Cooperative Terrestrial-Underwater Wireless Optical Links by Using an Amplify-and-Forward Strategy

Jurado-Navas, Antonio; Álvarez-Roa, Carmen; Álvarez-Roa, María; Castillo-Vázquez, Miguel

doi:10.3390/s22072464

Cited by 9 publications

(14 citation statements)

References 68 publications

(86 reference statements)

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“…where W s ′ is the code weight, σ 2 N ′ is the AWGN generated solely in the OCDMA channel, and σ 2 represents the MAI variance. Next, and considering now the effect of the atmospheric turbulence, since the MAI term is affected by I , σ 2 (I ), then the SNIR in (2) can be approximated by averaging the noises over atmospheric turbulence in the way proposed in [30], [31] as…”

Section: A System Modelmentioning

confidence: 99%

Flexible Free-Space Optical CDMA Networks

Álvarez-Roa,

Raddo

et al. 2023

IEEE Access

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In this paper, we propose a novel hybrid network solution using optical code-division multipleaccess and free-space optics (OCDMA-FSO) to support multiple data rates and quality-of-service according to user requirements. The proposed OCDMA-FSO network classifies users into diverse classes based on their requirements and allows for signal transmission in a fully asynchronous manner. The new hybrid network employs 2-D OCDMA codes as well as a variable aperture FSO receiver together with an equal gain combining (EGC) technique. We derive completely new analytical formalisms to evaluate the network performance in terms of average bit error rate (ABER), outage probability, effective data rate during outages, and ergodic capacity. The derived ABER expressions are validated via Monte-Carlo simulations. These new analytical formalisms are derived considering several atmospheric turbulence conditions such as uncorrelated, totally correlated, and partially correlated turbulence. To model this atmospheric turbulence, we derive the gamma-gamma (GG) distribution, which allows us to consider both the scintillation effect and the EGC technique. Finally, we carry out a comprehensive performance evaluation of the proposed hybrid network. Analytical results show that as the number of FSO receiver apertures increases, there is an improvement in overall performance levels. However, the ergodic capacity exhibits minimal improvement even as the number of FSO receiver apertures increases, regardless of the user requirements and turbulence conditions. The proposed network is a potential solution for scenarios that demand flexibility in bandwidth and data rate allocation.

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Section: A System Modelmentioning

confidence: 99%

Flexible Free-Space Optical CDMA Networks

Álvarez-Roa,

Raddo

et al. 2023

IEEE Access

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“…A curve-fitting method is an alternative to derive the exact analytical expression of the conditional BER of MPPM-based systems [34,43]. A hyper-exponential fitting technique is applied to derive the closed-form approximation expression of the conditional BER in [34].…”

Section: Ber Performance Without the Fecmentioning

confidence: 99%

“…The Monte Carlo simulation is verified to ensure the correctness prior to fitting, which is presented in Section 5. Then, with the integration by parts, change of variables and Gauss-Laguerre quadrature formulation [43], we have:…”

Section: Ber Performance Without the Fecmentioning

confidence: 99%

The BER Performance of the LDPC-Coded MPPM over Turbulence UWOC Channels

Jiang

Liao

et al. 2022

Photonics

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Turbulence-induced fading is a critical performance degrading factor for underwater wireless optical communication (UWOC) systems. In this paper, we propose a quasi-cyclic (QC) low-density parity-check (LDPC) code with multiple-pulse-position modulation (MPPM) to overcome turbulence-induced fading. MPPM is adopted as a compromise between the low-power efficiency of on–off keying (OOK) and the low bandwidth efficiency of pulse position modulation (PPM). The bit error rate (BER) performance of LDPC-coded MPPM over turbulence UWOC channels is investigated. The log-likelihood ratio (LLR) of MPPM is derived, and a simplified approximation is used for iterative decoding. Subsequently, the closed-form expression of the BER, without forward error correction (FEC) code, is obtained for the generalized-gamma (GG) fading model. Finally, Monte-Carlo (MC) simulation results are provided to demonstrate the correctness of the derived closed-form expressions and the effectiveness of the LDPC code with simplified LLR to improve the BER performance for different MPPM formats over fading channels.

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“…Analogously, the fronthaul links between the BBU and the RRHs also require a connection between a FSO gateway and the mother NFP node. Certainly, many applications beyond classical mobile networks can benefit from the proposed scenario shown in Figure 1 since it can provide backhaul/fronthaul connectivity to 5G V2X, or even future underwater communications [ 11 , 12 , 13 , 37 ].…”

Section: System Modelmentioning

confidence: 99%

“…More importantly, FSO technology does not interfere with RF systems, which paves the way to mixed RF/FSO approaches where the optical links complement the existing RF infrastructure [ 5 , 6 ]. Due to all these benefits, FSO communications have found their place in diverse applications such as space communications [ 7 , 8 , 9 ], underwater communications [ 10 , 11 , 12 , 13 ], indoor local area networks [ 14 ], data center networks [ 15 ], and mobile backhaul [ 6 , 16 , 17 ].…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of a Vertical FSO Link with Energy Harvesting Strategy

Álvarez-Roa

Martín-Vega

et al. 2022

Sensors

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In this paper we investigate the application of free space optical (FSO) communications, energy harvesting, and unmanned aerial vehicles (UAVs) as key technology enablers of a cost-efficient backhaul/fronthaul framework for 5G and beyond (5G+) networks. This novel approach is motivated by several facts. First, the UAVs, acting as relay nodes, represent an easy-to-deploy and adaptive network that can provide line-of-sight between the base stations and the gateways connected to the core network. Second, FSO communications offer high data rates between the UAVs and the network nodes, while avoiding any potential interference with the 5G radio access networks. Third, energy harvesting in the optical domain has the potential to extend the UAVs’ battery life. Nevertheless, the presence of atmospheric turbulence, atmospheric attenuation, and pointing errors in the FSO links severely degrades their performance. For this reason an accurate yet tractable modelling framework is required to fully understand whether an UAV-FSO backhaul/fronthaul network with energy harvesting can be applied. To this end, we consider a composite channel attenuation model that includes the effect of turbulence fading, pointing errors, and atmospheric attenuation. Using this model, we derive analytical closed-form expressions of the average harvested energy as a function of the FSO link parameters. These expressions can be used to improve energy harvesting efficiency in FSO link design. We have applied our proposed expressions to evaluate the energy harvested in vertical FSO links for a variety of real scenarios under a modified on-off keying (OOK) scheme optimized for energy harvesting. From the simulations carried out in this paper, we demonstrate that significant values of harvested energy can be obtained. Such performance enhancement can complement the existing deployment charging stations.

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Cooperative Terrestrial-Underwater Wireless Optical Links by Using an Amplify-and-Forward Strategy

Cited by 9 publications

References 68 publications

Flexible Free-Space Optical CDMA Networks

Flexible Free-Space Optical CDMA Networks

The BER Performance of the LDPC-Coded MPPM over Turbulence UWOC Channels

Performance Analysis of a Vertical FSO Link with Energy Harvesting Strategy

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