System Average Bit Research Articles

Performance analysis of MRR FSO communication system under Gamma–Gamma​ turbulence channel with pointing error

The performance of modulating retro-reflector (MRR) free space optical (FSO) communication system has been studied before for various atmospheric turbulence conditions. However, the effect of pointing error (PE) on the MRR FSO communication system has not been studied yet. In this work, we investigate the PE impact on the MRR FSO communication system. Specifically, we obtain the probability density function (PDF) of the system in closed form expression regarding Gamma–Gamma turbulence channel and Rayleigh PE. Using this PDF, we derive the statistical characteristics closed form expressions of the received optical signal-to-noise ratio (SNR) including PDF, cumulative distribution function (CDF), moments and moment generating function (MGF). Relying on the obtained analytical results, we derive the system average bit error rate (BER), outage probability, ergodic capacity (EC) and amount of fading (AF) performances in closed forms. The closed form expressions are given in terms of Meijer’s G-function with the exception of obtaining the moments of the received optical SNR and AF in terms of elementary functions. For the given weather, PE and system conditions, we optimize the beam divergence angle to minimize the system average BER. Based on this, we suggest controlling of the beam divergence angle with the transmission distance according to the optimum beam divergence angle to improve the system BER performance. Finally we demonstrate the system performances according to the optimum beam divergence angle.

Performance analysis of modulating retro-reflector FSO communication systems over Málaga turbulence channels

In this work we present a unified performance analysis of bistatic modulating retro-reflector (MRR) communication systems for all turbulence regimes where the free space optical (FSO) link is modeled by the generalized Málaga distribution. In particular, we obtain closed-form expressions for probability density function (PDF) of the system fading channel as well as PDF, cumulative distribution function (CDF), moment generating function (MGF), and moments of the system received signal to noise ratio (SNR) using Meijer’s G function. Based on the conducted analysis, we derive exact closed form expressions for the system average bit error rate (BER), outage probability, ergodic capacity, and amount of fading (AF). The closed form expressions are obtained in terms of Meijer’s G function. Furthermore, asymptotic expressions of the system average BER and outage probability at high SNR values are presented in terms of simple elementary functions.

Performance of Generalized QAM/FSO Systems With Pointing Misalignment and Phase Error Over Atmospheric Turbulence Channels

This article investigates the performance of free-space optical (FSO) systems using sub-carrier quadrature amplitude modulation (SC-QAM) signaling for broadband terrestrial applications. While previous studies ignored the influence of phase noise, we theoretically analyze and derive closed-form expressions of the system's average bit error rate (ABER) considering the combined effect of pointing misalignment, turbulence-induced fading, and phase error. The log-normal distribution is used to model the atmospheric turbulence in the weak regime while the gamma-gamma distribution is applied for modeling the turbulent atmosphere in the moderate and strong regimes. The phase error, which becomes complicated under the effect of atmospheric turbulence, is modeled by Tikhonov distribution. The numerical results reveal that the influence of the phase error on the system performance is dominant in the weak turbulence and high order modulation while the fading becomes more severe in the moderate-to-strong turbulence regime. The accuracy of analytical results is also validated by Monte-Carlo simulations and a good match can be confirmed.

On the performance of transmit antenna selection in multiuser asymmetric RF/FSO system under generalized order user scheduling

In this paper, the performance analysis of transmit antenna selection on a multiuser asymmetric RF/FSO system under generalized order user scheduling is investigated. A dual-hop system with one source, one relay and multiple FSO users at destination is considered without direct link between the source and destination. The RF link is subjected to Nakagami-m fading and FSO links follow Exponential Weibull (EW) distribution. Using the amplify-and-forward (AF) channel-state-information (CSI) based gain relay protocol, the equivalent cumulative distribution function (CDF) end-to-end SNR at the destination is derived and used to obtain the analytical expression for the system outage probability. By utilizing the derived statistics, the closed-form expression for the system average bit error rate (ABER) is then derived through the Gauss–Laguerre quadrature rule and second kind Stirling number. Moreover, the results demonstrate that the atmospheric turbulence significantly degrades the system performance and increase in the number of source transmit antenna offers the system better performance. Also, the system performance is deteriorated by increasing the orders N or decreasing the number of user K. The accuracy of the derived expressions is validated through Montel-Carlo Simulations.

Performance of M-PAM FSO communication systems in atmospheric turbulence based on APD detector.

We characterize the performance of the optical signal propagation model of multi-level pulse amplitude modulation (M-PAM) based on avalanche photodiode (APD) detector in the free-space link for the first time. When the number of photons absorbed by the active surface of the APD is large enough, the bit error rate (BER) performance relationship of the systems based on the signal intensity and the photon characteristics are depicted. We use the Gamma-Gamma (G-G) channel model to analysis the communication systems with joint parameter constraints, and demonstrate the atmospheric turbulence intensity, link lengths, optical wavelength, symbol transmission rate, temperature of APD and pointing errors (PEs) impact on the system average bit error rate (ABER) performance. Moreover, the relationship between signal-to-noise-ratio (SNR) and ABER rate is given. The numerical results show that the 4-PAM free-space optical (FSO) communication is suitable for medium-to-weak turbulence, and the high gain of APD can mitigate the influence of ABER. The best detection condition of the 4-PAM optical signal is at least 20 dB SNR, when the ABER is under the 7% forward error correction (FEC) limit of 3.8 × 10-3. This work provides a reference for parameter designing and evaluating in M-PAM FSO communication systems.

Spatial Modulation via 3-D Mapping

This letter proposes a jointly mapped spatial modulation (JM-SM) scheme to break through the constraint on the number of transmit antennas in traditional SM systems. It is realized via jointly mapping the transmit information bits to 3-D constellation points. A 3-D constellation design scheme for a JM-SM is analyzed and established by minimizing the system average bit error probability (ABEP). In addition, the extension of the joint 3-D mapping to generalized spatial modulation is discussed. The simulation results show that the proposed schemes can be adapted to multiple-input multiple-output systems with an arbitrary number of transmit antennas and offer better ABEP performance than those existing schemes.

Performance Analysis of Multiple-Relay AF Cooperative Systems Over Rayleigh Time-Selective Fading Channels With Imperfect Channel Estimation

In this paper, the authors consider the adaptive-gain M -relay amplify-and-forward (AF) cooperative system with both conventional relaying (\cr), as well as a best-relay-selection (br) scheme, and investigate its performance over time-selective fading, due to nodes' mobility, in the presence of channel estimation errors. The authors first derive exact closed-form expressions for the destination's direct path and overall end-to-end instantaneous signal-to-noise ratios (SNRs). The authors also derive closed-form tight approximate expressions for the system average bit error rate, outage probability, and Shannon capacity, which are general functions of the cooperating nodes' relative speeds, in terms of the links' correlation parameters, the estimation errors' variances, and the receivers' tracking loops' channel estimation rates, in terms of the transmitted block length. The authors analysis reveals that due to the cooperating nodes' mobility, the system performance metrics are severely degraded and, in some particular network circumstances, experience asymptotic limits. In addition, when both of the source and the destination are static, the system performance does not experience asymptotic limits although the relays are in motion. On the other hand, despite that the relays are static, the mobility of either the source or the destination severely impacts the system performance by asymptotic limits, where the difference between their impacts depends on the symmetrical conditions of the network two-hop fading gain power. In addition, the authors found that the br provides higher asymptotic error limits than that of the /cr scheme. The authors also assured the special case when the network receivers are equipped with fast estimation loops and showed their effect of reducing the degradation impacts of the nodes' mobility. Simulation and numerical results are provided to verify the accuracy of the derived analytical expressions.

Star-QAM Signaling Constellations for Spatial Modulation

The performance of spatial modulation (SM)-assisted multiple-input-multiple-output (MIMO) communication systems is highly dependent on the specific amplitude/phase modulation (APM) signal constellation adopted. In this paper, we conceive new star-quadrature amplitude modulation (star-QAM)-aided SM schemes. Our goal is to minimize the system's average bit error probability (ABEP). More specifically, a new class of star-QAM constellations is introduced for SM, which is capable of flexibly adapting ring ratios of the amplitude levels. Then, under a specific MIMO configuration and a predetermined transmission rate, a simple and efficient ring-ratio optimization algorithm is proposed to minimize the ABEP. Moreover, to improve further the performance of our star-QAM-aided SM scheme, a diagonal precoding technique is proposed, and a low-complexity minimum-distance-based approach is conceived for extracting the precoding parameters. Our numerical results show that the proposed star-QAM-aided SM arrangement provides beneficial system performance improvements compared with the identical-throughput maximum-minimum distance (MMD) QAM and phase-shift keying (PSK) benchmarkers. Moreover, our precoding scheme is capable of further improving the attainable system performance at a modest feedback requirement.

Asynchronous direct‐sequence ultra‐wideband communication using spatiotemporal chaotic sequences

In this work, the authors address the effect of spreading sequences and pulse waveforms on the performance of asynchronous direct-sequence ultra-wideband systems. Regarding spreading sequences, they consider the two cases of short and long sequences. The expression of the multi-user interference (MUI) variance is derived using long sequences at the output of a rake receiver, when propagating through multipath channels. The authors also propose the use of sequences generated with a family of spatiotemporal chaotic systems, namely piecewise coupled map lattices (PCML), as spreading sequences. Such sequences are shown to reduce the MUI variance with regard to independent identically distributed and Gold sets for both short and long sequences. Simulation results show that the use of long PCML codes in additive white Gaussian noise and multipath fading channels results in an improvement of the system average bit error rate, hence an increase of the system capacity in terms of number of active users.