Subcarrier PSK Performance in Terrestrial FSO Links Impaired by Gamma-Gamma Fading, Pointing Errors, and Phase Noise

For terrestrial free-space optical (FSO) communication systems, subcarrier intensity modulation represents an attractive alternative to on-off keying or pulse-position modulation, which is mainly because of the larger spectral efficiency. However, some degradation of the error performance must be taken into account due to nonperfect synchronization of carrier frequency and phase. In a recently published paper, the average bit error probability has been analyzed for M-ary phase-shift keying in the presence of phase noise for a terrestrial FSO link impaired by lognormal fading. In the this paper, we are extending this study to a gamma-gamma model, which is usually applied in case of moderate-to-strong scintillation effects. On top of that, pointing errors, caused by a misalignment between transmitter and receiver of the FSO link, are considered as well. Since a closed-form solution is not available under general conditions and because numerical methods are time-consuming, suffering in part also from serious convergence and stability problems, we provide approximate closed-form expressions, which are accurate enough over a wide signal-to-noise ratio range. © 2017 IEEE

Simo subcarrier psk fso links with phase noise and non-zero boresight pointing errors over turbulence channels

Terrestrial free-space optical (FSO) communication systems with subcarrier intensity modulation have experienced a particular research attention in the recent past. However, their performance strongly degrades in the presence of atmospheric turbulence, pointing errors, and phase noise impairments. In order to overcome these limitations, the authors consider a receiver diversity scheme of a typical subcarrier phase-shift keying (PSK) system and investigate the performance by means of the average symbol error probability (ASEP). They assume a wide range of turbulence conditions, non-zero boresight pointing errors, and phase noise strengths described through the gamma-gamma, Beckmann, and Tikhonov distributions, respectively. Novel approximate ASEP expressions are derived for single-input single-output and single-input multiple-output (SIMO) configurations. Appropriate numerical results are depicted and validated by Monte Carlo simulations. © The Institution of Engineering and Technology 2019

Exact Analysis of Different Detector Algorithms for NDA Carrier Phase Recovery of 16-APSK Signals

In the new digital video broadcasting standard for satellite communications (DVB-S2), 16-ary amplitude-phase shift keying (APSK) is recommended as modulation scheme. For carrier phase recovery with feedback loops, deci-sion-directed (DD) and non-data aided (NDA) detector algo-rithms are basically applicable to 16-APSK schemes as well. In a recent paper, however, a hybrid NDA/DD solution has been suggested although not analyzed in detail. Motivated by this fact, the latter is investigated in terms of detector characteris-tic (S-curve) and jitter variance as the main figures of merit in this respect. For comparison purposes, results for power-law and monomial-based Viterbi and Viterbi trackers, as classical NDA solutions, are also included

Extended Gardner Detector for Improved Symbol-Timing Recovery of M-PSK Signals

In a recent paper, the modified Gardner detector has been proposed for advanced symbol-timing recovery of M-ary phase-shift keying signals. Compared with the original algorithm, the self-noise jitter can be considerably reduced for highly bandlimited systems and smaller values of . In this letter, a completely different approach is investigated, which improves the self-noise performance for larger values of M, as well

Transmission Systems Exact analysis of different detector algorithms for NDA carrier phase recovery of 16/32-APSK signals

In the new digital video broadcasting standard for satellite communications (DVB-S2), 16- and 32-ary amplitude-phase shift keying (APSK) are recommended as complementary modulation schemes to 4-PSK and 8-PSK. For carrier phase recovery with feedback loops, decision-directed (DD) and non-data-aided (NDA) detector algorithms are basically applicable. In some recent papers, however, a hybrid NDA/DD solution has been suggested for this purpose, although not analysed in detail. Motivated by this observation, the hybrid algorithms are investigated in this paper in terms of detector characteristic (S-curve) and jitter variance as the main figures of merit in this respect, with an additional design parameter introduced for optimisation. For comparison reasons, results for power-law and monomial-based Viterbi and Viterbi (V & V) trackers, as classical NDA solutions, are derived as well

Pointing errors influence at the performance of a multi-hop terrestrial FSO link emulated by a dual-hop scheme

The last years, FSO technologies raised interest from both scientific and commercial point of view. However, due to the optical beam propagation through the atmosphere, the signal is impaired by several phenomena like the scintillation effect, mainly because of atmospheric turbulence and imperfect misalignment between optical beam and destination terminal. In order to mitigate their negative influence, various countermeasures have been proposed. A well-known technique to preserve their performance over long distances is the employment of decode-and-forward (DF) relay nodes. Nevertheless, when the signal propagates over composite channels, characterized by atmospheric turbulence along with pointing errors effects, the employment of several DF relays increases significantly the complexity of the mathematical models used for performance evaluation. Motivated by this, we are trying to reduce the complexity of these expressions in the current work by replacing the multi-hop relay configuration via an equivalent dual-hop scheme. For first time, to the best of our knowledge, we are trying to emulate such an FSO system taking into account the simultaneous influence of both, atmospheric turbulence and pointing errors effects, in order to derive closed form mathematical expressions, which can be used in practice for the design of very fast optical wireless communication systems which can be used in the 5G/5G+ networks, mainly as backhaul communication links and support reliable their operation. © 202

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. © 2018 by the authors

Simo subcarrier psk fso links with phase noise and non-zero boresight pointing errors over turbulence channels

Terrestrial free-space optical (FSO) communication systems with subcarrier intensity modulation have experienced a particular research attention in the recent past. However, their performance strongly degrades in the presence of atmospheric turbulence, pointing errors, and phase noise impairments. In order to overcome these limitations, the authors consider a receiver diversity scheme of a typical subcarrier phase-shift keying (PSK) system and investigate the performance by means of the average symbol error probability (ASEP). They assume a wide range of turbulence conditions, non-zero boresight pointing errors, and phase noise strengths described through the gamma-gamma, Beckmann, and Tikhonov distributions, respectively. Novel approximate ASEP expressions are derived for single-input single-output and single-input multiple-output (SIMO) configurations. Appropriate numerical results are depicted and validated by Monte Carlo simulations. © The Institution of Engineering and Technology 2019

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. © 2018 by the authors