A Hybrid Upstream Bandwidth Allocation Method for Multimedia Communications in EPONs

Baek, Jinsuk,Kwak, Min Gyung,Fisher, Paul S. The Institute of Electronics and Information Engin 2012 IEIE Transactions on Smart Processing & Computing Vol.1 No.1

The Ethernet Passive Optical Network (EPON) has been considered to be one of the most promising solutions for the implementation of the Fiber To The Home (FTTH) technology designed to ameliorate the "last mile" bandwidth bottleneck. In the EPON network, an efficient and fair bandwidth allocation is a very important issue, since multiple optical network units (ONUs) share a common upstream channel for packet transmission. To increase bandwidth utilization, an EPON system must provide a way to adaptively allocate the upstream bandwidth among multiple ONUs in accordance to their bandwidth demands and requirements. We present a new hybrid method that satisfies these requirements. The advantage of our method comes from the consideration of application-specific bandwidth allocation and the minimization of the idle bandwidth. Our simulation results show that our proposed method outperforms existing dynamic bandwidth allocation methods in terms of bandwidth utilization.

Packet Loss Patterns Adaptive Feedback Scheduling for Reliable Multicast

Jinsuk Baek,Cheonshik Kim,You-Sik Hong 대한전자공학회 2007 JUCT : Journal of Ubiquitous Convergence Technolog Vol.1 No.1

Tree-based reliable multicast protocols provide scalability by distributing error-recovery tasks among several repair nodes. These repair nodes perform local error recovery for their receiver nodes using the data stored in their buffers. We propose a packet loss patterns adaptive feedback scheduling scheme to manage these buffers in an efficient manner. Under our scheme, receiver nodes send NAKs to repair nodes to request packet re-transmissions only when the packet losses are independent events from other nodes. At dynamic and infrequent intervals, they also send ACKs to indicate which packets can be safely discarded from the repair node's buffer. Our scheme reduces delay in error recovery because the requested packets are almost always available in the repair node’s buffers. It also reduces the repair node’s workload because (a) each receiver node sends infrequent ACKs with non-fixed intervals and (b) their sending times are fairly distributed among all the receiver nodes.

A Scalable Recovery Tree Construction Scheme Considering Spatial Locality of Packet Loss

( Jinsuk Baek ),( Jehan-francois Paris ) 한국인터넷정보학회 2008 KSII Transactions on Internet and Information Syst Vol.2 No.2

Packet losses tend to occur during short error bursts separated by long periods of relatively error-free transmission. There is also a significant spatial correlation in loss among the receiver nodes in a multicast session. To recover packet transmission errors at the transport layer, tree-based protocols construct a logical tree for error recovery before data transmission is started. The current tree construction scheme does not scale well because it overloads the sender node. We propose a scalable recovery tree construction scheme considering these properties. Unlike the existing tree construction schemes, our scheme distributes some tasks normally handled by the sender node to specific nodes acting as repair node distributors. It also allows receiver nodes to adaptively re-select their repair node when they experience unacceptable error recovery delay. Simulation results show that our scheme constructs the logical tree with reduced message and time overhead. Our analysis also indicates that it provides fast error recovery, since it can reduce the number of additional retransmissions from its upstream repair nodes or sender node.

A Heuristic Buffer Management and Retransmission Control Scheme for Tree-Based Reliable Multicast

Jinsuk Baek,Jehan Francois Paris 한국전자통신연구원 2005 ETRI Journal Vol.27 No.1

We propose a heuristic buffer management scheme that uses both positive and negative acknowledgments to provide scalability and reliability. Under our scheme, most receiver nodes only send negative acknowledgments to their repair nodes to request packet retransmissions while some representative nodes also send positive acknowledgments to indicate which packets can be discarded from the repair node’s buffer. Our scheme provides scalability because it significantly reduces the number of feedbacks sent by the receiver nodes. In addition, it provides fast recovery of transmission errors since the packets requested from the receiver nodes are almost always available in their buffers. Our scheme also reduces the number of additional retransmissions from the original sender node or upstream repair nodes. These features satisfy the original goal of treebased protocols since most packet retransmissions are performed within a local group.

FI-Based Local Group Key Generation/Distribution for Mobile Multicast in a Hierarchical Mobile IPv6 Network

( Jinsuk Baek ),( Paul S. Fisher ),( Mingyung Kwak ) 한국인터넷정보학회 2008 KSII Transactions on Internet and Information Syst Vol.2 No.1

In order to securely transmit multicast data packets in a mobile environment where frequent join/leave events are a characteristic of the environment, there is a need for a new secure and efficient group key management solution. We propose a secure group key generation/distribution solution providing scalability and reliability. Using this solution, when a mobile node, which is in a multicast session, enters a new domain, the agent of the domain joins the multicast session and coordinates its data packets with the mobile node. The agent encrypts and transmits subsequent data packets to the mobile node, using a local one-time pad key. This key is generated with FI sequences, enabling the mobile node to regenerate the same data packet, based on the information sent by the agent. Our performance analysis demonstrates that the proposed solution can significantly reduce the number of key generations and distributions, when it is applied to the hierarchical mobile IPv6 network.

A New Hybrid Architecture for Cooperative Web Caching

Jinsuk Baek,Gurpreet Kaur,Junghoon Yang 대한전자공학회 2008 JUCT : Journal of Ubiquitous Convergence Technolog Vol.2 No.1

An effective solution to the problems caused by the explosive growth of World Wide Web is a web caching that employing an additional server, called proxy cache, between the clients and main server for caching the popular web objects near the clients. However, a single proxy cache can easily become the bottleneck. Deploying groups of cooperative caches provides scalability and robustness by eliminating the limitations caused by a single proxy cache. Two common architectures to implement the cooperative caching are hierarchical and distributed caching systems. Unfortunately, both architectures suffer from performance limitations. We propose an efficient hybrid caching architecture eliminating these limitations by using both the hierarchical and same level caches. Our performance evaluation with our investigated simulator shows that the proposed architecture offers the best of both existing architectures in terms of cache hit rate, the number of query messages from clients, and response time.

A Smart Backoff Scheme for Multicast Flows in Wireless LAN

Jinsuk Baek,Min Gyung Kwak,Paul S. Fisher 한국산학기술학회 2015 SmartCR Vol.5 No.3

In IEEE 802.11 wireless protocols, a multicast sender basically adopts a simple broadcasting mechanism to transmit multicast frames. As such, the multicast frames are locally transmitted at a low, fixed rate without any backoff process on the sender’s side or any feedback requirements on the receiver side. This simplicity reveals an unfairly shared channel access between unreliable multicast flows and reliable unicast flows. In this paper, we propose a novel backoff scheme for multicast frame retransmission. The proposed scheme has been strategically designed after considering the sources of multicast frame errors. We define two different types of NAK messages that include a NAK for a single frame error and a cumulative NAK for multiple continuous erroneous frames. For frame retransmission, the multicast sender is required to adaptively adjust its contention window size based on the NAKs sent by its local receiver. With the proposed scheme, we ultimately provide reliable local multicast transmission and a relatively fair channel sharing with low-priority unicast flows.

An Adaptive Primary Path Switching Scheme for Seamless mSCTP Handover

Jinsuk Baek,Doowon Kim,Paul S. Fisher,Minho Jo 한국산학기술학회 2011 SmartCR Vol.1 No.2

In this paper, a primary path switching scheme is proposed to provide a seamless handover for dual-homed mobile terminals. This scheme is proposed as an enhancement to the mSCTP protocol. With this scheme, a mobile terminal performs primary path switching before it becomes unavailable due to its primary path drop. The improvement achieved by the scheme is that it considers the temporal velocity of the mobile terminal with relative RTT variances of all available paths when it performs the handover process in the overlapped area between two different networks. Our simulation results show that the proposed scheme achieves a better overall performance than other schemes, and anticipatory switching is more important for faster moving terminals.

Improved Robustness of Reinforcement Learning Based on Uncertainty and Disturbance Estimator

Jinsuk Choi,Hyunbeen Park,Jongchan Baek,Soohee Han 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11

This paper proposes a method to improve the robustness of RLs based on model-free uncertainty and disturbance estimator (RL-based UDE). In the real environment, instead of using optimal trajectory and control techniques to perform complex tasks, it learns through RL and supplements robustness by using uncertainty and disturbance estimator (UDE). From UDE, the robotics system can be improved the stability by appropriately canceling the uncertainty and disturbance without efforts to obtain model information; hence the UDE can compensate for the performance degradation of RL when system is non-stationary. In addition, the performance can be improved by reducing the sensor noise from low-pass filter of UDE. It is shown through an experiment that the proposed RL-based UDE provides robustness.

유치원 만 5세 유아와 초등학교 1학년 아동의 이동기하능력과 공간능력 간의 관계에 대한 연구

백승선(Baek, SeungSeon),최진숙(Choi, JinSuk) 학습자중심교과교육학회 2019 학습자중심교과교육연구 Vol.19 No.5

본 연구는 유치원 만 5세 유아와 초등학교 1학년 아동의 연령에 따른 이동기하능 력과 공간능력의 발달 차이를 알아보고 이동기하능력과 공간능력 간의 관계를 밝히 는데 그 목적이 있다. 이를 위해 전라북도에 소재한 유치원 만 5세반과 초등학교 1학 년에 다니는 아동 62명씩 총 124명을 선정하여 2018년 4월 9일부터 5월 31일까지 최연, 이정욱(2006)이 고안한 이동기하능력 검사도구와 홍혜경(2001)이 개발한 공간능력 검사도구를 사용하여 검사를 진행하였다. 수집된 자료는 t검증과 Pearson의 상관 분석을 통해 검증하였다. 본 연구결과 유치원 만 5세 유아와 초등학교 1학년 아동의 이동기하능력과 공간능력은 연령이 높아질수록 발달하게 되며, 이동기하능력과 공간능력 간의 정적인 상관이 있는 것으로 나타났다. The objective of this study was to examine the difference of age-based development of motion geometry ability and spatial ability in 5-year-old kindergarten students and elementary school first-year students, and then look into the relationship between the two abilities. For this, 62 5-year-old kindergarten students and another 62 elementary school first-year students were sampled from kindergartens and elementary schools in Jeollabuk-do. In order to test collected data, this study used both the motion geometry ability test developed by Choe Yeon and Lee Jeong-Uk (2006) and the spatial ability test for young children developed by Hong Hye-Gyeong (2001). Study findings are as follows: Motion geometry ability and spatial ability in 5-year-old kindergarten students and elementary school first-year students increased gradually as they grew older. In addition, there was a positive relationship between motion geometry ability and spatial ability. Study findings seem to suggest that it is necessary to carry out a linked education of geometry learning for 5-year-old kindergarten students and elementary school first-year students. And since motion geometry activities for young children can develop their spatial ability, early childhood mathematical education must include motion geometry activities.