- Frequency Sharing of Wi-Fi/LTE-U -

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 협동과정 기술경영·경제·정책전공, 2020. 8. Jorn Altmann .5세대(5G) 이동통신 확산을 위하여 정부는 '비면허 5G' 주파수 대역인 6GHz 대역폭에 최대 1.2㎓ 폭을 공급할 예정이다. 4차 산업에 대응하여 기업이 스마트 공장에 적합한 맞춤형 5G망을 구축하기 위한 목적이다. 과학기술정보통신부(MSIT)는 6㎓ 대역 대상으로 비면허 주파수 대역의 5G 연구반을 가동, 주파수 분배 방안 수립과 기술 기준 제정에 착수한 것으로 확인됐다. 비면허 5G(NR-U)는 정부가 개방한 비면허 주파수 대역에 5G 코어망과 기지국 등 표준 기술을 적용해 초저지연초고속 성능을 구현하는 기술로, 6월 국제민간표준화기구(3GPP) 상용화를 앞두고 있다. 그러나 5/6GHz 대역의 주파수는 와이파이와 LTE-LAA가 공존하게 될 영역으로 이해관계자들의 주장이 엇갈리고 있다. LBT (Listen-Before-Talk)는 비면허 주파수를 공유하는 방법으로 기술적/행정적 방안으로, 채널을 분석하여 데이터를 전송하기 가장 적절한 주파수대역을 선출하는 방법중에 하나이다. 이 대역을 선출하기 위한 기술 방법은 CCA (Clear Channel Assessment)라고 한다. 이 기술은 LTE 통신사업자들이 개발한 기술로 구체화된 기술표준을 요구하고 있다. 하지만, 이 기술을 와이파이 사업자 입장에서는 이 기술의 실제 실용가능 여부에 대해 의구심을 갖고 있다. 그 이유는 해당 기술이 지나치게 LTE 통신사업자들에게 유리하게 개발된 기술이라는 논쟁이 있기 때문이다. 이에 통신기술정책 결정자는 양측이 공존할 수 있는 법 제정방안을 강구해야 하며, 이 논문에서는 기존 와이파이 사용자들을 보호하며 통신 사업자들 역시 주파수를 공유할 수 있는 제도 정책의 방법을 정책자 입장에서 연구해보자 한다. 비면허 주파수를 개방하게 되었을 때 채널 사용자 비율과 라이선스 배부 비율 사이의 효율성에 대해 연구하였다. 그리고, 사용 가능한 채널을 비교하는 방법을 기존연구를 통해 비교하고 새로운 모델을 개발 했다. 또 기술 표준으로 이미 제정 된 노이즈 한계치가 실제 공유가 됐을 때 어떤식으로 작용되는 지를 알아보기 위해 시뮬레이션 분석을 통해 예측해 보았다.A spectrum-sharing policy is yet to be established for unlicensed bands. There are several controversies related to providing 5-GHz (5G) band service with the coexistence of Wi-Fi and LTE–LAA (License Assisted Access). LTE–LAA is a technical and political scheme for sharing spectrum bands. Using this technique, the channel can be evaluated, and a proper channel can be selected before data transmission. This mechanism is called listen before talk (LBT), and the channel selection procedure is called clear channel assessment (CCA). LTE service providers suggest standardizing this technology using an unlicensed band. However, existing Wi-Fi users are skeptical about the sharing process. In this paper, we describe proper spectrum-sharing mechanisms based on policy-based channel selection algorithms. Based on the results, proper regulation of the 5G LTE-U is required to avoid conflicts among service providers. This work uses a policy-based mechanism to understand the role of the government in managing these bands. The main idea is that stricter sharing-policy regulations and higher thresholds must be implemented to protect the rights of existing users.1. Introduction 1 1.1 Research Background 1 1.2 Problem Description 2 1.2.1 Controversies on Wi-Fi and LTE-U Coexistence 2 1.3 Research Question 4 1.3.1. Fairness and Efficiency of Sharing Policy 4 1.3.2. Evaluation and Simulation of Sharing Technology 5 1.4 Contribution 5 2. Literature Review 6 2.1 Spectrum-Sharing Policy 6 2.1.2 Case of South Korea 8 2.2 Spectrum-Sharing Technologies 10 2.2.1 Licensed Assisted Access (LAA) 11 2.2.2 Listen Before Talk (LBT) 13 2.2.2.1 Qualcomm Evaluation 13 2.2.2.2 3GPP Evaluation 16 2.3 Comparison with Previous Work 17 3. Modeling 20 3.1 General Assumption 22 3.2 Flow Chart 23 3.2.1 License Type Evaluation (Guard Interval Evaluation) 23 3.2.2 Energy Detection Evaluation 26 4. Simulation 29 4.1 Parameter setting 29 4.2 Simulation Result 31 5. Conclusion 36 5.1 Overall Implication 36 5.2 Limitation 37 5.3 Further study 37 Appendix 39 Bibliography 47 Abstract (Korean) 50Maste

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