• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.945-950
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• 2002

In this paper the performance evaluations on Asynchronous Transfer Mode(ATM) access node are performed in the ATM access network which consists of access node and channel. The performance factors of access node are Cell Loss Ratio(CLR), buffer capacity and delay time. Both the ATM cell-scale queueing model and burst-scale queueing model are considered as the traffic model of access node for various traffic types such as Constant Bit Rate(CBR), Variable Bit Rate(VBR) and random traffic in the ATM access networks. Based on these situations, the relation of CLR, buffer capacity and delay time is analyzed in the ATM access node.

• Journal of Internet Computing and Services
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• v.9 no.4
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• pp.61-68
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• 2008

Ethernet passive optical network (EPON) is the next-generation technology mitigating the bottleneck between high-capacity local area networks (LANs) and a backbone network. The bottleneck is aggrevated depending on burstiness and long range dependence (LRD) of traffic characteristics as well as amount of outgoing traffic from the high-capacity LANs. The proposed scheme decreases average packet delay for data upstreaming by considering such traffic characteristics to dynamically allocate bandwidth to multiple optical network units (ONUs). In addition, it can appropriately support delay-sensitive traffic such as constant bit ratio (CBR) traffic by making maximum cycle time fix regardless of the number of ONUs. The comprehensive simulation results indicate that the proposed scheme acheives up to 77% and 82% lower than previous schemes in terms of average packet delay and average queue size while it limits the maximum cycle time to twice of the basic cycle time.

• Journal of the military operations research society of Korea
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• v.30 no.1
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• pp.107-134
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• 2004

Today's Internet is providing a single service which is so-called "best-effort service". Now, multimedia and real-time applications are not only demanding large bandwidth but also requiring high QoS. For this, MPLS and DiffServ technology can be adopted to support more scalability and QoS for data traffic engineering. The DISN(Defense Information Systems Network) supports CBR service for voice traffic and VBR service for data traffic which is best-effort service. We propose how to adopt MPLS and DiffServ technology to support traffic engineering and guarantee QoS in the DISN. A traffic analysis according to prioritized traffic classes is done using OPNET simulation tool for assuring QoS. The result shows that low priority packets are delayed a little bit, but high priority packets are transferred more efficiently than without traffic engineering.gineering.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.277-280
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• 1998

As user's demands for high-speed data traffic are recently increased, ABR services are considered as one of important service requirements in ATM networks. Unfortunately, a number of existing ATM switching systems have structural drawbacks as to support ABR services because these switching systems have been developed to support realtime(rt) services such as CBR and rt-VBR services. To support ABR services in the existing ATM switching systems, new traffic control mechanisms for ABR services are required. This paper proposes a method for supporting ABR services in ATM swithcing systems without back-pressure mechanisms and evaluates the performance of the proposed method using simulation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.3
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• pp.54-64
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• 1998

In this paper, a cell scheduling algorithm is proposed to satisfy the service requirements of CBR, VBR traffics. Particularly, inthe proposed algorithm an ABR traffic which is not included in the conventional cell schedulaing algorithm is treated as one kind of traffic types. The algorithm of RT-VBR and NRT-VBR traffic such that the service requrements of RT-VBR and NRT-VBR traffic are satisfied. The proposed algorithm dynamically schedules cells in a real time by considerin the current traffic conditions. The simulation of the proposed algorithms such as WRR or DWRR in terms of the mean delay time and the maximum queue length.

• Journal of Korea Multimedia Society
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• v.4 no.4
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• pp.339-348
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• 2001

In this paper, a cell scheduling algorithm which can be applied to all of the service class in ATM network is proposed. The proposed algorithm classifies the order of priority in each service class into 4 categories and generates the weight of each class service based on the traffic parameters which are negotiated in connection contract. The proposed algorithm guarantees QoS(Quality of Service) to the traffic which is sensitive to delay carrying out CBR and rt_VBR service. As it effectively manages the connection which has small bandwidth, it minimizes the cell delay in the queue. For verifying the effectiveness of the proposed algorithm the proposed algorithm is simulated with existing cell scheduling algorithm and the result is showed.

• International Journal of Computer Science & Network Security
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• v.22 no.7
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• pp.13-20
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• 2022

Basically Mobile Ad Hoc Network (MANET) is an autonomous system with the collection of mobile nodes, these nodes are connected to each other by using wireless networks. A mobile ad hoc network poses this quality which makes topology in dynamic manner. As this type of network is Ad Hoc in nature hence it doesn't have fixed infrastructure. If a node wishes to transfer data from source node to a sink node in the network, the data must be passed through intermediate nodes to reach the destination node, hence in this process data packet loss occurs in various MANET protocols. This research study gives a comparison of various Mobile Ad Hoc Network routing protocols like proactive (DSDV) and reactive (AODV, DSR) by using random topology with more intermediate nodes using CBR traffic. Our simulation used 50, 100, and 150 nodes variations to examine the performance of the MANET routing protocols. We compared the performance of DSDV, AODV and DSR, MANET routing protocols with the result of existing protocol using NS-2 environment, on the basis of different performance parameters like Packet Delivery Ratio, average throughput and average end to end delay. Finally we found that our results are better in terms of throughput and packet delivery ratio along with low data loss.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.28-34
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• 1998

In ATM networks CBR data traffic is sent in constant bit rate, and VBR data traffic in variable bit rate. Therefore unused bandwidth at network capacity may exist. To avoid waste of network resourcesm, ABR traffic utilizes the unused bandwidth to the utmost after CBR and VBR data traffic being first served. In this paper, a transfer rate-based congestion control algorithm is proposed for efficient ABR service in ATM networks. In the proposed algorithm the ATM switch first calculates bandwidth according to variable cell transfer rate in an ABR source. records this value in ER field in a RM cell, and then transmits a RM Cell to an ABR source. In this way the proposed algorithm dynamically allocates bandwidth to each ABR source, and the switch also can rapidly adapt to a change of a transfer rate of an source. The performance simulation of the proposed algorithm has batter performance in terms of source condition and link utilization.

• The Transactions of the Korea Information Processing Society
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• v.5 no.12
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• pp.3185-3193
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• 1998

ATM망은 망 내부의 큐잉 랜덤 지연에 의한 CDV의 발생으로 클럭복원의 문제를 안고 있다. 큐잉에 의한 지연은 여러 가지 파라메터에 의해 좌우되며 특히 망의 부하와 트래픽이 전송되는 교환기의 수에 의해 크게 좌우된다. CBR 트래픽의 경우 이를 해결하기 위해 SAR 헤더에 송신부의 클럭 정보를 담아 보내고 수신부에서는 이 정보를 바탕으로 송신부의 클럭을 복원하는 SRTS 기법을 사용하고 있다. 그러나 실시간성을 요하는 VBR 트래픽은 CBR과는 달리 대역폭의 가변적인 성질을 가지고 있으며 그 변화가 다양하여 SRTS 기법을 그대로 적용하기 곤란하다. VBR의 경우에 CBR 전송을 위한 SRTS 기법을 그대로 적용하면 주파수의 가변성으로 인해 망 클럭 주파수에 비해 매우 낮은 주파수의 경우에는 사이클이 상대적으로 많아 정보의 정확성이 떨어지게 된다. 이를 방지하기 위해 서비스 클럭의 주파수가 낮은 경우에는 망 기준 주파수를 낮게 하므로써 정확성을 증가시킬 수 있다. 또한, VBR 트래픽의 경우 AAL1에서는 SRTS의 필요성이 강조되지 않으나 단지 CDV를 제거할 방법이 요구되어진다. 따라서 AAL1의 SRTS를 CDV의 측정을 위한 메카니즘으로 바꾸는 것이 필요하며, 각 기반으로하여 Wavelet 변환을 이용한 VBR 트래픽의 클럭 복원방식을 제안한다. 제안된 알고리즘은 ATM망에서 VBR 영상 서비스를 위한 AAL 계층에 이용이 가능하다. 시뮬레이션 결과는 wavelet 변환 블록에서 출력되는 계수 값을 선택하여 전송함으로써 VBR 트래픽의 보다 다양한 QoS를 만족시킬 수 있음을 보인다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.325-329
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• 2007

The mobile and multimedia service on wireless network have been leaded from the improvement of telecommunication techniques. A typical multimedia service, a video transmission usually requires larger bandwidth than voice transmission. Many channel allocation algorithms for Orthogonal Frequency Division Multiple Access (OFBMA) to use resources more efficiently, Previous channel allocation algorithms have developed with an assumption that the data traffic is constant bit rate (CBR). However, existing algorithms are not suitable to video traffic because it usually generates a variable bit rate (VBR) traffic. In this paper, we proposed a new channel allocation algorithm called a queue-based channel allocation. it is more suitable to transmit the video traffics. Also, a problem are notified in case of realtime generated video traffic and a corresponding heuristic solution was proposed.