Lognormal Channels Research Articles

On the Optimality of Inverse Gaussian Approximation for Lognormal Channel Models

On the Optimality of Inverse Gaussian Approximation for Lognormal Channel Models

Pulse Jamming in PLC Over Log-Normal Channel Gain With Bernoulli-Gaussian Additive Noise

Pulse Jamming in PLC Over Log-Normal Channel Gain With Bernoulli-Gaussian Additive Noise

A Secure Optical Body Area Network Based on Free Space Optics and Time-Delayed 2D-Spectral/Spatial Optical CDMA

Free space optics (FSO)-based optical body area networks (OBANs) are receiving massive attention as an opportunity to address the limitations of their radio frequency (RF)-based counterparts. This boom in research interests is primarily due to multitude of benefits, including high capacity, immunity to electromagnetic interference (EMI), rapid installation, cost efficiency, and license-free use of spectrum. Securing the transmission of patient health data against interception in OBANs using insecure FSO channels is a challenging task. Therefore, we propose a low-cost, flexible, and secure OBAN based on FSO technology and a time-delayed two dimensional (2D) spectral/spatial optical code-division multiple access (OCDMA) system. The proposed architecture consists of eight sensors attached to the bodies of patients. The sensors operate at a rate of 50 kbps. Electrical data generated from each sensor are used to modulate an optical carrier and then encoded using 2D-spectral/spatial double weight–zero cross correlation (DW-ZCC) code. The 2D encoded optical signals are then time delayed to eliminate the multiple parallel FSO channels between the transmitter and medical center. The combined optical signal consists of eight 2D-encoded time-delayed optical signals transmitted towards a remote medical center over an FSO channel with a range of 1 km. The received signal is decoded and the data from each sensor are recovered after photodetection at the medical center for further analysis. The overall performance of the sensors is analyzed using bit-error rate (BER) and quality factor (Q-factor) plots for different weather conditions and lengths of the FSO channel, considering the log-normal channel model. The capital expenditure (CAPEX) of the proposed architecture is analyzed and compared with the conventional 2D-spectral/spatial FSO system to determine the overall impact of introducing time delay units on the cost of implementation.

Bootstrapped low complex iterative LDPC decoding algorithms for free-space optical communication links

In recent years, much research has been devoted to free-space optical communication (FSO). The unregulated spectrum, low implementation costs, and robust security of FSO systems all are of great importance which lead to a wide range of applications for FSO links, from terrestrial communications to satellite communications. However, the fundamental limitation with FSO links is atmospheric turbulence (AT) caused by fading, significantly reducing link performance. Random phenomena are the best characteristic of atmospheric turbulence caused by changes in the air’s refractive index over time. Numerous probability density functions of the AT models were presented to model the randomness in AT channels. The Log-Normal (LN) channel model is for weak atmospheric turbulence, while the Gamma–Gamma (G–G) channel is selected for moderate and strong atmospheric turbulence. The impacts of geometric losses, attenuation due to weather, and errors due to misalignment are addressed using LN and G–G channels. Channel coding is one of the possible solutions for mitigating such FSO channel impairments as the low-density parity check (LDPC) codes. In this article, the Weighted Bit Flipping (Algorithm (1)), Implementation Efficient Reliability Ratio Weighted Bit Flipping (Algorithm (2)), and Min-Sum (Algorithm (3)) algorithms are compared and evaluated against FSO atmospheric turbulence channels. In addition, two novel algorithms are proposed to enhance the complexity or Bit Error Rate performance of LDPC decoding over FSO channels. The results showed an impressive improvement of the coded FSO system by employing the proposed algorithms compared to the existing LDPC decoders for FSO communications from the point of all comparison parameters.

Intelligent Reflecting Surfaces for Underwater Visible Light Communications

Intelligent reflecting surfaces (IRSs) offer paradigm shift towards enhancing the capabilities of wireless communications. The use of this emerging technology in the realm of underwater wireless systems is a promising solution to overcome the limitations pertinent to such challenging environments. In this paper, we quantify the performance enhancement offered by the integration of IRS technology in the context of underwater optical wireless communication (OWC). Specifically, we derive a closed-form expression for the outage probability over log-normal channels, taking into consideration the underwater attenuation, pointing error, and turbulence effects. The underwater turbulent medium is characterized by the recently introduced Oceanic Turbulence Optical Power Spectrum (OTOPS) model that uses the practical values of average temperature and salinity concentration in earth basins. The presented numerical results take into account the effects of the turbulent medium as well as the communication system parameters (i.e., communication range, receiver aperture diameter, number of IRS). Our results show that IRSs can offer significant enhancement in the reliability of underwater OWC systems under attenuation, beam displacement, and turbulence effects. Moreover, the combined effect of using a large number of reflecting surfaces and a larger aperture diameter yields a more noticeable improvement.

Performance analysis of hybrid free space optical and visible light communications for underwater applications using spatial diversity

In this paper, we analyze a combination based on a hybrid triple hop terrestrial free-space optical (FSO), a fiber optic cable (FOC), and an underwater optical wireless communication (UOWC) link for providing high-speed optical connectivity between onshore and submerge systems. UOWC, scattering, absorption, and turbulence severely degrade the reliability and transmission rate of the UOWC link. In our manuscript, a bend-insensitive intermediate FOC link and a spatial diversity (SD) are exploited to improve the error performance of UOWC links, which involves the deployment of multiple input single outputs (MISO). For this purpose, different transmission signaling schemes, such as pulse position modulation (PPM) with spatial modulation (SM) and on–off keying (OOK) with repetition coding (RC), are employed to evaluate the system performance in terms of average bit error rate (ABER). The behavior of the entire system is obtained by applying a decode-and-forward (DF), where we consider log-normal channels for FSO and UOWC. The path loss and turbulence are obtained using intensity modulation and direct detection schemes. To obtain performance results, Monte Carlo-based statistical simulation method is applied to validate the analytical ABER performance of the system. The achieved results reveal that MISO-OOK-RC has superior ABER performance as compared to MISO-PPM-SM in higher signal-to-noise ratio (SNR) conditions with different underwater turbulence strengths.

Overall outage event of self-sustaining low-power cooperative relaying networks

This paper investigates the implementation of the household low-power energy harvesting (LoPEH) wireless sensor networks (WSN) over log-normal fading channels. The relays are battery-operated and the stochastic harvested energy flow to the batteries is characterized with the Markov property of energy buffer status. The communication is established with the combination of direct link and cooperative relays. The best relay is chosen based on a relay selection (RS) scheme namely optimal relay selection (OPRS). It can be drawn that within a particular range of signal-to-noise ratio (SNR), the energy harvesting (EH) relay-aided protocol can remarkably boost the overall system performance. On the other hand, the study reports how increasing the log-normal channel variance can degenerate the in-studied EH relaying protocol.

Non-Orthogonal Multiple Access-Based Underwater VLC Systems in the Presence of Turbulence

The promising potential of underwater applications in visible light communication (VLC) systems has recently gained considerable research attention, as an efficient technology for enabling high data rate, massive connectivity, and ultra-low latency. Different from indoor VLC, underwater wireless communications experience harsh environmental challenges, yielding a degraded performance. Non-orthogonal multiple access (NOMA) was introduced to enhance spectral efficiency and connectivity of underwater VLC communications. In this paper, we develop a mathematical framework to evaluate the performance of NOMA-enabled underwater VLC systems in the presence of turbulence. Specifically, we derive a closed-form expression for the outage probability of NOMA over lognormal channels, while considering the effect of path loss and turbulence. The derived analytical results with the corresponding numerical results demonstrate that the transmission distance between laser diode and sensor nodes (SNs) has a high impact on the outage performance of the SNs, due to the increased turbulence level with increased distance. Moreover, the presented results show the effect of the water type on the outage performance of the SNs and on the optimum values of the power coefficients.

Adaptive optics compensation of M-ary pulse position modulated communication systems in anisotropic non-Kolmogorov turbulent atmosphere

Adaptive optics compensation effect on the performance of an optical wireless communication system (OWC) employing M-ary pulse position modulation (PPM) scheme in anisotropic non-Kolmogorov turbulent atmosphere is investigated. Avalanche photodetector (APD) is used at the receiver side and log-normal channel that models the weak turbulence conditions is utilized. Anisotropy, generally resulting in better performance in OWC systems operating in the turbulent medium, combined with the adaptive optics applications will enhance the bit-error-rate (BER) of the OWC systems significantly. Results are obtained depending on various parameters for both the turbulent atmosphere and the receiver. Our work gives OWC system designers a perspective to optimize their design.

Integrating ultra-wideband and free space optical communication for realizing a secure and high-throughput body area network architecture based on optical code division multiple access

Nodes in a body area network (BAN) are miniature wearable or implantable battery-powered wireless sensors which continuously transmit real-time vital physiological data of a patient to remote health-care center while remaining in close proximity to the human body. Therefore, BAN nodes should have the features of high data rates and low transmit powers to protect the human body, environment and bio-medical equipment from harmful exposure of electromagnetic radiations and electromagnetic interference (EMI). Ultra-wideband (UWB) signals have low allowable transmission power and high data rates. Therefore, we propose a low cost, low powered and secure optical body area network (OBAN) composed of four UWB-BAN nodes each transmitting at a data rate of 30 Mbps. At the control node, UWB signals from UWB-BAN nodes are encoded using spectral amplitude coding-optical code division multiple access (SAC-OCDMA) scheme and the combined signal is transmitted over free space optics (FSO) channel towards remote health-care center. At the health-care center, the combined signal is decoded and UWB signal of each UWB-BAN node is photo-detected for analysis of patient’s data. Log-normal channel model is considered between control node and the health-care center. The signal received from each UWB-BAN after propagation through the FSO channel is analyzed through Bit error rate (BER) results. Similarly, cost efficiency of the proposed architecture is also evaluated through a detailed cost analysis. It was observed that the proposed architecture requires the UWB-BAN nodes to have low receiver sensitivities with the added benefits of cost-efficiency and data security.

Transceiver design for MU‐SIMO FSO communication over correlated lognormal channels

In this paper, with the assumption of only channel statistics information available at the receivers, a novel concept of multiplicative uniquely decomposable constellations is proposed for multi-user single-input multiple-output (MU-SIMO) FSO systems in weak atmospheric turbulence, which is modeled by spatially dependent lognormal fading channels. The design enables the fast decoding at the users' sides and meanwhile allows flexibility in assigning each user's ordering to meet different priority needs. Simulation results show that our proposed design has a significant performance improvement over the TDMA scheme at the same rates.

Threshold-based Wireless-based NOMA Systems over Log-Normal Channels: Ergodic Outage Probability of Joint Time Allocation and Power Splitting Schemes

Due to the development of state-of-the-art fifth-generation communication (5G) and Internet-of-Things (IoT), the demands for capacity and throughput of wireless networks have increased significantly. As a promising solution for this, a radio access technique, namely, non-orthogonal multiple access (NOMA) has been investigated. Particularly, in this paper, we analyse the system performance of a joint time allocation and power splitting (JTAPS) protocol for NOMA-based energy harvesting (EH) wireless networks over indoor scenarios, which we modelled with log-normal fading channels. Accordingly, for the performance analysis of such networks, the analytical expression of a metric so-called “ergodic outage probability” was derived. Then, thanks to Monte Carlo simulations done in Matlab, we are able to see how different EH power splitting (PS) and EH time switching (TS) factors influence the ergodic outage probability. Last, but not least, we plot the simulation results along with the theoretical results for comparison studies.

Centroid Error Analysis of Beacon Tracking under Atmospheric Turbulence for Optical Communication Links

Optical satellite communication has received considerable attention as a promising alternative to radio frequency communication because of its potential advantages including higher data rates and license free spectrum. Many studies have conducted performance analyses of optical communication channels, but few have investigated beacon tracking channels under atmospheric turbulence. The centroid accuracy of beacon tracking channels is limited by not only noise sources, but also a finite delay time, which also fluctuates due to atmospheric turbulence. Consequently, the centroid error is an important figure of merit when evaluating the performance of a beacon tracking system. In this study, the closed-form expressions were derived for average centroid error and fade probability, based on received photoelectron counts depending on exposure time, taking into account the log-normal tracking channels. We analyzed the angular positioning performance of beacon tracking detectors onboard small satellites in the presence of atmospheric turbulence, in terms of centroid error and fade probability. We found that an optimal exposure time exists, which minimizes the centroid error, and that fade probability is inversely proportional to the exposure time. These are significant properties to consider in the design of beacon tracking systems.

Self restorable intra data center interconnect based on multimode fiber and free-space optics

We demonstrate a high data rate and low-cost OM4 multimode fiber (MMF) and free-space optics (FSO)-based self-restorable 2 × 100 Gbps per wavelength intra data center interconnect between two pairs of servers. This transmission system is based on two vertical cavity surface-emitting lasers that are directly modulated with PAM-4 data at the rate of 100 Gbps and multiplexed using mode division multiplexing of two linearly polarized modes. In case a fault occurs in the MMF-based primary path, the traffic is shifted to FSO-based protection path through a specially designed triggering and switching mechanism. Offline digital signal processing is used at the receiver to process the received PAM-4 signal for compensating the effects of channel impairments. The performance of the proposed architecture is evaluated at link lengths of 35 and 70 m under normal and faulty scenarios. The effect of varying the refractive index structure parameter of the log-normal channel model and the effect of mode coupling between linearly polarized (LP) modes on the bit-error-rate performance is also analyzed under different conditions. We observe that the performance of the FSO-based protection path is better than the OM4-based primary path at a forward error correction limit of 3.8 × 10 − 3 bit-error-rate.

M-ary pulse position modulation performance with adaptive optics corrections in atmospheric turbulence

ABSTRACTThe performance of M-ary pulse position modulated (PPM) optical wireless communication (OWC) systems in atmospheric weak turbulence medium is evaluated by using adaptive optics corrections. Piston, tilt, defocus and coma components of adaptive optics corrections are applied to the avalanche photodetector (APD) type of receiver and the results are obtained depending on various turbulence and receiver parameters. The lognormal channel distribution is used to model the weak atmospheric turbulence conditions. Adaptive optics correction increases the bit-error-rate (BER) performance of an OWC system operating in atmospheric turbulence conditions. Piston component yields the highest BER performance, followed by the tilt, defocus and coma adaptive optics correction components respectively.

On the ASER performance of amplify-and-forward relaying MIMO/FSO systems using SC-QAM signals over log-normal and gamma-gamma atmospheric turbulence channels and pointing error impairments

ABSTRACT In this work, we analyse pointing error effects on the performance of amplify-and-forward (AF) relaying multiple-input multiple-output (MIMO) free-space optical (FSO) communication system employing sub-carrier quadrature amplitude modulation (SC-QAM) signal over log-normal and gamma-gamma distributed atmospheric turbulence channels. We study the pointing error effects by taking into account the influence of beam-width, aperture size and jitter variance on the average symbol error rate (ASER), which is derived in closed-form expressions of MIMO/FSO and SISO/FSO systems. In addition, the number of relaying stations is taken into account in the statistical model of the combined channel including atmospheric loss, atmospheric turbulence and pointing error impairments. The numerical results show that by combining AF relaying stations and MIMO/FSO configurations, the link length can be extended because the transmitted power is reduced according to the amplifier gain. Moreover, the performance of AF relaying MIMO/FSO systems is better than that of AF relaying SISO/FSO systems at the same link length.

UAV intelligent optical communication based on conditional generation against network

This paper first introduces the advancement and importance of laser communication technology for drones., then introduced Deep Neural Network (DNN) to develop wireless end-to-end communication systems. Accurate channel state parameters (CSI) are necessary for computing DNN, but in laser communication systems, channel information is difficult to gain in advance or changes quickly with time and environment. This paper will use conditional generation network (GAN) to represent channels. The coded signal of the transmitter and the pilot data are used as condition information. By simulating the simulation results of the lognormal channel, the method can achieve high-quality transmission without clear CSI.

On the performance of adaptive hybrid MQAM-MPPM scheme over Nakagami and log-normal dynamic visible light communication channels.

In this paper, we introduce the idea of using adaptive hybrid modulation techniques to overcome channel fading effects on visible light communication (VLC) systems. A hybrid $ M $M-ary quadrature-amplitude modulation ($ M{\rm QAM} $MQAM) and multipulse pulse-position modulation (MPPM) technique is considered due to its ability to make gradual changes in spectral efficiency to cope with channel effects. First, the Zemax optics studio simulator is used to simulate dynamic VLC channels. The results of Zemax show that Nakagami and log-normal distributions give the best fitting for simulation results. The performance of $ M{\rm QAM} $MQAM-MPPM is analytically investigated for both Nakagami and log-normal channels, where we obtain closed-form expressions for the average bit-error rate (BER). The optimization problem of evaluating the hybrid modulation technique settings that lead to the highest spectral efficiency under a specific channel status and constraint of outage probability is formulated and solved using an exhaustive search. Our results reveal that the adaptive hybrid scheme improves system spectral efficiency compared to ordinary QAM and MPPM schemes. Our results reveal that the adaptive hybrid scheme improves system spectral efficiency compared to ordinary QAM and MPPM schemes. Specifically, at low average transmitted power, $ - 32\;{\rm dBm} $-32dBm, the adaptive hybrid scheme shows 280% improvement in spectral efficiency compared to adaptive versions of ordinary schemes. At higher power, $ - 20\;{\rm dBm} $-20dBm, 6.5% and 725% improvement are obtained compared to ordinary QAM and ordinary MPPM, respectively. Also, the adaptive hybrid scheme shows great improvement in average BER and outage probability compared to ordinary schemes. The hybrid scheme shows 28%, 34%, and 38% improvement, respectively, for $ m = 1,2,3 $m=1,2,3 for Nakagami channels at $ {\rm BER}{ = 10^{ - 3}} $BER=10-3. Also, the outage probability of hybrid schemes of $ {\rm BER}{ = 10^{ - 3}} $BER=10-3 shows 30% and 14% better performance than ordinary $ M{\rm QAM} $MQAM and MPPM schemes, respectively.

Two-Way Relaying Non-Orthogonal Multiple Access With Imperfect Successive Interference Cancellation in Power Line Communications

In this article, we study the application of cooperative non-orthogonal multiple access (NOMA) in power line communication (PLC) where two users exchange information using a two-way relay (TWR). Under the assumption of perfect and imperfect successive interference cancellation (SIC), we analyze key performance metrics for PLC log-normal channels impaired by impulsive noise. In particular, for delay-limited (DL) and delay-tolerant (DT) modes, approximate closed-form expressions are derived for the user outage probability and user ergodic rate. The analytic results are verified via Monte Carlo simulations. Compared with the conventional orthogonal multiple access (OMA) scheme, the simulation results show that our proposed NOMA TWR enhances the user outage probability and the user ergodic rate performance in the low signal-to-noise ratio (SNR) region. However, this gain diminishes as the imperfect SIC error increases and is non-existent beyond a certain level of imperfect SIC. Furthermore, the system performance is maximized by optimizing the power allocation coefficients where the system throughput and ergodic sum-rate of the NOMA TWR network in DL and DT operation, respectively, are shown to approach a ceiling in the presence of imperfect SIC. The energy efficiency (EE) of the proposed system is also analyzed for DL and DT modes.

Cooperative Non-Orthogonal Multiple Access over Log-Normal Power Line Communication Channels

In this paper, we analyze the performance of cooperative power domain non-orthogonal multiple access (NOMA) in power line communication (PLC) networks. Due to the high signal attenuation of the source to user links, a relay aids communication from the source to two users. With half-duplex transmission, the source transmits a superimposed symbol in the first phase. The relay utilizes amplify-and-forward (AF) and decode-and-forward (DF) protocol on the received superimposed signal and forwards it to the users in the second phase. We derive analytic expressions for the outage probability and the system throughput of the proposed system under a PLC log-normal channel with impulsive noise. Based on the results for AF NOMA relaying case, we analyze the system performance at high signal-to-noise ratio (SNR) and derive closed-form lower and upper bounds for the outage probability. Simulation results show an improvement in the outage probability and the system throughput performance of the AF and DF NOMA schemes compared to the NOMA without relaying transmission and conventional orthogonal multiple access scheme. Furthermore, the impact of the channel variance is highlighted in the results. It is shown that the DF NOMA has a better outage probability than the AF NOMA scheme for low channel variance scenarios (i.e., less branches and connected loads in the PLC network). However, as the channel variance increases, AF NOMA scheme has similar outage probability performance as the DF NOMA scheme. In addition, it is shown that the system throughput is enhanced when the relay employs DF relaying compared to AF relaying.