• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.6
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• pp.9-17
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• 2012

High-quality multimedia on the Internet has attracted attention because of its wide application area. IP multicast has been proposed as a solution to use efficient network resources in these services. However, IP multicast has not been commonly used due to a number of practical issues such as security and management. As an alternative, an overlay multicast routing which is performed in upper protocol layers on legacy networks without changing hardware has been presented. Yet, the maximum data transmission capacity of the overlay multicast is not sufficient for real time transmission of multimedia data. In this paper, we have implemented an overlay multicast engine on NetFPGA which allows us to perform packet replication and tunneling which need high-speed. In addition, we have implemented extra portions which need low-speed in software. From now on, we will progress research which increase the number of terminal spots which can be replicated by improvement and amplify throughputs by optimization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1655-1665
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• 2017

Recently data centers are being constructed actively by many cloud service providers, enterprises, research institutes, etc. Generally, they are built on tree topology using ECMP data forwarding scheme for load balancing. In this paper, we examine data center network topologies like tree topology and fat-tree topology, and load balancing technologies like MLAG and ECMP. Then, we propose a scheduling algorithm to efficiently transmit particular files stored on the hosts in the data center to the destination node outside the data center, where fat-tree topology and OpenFlow protocol between infrastructure layer and control layer are used. We run performance analysis by numerical method, and compare the analysis results with those of ECMP. Through the performance comparison, we show the outperformance of the proposed algorithm in terms of throughput and file transfer completion time.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.93-100
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• 2010

In this paper, we propose a technique which makes it faster to delete prefixes in an IP address lookup architecture based on parallel TCAMs. In previous deletion schemes, more than one memory movement is needed for the prefix ordering and keeping the available memory space consecutive. For deletion, our scheme stores the address of the deleted prefix in a stack implemented by SRAM instead of actual movement in TCAM. Since SRAM has very short latency compared to TCAM, the proposed scheme can accomplish fast updating. From the experiment with the real forwarding table and update trace, we evaluate the performance of our scheme in terms of the memory access time for the prefix insertion and deletion. The experiment result also shows good performance with considerably small size of stack.

• International Journal of Railway
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• v.3 no.2
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• pp.39-45
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• 2010

The RF-CBTC (Radio Frequency-Communication Based Train Control) System is a communication system in railroad systems. The communication method of RF-CBTC system is the wireless between the wayside device and on-board device. The wayside device collects its location and speed from each train and transmits the distance from the forwarding train to the speed-limit position to it. The on-board device controlling device controls the speed optimum for the train. In the case of the RF-CBTC system used in Korea, transmission frequency is 2.4 [GHz]. It is the range of ISM(Industrial Scientific and Medical equipment) band and transmission of voice and data is performed by CDMA (Code Division Multiple Access) method. So noises are made in the AWGN (Additive White Gaussian Noise) and fading environment. Currently, the SNR (Signal to Noise Ratio) is about 20 [dB], so due to bit errors made by noises, transmission of reliable information to the train is not easy. Also, in the case that two tracks are put to a single direction, it is needed that two trains transmit reliable voice and data to a wayside device. But, by noises, it is not easy that just a train transmits reliable information. In this paper, we estimated the BER (Bit Error Rate) related to the SNR of voice and data transmission in the environment such as AWGN and fading from the RF-CBTC system using the CDMA method. Also, we supposed the SNR which is required to meet the BER standard for voice and data transmission. By increasing the processing gain that is a ratio of chip transmission to voice and data transmission, we made possible voice and data transmission from maximally two trains to a wayside device, and demonstrated it by using Matlab program.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.659-665
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• 2006

When using the Mobile IP which is the representative technology to secure the mobility in general IP networks, the packet loss during the handover is inescapable. To remedy the packet loss problem, the smooth handover was introduced. However, the smooth handover causes the packets sequence disruption during the packet forwarding procedure and it may result in the degradation of the network performance. The same problem also occurs in the WiBro (High-speed Portable Internet) system that is the next generation portable IP service system. The WiBro system, which provides the high speed data service just like xDSL and leased line in wired internet, aims to guarantee the portability, mobility, and the differentiated service based on IEEE 802.16. So, the handover mechanisms that solve the problems of packet loss and packet sequence distribution are required in the WiBro system. In this paper, we propose the handover mechanism and the packet sequence control algorithm that provide the reliability and the differentiated service for the unicast service in the WiBro system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.437-445
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• 2000

More advanced and demanding applications, like videoconferencing, video on demand. distributed computing etc., have been devised thanks to the availability of enhanced network feature. Network technologies need to be enhanced to support these applications and to cope with the increasing number of users. Increasing the availability of network resources is just not enough to achieve this goal; scalable network architecture. increased packet forwarding capabilities, a wider range of services are all additional requirements. MOLS (multiprotocol label Switching) is one of the new networking techniques under standardization in the scientific community. In this paper, we analyze the performance of label switching in ATM networks. Simulation tests were performed. In this simulation, we set a simple network configuration and used internet traffic traces from NLANR as input traffic sources. The simulation results and analysis will be helpful in utilizing the functions of ATM switching and IP routing.

• Journal of Biomedical Engineering Research
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• v.22 no.6
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• pp.543-550
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• 2001

In this study, ground reaction force(GRF) and energy consumption of fixed. single-axis and multi-axis Prosthetic ankle assemblies were investigated to show the biomechanical evaluation for trans-tibial amputees. In the experiments. two male and two female trans-tibial amputees were tested with fixed, sin91e-axis and multi-axis Prosthetic ankle assembly. A three-dimensional gait analysis was carried out to derive the ratio of GRF to weight as the percentage of total stance Phase for nine Points Energy consumption of each Prosthetic ankle assembly was measured while subjects walked at 2km/h. 3km/h and the most comfortable walking speed on the treadmill The results showed that multi-axis ankle was superior to the other two ankle assemblies for the characteristic of forwarding and breaking forces. Fixed ankle was relatively superior to the other two ankle assemblies for gait balancing and movement of the center fur mass Compared to the other ankle assembly. sing1e-axis type showed lower energy consumption over 2.3km/h walking speed .

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.2
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• pp.189-197
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• 2016

Mobile ad-hoc networks (MANETs) experience frequent link disconnections due to non-uniform node distribution and mobility. Thus, end-to-end path establishment-based routing protocols cause frequent transmission failures in MANETs, resulting in heavy control messages for path reestablishment. While location-based MANET routing protocols, such as Greedy Perimeter Stateless Routing (GPSR), use location information to forward messages in a hop-by-hop routing fashion without an end-to-end path establishment procedure, such protocols encounter communication void problems when message forwarding to the next hop fails due to the absence of a relay node. Therefore, to solve this problem, this paper proposes a Delay Tolerant-GPSR (DT-GPSR) protocol, which combines Delay Tolerant Networking (DTN) technology with the GPSR protocol. The performance of DT-GPSR is compared with the performances of the original GPSR and PRoPHET routing protocols through simulation using NS-2. The simulation results confirm that DT-GPSR outperforms GPSR and PRoPHET in terms of the message delivery ratio and message delivery delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11B
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• pp.673-684
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• 2007

In this paper, we introduce an FARNS (Flooding algorithm with Adaptive Retransmission Nodes Selection). It is an efficient cross layer-based flooding technique to solve broadcast storm problem that is produced by simple flooding of nodes in wireless sensor network. FARNS can decrease waste of unnecessary energy by preventing retransmission action of whole network node by deciding retransmission candidate nodes that are selected by identification in MAC and distance with neighborhood node through received signal strength information in PHY. In simulation part, we show the results that FARNS has excellent performance than the other flooding schemes in terms of broadcast forwarding ratio, broadcast delivery ratio, number of redundancy packets and overhead. And FARNS can adjust of node ratio for retransmission operation, it can solve broadcast storm problem as well as meet the requirements of various network environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.344-355
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• 2008

In this paper, we are dealing with the problems of performance evaluation of Differentiated Services(DiffServ) networks. For successful performance evaluation, the ability to accurately represent "real" traffic on the network by suitable traffic models is an essential ingredient. Many research results on the nature of real traffic measurements demonstrated LRD(long-range dependence) property for the Internet traffic including Web, TELNET, and P2P traffic. The LRD can be effectively represented by self-similarity. In this paper, we design and implement self-similar traffic generator using the aggregated On/Off source model, based on the analysis of the On-Off source model, FFT-FGN(Fast Fourier Transform-Fractional Gaussian Noise) model, and RMD(Random Midpoint Displacement) model. We confirmed the self-similarity of our generated traffic by checking the packet inter-arrival time of TCPdump data. Further we applied the implemented traffic generator to the performance evaluation of DiffServ networks and observed the effect of performance to the a value of the On/Off model, and performance of EF/BE class traffic by CBQ.