Dual Hop Research Articles

Physical layer security in cognitive radio network with energy harvesting relay and jamming in the presence of direct link

In this paper, we examine the physical (PHY) layer security in terms of secrecy outage of an energy harvesting (EH) relay based underlay cognitive radio network (CRN) in the presence of an eavesdropper. A dual hop communication network consisting of an energy harvesting relay that harvests energy from radio transmission of secondary user (SU) network using a time switching relay (TSR) scheme is studied. The relay works in decode and forward (DF) mode and forwards the confidential message to the destination, if it is successfully decoded at the relay. The advantage of the direct link between source to destination is exploited, if the relay link is in outage. Furthermore, simultaneous transmission of message signal and jamming signal to the legitimate nodes and illegitimate node respectively degrades the eavesdropping link capacity. We evaluate the secrecy outage probability (SOP) of the network under study. It is found that exploiting the direct link at the destination increases the secrecy in transmission as compared to the case of only relay based transmission without direct link. The impact of interference threshold, energy harvesting time, power allocation factor, target data rate, target secrecy rate and direct link on SOP of this proposed network is investigated.

Analysis and Optimization Study of Antenna Selection in Dual Hop Relay Networks over Weibull Fading Channels

Field experiments show that Weibull distribution can be considered as the most suitable distribution to model weak to high signal power levels in indoor and outdoor environments. Recently, Exponentiated Weibull which is a special case of Weibull fading, have been widely adopted in free-space optical communication systems to model weak and high levels of turbulence effects. Motivated from the increasing use of Weibull distribution, this paper studies the popular dual-hop amplify-and-forward relay network with joint transmit and receive antenna selection where closed form ergodic capacity, symbol error rate and outage probability expressions are derived for Weibull fading channels. With the help of high SNR analysis, diversity gain, array gain and optimum relay location are obtained. Finally, theoretical findings are validated by simulation results.

Performance analysis of decode-and-forward partial relay selection in NOMA systems with RF energy harvesting

In this paper, we investigate a dual hop communication decode-and-forward scheme relay system where a source node wants to transmit simultaneously two symbols to two desired destinations with the help of one selected energy constraint relay node. The power for operation of relay is come from the ambient radio frequency energy harvesting and the non-orthogonal multiple access technology is applied. We mathematically evaluate the impact of partial relay selection on the system performance by considering the undecodable probability of symbol for which symbols can not be decoded at the relay node or two destinations. Furthermore, the undecodable probability and the ergodic capacity are analyzed under the effect of imperfect and perfect successive interference cancellation (SIC). The results of theoretical analysis is similar to the simulation results, especially in the high region of transmit power. It verifies the correctness of mathmatical closed-form in our analysis. The results also show that the performance of the system are significantly influenced by the efficiency of SIC technology and the number of relay nodes.

A statistical channel model for a decode-and-forward based dual hop mixed RF/FSO relay network

In this paper, we have considered a dual branch with dual hop wireless cooperative communication system which comprises direct radio frequency path as well as indirect path with RF links and a free space optics (FSO) link through a Relay node (R) in between source (S) to destination (D). The faded channel for RF link is modelled with Nakagami-m distribution and the FSO link is modelled using double generalized Gamma fading. This proposed communication system uses the intensity modulation and direct detection technique for optical signal transmission and reception purpose, respectively in the FSO link. Further, we have employed selection combining diversity technique at the receiver during the use of both branches. Moreover, we have also derived probability density function and cummulative distribution function of the proposed communication system which is used to compute the performance metrics such as the outage probability and average bit error rate.

Relay-aided free-space optical communications using [formula omitted] distribution over atmospheric turbulence channels with misalignment errors

In this paper, we have analyzed the performance of dual hop radio frequency (RF)/free-space optical (FSO) fixed gain relay environment confined by atmospheric turbulence induced fading channel over FSO link and modeled using α−μ distribution. The RF hop of the amplify-and-forward scheme undergoes the Rayleigh fading and the proposed system model also considers the pointing error effect on the FSO link. A novel and accurate mathematical expression of the probability density function for a FSO link experiencing α−μ distributed atmospheric turbulence in the presence of pointing error is derived. Further, we have presented analytical expressions of outage probability and bit error rate in terms of Meijer-G function. In addition to this, a useful and mathematically tractable closed-form expression for the end-to-end ergodic capacity of the dual hop scheme in terms of bivariate Fox’s H function is derived. The atmospheric turbulence, misalignment errors and various binary modulation schemes for intensity modulation on optical wireless link are considered to yield the results. Finally, we have analyzed each of the three performance metrics for high SNR in order to represent them in terms of elementary functions and the achieved analytical results are supported by computer-based simulations.

Enhancing physical layer security in AF relay–assisted multicarrier wireless transmission

AbstractIn this paper, we study the physical layer security problem in the dual‐hop orthogonal frequency division multiplexing–based wireless communication system. First, we consider a single‐user single‐relay system and study a joint power optimization problem at the source and relay subject to individual power constraint at the 2 nodes. The aim is to maximize the end‐to‐end secrecy rate with optimal power allocation over different subcarriers. Later, we consider a more general multiuser multirelay scenario. Under high signal‐to‐noise ratio approximation for end‐to‐end secrecy rate, an optimization problem is formulated to jointly optimize power allocation at the base station, the relay selection, subcarrier assignment to users, and the power loading at each of the relaying node. The target is to maximize the overall security of the system subject to independent power budget limits at each transmitting node and the orthogonal frequency division multiple access–based exclusive subcarrier allocation constraints. A joint optimization solution is obtained through the duality theory. Dual decomposition allows to exploit convex optimization techniques to find the power loading at the source and relay nodes. Furthermore, an optimization for power loading at relaying nodes along with relay selection and subcarrier assignment for the fixed power allocation at the base station is also studied. A suboptimal scheme that explores joint power allocation at all transmitting nodes for the fixed subcarrier allocation and relay assignment is investigated. Finally, simulation results are presented to validate the performance of the proposed schemes.

Full-duplex distributed switch-and-stay energy harvesting selection relaying networks with imperfect CSI: Design and outage analysis

We analyze the effect of distributed switch and stay combining (DSSC) technique and imperfect channel state information (CSI) in the scenario, where the communication between the source and the destination is conducted through either the direct transmission or with the help of the best relay among K full-duplex energy harvesting relays by using partial relay selection. To activate such communication, at the destination, we apply DSSC technique, which is considered as an effective method to achieve spatial diversity in a distributed manner with low processing complexity and compatibility to resource-constrained wireless networks. Considering two popular relaying protocols, i.e., decode-and-forward (DF) and amplify-and-forward (AF), the performance analysis in terms of outage probability (OP) is carried out. Numerical results show that imperfect CSI has a negative impact on system performance. Besides that, our DSSC-full duplex selection relaying (FDSSCSR) system achieves a better performance in terms of outage probability than that of the DSSC-half duplex selection relaying (HDSSCSR) and the full duplex/half duplex dual hop relaying with partial relay selection (FD/HDDRPRS) systems. Simulation results are conducted to verify the correctness of our analysis.

Performance of antenna selection schemes in dual hop full-duplex decode-and-forward relaying over Nakagami-m fading channels

In this paper, we investigate the outage performance of several antenna selection (AS) schemes in dual hop full-duplex (FD) multiple-input multiple-output (MIMO) relay networks in which the relay adopts decode-and-forward (DF) protocol over Nakagami-m fading channels. In the network, the source (S), destination (D) and relay (R) are assumed to be equipped with multiple antennas. We assume that the line-of-sight component between S and D cannot be established due to the poor fading environment conditions. For signal transmission-reception during the training period, only a single antenna at each node is selected according to selection techniques, and then with the help of an error-free feedback channel the selected antenna index is sent to the related node. Outage probability (OP) expressions related to AS schemes are obtained in closed forms and asymptotic OPs are also derived in order to get more meaningful insights into OP and diversity behaviour. The theoretical results are verified by Monte Carlo simulations. We show that performance of the FD relay can be significantly improved by using selection techniques compared to half-duplex (HD), especially at low signal-to-noise ratio (SNR) region. In addition, results show that the performance floor level meaning zero diversity at high SNR region, which is also confirmed by asymptotic analysis and is an inherent disadvantage of FD relay, can be decreased. Moreover, it is shown that the FD relay with AS schemes outperforms HD as the target rate increases for a certain value of SNR and residual self-interference power.

Performance analysis of DF-relayed cognitive underlay networks over EGK fading channels

In this paper, we analyse the performance of a dual hop cognitive radio underlay network employing a decode and forward relay. The fading channels have been modeled using extended generalized-K fading statistics. The interference temperature is taken as a constraint so that the transmit power of the secondary source and the relay do not exceed this value. This limits the transmit powers of the secondary network to ensure no interference with the primary communication which is imperative in cognitive underlay systems. First the signal to noise ratio at the relay and the destination of the system under consideration are analyzed and then the respective cumulative distribution function and probability density function are evaluated. This is followed by the derivation of statistical expression for end-to-end signal to noise ratio of the relay network, it’s cumulative distribution function and probability density function. These expressions are further utilized to derive the analytical expressions for the outage probability and the ergodic capacity of the underlay dual-hop cognitive relay network. Our results demonstrate the dependence of the performance of the system on various parameters under the constraints of transmit power and interference temperature already defined. The mathematical analysis is followed by various numerical examples to illustrate how the various parameters of the system affect it’s performance.

Ergodic Capacity Analysis of AF DH MIMO Relay Systems With Residual Transceiver Hardware Impairments: Conventional and Large System Limits

Despite the inevitable presence of transceiver impairments, most prior work on multiple-input multiple-output (MIMO) wireless systems assumes perfect transceiver hardware, which is unrealistic in practice. In this direction, motivated by the increasing interest in MIMO relay systems due to their improved spectral efficiency and coverage, this paper investigates the impact of residual hardware impairments on the ergodic capacity of dual-hop (DH) amplify-and-forward (AF) MIMO relay systems. Specifically, a thorough characterization of the ergodic channel capacity of DH AF relay systems in the presence of hardware impairments is presented herein for both the finite and large antenna regimes by employing results from finite-dimensional and large random matrix theory, respectively. Regarding the former setting, we derive the exact ergodic capacity as well as closed-form expressions for tight upper and lower bounds. Furthermore, we provide an insightful study for the low signal-to-noise ratio regimes. Next, the application of the free probability theory allows us to study the effects of the hardware impairments in future 5G deployments including a large number of antennas. While these results are obtained for the large system limit, simulations show that the asymptotic results are quite precise even for conventional system dimensions.

Performance of Joint Relay and Antenna Selection in the Full-Duplex Amplify-and-Forward Relay Networks

This paper focuses on the joint relay and antenna selection problem in dual hop full-duplex (FD) relay network with one source, one destination and N FD amplify-and-forward relays in flat Rayleigh ...

Frame error rate for single-hop and dual-hop transmissions in 802.15.4 LoWPANs

ABSTRACTIEEE 802.15.4 is a popular standard for personal area networks used in different low-rate short-range applications. This paper examines the error rate performance of 802.15.4 in fading wireless channel. An analytical model is formulated for evaluating frame error rate (FER); first, for direct single-hop transmission between two sensor nodes, and second, for dual-hop (DH) transmission using an in-between relay node. During modeling the transceiver design parameters are chosen according to the specifications set for both the 2.45 GHz and 868/915 MHz bands. We have also developed a simulation test bed for evaluating FER. Some results showed expected trends, such as FER is higher for larger payloads. Other observations are not that intuitive. It is interesting to note that the error rates are significantly higher for the DH case and demands a signal-to-noise ratio (SNR) penalty of about 7 dB. Also, the FER shoots from zero to one within a very small range of SNR.

Outage analysis of TAS/MRC in dual hop full-duplex MIMO relay networks with co-channel interferences

In this paper, we investigate the outage performance of transmit antenna selection (TAS) and maximal-ratio combining (MRC) in dual hop full-duplex (FD) amplify-and-forward (AF) relay network over Rayleigh fading channels. In the analysis, Rayleigh faded multiple co-channel interferers (CCIs) are also taken into account at the relay. In the network, source and destination are equipped with multiple antennas, and relay is equipped with one receive and one transmit antennas, respectively and source-destination link is not available. While the TAS is applied at the source without considering residual self-interference (RSI) effect, received signals at the destination are combined based on the MRC technique. For the analysis, we consider three approaches at the relay. In the first, we consider the received signal at the relay is corrupted by faded RSI and noise, in the second one, the RSI is considered as non-fading. In the last one, the noise is neglected. In all cases, the relay suffers from multiple Rayleigh faded CCIs. Outage probability (OP) expression related to all the cases is derived and obtained in single integral forms in case of the faded/non-fading RSI and in closed form in case of the noise neglected approach. Moreover, we also find asymptotic OPs and conduct effective diversity order analysis. The analytical results are verified by the Monte Carlo simulations. Results show that TAS decreases error floor at high signal-to-noise ratio (SNR) region and MRC provides diversity gain at low SNR region. In addition, approaches II and III are good approximations to approach I at low and high SNR regions, respectively.

Dual Hop Relay with Cooperative Diversity and Relay Selection

Dual Hop Relay with Cooperative Diversity and Relay Selection

New threshold-based Relay Selection Algorithm in Dual Hop Cooperative Network

Abstract: Cognitive radio and cooperative communications emerged as networking technologies that solve the radio spectrum scarcity and the fading effects in wireless communications while improving the reliability, the performance and the adaptability of the network. In this work, we are aiming to achieve cooperative diversity via the use of an energy harvesting underlay cognitive radio network operating in decode and forward (DF) relay selection. The selection targets to satisfy the interference threshold and residual battery power conditions by the use of Green relays that permits to enable or disable a relay depending on a comparison between its residual .energy level and the set threshold.

Performance analysis of decode and forward relaying over dual-hop mixed fading channels

In this paper, the end-to-end performance of decode and forward relaying over an independent, asymmetrical and generalized fading channels are analyzed. We consider a dual hop mixed fading channel, one hop is subject to η-μ fading and the other hop is subject to κ-μ fading. We derived an exact expression of symbol error rate (SER) for non-coherent detection, outage probability, outage capacity and an approximate expression of SER for coherent detection. In addition, we compared the SER performance over different η,μ1,κ,μ2 which corresponds to different fading effects and validated the arrived expressions through Monte-Carlo simulation.

Full-duplex distributed switch-and-stay networks with wireless energy harvesting: design and outage analysis

Distributed switch and stay combining (DSSC) has been considered as an effective technique to achieve spatial diversity in a distributed manner with low processing complexity. In this paper, we incorporate DSSC into a full-duplex dual hop relaying system, where two energy-constrained relay nodes assist the information transmission from the source to the destination using energy wirelessly harvested from the source. By applying DSSC at the destination, this efficient technique not only improves performance of full-duplex relaying systems and increases the system diversity but also reduces the implementation and hardware complexity at the destination. We obtain tight approximate expression for outage probability in the case of using decode-and-forward (DF) relaying protocol and analytical expression for outage probability in the case of using amplify-and-forward (AF) relaying protocol. Numerical results show that our DSSC full-duplex relaying with wireless information and power transfer (WIPT) system achieves the full spatial diversity and has a better performance in terms of outage probability than that of the DSSC half-duplex relaying and conventional full-duplex relaying with WIPT system.

On the Maximum and Minimum of Double Generalized Gamma Variates With Applications to the Performance of Free-Space Optical Communication Systems

In this paper, we derive the exact statistical characteristics of the maximum and the minimum of two modified double generalized gamma variates in closed form in terms of Meijer's G-function, Fox's H-function, the extended generalized bivariate Meijer's G-function, and H-function, in addition to simple closed-form asymptotic results in terms of elementary functions. Then, we rely on these new results to present the performance analysis of 1) a dual-branch free-space optical selection combining (FSO SC) diversity and 2) a dual-hop (DH) FSO relay transmission system over double generalized gamma fading channels with the impact of pointing errors. In addition, we provide asymptotic results of the bit error rate (BER) of the two systems at a high signal-to-noise ratio (SNR) regime. Computer-based Monte Carlo simulations verify our new analytical results.

Energy Efficiency of a Dual Hop Clustered Networks in a High Data Rate

Energy Efficiency of a Dual Hop Clustered Networks in a High Data Rate

Decode‐and‐forward relaying in mixed η − μ and gamma–gamma dual hop transmission system

In this study, the authors carry out the performance analysis of an asymmetric dual hop relay system composed of both radio-frequency (RF) and free-space optical (FSO) links. The RF link is subject to generalised η - μ distribution, while the channel for FSO link is modelled as gamma-gamma distribution. The decode-and-forward relaying phenomena is used, where the relay decodes the received RF signal from the source and converts it into an optical signal using the sub-carrier intensity-modulation (SIM) scheme for transmission over the FSO link. The FSO link is subjected to pointing errors and account for both types of detection techniques, i.e. IM/DD and heterodyne detection. Novel exact closed-form expressions for the probability density function and cumulative distribution function of the equivalent end-to-end signal-to-noise ratio of the mixed RF/FSO system in terms of Meijer's G function are derived. Capitalising on these derived channel statistics, they provide the new closed-form expressions of outage probability and the ergodic channel capacity. They also provide the average bit-error rate for different binary modulations. Furthermore, the Monte Carlo simulations validate the analytical results.