Error mitigation using RaptorQ codes in an experimental indoor free space optical link under the influence of turbulence

Abstract

Abstract:In Free space optical (FSO) communications, several factors can strongly affect the link quality. Among them, one of the most important impairment that can degrade the FSO link quality and its reliability -even under the clear sky conditions -consists of optical turbulence. In this work, we investigate the generation of both weak and moderate turbulence regimes in an indoor environment to assess the FSO link quality. In particular, we show that, due to the presence of the turbulence, the link experiences both erasure errors and packet losses during transmission, and also compare the experimental statistical distribution of samples with the predicted Gamma-Gamma model. Furthermore, we demonstrate that the application of the RaptorQ codes noticeably improves the link quality decreasing the packet error rate (PER) by about an order of magnitude, also offering -in certain cases -an error free transmission with a PER of ~ 10 -2 at Rytov variance value of 0.5. The results show that the recovery rate increases with the redundancy, the packet length and the number of source packets, while decreases with increasing data rates.

The BER performance of a FSO system with polar codes under weak turbulence

“…In addition, to mitigate turbulenceinduced fading and, therefore, improve the links' bit error rate (BER) performance, various error control coding schemes have been proposed and investigated. FSO links with spacetime, repetition, and rate-less coding schemes have been reported in the literature [12][13][14]. A practical scheme of adaptive transmission has been considered to mitigate turbulenceinduced fading in FSO links to adjust parameters such as the transmit power, code rates and modulation schemes using the CSI received via the feedback path [11].…”

Adaptation of Mode Filtering Technique in 4G-LTE Hybrid RoMMF-FSO for Last-Mile Access Network

“…Higher data rate of 1.6 Tbps using a single FSO link was reported experimentally in [10]. The link performance of FSO systems are affected by the atmospheric channel conditions such as atmospheric absorption, scattering, and scintillation, which affect the transmission quality as well as the link availability [11,12]. Scintillation is a random phenomenon initiated by small temperature variations along the optical path, i.e., optical turbulence, thus leading to the refractive index and irradiance fluctuations [13].…”

“…In [14] several schemes have been introduced to combat turbulence induced fading effects. The impact of turbulence on the propagating optical beam can be evaluated using several statistical models including log-normal and gamma-gamma distribution model, which are adopted for weak and weak-strong turbulence regimes, respectively [12]. Here we have adopted log-normal model to experimentally assess the performance of proposed system under weak turbulence.…”

“…Further research works have considered mainly the atmospheric effects on the FSO link when using short length SMFs, but not the perturbing effects generated by MMF. In [12] experimental demonstration of the baseband signal transmission at 100 Mbps over a 1 m of MMF and a 2.5 m of a FSO link with weak turbulence was reported with a packet error rate (PER) of ~10 -2 using coding. Furthermore, an experimental RoF and RoFSO systems using the RF frequency range of 0.4 -4 GHz and a 10 km of SMF were reported in [17].…”