• Journal of Digital Contents Society
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• v.9 no.4
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• pp.679-686
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• 2008

Wireless LAN(WLAN) is a rather mature communication technology connecting mobile terminals. IEEE 802.11 is a representative protocol among WLAN technologies. With the rising popularity of delay-sensitive real-time multimedia applications(video, voice and data) in IEEE 802.11 wireless LAN, it is important to study the MAC layer delay performance of WLANs. In this paper, performance for packet delay model that recently have been proposed schemes is analysed in wireless LAN and proved performance results via simulation.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.583-585
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• 2012

PMIP (Proxy Mobile IPv6)은 네트워크 기반 이동성 지원 프로토콜로, 호스트 기반 이동성 프로토콜에 비해 핸드오버 시간을 줄였지만 완전히 제거하지 못하였고 핸드오버 시의 패킷 손실에 대해서도 고려하지 않는다. 따라서 핸드오버 시간을 줄이고 패킷 손실을 방지하여 끊김 없는 서비스를 제공하기 위한 빠른 predictive 핸드오버 방식이 제안되었다. 하지만 이 방식을 이용할 경우 predictive 모드에서의 핸드오버 절차를 진행하기 위해 불필요한 핸드오버 지연이 발생할 수 있다. 본 논문에서는 GPS를 이용하여 MN (Mobile Node)의 위치정보를 파악하고 이를 통해 predictive 모드에서의 빠른 핸드오버 절차 진행 시 발생하는 문제점 해결을 위한 기법을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.322-324
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• 2000

인터넷을 통한 실시간 멀티미디어 전송에 있어서 인터넷이 "Best effort" 서비스이기 때문에 지연과 지연변이 그리고 패킷 손실 등이 발생하게 되어 서비스의 질에 큰 영향을 미치게 된다. 더욱이 멀티미디어 데이터는 시간에 민감하다는 속성 때문에 네트워크상의 지연이나 지연 변이는 클라이언트 측의 재생지연과 버퍼의 Underflow, 미디어간 동기의 어긋남을 발생시킬 수 있다. 본 논문에서는 이를 해결하기 위해서 네트워크나 서버 측에서의 접근이 아닌 클라이언트의 측면에서 접근하였다. 기존 adaptive한 기법[2][3]을 도입, 개선하므로써 클라이언트가 네트워크의 상태에 적응하여 지연과 지연변이의 영향을 최소화시키도록 클라이언트의 버퍼관리와 playback control을 설계하였다.ol을 설계하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.1014-1017
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• 2007

무선랜에서는 작은 셀 크기로 인해 노드들의 이동에 따른 빈번한 핸드오프가 이루어진다. 그래서 무선랜에서는 지속적인 통신 서비스를 제공하기 위한 방법으로 모바일 아이피와 같은 방법을 개발하고 있다. 모바일 아이피는 모바일 노드가 한 장소에서 다른 장소로 이동할 때 IP 주소의 변경 없이도 이동할 수 있도록 해준다. 그러나 모바일 아이피는 긴 시간의 등록과정과 연결 재설정 때문에 시간지연이나 패킷 손실과 같은 오버헤드를 발생시킨다. 따라서 무선랜의 QOS(Quality Of Service)를 향상시키기 위해서 Mobile IP 의 핸드오프 시간을 줄여야만 한다. 본 논문은 이러한 문제를 해결하기 위해 핸드오프 지연 시간을 감소시키는 기법을 제안한다. 제안기법의 기본 아이디어는 모바일 노드의 이동 네트워크를 예상하여, 미리 패킷 포워딩을 수행하는데 있다. 우리는 각 모바일 노드들에게 connection proxy table 정보를 추가하였다. 그리고 이 테이블 정보를 이용함으로써 모바일 노드들은 홈에이전트와 포린에이전트에 COA(Care of address)를 미리 등록하는 것이 가능해졌다. 그 결과로 이동 노드들은 홈 네트워크를 완전히 벗어나지 않고도 핸드오프가 이루어져 지속적인 서비스가 가능하였다. 본 논문에서 제안하는 기법이 기존 Mobile IP 와 비교해 볼 때 핸드오프가 이루어지는 동안 비 연결 시간을 줄일 수 있다는 것을 실험결과를 통해서 확인할 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.770-777
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• 2007

Smaller cell size in the micro-cell or pico-cell structure brings about more frequent hand-overs between cells, and higher speed movement of the mobile terminal makes short the permissible time interval for executing these hand-over procedures. In this situation the hand-over failure may occur or some packets may be lost during the hand-over. Moreover a rapid degradation of throughput is triggered by packet re-transmission for compensating such errors. The QoS (Quality of Services) of mobile multimedia applications with higher bits rate requirements and higher speed mobility are severely affected by even shot service interruption. This paper proposes a new hand-over scheme to provide seamless services in the next generation mobile communication systems. Simulation is done to evaluate the performance of the proposed scheme based on its hand-over failure rate and packet loss rate.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1211-1216
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• 2000

Asynchronous transfer mode (ATM) can be efficiently used to transport packet data services. The switching system will support voice and packet data services simultaneously from end to end applications. To guarantee quality of service (QoS) of the offered services, source rateot send packet data is needed to control the network overload condition. Most existing control algorithms are shown to provide the threshold-based feedback control technique. However, real-time voice calls can be dynamically connected and released during data services in the network. If the feedback control information delays, quality of the serviced voice can be degraded due to a time delay between source and destination in the high speed link. An adaptive algorithm based on the optimal least mean square error technique is presented for the predictive feedback control technique. The algorithm attempts to predict a future buffer size from weight (slope) adaptation of unknown functions, which are used fro feedback control. Simulation results are presented, which show the effectiveness of the algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.277-284
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• 2009

With significant development in wireless communication technologies, the needs to handover from one network to another have grown dramatically. Recently IETF developed MIPv6 and FMIPv6 which are used to handover between different access networks. These handover mechanisms have some known weaknesses. MIPv6 can not serve time-critical application because it causes long handover latency and packet loss. By these reasons, MIPv6 does not guarantee session continuity. FMIPv6 uses handover preparation phase to reduce DAD latency. However FMIPv66 still suffers from long handover latency, because it must perform binding update at the end of handover procedure. In this paper we propose new handover mechanism FMIPv6-PBU which eliminates binding update latency. The proposed mechanism has compatability with lagacy FMIPv6. In this paper propose FMIPv6-PBU handover procedure and explain its procedures and evaluate it with MIPv6 and FMIPv6.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.121-126
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• 2018

IEEE 802.1 TSN TG is developing standards for end-to-end delay bounds and zero packet loss based on Ethernet technology. We focus on packet forwarding techniques. TSN packet forwarding techniques can be classified into Synchronous and Asynchronous framework. Synchronous approach allocates fixed time period for a class, yet is complex for large networks. Asynchronous approach provides delay guarantee by regulator-scheduler pair, yet is unnecessarily complex, too. We propose network components for TSN Asynchronous architecture, which remove the complexity of maintaining flow state for regulation decisions. Despite such a simplicity, the proposed architecture satisfies the TSN's delay requirements provided the limited high priority traffic's maximum packet length.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.3
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• pp.57-66
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• 2011

The current trend of the handover authentication delay time is gradually increased according to the interworking between 3G cellular network and WLANs. Therefore, authentication mechanism minimized in delay is required to perform the seamless handover and support the inter-subnet and inter-domain handover. In this paper, we propose a novel pre-authentication scheme based on the fast channel switching which directly performs the authentication with the next access point in advance. In addition, the proposed scheme is efficient in the inter-domain handover and can be easily implemented in current WLANs since it just modifies the client side of user. To analysis and evaluate our scheme, we compare the packet loss ratio and the delay time with the two standard 802.11 authentication schemes. The analytical results show that our scheme is approximate 10 times more effective than the standard schemes in packet loss and the delay time is minimized down to 0.16 msec.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.2
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• pp.289-296
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• 2015

Wireless multimedia sensor network senses and transfers mass multimedia data. Also, it is sensitive to latency. This thesis proposes a routing technique based on traffic priority in order to improve the network efficiency by minimizing latency. In addition, it proposes a congestion control mechanism that uses packet service time, packet inter-arrival time, buffer usage, etc. In this thesis, we verified the reduction of packet latency in accordance with the quality level of packet as a result of the performance analysis through the simulation method. Also, we verified that the proposed mechanism maintained a reliable network state by preventing packet loss due to network overload.