• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.152-155
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• 1999

ATM은 다양한 종류의 실시간 및 비실시간 트래픽을 지원할 수 있도록 기존의 회선 교환망과 패킷 교환망의 장점을 수용하여 셀이라는 일정한 크기의 패킷을 비동기식 시분할 방식으로 전송하는 방식이다. 이와 같은 ATM은 STM가 달리 대역폭의 효율적인 할당이 가능하므로 기존의 망에서 다루고 있는 데이터 통신 서비스 외에도 고화질의 화상이나 동영상, 멀티미디어 트래픽 제어는 실시간 접속에 대한 서비스 품질(QoS)의 보장이 요구되므로 본 논문은 망내에서 트래픽 왜곡과 CBR/VBR 접속에 대한 트래픽의 일반적 패턴과 셀 큐잉 지연 범위를 획득하여 최악의 규잉 분석을 모델링할 수 있는 비트 스트림 트래픽 모델에 기반을 둔 트래픽 제어 기법이 비트 스트림 제어 알고리즘을 제안한다. 제안된 알고리즘은 정적 우선순위스케줄링과 FIFO 큐잉 스위치를 갖는 ATM 망에서 엄격한 실시간 통신 서비스를 제공할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8B
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• pp.752-759
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• 2002

The capacity of the cell varies with the load of the home and neighboring cells. But most call admission control (CAC) algorithms do not consider the cell loading. In this paper a dynamic call admission control is proposed in a WCDMA system with traffic asymmetry. The proposed algorithm changes the CAC thresholds of new call and handoff call based on channel condition. The blocking and dropping probabilities can be controlled by adjusting these thresholds. The proposed algorithm guarantees the Qos of call class and priority between new call and handoff call. In addition, it can minimize the grade of service (GOS) value with the system throughput maintained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3B
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• pp.191-199
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• 2003

In this paper, a channel access control algorithm and a dynamic slot allocation algorithm are proposed for rt_VBR services and ABR services in the wireless ATM networks. In the proposed algorithm, rt_VBR terminals that require real-time services transmit a reservation request packet by a RAS minislot. An rt_VBR terminal, which transmitted the reservation request packet, transmits the dynamic parameters by DPS minislot without contention. On the other hand, ABR terminals that have a non-real-time traffic burst transfer a reservation request packet with contention basis. Based on the received dynamic parameters, the base station scheduler allocates uplink data slots as well as DPS minislot into rt_VBR terminals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10B
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• pp.854-861
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• 2003

In this paper, we proposed the fuzzy control algorithm for efficient buffer control about traffic that is connected in ATM networks. The proposed Fuzzy control algorithm has total traffic arrival ratio, buffer occupancy ratio and Fuzzy set to search for dynamic service rates in server. That is, is based on Fuzzy logic according to the arrival ratio of total traffic and buffer occupancy ratio that is happened and reasoning. Then, made reasoning result control service rates in server about traffic that is connected with defuzzification value. Performance analysis result: it was confirmed that with the proposed scheme, performance improves at cell loss rate, when compared with the existing PBS scheme.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.306-307
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• 2017

본 논문에서는 태양광모듈과 전력변환장치간의 접속장치로 사용된 전력용 반도체 스위칭 소자의 소프트 스타팅 기법을 통해 초기 돌입전류를 저감하는 알고리즘을 제안하고자 한다. 태양광 모듈의 경우, 릴레이나 DC차단기 등을 사용하여 전력변환장치와 연동하는 것이 일반적이나, 이 경우 태양광모듈의 수명과 접속장치의 전압 강하 및 응답성 등의 문제를 야기한다. 또한, 전력변환장치 출력단의 커패시터에 초기 동작 시 과도한 동일전류가 발생하게 되고 이는 태양광모듈의 과전류 현상을 발생시켜 모듈의 수명과 더불어 퓨즈의 차단 및 발열 등 비이상적인 현상을 발생시킨다. 따라서, 본 논문에서는 이러한 문제점을 해결하고자 스위칭 소자를 사용한 접속장치 적용하였고, 소프트 스타팅 기법을 이용하여 돌입전류를 저감하고자 한다. 제안한 알고리즘의 경우, 시뮬레이션을 통해서 검증하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6B
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• pp.406-415
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• 2005

The standards which use shared medium like IEEE 802.11 wireless LAN have transmission opportunity by contention in contention period. If there are collisions in contention period, medium access control protocol may solve problem by using backoff algorithm. Backoff algorithm is important part in medium access control, but legacy backoff method which is used under IEEE 802.11 standards is not adjusted when load is heavy because of increasing collisions. In this paper, we propose a new load-based dynamic backoff algorithm in contention-based wireless shared medium to improve throughput of medium and to reduce the number of collisions. Proposed backoff algorithm can increase the network utilization about $20\%$ higher than that of binary exponential backoff algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.561-564
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• 2005

This paper proposes an access control algorithm for guaranteeing fair packet transmissions in CDMA-based slotted ALOHA systems. In the proposed algorithm, the base station calculates the packet transmission and retransmission probabilities based on the offered loads and then broadcasts these probabilities to all mobile stations. Mobile stations, which have a packet to transmit, attempt to transmit a packet with the received probabilities. Simulation results show that the proposed algorithm can offer better system throughput and average delay than the conventional algorithm. Results also show that the proposed algorithm can guarantee a good fairness among all mobile stations regardless of the offered loads.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.3
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• pp.8-17
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• 1999

무선 ATM망에서 다수 연결채널로부터 발생되는 트래픽의 서비스 질을 보장하고 한정된 무선 자원을 효율적으로 사용하기 위해서는 다중접속제어 기술이 중요한 설계요소 중 하나이다. 본고에서는 ATM 프로토콜 특성을 무선 구간에 까지 확장한 동적다중슬롯할당(DMSA: Dynamic Multi-Slot Assignment)기법의 단점 중 하나인 연결채널별 지연 성능의 차이에 대해 분석하고, 이를 해결하기 위하여 이동국으로부터 각 연결채널에 대해 전달되는 정보를 이용하여 중앙제어국에 가상큐를 도입하는 방안을 제안한다. 중앙제어국에서는 구성된 가상큐룰 이용하여 상향링크의 다음 한 프레임내 모든 타임슬롯에 대한 연결채녈 할당을 수행한다. 다양한 트래픽 소스에 대한 시뮬레이션을 통해 가상큐-동적다중슬롯할당 알고리즘이 기존의 동적다중슬롯할당 알고리즘에 비해 중앙제어국에서의 단순한 제어 부하만으로도 다수의 연결채널에 대해 균등한 설비스 질을 보장하고 지연 변이 특성의 성능 향상을 나타냄을 입증한다. 이러한 연구결과는 동종 혹은 이종의 트래픽을 가진 각 연결 채널에 대해 무선 구간의 분산 환경으로 인해 발생할 수 있는 불평등성을 해결함으로써 무선 ATM의 개념을 우선 ATM과 유사한 환경으로 분석할 수 있는 계기를 마련한 것으로 판단된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.684-690
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• 2003

In this paper, a contention-based reservation access control algorithm and a slot allocation algorithm are proposed for non-real-time bursty traffic services in the wireless ATM networks. In order to reduce the collisions of the reservation request packets, the base station scheduler calculates the transmission probability using the number of RAS minislots and the estimated load of the reservation request packets. And it broadcasts the calculated transmission probability over the downlink control channel. Mobile terminals, which have traffic burst, select randomly a RAS minislot and transmit the reservation request packet by the received transmission probability. The reservation request packet contains the number of packets in the buffer. The slot allocation is based on the buffer status of the received reservation request packets. The base station scheduler allocates slots in proportion to the total number of slots that are requested by each terminal.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1333-1340
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• 2015

IEEE 802.11 MAC(Media Access Control) defines DCF(Distributed Coordination Function) for data transmission control. BEB(Binary Exponential Backoff) algorithm of DCF has a problem that if the number of stations connected are over a certain threshold, it degrades network performance because of packet collisions caused from the minimum contention window size. To cope with this problem, we proposed a novel algorithm, named as VBS(Variable Backoff Stage) algorithm, which adjusts the rate of backoff stage increment depending on the number of stations associated with an AP(Access Point). Analytic model of proposed algorithm was derived and simulations on the BEB and the VBS algorithms have been conducted on the OFDM (Orthogonal Frequency Division Multiplexing) method. Simulation results showed that when the rate of backoff state increment was 5 and 10, the number of retransmission were reduced to 1/5 and 1/10 comparing to that of BEB, respectively. Our algorithm showed improvement of 19% and 18% in network utilization, respectively. Packet delay was reduced into 1/12.