• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.9-16
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• 2005

A new online routing algerian is proposed in this paper, which use the interference-prediction to solve the network congestion originated from extension of Internet scope and increasing amount of traffic. The end-to-end QoS has to be guaranteed in order to satisfy service level agreements (SLAs) in the integrated networks of next generation. For this purpose, bandwidth is allocated dynamically and effectively, moreover the path selection algorithm is required while considering the network performance. The proposed algorithm predicts the level of how much the amount of current demand interferes the future potential traffic, and then minimizes it. The proposed algorithm considers the bandwidth on demand, link state, and the information about ingress-egress pairs to maximize the network performance and to prevent the waste of the limited resources. In addition, the interference-prediction supports the bandwidth guarantee in dynamic network to accept more requests. In the result, the proposed algorithm performs the effective admission control and QoS routing. In this paper, we analyze the required conditions of routing algorithms, the aspect of recent research, and the representative algorithms to propose the optimized path selection algorithm adequate to Internet franc engineering. Based on these results, we analyze the problems of existing algorithms and propose our algorithm. The simulation shows improved performance by comparing with other algorithms and analyzing them.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.889-896
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• 2006

ATM Forum has defined a guaranteed frame rate (GFR) service to serve Internet traffic efficiently. The GFR service provides virtual connections (VCs) for minimum cell rate (MCR) guarantees and allows them to fairly share the residual bandwidth. And ATM Forum has recommended a frame-based generic cell rate algorithm (F-GCRA) as a frame classifier, which determines whether an Am cell is eligible to use the guaranteed bandwidth in a frame level. An ATM switch accommodates cells in its buffer or drops them in a frame level according to current buffer occupancy. A FIFO shared buffer has so simple structure as to be feasibly implemented in switches, but has not been able to provide an MCR guarantee for each VC without buffer management based on per-VC accounting. In this paper, we enhance the F-GCRA frame classifier to guarantee an MCR of each VC without buffer management based on per-VC accounting. The enhanced frame classifier considers burstness of TCP traffic caused by congestion control algorithm so as to enable each VC to use its reserved bandwidth sufficiently. In addition, it is able to alleviate the unfairness problem in usage of the residual bandwidth. Simulation results show that the enhanced frame classifier satisfies quality of services (QoSs) of the GFR service for the TCP traffic.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.3
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• pp.196-201
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• 2013

In this paper, we propose an asynchronous and adaptive message passing scheme based on S-MAC for handling with the problem on energy efficiency in wireless sensor networks. The proposed scheme consists of a policy that differentiate transmission errors caused by packet collision or radio interference from congestion errors caused by buffer overflow and a method that adaptively controls the size of a fragment according to the variance of traffic loads. Especially, it presents a method that highly reduce the energy consumption by keeping the size of fragment not being excessively smaller than the one that may result in rapid increment of the total transfer time. Finally, with the simulation results we show that network throughput and delay are improved by using the proposed message passing scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.758-767
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• 2017

IoT paradigm which makes a information without direct intervention of a human and interworks with other objects, humans and systems is attracting attention. It will be expected the number of smart devices equipped with sensors and wireless communication capabilities is reached to about 260 billion by 2020. With the vast amount of sending data generated from rapidly increasing number of smart devices, it will bring up the traffic growth over internet and congestion in wireless networks. In this paper, we utilize the smart device as a sink node to collect and forward the sensing data periodically in IoT and propose a heuristic algorithm for a selection of sink nodes' set with each sink node satisfies the QoS its applications because a selection of optimal sink nodes' set is NP-hard problem. The complexity of proposed heuristic algorithm is $O(m^3)$ and faster than the optimal algorithm.

• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.153-158
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• 2008

The technology of Software Defined Radio (SDR) is a possible solution to interwork flexibly between various wireless transport protocols. Ubiquitous network, like u-health service network, includes sensor devices or nodes which do not facilitate all the same transport protocols to access network. As such this may be in such unreachable situations as poverty of all required AP (Access Point)’s, faults or contention in a path of particular protocol communication, etc. This paper presents research results of modeling and simulation to analyze transport performance of multi-protocol ubiquitous network which includes SDR-based interwork nodes and congestion-controlled AP’s. Focusing mainly on dynamics of overall transport performance rather than protocol execution procedures, this paper employs the Zeigler’s DEVS (Discrete Event Systems Specification) methodology and DEVSim++simulation environment to experiment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.104-113
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• 2009

Recently, high-speed Internet users and broadband network infrastructure are increasing. However, the TCP protocol widely used in the Internet is an appropriate transport only for the legacy Internet, it is inefficient for traffic transport for network environments with large bandwidth-delay product. In order to remedy this problem, there have been many researches about improved congestion control algorithms for broadband networks. In these studies, most of performance evaluation has been done by simulations. In this paper, after we reviewed the proposed high bandwidth transport layer protocols, we implemented a real testbed, measured the performance and analyzed the problems of high-speed transport protocols through the international research network TEIN2 between three nations, Korea, China, and Germany.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2811-2817
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• 2010

In this paper we propose the QAC-MAC that supports Quality of Service(QoS) and saves energy resources of the sensor node, and hence prolonging the lifetime of the sensor network with multiple sink nodes. Generally, the nodes nearest to the sink node often experience heavy congestion since all data is forwarded toward the sink through those nodes. So this critically effects on the delay-constraint data traffics. QAC-MAC uses a hybrid mechanism that adapts scheduled scheme for medium access and scheduling and unscheduled scheme based on TDMA for no data collision transmission. Generally speaking, characteristics of the real-time traffic with higher priority tends to be bursty and has same destination. QAC-MAC adapts cross-layer concept to rearrange the data transmission order in each sensor node's queue, saves energy consumption by allowing few nodes in data transmission, and prolongs the network lifetime.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.363-373
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• 2010

The existing QoS mechanisms for video streaming are short of the consideration for various user environments and the characteristic of streaming applying programs. In order to overwhelm this problem, studies on the video streaming protocols exploiting scalable video coding (SVC), which provide spatial, temporal, and qualitative scalability in video coding, are progressing actively. However, these protocols also have the problem to deepen network congestion situation, and to lower fairness between other traffics, as they are not equipped with congestion control mechanisms. SVC based streaming protocols also have the problem to overlook the property of videos encoded in SVC, as the protocols transmit the streaming simply by extracting the bitstream which has the maximum bit rate within available bandwidth of a network. To solve these problems, this study suggests TCP-friendly network adaptive SVC streaming(T-NASS) protocol which considers both network status and SVC bitstream property. T-NASS protocol extracts the optimal SVC bitstream by calculating TCP-friendly transmission rate, and by perceiving the network status on the basis of packet loss rate and explicit congestion notification(ECN). Through the performance estimation using an ns-2 network simulator, this study identified T-NASS protocol extracts the optimal bitstream as it uses TCP-friendly transmission property and perceives the network status, and also identified the video image quality transmitted through T-NASS protocol is improved.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.9
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• pp.73-80
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• 2004

In this paper, we present the cell resequencing buffer to solve the cell sequence integrity problem of the Cyclic banyan network that is a high-performance fault-tolerant cell switch. By offering multiple paths between input ports and output ports, using the deflection self-routing, the Cyclic banyan switch offer high reliability, and it also solves congestion problem for the internal links of the switch. By the way, these multiple paths can be different lengths for each other. Therefore, the cells departing from an identical source port and arriving at an identical destination port can reach to the output port as the order that is different from the order arriving at input port. The proposed cell resequencing buffer is a hardware sliding window mechanism. to solve such cell sequence integrity problem. To calculate the size of sliding window that cause the prime cost of the presented device, we analyzed the distribution of the cell delay through the simulation analyses under traffic load that have a nonuniform address distribution that express tile Property of traffic of the Internet. Through these analyses, we found out that we can make a cell resequencing buffer by which the cell sequence integrity is to be secured, by using a, few of ordinary memory and control logic. The cell resequencing buffer presented in this paper can be used for other multiple paths switching networks.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.34-43
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• 2007

Recently, in addition to the sharp increase of mobile nodes, various kinds of wireless technologies are available for mobile nodes. If IPv6 technology is applied to the network, multi-homing terminals which have several public IP addresses on one interface will be common. Accordingly, there are many research activities on mobility management for multi-interface, multi-homming nodes. In this paper we propose an extended fast handover mechanism for multi-interface MIPv6 environments that uses multi-interface FBU (MFBU) message instead of the existing FBU message. The MFBU message has the "tunnel destination" mobility option that points a specific tunnel destination other than NAR, and "T" flag that indicates the existence of tunnel destination option. The proposed mechanism can improve the TCP performance by mitigating packet reordering during FMIPv6 handover that can cause unnecessary congestion control due to 3 duplicate ACKs. In this paper, we implemented a multi-Interface MIPv6 simulator by extending a single-interface MIPv6 simulator in NS-2, and showed that the performance of TCP traffic is improved by using the proposed multi-interface fast MIPv6.