[발표] 2015개정 실과 교육과정 ‘가정생활’ 영역 개발 방향

Long term evolution (LTE) carrier aggregation with 5 GHz unlicensed national informational infrastructure band has been pointed out by the industry as a good solution to handle the rapidly increasing amounts of data traffic. To provide fair coexistence of LTE-licensed assisted access (LTE-LAA) and Wi-Fi on 5 GHz, several coexistence mechanisms have already been proposed. This paper provides a comprehensive survey of the coexistence of LTE-LAA and Wi-Fi on 5 GHz with corresponding deployment scenarios. We first analyze coexistence-related features of those two technologies, including motivation, LTE carrier aggregation with unlicensed band, LTE and Wi-Fi medium access control protocols comparison, coexistence challenges and enablers, performance difference between LTE-LAA and Wi-Fi, as well as co-channel interference. Second, we further extensively discuss current considerations about the coexistence of LTE-LAA and Wi-Fi. Third, influential factors for the classification of small cell scenarios, as well as four representative scenarios are investigated in detail. Then we explore a relatively smooth technical route for solving coexistence-related problems, which practically takes features of a specific scenario as the base for designing deployment mode of LTE-LAA and/or Wi-Fi. A scenario-oriented decision making procedure for the coexistence issue and the analysis on an example deployment scenario, including design and performance evaluation metrics focusing on the concept of the scenario-oriented coexistence are presented. We finally forecast further research trends on the basis of our conclusion.

Coexistence of LTE-LAA and Wi-Fi on 5 GHz With Corresponding Deployment Scenarios: A Survey

On a fair coexistence of LTE and Wi-Fi in the unlicensed spectrum: A Survey

The dramatic growth in demand for mobile data has prompted mobile network operators (MNOs) to explore spectrum sharing in unlicensed bands. MNOs have been allowed recently to operate their LTE services over the 5 GHz Unlicensed National Information Infrastructure (U-NII) bands, currently occupied by Wi-Fi. The unlicensed LTE operation has been standardized by 3GPP under the name Licensed Assisted Access (LAA). Unlicensed 5G New radio (NR) operation over the U-NII bands, a.k.a., NR-Unlicensed (NR-U), is also being explored. To support applications with diverse Quality-of-Service (QoS) requirements, LAA, NR-U, and Wi-Fi technologies offer multiple priority classes with different contention parameters for accessing an unlicensed channel. How these different classes affect the interplay between coexisting MNOs and Wi-Fi systems is still a relatively under-explored topic. In this paper, we develop a simple yet efficient framework for fair coexistence between LTE MNOs and Wi-Fi systems, each with multiple priority classes. We derive approximated closed-form solutions for the probability of successful transmission (PST), average contention delay, and average throughput when coexisting LAA and Wi-Fi devices serve traffic with different priority classes. LTE and Wi-Fi operators can fit our solutions to estimate the performance of both systems in offline or online fashions, and use them to further optimize their system throughput and latency. Our results reveal that PSTs computed with our approximate models are within 5% difference with those obtained via close-to-real simulation under dense network deployments and high traffic loads.

Harmonious Cross-Technology Coexistence With Heterogeneous Traffic in Unlicensed Bands: Analysis and Approximations

The explosive emergence of wireless technologies and standards, covering licensed and unlicensed spectrum bands, has triggered the appearance of a huge amount of wireless technologies, with many of them competing for the same spectrum band instead of harmoniously sharing it. Unfortunately, the wireless spectrum is a scarce resource, and the available frequency bands will not scale with the foreseen demand for new capacity. Certain parts of the spectrum, in particular the license-free ISM bands, are overcrowded, while other parts, mostly licensed bands, may be significantly underutilized. As such, there is a need to introduce more advanced techniques to access and share the wireless medium, either to improve the coordination within a given band or to explore the possibilities of intelligently using unused spectrum in underutilized (e.g., licensed) bands. Therefore, in this paper, we present an open source software-defined radio-based framework that can be employed to devise disruptive techniques to optimize the sub-optimal use of radio spectrum that exists today. We describe three use cases where the framework can be employed along with intelligent algorithms to achieve improved spectrum utilization. In addition, we provide several experimental results showing the performance and effectiveness of the proposed framework.

https://biblio.ugent.be/publication/8583125/file/8583126.pdf

A Spectrum Sharing Framework for Intelligent Next Generation Wireless Networks

3GPP is introducing Licensed Assisted Access (LAA) in Release 13 [1], for LTE operation in unlicensed bands, to provide high data rate and to reduce the load on licensed spectrum. One of the mandatory functionalities of LAA is Listen Before Talk (LBT) to co-exist fairly with other technologies in unlicensed bands like Wi-Fi. Contention Window (CW) adjustment is one of the important issues in LAA LBT. Hence in this paper, we propose a dynamic CW adjustment algorithm for LAA based on channel sensing and then evaluated the performance of Wi-Fi in Wi-Fi - Wi-Fi and LAA - Wi-Fi scenarios. Our simulation results show that LAA with proposed CW adjustment algorithm can fairly co-exist with Wi-Fi.

Channel sensing based dynamic adjustment of contention window in LAA-LTE networks

A novel coexistence scheme for IEEE 802.11 for user fairness and efficient spectrum utilization in the presence of LTE-U

Due to the scarcity of licensed spectrum, Long-Term Evolution (LTE) operation in unlicensed spectrum is a promising solution to provide high data rate and to reduce the load on licensed spectrum. In Release 13, 3GPP introduced LTE in Unlicensed (LTE-U) as Licensed Assisted Access (LAA). In LTE-U, Carrier Aggregation (CA) feature aggregates licensed and unlicensed spectrum to get higher bandwidth. Use of unlicensed spectrum by Wi-Fi and LTE-U networks results in more interference because of lack of coordination and thereby makes it challenging for LTE-U operators to select best component carrier from available unlicensed carriers in case of dense deployments. In this paper, for efficient LTE-U operation, we propose dynamic Unlicensed Component Carrier Selection (UCCS) algorithm which minimizes interference from other networks (Wi-Fi and LTE-U). The algorithm considers fairness factor to achieve better performance for each User Equipment (UE). Further, the user offloading algorithm offloads those UE(s) to licensed carrier that are getting lesser throughput due to interference from adjacent cells operating on the same unlicensed carrier. The simulation results show that the proposed algorithm outperforms Random and Least Received Power channel selection schemes.

Unlicensed Carrier Selection and User Offloading in Dense LTE-U Networks

The Licensed Assisted Access (LAA) is shown as a required technology to avoid overcrowding of the licensed bands by the increasing cellular traffic. Proposed by 3GPP, LAA uses a Listen Before Talk (LBT) and backoff mechanism similar to Wi-Fi. While many mathematical models have been proposed to study the problem of the coexistence of LAA and Wi-Fi systems, few have tackled the problem of QoS provisioning, and in particular analysed the behaviour of the various classes of priority available in Wi-Fi and LAA. This paper presents a new mathematical model to investigate the performance of different priority classes in coexisting Wi-Fi and LAA networks. Using Discrete Time Markov Chains, we model the saturation throughput of all eight priority classes used by Wi-Fi and LAA. The numerical results show that with the 3GPP proposed parameters, a fair coexistence between Wi-Fi and LAA cannot be achieved. Wi-Fi users in particular suffer a significant degradation of their performance caused by the collision with LAA transmissions which has a longer duration compared to Wi-Fi transmissions.

/pdf/modelling-and-analysis-of-wi-fi-and-laa-coexistence-with-4woutlujnl.pdf

Modelling and Analysis of Wi-Fi and LAA Coexistence with Priority Classes

The deployment of LTE in unlicensed spectrum is a plausible solution to meet explosive traffic demand from mobile users. However, fair coexistence with the existing unlicensed technologies, mainly Wi-Fi, needs to be ensured before any such deployment. Duty cycled LTE (LTE-U) is a simple and an easily adaptable scheme which helps in fair coexistence with the Wi-Fi. Nonetheless, the immense deployment of Wi-Fi necessitates a user-oriented study to find the effects of LTE-U operation, primarily in scenarios where the LTE-U eNB remains hidden from Wi-Fi Access Point. To comprehend these effects, we perform a user-level throughput study of Wi-Fi in the presence of LTE-U using a testbed and observe a clear unfairness in throughput distribution among Wi-Fi users. Furthermore, we also notice inability among the disadvantaged users to receive the periodic Wi-Fi beacon frames successfully. The reasons and the subsequent consequences, of throughput unfairness and beacon losses, are carefully elaborated. Also, to validate the beacon loss results, we present a beacon loss analysis which provides a mathematical expression to find the beacon loss percentage. Finally, we examine the results and highlight a need for incorporating additional functionalities in either LTE-U or Wi-Fi to overcome the present challenges.

/pdf/lte-u-and-wi-fi-hidden-terminal-problem-how-serious-is-it-y4jrkfpr90.pdf

Anand M. Baswade

Papers

Channel sensing based dynamic adjustment of contention window in LAA-LTE networks

A novel coexistence scheme for IEEE 802.11 for user fairness and efficient spectrum utilization in the presence of LTE-U

Unlicensed Carrier Selection and User Offloading in Dense LTE-U Networks

Modelling and Analysis of Wi-Fi and LAA Coexistence with Priority Classes

LTE-U and Wi-Fi hidden terminal problem: How serious is it for deployment consideration?