• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8B
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• pp.1426-1437
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• 1999

The introduction of fast packet switching networks such as the ATM leads to the possibility of video services with constant quality. However, the fixed traffic descriptor(TD), which is defined by ATM Forum and ITU-T, can not simultaneously satisfy network efficiency and video quality. This paper presents fast resource reallocation protocol (FRRP) which can provide an effective compromise between network efficiency and video quality. This protocol reallocates the network resources and then adapts the traffic to the reallocated resources. In the proposed method, a video session is divided into several time-intervals according to its generated traffic and TD is calculated which well characterizes the traffic during the specific subdivided interval. In addition, a system model, where MPEG coding algorithm and network control are unified, is proposal and the performance of the FRRP in terms of cell loss rate(CLR) is evaluated though the simulation using real video traffic(Star Wars). Simulation results show that the FRRP has only 5 ~35% CLR of the fixed TD.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.95-117
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• 2006

In this paper, we describe the optimization of the link-level performance and the complexity of floating-point and fixed-point methods in IEEE 802.16e OFDMA/TDD mobile modem. In floating-point design, we propose the channel estimation methods for downlink traffic channel and select the optimized method using computer simulation. So we also propose efficent algorithms for time and frequency synchronization, Digital Front End and CINR estimation scheme to optimize the system performance. Furthermore, we describe fixed-point method of uplink traffic and control channels. The superiority of the proposed algorithm is validated using the performances of Detection, False Alarm, Missing Probability and Mean Acquisition Time, PER Curve, etc. For fixed-point design, we propose an efficient methodology for optimized fixed-point design from floating-point At last, we design fixed-point of traffic channel, time and frequency synchronization, DFE block in uplink and downlink. The tradeoff between performance and complexity are optimized through computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.495-507
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• 2006

In wireless local area networks (WLANs), the successful design of scheduling algorithm is a key factor in guaranteeing the various quality of service (QoS) requirements for the stringent real-time constraints of multimedia services. In this paper we propose a multipolling-based dynamic scheduling algorithm for providing delay guarantees to multimedia traffics such as MPEG streams. The dynamic algorithm exploits the characteristics of MPEG stream, and uses mini frames for feedback control in order to deliver dynamic parameters for channel requests from stations to the point coordinator (PC) operating at the access point (AP). In this scheme, the duration of channel time allocated to a station during a superframe is changed dynamically depending on the MPEG frame type, traffic load and delay bound of the frame, etc. Performance of the proposed scheme is investigated by simulation. Our results show that compared to conventional scheme, the proposed scheme is very effective and has high performance while guaranteeing the delay bound.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.11
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• pp.1-12
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• 2005

In wireless personal area networks(PANs), the successful design of channel time allocation algorithm is a key factor in guaranteeing the various quality of service(QoS) requirements for the stringent real-time constraints of multimedia services. In this paper we propose a dynamic channel time allocation algerian for providing delay guarantees to multimedia traffics such as MPEG streams in the IEEE 802.15.3 high-rate WPANs. The dynamic algorithm exploits the characteristics of MPEG stream, wherein the devices (DEVs) send their channel time requests only at the end of superframe boundaries. The algerian uses mini packets for feedback control in order to deliver dynamic parameters for channel time requests from the DEVs to the piconet coordinator (PNC). In this scheme, the duration of channel time allocated to a DEV during a superframe is changed dynamically depending on the MPEG frame type, traffic load and delay bound of the frame, etc. Performance of the proposed scheme is investigated by simulation. Our results show that compared to traditional scheme, the proposed scheme is very effective and has high performance while guaranteeing the delay bound.

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.101-108
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• 2001

In this paper we focus on dynamic reservation slot allocation scheme for supporting QoS of a voice traffic in WATM MAC. Especially, voice traffic is the most important real-time object, and so we propose a new MAC protocol for voice traffic over WATM networks in the multimedia environment. According to the characteristics of voice traffic which is repeatedly in silent state and active state, new protocol allocates reservation slots dynamically with respect to the number of silent voice source of which starting time is stored to the state table in base station (BS). The simulation results show that the proposed protocol has better performance than slotted ALOHA in average access delay, collision rate, better than NC-PRMA(Non Collision Packet Reservation Multiple Access) in band width efficiency, and can provide a certain level of QoS requirement by the given slot assignment even though the number of voice terminals is increased.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.237-239
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• 1998

ATM 망에서 이루어지는 다양한 멀티미디어 서비스를 무선 ATM망에서 지우너하기 위해서는, 단말의 이동에 위해 핸드오프가 일어날 때, 주위 셀의 상태와 다양한 클래스의 트래픽 특성을 고려한 무선 호 수락 제어 문제가 해결되어야 한다. 본 논문에서는 셀수준(cell-level)에서 인접 셀의 상태 정보를 이용한 분산 호 수락제어기법(DCA)과 현재 무선 셀에서 발생하는 클래스별 호들에 대한 할당을 위한 자원공유 알고리즘인 Ra방식을 조합하여 멀티 셀 환경에서 멀티 클래스 서비스별 QoS를 고려한 적응적인 무선화 수락제어 기법인 RA-DCA기법을 제안한다. 또한 제안된 호 수락 제어 기법의 성능분석을 위한 모델과 시뮬레이션 결과를 분석하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.454-456
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• 2005

최근에 파일 공유 애플리케이션을 개발하는데 있어 클라이언트-서버(client-sewer) 모델의 문제점을 해결하기 위해 피어-투-피어(peer-to-peer) 모델이 각광 받고 있다. 대표적일 P2P 기반 파일 공유 시스템으로 넵스터, 그누텔라등이 있다. 그러나 이 시스템들은 각각 중앙 집중적 제어, 혹은 브로드캐스팅에 의한 과도한 네트워크 트래픽 발생 등 확장성 문제를 발생시킨다. 이런 문제점을 해결하기 위해 울트라피어 및 동적 라우팅 기법을 사용하지만 여전히 rare 파일에 대한 높은 응답시간과 검색의 낮은 신뢰성 문제점들을 해결할 수 없다. 본 논문에서는 popular 파일과 rare 파일에 대한 검색을 구분하여 popular 파일을 기존의 그누텔라 검색 방법을 사용하고 rare 파일 검색을 제안하는 새로운 DHT 알고리즘을 사용하도록 한다. 특히 제안하는 DHT 알고리즘은 기존의 DHT 알고리즘들과 달리 일반 노드가 아닌 울트라피어들만으로 구성함으로서 검색 비용, 노드 조인과 리브 비용, 핑거 테이블의 엔트리 수를 매우 줄임으로서 효과적이고 확장적이라 할 수 있다.

• Journal of Broadcast Engineering
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• v.18 no.3
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• pp.491-494
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• 2013

This paper proposes a stochastic/dynamic routing protocol which aims the minimization of the summation of time average expected power expenditure with buffer stability in mobile ad-hoc 60 GHz wireless networks. By using 60 GHz RF, the wireless devices can transmit/receive 1080p HD video signals without compression. In addition, our algorithm works without centralized controller, so that the distributed operation is available. The novelty of the proposed algorithm was also verified by simulations.

• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.229-234
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• 2005

We propose a fuzzy logic-based buffer management algorithm to improve internet traffic over ATM-GFR service. The proposed algorithm employs the strategies of early congestion detection and selective packet discard to achieve its design goals. A key feature of proposed algorithm is its ability to accept or drop a new incoming packet dynamically based on buffer condition and load rate of VCs. This is achieved by using fuzzy logic controller for the production of a drop factor. Simulation results show that proposed scheme significantly has improved fairness and TCP throughput compared with previous schemes.

• Journal of Korea Multimedia Society
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• v.11 no.2
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• pp.197-205
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• 2008

TCP packets occupy over 90% of current Internet traffic thus understanding of TCP throughput is crucial to understand Internet. Under the TCP congestion regime, heterogeneous flows, i.e., flows with different round-trip times (RTTs), that share the same bottleneck link will not attain equal portions of the available bandwidth. In fact, according to the TCP friendly formula, the throughput ratio of two flows is inversely proportional to the ratio of their RTTs. It has also been shown that TCP's unfairness to flows with longer RTTs is accentuated under loss synchronization. In this paper, we show that, injecting bursty background traffic may actually lead to new type of synchronization and result in unfairness to foreground TCP flows with longer RTTs. We propose three different metrics to characterize traffic burstiness and show that these metrics are reliable predictors of TCP unfairness.