• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.21-24
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• 2001

For very large multimedia traffic to be supported successfully in wireless network environment, it is necessary to provide Quality-of-Service(QoS) guarantees between mobile hosts(clients). In order to guarantee the Qos, we have to keep the call blocking probability below target value during handoff session. However, the QoS negotiated between the client and the network may not be guaranteed due to lack of available channels for traffic in the new cell, since mobile clients should be able to continue their on-going sessions. In this paper we propose a efficient load-balancing algorithm based on the adaptive bandwidth reservation scheme for enlarging available channels in a cell. We design a new method to predict the mobility of clients using MPT(mobility profile table). This method is then used to reserve a part of bandwidths for handoff calls to its adjacent cells and this reserved bandwidth can be used for handoff call prior to new connection requests. If the number of free channels is also under a low threshold value, our scheme use a load-balancing algorithm with a adaptive bandwidth reservation. In order to evaluate the performance of our algorithm, we measure the metrics such as the blocking probability of new calls and dropping probability of handoff calls, and compare with other existing schemes.

• The KIPS Transactions:PartC
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• v.8C no.4
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• pp.421-428
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• 2001

위성통신 시스템은 기존의 지상망이나 광 케이블 기술에 비해 통신 대역폭의 유연성과 다중 접속 능력, 이동 통신, 광역성, 멀티포인트 및 브로드캐스팅 등의 고유의 특징으로 인해 초 고속 정보 통신망 구축에 중요한 역할을 할 것이다. 또한 위성통신은 앞으로 도래할 브로드 캐스팅 및 멀티미디어 서비스 등의 통신환경을 지원하며, 지상중계망의 장애 및 트래픽 폭 주시에 대체경로를 제공함으로써 지상망 중심으로 진화·발전되어 온 B-ISDN망과 상호 보 완적인 보완망으로서의 역할을 수행할 것이다. 따라서 지상 B-ISDN과 위성망의 통합은 지 상망의 효율성고 안정성을 향상시킬 수 있을 뿐만 아니라 국가의 모든 통신망을 하나의 정 보 통신망으로 구성하여 국가의 정보를 효율적으로 이용, 관리 및 운용할 수 있기 때문에 위성망과 B-ISDN간의 연동에 대한 연구는 필수적이다. 본 논문에서는 OBP(On-Board Processing) 탑재 위성 B-ISDN 중계망의 호 처리 절차 연구를 수행하는 것으로서, 위성 B-ISDN 구조와 각 지구국별 신호 기능 및 B-ISDN 신호 시스템인 DSS2(Digital Subscriber Signalling No.2) 계층 3 신호 프로토콜, B-ISUP(B-ISDN User Part) 프로토콜, S-BISUP(Satellite BISUP) 프로토콜의 구조를 분석하였다. 또한 점-대-다지점 연결을 위한 B-ISDN의 연결과 소유권 및 각각의 프로토콜에 대한 메시지와 프리미티브를 정의하여, 이 를 토대로 OBP 탑재 위성 B-ISDN 중계망 연동을 위한 기본 호 처리 절차를 설계 및 검증 하고, 이를 구현하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.925-933
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• 2003

Network is expected to be developed into optical Internet network collected IP layer and optical layer, but GMPLS is risen at the transitional evolution stage because of the present technology level. GMPLS that MPLS is extended and generalized is able to support not only the packet switching device but also the devices which perform switching in time, wavelength, and space domain. To implement the common control plane to these various switching types, GMPLS extends the existing MPLS signaling and routing protocol. In this paper, we describe the overview of GMPLS technology, and then we will refer to the OSPF(Open Shortest Path First), which was used to exchange the status information of link, as the plan of routing extension to exchange the information of various link type, bandwidth, link protection type etc. And also, we describe the definition of new protocol, so called, LMP that is a signaling protocol for solving complex problem which manages hundreds and thousands of links between two nodes. And we will examine and analyze the plan of signaling protocol extension to apply signaling protocol RSVP-TE(Resource Reservation Protocol) for traffic engineering in MPLS to network, and the message objects and formats associated with modified RSVP.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1139-1142
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• 2006

Mobile Ad-hoc 네트워크(MANET)에서 각 노드들은 한정된 배터리에 의존하여 통신한다. 이와 같은 제한사항을 극복하기 위해 링크의 안정성을 유지하거나 파워 소모를 고려한 프로토콜에 대한 연구들이 활발히 이루어져 왔다. 하지만 링크의 안정성 또는 파워 소모의 어느 한 측면만을 고려함으로써 링크의 안정성은 높일 수 있으나 파워 소모가 효율적이지 못했다. 반면에 전체 파워소모는 줄일 수 있었으나 파워소모의 균형을 이루지 못함으로써 네트워크 수명을 오래 지속시킬 수 없는 문제점이 발생 했다. 본 논문에서는 배터리 잔량에 대한 threshold를 적용함과 동시에 신호세기를 고려하여 각 노드들의 균형된 파워소모와 네트워크 전체의 파워 소모를 최소화함으로써 네트워크 수명을 오래 지속시키기 위한 프로토콜인 PRTRS(Power Aware Routing Protocol based on Both Threshold by Residual Battery Capacity and Signal Strength in Mobile Ad-hoc Network)를 제안한다. PRTRS는 AODV(Ad-hoc On-demand Distance Vector Routing)를 기반으로 하였다. NS-2 네트워크 시뮬레이션 결과 PRTRS는 특정 노드로 집중되는 트래픽을 분산시켜 파워소모의 균형을 이루고 네트워크 전체의 파워소모를 최소화함으로써 네트워크 수명이 연장됨을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1117-1124
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• 2013

As the recently soaring wireless traffic, small-cell techniques have been actively studied in order to support such a wireless demand for cellular wireless networks. This paper focuses on the inter-cell interference neutralization to resolve the main barrier for implementing small-cell cellular networks. Assuming that each message is delivered to the final destination by the help of base stations or relays, ergodic interference neutralization is proposed, which exploits the time-varying nature of wireless channels. The previous approach based on amplify-and-forward (AF) suffers from severe performance degradation in the low signal-to-noise (SNR) regime due to noise amplification. On the other hand, the proposed interference neutralization based on recently developed compute-and-forward (CF) fixes such a problem and improves the performance in the low SNR regime.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.1
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• pp.21-26
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• 2002

Video stream invoke a variety of traffic with the structure of compression algorithm and image complexity. Thus, it is difficult to allocate the resource on the both sides of sender and receiver, and playout on the Internet such as a packet switched network. Thus, in this paper we proposed video stream smoothing using multistream for the effective transmission of video stream. This method specifies the type of LDU(logical data unit) according to the type of original stream, and then makes a large number of streams as a fixed size, and transfers them. So, the proposed method can reduce the buffering time which occurs during the process of the smoothing and prefetch be robust to the jitter on network, as well. Consequently, it has the effective transmission characteristics of fully utilizing the clients bandwidth.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.870-872
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• 2020

본 시스템은 어린이보호구역에 발생하는 차량사고가 불법주정차된 차량으로 인한 사각지대에 의해 발생되는 것에 착안하여 보행자를 인식하여 운전자들에게 알려 안전운전을 유도하여 사고를 예방해 주는 시스템이다 본 시스템은 영상인식장치, 경광장치, 중계장치, 차량 내 경고장치, 원격 트래픽 경고 수신기로 구성되어 있으며 영상인식장치가 edge-TPU 장치를 활용하여 카메라로부터 입력받은 영상을 모바일넷 기반의 딥러닝으로 처리하여 보행자, 차량, 그밖의 물체를 인식한다. 보행자가 인식되면 외부에서 경광장치가 발광하여 신호를 보내고, 중계장치를 통해 차량 내 경고장치로 보행자 경고 신호를 보낸다. 실험 결과 영상인식을 통해 보행자와 차량을 분류 인식할 수 있음을 확인하였다. 이러한 시스템은 어린이 보호구역에서 발생할 수 있는 교통사고를 방지하기 위해 효과적임을 확인할 수 있었다.

• The Journal of Information Technology
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• v.4 no.3
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• pp.87-100
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• 2001

IETF has proposed integrated services model(Int-Serv) and differentiated service(Diff-Serv) to supply IP QoS in Internet[1][2]. Int-Serv model uses state information of each IP flow, so satisfies QoS according to traffic characteristics, but increases the amount of flow state information with increasing flow number. Diff-Serv uses PHP(Per Hop Behaviour) and there are well-defined classes to provide differentiated traffics with different services according to delay and loss sensitivity. Diff-Serv model can provide diverse services in Internet because of having no the state and signal information of each flow. As MPLS uses the packet forwarding technology based on label, it implements the forwarding engine of high performance easily. The MPLS can set up the path having different and variable bandwidth and assign each path to particular CoS (Class of Service). Therefore it is possible to support the Diff-Serv model of well- defined classes that can provide the differentiated traffic with different services according to delay and loss sensitivity in IP QoS models of IETF. In this paper we propose a scheme that can accommodate Diff-Serv model to provide QoS. The system performance has been estimated by scheduling plan according to traffic classes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.29-36
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• 2012

In Wireless Sensor Network(WSN)s, the detection of precise location of each node is essential for utilizing sensing data acquired from sensor nodes effectively. Among various location methods, the received signal strength(RSS) based localization scheme is mostly preferable in many applications because it can be easily implemented without any additional hardware cost. Since a RSS-based localization scheme is mainly affected by radio channel or obstacles such as building and mountain between two nodes, the localization error can be inevitable. To enhance the accuracy of localization in RSS-based localization scheme, a number of RSS measurements are needed, which results in the energy consumption. In this paper, a RSS based localization using Bayesian Compressive Sensing(BSS) with path-loss exponent estimation is proposed to improve the accuracy of localization in the energy-efficient way. In the propose scheme, we can increase the adaptative, reliability and accuracy of localization by estimating the path-loss exponents between nodes, and further we can enhance the energy efficiency by the compressive sensing. Through the simulation, it is shown that the proposed scheme can enhance the location accuracy of multiple unknown nodes with fewer RSS measurements and is robust against the channel variation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1549-1556
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• 2016

By increased moving speed of aircraft, estimating location of itself becomes more important than ever. This requirement is satisfied by appearance of GPS, however it is useless when signal reception from satellite is not good enough by interruption, for example, traffic jamming. Applying link for communication to additional positioning system is capable of providing relative position of aircraft. Estimating location with link for communication is done without additional equipment but with signal processing based on correlation of received signal. ESPRIT is one of the representative algorithm among them. Estimating correlation matrix is possible to have error since it includes average operation needs enough number of samples not impractical. Therefore we propose algorithm that defines, estimates and removes error matrix of correlation. Proposing algorithm shows better performance than previous one when transmitters are close.