394 research outputs found
Long Term Evolution โ License Assisted Access (LTE-LAA): Modeling and Coexistence Performance Analysis
Wireless communication built upon radio spectrum plays an instrumental role in today's modern world. With the explosive growth of mobile data traffic, mobile cellular networks need more spectrum to boost their system capacity. Long Term Evolution (LTE) technology leveraging the unlicensed band is anticipated to provide a solution to address this challenge. However, ensuring fair operation in terms of spectrum sharing with current unlicensed spectrum incumbents remains a key challenge for the success and viability of Unlicensed LTE (U-LTE). In particular, fair co-existence between unlicensed LTE and the Institute of Electrical and Electronics Engineers (IEEE) 802.11x standard, known as Wi-Fi, remains a principal concern, due to the ubiquitous, high-throughput and high capacity nature of both technologies.
This work addresses the problem of modeling and evaluating the coexistence of LTE License-Assisted-Access (LTE-LAA) in the unlicensed band. The research work presents a novel analytical model using Markov Chain to accurately model the LAA Listen-Before-Talk (LBT) scheme, as specified in the final technical specification 36.213 of the 3rd Generation Partnership Project (3GPP) release 13 and 14. Model validation is demonstrated through numerical and simulation result comparison. Model performance evaluation is examined and contrasted with the IEEE 802.11 Distributed Coordination Function (DCF) and analysis results are subsequently presented and discussed herein. Finally, succeeding model development, a comprehensive coexistence performance analysis study is developed and completed examining the coexistence of homogeneous and heterogeneous network scenarios consisting of LTE-LAA and Wi-Fi nodes. As a result, the contribution of this work establishes a novel apparatus that facilitates numerical analysis of the LTE-LAA LBT mechanism and enables numerical comparison of future enhancements with the standardized LTE-LAA framework. In addition, this work delivers a delineating, unequivocal and in-depth examination of the effects and implications that the LTE-LAA LBT mechanism and its parameters have on coexistence performance of homogeneous and heterogeneous co-channel and co-located networks
Enhancing Coexistence in the Unlicensed Band with Massive MIMO
We consider cellular base stations (BSs) equipped with a large number of
antennas and operating in the unlicensed band. We denote such system as massive
MIMO unlicensed (mMIMO-U). We design the key procedures required to guarantee
coexistence between a cellular BS and nearby Wi-Fi devices. These include:
neighboring Wi-Fi channel covariance estimation, allocation of spatial degrees
of freedom for interference suppression, and enhanced channel sensing and data
transmission phases. We evaluate the performance of the so-designed mMIMO-U,
showing that it allows simultaneous cellular and Wi-Fi transmissions by keeping
their mutual interference below the regulatory threshold. The same is not true
for conventional listen-before-talk (LBT) operations. As a result, mMIMO-U
boosts the aggregate cellular-plus-Wi-Fi data rate in the unlicensed band with
respect to conventional LBT, exhibiting increasing gains as the number of BS
antennas grows.Comment: To appear in Proc. IEEE ICC 201
๋น๋ฉดํ๋์ญ ์ ๋ฃฐ๋ผ ํต์ ์ ์ํ ์ฑ๋ฅ ํฅ์ ๊ธฐ๋ฒ
ํ์๋
ผ๋ฌธ(๋ฐ์ฌ) -- ์์ธ๋ํ๊ต๋ํ์ : ๊ณต๊ณผ๋ํ ์ ๊ธฐยท์ ๋ณด๊ณตํ๋ถ, 2021.8. ๋ฐ์ธ์
.The 3rd generation partnership project (3GPP) has standardized long-term evolution (LTE) licensed-assisted access (LTE-LAA) that uses a wide unlicensed band as an alternative solution to the insufficient bandwidth problem of the existing LTE. 3GPP cellular communications in unlicensed spectrum allow transmission only after completing listen-before-talk (LBT) operation. For downlink, the LBT operation helps cellular traffic to coexist well with Wi-Fi traffic. However, cellular uplink transmission is attempted only at the time specifically determined by the base station after having a successful LBT and the user equipment (UE) may suffer transmission failure and delayed transmission due to Wi-Fi interference. As a result, cellular uplink traffic does not coexist well with Wi-Fi traffic. NR-U suffers from the collision issue because its channel access mechanism is similar to that of Wi-Fi. Wi-Fi solves the collision problem through the request-to-send/clear-to-send (RTS/CTS) mechanism. However, NR-U has no way of solving the collision problem. As a result, NR-U suffers severe performance degradation due to collisions as the number of contending nodes increases.
In this dissertation, we consider the following two enhancements to cellular communication in the unlicensed spectrum: (i) Uplink channel access enhancement for solving poor uplink performance and (ii) collision minimization for efficient channel utilization.
First, we mathematically analyze the problem of unfairness between cellular and Wi-Fi for uplink channel access.
To address the coexistence problem in unlicensed spectrum, we propose a standard-compliant approach, termed UpChance, which allows the UE to use a minimum length of uplink reservation signal (RS) and the base station to determine the optimal timing for the UE's uplink transmission. Through ns-3 simulation, we verify that UpChance improves the performance of fairness and random access completion time by up to 88% and 99%, respectively.
Second, we propose to extend an RS duration and use a split RS for reservation in NR-U that consists of front RS and rear RS and design a new collision minimization scheme, termed R-SplitC, that contains two components: new split RS operation and contention window size (CWS) control. New split RS operation helps to minimize collisions in NR-U transmissions, and CWS control works to protect the performance of other communication technologies such as Wi-Fi. We mathematically analyze and evaluate the performance of our scheme and confirm that R-SplitC improves network throughput by up to 100.6% compared to the baseline RS scheme without degrading Wi-Fi performance.
In summary, we propose standard-compliant uplink channel access enhancement scheme and collision minimization scheme for cellular communication in unlicensed spectrum. Through this research, we achieve enhancements of network performance such as throughput and fairness.3์ธ๋ ํํธ๋์ญ ํ๋ก์ ํธ๋ ๊ธฐ์กด LTE์ ๋ถ์กฑํ ๋์ญํญ ๋ฌธ์ ์ ๋ํ ๋์์ผ๋ก ๋์ ๋น๋ฉดํ ๋์ญ์ ์ฌ์ฉํ๋ ๋ผ์ด์ ์ค ์ง์ ์ ์์ ํ์คํํ๊ณ ์๋ค. ๋น๋ฉดํ ๋์ญ์์ 3GPP ์
๋ฃฐ๋ฌ ํต์ ์ LBT ๋์์ ์๋ฃํ ํ์๋ง ์ ์ก์ ํ์ฉํ๋ค. ๋ค์ด๋งํฌ์ ๊ฒฝ์ฐ LBT ์์
์ ํตํด ์
๋ฃฐ๋ฌ ํธ๋ํฝ์ด ์์ดํ์ด ํธ๋ํฝ๊ณผ ์ ๊ณต์กดํ ์ ์์ต๋๋ค. ๊ทธ๋ฌ๋, ์
๋ฃฐ๋ฌ ์
๋งํฌ ์ ์ก์ LBT ์ฑ๊ณต ํ ๊ธฐ์ง๊ตญ์ ์ํด ํน๋ณํ ๊ฒฐ์ ๋ ์๊ฐ์๋ง ์๋๋๋ฉฐ, ์ฌ์ฉ์ ์ฅ๋น๋ ์์ดํ์ด์ ๊ฐ์ญ์ผ๋ก ์ธํด ์ ์ก ์คํจ์ ์ ์ก ์ง์ฐ์ ๊ฒช์ ํ๋ฅ ์ด ๋๋ค. ๋ฐ๋ผ์ ์
๋ฃฐ๋ฌ ์
๋งํฌ ํธ๋ํฝ์ด ์์ดํ์ด ํธ๋ํฝ๊ณผ ์ ๊ณต์กดํ์ง ๋ชปํ๋ค. ๋ผ์ด์ ์ค ์ง์ ์ ์ ๊ธฐ์ ์ ๋ํ ์ฑ๋ ์ก์ธ์ค ๋ฉ์ปค๋์ฆ์ด ์์ดํ์ด์ ์ฑ๋ ์ก์ธ์ค ๋ฉ์ปค๋์ฆ๊ณผ ์ ์ฌํ๊ธฐ ๋๋ฌธ์ ๋์ ์ ์ก์ผ๋ก ์ถฉ๋ ๋ฌธ์ ๋ฅผ ๊ฒช๊ณ ์๋ค. ์์ดํ์ด๋ RTS/CTS ๋ฉ์ปค๋์ฆ์ ํตํด ์ถฉ๋ ๋ฌธ์ ๋ฅผ ํด๊ฒฐํ๋ค. ๊ทธ๋ฌ๋ ํ์ฌ ๋ผ์ด์ ์ค ์ง์ ์ ์ ๊ธฐ์ ์ ์ถฉ๋ ๋ฌธ์ ๋ฅผ ํด๊ฒฐํ ๋ฐฉ๋ฒ์ด ์กด์ฌํ์ง ์๋๋ค.
๋ฐ๋ผ์ ๋ผ์ด์ ์ค ์ง์ ์ ์ ๊ธฐ์ ์ ๊ฒฝํฉ ๋
ธ๋ ์๊ฐ ์ฆ๊ฐํจ์ ๋ฐ๋ผ ์ถฉ๋๋ก ์ธํด ์ฌ๊ฐํ ์ฑ๋ฅ ์ ํ๋ฅผ ๊ฒช๋๋ค.
๋ณธ ๋
ผ๋ฌธ์์๋ ๋น๋ฉดํ ๋์ญ์์ ์
๋ฃฐ๋ฌ ํต์ ์ ๋ํ ๋ค์๊ณผ ๊ฐ์ ๋ ๊ฐ์ง ๊ฐ์ ์ ๊ณ ๋ คํ๋ค. (i) ์
๋งํฌ ์ฑ๋ฅ ์ ํ๋ฅผ ํด๊ฒฐํ๊ธฐ ์ํ ์
๋งํฌ ์ฑ๋ ์ก์ธ์ค ํฅ์ ๋ฐ (ii) ํจ์จ์ ์ธ ์ฑ๋ ํ์ฉ์ ์ํ ์ถฉ๋ ์ต์ํ.
์ฒซ์งธ, ์
๋งํฌ ์ฑ๋ ์ก์ธ์ค๋ฅผ ์ํ ์
๋ฃฐ๋ฌ์ ์์ดํ์ด ์ฌ์ด์ ๋ถ๊ณต์ ์ฑ ๋ฌธ์ ๋ฅผ ์ํ์ ์ผ๋ก ๋ถ์ํ๋ค. ๋น๋ฉดํ ๋์ญ์์์ ๊ณต์กด ๋ฌธ์ ๋ฅผ ํด๊ฒฐํ๊ธฐ ์ํด, ์ฐ๋ฆฌ๋ ๋จ๋ง์ด ์ต์ ๊ธธ์ด์ ์
๋งํฌ ์์ฝ ์ ํธ๋ฅผ ์ฌ์ฉํ๊ณ ๊ธฐ์ง๊ตญ์ด ๋จ๋ง์ ์
๋งํฌ ์ ์ก์ ๋ํ ์ต์ ์ ํ์ด๋ฐ์ ๊ฒฐ์ ํ ์ ์๋ UpChance๋ผ๋ ํ์ค์ ๋ง์กฑํ๋ ์ํฅ ๋งํฌ ์ฑ๋ ์ ๊ทผ ๋ฐฉ์์ ์ ์ํ๋ค. ns-3 ์๋ฎฌ๋ ์ด์
์ ํตํด UpChance๊ฐ ๊ณต์ ์ฑ๊ณผ ๋๋ค ์ก์ธ์ค ์๋ฃ ์๊ฐ์ ๊ฐ๊ฐ ์ต๋ 88%, 99% ํฅ์์ํค๋ ๊ฒ์ ๊ฒ์ฆํ๋ค.
๋์งธ, ์ฐ๋ฆฌ๋ ์ ๋ฐฉ ์์ฝ์ ํธ์ ํ๋ฐฉ ์์ฝ์ ํธ๋ก ๊ตฌ์ฑ๋ ๋ถํ ์์ฝ ์ ํธ๋ฅผ ์ฌ์ฉํ๊ณ ๊ฒฝํฉ ์ฐฝ ํฌ๊ธฐ๋ฅผ ์ถ๊ฐ์ ์ผ๋ก ์ ์ดํ๋ R-SplitC๋ผ๋ ์๋ก์ด ์ถฉ๋ ์ต์ํ ์ฒด๊ณ๋ฅผ ์ ์ํ๋ค. ์๋ก์ด ๋ถํ ์์ฝ ์ ํธ๋ ๋ผ์ด์ ์ค ์ง์ ์ ์ ๊ธฐ์ ์ ์ ์ก๊ฐ์ ์ถฉ๋์ ์ต์ํํ๋ ๋ฐ ๋์์ ์ฃผ๋ฉฐ, ๊ฒฝํฉ ์ฐฝ ํฌ๊ธฐ ์ ์ด๋ ์์ดํ์ด์ ๊ฐ์ ๋ค๋ฅธ ํต์ ๊ธฐ์ ์ ์ฑ๋ฅ์ ๋ณดํธํ๋ค. ์ฐ๋ฆฌ๋ ์ฐ๋ฆฌ ์ฒด๊ณ์ ์ฑ๋ฅ์ ์ํ์ ์ผ๋ก ๋ถ์ํ๊ณ ํ๊ฐํ์ฌ R-SplitC๊ฐ ์์ดํ์ด ์ฑ๋ฅ์ ์ ํ์ํค์ง ์๊ณ ๊ธฐ์กด์ ์์ฝ ์ ํธ ์ฒด๊ณ์ ๋นํด ๋คํธ์ํฌ ์ฒ๋ฆฌ๋์ ์ต๋ 100.6% ํฅ์์ํค๋ ๊ฒ์ ํ์ธํ๋ค.
์์ฝํ๋ฉด, ์ฐ๋ฆฌ๋ ๋น๋ฉดํ ๋์ญ์์ ์
๋ฃฐ๋ฌ ํต์ ์ ์ํ ์
๋งํฌ ์ฑ๋ ์ก์ธ์ค ํฅ์ ๊ธฐ๋ฒ ๋ฐ ์ถฉ๋ ์ต์ํ ๊ธฐ๋ฒ์ ์ ์ํ๋ค.
๋ณธ ์ฐ๊ตฌ๋ฅผ ํตํด, ์ฐ๋ฆฌ๋ ์ต์ฒจ๋จ ๊ธฐ์ ์ ๋นํด ์ฒ๋ฆฌ๋ ๋ฐ ๊ณต์ ์ฑ๊ณผ ๊ฐ์ ๋คํธ์ํฌ ์ฑ๋ฅ์ ํฅ์์ ๋ฌ์ฑํ๋ค.1 Introduction 1
1.1 Motivation 1
1.2 Main Contributions 2
1.2.1 Uplink Channel Access Enhancement for Cellular Communication in Unlicensed Spectrum 2
1.2.2 R-SplitC: Collision Minimization for Cellular Communication in Unlicensed Spectrum 3
1.3 Organization of the Dissertation 4
2 Uplink Channel Access Enhancement for Cellular Communication in Unlicensed Spectrum 5
2.1 Introduction 5
2.2 Related Work and Preliminaries 7
2.2.1 Related Work 7
2.2.2 Preliminaries 8
2.3 Mathematical Analysis for Unfairness between Uplink Cellular and Wi-Fi 10
2.3.1 PRACH scenario 10
2.3.2 UL data scenario 13
2.4 Proposed Scheme 17
2.4.1 UE Operation 18
2.4.2 eNB Operation 19
2.5 Performance Evaluation 24
2.5.1 Simulation Environments 24
2.5.2 UL data transmission 25
2.5.3 Random access 27
2.6 Summary 29
3 R-SplitC: Collision Minimization for Cellular Communication in Unlicensed Spectrum 37
3.1 Introduction 37
3.2 Related Work and Preliminaries 39
3.2.1 Related Work 39
3.2.2 NR-U 40
3.2.3 listen-before-talk (LBT) 41
3.2.4 reservation signal and mini-slot 41
3.2.5 Wi-Fi 42
3.3 Proposed Scheme 44
3.3.1 New RS structure 46
3.3.2 CWS control 48
3.4 Performance Analysis 49
3.4.1 Throughput Analysis for R-Split 49
3.4.2 Throughput Analysis for R-SplitC 55
3.5 Performance Evaluation 57
3.5.1 Performance Evaluation for an NR-U only Network 58
3.5.2 Performance Evaluation for an NR-U/Wi-Fi Network 61
3.6 Summary 65
4 Concluding Remarks 67
4.1 Research Contributions 67
4.2Future Work 68
Abstract (In Korean) 75
๊ฐ์ฌ์๊ธ 78๋ฐ
LTE and Wi-Fi Coexistence in Unlicensed Spectrum with Application to Smart Grid: A Review
Long Term Evolution (LTE) is expanding its utilization in unlicensed band by
deploying LTE Unlicensed (LTEU) and Licensed Assisted Access LTE (LTE-LAA)
technology. Smart Grid can take the advantages of unlicensed bands for
achieving two-way communication between smart meters and utility data centers
by using LTE-U/LTE-LAA. However, both schemes must co-exist with the incumbent
Wi-Fi system. In this paper, several co-existence schemes of Wi-Fi and LTE
technology is comprehensively reviewed. The challenges of deploying LTE and
Wi-Fi in the same band are clearly addressed based on the papers reviewed.
Solution procedures and techniques to resolve the challenging issues are
discussed in a short manner. The performance of various network architectures
such as listenbefore- talk (LBT) based LTE, carrier sense multiple access with
collision avoidance (CSMA/CA) based Wi-Fi is briefly compared. Finally, an
attempt is made to implement these proposed LTEWi- Fi models in smart grid
technology.Comment: submitted in 2018 IEEE PES T&
Survey of Spectrum Sharing for Inter-Technology Coexistence
Increasing capacity demands in emerging wireless technologies are expected to
be met by network densification and spectrum bands open to multiple
technologies. These will, in turn, increase the level of interference and also
result in more complex inter-technology interactions, which will need to be
managed through spectrum sharing mechanisms. Consequently, novel spectrum
sharing mechanisms should be designed to allow spectrum access for multiple
technologies, while efficiently utilizing the spectrum resources overall.
Importantly, it is not trivial to design such efficient mechanisms, not only
due to technical aspects, but also due to regulatory and business model
constraints. In this survey we address spectrum sharing mechanisms for wireless
inter-technology coexistence by means of a technology circle that incorporates
in a unified, system-level view the technical and non-technical aspects. We
thus systematically explore the spectrum sharing design space consisting of
parameters at different layers. Using this framework, we present a literature
review on inter-technology coexistence with a focus on wireless technologies
with equal spectrum access rights, i.e. (i) primary/primary, (ii)
secondary/secondary, and (iii) technologies operating in a spectrum commons.
Moreover, we reflect on our literature review to identify possible spectrum
sharing design solutions and performance evaluation approaches useful for
future coexistence cases. Finally, we discuss spectrum sharing design
challenges and suggest future research directions
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