• Convergence Security Journal
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• v.12 no.1
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• pp.35-42
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• 2012

Increase of data traffic and the advent of new real-time services require to change from the traditional TDM-based (Time Division Multiplexing) networks to the optical networks that soft and dynamic configuration. Voice and lease line services are main service area of the traditional TDM-based networks. This optical network became main infrastructure that offer many channel that can convey data, video, and voice. To provide high resilience against failures, Packet-optical networks must have an ability to maintain an acceptable level of service during network failures. Fast and resource optimized lightpath restoration strategies are urgent requirements for the near future Packet-optical networks with a Generalized Multi-Protocol Label Switching(GMPLS) control plane. The goal of this paper is to provide packet-optical network with a hierarchical multi-layer recovery in order to fast and coordinated restoration in packet-optical network/GMPLS, focusing on new implementation information. The proposed schemes do not need an extension of optical network signaling (routing) protocols for support.

• Journal of KIISE
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• v.44 no.1
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• pp.63-70
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• 2017

This paper considers the problem of combining multiple strategies for solving sleeping bandit problems with stochastic rewards and stochastic availability. It also proposes an algorithm, called sleepComb(${\Phi}$), the idea of which is to select an appropriate strategy for each time step based on ${\epsilon}_t$-probabilistic switching. ${\epsilon}_t$-probabilistic switching is used in a well-known parameter-based heuristic ${\epsilon}_t$-greedy strategy. The algorithm also converges to the "best" strategy properly defined on the sleeping bandit problem. In the experimental results, it is shown that sleepComb(${\Phi}$) has convergence, and it converges to the "best" strategy rapidly compared to other combining algorithms. Also, we can see that it chooses the "best" strategy more frequently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8A
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• pp.760-768
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• 2006

In this paper, an novel resource allocation scheme is proposed for adaptive multiuser OFDM-TDD systems in multiuser, multicell and frequency-selective time-varying channels. The optimal frame size and mode switching level of each user is determined by maximizing the spectrum efficiency. In multi-cell environment, the allocation scheme must consider the cochannel interference of other cells. The measured SINR is changed in one frame size because the interference is changed. The frame size is determined to consider both the optimal frame size and cochannel user's frame size of other cells. we propose the efficient resource allocation scheme which is satisfied the target BER.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.11
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• pp.84-91
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• 2009

A high speed serial link transmitter using multi-level signaling is proposed. To achieve high data rate m high speed serial link, 4-pulse amplitude modulation (PAM) is used. By transmitting 2 bit data in each symbol time, high speed data transmission, two times than binary signaling, is achieved. The transmitter transmits current-mode output instead of voltage-mode output Current-mode output is much faster than voltage-mode output, so higher data transmission is available by increasing switching speed of driver. $2^5-1$ pseudo-random bit sequence (PRBS) generator is contained to perform built-in self test (BIST). The 4-PAM transmitter is designed in Dongbu HiTek $0.18{\mu}m$ CMOS technology and achieves 8 Gb/s, 160 mV of eye height with 1.8 V supply voltage. The transmitter consumes only 98 mW for 8 Gb/s transmission.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.8
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• pp.1099-1106
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• 2018

In this paper, we developed and then analyzed the specifications of the frequency synthesizer which was applied to long range MFR (Multi-function Radar). These specifications were able to guarantee the functions and performance of MFR. MFR was the radar system that used phase array for electronically scanning. This frequency synthesizer made various frequency signals including to STALO (Stable Local Oscillator) for MFR. By analyzing the MFR requirements, we choose the optimal frequency synthesis method and then we got the best performance and functionality including to physical size for this system. We designed and fabricated DDS (Direct Digital Synthesizer)-driven Offset-PLL (Phase Locked Loop) synthesizer to meet the requirements which were low phase noise, fast switching time and low spurious. This synthesizer had less than -131dBc/Hz@100kHz phase noise and less than $4.1{\mu}s$ switching time, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7C
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• pp.677-684
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• 2002

Today's Internet does not have efficient traffic engineering mechanism to support QoS for the explosive increasing internet traffic such as various multimedia traffic. This functional shortage degrades prominently the quality of service, and makes it difficult to provide multi-media service and real-time service. Various technologies are under developed to solve these problems. IETF (Internet Engineering Task Force) developed the MPLS (Multi-Protocol Label Switching) technology that provides a good capabilities of traffic engineering and is independent layer 2 protocol, so MPLS is expected to be used in the Internet backbone network$\^$[1][2]/. The faults occurring in high-speed network such as MPLS, may cause massive data loss and degrade quality of service. So fast network restoration function is essential requirement. Because MPLS is independent to layer 2 protocol, the fault detection and reporting mechanism for restoration should also be independent to layer 2 protocol. In this paper, we present the experimental results of the MPLS OAM function for the performance monitoring and fault detection 'll'&'ll' notification, localization in MPLS network, based on the OPNET network simulator

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.469-477
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• 2003

This paper proposes a Carrier-Rotation (CR) PWM technique that is a new solution for the voltage unbalancing problem of flying capacitors in the Flying Capacitor Multi-level Inverter (FCMI). The proposed technique equalizes the utilization of phase leg voltage redundancies corresponding to the charging and the discharging state of individual flying capacitors during each switching period of all the switches. Therefore, the charging and the discharging quantity of flying capacitors are equal, which makes the average variation of flying capacitor voltages become zero and keeps their voltage stable during minimum specified period. It also has the reduced harmonic contents of output voltage and the same switch utilization since all the carrier signals are in phase and the switching frequency of each switch is identical. The proposed technique is analyzed precisely in flying capacitor 3-level inverter and then it has expanded to the FCMI (N-level, N>3). Experimental results on the laboratory prototype flying capacitor 3-level inverter confirm the validity of the proposed technique.

• ETRI Journal
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• v.38 no.5
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• pp.847-857
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• 2016

Broadcasting services such as multi/single channel HDTV and 3DTV/2DTV use a multi-channel encoder that changes the bitrate and composition of the video service depending on the time. However, this type of multi-channel encoder could cause a longer latency owing to the variable bitrate and relatively bigger size of the buffers, which results in the same delay as in 3DTV even for a conventional DTV service. On the other hand, systems built based on separate encoders, each of which is optimized for the target service, might not have such latency problems. Nevertheless, there might be a distortion problem in the image and sound at the time of a switchover between two encoders with different output bitrates and group of picture structures. This paper proposes a system that can realize a seamless video service conversion using two different video encoders optimized for each video service. An overall functional description of the video service change control server, which is a main control block for the proposed system, is also provided. The experiment results confirm the seamless switchover and reduced broadcasting latency of DTV services compared with a broadcasting system composed of a multi-channel encoder system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4725-4747
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• 2020

Software defined networking (SDN) is considered to be one of the most promising paradigms in the future. To solve the scalability and performance problem that a single and centralized controller suffers from, the distributed multi-controller architecture is adopted, thus forms multi-domain SDN. In a multi-domain SDN network, it is of great importance to ensure a reliable control plane. In this paper, we focus on the reliability problem of multi-domain SDN against controller failure from perspectives of backup controller deployment and controller replication. We firstly propose a placement algorithm for backup controllers, which considers both the reliability and the cost factors. Then a controller replication mechanism based on shared data storage is proposed to solve the inconsistency between the active and standby controllers. We also propose a shared data storage layout method that considers both reliability and performance. Besides, a fault recovery and repair process is designed based on the controller backup and shared data storage mechanism. Simulations show that our approach can recover and repair controller failure. Evaluation results also show that the proposed backup controller placement approach is more effective than other methods.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.285-288
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• 1998

In this paper, we present mSROS(Micro-Scalable Realtime Operating System) to be applied commonly to the device controller systems in the HANbit ACE256 system. The device controller systems in HANbit ACE256 system are organized as many kinds of device controller. Applying modified PPOS(Peripheral Processor Operating System)which is an operating system for devices of the TDX-10 switching system to the firmwares for them, the inefficiency in development and maintenance exists inherently. To remove the inefficiency nd to improve the performqance of firmwares, we build a common operating system platform that including multi-tasking microkernel so that the firmwares among devices can acquire convenient development and cheap cost of maintencance. Especially, building a virtual machine as a development methodology, it is possible to remove dependency from the kernel so that any kinds of commercial real-time kernels can be used in mSROS as a basic kernel. The virtual machine in mSROS is compatible with the API of SROS(Scalable Realtime Operating System), PPOS, and CROS(Concurrent Realtime Operating System).