Federica Aveta

Multi-user free-space optical communication (FSOC) is beginning to draw a significant attention for its ability to support increased system network capacity while using single receiving photodiode and satisfying size, weight, and power (SWaP) constraints imposed by space- and aerial-based mobile communication. Despite these advantages, support of multi-user capabilities cause increased system complexity due to accommodating heterogenous users communications with varying transmission and data… Show more

Multi-user free-space optical communication (FSOC) is beginning to draw a significant attention for its ability to support increased system network capacity while using single receiving photodiode and satisfying size, weight, and power (SWaP) constraints imposed by space- and aerial-based mobile communication. Despite these advantages, support of multi-user capabilities cause increased system complexity due to accommodating heterogenous users communications with varying transmission and data rate requirements. Machine learning (ML) has recently been considered as a promising approach for introducing cognition into the network to mitigate some of the complexity. A cognitive method based on unsupervised ML was derived for estimating the number of users communicating and sharing time and bandwidth resources with a single-node receiver. A weighted clustering approach was introduced and experimentally validated when users received with similar amplitude information that results in underestimation. Obtained results confirmed that the proposed methodology was able to accurately differentiate the number of simultaneously transmitting users with accuracy greater than 92%— even in the presence of moderate atmospheric turbulence. An experimental analysis was conducted to determine data size and receiver sampling rate requirements for accurate estimation. Furthermore, an empirical model was derived to evaluate the effect of preamble signal length given a particular sampling rate on the accuracy of the estimation. The model was validated for up-to four users. Show less

A methodology based on convolutional neural network (CNN) is proposed for joint
classification of transmitting user number and modulation format in a multiuser free-space optical
communication (FSOC) link. The proposed methodology relies on amplitude information of
received mixed signal. In-phase and quadrature components of users that are sharing time and
bandwidth resources transmitting into the same optical wireless access point and interfering
within each other are analyzed… Show more

A methodology based on convolutional neural network (CNN) is proposed for joint
classification of transmitting user number and modulation format in a multiuser free-space optical
communication (FSOC) link. The proposed methodology relies on amplitude information of
received mixed signal. In-phase and quadrature components of users that are sharing time and
bandwidth resources transmitting into the same optical wireless access point and interfering
within each other are analyzed. The proposed approach utilizes the constellation diagrams of the
received mixed symbols to generate image data sets that are fed into CNN input. The
designed CNN model with three convolutional layers was tested for: varying image resolutions,
image-data set size, varying number of received symbols, and atmospheric turbulence to
identify optimal parameters and processing time for system design and implementation. The
results indicate that the CNN model can blindly and accurately identify the communicating
device number and their optical modulation format with classification accuracy up to 100% for
various SNRs. Moreover, the CNN demonstrated robustness against atmospheric turbulence and
suggested immunity to additive noise. Therefore, the proposed methodology proved to be a
promising and feasible solution for practical implementation of an intelligent optical wireless
receiver for aerial and terrestrial FSOC links. Show less

Free Space Optical (FSO) multi-user communication provides high aggregate bandwidth and link robustness attributable to spatial diversity. The primary challenge for this technology is interference among multiple users at the receiver. A non-orthogonal multiple access (NOMA) technique multiplexes numerous users in the power domain at the same time and frequency resource. Thus, different users simultaneously transmit their signals with various power levels. The receiver then decodes user data… Show more

Free Space Optical (FSO) multi-user communication provides high aggregate bandwidth and link robustness attributable to spatial diversity. The primary challenge for this technology is interference among multiple users at the receiver. A non-orthogonal multiple access (NOMA) technique multiplexes numerous users in the power domain at the same time and frequency resource. Thus, different users simultaneously transmit their signals with various power levels. The receiver then decodes user data individually from the overlapped signal using successive interference cancellation (SIC). This paper reports the use of NOMA in an FSO link with two users and details an investigation of the effects of power allocation and channel estimation on the user’s signals demodulation accuracy. Analysis of varying data rate and system capacity gain are explored. Experimental results indicate that accurate channel estimation and optimum power allocation ratio can improve the accuracy of signal reconstruction. Difference in data rate tested proved negligible to signal demodulation quality. Show less

Optical wireless communication (OWC) has emerged as an attractive and promising solution for supporting high-capacity and high-density networks required by the fifth-generation (5G) communication standard and the Internet of Thing (IoT) system. As a wireless technology, OWC must ensure that multiple users can communicate through the network. To facilitate this, the ability of diverse optical multiple access control (O-MAC) techniques are analyzed in this paper. Combinations of different O-MAC… Show more

Optical wireless communication (OWC) has emerged as an attractive and promising solution for supporting high-capacity and high-density networks required by the fifth-generation (5G) communication standard and the Internet of Thing (IoT) system. As a wireless technology, OWC must ensure that multiple users can communicate through the network. To facilitate this, the ability of diverse optical multiple access control (O-MAC) techniques are analyzed in this paper. Combinations of different O-MAC methods that were individually tested in previous work are studied and experimentally validated. Results from testing four methods— Independent Component Analysis (ICA) and non-orthogonal multiple access (NOMA); ICA and signal subtraction; NOMA on one received mixed signal; and NOMA on two received mixed signals—proved successful for free space optical communication (FSOC) in a setup comprised of three users and a dual-path fiber bundle receiver. Users with same data rate and with various data rate were tested. Obtained results showed that received signals were demodulated with high accuracy. Show less

Increasing usage and higher demand for wireless traffic are causing a critical need for increased bandwidth and capacity communication networks. Accordingly, multipoint free-space optical communication (FSOC) links are beginning to draw significant attention as a valuable and promising solution for satisfying new network requirements. Extensive interest has focused on investigating and developing hardware design solutions to perform multiuser FSOC. However, to meet the low size, weight, and… Show more

Increasing usage and higher demand for wireless traffic are causing a critical need for increased bandwidth and capacity communication networks. Accordingly, multipoint free-space optical communication (FSOC) links are beginning to draw significant attention as a valuable and promising solution for satisfying new network requirements. Extensive interest has focused on investigating and developing hardware design solutions to perform multiuser FSOC. However, to meet the low size, weight, and power needs of this technology, we propose using a robust and solid signal-processing method, namely independent component analysis (ICA), to implement an optical multiple access technique. A high-speed, multipoint free space optical system composed of two independent users and two receiving sensors is introduced. FastICA and joint approximate diagonalization of eigenmatrices algorithms are exploited for multiuser detection, and extensive analysis of power ratio, data rate difference, computational complexity, achievable system capacity, turbulence generation accuracy, and turbulence severity effects on signal reconstruction is performed. Experimental results demonstrate that ICA provides suitable source separation for all tested configurations. Additionally, transmission parameters that maximize signal reconstruction performances were identified. Show less

Multi-point free-space optical communication (FSOC) has recently received extensive interest as a valuable solution for providing increased capacity in the upcoming communication networks. Diverse optical multiple access control (O-MAC) techniques have proved to successfully support multi-user FSOC. However, to adaptively and automatically select the most fitting O-MAC technique or combination thereof for signal demodulation, the number of transmitting users should be known a priori at the… Show more

Multi-point free-space optical communication (FSOC) has recently received extensive interest as a valuable solution for providing increased capacity in the upcoming communication networks. Diverse optical multiple access control (O-MAC) techniques have proved to successfully support multi-user FSOC. However, to adaptively and automatically select the most fitting O-MAC technique or combination thereof for signal demodulation, the number of transmitting users should be known a priori at the receiver side. In this letter, a technique based on histogram peak detection and unsupervised machine learning (e.g., k-mean, k-medoid, hierarchical, and fuzzy clustering), is proposed and experimentally demonstrated for number of users detection. The proposed methodology relies on amplitude information of received signals. Results show that when multiple users’ signals are received with equal amplitude, under-estimation of user number was observed; hence, a modified approach—a weighted clustering—was employed and experimentally validated. The work reported herein demonstrated the ability of the proposed methodology to simultaneously and accurately detect multiple transmitting users in real time and under severe atmospheric turbulence. Show less

Free Space Optical (FSO) communication is widely recognized for its powerful features, especially when compared to other wireless technologies utilized in point-to-point communication links. Although current literature focuses primarily on point-to-point transmission, multi-user FSO systems are beginning to draw significant attention. The primary objective in a multi-user communication system is to estimate individually transmitted signals from received signals, namely Blind Source Separation… Show more

Free Space Optical (FSO) communication is widely recognized for its powerful features, especially when compared to other wireless technologies utilized in point-to-point communication links. Although current literature focuses primarily on point-to-point transmission, multi-user FSO systems are beginning to draw significant attention. The primary objective in a multi-user communication system is to estimate individually transmitted signals from received signals, namely Blind Source Separation (BSS). A solution to the BSS problem in an FSO multi-user communication link is proposed. A multi-point FSO system composed of two independent transmitters operating at different wavelengths and a dual path fiber bundle receiver was used. The FastICA algorithm was exploited for multi-user detection. Experimental results demonstrate that this method can separate original transmitted signals from their received mixtures. Effects of signal power, data rate, misalignment error, and turbulence severity on signal separation are also explored to define the working range for achieving best performance. Show less

Free Space Optical (FSO) communication technology has a data rate higher than other wireless communication techniques. Although FSO has enjoyed widespread notoriety for its point-to-point communication, the increasing demand of mobile platforms and multi-user communications requires considerable improvement over current FSO systems. Developing multi-point mobile FSO systems is highly desirable. To aid in this effort, the work presented in this paper details a solution for overcoming the Blind… Show more

Free Space Optical (FSO) communication technology has a data rate higher than other wireless communication techniques. Although FSO has enjoyed widespread notoriety for its point-to-point communication, the increasing demand of mobile platforms and multi-user communications requires considerable improvement over current FSO systems. Developing multi-point mobile FSO systems is highly desirable. To aid in this effort, the work presented in this paper details a solution for overcoming the Blind Source Separation (BSS) problem in a multi-user communication link. A multi-user FSO link with various atmospheric conditions that leverages the FastICA algorithm is detailed below. Experimental results have been obtained with a system composed of two transmitters operating at different wavelengths and two receivers. Results demonstrate that using this method, the original optically transmitted signals can be separated from their received mixtures, even during high turbulence conditions. Show less