-{\mu} shadowed ({\alpha}-KMS) fading distribution as a natural generalization of the versatile {\alpha}-{\kappa}-{\mu} and {\alpha}-{\eta}-{\mu} distributions. The {\alpha}-KMS fading distribution unifies a wide set of fading distributions, as it includes the {\alpha}-{\kappa}-{\mu}, {\alpha}- {\eta}-{\mu}, {\alpha}-{\mu}, Weibull, {\kappa}-{\mu} shadowed, Rician shadowed, {\kappa}-{\mu} and {\eta}- {\mu} distributions as special cases, together with classical models like Rice, Nakagami-m, Hoyt, Rayleigh and one-sided Gaussian. Notably, the {\alpha}-KMS distribution reduces to a finite mixture of {\alpha}-{\mu} distributions when the fading parameters {\mu} and m take positive integer values, so that performance analysis over {\alpha}-KMS fading channels can be tackled by leveraging previous (existing) results in the literature for the simpler {\alpha}-{\mu} case. As application examples, important performance metrics like the outage probability and average channel capacity are analyzed., Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible

In this letter, the secrecy performance of single-input multiple-output systems over the generalized $\kappa$ – $\mu$ fading channels is analyzed. Novel expressions for the average secrecy capacity and the secure outage probability (SOP) are derived. Moreover, simple and explicit expressions of the asymptotic SOP at high signal-to-noise ratio are given in an effort to gain some valuable insights on how various system parameters affect the secrecy performance. The proposed mathematical analysis is compared with Monte–Carlo simulation to verify the accuracy of the derivation.

Since the radio-frequency spectrum is fast becoming scarce, increasing the spectral utilization is of utmost importance for the sustainable development of wireless communications systems. In an effort to improve the spectral efficiency, cooperative relaying techniques have recently been integrated into spectrum-sharing environments. In this paper, we examine the outage and bit error probabilities of dual-hop cognitive turbo-coded cooperative networks with outdated channel state information (CSI) subject to Rayleigh fading. We assume a spectrum-sharing environment where the transmit power conditions of the underlay network are governed by the combined power constraint of the interference in the primary network and the maximum allowable transmission power at the secondary network. In this network, cochannel interference from the primary transmitter on the secondary network is considered, and a single relay that maximizes the received signal-to-noise ratio (SNR) is selected among the secondary relays. To efficiently evaluate the key parameters on the system performance, we derive the analytical expressions of the end-to-end outage probability and bit error rate (BER) for the proposed scheme. Assuming binary phase-shift keying (BPSK), we obtain explicit upper bounds on the probability of bit error based on the pairwise error probability. Furthermore, we present simplified expressions of the outage probability in the high-SNR regime used to quantify the system performance in terms of diversity gain. Finally, simulation results are provided to verify the accuracy of our analytical framework.

In this paper, the concept of wireless power transfer and wireless information transmission, which have recently received special attention for improving energy efficiency in wireless communication systems, are investigated. In particular, we focus on a cooperative communication network consisting of a source node, an energy-constrained relay node and a destination node. In contrast to conventional wireless-powered cooperative networks, a GFDM waveform-which is an emerging candidate waveform for the 5G mobile networks and beyond-is considered. The performance of the proposed GFDM-based relaying network with energy harvesting is studied in terms of the average BER for the general M-QAM constellation set. Numerical and simulation results are provided to give useful insights and to assess the accuracy of our mathematical derivations. Post-print / Final draft

Two sequential relay selection strategies are investigated for a cooperative relay-assisted device-to-device (D2D) communication underlaying cellular network over mixed fading channels. The relay selection schemes aim to improve the D2D communication performance and the wireless physical layer security of the cellular network. In this paper, the study is conducted analytically by obtaining an expression for the secrecy outage probability (SOP) of the cellular network. Moreover, in an effort to assess the usefulness of the cooperation between the two networks, an expression for the mutual outage probability (MOP)â€"which represents the true outage probability across both the D2D and cellular networksâ€"is derived. Also, an asymptotic analysis of the MOP in the high signal-to-noise ratio regime is obtained and the diversity order is evaluated. Monte-Carlo simulations are provided to validate the accuracy of our proposed analytical framework.

The present work investigates an energy harvesting (EH)-based cognitive massive multiple-input multiple-output (MIMO) and multi-relay assisted network with underlay spectrum sharing. This study considers a secondary network which is allowed to opportunistically access the licensed spectrum band of the primary network, as long as the intra-cell interference imposed on the primary base station due to concurrent secondary network transmissions, does not exceed a pre-defined interference temperature. To this end, analytical expressions of the signal-to-interference-plus-noise (SINR) ratio and the asymptotic achievable sum rate are obtained. Capitalizing on the offered results, the trade-off between the achievable sum rate of the network and the harvested energy on the back of relay selection, is quantified. Monte Carlo simulations are provided to demonstrate the correctness of the proposed mathematical derivations.

In this paper, the error performance of binary and quaternary phase-shift keying signals with imperfect carrier phase recovery is investigated assuming a flat slow i±-i fading channel and the presence of thermal noise. The phase noise is considered to be Tikhonov and Gaussian distributed. More specifically, an analytical expression for the exact average bit error rate is obtained, as well as its corresponding asymptotic expression for large signal-to-noise ratio (SNR) values. The derived expressions are valid for arbitrary values of the fading parameters, namely i± and i, and they are validated through Monte Carlo simulations. Several important conclusions concerning the system performance as a function of the channel parameters, namely, non-linearity, clustering, and loop SNR, are drawn.

This paper investigates the secrecy performance of a multiple-input multiple-output (MIMO) system with transmit antenna selection (TAS) and maximal-ratio combining (MRC) over generalized α-µ fading. In the underlying wireless communication system, a single antenna is selected to transmit confidential messages to a multi-antenna receiver in the presence of a passive multi-antenna eavesdropper. In our analysis, new closed-form expressions are obtained for the secrecy outage probability (SOP) and the probability of strictly positive secrecy capacity (SPSC), and are subsequently corroborated through Monte Carlo simulations to assess their validity. Moreover, asymptotic studies of the secrecy outage probability are derived and explicitly show the effects of various system parameters on the secrecy diversity gain.

The present work investigates the physical layer security of wireless communication systems over non-homogeneous fading environments, which are typically encountered in realistic wireless transmission scenarios in the context of conventional and emerging communication systems. This is carried out in the context of a single-input multiple-output system that consists of a single-antenna transmitter, a multi-antenna legitimate receiver, and a multi-antenna active eavesdropper. To this end, novel exact analytic expressions are derived for the corresponding average secrecy capacity, which are corroborated by respective results from computer simulations that verify their validity. Capitalizing on the offered results, the physical layer security is quantified in terms of different parameters. This leads to the development of useful insights on the impact of non-homogeneous fading environment and the number of employed antennas on the achieved physical layer security levels of the considered set up. acceptedVersion

Recently, cooperative relaying techniques have been integrated into spectrum-sharing systems in an effort to yield higher spectral efficiency. Many investigations on such systems have assumed that the channel state information between the secondary transmitter and primary receiver used to calculate the maximum allowable transmit secondary user transmit power to limit the interference is known to be perfect. However, because of feedback delay from the primary receiver or the time-varying properties of the channel, the channel information may be outdated, which is an important scenario to cognitive radio systems. In this paper, we investigate the impact of outdated channel state information for relay selection on the performance of partial relay selection with amplify and forward in underlay spectrum-sharing systems. We begin by deriving a closed-form expression for the outage probability of the secondary network in a Rayleigh fading channel along with peak received interference power constraint and maximum allowable secondary user transmit power. We also provide a closed-form expression for the average bit-error rate of the underlying system. Moreover, we present asymptotic expressions for both the outage probability and average bit-error rate in the high signal-to-noise ratio regime that reveal practical insights on the achievable diversity gain. Finally, we confirm our results through comparisons with computer simulations. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, we analyze the performance of the generalized selection combining with Gaussian distributed weighting errors for physical-layer security of a wireless communication system. Exact closed-form expressions for the secrecy performance in terms of the secrecy outage probability and the probability of non-zero secrecy capacity are derived. Moreover, asymptotic expressions are obtained and provide insights on how the channel parameters affect the secrecy performance. Monte-Carlo simulations are conducted to assess the accuracy of our analytical framework.

In this paper, we investigate the physical-layer (PHY) security problem of a wireless communication system over mixed generalized fading channels. We consider the transmission of confidential information between a transmitter and a legitimate receiver over an α-μ fading channel in the presence of an eavesdropper who is subject to κ-μ fading. Both the α-μ and κ-μ distributions have been considered in the literature to model the generalized small-scale fading and such a mixed fading propagation environment can be encountered in practical systems where one channel is described for its non-linearity and clustering properties whereas the other has a line-of-sight (LOS) component. In particular, novel analytical expressions for the exact and asymptotic average secrecy capacity (ASC) are derived. Finally, Monte-Carlo simulations are performed to assess the accuracy of the proposed mathematical analysis.

In this paper, the performance for physical-layer (PHY) security of a wireless communication system in mixed α-μ and κ-μ fading channels is analyzed. The system under consideration consists of a transmitter and a legitimate receiver in the presence of an eavesdropper, wherein the main channel is subject to α -μ fading while the wiretap channel undergoes κ-μ fading. We assume that the legitimate users and the eavesdropper are equipped with a single antenna. We derive a novel analytical expression for the lower bound of secure outage probability (SOP). Next, we investigate the asymptotic behavior of the SOP for high signal-to-noise ratio (SNR) of the main channel. Finally, we provide Monte-Carlo simulations to verify our proposed analytical framework.

This paper provides an analytical study on the bit-error rate (BER) of the turbo-coded cooperative relaying in spectrum-sharing systems subject to Rayleigh fading. It is assumed that a single relay that maximizes the received signal- to-noise ratio (SNR) is selected in a secondary multi-relay network. We consider that the transmit power conditions of the underlay system is controlled by the joint power constraint of the interference in the primary network and the maximum allowable transmission power at the secondary network. Moreover, the proposed scheme takes into account the effect of primary user (PU) interference on the neighboring secondary network. First, we derive an expression of a tight upper bound for the BER of the secondary network. Then, we investigate the cooperative diversity gain of the underlying scheme. Finally, the proposed analysis is validated by Monte-Carlo simulations.

In this paper, we consider relay selection for turbo coded cooperative networks subject to Nakagami-m fading when the channel state information (CSI) is known at the receiver but is not necessarily ideal. This non-ideality may be due to a feedback delay caused by the difference between the instantaneous CSI during the transmission and the CSI at the time of relay selection, resulting in outdated CSI phenomena. The impact of the outdated CSI on the proposed scheme is well investigated. A closed-form expression for the exact outage probability is derived as well as its asymptotic expression in the high signal-to-noise (SNR) regime. Moreover, upper bounds on the bit-error rate (BER) are presented and a study of the diversity order reveals that for ideal CSI, full diversity in the number of relays and fading parameters m is achieved as opposed to outdated CSI where the achievable diversity is equivalent to the diversity of a coded cooperative network with a single relay.

This paper studies a multi-relay adaptive turbo-coded cooperative diversity scheme over Nakagami- m fading channels. In the underlying scheme, after receiving a fraction of the codeword determined by a tradeoff parameter denoted by f, all the relays decode, and only the reliable relays forward the rest of the codeword to the destination. We assume binary phase-shift keying modulation and analyze the scheme under study in terms of bit error rate (BER) and outage probability. Union bounds on the BER are derived using the transfer function bounding and the limit-before-average techniques. Furthermore, we examine the asymptotic behavior of the system in the high-signal-to-noise-ratio (SNR) regime using the derived pairwise error probability (PEP). We also derive a closed-form expression for the outage probability of the system and its high-SNR approximation to evaluate the achievable diversity order. Simulations are provided to assess the accuracy of our analytical work.

This paper presents an analytical study on the outage probability (OP) of cognitive amplify-and-forward (AF) with underlay spectrum-sharing systems subject to Rayleigh fading. In the underlying scheme, we consider a partial relay selection with outdated channel state information (CSI) and a spectrum-sharing system where the transmit power conditions are controlled by the combined interference power in the primary network and the maximum allowable transmission power at the secondary network. We first derive the end-to-end OP in closed form and then present asymptotic analysis for the high signal-to-noise ratio (SNR). Finally, Monte-Carlo simulations are provided to verify the accuracy of the theoretical analysis.

In this paper, we study the outage probability of the amplify-and-forward (AF) cognitive relaying in spectrumsharing environments with outdated channel state information (CSI) over Rayleigh fading channels. A selection of the best relay in the secondary system with outdated channel information is considered. We derive a closed-form expression for the tight lower bound on the end-to-end outage probability using the cumulative density function (CDF) approach. Furthermore, the asymptotic behavior of the outage performance is investigated and reveals the diversity order of the underlying scheme. Finally Monte-Carlo simulations are provided to verify the analytical framework.

In this paper, the best relay selection in CSI-assisted variable gain amplify-and-forward (AF) with outdated channel state information (CSI) in the presence of co-channel interference (CCI) over Rayleigh fading channels is investigated. We first derive the cumulative density function (CDF) of the effective signal-to-interference-plus-noise ratio (SINR) of both the best source-to-relay and relay-to-destination links. Subsequently, a closed-form expression for the lower bound on the end-to-end outage probability (OP) of the system under study is obtained. Moreover, we present and discuss asymptotic expressions of the OP, which reveal the diversity gain of the underlying system. In particular, it is shown that for varying interference-to-noise ratio (INR), the diversity order is reduced to zero regardless of the nature of the desired CSI (i.e., outdated or ideal), and to full diversity or diversity one for fixed INR with ideal CSI or outdated CSI, respectively. Finally, Monte-Carlo simulation results are presented to validate the accuracy of the proposed analytical framework.

In this paper, we consider a cognitive radio network (CRN) with multiple primary users (PUs) and multiple SUs and propose a cooperative spectrum sensing and transmission for some selected SUs in order to avoid interference with PUs. The distributed collaboration strategy is done through a coalitional game and we present a distributed algorithm for the coalition formation. In the proposed scheme, the SUs that sense a particular channel with non-identical sensing times, form a coalition in which a coalition head is selected to determine whether or not the channel is idle. If a channel is not active, then the SU chosen as coalition head can transmit its packets through a cooperative scheme in the data transmission slot. Our simulation results show that the proposed scheme can significantly improve the average throughput compared to its non-cooperative counterpart. Moreover, it is shown that the proposed scheme is energy efficient in comparison to a scheme with fixed and identical sensing times.

Cooperation with channel coding also known as coded cooperation has been shown to be an efficient scheme for providing significant performance gains. However, relay selection in coded cooperation systems is seldom available in the existing literature. It is widely known that relay selection schemes in cooperative communications are dependent on the quality of the channel state information (CSI). In this paper, we study the impact of using outdated channel state information (CSI) for opportunistic relay selection (ORS) in turbo-coded cooperation over Rayleigh fading channels. A closed-form expression for the exact outage probability as a function of the correlation between the actual and delayed or outdated CSI is derived. Furthermore, diversity analysis is presented and it is noted that the diversity order is reduced to two regardless of the number of available relays, when the correlation factor is not equal to unity.

We study the performance of distributed turbo-coded cooperative networks with multiple dual-hop relays over both identical and non-identical Nakagami-m slow fading channels. All the relays are equipped with error detection capabilities and only the reliable relays retransmit to the destination. In this paper, we derive the union bounds on the bit-error rate (BER) of the proposed scheme using the transfer function bounding and the limit-before-average techniques. Moreover, through the derived pairwise-error probability (PEP), we analyze the asymptotic behavior of this system at high signal-to-noise ratio (SNR). It is noted that the achievable diversity order depends on the number of cooperating relays and the fading parameters. Finally, performance evaluation of the proposed scheme is presented via error bounds and Monte Carlo simulations.