Exponentiated Weibull Fading Channels Research Articles

Pulse Jamming in Aperture-Averaged FSO Receiver Over Exponentiated Weibull Fading Channel

In this paper, we study the pulse jamming effect thoroughly in aperture-averaged free space optical (FSO) systems. The FSO fading channels are considered to be Exponentiated Weibull (EW) distributed due to its excellent fit for all aperture sizes over the ranges of atmospheric turbulence conditions. It is inferred from the theoretical analysis that random jamming behaviour is impulsive and it reveals a destructive property over aperture-averaged FSO receivers. Analytical expressions of the average bit error rate (ABER) and outage probability (OP) are formulated for the considered FSO system in the presence of random jammer. The effects of pulse jamming on ABER and OP performances are shown. Additionally, the asymptotic ABER analysis is performed in order to investigate the response of the considered FSO system in high transmit power region and to analyze the diversity order under the pulse jamming effect. Pointing error impairments, being another important performance degrading parameter of the FSO communication system, are studied along with the pulse jamming effect. Also, asynchronous jamming effect over the ABER performances is described by both analytically and graphically.

SER performance investigation of a MPPM relay-aided FSO system with three decision thresholds over EW fading channel considering pointing errors

The symbol error rate (SER) performance of a multi-hop parallel free-space optical (FSO) communication system with multiple pulse position modulation (MPPM) scheme considering three different decision threshold schemes, fixed decision threshold (FDT), optimized decision threshold (ODT), and dynamic decision threshold (DDT) has been investigated over exponentiated Weibull (EW) atmospheric turbulence channel combiningthe impact of the fading induced by pointing errors. On the basis of the decode-and-forward (DF) protocol, the cumulative distribution function (CDF) and probability density function (PDF) in terms of the Meijer’ s G-function for this considered FSO communication system are derived with the max–min criterion as the best path selection scheme. After that, the closed-form SER expressions for three threshold schemes are obtained by Gauss–Laguerre quadrature function and then confirmed by Monte Carlo (MC) simulation. The SER performance is further analyzed systematically under different turbulence conditions, receiver aperture sizes, jitter variances, and structure parameters (R and C) for three decision threshold schemes. The results show that pointing errors will deteriorate the system performance, while the multi-hop parallel transmission can improve the SER performance and expand the communication range. Furthermore, ODT and DDT schemes can significantly overcome the effect of the error floor of FDT scheme. This work benefits the development of the MPPM based relay-aided FSO system.

On the performance of AF full FSO two-way relay networks over exponentiated Weibull fading channels

This work implements free space optical communication (FSO) in an amplify-and-forward (AF) two-way relay network (TWRN) to exploit the advantages of spectral efficiency, full-duplex Gigabit throughput, license-free spectrum, easy installation and to overcome the limitations of free space optical communication due to distance dependent turbulence induced fading. To quantify the performance of the proposed scheme, overall outage probability (OOP) and ergodic sum rate (ESR) expressions are derived over Exponentiated Weibull (EW) fading channels. The simple theoretical results which are validated with the Monte-Carlo simulations show that a system designer can get a quick idea about the FSO TWRN without resorting to complex prototypes or simulations.

The analysis of multiuser relaying mixed RF/FSO networks over exponentiated Weibull fading channel

In this paper, the performance of multiuser relaying mixed radio frequency (RF)/free space optical (FSO) networks over exponentiated Weibull Fading Channel is studied. Based on the transmit opportunistic scheduling, a unified cumulative distribution function (CDF) of the end-to-end signal to noise ratio (SNR) for multiuser dual-hop relaying system is derived. Then the average symbol error rate (ASER), outage probability and ergodic channel capacity are analyzed in detail. Furthermore, in order to simplify the analysis of system performance, the asymptotic results for the outage probability and ASER are derived at high SNR regime. We also demonstrate Monte Carlo simulation to ensure the effectiveness of the results. The simulation results show that deploying the transmit opportunistic scheme can improve the proposed system performance. And aperture averaging and heterodyne detection technique can suppress the impact of turbulence on FSO networks.

Performance Improvement for Wireless Sensors Networks by Adopting Hybrid Subcarrier Intensity Modulation Over Exponentiated Weibull Turbulence Channels

We conduct a research on free space optical (FSO) communication system that is applied for transmission in wireless sensor networks (WSN), which is based on the hybrid pulse position modulation-binary phase shift keying-subcarrier intensity modulation (PPM-BPSK-SIM) undergoes novel Exponentiated Weibull fading channels. When battery-charged sensor transmission nodes with limited energy is transmitted, it is vital to study the performance of the transmission link. We have derived the exact joint probability function of the transmission link when the atmospheric turbulence and pointing errors are considering. On the basis of them, the unconditional average bit error rate (BER) for hybrid PPM-BPSK-SIM is derived, then the closed expression of the outage probability and the average channel capacity are also derived. Research results indicates that increasing the receiver aperture by aperture averaging effect can distinctly improve the performance of the link. Additionally, for any circumstances of atmospheric turbulence and pointing errors, by combining the utilization of hybrid PPM-BPSK-SIM modulation and symbol with average length greater than eight, the average BER performance can be conspicuously enhanced. The outage probability and average channel capacity of the FSO link are jointly affected by atmospheric turbulence and pointing error, and optimization strategies in different scenarios are given by our research.

On the performance of cognitive underlay RF/FSO communication systems with limited feedback

In this work, we consider an underlay cognitive radio (CR) RF/free space optical (FSO) network where the unlicensed secondary user (SU) wishes to communicate with a specific destination node with the aid of an optical path over a selected relay terminal without causing any interference to the primary user (PU). The proposed structure can be viable for metropolitans where an unlicensed user wishes to transfer its information to a specific destination node which is connected to the backbone network over an optical path. For the proposed structure, closed form and approximate outage probability and ergodic capacity expressions are derived for Nakagami-m/ Exponentiated Weibull fading channels. The results show that the transmission capacity of the SU depends on the weather conditions and the number of relays in the system.

The performance analysis of multi-hop MIMO free space optical communications with space–time block codes over exponentiated Weibull fading channels

The symbol error rate (SER) performance of decode-and-forward (DF) based multiple-input multiple-output (MIMO) multi-hop free-space optical (FSO) systems is investigated with space–time block coding (STBC) over the exponentiated Weibull (EW) fading channel. The moment generating function (MGF) and Gauss–Laguerre quadrature rule are adopted to derive the end-to-end (EE) analytical SER expressions for this considered FSO communication system. The SER performance is further studied under various hops, STBC schemes, and turbulence conditions detailly. In addition, the asymptotic EE SER expressions are obtained to evaluate the diversity orders. Results show that the SER performances of this FSO system under EW atmospheric turbulence distribution can be improved considerably by employing the STBC scheme, and the diversity order depends not only on the numbers of transmitting and receiving antennas, but also on the channel fading parameters. The SERs of EW distribution are compared with Lognormal (LN) and gamma–gamma (G–G) distributions in weak and strong turbulence atmosphere, respectively. We also verify these analytical results through Monte Carlo simulations. This work is beneficial to the design of FSO system.

Joint user and relay selection for relay-aided RF/FSO systems over Exponentiated Weibull fading channels

In this paper, we investigate the performance of joint user and relay selection scheme for a multi-user relayed network over mixed radio-frequency (RF) and free space optical (FSO) system. In this set-up, the non line-of-sight (NLOS) RF link is modeled with Rayleigh fading whereas the LOS FSO path is modeled with Exponentiated Weibull (EW) distribution. We assume that the multiple users at source terminal communicate with the destination over multiple decode and forward relays which are located at the rooftops of the buildings to provide a perfect LOS path. In the proposed scheme, all users send pilot signals to the destination through relay terminals and the latter jointly selects the best user and relay based on the maximization of the end-to-end signal-to-noise ratio (SNR). To quantify the performance of the proposed scheme, closed form outage and error probability are derived. Moreover, asymptotic analysis is performed to obtain important system parameters including fading severity, number of users and relays in the system. Finally, Monte-Carlo (MC) simulations are carried out the verify the performance of the considered scheme.

Performance analysis of multiuser diversity scheduling schemes in FSO communication system

Taking into consideration the aperture averaging, the system performance of a point-to-multipoint free space optical (FSO) system for various multiuser diversity scheduling schemes is studied over exponentiated Weibull (EW) fading channels. The selection principles of greedy scheduling (GS), selective multiuser diversity scheduling (SMDS), proportional fair scheduling (PFS) and selective multiuser diversity scheduling with exponential rule (SMDS-ER) schemes are introduced and compared on the basis of time-varying behavior of turbulence channel fading in the present system. The analytical average capacity expressions for the GS and SMDS schemes are derived, respectively. Then, the relative capacity simulations for PFS and SMDS-ER schemes are also provided over EW fading channels with the binary phase shift keying (BPSK) modulation. The results show that the GS scheme obtains the maximum average capacity at the cost of the fairness of users. The SMDS-ER receives the minimum capacity, but it guarantees the fairness of users. The SMDS and PFS schemes can get balance between capacity and fairness. This study can be used for FSO system design.

On the performance of 2[formula omitted]2 DF relay mixed RF/FSO airborne system over Exponentiated Weibull fading channel

This paper discuses the performance of a mixed free space optical (FSO)/radio frequency (RF) airborne communication system which consists of a dual-input dual-output (DIDO) relay based on decode-and-forward (DF), single-antenna RF transmitter, and single-aperture optical receiver. The Nakagami-m fading channel and exponentiated Weibull fading channel are adopted for the RF channel and FSO link, respectively. The analytical expressions of probability density function (PDF) and cumulative distribution function (CDF) about the equivalent signal-to-noise ratio (SNR) are obtained. We also analyze the average bit-error-rate and outage probability of the mixed FSO/RF system and derive closed form expressions by the Meijer’s G function. To further verify the performance of the system, we simulate to compare the performance of the DIDO and single-input single-output (SISO) relay-based communication systems. The DIDO relay-based system outperforms the SISO relay system.

Impact of pointing errors on the SER performance of free space optical communication system with two decision thresholds over exponentiated Weibull fading channels

The impact of pointing errors on the symbol error rate (SER) performance of multiple pulse-position modulation (MPPM) free space optical (FSO) system with optimized decision threshold (ODT) and dynamic decision threshold (DDT) is investigated over exponentiated Weibull atmospheric turbulence channels. The probability density function (PDF) of the aggregated channel model is derived on the basis of Meijer’s G-function and the closed-form SER expression is then obtained by Gauss–Laguerre quadrature function. The variations of SER performance with different jitter variances, beam width, aperture sizes, and turbulence strengths for these two decision threshold schemes are analyzed in detail. The study shows that the impact of jitter variances is more apparent for ODT than that for DDT scheme and the performance difference between ODT and DDT schemes decreases with the increase of beam width. Monte Carlo simulation is also provided to verify the correctness of the proposed SER models. This work is beneficial to the design of FSO system.

On the performance of dual-hop mixed RF/FSO wireless communication system in urban area over aggregated exponentiated Weibull fading channels with pointing errors

The performance of decode-and-forward dual-hop mixed radio frequency / free-space optical system in urban area is studied. The RF link is modeled by the Nakagami-m distribution and the FSO link is described by the composite exponentiated Weibull (EW) fading channels with nonzero boresight pointing errors (NBPE). For comparison, the ABER results without pointing errors (PE) and those with zero boresight pointing errors (ZBPE) are also provided. The closed-form expression for the average bit error rate (ABER) in RF link is derived with the help of hypergeometric function, and that in FSO link is obtained by Meijer’s G and generalized Gauss–Laguerre quadrature functions. Then, the end-to-end ABERs with binary phase shift keying modulation are achieved on the basis of the computed ABER results of RF and FSO links. The end-to-end ABER performance is further analyzed with different Nakagami-m parameters, turbulence strengths, receiver aperture sizes and boresight displacements. The result shows that with ZBPE and NBPE considered, FSO link suffers a severe ABER degradation and becomes the dominant limitation of the mixed RF/FSO system in urban area. However, aperture averaging can bring significant ABER improvement of this system. Monte Carlo simulation is provided to confirm the validity of the analytical ABER expressions.

ABER Performance of LDPC-Coded OFDM Free-Space Optical Communication System Over Exponentiated Weibull Fading Channels With Pointing Errors

A low-density parity-check (LDPC)-coded free space optical (FSO) orthogonal frequency-division multiplexing (OFDM) communication system over aggregated exponentiated Weibull (EW) fading channels with pointing errors considered is investigated. On the basis of the probability density function and cumulative distribution function of the composite channel gain, the analytical expressions of average bit error rate (ABER) of this FSO-OFDM system with on–off keying, K -ary quadrature amplitude modulation (QAM) and phase shift keying (PSK) modulation schemes are derived by using generalized Gauss–Lagurre quadrature rule, respectively. Monte Carlo simulations are provided to verify the validity of these three expressions. Furthermore, LDPC codes are applied in the simulation to improve the ABER performance. The results show that the ABER performance of 16-QAM-OFDM is better than that of the 16-PSK-OFDM system over composite EW fading channels, regardless of the turbulence strengths. For the modulation schemes involved, the degradation due to the increase of atmospheric turbulence strength for turbulence only scenario is more severe when compared with pointing errors included case. The study also demonstrates that significant coding gain improvement can be achieved by LDPC codes over EW fading channels, especially under strong turbulence condition. With pointing errors, more coding gain can be obtained when the jitter increases or beamwidth decreases.

Performance analysis for mixed FSO/RF Nakagami-m and Exponentiated Weibull dual-hop airborne systems

In this paper, the performances of mixed free-space optical (FSO)/radio frequency (RF) systems are presented based on the decode-and-forward relaying. The Exponentiated Weibull fading channel with pointing error effect is adopted for the atmospheric fluctuation of FSO channel and the RF link undergoes the Nakagami-m fading. We derived the analytical expression for cumulative distribution function (CDF) of equivalent signal-to-noise ratio (SNR). The novel mathematical presentations of outage probability and average bit-error-rate (BER) are developed based on the Meijer's G function. The analytical results show an accurately match to the Monte-Carlo simulation results. The outage and BER performance for the mixed system by decode-and-forward relay are investigated considering atmospheric turbulence and pointing error condition. The effect of aperture averaging is evaluated in all atmospheric turbulence conditions as well.

Symbol error rate performance analysis of soft-decision decoded MPPM free space optical system over exponentiated Weibull fading channels

The symbol error rate (SER) performance of a multipulse pulse-position modulation (MPPM) free space optical (FSO) system under the combined effect of turbulence-induced fading modeled by exponentiated Weibull (EW) distribution and pointing errors with a soft-decision detector is investigated systematically. Particularly, the theoretical conditional SER (CSER) of soft-decision decoded MPPM is derived. The corresponding closed-form CSER is obtained via curve fitting with the Levenberg–Marquardt method. The analytical SER expression over the aggregated fading channels is then achieved in terms of Laguerre integration. Monte Carlo simulation results are also offered to corroborate the validity of the proposed SER model.

Impact of nonzero boresight pointing errors on the performance of a relay-assisted free-space optical communication system over exponentiated Weibull fading channels.

The impact of nonzero boresight pointing errors on the system performance of decode-and-forward protocol-based multihop parallel optical wireless communication systems is studied. For the aggregated fading channel, the atmospheric turbulence is simulated by an exponentiated Weibull model, and pointing errors are described by one recently proposed statistical model including both boresight and jitter. The binary phase-shift keying subcarrier intensity modulation-based analytical average bit error rate (ABER) and outage probability expressions are achieved for a nonidentically and independently distributed system. The ABER and outage probability are then analyzed with different turbulence strengths, receiving aperture sizes, structure parameters (P and Q), jitter variances, and boresight displacements. The results show that aperture averaging offers almost the same system performance improvement with boresight included or not, despite the values of P and Q. The performance enhancement owing to the increase of cooperative path (P) is more evident with nonzero boresight than that with zero boresight (jitter only), whereas the performance deterioration because of the increasing hops (Q) with nonzero boresight is almost the same as that with zero boresight. Monte Carlo simulation is offered to verify the validity of ABER and outage probability expressions.

Outage performance of multihop free-space optical communication system over exponentiated Weibull fading channels with nonzero boresight pointing errors

The outage performance of the multihop free-space optical (FSO) communication system with decode-and-forward (DF) protocol is studied by considering the joint effects of nonzero boresight pointing errors and atmospheric turbulence modeled by exponentiated Weibull (EW) distribution. The closed-form analytical expression of outage probability is derived, and the results are validated through Monte Carlo simulation. Furthermore, the detailed analysis is provided to evaluate the impacts of turbulence strength, receiver aperture size, boresight displacement, beamwidth and number of relays on the outage performance for the studied system.

Multihop FSO Over Exponentiated Weibull Fading Channels With Nonzero Boresight Pointing Errors

The end-to-end (EE) average bit error rate (ABER) performance of a decode-and-forward-based multihop free-space optical communication system is investigated over composite exponentiated Weibull fading channels with nonzero boresight pointing errors considered. In particular, the cumulative distribution function of the aggregated fading channel for non-identically and independently distributed multihop system is derived. Then, the analytical expression of EE ABER with $M$ -ary phase shift keying subcarrier intensity modulation is achieved in terms of Gauss–Laguerre quadrature rule considering aperture averaging effect. The results show that the ABER performance is mainly limited by nonzero boresight pointing errors for larger receiver aperture size. The comparison with Monte Carlo simulation verifies the validity of the proposed ABER model.

BER Performance of FSO Limited by Shot and Thermal Noise Over Exponentiated Weibull Fading Channels

In this letter, the average bit error rate (ABER) performance of free-space optical links adopting $m$ -ary pulse-position modulation is investigated by considering the effects of both atmospheric turbulence and receiver noise. The atmospheric turbulence is modeled by exponentiated Weibull (EW) distribution with an aperture averaging effect taken into account. For the receiver noise, both shot- and thermal-noise-limited scenarios are studied and compared with log-normal and gamma–gamma distributions. For the shot-noise-limited system, an approximate expression for the ABER is obtained on the basis of the generalized Gauss–Laguerre quadrature rule. The union bound of ABER for the thermal-noise-limited system is also derived and verified by Monte Carlo simulation.

Performance Analysis for Relay-Aided Multihop BPPM FSO Communication System Over Exponentiated Weibull Fading Channels With Pointing Error Impairments

The performances of the decode-and-forward (DF) multihop free-space optical communication system with exponentiated Weibull distribution considering the fading induced by pointing error have been studied. With Meijer's G-function, the probability density function (PDF) of the aggregated channel model and the closed-form expression for the average bit error rate (ABER) of binary pulse position modulation are derived. The average bit-error-rate performance is then investigated with different hop numbers $H$ , turbulence strength values, receiver aperture sizes, beamwidths, and jitter variances. Compared with the case without pointing error, the mitigation effect of aperture averaging for fading is more significant over the aggregated channel, regardless of the selected $H$ , and it is less effective for the degradation induced by the increase in $H$ , which can be restrained by larger beamwidth and lower jitter. The outage probability is also investigated, and the results show that aperture averaging has less of an effect on the outage probability under moderate turbulence than that under the weak turbulence condition at a given value of $H$ , which is different from the scenario without pointing error. After this, the end-to-end average capacity is analyzed. Monte Carlo simulation is provided to confirm the validity of the proposed ABER expression.