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Neighbourhood area network (NAN) performance is analyzed with space shift keying (SSK) modulation and energy harvesting-based cooperative amplify-and-forward (AF) relaying. Wifi-enabled home appliances (HAs) can transfer the information to the utility control centre through the smart meter (SM) in the NAN. The HAs in NAN work on a power-saving mechanism, and they drastically increase the spectral efficiency. The Markov chain dynamically models the number of active HAs in the smart grid (SG) network. Moreover, simultaneous wireless information and power transfer combined with AF relaying-based SM helps overcome the rising demands of SG communication by providing an enhanced data rate, low latency, shorter coverage, widespread connectivity of the massive number of devices along with energy-efficiency. Mathematical expressions for average bit error probability are derived for NAN over mixed Saleh–Valenzuela and Rician fading channel based on the multi-user selection combination. The Monte Carlo simulation verifies the numerical results. The result illustrates that the SG NAN performance can be improved by combining SSK modulation with energy harvesting schemes. [ABSTRACT FROM AUTHOR]

Previous works only focus on the optimization design for the dual-hop cooperative ambient backscatter communication (AmBC) system with single-relay selection. The impact of relay selection on the outage performance of dual-hop cooperative AmBC systems is still missing. Motivated by this, in this paper, we investigate the outage performance of a dual-hop cooperative AmBC system with single-relay selection, where the backscatter link shares the receiver with the cellular link and the harmful direct-link interference (DLI) is mitigated by using successive interference cancellation (SIC). In the system considered, the selected relay has dual functions. One is to forward message for the cellular link, and the other is to act as the radio-frequency (RF) source for the backscatter device (BD). Specifically, after proposing two novel single-relay selection schemes (RSSs), namely reactive RSS and proactive RSS, we derive the closed-form outage probability (OP) expressions for both RSSs, which can be performed in a distributed manner. To gain more insights, the asymptotic OPs at high signal-to-noise ratio (SNR) are explored and the outage performance comparison between the reactive RSS and proactive RSS are also provided. Results show that the proposed reactive RSS is outage-optimal among all possible single-relay selection schemes. The theoretical analysis is validated by Monte Carlo simulations. The results also show that the relay selection scheme, the number of relays, the location of BD, and the reflection coefficient of BD have great impact on the outage performance of cooperative AmBC systems. [ABSTRACT FROM AUTHOR]

Relay-assisted wireless communications, where both the relay and the final destiny employ diversity-combining techniques, represent a compelling strategy for improving the signal-to-noise ratio (SNR) for mobile terminals, mainly at millimeter-wave (mmWave) frequency bands. In this sense, this work considers a wireless network that employs a dual-hop decode-and-forward (DF) relaying protocol, in which the receivers at the relay and at the base station (BS) use an antenna array. Moreover, it is considered that the received signals are combined at reception using equal-gain-combining (EGC). Recent works have enthusiastically employed the Weibull distribution so as to emulate the small-scale fading behavior in mmWave frequencies, which also motivates its use in the present work. For this scenario, exact and asymptotic expressions for the system's outage probability (OP) and average bit error probability (ABEP) are derived in closed form. Useful insights are gained from these expressions. More precisely, they illustrate how the system and fading parameters affect the performance of the DF-EGC system. Monte Carlo simulations corroborate the accuracy and validity of the derived expressions. Furthermore, the mean achievable rate of the considered system is also evaluated via simulations. Useful insights regarding the system performance are obtained from these numerical results. [ABSTRACT FROM AUTHOR]

Massive device-to-device communication nodes and Internet of Things (IoT) devices are expected to be crucial components in next-generation wireless networks. However, the energy constraint of these nodes presents a challenge since the energy of the batteries is limited. Motivated by this, radio frequency energy harvesting (EH) has been developed as an efficient strategy to overcome the energy constraint of IoT devices and sensor networks. In this paper, a wireless-powered dual-hop amplify-and-forward relaying system, in the absence of a direct link between the source (S) and the destination (D), is considered. It is assumed that a dedicated power beacon (PB) transmits an energy-bearing signal from which the power-constrained S and relay (R) harvest energy. Theoretical derivations of bit error probability, outage probability, and throughput expressions are performed for both linear and non-linear energy harvesting models. Moreover, the theoretical results provided for different system parameters are validated via Monte Carlo simulations. The obtained results reveal the difference between the realistic non-linear EH model and the conventional linear EH model, which overestimates the system performance at high levels of harvested energy. Thus, it leads to misunderstanding the real performance of the EH systems. However, at low levels of harvested energy, both models behave similarly and provide realistic results. [ABSTRACT FROM AUTHOR]

A dual-hop home area network (HAN) with energy harvesting over mixed fading has been proposed for smart grid (SG) communication. Radio-frequency (RF) and Terahertz (THz) channels with amplify-and-forward (AF) and decode-and-forward (DF) relays are the two cases taken into consideration. The Markov chain with multi-user selection combining is used to model the active home appliances. The appliances use RF links for exchanging information with the smart meter (SM). The SM harvests energy from RF signals to transmit data to the control unit through a THz link. The RF and THz links are considered the Saleh-Valenzuela (S-V) and the α − μ distributions, respectively. Here, the space shift keying (SSK) modulation scheme is considered for transferring information from the home appliances to the SM. Closed-form mathematical expressions for average bit error probability (ABEP) are derived for performance analysis. The effects of the energy harvesting time factor, the number of appliances present, the intensity of traffic, and the severity of fading are shown by numerical and Monte Carlo simulation results in the SG communication system. [ABSTRACT FROM AUTHOR]

Recently, non-orthogonal multiple access (NOMA) and energy harvesting (EH) from radio frequency (RF) have been considered as promising candidates for next-generation mobile communications. In this paper, we investigate a novel solution to enhance the reliability and the supply stability of a downlink NOMA relaying networks, in which we integrate two techniques: (i) simultaneous wireless information and power transfer, i.e. the relay node can harvest the energy from source signals and use this energy to help forward information from source node to two user nodes; and (ii) data buffer aid at relay node, i.e. the data packets received from the source can be stored in a buffer and then be re-transmitted to the destination nodes only when the channel condition is good. The performance of the proposed system is analyzed rigorously to derive the system outage probability (OP), throughput and the average packet delay. Furthermore, a power allocation optimization problem to minimize the OP is formulated and solution to this problem is also provided. In addition, the optimal transmission rates to maximize the throughput of each user are presented in numerical results. Monte Carlo simulations are conducted to verify the analytical results, which confirms that with data buffer at relay, the overall outage probability (OOP) can be reduced significantly. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a new framework for low-outage downlink non-orthogonal multiple access (NOMA) using a coordinated direct and relay transmission (CDRT) scheme with direct links to both the near-user (NU) and the far-user (FU). Both amplify-and-forward and decode-and-forward relays are considered. In this framework, the NU combines the signals from base-station and relay at each stage of the successive interference cancellation (SIC) to attain good outage performance. For both NU and FU, the expressions for outage probability and throughput are derived in closed form. We also derive the high-SNR expressions for the outage probability to demonstrate that with the proposed framework, both users harness a diversity of two without feedback bits (this is the only framework to achieve this). We demonstrate that the choice of power allocation coefficient and target symbol rates is crucial to maximizing the NU throughput while ensuring a desired target FU throughput. We demonstrate that CDRT with the proposed framework outperforms known schemes in terms of outage probability, sum throughput, and energy efficiency. Moreover, we also show that optimal rate selection is important to maximize the energy efficiency. Monte Carlo simulations validate the accuracy of the derived analytical expressions. [ABSTRACT FROM AUTHOR]

Cooperative communication is a key factor in 5G and beyond standards for increasing the quality of service and aids for dense networks. It works in conjugate with non-orthogonal multiple access (NOMA) to increase the connectivity and spectral efficiency. In this paper, a novel minimum variance maximum mean relay selection scheme with fixed power allocation (MVMM-FPA) is proposed for two-stage cooperative NOMA (C-NOMA) networks using decode-and-forward protocol. The outage probability analytical expressions are derived for the MVMM-FPA over Rayleigh fading channel and its performance is observed with the conventional relay selection (RS) schemes. The impact of outage performance on target rate for users and number of relays have been analyzed for the proposed scheme. Monte Carlo simulations are used to corroborate the analytical expressions of outage probability. Simulation results reveal that the MVMM-FPA RS scheme for C-NOMA offers a minimal outage probability than existing max–min RS and orthogonal multiple access schemes without sacrificing the spectral efficiency. [ABSTRACT FROM AUTHOR]

In this work, we provide a framework analysis of dual-hop hybrid Millimeter Wave Radio Frequency (RF)/Free Space Optical (FSO) MIMO relaying system. The source is equipped with multiple antennas and employs conjugate beamforming while the destination consists of multiple apertures with selection combining. The system also consists of a relay operating at amplify-and-forward mode. The RF channels are subject to Nakagami-m fading while the optical links experience the Málaga distribution. In addition, we introduce the impairments to the relay and receiver. In fact, the relay is impaired by the High Power Amplifier (HPA) nonlinearities while the receiver suffers from the In phase and Quadrature Imbalance. Moreover, we assume two types of HPA nonlinearities impairments called Soft Envelope Limiter (SEL) and Traveling Wave Tube Amplifier (TWTA). Closed-forms of the outage probability, the bit error probability, and the ergodic capacity are derived. Capitalizing on these performances, we derive the high SNR asymptotes to unpack insightful metrics such as the diversity gain. We also address the impacts of some key factors on the system performance such as the impairments, the interferers, the number of antennas and apertures and the pointing errors, etc. Finally, the analytical expressions are confirmed by Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

This paper studies a new decode-and-forward cooperative overlay cognitive radio non-orthogonal multiple access (DFCO-NOMA) system, where a secondary network shares the license spectrum of a primary network by using NOMA principles. Asymptotic expressions for the outage probability in high signal-to-noise ratio regime of both secondary and primary destinations are derived assuming channel estimation error (CEE) and imperfect successive interference cancellation. The diversity order for the primary and secondary symbols are also derived. Further, the optimal power allocation coefficients to maximize the system throughput are determined to ensure priority to the primary network. The paper also investigates the impact of various parameters such as power allocation coefficients, CEE, and detection threshold, on the outage performance of the proposed system. The accuracy of derived analytical results are verified through the Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

In this paper, the one-way decode-and-forward (DF) full-duplex relaying network system with presence of direct link is investigated. In the analysis section, we derived the exact, lower, and upper bound for outage probability (OP) with maximal ratio combining (MRC) at the receiver. Furthermore, the system performance's analytical expressions are verified by using the Monte Carlo simulation. In addition, we investigated the effect of the main parameters on the OP of the proposed system. Finally, we can sate that the simulation curves overlap the analytical curves to convince the analysis section. This research can provide a novel recommendation for the communication network. [ABSTRACT FROM AUTHOR]

This paper investigates the decode-and-forward (DF) full-duplex (FD) relaying system under the presence of an eavesdropper. Moreover, the relay node is able to harvest energy from a transmitter, and then it uses the harvested energy for conveying information to the receiver. Besides, both two-hop and direct relaying links are taking into consideration. In the mathematical analysis, we derived the exact expressions for intercept probability and outage probability (OP) by applying maximal ratio combining (MRC) and selection combining (SC) techniques at the receiver. Next, the Monte Carlo simulation is performed to validate the mathematical analysis. The results show that the simulation curves match the mathematic expressions, which confirms the analysis section. [ABSTRACT FROM AUTHOR]

In this work, a non-orthogonal multiple access (NOMA) based transmission between a source and two end users is examined over slow Generalized-K distributed (GKD) fading channels, where a single relay using decode-and-forward (DF) protocol is selected out of a set of full-duplex/half-duplex (FD/HD) multiple relays with the quality of service requirements. Two stage relay selection (RS), selecting a relay out of a set of relays providing service quality for user 1 to maximize data rate of user 2, is analyzed. Additionally, not only perfect successive interference cancellation (pSIC) but also imperfect SIC (ipSIC) is considered. Self-interference (SI) and ipSIC are assumed to be Nakagami-m distributed, additionally, Gaussian and channel gain dependent modelling of ipSIC are also considered. A new expression for cumulative distribution function (CDF) of GKD is provided, thereafter, robust approximated probability density function (PDF) and CDF for GKD based on generalized Gauss-Laguerre quadrature are derived. Since outage probability (OP) analysis with exact CDF is found to be unstable, approximated and asymptotic OP expressions are derived and validated via Monte Carlo simulation technique. Approximated CDF, in turn OP, expression is almost excellent. Unlike existing works, our expressions are unique and valid for all cases such as FD and HD together with pSIC and ipSIC, i.e. expressions are not given separately but in a single compact form. Effects of SI, ipSIC, fading and shadowing parameters on OP are demonstrated and it is also shown that RS can significantly reduce OP. Finally, nonzero diversity order is asserted and details are provided. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the full-duplex (FD) decode-and-forward (DF) cooperative relaying system, whereas the relay node can harvest energy from radiofrequency (RF) signals of the source and then utilize the harvested energy to transfer the information to the destination. Specifically, a hybrid time-power switching-based relaying method is adopted, which leverages the benefits of time-switching relaying (TSR) and power-splitting relaying (PSR) protocols. While energy harvesting (EH) helps to reduce the limited energy at the relay, full-duplex is one of the most important techniques to enhance the spectrum efficiency by its capacity of transmitting and receiving signals simultaneously. Based on the proposed system model, the performance of the proposed relaying system in terms of the ergodic capacity (EC) is analyzed. Specifically, we derive the exact closed form for upper bound EC by applying some special function mathematics. Then, the Monte Carlo simulations are performed to validate the mathematical analysis and numerical results. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel routing technique for millimeter wave (mmWave) networks to improve the spectral efficiency. The performance of the proposed nth best relay routing technique is investigated using tools from stochastic geometry. First, we derive the probability density function (PDF) of the distance between the nth best relay and destination. Capitalizing on this result, we derive a closed-form expression of the coverage probability over the log-normal fading channels. Monte Carlo simulations show an accurate match with the analytical results. We further demonstrate that the coverage probability varies according to specific system parameters, such as density of relays, blockage density and the signal-to-noise ratio threshold. Furthermore, we show that the adaptive signal-to-noise ratio threshold plays an important role in improving the spectral efficiency for different relay density, blockage density and the order of best relay (n). These findings provide insights for designing multi-hop mmWave networks with better performance. [ABSTRACT FROM AUTHOR]

In this paper, performance analysis of a relay based hybrid free space optical and radio frequency (FSO/RF) communication system is achieved by calculating outage probability. Some advanced concepts like hybrid spatial modulation (HSM), transmit source selection (TSS) and HSM along with TSS for such hybrid systems are proposed for the first time. These cooperative systems employ decode and forward (DF) scheme at the relay. The performance of these schemes are compared with the existing ones analytically and validated by means of Monte Carlo simulations. The FSO channel model incorporates pointing errors for outdoor scenarios. The system performance is influenced by various parameters which is explored extensively in this paper. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA)-based cognitive radio (CR) networks have recently emerged as a promising solution to enhance the spectral efficiency and massive connectivity problems. In this paper, we investigate the error rate performance of relay-assisted NOMA with partial relay selection in an underlay cognitive radio network. In this setup, $K$ relays are used to assist in transmission between secondary NOMA users and a secondary base station (SBS), where the relay (R) with the strongest link with the SBS is selected to amplify-and-forward (AF) its received signals to the secondary receivers. We derive an accurate approximation for the pairwise error probability (PEP) of the secondary users with imperfect successive interference cancellation (SIC). Subsequently, the derived PEP expression is utilized to deduce a union bound, which is considered as an upper bound on the bit error rate (BER). We further formulate an optimization problem to calculate the optimum power coefficients that minimize the derived union bound. Numerical and Monte Carlo simulation results are presented to corroborate the derived analytical expressions and give some useful insights into the error rate performance of each user. [ABSTRACT FROM AUTHOR]

In this paper, we apply the power splitting-based energy-harvesting protocol to enhance the transmission between a wireless access point and a mobile user via a helping relay. The mobile user exploits the energy supplied by the access point and forwarded by the relay to transmit its own data back to the access point, again with the helping of the relay. Here, the effect of various system parameters, including power-splitting factor and the power-to-noise ratio on the system performance, is rigorously studied, with closed-form expressions for the outage probability and system throughput as the results. Furthermore, we figure out the optimal power-splitting ratio at which the information throughput from the user to the AP is maximized, subject to the constraint on the transmitting power at the access point. All above analytical results are also supported by Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

In this paper, we propose a dual-hop radio-frequency (RF)/free-space optical system with multiple relays employing the decode-and-forward and amplify-and-forward with a fixed gain relaying scheme. The RF channels are subject to a Rayleigh distribution while the optical links experience a unified fading model emcopassing the atmospheric turbulence that follows the Málaga distribution (or also called the \mathcal M -distribution), the atmospheric path loss, and the pointing error. Partial relay selection with outdated channel state information is proposed to select the candidate relay to forward the signal to the destination. At the reception, the detection of the signal can be achieved following either heterodyne or intensity modulation and direct detection. Many previous attempts neglected the impact of the hardware impairments and assumed ideal hardware. This assumption makes sense for low data rate systems but it would no longer be valid for high data rate systems. In this paper, we propose a general model of hardware impairment to get insight into quantifying its effects on the system performance. We will demonstrate that the hardware impairments have small impact on the system performance for low signal-to-noise ratio (SNR), but it can be destructive at high SNR values. Furthermore, analytical expressions and upper bounds are derived for the outage probability and ergodic capacity while the symbol error probability is obtained through the numerical integration method. Capitalizing on these metrics, we also derive the high SNR asymptotes to get valuable insight into the system gains, such as the diversity and the coding gains. Finally, analytical and numerical results are presented and validated by the Monte Carlo simulation. [ABSTRACT FROM PUBLISHER]

In the work, a dual-hop cooperative simultaneous wireless information and power transfer (SWIPT) system, in which there are a source–destination ( S – D ) pair and a relay node ( R ), is considered. R adopts threshold amplify-and-forward (AF)/decode-and-forward (DF) relaying schemes to decide whether to aid S – D pair’s information transmission not. The effect of SWIPT on the outage performance has been investigated and the closed-form analytical expressions for outage probability have been derived for threshold AF and DF relaying schemes, respectively, which are verified by Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the secrecy outage performance of a dual-hop inter-vehicle communication system, in which all nodes are in motion and all fading channels are assumed to undergo cascaded Rayleigh distributions. In particular, a mobile node (source) with a single antenna transmits confidential information to another mobile node (destination) equipped with M ( M ⩾ 1 ) antennas through N ( N > 1 ) single-antenna road-side relays in the presence of an eavesdropper with L ( L ⩾ 1 ) antennas. Assuming decode-and-forward relaying, the K th best relay is selected to assist source–destination transmission based on two classical relay selection schemes: (i) the optimal source-relay link scheme; and (ii) the optimal source-relay-destination link scheme. Closed-form analytical expressions for secrecy outage probability of those two schemes are derived, and verified with Monte Carlo simulation results. [ABSTRACT FROM AUTHOR]

In this paper, the spatial modulation (SM) technique is employed at the source and relay nodes in a full-duplex two-way relay channel (FD-TWRC) to support spectral-efficient bi-directional communications while guaranteeing a low cost implementation. Maximum likelihood detectors are employed at each node that is subject to an intrinsic self-loop interference. We first propose a tight upper bound on the average bit error probability (ABEP). Then, based on the ABEP upper bound, an asymptotic ABEP expression is derived in the high signal-to-noise ratio (SNR) regime. Exploiting the asymptotic ABEP, an exact SNR threshold for the selection between FD-TWRC-SM and half-duplex (HD)-TWRC-SM is derived in a closed form, which sheds light on when it is beneficial to select the FD (or HD) mode. In addition, the power allocation (PA) among sources and relay is investigated, through which an optimal PA factor in terms of ABEP is obtained. All analytical results derived in this paper are verified by Monte Carlo simulations, from which some new insights are obtained on the performance of FD-TWRC-SM. [ABSTRACT FROM AUTHOR]

In a dual-hop relaying system without a direct link between the source and the destination, the source broadcasts information signal to the relay and relay broadcasts it to the destination, thus it uses two phases to transmit one symbol. This study proposes a novel scheme to incorporate signal space diversity into a dual-hop relaying system with multiple decode-and-forward (DF) relays to enhance its spectral efficiency. The proposed dual-hop signal space cooperative relaying scheme transmits two symbols in three phases while the conventional dual-hop DF relaying system uses four phases to transmit the same two symbols. Therefore, the proposed scheme improves the spectral efficiency without additional complexity, bandwidth or transmit power. The proposed scheme is analysed over Rayleigh fading channel and error probability performance is derived. Moreover, an asymptotic approximation for the error probability is obtained to illustrate the impact of different system parameters and diversity gain. In addition, this study discusses the power allocation optimisation, relay position optimisation and the joint optimisation of both. Furthermore, closed-form expression for the average channel capacity is derived. In the end, analytical results are compared and validated through Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The outage probability (OP) performance of transmit antenna selection (TAS) in a decode-and-forward relaying mobile-to-mobile system with relay selection overN-Nakagami fading channels is investigated. Exact closed-form expressions for the OP of two TAS schemes are derived, and the optimal power allocation optimisation problem is formulated. The OP performance is evaluated via Monte Carlo simulation to verify the analysis. The results obtained show that the optimal TAS scheme has better performance than the suboptimal TAS scheme, but the performance gap between these techniques decreases as the number of source antennas increases. [ABSTRACT FROM AUTHOR]

In this paper, a novel scheme is proposed to enhance the spectral efficiency of a two-way cooperative relaying system, where two source terminals exchange information directly and via K intermediate relays using the three-phase two-way decode-and-forward (DF) protocol. Signal space diversity (SSD) is incorporated into the two-way cooperative relaying system in the proposed scheme that exploits the inherent diversity in the modulation signal space by rotating and expanding the ordinary constellation. The proposed SSD-based three-phase two-way DF relaying scheme exchanges four symbols in three time slots and thus doubles the spectral efficiency as compared to the conventional three-phase two-way DF relaying system, where six time slots are required to exchange the same four symbols. This improvement in spectral efficiency is achieved without adding any extra complexity, bandwidth, or transmit power. A comprehensive analysis of the proposed scheme is carried out in this paper, and closed-form expressions for various performance metrics, including error probability, outage probability, and channel capacity, are derived. It is shown that the proposed scheme provides a diversity gain equal to one higher than the number of relays. The paper also studies different schemes for the optimization of relay position and power allocation. Finally, Monte Carlo simulations are performed which confirm the validity and accuracy of the analytical framework. [ABSTRACT FROM AUTHOR]

This paper proposes two new data detection algorithms for decode-and-forward alternate-relaying cooperative communication systems. These algorithms are discussed in the context of bit-interleaved coded modulation transmission with a multiple-antenna destination. The interference signal, resulting from the concurrent transmission of the source and one of the relays, is exploited as a beneficial resource to develop an optimal data detection algorithm. We show that the optimal algorithm can be implemented by parallel demappers, each based on a family of Bahl, Cocke, Jelinek, and Raviv algorithms, connected to parallel decoders in an iterative way. Due to the need to buffer the entire frame before decoding, the optimal algorithm suffers from long processing time. A suboptimal algorithm is also proposed to avoid this problem, where each packet is decoded by using two consecutive received packets. The suboptimal algorithm reduces processing time, complexity, bandwidth loss, and memory size with a slight increase in the bit error rate (BER). The BER performance of the proposed algorithms is evaluated via Monte Carlo simulations, and the results indicate their effectiveness in improving the BER performance. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the outage behavior of decode-and-forward (DF) relaying in the context of selective two-way cooperative systems. First, a new relay selection metric is proposed to take into consideration both transmission rates and instantaneous link conditions between cooperating nodes. Afterward, the outage probability of the proposed system is derived for Nakagami- $m$ fading channels in the case when perfect channel state information (CSI) is available and then extended to the more realistic scenario where the available CSI is outdated due to fast fading. New expressions for the outage probability are obtained, and the impact of imperfect CSI on the performance is evaluated. Illustrative numerical results, Monte Carlo simulations, and comparisons with similar approaches are presented to assess the accuracy of our analytical derivations and confirm the performance gain of the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper proposes a Decode-and-Forward (DF) relaying scheme for the multi-hop transmission in wireless networks, where the information generated by an independent source has to be sent to a far destination based on multiple-relay cooperation. The proposed DF scheme blends together convolutional channel coding with linear combination of blocks of data over a finite field using very short block lengths ( K=13). We provide an extrinsic information transfer (EXIT) chart analysis to understand the good performance behavior of the proposed scheme when compared with other referenced schemes using much larger block lengths. This fact is corroborated by a set of Monte Carlo simulations. Moreover, the proposed DF scheme is suitable for large multi-hop networks since a negligible performance degradation is obtained when adding more hops. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the end-to-end performance of dual-hop proactive decode-and-forward relaying networks with $N$th best relay selection in the presence of two practical deleterious effects: i) hardware impairment and ii) co-channel interference. In particular, we derive new exact and asymptotic closed-form expressions for the outage probability and average channel capacity of $N$th best partial and opportunistic relay selection schemes over Rayleigh fading channels. Insightful discussions are provided. It is shown that, when the system cannot select the best relay for cooperation, the partial relay selection scheme outperforms the opportunistic method under the impact of the same co-channel interference (CCI) . In addition, without CCI but under the effect of hardware impairment, it is shown that both selection strategies have the same asymptotic channel capacity. Monte Carlo simulations are presented to corroborate our analysis. [ABSTRACT FROM PUBLISHER]

Most of existing papers on cognitive relay networks with multiple primary user (PU) receivers consider the scenario where the PU receivers utilize the same spectrum band. In this paper, we consider a new scenario where the PU receivers utilize orthogonal spectrum bands and the spectrum of a PU receiver whose channel enhances the performance of the secondary system is shared with the secondary user (SU) nodes. Using orthogonal spectrum bands in cellular networks aims to reduce the interference between users as in the downlink transmission where orthogonal frequency bands are used by the base station in transmitting the data for the different users. In this paper, we study the outage performance of cognitive opportunistic decode-and-forward relaying operating in the secondary network with multiple PU receivers and in the presence of interference from a PU transmitter. A closed-form expression is derived for the outage probability with all system links following Rayleigh distribution. Furthermore, to get more insights about the system behavior, the performance is studied at the high signal-to-noise ratio (SNR) regime where approximate expressions for the outage probability, diversity order, and coding gain are obtained. Monte Carlo simulations are given to validate the achieved results. Main findings illustrate that with fixed interference power, the diversity order of the secondary system equals the number of relays and it is not affected by the number of PU receivers. Also, results show that the number of PU receivers affects the system performance through affecting only the coding gain. Unlike the existing papers where the same spectrum band is assumed to be shared by the PU receivers, our findings demonstrate that increasing the number of PU receivers in the proposed scenario enhances the system performance. Finally, results illustrate that when the interference at the SU relays or at SU destination or at both scales with SNR, the system achieves a zero diversity order and a noise floor appears in the results due to the effect of interference on the system performance. [ABSTRACT FROM AUTHOR]

Improving spectral efficiency under a certain energy limitation is an important design metric for future wireless communications as a response to the growing transmission demand of wireless devices. In order to improve spectral efficiency for communication systems without increasing energy consumption, this paper considers a non-orthogonal multiple access (NOMA)–based cognitive radio network, with the assistance of a wireless-powered relay station (RS), and then analyzes the system outage performance under amplified-and-forward (AF) and decoded-and-forward (DF) cooperative transmission modes. Specifically, the base station (BS) has the opportunity to cooperate by transmitting information through the RS, depending on whether the RS can harvest sufficient RF energy for cooperative transmission. That is to say, when the energy stored by the RS is sufficient for cooperative transmission, the RS will assist the BS to forward information; otherwise, the BS will send information through direct links, while the RS converts the radio frequency (RF) signals sent by the BS into energy for future transmission. Moreover, the transmission power required by the RS for cooperative transmission is usually relatively large, while the amount of harvested energy by the RS in a transmission slot is usually low, so it takes several consecutive time slots to accumulate enough transmission energy. To this end, we utilize a discrete-time Markov chain to describe the processes of charging and discharging of the RS. Subsequently, we derive the closed-form outage probabilities of both the primary and secondary systems for the considered system in AF and DF modes through mathematical analysis, and verify the accuracy of the analyses through Monte Carlo simulation. The simulation results show that the two proposed cooperative transmission schemes with AF and DF relaying techniques outperform both direct transmission and other similar schemes in both the primary and secondary system, while the DF scheme can provide better performance than the AF scheme within the range of setting values. [ABSTRACT FROM AUTHOR]

In this paper, we study the physical layer security for simultaneous wireless information and power transfer (SWIPT)-based half-duplex (HD) decode-and-forward relaying system. We consider a system model including one transmitter that tries to transmit information to one receiver under the help of multiple relay users and in the presence of one eavesdropper that attempts to overhear the confidential information. More specifically, to investigate the secrecy performance, we derive closed-form expressions of outage probability (OP) and secrecy outage probability for dynamic power splitting-based relaying (DPSBR) and static power splitting-based relaying (SPSBR) schemes. Moreover, the lower bound of secrecy outage probability is obtained when the source's transmit power goes to infinity. The Monte Carlo simulations are given to corroborate the correctness of our mathematical analysis. It is observed from simulation results that the proposed DPSBR scheme outperforms the SPSBR-based schemes in terms of OP and SOP under the impact of different parameters on system performance. [ABSTRACT FROM AUTHOR]

In this study, we examine an emerging Multiple-Input-Multiple-Output (MIMO) Non-Orthogonal Multiple Access (NOMA) network which combines Transmit Antenna Selection (TAS) and Simultaneous Wireless Information and Power Transfer (SWIPT) protocols. A pre-coding channels matrix was designed to aid the TAS protocol. We deployed a strong user as a relay to assist a weak user. Three cooperative MIMO-NOMA network scenarios were investigated. In the first scenario, we assumed the relay was deployed with (i) Decode-and-Forward (DF), (ii) Amplify-and-Forward (AF) with Fixed Gain (FG) and (iii) AF with a Variable Gain (VG) protocols to improve system performance over the first scenario. In scenario (iii), we investigated an amplify coefficient based on the maximum of instantaneous CSI and obtained the Outage Probability (OP) in novel closed form. The analytical results showed that although the Base Station (BS) sent information and energy at the same instant, the OP performance at the relay was sufficient due to assistance from multi-antennas and the TAS protocol. However, the OP performance at the user under cooperation with a relay using the AF-VG protocol achieved better system performance than the DF and AF-FG protocols. We proved and verified the analytical results with Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

This paper proposes a wavelength diversity decode-and-forward (DF) serial relay orthogonal frequency division multiplexing (OFDM) free-space optical (FSO) communication system. The proposed system performance is evaluated by the quadrature phase-shift keying (QPSK) as an OFDM signal subcarrier mapping method, considering the maximum ratio combining (MRC) and equal gain combining (EGC) schemes, over exponentiated Weibull (EW) channels. The Monte Carlo (MC) method is used to simulate the system performance. The closed-form expressions of outage probability and average symbol error rate (SER) are also derived considering the joint effect of atmospheric turbulence, path loss, and pointing errors. In addition, the effects of the number of operating wavelength, receiving aperture diameter, number of relay hops, and link length between relays on the outage performance of an FSO communication system, and the effect of the MRC and EGC schemes the average SER are analyzed through simulations. The MC simulations verify the correctness of the numerical results. The results show that the proposed system can concurrently expand the communication range and improve system performance. • A wavelength diversity serial relay OFDM FSO communication system is proposed. • The closed-form expressions of OP and SER of proposed system are derived. • The OP and SER performance of proposed system are analyzed. • The proposed system expands the communication range and improves performance. [ABSTRACT FROM AUTHOR]