• Journal of Internet Computing and Services
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• v.8 no.5
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• pp.125-132
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• 2007

Transmission mechanisms that include an available bandwidth estimation algorithm and a packet loss differentiation scheme, in general, exhibit higher TCP performance in wireless networks. TCP New Jersey, known as the best existing scheme in terms of goodput, improves wireless TCP performance using the available bandwidth estimation at the sender and the congestion warning at intermediate routers. Although TCP New Jersey achieves 17% and 85% improvements in goodput over TCP Westwood and TCP Reno, respectively, we further improve TCP New Jersey by exploring improved available bandwidth estimation, retransmission timeout, and recovery mechanisms. Hence, we propose TCP New Jersey PLUS (shortly TCP NJ+), showing that under 1% packet loss rate, it outperforms 3% by TCP New Jersey and 5% by TCP Wes1wood. In 5% packet loss rate, a characteristic of high bit-error-rate wireless network, it outperforms other TCP variants by 19% to 104% in terms of goodput even when the network is in bi-directional congestion.

• Journal of Internet Computing and Services
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• v.11 no.2
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• pp.1-15
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• 2010

The damage of safety accidents at home can be minimized by preventing accidents in advance as well as by coping with the accidents promptly through the help of safety management system. In this paper, we identify several services to prevent and cope with the accidents that may occur at home by leveraging sensors and wireless network technology available at home network environments. In order to provide these services, we propose a context-aware system for safety management at home. The proposed system awares the dangerous situations through the information collected by the sensors in home network environment. The proposed system tries to not only prevent the accidents but also to cope with the situations using the information of rescue targets and the location where the accident occurs. We evaluate the appropriateness of sensors by implementing the proposed environments. Through OPNET simulation experiments, we also measure the amount of network traffic in order to confirm that the bandwidth of IEEE 802.15.4 is enough for the proposed system. Finally, we determine more appropriate wireless data transmission mechanism with respect to the end-to-end delay and battery consumption for the proposed system.

• Journal of Internet Computing and Services
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• v.21 no.5
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• pp.149-157
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• 2020

Recently, as interest in artificial intelligence has increased, many studies have been conducted to implement AI processors. However, the AI processor requires functional verification as well as performance verification on whether the AI processor is suitable for the application. In this paper, We propose an AI processor performance analyzer that can verify the application performance and explore the limitations of the processor. By Using the performance analyzer, we explore the limitations of the AI processor and optimize the AI model to fit an AI processor in image recognition and speech recognition applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.221-231
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• 2006

TCP is needed as a transport protocol to provide reliable end-to-end message delivery for MANETs in order to achieve a smooth integration with the fixed Internet. Particularly, TCP has its variants, namely TCP-Reno and TCP-Vegas. However, there has been no research work on extensive performance comparison of TCP-Reno and TCP-Vegas over AODV and OLSR. This paper is the first trial to perform the research by using ns-2 simulator. Through the extensive simulations, we found that which to select among routing protocols is more important than which to select among TCP variants, because the performance difference between TCP-Reno and TCP-Vegas over uy selected routing protocol is not so much outstanding. Particularly, TCP-Vegas relies on an accurate BaseRTT estimation in order to decide the sending rate of a TCP Sender. However, it cannot be directly applied to MANET because a route change makes the Base an used over a Previous Path obsolete. Therefore, we propose a technique for improving the performance of TCP-Vegas by considering the route change, and show the performance improvement through simulation study.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7C
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• pp.677-684
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• 2002

Today's Internet does not have efficient traffic engineering mechanism to support QoS for the explosive increasing internet traffic such as various multimedia traffic. This functional shortage degrades prominently the quality of service, and makes it difficult to provide multi-media service and real-time service. Various technologies are under developed to solve these problems. IETF (Internet Engineering Task Force) developed the MPLS (Multi-Protocol Label Switching) technology that provides a good capabilities of traffic engineering and is independent layer 2 protocol, so MPLS is expected to be used in the Internet backbone network$\^$[1][2]/. The faults occurring in high-speed network such as MPLS, may cause massive data loss and degrade quality of service. So fast network restoration function is essential requirement. Because MPLS is independent to layer 2 protocol, the fault detection and reporting mechanism for restoration should also be independent to layer 2 protocol. In this paper, we present the experimental results of the MPLS OAM function for the performance monitoring and fault detection 'll'&'ll' notification, localization in MPLS network, based on the OPNET network simulator

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1679-1686
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• 2019

The main purpose of this research is to propose an approach for solving the packet loss problem by quickly adapting to topology change when nodes move in RPL-based IoT environment. In order to enhance mobility, every node is aware of the mobility of its neighbor nodes and quantifies the mobility level based on the number of control messages and all received packets. According to the mobility level, the DIO timer is changed. The proposed approach allows nodes to change their DIO timers according to their mobility levels to adapt topology changes and update paths to the sink. The performance of the proposed approach is evaluated using a Contiki-based Cooja simulator in various moving speeds. The simulation results show that the proposed approach copes with mobility scenarios better than the standard RPL by ascertaining that the packet delivery ratio is improved by 31.03%.

• Journal of Internet Computing and Services
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• v.16 no.4
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• pp.61-70
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• 2015

This paper presents a web-based Java applet for understanding the concepts in digital logic circuits and student satisfaction survey was carried out in order to show its educational validity. Through our educational Java applet, the learners will be capable of learning the concepts and principles related to digital logic circuit experiments and how to operate virtual experimental equipments and virtual bread board. The proposed educational Java applet is composed of five important components: Principle Classroom to explain the concepts and principles for digital logic circuit operations, Simulation Classroom to provide a web-based simulator to the learners, Virtual Experiment Classroom to provide interactive Java applet about the syllabus of off-line laboratory class, Assessment Classroom, and Management System. With the aid of the Management System every classroom is organically tied together collaborating to achieve maximum learning efficiency. Finally, we have obtained several affirmative effects such as high learning standard, reducing the total experimental hours and the damage rate for experimental equipments.

• 전자공학회논문지 IE
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• v.43 no.3
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• pp.41-48
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• 2006

In this paper, we propose a new active queue management (AQM) scheme by utilizing the predictability of the Internet traffic. The proposed scheme predicts future traffic input rate by using the auto-regressive (AR) time series model and determines the future congestion level by comparing the predicted input rate with the service rate. If the congestion is expected, the packet drop probability is dynamically adjusted to avoid the anticipated congestion level. Unlike the previous AQM schemes which use the queue length variation as the congestion measure, the proposed scheme uses the variation of the traffic input rate as the congestion measure. By predicting the network congestion level, the proposed scheme can adapt more rapidly to the changing network condition and stabilize the average queue length and its variation even if the traffic input level varies widely. Through ns-2 simulation study in varying network environments, we compare the performance among RED, Adaptive RED (ARED), REM, Predicted AQM (PAQM) and the proposed scheme in terms of average queue length and packet drop rate, and show that the proposed scheme is more adaptive to the varying network conditions and has shorter response time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1059-1067
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• 2006

AODV(Ad-hoc On-demand Distance Vector) routing protocol was devised for use of mobile nodes in Ad-hoc network. When we use the AODV routing protocol in Ad-hoc networks with high mobility, disturbance of optimized route path and link break occur. In order to solve the shortcomings, this paper proposes a new routing protocol in which new routing control messages are added to the existing AODV. The proposed protocol minimizes link break and transmission delay while is able to secure the optimized route path constantly in changes of network topology The performance of the proposed routing protocol was evaluated by using us2 network simulator. The actual Ad-hoc network test bed provides us the most reliable experimental data for Ad-hoc networks. In order to support this experimental environment, the dissertation also developed an efficient embedded system on which AODV routing protocol, NAT, Netfilter can run and other event message can be verified without declining efficiency. The correct operation of AODV routing protocol has been verified in both the Ad-hoc network test bed in which the embedded system was used, and Ad-hoc networks linked with Ethernet backbone network.

• Convergence Security Journal
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• v.17 no.5
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• pp.3-10
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• 2017

Standard Protocol Optimized for Resource-Constrained IoT Environment Constrained Application Protocol (CoAP) supports web-based communication between a sensor node in the IoT environment and a client on the Internet. The CoAP is a Request / Response model that responds to the client's CoAP Request message by responding with a CoAP Response message from the server. CoAP recommends the use of CoAP-DTLS for message protection. However, validation of the use of DTLS in the IoT environment is underway. We analyze CoAP and DTLS security mode, evaluate performance of secure channel creation time, security channel creation step time, and RAM / ROM consumption through Cooja simulator and evaluate the possibility of real environment application.