23 research outputs found

    Systematic Approaches for Telemedicine and Data Coordination for COVID-19 in Baja California, Mexico

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    Conference proceedings info: ICICT 2023: 2023 The 6th International Conference on Information and Computer Technologies Raleigh, HI, United States, March 24-26, 2023 Pages 529-542We provide a model for systematic implementation of telemedicine within a large evaluation center for COVID-19 in the area of Baja California, Mexico. Our model is based on human-centric design factors and cross disciplinary collaborations for scalable data-driven enablement of smartphone, cellular, and video Teleconsul-tation technologies to link hospitals, clinics, and emergency medical services for point-of-care assessments of COVID testing, and for subsequent treatment and quar-antine decisions. A multidisciplinary team was rapidly created, in cooperation with different institutions, including: the Autonomous University of Baja California, the Ministry of Health, the Command, Communication and Computer Control Center of the Ministry of the State of Baja California (C4), Colleges of Medicine, and the College of Psychologists. Our objective is to provide information to the public and to evaluate COVID-19 in real time and to track, regional, municipal, and state-wide data in real time that informs supply chains and resource allocation with the anticipation of a surge in COVID-19 cases. RESUMEN Proporcionamos un modelo para la implementaciรณn sistemรกtica de la telemedicina dentro de un gran centro de evaluaciรณn de COVID-19 en el รกrea de Baja California, Mรฉxico. Nuestro modelo se basa en factores de diseรฑo centrados en el ser humano y colaboraciones interdisciplinarias para la habilitaciรณn escalable basada en datos de tecnologรญas de teleconsulta de telรฉfonos inteligentes, celulares y video para vincular hospitales, clรญnicas y servicios mรฉdicos de emergencia para evaluaciones de COVID en el punto de atenciรณn. pruebas, y para el tratamiento posterior y decisiones de cuarentena. Rรกpidamente se creรณ un equipo multidisciplinario, en cooperaciรณn con diferentes instituciones, entre ellas: la Universidad Autรณnoma de Baja California, la Secretarรญa de Salud, el Centro de Comando, Comunicaciones y Control Informรกtico. de la Secretarรญa del Estado de Baja California (C4), Facultades de Medicina y Colegio de Psicรณlogos. Nuestro objetivo es proporcionar informaciรณn al pรบblico y evaluar COVID-19 en tiempo real y rastrear datos regionales, municipales y estatales en tiempo real que informan las cadenas de suministro y la asignaciรณn de recursos con la anticipaciรณn de un aumento de COVID-19. 19 casos.ICICT 2023: 2023 The 6th International Conference on Information and Computer Technologieshttps://doi.org/10.1007/978-981-99-3236-

    ๋น„๋ฉดํ—ˆ๋Œ€์—ญ ์…€๋ฃฐ๋ผ ํ†ต์‹ ์˜ ์„ฑ๋Šฅ ๋ถ„์„ ๋ฐ ์„ฑ๋Šฅ ํ–ฅ์ƒ ๊ธฐ๋ฒ• ์—ฐ๊ตฌ

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ) -- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ๊ณต๊ณผ๋Œ€ํ•™ ์ „๊ธฐยท์ •๋ณด๊ณตํ•™๋ถ€, 2021. 2. ๋ฐ•์„ธ์›….3GPP๋Š” LAA (licensed-assisted access)๋ผ๊ณ ํ•˜๋Š” 5GHz ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ LTE๋ฅผ ๊ฐœ๋ฐœํ–ˆ์Šต๋‹ˆ๋‹ค. LAA๋Š” ์ถฉ๋Œ ๋ฐฉ์ง€ ๊ธฐ๋Šฅ์„ ์‚ฌ์šฉํ•˜๊ธฐ ์œ„ํ•ด Wi-Fi์˜ CSMA / CA (Carrier Sense Multiple Access with Collision avoidance)์™€ ์œ ์‚ฌํ•œ LBT (Listen Before Talk) ์ž‘์—…์„ ์ฑ„ํƒํ•˜์—ฌ ๊ฐ LAA ๋‹ค์šด ๋งํฌ ๋ฒ„์ŠคํŠธ์˜ ํ”„๋ ˆ์ž„ ๊ตฌ์กฐ ์˜ค๋ฒ„ ํ—ค๋“œ๋Š” ๊ฐ๊ฐ์˜ ์ข…๋ฃŒ ์‹œ๊ฐ„์— ๋”ฐ๋ผ ๋‹ฌ๋ผ์ง‘๋‹ˆ๋‹ค. ์ด์ „ LBT ์ž‘์—…. ์ด ๋…ผ๋ฌธ์—์„œ๋Š” ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ ์…€๋ฃฐ๋Ÿฌ ํ†ต์‹ ์„ ๋ถ„์„ํ•˜๊ธฐ์œ„ํ•œ ์ˆ˜์น˜ ๋ชจ๋ธ์„ ์ œ์•ˆํ•œ๋‹ค. ๋‹ค์Œ์œผ๋กœ, ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ ์…€๋ฃฐ๋Ÿฌ ํ†ต์‹ ์˜ ๋‹ค์Œ ๋‘ ๊ฐ€์ง€ ํ–ฅ์ƒ๋œ ๊ธฐ๋Šฅ์„ ๊ณ ๋ คํ•ฉ๋‹ˆ๋‹ค. ๋Œ€์—ญ ๋…๋ฆฝํ˜• ์…€๋ฃฐ๋Ÿฌ ํ†ต์‹ . ๊ธฐ์กด WiFi ๋ถ„์„ ๋ชจ๋ธ๋กœ๋Š” LAA์˜ ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•  ์ˆ˜ ์—†๋‹ค๋Š” ์ ์„ ๊ฐ์•ˆํ•˜์—ฌ ๋ณธ ์„œ์‹ ์—์„œ๋Š” ์—ฌ๋Ÿฌ ๊ฒฝํ•ฉ ์ง„ํ™” ๋œ NodeB๋กœ ๊ตฌ์„ฑ๋œ LAA ๋„คํŠธ์›Œํฌ์˜ ์„ฑ๋Šฅ์„ ๋ถ„์„ํ•˜๊ธฐ์œ„ํ•œ ์ƒˆ๋กœ์šด Markov ์ฒด์ธ ๊ธฐ๋ฐ˜ ๋ถ„์„ ๋ชจ๋ธ์„ ์ œ์•ˆํ•ฉ๋‹ˆ๋‹ค. LAA ํ”„๋ ˆ์ž„ ๊ตฌ์กฐ ์˜ค๋ฒ„ ํ—ค๋“œ์˜ ๋ณ€ํ˜•. LTE-LAA๋Š” LTE์—์„œ ์ƒ์† ๋œ ์†๋„ ์ ์‘ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์œ„ํ•ด ์ ์‘ ๋ณ€์กฐ ๋ฐ ์ฝ”๋”ฉ (AMC) ์„ ์ฑ„ํƒํ•ฉ๋‹ˆ๋‹ค. AMC๋Š” ์ง„ํ™” ๋œ nodeB (eNB)๊ฐ€ ํ˜„์žฌ ์ „์†ก์˜ ์ฑ„๋„ ํ’ˆ์งˆ ํ‘œ์‹œ๊ธฐ ํ”ผ๋“œ ๋ฐฑ์„ ์‚ฌ์šฉํ•˜์—ฌ ๋‹ค์Œ ์ „์†ก์„์œ„ํ•œ ๋ณ€์กฐ ๋ฐ ์ฝ”๋”ฉ ๋ฐฉ์‹ (MCS)์„ ์„ ํƒํ•˜๋„๋ก ๋•์Šต๋‹ˆ๋‹ค. ๋ผ์ด์„ ์Šค ๋Œ€์—ญ์—์„œ ๋™์ž‘ํ•˜๋Š” ๊ธฐ์กด LTE์˜ ๊ฒฝ์šฐ ๋…ธ๋“œ ๊ฒฝํ•ฉ ๋ฌธ์ œ๊ฐ€ ์—†์œผ๋ฉฐ AMC ์„ฑ๋Šฅ ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ์ž˜ ์ง„ํ–‰๋˜๊ณ  ์žˆ์Šต๋‹ˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ์—์„œ ๋™์ž‘ํ•˜๋Š” LTE-LAA ์˜ ๊ฒฝ์šฐ ์ถฉ๋Œ ๋ฌธ์ œ๋กœ ์ธํ•ด AMC ์„ฑ๋Šฅ์ด ์ œ๋Œ€๋กœ ์ฒ˜๋ฆฌ๋˜์ง€ ์•Š์•˜์Šต๋‹ˆ๋‹ค. ์ด ํŽธ์ง€์—์„œ๋Š” AMC ์šด์˜์„ ๊ณ ๋ คํ•œ ํ˜„์‹ค์ ์ธ ์ฑ„๋„ ๋ชจ๋ธ์—์„œ LTELAA ์„ฑ๋Šฅ์„ ๋ถ„์„ํ•˜๊ธฐ์œ„ํ•œ ์ƒˆ๋กœ ์šด Markov ์ฒด์ธ ๊ธฐ๋ฐ˜ ๋ถ„์„ ๋ชจ๋ธ์„ ์ œ์•ˆํ•ฉ๋‹ˆ๋‹ค. ๋ฌด์„  ๋„คํŠธ์›Œํฌ ๋ถ„์„์— ๋„๋ฆฌ ์‚ฌ์šฉ๋˜๋Š” Rayleigh ํŽ˜์ด๋”ฉ ์ฑ„๋„ ๋ชจ๋ธ์„ ์ฑ„ํƒํ•˜๊ณ  ๋ถ„์„ ๊ฒฐ๊ณผ๋ฅผ ns-3 ์‹œ๋ฎฌ๋ ˆ์ดํ„ฐ์—์„œ ์–ป์€ ๊ฒฐ๊ณผ ์™€ ๋น„๊ตํ•ฉ๋‹ˆ๋‹ค. ๋น„๊ต ๊ฒฐ๊ณผ๋Š” ํ‰๊ท  ์ •ํ™•๋„๊ฐ€ 99.5%๋กœ ๋ถ„์„ ๋ชจ๋ธ์˜ ์ •ํ™•๋„๋ฅผ ๋ณด์—ฌ์ค๋‹ˆ๋‹ค. ๋†’์€ ๋ฐ์ดํ„ฐ ์†๋„์— ๋Œ€ํ•œ ์š”๊ตฌ ์‚ฌํ•ญ์œผ๋กœ ์ธํ•ด 3GPP๋Š” LTE-LAA๋ฅผ์œ„ํ•œ ๋‹ค์ค‘ ๋ฐ˜์†กํŒŒ ์šด์˜์„ ์ œ๊ณตํ–ˆ์Šต๋‹ˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๋‹ค์ค‘ ๋ฐ˜์†กํŒŒ ๋™์ž‘์€ OOBE์— ์ทจ์•ฝํ•˜๊ณ  ์ œํ•œ๋œ ์ „์†ก ์ „๋ ฅ์„ ์‚ฌ์šฉํ•˜์—ฌ ๋น„ํšจ์œจ์  ์ธ ์ฑ„๋„ ์‚ฌ์šฉ์„ ์ดˆ๋ž˜ํ•ฉ๋‹ˆ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์€ ์ฑ„๋„ ํšจ์œจ์„ ๋†’์ด๊ธฐ์œ„ํ•œ ์ƒˆ๋กœ์šด ๋‹ค์ค‘ ๋ฐ˜์†กํŒŒ ์ ‘๊ทผ ๋ฐฉ์‹์„ ์ œ์•ˆํ•œ๋‹ค. ์šฐ๋ฆฌ๊ฐ€ ์ œ์•ˆํ•œ ๋ฐฉ์‹์€ ์ „์†ก ๋ฒ„์ŠคํŠธ๋ฅผ ์—ฌ๋Ÿฌ ๊ฐœ๋กœ ๋ถ„ํ• ํ•˜๊ณ  ์ „์†ก ์ „๋ ฅ ์ œํ•œ์„ ์ถฉ์กฑํ•˜๋ฉด์„œ ์งง์€ ์„œ๋ธŒ ํ”„๋ ˆ์ž„ ์ „์†ก ์„ ์‚ฌ์šฉํ•ฉ๋‹ˆ๋‹ค. ๋˜ํ•œ ์ฑ„๋„ ์ƒํƒœ๋ฅผ ์ •ํ™•ํ•˜๊ฒŒ ํŒ๋‹จํ•˜์—ฌ OOBE ๋ฌธ์ œ๋ฅผ ๊ทน๋ณต ํ•  ์ˆ˜์žˆ๋Š” ์—๋„ˆ์ง€ ๊ฐ์ง€ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ œ์•ˆํ•ฉ๋‹ˆ๋‹ค. ์†Œํ”„ํŠธ์›จ์–ด ์ •์˜ ๋ผ๋””์˜ค๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ํ”„๋กœํ†  ํƒ€์ž…์€ 99% ์ด์ƒ์˜ ์ •ํ™•๋„๋กœ ์ฑ„๋„ ์ƒํƒœ๋ฅผ ๊ฒฐ์ •ํ•˜๋Š” ์—๋„ˆ์ง€ ๊ฐ์ง€ ์•Œ๊ณ ๋ฆฌ์ฆ˜์˜ ์‹คํ–‰ ๊ฐ€๋Šฅ์„ฑ๊ณผ ์„ฑ๋Šฅ์„ ๋ณด์—ฌ์ค๋‹ˆ๋‹ค. ns-3 ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•ด ์ œ์•ˆ ๋œ ๋‹ค์ค‘ ๋ฐ˜์†กํŒŒ ์•ก์„ธ์Šค ๋ฐฉ์‹์ด ๊ธฐ์กด LBT ์œ ํ˜• A ๋ฐ ์œ ํ˜• B์— ๋น„ํ•ด ์‚ฌ์šฉ์ž์ธ์ง€ ์ฒ˜๋ฆฌ๋Ÿ‰์—์„œ ๊ฐ๊ฐ ์ตœ๋Œ€ 59% ๋ฐ 21.5%์˜ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ๋‹ฌ์„ฑ ํ•จ์„ ํ™•์ธํ–ˆ์Šต๋‹ˆ๋‹ค. ๋ ˆ๊ฑฐ์‹œ LAA์—๋Š” ๋ฐฐํฌ ๋ฌธ์ œ๊ฐ€ ์žˆ๊ธฐ ๋•Œ๋ฌธ์— 3GPP์™€ MulteFire ์–ผ๋ผ์ด์–ธ์Šค๋Š” ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ ๋…๋ฆฝํ˜• ์…€๋ฃฐ๋Ÿฌ ํ†ต์‹  ์‹œ์Šค ํ…œ์„ ์ œ์•ˆํ–ˆ์Šต๋‹ˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ์ข…๋ž˜์˜ ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ ๋…๋ฆฝํ˜• ์…€๋ฃฐ๋Ÿฌ ํ†ต์‹  ์‹œ์Šคํ…œ์€ ์ƒํ–ฅ ๋งํฌ ์ œ์–ด ๋ฉ”์‹œ์ง€์˜ ์ „์†ก ํ™•๋ฅ ์ด ๋‚ฎ๋‹ค. ์ด ๋…ผ๋ฌธ์€ Wi-Fi ๋ธ”๋ก ACK ํ”„๋ ˆ์ž„์— ์—… ๋งํฌ ์ œ์–ด ๋ฉ”์‹œ์ง€๋ฅผ ๋„ฃ๋Š” W ARQ : Wi-Fi ์ง€์› HARQ๋ฅผ ์ œ์•ˆํ•ฉ๋‹ˆ๋‹ค. ๋˜ํ•œ W-ARQ์˜ ์ฒ˜ ๋ฆฌ ์„ฑ๋Šฅ์„ ํ–ฅ์ƒ์‹œํ‚ค๊ธฐ ์œ„ํ•ด ๋ณ‘๋ ฌ HARQ ๋ฐ ํด๋Ÿฌ์Šคํ„ฐ๋ง ๋œ Minstrel์„ ์ œ์•ˆํ•ฉ๋‹ˆ๋‹ค. ์šฐ๋ฆฌ๊ฐ€ ์ œ์•ˆํ•œ ์•Œ๊ณ ๋ฆฌ์ฆ˜์€ ๊ธฐ์กด MulteFire๊ฐ€ ๊ฑฐ์˜ ์ œ๋กœ ์ฒ˜๋ฆฌ๋Ÿ‰ ์„ฑ๋Šฅ์„ ๋ณด์ด๋Š” ๊ฒฝ์šฐ ๋†’์€ ์ฒ˜๋ฆฌ๋Ÿ‰ ์„ฑ๋Šฅ์„ ๋ณด์—ฌ์ค๋‹ˆ๋‹ค. ์š”์•ฝํ•˜๋ฉด ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ ์…€๋ฃฐ๋Ÿฌ ํ†ต์‹ ์˜ ์„ฑ๋Šฅ์„ ๋ถ„์„ ํ•ฉ๋‹ˆ๋‹ค. ์ œ์•ˆ ๋œ ๋ชจ๋ธ์„ ์‚ฌ์šฉํ•จ์œผ๋กœ์จ ์šฐ๋ฆฌ๋Š” ๋ ˆ๊ฑฐ์‹œ ๋‹ค์ค‘ ๋ฐ˜์†กํŒŒ ๋™์ž‘์„ ์ฃผ์žฅํ•˜๋ฉฐ ๋น„๋ฉดํ—ˆ ์…€๋ฃฐ๋Ÿฌ ํ†ต์‹ ์˜ HARQ๋Š” ํšจ์œจ์ ์ด์ง€ ์•Š๋‹ค. ์ด๋Ÿฌํ•œ ์ด์œ ๋กœ, ์šฐ๋ฆฌ๋Š” ์ตœ์ฒจ๋‹จ ๊ธฐ ์ˆ ์— ๋น„ํ•ด UPT ๋ฐ ์ฒ˜๋ฆฌ๋Ÿ‰๊ณผ ๊ฐ™์€ ๋„คํŠธ์›Œํฌ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ๋‹ฌ์„ฑํ•˜๋Š” OOBE ์ธ์‹ ์ถ”๊ฐ€ ์•ก์„ธ์Šค ๋ฐ W-ARQ๋ฅผ ์ œ์•ˆํ•ฉ๋‹ˆ๋‹ค.3GPP has developed 5 GHz unlicensed band LTE, referred to as licensed-assisted access (LAA). LAA adopts listen before talk (LBT) operation, resembling Wi-Fis carrier sense multiple access with collision avoidance (CSMA/CA), to enable collision avoidance capability, while the frame structure overhead of each LAA downlink burst varies with the ending time of each preceding LBT operation. In this dissertation, we propose numerical model to analyze unlicensed band cellular communication. Next, we consider the following two enhancements of unlicensed band cellular communication: (i) out-of-band emission (OOBE) aware additional carrier access, and (ii) Wi-Fi assisted hybrid automatic repeat request (H-ARQ) for unlicensed-band stand-alone cellular communication. Given that, existing analytic models of Wi-Fi cannot be used to evaluate the performance of LAA, in this letter, we propose a novel Markov chain-based analytic model to analyze the performance of LAA network composed of multiple contending evolved NodeBs by considering the variation of the LAA frame structure overhead. LTE-LAA adopts adaptive modulation and coding (AMC) for the rate adaptation algorithm inherited from LTE. AMC helps the evolved nodeB (eNB) to select a modulation and coding scheme (MCS) for the next transmission using the channel quality indicator feedback of the current transmission. For the conventional LTE operating in the licensed band, there is no node contention problem and AMC performance has been well studied. However, in the case of LTE-LAA operating in the unlicensed band, AMC performance has not been properly addressed due to the collision problem. In this letter, we propose a novel Markov chain-based analysis model for analyzing LTELAA performance under a realistic channel model considering AMC operation. We adopt Rayleigh fading channel model widely used in wireless network analysis, and compare our analysis results with the results obtained from ns-3 simulator. Comparison results show an average accuracy of 99.5%, which demonstrates the accuracy of our analysis model. Due to the requirement for a high data rate, the 3GPP has provided multi-carrier operation for LTE-LAA. However, multi-carrier operation is susceptible to OOBE and uses limited transmission power, resulting in inefficient channel usage. This paper proposes a novel multi-carrier access scheme to enhance channel efficiency. Our proposed scheme divides a transmission burst into multiple ones and uses short subframe transmission while meeting the transmission power limitation. In addition, we propose an energy detection algorithm to overcome the OOBE problem by deciding the channel status accurately. Our prototype using software-defined radio shows the feasibility and performance of the energy detection algorithm that determines the channel status with over 99% accuracy. Through ns-3 simulation, we confirm that the proposed multi-carrier access scheme achieves up to 59% and 21.5% performance gain in userperceived throughput compared with the conventional LBT type A and type B, respectively. Since the legacy LAA has deployment problem, 3GPP and MulteFire alliance proposed unlicensed band stand-alone cellular communication system. However, conventional unlicensed band stand-alone cellular communication system has low transmission probability of uplink control messages. This disertation proposes W-ARQ: Wi-Fi assisted HARQ which put uplink control messages into Wi-Fi block ACK frame. In addition we propose parallel HARQ and clustered Minstrel to enhance throughput performance of W-ARQ. Our proposed algorithm shows high throughput performance where conventional MulteFire shows almost zero throughput performance. In summary, we analyze the performance of unlicensed-band cellular communication. By using the proposed model, we insist the legacy multi-carrier operation and HARQ of unlicensed cellular communication is not efficient. By this reason, we propose OOBE aware additional access and W-ARQ which achievee enhancements of network performance such as UPT and throughput compared with state-of-the-art techniques.Abstract i Contents iv List of Tables vii List of Figures viii 1 Introduction 1 1.1 Unlicensed Band Communication System . . . . . . . . . . . . . . . 1 1.2 Overview of Existing Approaches . . . . . . . . . . . . . . . . . . . 2 1.2.1 License-assisted access . . . . . . . . . . . . . . . . . . . . . 2 1.2.2 Further LAA . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2.3 Non-3GPP Unlicensed Band Cellular Communication . . . . 6 1.3 Main Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3.1 Performance Analysis of LTE-LAA . . . . . . . . . . . . . . 6 1.3.2 Out-of-Band Emission Aware Additional Carrier Access for LTE-LAA Network . . . . . . . . . . . . . . . . . . . . . . . 7 1.3.3 W-ARQ: Wi-Fi Assisted HARQ for Unlicensed Band StandAlone Cellular Communication System . . . . . . . . . . . . 8 1.4 Organization of the Dissertation . . . . . . . . . . . . . . . . . . . . 8 2 Performance Analysis of LTE-LAA network 10 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3 Proposed Markov-Chain Model . . . . . . . . . . . . . . . . . . . . . 14 2.3.1 Markov Property . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3.2 Markov Chain Model for EPS Type Variation . . . . . . . . . 16 2.3.3 LAA Network Throughput Estimation . . . . . . . . . . . . . 18 2.4 Model Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3 Out-of-Band Emission Aware Additional Carrier Access for LTE-LAA Network 35 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.2 Related work and Background . . . . . . . . . . . . . . . . . . . . . 37 3.2.1 Related work . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.2.2 Listen Before Talk . . . . . . . . . . . . . . . . . . . . . . . 38 3.2.3 Out-of-Band Emission . . . . . . . . . . . . . . . . . . . . . 39 3.3 Multi-carrier Operation of LTE-LAA . . . . . . . . . . . . . . . . . . 39 3.4 Carrier Sensing considering Out-of-Band Emission . . . . . . . . . . 47 3.4.1 Energy Detection Algorithm . . . . . . . . . . . . . . . . . . 49 3.4.2 Nominal Band Energy Detection . . . . . . . . . . . . . . . . 50 3.4.3 OOBE-Free Region Energy Detection . . . . . . . . . . . . . 51 3.5 Additional Carrier Access Scheme . . . . . . . . . . . . . . . . . . . 52 3.5.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . . . . . 52 3.5.2 Transmission Power Limitation . . . . . . . . . . . . . . . . 53 3.5.3 Dividing Transmission Burst . . . . . . . . . . . . . . . . . . 54 3.5.4 Short Subframe Decision . . . . . . . . . . . . . . . . . . . . 54 3.6 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 57 3.6.1 Performance of Energy Detection considering OOBE . . . . . 57 3.6.2 Simulation Environments . . . . . . . . . . . . . . . . . . . . 57 3.6.3 Performance of Proposed Carrier Access Scheme . . . . . . . 58 3.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4 W-ARQ: Wi-Fi Assisted HARQ for Unlicensed Band Stand-Alone Cellular Communication System 66 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.3 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.4 W-ARQ: Wi-Fi assisted HARQ for Unlicensed Band Stand-Alone Cellular Communication System . . . . . . . . . . . . . . . . . . . . . . 69 4.4.1 Parallel HARQ . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.4.2 Clustered Minstrel . . . . . . . . . . . . . . . . . . . . . . . 72 4.5 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5 Concluding Remarks 80 5.1 Research Contributions . . . . . . . . . . . . . . . . . . . . . . . . . 80 5.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Abstract (In Korean) 90 ๊ฐ์‚ฌ์˜ ๊ธ€ 93Docto

    Downlink channel access performance of NR-U: Impact of numerology and mini-slots on coexistence with Wi-Fi in the 5 GHz band

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    Coexistence between cellular systems and Wi-Fi gained the attention of the research community when LTE License Assisted Access (LAA) entered the unlicensed band. The recent introduction of NR-U as part of 5G introduces new coexistence opportunities because it implements scalable numerology (flexible subcarrier spacing and OFDM symbol lengths), and non-slot based scheduling (mini-slots), which considerably impact channel access. This paper analyzes the impact of NR-U settings on its coexistence with Wi-Fi networks and compares it with LAA operation using simulations and experiments. First, we propose a downlink channel access simulation model, which addresses the problem of the dependency and non-uniformity of transmission attempts of different nodes, as a result of the synchronization mechanism introduced by NR-U. Second, we validate the accuracy of the proposed model using FPGA-based LAA, NR-U, and Wi-Fi prototypes with over-the-air transmissions. Additionally, we show that replacing LAA with NR-U would not only allow to overcome the problem of bandwidth wastage caused by reservation signals but also, in some cases, to preserve fairness in channel access for both scheduled and random-access systems. Finally, we conclude that fair coexistence of the aforementioned systems in unlicensed bands is not guaranteed in general, and novel mechanisms are necessary for improving the sharing of resources between scheduled and contention-based technologies

    Towards Efficient and Enhanced Wireless Coexistence in the Unlicensed Spectrum

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    The 3rd Generation Partnership Project (3GPP) is developing the fifth generation (5G) of wireless broadband technology and has identified the unlicensed spectrum as a principal item on the plan of action. Listen-Before-Talk (LBT) has been recognized as the starting development point for the channel access scheme of future 5G New Radio-Unlicensed (NR-U) networks. Recent technical reports suggest that all sub-7 GHz unlicensed spectrum is targeted for 5G NR-U operation, including the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. Literature is inundated with research on Wi-Fi and LBT-based long-term evolution License-Assisted Access (LTE-LAA) wireless coexistence analysis. While a treasure trove of radio spectrum has been approved for license-exempt use in the 6 GHz band, industry and standard organizations must make sure it is well utilized by enhancing their coexistence schemes. A proper assessment of the homogeneous LBT deployment is imperative under the new use cases and regulatory circumstances. The work presented herein aimed to fill the gap and underline the importance of improving channel access mechanisms in next-generation wireless systems. The research in this dissertation first analyzed the LBT channel access scheme and analytically evaluated its performance in terms of a metrics set, such as effective channel utilization, collision probability, mean access delay, and temporal fairness among coexisting nodes. Outcomes of the developed analytical model revealed inefficiencies in various cases. For example, high priority classes generally hinder overall effective channel utilization, exhibit a high collision rate, and incur long latencies compared to lower priorities; and low priority classes sustain longer delays in class-heterogeneous scenarios. The developed framework was then utilized to investigate wireless coexistence in a 5G-enabled intensive care unit, employing remote patient monitoring over 5G NR-U. A modified LBT scheme is then proposed in this work to enhance overall channel efficiency in homogeneous LBT deployments by reducing the collision probability among coexisting stations based on the analytical investigation of the LBT mechanism. It is expected that low-power, narrowband frequency hoppers will be allowed to operate in the 6 GHz spectrum based on recent European Communications Committee (ECC) mandates, which raises speculation around coexistence with incumbent radio access technologies (RATs). To address the potential operation of cellular LBT in the 2.4 GHz and frequency hopping systems in the 5- and 6-GHz bands, the coexistence of Bluetooth Low Energy (BLE) 5 and LBT was investigated empirically in an anechoic chamber. The mutual impact was explored by means of throughput, packet error rate, and interframe delays. Empirical evaluation results demonstrated how BLE throughput dropped as the intended-to-unintended signal ratio decreased and the way in which LBT classes exhibited a diminishing effect as the class priority descended. Long Range BLE physical layer (PHY) was found to sustain longer gap times (i.e., delay) than the other two PHYs; however, the LR PHY showed less susceptibility to interference. Results also demonstrated that low data rate BLE PHYs hindered LBT throughput performance since they correspond to longer airtime durations

    A Survey of Resource Allocation Techniques for Cellular Networkโ€™s Operation in the Unlicensed Band

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    With an ever increasing demand for data, better and efficient spectrum operation has become crucial in cellular networks. In this paper, we present a detailed survey of various resource allocation schemes that have been considered for the cellular networkโ€™s operation in the unlicensed spectrum. The key channel access mechanisms for cellular networkโ€™s operation in the unlicensed bands are discussed. The various channel selection techniques are explored and their operation explained. The prime issue of fairness between cellular and Wi-Fi networks is discussed, along with suitable resource allocation techniques that help in achieving this fairness. We analyze the coverage, capacity, and impact of coordination in LTE-U systems. Furthermore, we study and discuss the impact and discussed the impact of various traffic type, environments, latency, handover, and scenarios on LTE-Uโ€™s performance. The new upcoming 5G New Radio and MulteFire is briefly described along with some of the critical aspects of LTE-U which require further research. ยฉ 2020 by the authors. Licensee MDPI, Basel, Switzerland

    Measurement and Optimization of LTE Performance

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    4G Long Term Evolution (LTE) mobile system is the fourth generation communication system adopted worldwide to provide high-speed data connections and high-quality voice calls. Given the recent deployment by mobile service providers, unlike GSM and UMTS, LTE can be still considered to be in its early stages and therefore many topics still raise great interest among the international scientific research community: network performance assessment, network optimization, selective scheduling, interference management and coexistence with other communication systems in the unlicensed band, methods to evaluate human exposure to electromagnetic radiation are, as a matter of fact, still open issues. In this work techniques adopted to increase LTE radio performances are investigated. One of the most wide-spread solutions proposed by the standard is to implement MIMO techniques and within a few years, to overcome the scarcity of spectrum, LTE network operators will offload data traffic by accessing the unlicensed 5 GHz frequency. Our Research deals with an evaluation of 3GPP standard in a real test best scenario to evaluate network behavior and performance
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