Control-Data Separation With Decentralized Edge Control in Fog-Assisted Uplink Communications

Kang, Jinkyu,Simeone, Osvaldo,Kang, Joonhyuk,Shamai Shitz, Shlomo IEEE 2018 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.17 No.6

<P>Fog-aided network architectures for 5G systems encompass wireless edge nodes, referred to as remote radio systems (RRSs), as well as remote cloud center (RCC) processors, which are connected to the RRSs via a fronthaul access network. RRSs and RCC are operated via network functions virtualization, enabling a flexible split of network functionalities that adapts to network parameters such as fronthaul latency and capacity. This paper focuses on uplink communications and investigates the cloud-edge allocation of two important network functions, namely, the control functionality of rate selection and the data-plane function of decoding. Three functional splits are considered: 1) distributed radio access network, in which both functions are implemented in a decentralized way at the RRSs; 2) cloud RAN, in which instead both functions are carried out centrally at the RCC; and 3) a new functional split, referred to as fog RAN (F-RAN), with separate decentralized edge control and centralized cloud data processing. The model under study consists of a time-varying uplink channel with fixed scheduling and cell association in which the RCC has global but delayed channel state information due to fronthaul latency, while the RRSs have local but more timely CSI. Using the adaptive sum-rate as the performance criterion, it is concluded that the F-RAN architecture can provide significant gains in the presence of user mobility.</P>

Fronthaul Compression and Precoding Design for C-RANs Over Ergodic Fading Channels

Kang, Jinkyu,Simeone, Osvaldo,Kang, Joonhyuk,Shamai, Shlomo IEEE 2016 IEEE Transactions on Vehicular Technology VT Vol.65 No.7

<P>This paper investigates the joint design of fronthaul compression and precoding for the downlink of cloud radio access networks (C-RANs). In a C-RAN, a central unit (CU) controls a cluster of radio units (RUs) through low-latency fronthaul links. Most previous works on the design of fronthaul compression and precoding assume constant channels and instantaneous channel state information (CSI) at the CU. This paper, in contrast, concentrates on a more practical scenario with block-ergodic channels and considers either instantaneous or stochastic CSI at the CU. Moreover, the analysis encompasses two types of CU-RU functional splits at the physical layer, which we refer to as compression-after-precoding (CAP) and compression-before-precoding (CBP). With the CAP approach, which is the standard C-RAN solution, all baseband processing is done at the CU. With the CBP scheme, channel encoding and precoding are instead performed at the RUs: The CU does not perform precoding but rather forwards separately the information messages of a subset of mobile stations (MSs) along with the compressed precoding matrices to each RU. Optimization algorithms over fronthaul compression and precoding for both CAP and CBP are proposed, which are based on a stochastic successive upper bound minimization (SSUM) approach. Numerical results yield insights into the optimal RU-CU functional split for C-RANs. As a general conclusion, the relative advantages of the two functional splits depend on the interplay between the enhanced interference management abilities of CAP, particularly for dense networks, and the lower fronthaul requirements of CBP in terms of precoding information overhead, particularly for large coherence periods and with stochastic, rather than instantaneous, CSI.</P>

Layered Downlink Precoding for C-RAN Systems With Full Dimensional MIMO

Kang, Jinkyu,Simeone, Osvaldo,Kang, Joonhyuk,Shamai, Shlomo IEEE 2017 IEEE Transactions on Vehicular Technology VT Vol.66 No.3

<P>The implementation of a cloud radio access network (C-RAN) with full dimensional (FD) multiple-input multiple-output (MIMO) is faced with the challenge of controlling the fronthaul overhead for the transmission of baseband signals as the number of horizontal and vertical antennas grows larger. This paper proposes to leverage the special low-rank structure of the FD-MIMO channel, which is characterized by a time-invariant elevation component and a time-varying azimuth component, by means of a layered precoding approach, to reduce the fronthaul overhead. According to this scheme, separate precoding matrices are applied for the azimuth and elevation channel components, with different rates of adaptation to the channel variations and correspondingly different impacts on the fronthaul capacity. Moreover, we consider two different central unit (CU)-radio unit (RU) functional splits at the physical layer, namely, the conventional C-RAN implementation and an alternative one in which coding and precoding are performed at the RUs. Via numerical results, it is shown that the layered schemes significantly outperform conventional nonlayered schemes, particularly in the regime of low fronthaul capacity and a large number of vertical antennas.</P>

북한산국립공원 내 초미세먼지 농도 및 화학적 특성

강석원(Seokwon Kang),강태원(Taewon Kang),박태현(Taehyun Park),박규태(Gyutae Park),이준홍(Junhong Lee),홍제우(Je-Woo Hong),홍진규(Jinkyu Hong),이재홍(Jaehong Lee),이태형(Taehyoung Lee) 한국대기환경학회 2018 한국대기환경학회지 Vol.34 No.3

Preempt a Job or Not in EDF Scheduling of Uniprocessor Systems

Jinkyu Lee,Shin, Kang G. IEEE 2014 IEEE Transactions on Computers Vol.63 No.5

<P>The earliest-deadline-first (EDF) policy has been widely studied for the scheduling of real-time jobs for its effectiveness and simplicity. However, since each preemption incurs an additional delay to the execution of jobs, the effectiveness of EDF is affected greatly by the underlying preemption policy that determines if and when a higher-priority job is allowed to preempt a currently executing lower-priority job. To address this problem, we propose a new and better (in meeting job deadlines) preemption policy of EDF, given a non-zero preemption delay. Specifically, we propose a controlled preemption (CP) policy that controls the condition of preempting jobs, whereas existing approaches focus on that of preempted jobs. We define cp-EDF in which the CP policy is applied to EDF, and analyze its schedulability. This schedulability analysis is then utilized to develop an algorithm that assigns the optimal control parameters of cp-EDF. Our in-depth evaluation has demonstrated that cp-EDF with the optimal parameter assignment improves EDF schedulability over existing preemption policies by up to 7.4%.</P>

A Single Channel Speech Enhancement for Automatic Speech Recognition

Jinkyu Lee,Hyunson Seo,Hong-Goo Kang 한국방송·미디어공학회 2011 한국방송공학회 학술발표대회 논문집 Vol.2011 No.7

This paper describes a single channel speech enhancement as the pre-processor of automatic speech recognition system. The improvements are based on using optimally modified log-spectra (OM-LSA) gain function with a non-causal a priori signal-to-noise ratio (SNR) estimation. Experimental results show that the proposed method gives better perceptual evaluation of speech quality score (PESQ) and lower log-spectral distance, and also better word accuracy. In the enhancement system, parameters was turned for automatic speech recognition.

Composition of Schedulability Analyses for Real-Time Multiprocessor Systems

Jinkyu Lee,Shin, Kang G.,Shin, Insik,Easwaran, Arvind IEEE 2015 IEEE Transactions on Computers Vol.64 No.4

<P>With increasing popularity and deployment of multi-core chips in embedded systems, a number of real-time multiprocessor scheduling algorithms have been proposed along with their schedulability analyses (or tests), which verify temporal correctness under a specific algorithm. Each of these algorithms often comes with several different schedulability tests, especially when it is difficult to find exact schedulability tests for the algorithm. Such tests usually find different task sets deemed schedulable even under the same scheduling algorithm. While these different tests have been compared with each other in terms of schedulability performance, little has been done on how to combine such different tests to improve the overall schedulability of a given scheduling algorithm beyond a simple union of their individual schedulability. Motivated by this, we propose a composition theory for schedulability tests with two new methods. The first method composes task-level timing guarantees derived from different schedulability tests, and the second one derives system-level schedulability results from a single schedulability test. The unified composition theory with these two methods then utilizes existing schedulability tests effectively so as to cover additional schedulable task sets. The proposed composition theory is shown to be applicable to most existing preemptive/non-preemptive scheduling algorithms. We also present three case-studies, demonstrating how and by how much the theory can improve schedulability by composing existing schedulability tests. Our evaluation results also show that the composition theory makes it possible to cover up to 181.7 percent additional schedulable task sets for preemptive fpEDF, preemptive EDF and non-preemptive EDF scheduling algorithms beyond their existing tests.</P>

Improvement of Real-Time Multi-CoreSchedulability with Forced Non-Preemption

Jinkyu Lee,Shin, Kang G. IEEE 2014 IEEE transactions on parallel and distributed syst Vol.25 No.5

<P>While tasks may be preemptive or non-preemptive (due to their transactional operations), deadline guarantees in multi-core systems have been made only for those task sets in each of which all tasks are preemptive or non-preemptive, not a mixture thereof,i.e., fully preemptive or fully non-preemptive. In this paper, we first develop a schedulability analysis framework that guarantees the timing requirements of a given task set in which a task can be either preemptive or non-preemptive in multi-core systems. We then apply this framework to the prioritization polices of EDF (earliest deadline first) and FP (fixed priority), yielding schedulability tests of mpn-EDF (Mixed Preemptive/Non-preemptive EDF) and mpn-FP, which are generalizations of corresponding fully-preemptive and non-preemptive algorithms, i.e., fp-EDF and np-EDF, and fp-FP and np-FP. In addition to their timing guarantees for any task set that consists of a mixture of preemptive and non-preemptive tasks, the tests outperform the existing schedulability tests of np-EDF andnp-FP (i.e., special cases of mpn-EDF and mpn-FP). Using these tests, we also improve schedulability by developing an algorithm that optimally disallows preemption of a preemptive task under a certain assumption. We demonstrate via simulation that the algorithm finds up to 47.6 percent additional task sets that are schedulable with mpn-FP (likewise mpn-EDF), but not with fp-FP and np-FP (likewisefp-EDF and np-EDF).</P>

TOXICITIY COMPARISON OF SWCNT BY CONDUCTANCE IN MICE

Kang Minsung,Roh Jinkyu,Kim Younghun,Kim Soo-Nam,Han Young-Ah,Lee Byeong-Chan,Seo Heung-Sik,Kim Jae-hwan,Kwangsik Park,Kyunghee Choi,Heo Jeong-Doo,Song Chang-Woo,Park Eun-Jung 한국환경독성학회 2009 한국독성학회 심포지움 및 학술발표회 Vol.2009 No.11

Co-simulation을 이용한 스프라켓 고주파 유도경화 깊이분석에 대한 연구

최진규(Jinkyu Choi),탁승민(Seungmin Tak),백인석(Inseok Pack),강한빈(Hanbin Kang),이인영(Inyoung Lee),염상훈,이석순(Seoksoon Lee) 항공우주시스템공학회 2017 항공우주시스템공학회 학술대회 발표집 Vol.2017 No.4