• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.965-973
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• 2007

We analyzed that the loss of data in TCP protocol based wireless networks caused by overlapped responses in bi-directional nodes that were resulted in out of the data sequence. This loss can be prevented by using revised TCP rate control algorithm and the performance of throughput can also be improved. The rate control algorithm is applied when the congestion happens between nodes while traffic packets are retransmitting in TCP bandwidth. In addition to applying the rate control algorithm, we determine the number of system clients in bandwidth and the average of pausing time between transmitting serial files to produce a competitive level so that an efficient performance of rapid retransmitting for the loss of multi-packets. This paper discusses the improvement of congestion control in that the decrease of the loss, firstly, as ensuring an efficient connection rate and, secondly, as using sliding window flow control.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.1
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• pp.29-37
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• 2020

Work to improve network throughput has been focused on network coding as the utilization of IoT-based application services increases and network usage increases rapidly. In network coding, nodes transform packets received from neighboring nodes into a combination of encoded packets for transmission and decoding at the destination. This scheme is based on trust among nodes, but in the IoT environment where nodes are free to join, a malicious node can fabricate the packet if it legally participates in the configuration. It is difficult to identify the authenticity of the encoded packet since the packet received at destination is not a single source but a combination of packets generated by several nodes. In this paper, we propose a method to detect "look-like-valid" packets that have been attacked and disguised in packets received at destination, and to identify valid messages in the reconstructions. This method shows that network coding performance is significantly improved because the destination can reconstruct a valid message with only received packets without retransmission with a high probability, despite the presence of disguised packets.

• Journal of KIISE:Information Networking
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• v.34 no.2
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• pp.120-133
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• 2007

A multicast tree includes several, possibly a large number of, paths connecting source-receiver pairs, and network failure may disable part of the multicast tree. Reconstruction of the entire multicast tree to recover from a component failure is highly undesirable, because some group members have to suffer service disruptions even though the communication paths to/from them are not affected by the failure. To limit reconfiguration region and to maximize the likelihood of successful reconfiguration, we propose and evaluate a pre-planned reconfiguration policy for QoS multicast sessions. Specifically, we equip a reconfiguration path (RP) with each end-to-end path that connects a source-receiver pair in the multicast tree, and reserve resources in advance along the RPs. Efficient resource-sharing techniques are applied to reduce the amount of resources reserved for RPs but not used in the absence of failures. This way, we prevent uncontrolled competition among different multicast sessions which may simultaneously try to recover from failures. We evaluate the performance of the proposed scheme using simulation on randomly-generated networks. We use the shortest-path routing for QoS multicast sessions, and simulate both source-based and shared multicast trees. The evaluation results indicates that successful pre-planned reconfiguration can be achieved for all group members with reasonable overhead. Our scheme is also shown to adapt well to dynamic changes of group membership.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.813-818
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• 2020

Recently, with the rapid increase in technology and users of smart devices, the smart watch market has grown, and its utility and usability are continuously expanding. The strengths of smartwatches are wearable portability, application immediacy, data diversity and real-time capability. Despite these strengths, smartwatches have limitations such as battery limitations, display and user interface size limitations, and memory limitations. In addition, there is a need to supplement developers and standard devices, operating system standard models, and killer application modules. In particular, monitoring and application of user's biometric information is becoming a major service for smart watches. The biometric information of such a smart watch generates a large amount of data in real time. In order to advance the biometric information service, stable peer-to-peer transmission of sensing data to a remote smartphone or local server storage must be performed. We propose a synchronization method to ensure wireless remote peer-to-peer transmission stability in a smart watch system. We design a wireless peer-to-peer transmission process based on this synchronization method, analyze asynchronous transmission process and proposed synchronous transmission process, and propose a transmission efficiency method according to an increase in transmission amount.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.6
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• pp.612-622
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• 2002

In this paper, we review temporal error concealment for video transport over unreliable networks, and a new approach for the recovery of lost or erroneous motion vection(MV)s by classifying the movements of neighboring blocks by their homogeneity is proposed. MVs of the neighboring blocks are classified according to the direction of MVs and a representative value for each class is determined to obtain the candidate MV set. By computing the distortion of the candidates, a MV with the minimum distortion is selected. Experimental results show that the proposed algorithm exhibits better performance in many cases than existing methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.1
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• pp.76-87
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• 2005

In this paper, we propose a new profile, ROHC(RObust Header Compression) profile 7, for SCTP with ROHC for applying robust header compression SCTP, which is a transport layer protocol. The proposed new profile 7 adds a new field of 1 or 2 byte size on the existing SCTP packet header, which can make the SCTP stream to be diveded into acknowledgement stream and data stream. In addition, the classification of the stream can be used for recovering fault context. Consequently, in the case of using proposed ROHC-SCTP, it is possible to reduce the SCTP header overhead rate and also can be saved bandwidth.

• The Journal of the Korea Contents Association
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• v.8 no.3
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• pp.47-54
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• 2008

In order to realize Intelligent Transport System (ITS) without any road facilities support, Inter-vehicle Communication (IVC) is increased attention. IVC makes it possible to exchange real-time information among vehicles without centralized infrastructure. The IVC systems use multi-hop broadcast to disseminate information. In this paper, we propose the improved AODV routing protocol based on location information. The proposed AODV routing protocol transmits Hello packet with location information to calculate the distance between nodes. Then it achieves fast link recovery. We confirm the throughput performance of the proposed AODV routing protocol compared with the AODV routing protocol using Qualnet ver.3.8 simulator.

• Journal of KIISE:Information Networking
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• v.28 no.1
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• pp.143-153
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• 2001

본 논문에서는 에드-혹 망의 멀티캐스트 라우팅 프로토콜인 ODMRP(On-Demand Multicast Routing Protocol)를 확장한 PatchODMRP를 제안한다. ODMRP는 네트워크 상에서 멀티캐스트그룹의 송신원으로부터 수신원에 이르는 경로 상에 있는 노드들을 FG(Forwarding Group) 노드로 선출하여 이들이 해당 멀티캐스트그룹에 속하는 패킷을 모두 플러딩하도록 함으로써 멀티캐스트 그룹데이타 전송을 담당하는 메쉬를 구성하도록 하는 방안이다. 그런데 ODMRP는 주기적으로 이 메쉬를 구성하는 FG 노드들을 재 선정하기 때문에 이 주기가 길어지면 메쉬 구성이 네트워크 노드들의 이동성을 따라가지 못해 메쉬분리가 발생하고 데이터가 손실될수 있다. 반면에 이 주기를 짧게 하면 오버헤드가 지나치게 커질수 있다. 특히 송신원의 수가 적은 경우 ODMRP의 메쉬는 매우 성기게 형성되는데 이때 호스트들의 이동성이 크면 메쉬 연결을 유지하기 위하여 이 주기를 짧게 잡아주거나 높은 데이터 손실율을 감수해야한다. 본 논문에서는 이 문제점을 해결하고자 각 FG 노드들이 BEACON 신호를 이용해 자신에 인접한 메쉬에 손실이 발생한 것을 인지하고 이를 국부적인 플러딩을 통하여 빠르게 복구하는 메커니즘을 ODMRP에 추가한 PatchODMRP 방식을 제안한다. 시뮬레이션을 통하여 기존의 ODMRP와 제안하는 PatchODMRP의 성능을 비교한 결과 PatchODMRP가 호스트의 이동성에 훨씬 강하며 ODMRP에 비하여 낮은 오버헤드로 높은 데이터 전송률을 제공할 수 있음을 보여주었다.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.784-789
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• 2007

유비쿼터스 환경에 존재하는 스마트 객체들 사이의 협력으로 지능적인 서비스를 제공하는 시스템을 구축하기 위한 새로운 패러다임으로 커뮤니티 컴퓨팅이 제안되어, 활발히 연구되고 있다. 커뮤니티는 해결해야 할 목표를 가지며 목표 달성을 위해 필요한 멤버들을 구성하고, 멤버들은 목표 달성을 위해 상호작용한다. 이러한 상황에서 멤버의 결함은 멤버 사이의 상호작용을 중단시키는데, 원활한 멤버 사이의 상호작용이 커뮤니티의 목표를 달성하는 가장 중요한 문제이므로, 결국 멤버의 결함은 커뮤니티의 목표 달성의 실패를 가져온다. 이 문제를 해결하기 위해, 본 논문에서는 컨텍스트 온톨로지를 이용한 멤버의 복제 방법 및 복구 알고리즘을 제안한다. 각 멤버는 자신의 상태를 커뮤니티에 전송하며, 커뮤니티는 모든 멤버의 상태를 온톨로지로서 유지한다. 멤버의 결함이 발견되면, 커뮤니티는 결함이 발생한 멤버의 상태 온톨로지를 추론하여 이 멤버를 대신할 새로운 멤버를 커뮤니티로 끌어들인다. 커뮤니티에 들어온 새로운 멤버는 다른 멤버들과 즉시 상호작용을 할 수 없기 때문에, 커뮤니티로부터 결함이 발생한 멤버의 온톨로지를 전송 받아 추론하여 자신의 상태를 결함이 발생한 멤버의 상태로 전환시킨다. 이 과정이 끝나면, 새로운 멤버는 자연스럽게 다른 멤버들과 상호작용을 할 수 있으며, 커뮤니티는 목표 달성을 위해 계속적으로 나아간다. 본 논문에서는 이 알고리즘의 빠르고 효율적인 수행을 위해 OWL(Web Ontology Language)로 기술된 컨텍스트 온톨로지를 사용하였으면, Jade 에이전트 플랫폼을 이용하여 제안한 방법을 실험, 분석 하였다.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.3
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• pp.1-9
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• 2006

The handoff in IEEE 802.11 WLAN is a hard handoff. In hard handoff, a station has to stop the communication. As a result, the station is likely to miss some packets that arrival during the handoff process. To recover these lost packets, buffer-and-forward scheme is used. But, buffer-and-forward scheme is not efficient for real time service. In this paper, we propose new handoff scheme for real time service in home network based WLAN. The scheme uses priority queue which is recommended in IEEE 802.lie, and priority of priority queue is given to real time handoff calls. The simulation results show that the proposed scheme reduces traffic loss and transmission sequence error.