• ETRI Journal
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• v.34 no.3
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• pp.352-360
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• 2012

This paper proposes a low-cost, low-power, and high-capacity optical-electrical-optical-type reach extender that can provide 3R frame regeneration and remote management to increase the reach and split ratio with no change to a legacy time division multiple access passive optical network. To provide remote management, the extender gathers information regarding optical transceivers and link status per port and then transmits to a service provider using a simple network management protocol agent. The extender can also apply to an Ethernet passive optical network (E-PON) or a gigabit-capable PON (G-PON) by remote control. In a G-PON, in particular, it can provide burst mode signal retiming and burst-to-continuous mode conversion at the upstream path through a G-PON transmission convergence frame adaptor. Our proposed reach extender is based on the quad-port architecture for cost-effective design and can accommodate both the physical reach of 60 km and the 512 split ratios in a G-PON and the physical reach of 80 km and the 256 split ratios in an E-PON.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.117-126
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• 2014

The COSPAS-SARSAT Search-and-Rescue System detects and locates emergency beacons activated by aircraft, ships and individuals. In particular, when this system is used in wartime and the signal is leaked to the enemy, it can cause the loss of the rescuers and the survivors. This paper proposes an improved method which protects the COSPAS-SARSAT search-and-rescue signal itself from being disclosed during its operation. In addition, there is presented a new protocol which maintains the stabilized security status between survivors and rescuers, using the Galileo/SAR return link.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.91-99
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• 2008

In this paper, we implemented an wireless remote control and monitoring system by using Globalstar satellite modem. This system is composed of the data terminal equipment of Globalstar data communication system using microcontroller, C8051F023, and WGIS(Web-based GIS) user program. We tested the wireless remote control and monitoring system with data terminal equipment and user program how to work properly, and verified that the user could confirm the data from the data terminal equipment, which can provide the status of input/output devices and the information of location with the main and control dialog by GIS(Geographic Information System) program. For data communication of between data terminal equipment and user program, we programed PPP and TCP/IP protocol to communicate with each other. Some GIS tools used in this program are ArcView and MapObject from ESRI to offer various visual mapping information to the user.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.300-305
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• 2017

It is necessary to establish a system suitable for the driving vehicle so that it can effectively search for and modify various data anywhere and anytime by effectively linking communication with the computer system in the running vehicle and to control the equipment properly for smooth operation on a limited platform do. Also, vehicle CAN communication is used to extract system engine information, and data is transmitted using ZigBee for this information transmission. Therefore, OBD-II protocol, which is provided by the vehicle itself, is used for vehicle CAN to obtain vehicle status information and exhaust gas using various sensor information of the vehicle and O2 sensor value, and transmits it to the ZigBee main control system. In this study, we implemented a system that can reduce the battery load damage to the maximum by reducing the power consumption to the maximum, and to monitor the internal state of the vehicle through ZigBee communication with the embedded system for low power vehicles.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.921-924
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• 2007

In this paper, we have implemented a ubiquitous healthcare system that can measure and check human's health in anytime and anywhere. The implemented prototype are composed of both front-end and back-end. The front-end have several groups: environment sensor group such as temperature, humidity, photo, voice sensor, health sensor group such as blood pressure, heart beat, electrocardiogram, spo2 sensor, gateway for wired/wireless communication, and RFlD reader to identify personal. The back-end has a serial forwarder to propagate measurment results, monitor program, and medical information server. The implemented sensor node constructs a sensor network using the Zigbee protocol and is ported the TinyOS. The data gathering base node is linux-based terminal that can transfer a sensed medial data through wireless LAN. And, the medical information server stores the processed medical data and can promptly notify the urgent status to the connected medical team. Through our experiments, we've confirmed the possibility of ubiquitous healthcare system based on sensor network using the Zigbee.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.1005-1018
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• 2017

This paper proposes an App Visualization (AppV) based on IoT Self-diagnosis Micro Control Unit (ISMCU) for accident prevention. It collects a current status of a vehicle through a sensor, visualizes it on a smart phone and prevents vehicles from accident. The AppV consists of 5 components. First, a Sensor Layer (SL) judges noxious gas from a current vehicle and a driver's driving habit by collecting data from various sensors such as an Accelerator Position Sensor, an O2 sensor, an Oil Pressure Sensor, etc. and computing the concentration of the CO collected by a semiconductor gas sensor. Second, a Wireless Sensor Communication Layer (WSCL) supports Zigbee, Wi-Fi, and Bluetooth protocol so that it may transfer the sensor data collected in the SL to ISMCU and the data in the ISMCU to a Mobile. Third, an ISMCU integrates the transferred sensor information and transfers the integrated result to a Mobile. Fourth, a Mobile App Block Programming Tool (MABPT) is an independent App generation tool that changes to visual data just the vehicle information which drivers want from a smart phone. Fifth, an Embedded Module (EM) records the data collected through a Smart Phone real time in a Cloud Server. Therefore, because the AppV checks a vehicle' fault and bad driving habits that are not known from sensors and performs self-diagnosis through a mobile, it can reduce time and cost spending on accidents caused by a vehicle's fault and noxious gas emitted to the outside.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.906-915
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• 2016

In this study, a network monitoring system, including a secure 460-Network and a 460-Gateway, is designed and developed according with the requirements of the IEC (International Electro-Technical Commission) 61162-460 network standard for the safety and security of networks on board ships. At present, internal or external unauthorized access to or malicious attack on a ship's on board systems are possible threats to the safe operation of a ship's network. To secure the ship's network, a 460-Network was designed and implemented by using a 460-Switch, 460-Nodes, and a 460-Gateway that contains firewalls and a DMZ (Demilitarized Zone) with various application servers. In addition, a 460-firewall was used to block all traffic from unauthorized networks. 460-NMS (Network Monitoring System) is a network-monitoring software application that was developed by using an simple network management protocol (SNMP) SharpNet library with the .Net 4.5 framework and a backhand SQLite database management system, which is used to manage network information. 460-NMS receives network information from a 460-Switch by utilizing SNMP, SNMP Trap, and Syslog. 460-NMS monitors the 460-Network load, traffic flow, current network status, network failure, and unknown devices connected to the network. It notifies the network administrator via alarms, notifications, or warnings in case any network problem occurs. Once developed, 460-NMS was tested both in a laboratory environment and for a real ship network that had been installed by the manufacturer and was confirmed to comply with the IEC 61162-460 requirements. Network safety and security issues onboard ships could be solved by designing a secure 460-Network along with a 460-Gateway and by constantly monitoring the 460-Network according to the requirements of the IEC 61162-460 network standard.

• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.65-76
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• 2002

QoS routing is a routing technique for finding feasible path that satisfies QoS requirements required by application programs. Since QoS routing determines such paths in terms of dynamic network state, it satisfies the requirement of applications and increases the utilization of the network. The overhead is, however, generated by routers to exchange the information of the dynamic state of network. In order to reduce this protocol overhead, a timer based update mechanism is proposed in which router checks the change of the network status periodically and network state information is exchanged if the change is greater than a certain value. Using large update period makes, though, routing performance irresponsive to the parameters which determine the update of the network state of the router. In addition to this, large update period may result in inaccurate network state information at routers and cause resource reservation failure. The resource reservation failure generates additional overhead to cancel the resource reservation of the part of the path. In this paper, we propose mechanisms enhancing the existing network state update policy with respect to these two problems. Performance of the proposed schemes are evaluated through a course of simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.369-379
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• 2011

During the routing process between nodes on the CR(Cognitive Radio) network conducting for efficient use of limited frequency resources, spectrum handover process due to the appearance of the PU occupies most of the routing latency, and also decreases the reliability of the path. In this paper, a cooperative routing protocol in a multi-channel environment is proposed. The source node broadcasts a message with available channel lists and probability of PU appearance during its route guidance. The intermediate nodes re-transmit the message, received from the source node, and update and maintain the information, status table of the path. The destination node determines the optimal path and sends a reply message to the selected path after it receives the messages from the intermediate nodes. The average probability of the PU appearance and the average time of the PU appearance are updated while transferring data. During data transmission the channel with the lowest probability of appearance of the PU is selected dynamically and if a PU appears on the current channel partial repairment is performed. It is examined that reliability of the selected path considerably is improved and the routing cost is reduced significantly compared to traditional routing methods.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.6
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• pp.547-553
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• 2019

Presence server should process massive SIP subscription request messages and massive presence event notifications from presence resources in real time. Therefore multiple servers architecture is needed for presence service system. In this paper, an architecture of multiple servers presence service system using SIP based CCMP control messages for lowering presence server load level has been presented. In this system, each presence server exchanges current load status using CCMP control messages, and total system load according to variance of users number and amount of presence resources has been effectively distributed processed. The CCMP control messages has been optimally designed to control presence servers, and exchange procedures of these control messages between presence servers has been also presented and the performance of the proposed multiple servers presence service system has been analysed by experiments. The result shows that average presence subscription processing time reduced from 40.8% to 69.2% and average presence notification processing time reduced from 29.4% to 62.7%.