Nonzero Boresight Pointing Errors Research Articles

Correction to “Dual-Hop RF/FSO Systems Over $\kappa$-$\mu$ Shadowed and Fisher-Snedecor ${\mathcal F}$ Fading Channels With Non-Zero Boresight Pointing Errors” [Feb 22 708-719

Here, we correct the mistakes about citations in our article [1]. This has no effect on the results and conclusions. The correct citation numbers are given here.

Dual-Hop RF/FSO Systems Over $\kappa$-$\mu$ Shadowed and Fisher-Snedecor ${\mathcal F}$ Fading Channels With Non-Zero Boresight Pointing Errors

We investigate the performance of a dual-hop mixed radio frequency (RF)/free space optical (FSO) system with variable-gain relaying. The RF link is modeled by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\kappa$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> shadowed distribution, which unifies popular RF channel models. The FSO link is subject to atmospheric turbulence with non-zero boresight pointing errors. The atmospheric turbulence channel is modeled by the Fisher-Snedecor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathcal F}$</tex-math></inline-formula> distribution, which fits well with the measurement data under weak-to-strong turbulence conditions. The pointing error is modeled by the Beckmann distribution, which includes popular pointing error models. We propose an approximation method to approximate the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\kappa$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> shadowed distribution using an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> distribution, which is more accurate than that using a gamma distribution in the existing literatures. Then, we derive closed-form expressions for the probability density function (PDF) and the cumulative distribution function (CDF) for the irradiance fluctuations. Based on these expressions, we derive closed-form approximate expressions for the CDF, the PDF, the moment generating function (MGF), the average bit error rate (BER), and the ergodic capacity (EC) of the considered system in terms of the bivariate Fox’s H function. Furthermore, asymptotic expressions for the CDF and the average BER at high signal-to-noise ratio (SNR) are derived in terms of simple elementary functions. Finally, numerical results and Monte Carlo (MC) simulations are provided to verify the derived approximate expressions.

Combining Power Allocation and Superposition Coding for an Underlay Two-way Decode-and-forward Scheme

Combining Power Allocation and Superposition Coding for an Underlay Two-way Decode-and-forward Scheme

Channel Modeling for UAV-Based Optical Wireless Links With Nonzero Boresight Pointing Errors

The channel modeling of unmanned aerial vehicle (UAV)-based free-space optical (FSO) links with nonzero boresight pointing error is the subject of this paper. In particular, utilizing log-normal turbulence model, we propose a novel closed-form statistical channel model for UAV-based FSO links that takes into account the effect of nonzero boresight pointing errors. Subsequently, utilizing Gamma-Gamma turbulence model, we propose a novel channel characterization for such links that is valid under moderate to strong turbulence conditions. The accuracy of the proposed models is verified via Monte-Carlo simulations. The proposed models are more tractable and suitable for analysis of such UAV-based FSO links.

Outage Capacity of Rate-Adaptive Relaying for FSO Links With Nonzero Boresight Pointing Errors

An outage capacity analysis of a three-way free-space optical (FSO) setup based on the optical path selection, either source-destination (S-D) or source-relay-destination (S-R-D), with a greater value of channel gain along with the use of repetition coding (RC) is analyzed over atmospheric turbulence channels with nonzero boresight pointing errors. The developed expression, which is validated through Monte Carlo simulation, is used to carefully analyze the performance and design of rate-adaptive relaying FSO systems from an information theory point of view. It is highlighted that a greater outage diversity is achieved by the obtained results without investing in extra hardware at the expense of an information rate reduction.

SIMO Subcarrier PSK FSO Links with Phase Noise and Nonzero Boresight Pointing Errors over Turbulence Channels

SIMO Subcarrier PSK FSO Links with Phase Noise and Nonzero Boresight Pointing Errors over Turbulence Channels

Exact and Asymptotic Analysis of Partial Relay Selection for Cognitive RF-FSO Systems With Non-Zero Boresight Pointing Errors

In this paper, we investigate the performance of asymmetric radio frequency (RF) and free space optical (FSO) dual-hop cooperative relay network along with a direct RF link between source and destination. The FSO link experiences double generalized Gamma turbulence in the presence of the generalized non-zero boresight pointing errors, and RF links experience non-identically distributed Nakagami-m fading. Moreover, considering both cognitive radio and non-cognitive scenarios, a partial relay selection (PRS) strategy has been employed. Furthermore, both relay selection and underlay power restriction are governed with the outdated channel state information (CSI). We also assume both heterodyne and intensity modulation/direct detection methods in the FSO receiver. Under the assumption of amplify-and-forward relaying and PRS, we derive closed-form expressions for outage probability (OP) of both scenarios, while bit-error probability and ergodic capacity of the non-cognitive scenario are also obtained. The asymptotic expressions of OP and diversity order of this network are derived for both perfect CSI and outdated CSI cases. It is demonstrated that the diversity order is a function of the fading severity of the RF links, turbulence parameters of the FSO link, and pointing error, regardless of interference channel parameter of the primary user.

Spatial Diversity for CDMA RoFSO Links over M Turbulence Channels with Nonzero Boresight Pointing Errors

A CDMA RoFSO link with receivers’ spatial diversity is studied. Turbulence-induced fading, modeled by the M(alaga) distribution, is considered that hamper the FSO link performance along with the nonzero boresight pointing errors effect. Novel, analytical closed-form expressions are extracted for the estimation of the average bit-error-rate and the outage probability of the CDMA RoFSO system for both directions of the forward and the reverse link. The numerical results show clearly the performance improvement of using spatial diversity, even in the most adverse atmospheric conditions with strong and saturated atmospheric turbulence with enhanced misalignment. Also, the effects of nonlinear distortion, multiple access interference and clipping noise aggravate the performance of the link, where cases with large number of users are taken into account.

Asymptotic Performance Analysis of Two-Way Relaying FSO Networks With Nonzero Boresight Pointing Errors Over Double-Generalized Gamma Fading Channels

In this correspondence, an asymptotic performance analysis for two-way relaying free-space optical (FSO) communication systems with nonzero boresight pointing errors over double-generalized Gamma fading channels is presented. Assuming amplify-and-forward relaying, two nodes having the FSO ability can communicate with each other through the optical links. With this setup, we derive some asymptotic analytical results for the outage probability and average bit error rate. Furthermore, we provide an asymptotic average capacity analysis for high signal-to-noise ratio by using the moments-based method.

DF Relayed Subcarrier FSO Links over Malaga Turbulence Channels with Phase Noise and Non-Zero Boresight Pointing Errors

Subcarrier free-space optical (FSO) systems using coherent recovery techniques at the receiver have acquired growing research interest in recent times. However, their optimal performance is diminished by the non-perfect synchronization of carrier frequency and phase, which is mainly due to phase noise problems. Moreover, turbulence and pointing error effects further deteriorate the overall performance. However, relay transmission schemes can extend the coverage distance and offer substantial improvements over fading conditions. In this respect, we consider a serially relayed network using decode-and-forward relays, and investigate its performance by means of average symbol error probability and mean outage duration. Turbulence is modeled by the recently unified M(alaga) distribution, which constitutes a very general statistical model that accurately describes the irradiance fluctuations from weak-to-strong turbulence conditions. Additionally, the presence of non-zero boresight pointing errors due to misalignment between the transmitter–receiver pair is considered, while the effect of phase noise is specified by a Tikhonov distribution. A comparison between single line-of-sight and serially relayed FSO configurations is provided as well. Novel approximated mathematical expressions are deduced, which are proved to be accurate enough over a wide range of turbulence strengths and signal-to-noise values. Finally, proper numerical results are presented and validated by Monte Carlo simulations.

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.

OFDM RoFSO Links with Relays Over Turbulence Channels and Nonzero Boresight Pointing Errors

OFDM RoFSO Links with Relays Over Turbulence Channels and Nonzero Boresight Pointing Errors

OFDM RoFSO Links with Relays Over Turbulence Channels and Nonzero Boresight Pointing Errors

OFDM RoFSO Links with Relays Over Turbulence Channels and Nonzero Boresight Pointing Errors

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.

Ergodic Capacity Analysis of Free-Space Optical Links With Nonzero Boresight Pointing Errors

A unified capacity analysis of a free-space optical (FSO) link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. intensity modulation/direct detection as well as heterodyne detection) is addressed in this work. More specifically, an exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system is presented in terms of well-known elementary functions. Capitalizing on these new moments expressions, we present approximate and simple closed-form results for the ergodic capacity at high and low SNR regimes. All the presented results are verified via computer-based Monte-Carlo simulations.

Outage Analysis for Relay-Aided Free-Space Optical Communications Over Turbulence Channels With Nonzero Boresight Pointing Errors

Free-space optical (FSO) communications has recently received significant attention and commercial interest for a variety of applications. In this paper, the outage probabilities for both the parallel and serial relay-aided FSO communications are analyzed. Initially, a new aggregated channel fading model is established, which considers atmospheric attenuation, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">${\cal M}$</tex-math></inline-formula> -distributed atmospheric turbulence, and nonzero boresight pointing errors. After that, the statistical characteristic of the aggregated channel is analyzed. Under the aggregated channel model, closed-form expressions of the outage probabilities for both the parallel and serial relay-aided FSO communications are derived, respectively. Numerical results show that the derived theoretical expressions are quite accurate and can provide sufficient precision for evaluating the outage performance, which is helpful to the design of future FSO communication systems.

Free-Space Optical Communication with Nonzero Boresight Pointing Errors

The performance of free-space optical (FSO) communication systems is compromised by atmospheric fading and pointing errors. The pointing errors are widely considered as a combination of two components: boresight and jitter. A statistical model is investigated for pointing errors with nonzero boresight by taking into account the laser beamwidth, detector aperture size, and jitter variance. A novel closed-form probability density function (PDF) is derived for this new nonzero boresight pointing error model. Furthermore, we obtain closed-form PDF for the composite lognormal turbulence channels and finite series approximate PDF for the composite Gamma-Gamma turbulence channels, which is suitable for terrestrial FSO applications impaired by building sway. We conduct error rate analysis of on-off keying signaling with intensity modulation and direct detection over the lognormal and Gamma-Gamma fading channels. Asymptotic error rate analysis and outage probability of such a system are also presented based on the derived composite PDFs. It is shown that the boresight can only affect the coding gain, while the diversity order is determined by the atmospheric fading effect as well as the pointing error effect.