Ergodic channel capacity of MIMO WOC systems over combined effects of correlated atmospheric turbulence channel with MPPM

2019 ◽  
Author(s):  
Yue Zhang ◽  
Huiqin Wang ◽  
Minghua Cao ◽  
Xia Zhang
Keyword(s):  
Atmospheric Turbulence ◽  
Channel Capacity ◽  
Combined Effects ◽  
Ergodic Channel Capacity

scholarly journals Modal coupling and crosstalk due to turbulence and divergence on free space THz links using multiple orbital angular momentum beams

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhe Zhao ◽  
Runzhou Zhang ◽  
Hao Song ◽  
Kai Pang ◽  
Ahmed Almaiman ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Atmospheric Turbulence ◽  
Channel Capacity ◽  
Orbital Angular Momentum ◽  
Beam Waist ◽  
Modal Coupling ◽  
Divergence Effect ◽  
Power Leakage ◽  
Calm Weather ◽  
Bad Weather

AbstractOrbital-angular-momentum (OAM) multiplexing has been utilized to increase the channel capacity in both millimeter-wave and optical domains. Terahertz (THz) wireless communication is attracting increasing attention due to its broadband spectral resources. Thus, it might be valuable to explore the system performance of THz OAM links to further increase the channel capacity. In this paper, we study through simulations the fundamental system-degrading effects when using multiple OAM beams in THz communications links under atmospheric turbulence. We simulate and analyze the effects of divergence, turbulence, limited-size aperture, and misalignment on the signal power and crosstalk of THz OAM links. We find through simulations that the system-degrading effects are different in two scenarios with atmosphere turbulence: (a) when we consider the same strength of phasefront distortion, faster divergence (i.e., lower frequency; smaller beam waist) leads to higher power leakage from the transmitted mode to neighbouring modes; and (b) however, when we consider the same atmospheric turbulence, the divergence effect tends to affect the power leakage much less, and the power leakage increases as the frequency, beam waist, or OAM order increases. Simulation results show that: (i) the crosstalk to the neighbouring mode remains < − 15 dB for a 1-km link under calm weather, when we transmit OAM + 4 at 0.5 THz with a beam waist of 1 m; (ii) for the 3-OAM-multiplexed THz links, the signal-to-interference ratio (SIR) increases by ~ 5–7 dB if the mode spacing increases by 1, and SIR decreases with the multiplexed mode number; and (iii) limited aperture size and misalignment lead to power leakage to other modes under calm weather, while it tends to be unobtrusive under bad weather.

scholarly journals Average Channel Capacity of Amplify-and-forward MIMO/FSO Systems Over Atmospheric Turbulence Channels

2018 ◽  
Vol 8 (6) ◽  
pp. 4334
Author(s):  
Duong Huu Ai
Keyword(s):  
Atmospheric Turbulence ◽  
Channel Capacity ◽  
Multiple Input Multiple Output ◽  
Mathematical Expression ◽  
Relay Channel ◽  
Free Space Optical ◽  
Amplify And Forward ◽  
Average Channel Capacity ◽  
Link Distance ◽  
Gamma Distributions

In amplify-and-forward (AF) relay channel, when the direct link between source and destination terminals is deeply faded, the signal from the source terminal to the destination terminal propagates through the relay terminals, each of which relays a signal received from the previous terminal to the next terminal in series. This paper, we theoretically analyze the performance of multiple-input multiple-output (MIMO) AF free-space optical (FSO) systems. The AF-MIMO/FSO average channel capacity (ACC), which is expressed in terms of average spectral efficiency (ASE) is derived taking into account the atmospheric turbulence effects on the MIMO/FSO channel. They are modeled by log-normal and the gamma-gamma distributions for the cases of weak-to-strong turbulence conditions. We extract closed form mathematical expression for the evaluation of the ACC and we quantitatively discuss the influence of turbulence strength, link distance, different number of relay stations and different MIMO configurations on it.

scholarly journals Performance Improvement for Mixed RF–FSO Communication System by Adopting Hybrid Subcarrier Intensity Modulation

2019 ◽  
Vol 9 (18) ◽  
pp. 3724 ◽  
Author(s):  
Jiang ◽  
Zhao ◽  
Liu ◽  
Deng ◽  
Luo ◽  
...  
Keyword(s):  
Atmospheric Turbulence ◽  
Channel Capacity ◽  
Communication System ◽  
Rayleigh Distribution ◽  
Intensity Modulation ◽  
Phase Shift Keying ◽  
Free Space Optical ◽  
Pointing Error ◽  
Shift Keying ◽  
Binary Phase Shift Keying

The improvement for hybrid radio frequency–free space optical (RF–FSO) communication system in wireless optical communications has acquired growing interests in recent years, but rarely improvement is based on hybrid modulation. Therefore, we conduct a research on end-to-end mixed RF–FSO system with the hybrid pulse position modulation–binary phase shift keying–subcarrier intensity modulation (PPM–BPSK–SIM) scheme. The RF link obeys Rayleigh distribution and the FSO link experiences Gamma–Gamma distribution. The average bit error rate (BER) for various PPM–BPSK–SIM schemes has been derived with consideration of atmospheric turbulence influence and pointing error condition. The outage probability and the average channel capacity of the system are discussed as well. Simulation results indicate that the pointing error aggravates the influence of atmospheric turbulence on the channel capacity, and the RF–FSO systematic performance is improved obviously while adopting PPM–BPSK–SIM under strong turbulence and severe pointing error conditions, especially, when the system average symbol length is greater than eight.

Capacity of Optical Wireless System over Log-Normal Channels with Spatial Diversity in Presence of Atmospheric Losses

2018 ◽  
Vol 39 (3) ◽  
pp. 349-357 ◽  
Author(s):  
Rahul Kaushik ◽  
Vineet Khandelwal ◽  
R.C. Jain
Keyword(s):  
Atmospheric Turbulence ◽  
Channel Capacity ◽  
Random Variable ◽  
Weather Conditions ◽  
Spatial Diversity ◽  
Closed Form Expression ◽  
Atmospheric Conditions ◽  
Optical Wireless ◽  
Diversity Techniques ◽  
Log Normal

Abstract In this paper, average channel capacity of optical wireless communication system is evaluated under the combined effect of geometrical loss, attenuation due to weather conditions and weak atmospheric turbulence using a simple closed form expression. Fading induced due to atmospheric turbulence is modeled by log-normal distribution. Considering the fact that the sum of log-normal random variables can be well approximated by another log-normal random variable, the proposed expression has been utilized to compute the channel capacity for spatial diversity reception employing maximum ratio combining and equal gain combining over uncorrelated turbulence-induced fading conditions. It is shown that spatial diversity is an effective technique to mitigate the impairments caused by various atmospheric conditions such as haze, rain and fog. The quantitative improvement in channel capacity achieved by using diversity techniques is investigated and compared. Accuracy of the results is validated with exact results computed using Monte Carlo simulation.

Performance Analysis of a STBC FDM FSO Communication System with Direct Detection Receiver under Turbulent Condition

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Bobby Barua ◽  
S. P. Majumder
Keyword(s):  
Atmospheric Turbulence ◽  
Channel Capacity ◽  
Communication System ◽  
Direct Detection ◽  
Weather Conditions ◽  
Optical Receiver ◽  
Communication Link ◽  
Link Distance ◽  
Receive Diversity ◽  
Turbulent Condition

AbstractWeather conditions are severely degraded the performance of FSO communication link. Atmospheric turbulence is one of the important weather conditions that degrade the performance even under clear sky condition. In this paper, we provide a noble analytical approach to evaluate the performance of STBC coded FDM FSO communication system with direct detection optical receiver under turbulent condition. Analysis is carried out to find the channel capacity of RF subcarrier modulation taking into consideration the effect of strong atmospheric turbulence which is modeled as gamma-gamma distribution and the probability density function of the conditional CNR, conditioned on a given turbulence-induced fading is derived considering equal gain receive diversity combining technique with direct detection optical receiver followed by RF synchronous demodulation. Results are evaluated numerically in terms of average CNR, BER and channel capacity for several system parameters like turbulence variance, link distance, data rate, etc.

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