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  • Open Access English
    Country: Luxembourg

    Während sich die Materialitäten und Funktionsweisen von Grenzen in den letzten Jahrzehnten drastisch verändert haben, besteht das ordnende Prinzip der Grenze weiter fort. Dabei zeichnet sich der selektive Charakter von Grenzen in einer in Europa bisher kaum gekannten Deutlichkeit ab. Hier setzen die Beiträ-ge an und diskutieren die Beobachtung, dass Grenzen nicht für alle Menschen in gleicher Weise bedeut-sam sind. Dafür arbeiten die Autor:innen mit dem Begriff der Multivalenz, der unterstellt, dass Grenzen soziale Wertigkeiten oder Relevanzen besitzen, die sich mit Blick auf bestimmte Personengruppen un-terscheiden. Das Themenheft mit Analysebeispielen von Governance, Flucht, Berichterstattung, Film und Literatur zeigt multiple Valenzen von Grenzen auf, die für Ungleichheiten stehen und auf wirkmächtige kulturelle Ordnungen verweisen. Alors que la matérialité et le fonctionnement des frontières ont considérablement changé au cours des dernières décennies, le principe ordonnateur de la frontière persiste. Le caractère sélectif des frontières se dessine avec une netteté jusqu'ici inconnue en Europe. C'est à partir de là que les textes du cahier discutent de l'observation selon laquelle les frontières n'ont pas la même signification pour tous les êtres humains. Pour ce faire, les auteurs utilisent le concept de multivalence, qui suppose que les fron-tières possèdent des valeurs sociales ou des pertinences qui se distinguent en fonction de certains groupes de personnes. Ce cahier thématique, qui présente des études de cas de la gouvernance, de la fuite, du reportage, du cinéma et de la littérature, montre les multiples valences des frontières, qui sont synonymes d'inégalités et renvoient à des ordres culturels puissants. While the materialities and functionalities of borders have changed drastically in recent decades, the ordering principle of the border persists. At the same time, the selective character of borders is emerg-ing with a clarity that has hardly been seen in Europe before. This is the point of departure for the issue papers, which discuss the observation that borders do not have the same significance for all people. For this purpose, the authors work with the concept of multivalence, which assumes that borders have social values or relevances that differ regarding certain groups of people. The thematic issue with case studies of governance, flight, reporting, film, and literature shows multiple valences of borders, which stand for inequalities and refer to powerful cultural orders.

  • Other research product . Other ORP type . 2023
    Open Access English
    Authors: 
    Perissinotto, Flavio; Perucca, Antonella;
    Country: Luxembourg

    Let T be a finite product of one-dimensional tori defined over a number field K. We consider the torsion-Kummer extension K(T[nt], (1/n)G), where n,t are positive integers and G is a finitely generated group of K-points on T. We show how to compute the degree of K(T[nt], (1/n)G) over K and how to determine whether T is split over such an extension. If K=Q, then we may compute at once the degree of the above extensions for all n and t.

  • Open Access English
    Authors: 
    Armaselu, Florentina;
    Country: Luxembourg

    Natural language processing (NLP) for detecting lexical semantic change and linguistic linked open data (LLOD) are two areas of research that have shown promising results in the latest years. However, their potential of being considered together for analysing and representing semantic change from a humanistic perspective needs further study and development. The talk will present an overview of theoretical aspects, NLP techniques and LLOD formalisms intended to this purpose, and will focus on a project developed as a humanities use case within the COST Action “Nexus Linguarum - European network for Web-centred linguistic data science.” The discussion will include preliminary thoughts on the conception of a system that combines dictionary information with corpus evidence, and provides multilingual diachronic ontologies for humanities research.

  • Open Access English
    Authors: 
    Nguyen, Nhan T.; Nguyen, V.-Dinh; Wu, Qingqing; Tölli, Antti; Chatzinotas, Symeon; Juntti, Markku;
    Country: Luxembourg

    We consider a novel hybrid active-passive reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicle (UAV) air-ground communications system. Unlike the conventional passive RIS, the hybrid RIS is equipped with a few active elements to not only reflect but also amplify the incident signals for significant performance improvement. Towards a fairness design, our goal is to maximize the minimum rate among users through jointly optimizing the location and power allocation of the UAV and the RIS reflecting/amplifying coefficients. The formulated optimization problem is nonconvex and challenging, which is efficiently solved via block coordinate descend and successive convex approximation. Our numerical results show that a hybrid RIS requires only 4 active elements and a power budget of 0 dBm to achieve an improvement of 52.08% in the minimum rate, while that achieved by a conventional passive RIS with the same total number of elements is only 18.06%.

  • Open Access German
    Authors: 
    Sagrillo, Damien François;
    Country: Luxembourg
  • Open Access English
    Authors: 
    Krämer, Charlotte; Rathmacher, Yannick; Ottenbacher, Martha; Tremmel, Katharina Antonia Michiko;
    Country: Luxembourg

    Previous surveys on the reading habits of Luxembourgish secondary school students (conducted within the framework of the national school monitoring programme Épreuves Standardisées (ÉpStan) in 2016 and 2019) revealed better reading comprehension results in French and German for those students who frequently read printed narrative texts in their leisure time. However, these studies only focused on different reading modes and text types. They did not investigate which digital and/or printed books students actually read for pleasure, nor which text features determine the positive impact narrative texts have on their reading performances: Is it, for example, the language quality, the richness and complexity of content, or simply the amount of written language they need to process? Therefore, we conducted an explorative follow-up survey within the framework of ÉpStan 2020 and asked secondary school students (Grade 7: n=3055; Grade 9: n=5781) to indicate up to three book titles – printed and e-books respectively – they had read in their leisure time. Despite the omnipresence of digital media, preliminary findings show that both age groups prefer paper-based reading activities when reading longer texts (or books) for pleasure. Nevertheless, the most popular text types and book titles are the same for printed books and e-books: Among them, we find the novel series “Harry Potter”, the rather comic-like book series “Gregs Tagebuch”, and the mangas from the “Naruto”/“Boruto” series. The linkage between students’ leisure time reading activities and their ÉpStan reading performances will be drawn, and some first linguistic text analyses of extracts from the most popular book titles will be conducted in order to reveal some of the text features that foster reading comprehension skills.

  • Open Access English
    Authors: 
    Emslander, Valentin; Levy, Jessica; Fischbach, Antoine;
    Country: Luxembourg

    In such a diverse context as Luxembourg, educational inequalities can arise from diverse languages spoken at home, a migration background, or a family’s socioeconomic status. This diversity leads to different preconditions for learning math and languages (e.g. the language of instruction) and thus shapes the school careers of students (Hadjar & Backes, 2021). The aim of the project Systematic Identification of High Value-Added in Educational Contexts (SIVA) was to answer the questions (1) what highly effective schools are doing “right” or differently and (2) what other schools can learn from them in alleviating inequalities. In collaboration with the Observatoire National de la Qualité Scolaire, we investigated the differences of schools with stable high value-added (VA) scores to those with stable medium or low VA scores from multiple perspectives. VA is a statistical regression method usually used to fairly estimate schools’ effectiveness considering diverse student backgrounds. First, we identified 16 schools which had a stable high, medium, or low VA scores over two years. Second, we collected data on their pedagogical strategies, student background, and school climate through questionnaires and classroom observations. Third, we matched our data to results from the Luxembourg School Monitoring Programme ÉpStan (LUCET, 2021). We selected the variables based on learning models focusing on aspects such as school organization or classroom management (e.g., Hattie, 2008; Helmke et al., 2008; Klieme et al., 2001). We further investigated specificities about the Luxembourgish school system, which are not represented in international school learning models (such as the division into two-year learning cycles, the multilingual school setting, or the diverse student population). We will discuss the SIVA-project, its goals, and its data collection leading to data from observations in 49 classroom and questionnaires with over 500 second graders, their parents, their teachers, as well as school presidents and regional directors. Literature Hadjar, A., & Backes, S. (2021). Bildungsungleichheiten am Übergang in die Sekundarschule in Luxemburg. https://doi.org/10.48746/BB2021LU-DE-21A Hattie, J. (2008). Visible Learning: A synthesis of over 800 meta-analyses relating to achievement (0 ed.). Routledge. https://doi.org/10.4324/9780203887332 Helmke, A., Rindermann, H., & Schrader, F.-W. (2008). Wirkfaktoren akademischer Leistungen in Schule und Hochschule [Determinants of academic achievement in school and university]. In M. Schneider & M. Hasselhorn (Eds.), Handbuch der pädagogischen Psychologie (Vol. 10, pp. 145–155). Hogrefe. Klieme, E., Schümer, G., & Knoll, S. (2001). Mathematikunterricht in der Sekundarstufe I: “Aufgabenkultur” und Unterrichtsgestaltung. TIMSS - Impulse für Schule und Unterricht, 43–57. LUCET. (2021). Épreuves Standardisées (ÉpStan). https://epstan.lu

  • Open Access English
    Authors: 
    Kerger, Sylvie; Pianaro, Enrica; Schadeck, Claire;
    Country: Luxembourg

    Teaching materials, and particularly textbooks, play an essential role in the socialisation of children through the communication of values. As „textbooks are not a reflection of reality, but an arrangement of the representation of a society that they legitimise” (Brugeilles & Cromer, 2008, p.42), we argue that they contribute to challenging, perpetuating, or increasing gender inequalities. The results of our first study on Luxemburgish primary school textbooks, already published, indicate an androcentric view (Kerger & Brasseur, 2021). In every textbook, we counted more male than female characters in the texts and the illustrations. Men are more often represented in professional activities, while women are more likely to perform domestic activities. The celebrities represented are more often men than women. This poster presents the results of history textbooks in secondary school. It shows an ethnocentric perspective on the representation of non-white characters and those with disabilities. People with disabilities are almost exclusively portrayed when disability as a subject is being discussed. Use of racist language. These representations do not transmit the realities of societal complexities and they contribute to the marginalization and discrimination of non-white people and people with disabilities.

  • Open Access English
    Authors: 
    Kaufmann, Lena Maria; Fischbach, Antoine; Ottenbacher, Martha; Hornung, Caroline;
    Country: Luxembourg

    For decades, researchers have been raising awareness of the issue of educational inequalities in the multilingual Luxemburgish school system. Especially children from families with a migration background or a lower socio-economic status show large deficits in their language and mathematics competences in comparison to their peers. The same applies to children who do not speak Luxemburgish or German as their first language (Hornung et al., 2021; Sonnleitner et al., 2021). One way to reduce such educational inequalities might be an early and extensive participation in early childhood education and care (ECEC). Indeed, participation in ECEC was found to be positively connected to language and cognitive development in other countries, especially for children from disadvantaged families (Bennett, 2012). However, these children attend ECEC less often (Vandenbroeck & Lazzari, 2014). There are indications that lower parental costs might go hand in hand with a greater attendance of ECEC in general (for a Luxembourgish study, see Bousselin, 2019) and in particular by disadvantaged families (Busse & Gathmann, 2020). The aim of this study is to spotlight the attendance of ECEC in Luxembourg during the implementation of the ECEC reform after 2017 which increased free ECEC hours for all families from 3 to 20 hours a week. We draw on a large dataset of about 35.000 children from the Épreuves Standardisées (ÉpStan, the Luxemburg school monitoring programme) from 2015 to 2021 and investigate which children attend any kind of regulated ECEC service (public, private or family daycare) in which intensity, taking socio-economic and cultural family factors into account. The findings might help to understand in which contexts ECEC attendance should be further encouraged. Implications for future policy decisions are discussed with the goal of further promoting equal educational opportunities for all children.

  • Open Access English
    Authors: 
    Khan, Wali Ullah; Lagunas, Eva; Mahmood, Asad; Ali, Zain; Chatzinotas, Symeon; Ottersten, Björn;
    Country: Luxembourg

    Future wireless networks are expected to connect large-scale low-powered communication devices using the available spectrum resources. Backscatter communications (BC) is an emerging technology towards battery-free transmission in future wireless networks by leveraging ambient radio frequency (RF) waves that enable communications among wireless devices. Non-orthogonal multiple access (NOMA) has recently drawn significant attention due to its high spectral efficiency. The combination of these two technologies can play an important role in the development of future networks. This paper proposes a new optimization approach to enhance the spectral efficiency of nonorthogonal multiple access (NOMA)-BC network. Our framework simultaneously optimizes the power allocation of base station and reflection coefficient (RC) of the backscatter device in each cell under the assumption of imperfect signal decoding. The problem of spectral efficiency maximization is coupled on power and RC which is challenging to solve. To make this problem tractable, we first decouple it into two subproblems and then apply the decomposition method and Karush-Kuhn-Tucker conditions to obtain the efficient solution. Numerical results show the performance of the proposed NOMA-BC network over the pure NOMA network without BC.

Advanced search in
Research products
arrow_drop_down
Searching FieldsTerms
Any field
arrow_drop_down
includes
arrow_drop_down
Include:
858 Research products, page 1 of 86
  • Open Access English
    Country: Luxembourg

    Während sich die Materialitäten und Funktionsweisen von Grenzen in den letzten Jahrzehnten drastisch verändert haben, besteht das ordnende Prinzip der Grenze weiter fort. Dabei zeichnet sich der selektive Charakter von Grenzen in einer in Europa bisher kaum gekannten Deutlichkeit ab. Hier setzen die Beiträ-ge an und diskutieren die Beobachtung, dass Grenzen nicht für alle Menschen in gleicher Weise bedeut-sam sind. Dafür arbeiten die Autor:innen mit dem Begriff der Multivalenz, der unterstellt, dass Grenzen soziale Wertigkeiten oder Relevanzen besitzen, die sich mit Blick auf bestimmte Personengruppen un-terscheiden. Das Themenheft mit Analysebeispielen von Governance, Flucht, Berichterstattung, Film und Literatur zeigt multiple Valenzen von Grenzen auf, die für Ungleichheiten stehen und auf wirkmächtige kulturelle Ordnungen verweisen. Alors que la matérialité et le fonctionnement des frontières ont considérablement changé au cours des dernières décennies, le principe ordonnateur de la frontière persiste. Le caractère sélectif des frontières se dessine avec une netteté jusqu'ici inconnue en Europe. C'est à partir de là que les textes du cahier discutent de l'observation selon laquelle les frontières n'ont pas la même signification pour tous les êtres humains. Pour ce faire, les auteurs utilisent le concept de multivalence, qui suppose que les fron-tières possèdent des valeurs sociales ou des pertinences qui se distinguent en fonction de certains groupes de personnes. Ce cahier thématique, qui présente des études de cas de la gouvernance, de la fuite, du reportage, du cinéma et de la littérature, montre les multiples valences des frontières, qui sont synonymes d'inégalités et renvoient à des ordres culturels puissants. While the materialities and functionalities of borders have changed drastically in recent decades, the ordering principle of the border persists. At the same time, the selective character of borders is emerg-ing with a clarity that has hardly been seen in Europe before. This is the point of departure for the issue papers, which discuss the observation that borders do not have the same significance for all people. For this purpose, the authors work with the concept of multivalence, which assumes that borders have social values or relevances that differ regarding certain groups of people. The thematic issue with case studies of governance, flight, reporting, film, and literature shows multiple valences of borders, which stand for inequalities and refer to powerful cultural orders.

  • Other research product . Other ORP type . 2023
    Open Access English
    Authors: 
    Perissinotto, Flavio; Perucca, Antonella;
    Country: Luxembourg

    Let T be a finite product of one-dimensional tori defined over a number field K. We consider the torsion-Kummer extension K(T[nt], (1/n)G), where n,t are positive integers and G is a finitely generated group of K-points on T. We show how to compute the degree of K(T[nt], (1/n)G) over K and how to determine whether T is split over such an extension. If K=Q, then we may compute at once the degree of the above extensions for all n and t.

  • Open Access English
    Authors: 
    Armaselu, Florentina;
    Country: Luxembourg

    Natural language processing (NLP) for detecting lexical semantic change and linguistic linked open data (LLOD) are two areas of research that have shown promising results in the latest years. However, their potential of being considered together for analysing and representing semantic change from a humanistic perspective needs further study and development. The talk will present an overview of theoretical aspects, NLP techniques and LLOD formalisms intended to this purpose, and will focus on a project developed as a humanities use case within the COST Action “Nexus Linguarum - European network for Web-centred linguistic data science.” The discussion will include preliminary thoughts on the conception of a system that combines dictionary information with corpus evidence, and provides multilingual diachronic ontologies for humanities research.

  • Open Access English
    Authors: 
    Nguyen, Nhan T.; Nguyen, V.-Dinh; Wu, Qingqing; Tölli, Antti; Chatzinotas, Symeon; Juntti, Markku;
    Country: Luxembourg

    We consider a novel hybrid active-passive reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicle (UAV) air-ground communications system. Unlike the conventional passive RIS, the hybrid RIS is equipped with a few active elements to not only reflect but also amplify the incident signals for significant performance improvement. Towards a fairness design, our goal is to maximize the minimum rate among users through jointly optimizing the location and power allocation of the UAV and the RIS reflecting/amplifying coefficients. The formulated optimization problem is nonconvex and challenging, which is efficiently solved via block coordinate descend and successive convex approximation. Our numerical results show that a hybrid RIS requires only 4 active elements and a power budget of 0 dBm to achieve an improvement of 52.08% in the minimum rate, while that achieved by a conventional passive RIS with the same total number of elements is only 18.06%.

  • Open Access German
    Authors: 
    Sagrillo, Damien François;
    Country: Luxembourg
  • Open Access English
    Authors: 
    Krämer, Charlotte; Rathmacher, Yannick; Ottenbacher, Martha; Tremmel, Katharina Antonia Michiko;
    Country: Luxembourg

    Previous surveys on the reading habits of Luxembourgish secondary school students (conducted within the framework of the national school monitoring programme Épreuves Standardisées (ÉpStan) in 2016 and 2019) revealed better reading comprehension results in French and German for those students who frequently read printed narrative texts in their leisure time. However, these studies only focused on different reading modes and text types. They did not investigate which digital and/or printed books students actually read for pleasure, nor which text features determine the positive impact narrative texts have on their reading performances: Is it, for example, the language quality, the richness and complexity of content, or simply the amount of written language they need to process? Therefore, we conducted an explorative follow-up survey within the framework of ÉpStan 2020 and asked secondary school students (Grade 7: n=3055; Grade 9: n=5781) to indicate up to three book titles – printed and e-books respectively – they had read in their leisure time. Despite the omnipresence of digital media, preliminary findings show that both age groups prefer paper-based reading activities when reading longer texts (or books) for pleasure. Nevertheless, the most popular text types and book titles are the same for printed books and e-books: Among them, we find the novel series “Harry Potter”, the rather comic-like book series “Gregs Tagebuch”, and the mangas from the “Naruto”/“Boruto” series. The linkage between students’ leisure time reading activities and their ÉpStan reading performances will be drawn, and some first linguistic text analyses of extracts from the most popular book titles will be conducted in order to reveal some of the text features that foster reading comprehension skills.

  • Open Access English
    Authors: 
    Emslander, Valentin; Levy, Jessica; Fischbach, Antoine;
    Country: Luxembourg

    In such a diverse context as Luxembourg, educational inequalities can arise from diverse languages spoken at home, a migration background, or a family’s socioeconomic status. This diversity leads to different preconditions for learning math and languages (e.g. the language of instruction) and thus shapes the school careers of students (Hadjar & Backes, 2021). The aim of the project Systematic Identification of High Value-Added in Educational Contexts (SIVA) was to answer the questions (1) what highly effective schools are doing “right” or differently and (2) what other schools can learn from them in alleviating inequalities. In collaboration with the Observatoire National de la Qualité Scolaire, we investigated the differences of schools with stable high value-added (VA) scores to those with stable medium or low VA scores from multiple perspectives. VA is a statistical regression method usually used to fairly estimate schools’ effectiveness considering diverse student backgrounds. First, we identified 16 schools which had a stable high, medium, or low VA scores over two years. Second, we collected data on their pedagogical strategies, student background, and school climate through questionnaires and classroom observations. Third, we matched our data to results from the Luxembourg School Monitoring Programme ÉpStan (LUCET, 2021). We selected the variables based on learning models focusing on aspects such as school organization or classroom management (e.g., Hattie, 2008; Helmke et al., 2008; Klieme et al., 2001). We further investigated specificities about the Luxembourgish school system, which are not represented in international school learning models (such as the division into two-year learning cycles, the multilingual school setting, or the diverse student population). We will discuss the SIVA-project, its goals, and its data collection leading to data from observations in 49 classroom and questionnaires with over 500 second graders, their parents, their teachers, as well as school presidents and regional directors. Literature Hadjar, A., & Backes, S. (2021). Bildungsungleichheiten am Übergang in die Sekundarschule in Luxemburg. https://doi.org/10.48746/BB2021LU-DE-21A Hattie, J. (2008). Visible Learning: A synthesis of over 800 meta-analyses relating to achievement (0 ed.). Routledge. https://doi.org/10.4324/9780203887332 Helmke, A., Rindermann, H., & Schrader, F.-W. (2008). Wirkfaktoren akademischer Leistungen in Schule und Hochschule [Determinants of academic achievement in school and university]. In M. Schneider & M. Hasselhorn (Eds.), Handbuch der pädagogischen Psychologie (Vol. 10, pp. 145–155). Hogrefe. Klieme, E., Schümer, G., & Knoll, S. (2001). Mathematikunterricht in der Sekundarstufe I: “Aufgabenkultur” und Unterrichtsgestaltung. TIMSS - Impulse für Schule und Unterricht, 43–57. LUCET. (2021). Épreuves Standardisées (ÉpStan). https://epstan.lu

  • Open Access English
    Authors: 
    Kerger, Sylvie; Pianaro, Enrica; Schadeck, Claire;
    Country: Luxembourg

    Teaching materials, and particularly textbooks, play an essential role in the socialisation of children through the communication of values. As „textbooks are not a reflection of reality, but an arrangement of the representation of a society that they legitimise” (Brugeilles & Cromer, 2008, p.42), we argue that they contribute to challenging, perpetuating, or increasing gender inequalities. The results of our first study on Luxemburgish primary school textbooks, already published, indicate an androcentric view (Kerger & Brasseur, 2021). In every textbook, we counted more male than female characters in the texts and the illustrations. Men are more often represented in professional activities, while women are more likely to perform domestic activities. The celebrities represented are more often men than women. This poster presents the results of history textbooks in secondary school. It shows an ethnocentric perspective on the representation of non-white characters and those with disabilities. People with disabilities are almost exclusively portrayed when disability as a subject is being discussed. Use of racist language. These representations do not transmit the realities of societal complexities and they contribute to the marginalization and discrimination of non-white people and people with disabilities.

  • Open Access English
    Authors: 
    Kaufmann, Lena Maria; Fischbach, Antoine; Ottenbacher, Martha; Hornung, Caroline;
    Country: Luxembourg

    For decades, researchers have been raising awareness of the issue of educational inequalities in the multilingual Luxemburgish school system. Especially children from families with a migration background or a lower socio-economic status show large deficits in their language and mathematics competences in comparison to their peers. The same applies to children who do not speak Luxemburgish or German as their first language (Hornung et al., 2021; Sonnleitner et al., 2021). One way to reduce such educational inequalities might be an early and extensive participation in early childhood education and care (ECEC). Indeed, participation in ECEC was found to be positively connected to language and cognitive development in other countries, especially for children from disadvantaged families (Bennett, 2012). However, these children attend ECEC less often (Vandenbroeck & Lazzari, 2014). There are indications that lower parental costs might go hand in hand with a greater attendance of ECEC in general (for a Luxembourgish study, see Bousselin, 2019) and in particular by disadvantaged families (Busse & Gathmann, 2020). The aim of this study is to spotlight the attendance of ECEC in Luxembourg during the implementation of the ECEC reform after 2017 which increased free ECEC hours for all families from 3 to 20 hours a week. We draw on a large dataset of about 35.000 children from the Épreuves Standardisées (ÉpStan, the Luxemburg school monitoring programme) from 2015 to 2021 and investigate which children attend any kind of regulated ECEC service (public, private or family daycare) in which intensity, taking socio-economic and cultural family factors into account. The findings might help to understand in which contexts ECEC attendance should be further encouraged. Implications for future policy decisions are discussed with the goal of further promoting equal educational opportunities for all children.

  • Open Access English
    Authors: 
    Khan, Wali Ullah; Lagunas, Eva; Mahmood, Asad; Ali, Zain; Chatzinotas, Symeon; Ottersten, Björn;
    Country: Luxembourg

    Future wireless networks are expected to connect large-scale low-powered communication devices using the available spectrum resources. Backscatter communications (BC) is an emerging technology towards battery-free transmission in future wireless networks by leveraging ambient radio frequency (RF) waves that enable communications among wireless devices. Non-orthogonal multiple access (NOMA) has recently drawn significant attention due to its high spectral efficiency. The combination of these two technologies can play an important role in the development of future networks. This paper proposes a new optimization approach to enhance the spectral efficiency of nonorthogonal multiple access (NOMA)-BC network. Our framework simultaneously optimizes the power allocation of base station and reflection coefficient (RC) of the backscatter device in each cell under the assumption of imperfect signal decoding. The problem of spectral efficiency maximization is coupled on power and RC which is challenging to solve. To make this problem tractable, we first decouple it into two subproblems and then apply the decomposition method and Karush-Kuhn-Tucker conditions to obtain the efficient solution. Numerical results show the performance of the proposed NOMA-BC network over the pure NOMA network without BC.

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