2,048 research outputs found

    Interference allocation for scheduler for green multimedia delivery

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    One of the key challenges in wireless networking is allocating the available radio resources to maximize key service delivery parameters such as the aggregate throughput and the multimedia quality of experience (QoE). We propose a novel and effective scheduling policy that allocates resource blocks, such that interference power is shifted toward capacity-saturated users, while improving the throughput of unsaturated users. The highlight of this paper is that the proposed scheme can dramatically improve the performance of cells that have a high discrepancy in its signal-to-noise ratio (SNR) distribution, which is typical in urban areas. The results show that a free-lunch (FL) solution is possible, whereby for negligible performance degradation in the saturated users, a large improvement in the nonsaturated users can be obtained. However, on average, the number of FL user pairings is low. By relaxing the degradation constraints, the non-FL (NFL) solution can yield a greater multiuser throughput gain. Motivated by a surge in mobile multimedia traffic, we further demonstrate that the proposed scheduling may have a profound impact on both energy efficiency and QoE of multimedia service delivery

    Fair Coexistence of Scheduled and Random Access Wireless Networks: Unlicensed LTE/WiFi

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    We study the fair coexistence of scheduled and random access transmitters sharing the same frequency channel. Interest in coexistence is topical due to the need for emerging unlicensed LTE technologies to coexist fairly with WiFi. However, this interest is not confined to LTE/WiFi as coexistence is likely to become increasingly commonplace in IoT networks and beyond 5G. In this article we show that mixing scheduled and random access incurs and inherent throughput/delay cost, the cost of heterogeneity. We derive the joint proportional fair rate allocation, which casts useful light on current LTE/WiFi discussions. We present experimental results on inter-technology detection and consider the impact of imperfect carrier sensing.Comment: 14 pages, 8 figures, journa

    Rate-Splitting Robustness in Multi-Pair Massive MIMO Relay Systems

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    Relay systems improve both coverage and system capacity. Toward this direction, a full-duplex (FD) technology, being able to boost the spectral efficiency by transmitting and receiving simultaneously on the same frequency and time resources, is envisaged to play a key role in future networks. However, its benefits come at the expense of self-interference (SI) from their own transmit signal. At the same time, massive multiple-input massive multiple-output systems, bringing unconventionally many antennas, emerge as a promising technology with huge degrees-of-freedom. To this end, this paper considers a multi-pair decode-and-forward FD relay channel, where the relay station is deployed with a large number of antennas. Moreover, the rate-splitting (RS) transmission has recently been shown to provide significant performance benefits in various multi-user scenarios with imperfect channel state information at the transmitter (CSIT). Engaging the RS approach, we employ the deterministic equivalent analysis to derive the corresponding sum-rates in the presence of interferences. Initially, numerical results demonstrate the robustness of RS in half-duplex (HD) systems, since the achievable sum-rate increases without bound, i.e., it does not saturate at high signal-to-noise ratio. Next, we tackle the detrimental effect of SI in FD. In particular, and most importantly, not only FD outperforms HD, but also RS enables increasing the range of SI over which FD outperforms HD. Furthermore, increasing the number of relay station antennas, RS appears to be more efficacious due to imperfect CSIT, since SI decreases. Interestingly, increasing the number of users, the efficiency of RS worsens and its implementation becomes less favorable under these conditions. Finally, we verify that the proposed DEs, being accurate for a large number of relay station antennas, are tight approximations even for realistic system dimensions.Peer reviewedFinal Accepted Versio

    Accurate non-intrusive residual bandwidth estimation in WMNs

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    The multi-access scheme of 802.11 wireless networks imposes difficulties in achieving predictable service quality in multi-hop networks. In such networks, the residual capacity of wireless links should be estimated for resource allocation services such as flow admission control. In this paper, we propose an accurate and non-intrusive method to estimate the residual bandwidth of an 802.11 link. Inputs from neighboring network activity measurements and from a basic collision detection mechanism are fed to the analytical model so that the proposed algorithm calculates the maximum allowable traffic level for this link. We evaluate the efficiency of the method via OPNET simulations, and show that the percent estimation error is significantly lower than two other prominent estimation methods, bounded only between 2.5-7.5%. We also demonstrate that flow admission control is successfully achieved in a realistic WMN scenario. Flow control through our proposed algorithm keeps the unsatisfied traffic demand bounded and at a negligibly low level, which is less than an order of magnitude of the other two methods

    A survey of IEEE 802.15.4 effective system parameters for wireless body sensor networks

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    This is the peer reviewed version of the following article: Moravejosharieh, Amirhossein, Lloret, Jaime. (2016). A survey of IEEE 802.15.4 effective system parameters for wireless body sensor networks.International Journal of Communication Systems, 29, 7, 1269-1292. DOI: 10.1002/dac.3098, which has been published in final form at http://doi.org/10.1002/dac.3098. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving[EN] Wireless body sensor networks are offered to meet the requirements of a diverse set of applications such as health-related and well-being applications. For instance, they are deployed to measure, fetch and collect human body vital signs. Such information could be further used for diagnosis and monitoring of medical conditions. IEEE 802.15.4 is arguably considered as a well-designed standard protocol to address the need for low-rate, low-power and low-cost wireless body sensor networks. Apart from the vast deployment of this technology, there are still some challenges and issues related to the performance of the medium access control (MAC) protocol of this standard that are required to be addressed. This paper comprises two main parts. In the first part, the survey has provided a thorough assessment of IEEE 802.15.4 MAC protocol performance where its functionality is evaluated considering a range of effective system parameters, that is, some of the MAC and application parameters and the impact of mutual interference. The second part of this paper is about conducting a simulation study to determine the influence of varying values of the system parameters on IEEE 802.15.4 performance gains. More specifically, we explore the dependability level of IEEE 802.5.4 performance gains on a candidate set of system parameters. Finally, this paper highlights the tangible needs to conduct more investigations on particular aspect(s) of IEEE 802.15.4 MAC protocol. Copyright (c) 2015 John Wiley & Sons, Ltd.Moravejosharieh, A.; Lloret, J. (2016). A survey of IEEE 802.15.4 effective system parameters for wireless body sensor networks. International Journal of Communication Systems. 29(7):1269-1292. https://doi.org/10.1002/dac.3098S12691292297Alrajeh, N. A., Lloret, J., & Canovas, A. (2014). A Framework for Obesity Control Using a Wireless Body Sensor Network. International Journal of Distributed Sensor Networks, 10(7), 534760. doi:10.1155/2014/534760Lopes I Silva B Rodrigues J Lloret J Proenca M A mobile health monitoring solution for weight control International Conference on Wireless Communications and Signal Processing (WCSP) Nanjing / China 2011 1 5Singh, N., Singh, A. K., & Singh, V. K. (2015). Design and performance of wearable ultrawide band textile antenna for medical applications. Microwave and Optical Technology Letters, 57(7), 1553-1557. doi:10.1002/mop.29131Lan, K., Chou, C.-M., Wang, T., & Li, M.-W. (2012). Using body sensor networks for motion detection: a cluster-based approach for green radio. Transactions on Emerging Telecommunications Technologies, 25(2), 199-216. doi:10.1002/ett.2559Lloret, J., Garcia, M., Catala, A., & Rodrigues, J. J. P. C. (2016). A group-based wireless body sensors network using energy harvesting for soccer team monitoring. International Journal of Sensor Networks, 21(4), 208. doi:10.1504/ijsnet.2016.079172Garcia M Catala A Lloret J Rodrigues J A wireless sensor network for soccer team monitoring International Conference on Distributed Computing in Sensor Systems and Workshops (DCOSS) Barcelona / Spain 2011 1 6Penders J Gyselinckx B Vullers R De Nil M Nimmala V van de Molengraft J Yazicioglu F Torfs T Leonov V Merken P Van Hoof C Human++: from technology to emerging health monitoring concepts 5th International Summer School and Symposium ISSS-MDBS on Medical Devices and Biosensors Hong Kong 2008 94 98Penders J Van de Molengraft J. 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    LTE-LAA ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ์œ„ํ•œ MAC ๊ณ„์ธต ๊ธฐ๋ฒ•

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ๊ณต๊ณผ๋Œ€ํ•™ ์ „๊ธฐยท์ปดํ“จํ„ฐ๊ณตํ•™๋ถ€, 2019. 2. ์ตœ์„ฑํ˜„.3GPP long term evolution (LTE) operation in unlicensed spectrum is emerging as a promising technology in achieving higher data rate with LTE since ultra-wide unlicensed spectrum, e.g., about 500 MHz at 5โ€“6 GHz range, is available in most countries. Recently, 3GPP has finalized standardization of licensed-assisted access (LAA) for LTE operation in 5 GHz unlicensed spectrum, which has been a playground only for Wi-Fi. In this dissertation, we propose the following three strategies to enhance the performance of LAA: (1) Receiver-aware COT adaptation, (2) Collision-aware link adaptation, and (3) Power and energy detection threshold adaptation. First, LAA has a fixed maximum channel occupancy time (MCOT), which is the maximum continuous transmission time after channel sensing, while Wi-Fi may transmit for much shorter time duration. As a result, when Wi-Fi coexists with LAA, Wi-Fi airtime and throughput can be much less than those achieved when Wi-Fi coexists with another Wi-Fi. To guarantee fair airtime and improve throughput of Wi-Fi, we propose a receiver-aware channel occupancy time (COT) adaptation ( RACOTA ) algorithm, which observes Wi-Fi aggregate MAC protocol data unit (A-MPDU) frames and matches LAAs COT to the duration of A-MPDU frames when any Wi-Fi receiver has more data to receive. Moreover, RACOTA detects saturation of Wi-Fi traffic and adjusts COT only if Wi-Fi traffic is saturated. We prototype saturation detection algorithm of RACOTA with commercial off-the-shelf Wi-Fi device and show that RACOTA detects saturation of Wi-Fi networks accurately. Through ns-3 simulations, we demonstrate that RACOTA provides airtime fairness between LAA and Wi-Fi while achieves up to 334% Wi-Fi throughput gain. Second, the link adaptation scheme of the conventional LTE, adaptive modulation and coding (AMC), cannot operate well in the unlicensed band due to intermittent collisions. Intermittent collisions make LAA eNB lower modulation and coding scheme (MCS) for the subsequent transmission and such unnecessarily lowered MCS significantly degrades spectral efficiency. To address this problem, we propose a collision-aware link adaptation algorithm ( COALA ). COALA exploits k-means unsupervised clustering algorithm to discriminate channel quality indicator (CQI) reports which are measured with collision interference and selects the most suitable MCS for the next transmission. By prototype-based experiments, we demonstrate that COALA detects collisions accurately, and by conducting ns-3 simulations in various scenarios, we also show that COALA achieves up to 74.9% higher user perceived throughput than AMC. Finally, we propose PETAL to mitigate the negative impact of spatial reuse (SR) operation. We first design the baseline algorithm, which operates SR aggressively, and show that the baseline algorithm degrades the throughput performance severely when the UE is close to an interferer. Our proposed algorithm PETAL estimates and compares the spectral efficiency for the SR operation and non-SR operation. Then, PETAL operates SR only if the spectral efficiency of SR operation is expected to be higher than the case of non-SR operation. Our simulation verifies the performance of PETAL in various scenarios. When two pair of an eNB and a UE coexists, PETAL improves the throughput by up to 329% over the baseline algorithm. In summary, we identify interesting problems that appeared with LAA and shows the impact of the problems through the extensive simulations and propose compelling algorithms to solve the problems. The airtime fairness between Wi-Fi and LAA is improved with COT adaptation. Furthermore, link adaptation accuracy and SR operation are improved by exploiting CQI reports history. The performance of the proposed schemes is verified by system level simulation.๋น„๋ฉดํ—ˆ ๋Œ€์—ญ์—์„œ์˜ LTE ๋™์ž‘์€ ๋” ๋†’์€ ๋ฐ์ดํ„ฐ ์ „์†ก๋ฅ ์„ ๋‹ฌ์„ฑํ•˜๋Š” ์œ ๋งํ•œ ๊ธฐ์ˆ ๋กœ ๋ถ€๊ฐ๋˜๊ณ  ์žˆ๋‹ค. ์ตœ๊ทผ 3GPP๋Š” ๊ธฐ์กด Wi-Fi ๊ธฐ์ˆ ์ด ์‚ฌ์šฉํ•˜๋˜ 5 GHz ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ์—์„œ LTE๋ฅผ ์‚ฌ์šฉํ•˜๋Š” licensed-assisted access (LAA) ๊ธฐ์ˆ ์˜ ํ‘œ์ค€ํ™”๋ฅผ ์™„๋ฃŒํ•˜์˜€๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ ์šฐ๋ฆฌ๋Š” LAA์˜ ์„ฑ๋Šฅ์„ ํ–ฅ์ƒ์‹œํ‚ค๊ธฐ ์œ„ํ•ด ๋‹ค์Œ๊ณผ ๊ฐ™์€ ์„ธ ๊ฐ€์ง€ ์ „๋žต์„ ์ œ์•ˆํ•œ๋‹ค: (1) ์ˆ˜์‹ ๊ธฐ ์ธ์‹ ์ฑ„๋„ ์ ์œ  ์‹œ๊ฐ„ ์ ์‘, (2) ์ถฉ๋Œ ์ธ์‹ ๋งํฌ ์ ์‘, (3) ์ „๋ ฅ ๋ฐ ์—๋„ˆ์ง€ ๊ฒ€์ถœ ์—ญ์น˜ ์ ์‘. ์ฒซ์งธ, LAA๋Š” ๊ณ ์ •๋œ ์ตœ๋Œ€ ์ฑ„๋„ ์ ์œ  ์‹œ๊ฐ„์„ ๊ฐ€์ง€๊ณ  ์žˆ๊ณ  ๊ทธ ์‹œ๊ฐ„ ๋งŒํผ ์—ฐ์†์ ์œผ๋กœ ์ „์†กํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐ˜๋ฉด, Wi-Fi๋Š” ๋น„๊ต์  ์งง์€ ์‹œ๊ฐ„ ๋™์•ˆ๋งŒ ์—ฐ์†์ ์œผ๋กœ ์ „์†กํ•  ์ˆ˜ ์žˆ๋‹ค. ๊ทธ ๊ฒฐ๊ณผ Wi-Fi๊ฐ€ LAA์™€ ๊ณต์กดํ•  ๋•Œ Wi-Fi์˜ airtime๊ณผ ์ˆ˜์œจ ์„ฑ๋Šฅ์€ Wi-Fi๊ฐ€ ๋˜ ๋‹ค๋ฅธ Wi-Fi์™€ ๊ณต์กดํ•  ๋•Œ์— ๋น„ํ•˜์—ฌ ์ €ํ•˜๋˜๊ฒŒ๋œ๋‹ค. ๋”ฐ๋ผ์„œ ์šฐ๋ฆฌ๋Š” Wi-Fi์˜ airtime๊ณผ ์ˆ˜์œจ ์„ฑ๋Šฅ์„ ํ–ฅ์ƒ์‹œํ‚ค๊ธฐ ์œ„ํ•˜์—ฌ Wi-Fi์˜ A-MPDU ํ”„๋ ˆ์ž„ ์ „์†ก ์‹œ๊ฐ„์— ๋งž์ถ”์–ด LAA์˜ ์ฑ„๋„ ์ ์œ  ์‹œ๊ฐ„์„ ์กฐ์ ˆํ•˜๋Š” ์ˆ˜์‹ ๊ธฐ ์ธ์‹ ์ฑ„๋„ ์ ์œ  ์‹œ๊ฐ„ ์ ์‘ ๊ธฐ๋ฒ•์ธ RACOTA๋ฅผ ์ œ์•ˆํ•œ๋‹ค. RACOTA ๋Š” ํฌํ™” ๊ฐ์ง€ ๊ฒฐ๊ณผ Wi-Fi ์ˆ˜์‹ ๊ธฐ๊ฐ€ ๋” ๋ฐ›์„ ๋ฐ์ดํ„ฐ๊ฐ€ ์žˆ๋‹ค๊ณ  ํŒ๋‹จ๋  ๋•Œ์—๋งŒ ์ฑ„๋„ ์ ์œ  ์‹œ๊ฐ„์„ ์กฐ์ ˆํ•œ๋‹ค. ์šฐ๋ฆฌ๋Š” RACOTA ์˜ ํฌํ™” ๊ฐ์ง€ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ƒ์šฉ Wi-Fi ์žฅ๋น„์— ๊ตฌํ˜„ํ•˜์—ฌ ์ด๋ฅผ ๋ฐ”ํƒ•์œผ๋กœ ์‹ค์ธก์„ ํ†ตํ•ด RACOTA ๊ฐ€ ๊ณต์กดํ•˜๋Š” Wi-Fi์˜ ํฌํ™” ์—ฌ๋ถ€๋ฅผ ์ •ํ™•ํ•˜๊ฒŒ ๊ฐ์ง€ํ•ด๋ƒ„์„ ๋ณด์ธ๋‹ค. ๋˜ํ•œ ์šฐ๋ฆฌ๋Š” ns-3 ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•˜์—ฌ RACOTA ๋ฅผ ์‚ฌ์šฉํ•˜๋Š” LAA๊ฐ€ ๊ณต์กดํ•˜๋Š” Wi-Fi์—๊ฒŒ ๊ณต์ •ํ•œ airtime์„ ์ œ๊ณตํ•˜๊ณ  ๊ธฐ์กด LAA์™€ ๊ณต์กดํ•˜๋Š” Wi-Fi ๋Œ€๋น„ ์ตœ๋Œ€ 334%์˜ Wi-Fi ์ˆ˜์œจ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ๊ฐ€์ ธ์˜ด์„ ๋ณด์ธ๋‹ค. ๋‘˜์งธ, ๊ฐ„ํ—์ ์ธ ์ถฉ๋Œ์ด ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋Š” ๋น„๋ฉดํ—ˆ ๋Œ€์—ญ์—์„œ๋Š” ๊ธฐ์กด LTE์˜ ๋งํฌ ์ ์‘ ๊ธฐ๋ฒ•์ธ adaptive modulation and coding (AMC)์ด ์ž˜ ๋™์ž‘ํ•˜์ง€ ์•Š์„ ์ˆ˜ ์žˆ๋‹ค. ๊ฐ„ํ—์ ์ธ ์ถฉ๋Œ์€ LAA ๊ธฐ์ง€๊ตญ์œผ๋กœ ํ•˜์—ฌ๊ธˆ modulation and coding scheme (MCS)์„ ๋‚ฎ์ถ”์–ด์„œ ๋‹ค์Œ ์ „์†ก์„ ํ•˜๋„๋ก ํ•˜๋Š”๋ฐ ๋‹ค์Œ ์ „์†ก ์‹œ์— ์ถฉ๋Œ์ด ๋ฐœ์ƒํ•˜์ง€ ์•Š๋Š”๋‹ค๋ฉด ๋ถˆํ•„์š”ํ•˜๊ฒŒ ๋‚ฎ์ถ˜ MCS๋กœ ์ธํ•ด ์ฃผํŒŒ์ˆ˜ ํšจ์œจ์ด ํฌ๊ฒŒ ์ €ํ•˜๋œ๋‹ค. ์ด๋Ÿฌํ•œ ๋ฌธ์ œ๋ฅผ ํ•ด๊ฒฐํ•˜๊ธฐ์œ„ํ•ด ์šฐ๋ฆฌ๋Š” ์ถฉ๋Œ ์ธ์‹ ๋งํฌ ์ ์‘ ๊ธฐ๋ฒ•์ธ COALA ๋ฅผ ์ œ์•ˆํ•œ๋‹ค. COALA ๋Š” k-means ๋ฌด๊ฐ๋… ํด๋Ÿฌ์Šคํ„ฐ๋ง ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์‚ฌ์šฉํ•˜์—ฌ channel quality indicator (CQI) ๋ฆฌํฌํŠธ ์ค‘ ์ถฉ๋Œ ๊ฐ„์„ญ์— ์˜ํ–ฅ์„ ๋ฐ›์€ CQI ๋ฆฌํฌํŠธ๋“ค์„ ๊ตฌ๋ณ„ํ•ด๋‚ด๊ณ  ์ด๋ฅผ ํ†ตํ•ด ๋‹ค์Œ ์ „์†ก์„ ์œ„ํ•œ ์ตœ์ ์˜ MCS๋ฅผ ์„ ํƒํ•œ๋‹ค. ์šฐ๋ฆฌ๋Š” ์‹ค์ธก์„ ํ†ตํ•˜์—ฌ COALA ๊ฐ€ ์ •ํ™•ํ•˜๊ฒŒ ์ถฉ๋Œ์„ ๊ฐ์ง€ํ•ด๋ƒ„์„ ๋ณด์ธ๋‹ค. ๋˜ํ•œ ์šฐ๋ฆฌ๋Š” ๋‹ค์–‘ํ•œ ํ™˜๊ฒฝ์—์„œ์˜ ns-3 ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•˜์—ฌ COALA ๊ฐ€ AMC ๋Œ€๋น„ ์ตœ๋Œ€ 74.9%์˜ ์‚ฌ์šฉ์ž ์ธ์‹ ์ˆ˜์œจ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ๊ฐ€์ ธ์˜ด์„ ๋ณด์ธ๋‹ค. ์…‹์งธ, ์šฐ๋ฆฌ๋Š” ๊ณต๊ฐ„ ์žฌ์‚ฌ์šฉ ๋™์ž‘์˜ ๋ถ€์ž‘์šฉ์„ ์ตœ์†Œํ™”ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ˆ˜์‹  ๋‹จ๋ง์„ ๊ณ ๋ คํ•˜์—ฌ ์ „์†ก ํŒŒ์›Œ ๋ฐ ์—๋„ˆ์ง€ ๊ฒ€์ถœ ์—ญ์น˜๋ฅผ ์ ์‘์ ์œผ๋กœ ์กฐ์ ˆํ•˜๋Š” PETAL ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ œ์•ˆํ•œ๋‹ค. ์šฐ๋ฆฌ๋Š” ๋จผ์ € ์ˆ˜์‹  ๋‹จ๋ง์„ ๊ณ ๋ คํ•˜์ง€ ์•Š๊ณ  ๊ณต๊ฒฉ์ ์œผ๋กœ ๊ณต๊ฐ„ ์žฌ์‚ฌ์šฉ ๋™์ž‘์„ ํ•˜๋Š” baseline ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์„ค๊ณ„ํ•˜๊ณ  ๋‹ค์–‘ํ•œ ํ™˜๊ฒฝ์—์„œ์˜ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•˜์—ฌ ์ˆ˜์‹  ๋‹จ๋ง์ด ๊ฐ„์„ญ์›์— ๊ฐ€๊นŒ์šด ๊ฒฝ์šฐ baseline ์•Œ๊ณ ๋ฆฌ์ฆ˜์˜ ์„ฑ๋Šฅ์ด ์‹ฌ๊ฐํ•˜๊ฒŒ ์—ดํ™”๋จ์„ ๋ณด์ธ๋‹ค. ์ œ์•ˆํ•˜๋Š” ์•Œ๊ณ ๋ฆฌ์ฆ˜์ธ PETAL ์€ ์ˆ˜์‹  ๋‹จ๋ง๋กœ๋ถ€ํ„ฐ ๋ฐ›์€ CQI ๋ฆฌํฌํŠธ ์ •๋ณด์™€ ์ฑ„๋„ ์ ์œ  ์‹œ์ ๊นŒ์ง€์˜ ํ‰๊ท  ๋Œ€๊ธฐ ์‹œ๊ฐ„์„ ์ด์šฉํ•˜์—ฌ ๊ณต๊ฐ„ ์žฌ์‚ฌ์šฉ ๋™์ž‘์„ ํ•  ๋•Œ ์˜ˆ์ƒ๋˜๋Š” ์ฃผํŒŒ์ˆ˜ ํšจ์œจ๊ณผ ๊ณต๊ฐ„ ์žฌ์‚ฌ์šฉ ๋™์ž‘์„ ํ•˜์ง€ ์•Š์„ ๋•Œ ์˜ˆ์ƒ๋˜๋Š” ์ฃผํŒŒ์ˆ˜ ํšจ์œจ์„ ๋น„๊ตํ•˜์—ฌ ๊ณต๊ฐ„ ์žฌ์‚ฌ์šฉ ๋™์ž‘์„ ํ•  ๋•Œ ์˜ˆ์ƒ๋˜๋Š” ์ฃผํŒŒ์ˆ˜ ํšจ์œจ์ด ๋” ํด ๋•Œ์—๋งŒ ๊ณต๊ฐ„ ์žฌ์‚ฌ์šฉ ๋™์ž‘์„ ํ•œ๋‹ค. ์šฐ๋ฆฌ๋Š” ๋‹ค์–‘ํ•œ ํ™˜๊ฒฝ์—์„œ์˜ ns-3 ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•˜์—ฌ PETAL ์ด baseline ์•Œ๊ณ ๋ฆฌ์ฆ˜ ๋Œ€๋น„ ์ตœ๋Œ€ 329%์˜ ์ˆ˜์œจ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ๊ฐ€์ ธ์˜ด์„ ๋ณด์ธ๋‹ค. ์š”์•ฝํ•˜์ž๋ฉด, ์šฐ๋ฆฌ๋Š” LAA์˜ ๋“ฑ์žฅ๊ณผ ํ•จ๊ป˜ ์ƒˆ๋กญ๊ฒŒ ๋Œ€๋‘๋˜๋Š” ํฅ๋ฏธ๋กœ์šด ๋ฌธ์ œ๋“ค์„ ํ™•์ธํ•˜๊ณ  ๋ฌธ์ œ๋“ค์˜ ์‹ฌ๊ฐ์„ฑ์„ ๋‹ค์–‘ํ•œ ํ™˜๊ฒฝ์—์„œ์˜ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•˜์—ฌ ์‚ดํŽด๋ณด๊ณ  ์ด ๋Ÿฌํ•œ ๋ฌธ์ œ๋“ค์„ ํ•ด๊ฒฐํ•  ์ˆ˜ ์žˆ๋Š” ์•Œ๊ณ ๋ฆฌ์ฆ˜๋“ค์„ ์ œ์•ˆํ•œ๋‹ค. Wi-Fi์™€ LAA ์‚ฌ์ด์˜ airtime ๊ณต์ •์„ฑ์€ LAA์˜ ์—ฐ์† ์ „์†ก ์‹œ๊ฐ„์„ ์ ์‘์ ์œผ๋กœ ์กฐ์ ˆํ•˜์—ฌ ๊ฐœ์„ ํ•  ์ˆ˜ ์žˆ๋‹ค. ๋˜ํ•œ ๋งํฌ ์ ์‘ ์ •ํ™•๋„์™€ ๊ณต๊ฐ„ ์žฌ์‚ฌ์šฉ ๋™์ž‘์˜ ํšจ์œจ์„ฑ์€ CQI ๋ฆฌํฌํŠธ๋“ค์˜ ๋ถ„ํฌ๋ฅผ ์ด์šฉํ•˜์—ฌ ๊ฐœ์„ ํ•  ์ˆ˜ ์žˆ๋‹ค. ์ œ์•ˆํ•˜๋Š” ์•Œ๊ณ ๋ฆฌ์ฆ˜๋“ค์˜ ์„ฑ๋Šฅ์€ ์‹œ์Šคํ…œ ๋ ˆ๋ฒจ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•˜์—ฌ ๊ฒ€์ฆ๋˜์—ˆ๋‹ค.1 Introduction 1 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Overview of Existing Approaches . . . . . . . . . . . . . . . . . . . 2 1.3 Main Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3.1 RACOTA: Receiver-Aware Channel Occupancy Time Adaptation for LTE-LAA . . . . . . . 2 1.3.2 COALA: Collision-Aware Link Adaptation for LTE-LAA . . 3 1.3.3 PETAL: Power and Energy Detection Threshold Adaptation for LAA . . . . . . . . . . . . . . 4 1.4 Organization of the Dissertation . . . . . . . . . . . . . . . . . . . . 5 2 RACOTA:Receiver-AwareChannelOccupancyTimeAdaptationforLTE- LAA 6 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3 MAC Mechanisms of Wi-Fi and LAA . . . . . . . . . . . . . . . . . 10 2.3.1 Wi-Fi MAC Operation . . . . . . . . . . . . . . . . . . . . . 10 2.3.2 LAA Listen-Before-Talk (LBT) Mechanism . . . . . . . . . . 11 2.3.3 Wide Bandwidth Operation . . . . . . . . . . . . . . . . . . 13 2.4 Coexistence performance of LAA and Wi-Fi . . . . . . . . . . . . . . 14 2.4.1 Simulation Setup . . . . . . . . . . . . . . . . . . . . . . . . 14 2.4.2 Unfairness between LAA and Wi-Fi . . . . . . . . . . . . . . 15 2.5 Receiver-Aware COT Adaptation Algorithm . . . . . . . . . . . . . . 17 2.5.1 Saturation Detection (SD) . . . . . . . . . . . . . . . . . . . 20 2.5.2 Receiver-Aware COT Decision . . . . . . . . . . . . . . . . . 22 2.6 Performance Evaluation of SD Algorithm . . . . . . . . . . . . . . . 22 2.6.1 Measurement Setup . . . . . . . . . . . . . . . . . . . . . . . 22 2.6.2 PPDUMaxTime Detection . . . . . . . . . . . . . . . . . . . 24 2.6.3 Saturation Detection Performance . . . . . . . . . . . . . . . 26 2.7 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.7.1 Saturated Traffic Scenario . . . . . . . . . . . . . . . . . . . 28 2.7.2 Unsaturated Traffic Scenario . . . . . . . . . . . . . . . . . . 30 2.7.3 Bursty Traffic Scenario . . . . . . . . . . . . . . . . . . . . . 30 2.7.4 Heterogeneous Wi-Fi Traffic Generation Scenario . . . . . . 31 2.7.5 Multiple Node Scenario . . . . . . . . . . . . . . . . . . . . 34 2.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3 COALA: Collision-Aware Link Adaptation for LTE-LAA 36 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3.2 Backgound and Related Work . . . . . . . . . . . . . . . . . . . . . 38 3.2.1 LAA and LBT . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.2.2 AMC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.2.3 Inter-Cell Interference Cancellation . . . . . . . . . . . . . . 39 3.2.4 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.3 Impact of Collision to Link Adaptation . . . . . . . . . . . . . . . . . 41 3.4 COALA: Collision-aware Link Adaptation . . . . . . . . . . . . . . . 47 3.4.1 CQI Clustering Algorithm . . . . . . . . . . . . . . . . . . . 48 3.4.2 Collision Detection and Collision Probability Estimation . . . 48 3.4.3 Suitable MCS Selection . . . . . . . . . . . . . . . . . . . . 49 3.5 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.5.1 Prototype-based Feasibility Study . . . . . . . . . . . . . . . 51 3.5.2 Contention Collision with LAA eNBs . . . . . . . . . . . . . 53 3.5.3 Hidden Collision . . . . . . . . . . . . . . . . . . . . . . . . 57 3.5.4 Bursty Hidden Collision . . . . . . . . . . . . . . . . . . . . 58 3.5.5 Contention Collision with Wi-Fi Transmitters . . . . . . . . . 58 3.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4 PETAL: Power and Energy Detection Threshold Adaptation for LAA 62 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.2 Backgound and Related Work . . . . . . . . . . . . . . . . . . . . . 64 4.2.1 Energy Detection Threshold . . . . . . . . . . . . . . . . . . 64 4.2.2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.3 Baseline Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.3.1 Design of the Baseline Algorithm . . . . . . . . . . . . . . . 65 4.3.2 Performance of the Baseline Algorithm . . . . . . . . . . . . 66 4.4 PETAL: Power and Energy Detection Threshold Adaptation . . . . . 68 4.4.1 CQI Management . . . . . . . . . . . . . . . . . . . . . . . . 69 4.4.2 Success Probability and Airtime Ratio Estimation . . . . . . . 69 4.4.3 CQI Clustering Algorithm . . . . . . . . . . . . . . . . . . . 71 4.4.4 SR Decision . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.5 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.5.1 Two Cell Scenario . . . . . . . . . . . . . . . . . . . . . . . 73 4.5.2 Coexistence with Standard LAA . . . . . . . . . . . . . . . . 75 4.5.3 Four Cell Scenario . . . . . . . . . . . . . . . . . . . . . . . 76 4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5 Concluding Remarks 79 5.1 Research Contributions . . . . . . . . . . . . . . . . . . . . . . . . . 79 Abstract (In Korean) 88 ๊ฐ์‚ฌ์˜ ๊ธ€ 92Docto
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