• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1873-1878
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• 2017

Recently, many researches have been conducted on the aviation industry to replace the wire harness cable between the avionics of the aircraft with the wireless network. In this paper, we present an Event-Based Simulator for Wireless Avionics Intra-Communications (ES-WAIC) that can verify core technologies of wireless networks and efficiently integrate different layers of the network. ES-WAIC is developed to enhance the readability between the real time control application developers of the higher layer and the network layer developers. Specifically, the practical implement relies on an event-based programming concept to increase portability and compatibility that can be applied to the realistic low-power wireless embedded networks. ES-WAIC implements the overall system layers including the wireless channel modeling of the 4.4GHz band, the physical layer, the medium access control, the network, and the application layer of wireless avionics intra-communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1138-1147
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• 2012

IEEE standard 802.16, often referred to as WiMAX, is considered a "last mile" broadband wireless access alternative to conventional DSL and Cable Internet. One extension that is recently receiving great attention is the IEEE 802.16j Mobile Multihop Relay (MMR) amendment. The focus of this amendment is the development of simple and lower cost relay stations (RSs) that can enhance network coverage and capacity. We use our proposed simple scheduling scheme for serving the SSs in a fair manner and evaluate the performance of WiMAX networks with relays, especially we analyze the impact of interference between RSs on cell throughput Through simulations and numerical analysis, we make several fundamental observations about interference aware cost effective coverage extension in such networks.

• Journal of Broadcast Engineering
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• v.2 no.2
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• pp.182-193
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• 1997

In this paper, we propose technical and structural solutions for various problems in two-way digital communication services in CATV networks by actual field tests. The two-way digital communication services include VOD, video conferencing, distance learning, interactive game and internet service. We investigate the quality of T -1 level 0.544 Mbps) upstream digital signal while varying the number of subscribers in three different cells in accordance with ITU-T G.821. Based on this investigation, several ways to cope with the problems identified are suggested.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.115-122
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• 2008

Mostly used sensors have wired powering and two-way cable systems. It is difficult to employ wired sensor network in ubiquitous era because of a number of sensors and cables. Therefore, sensor networks move from wired systems to wireless systems for the future. However, the power source is a critical obstacle for wireless sensornodes. This research represents the new power source which supplies energy sensor node, maintains over 10 years, and thus replaces batteries with limit of lifetime. The system with piezo materials scavenges extra energies such as vibration and acceleration from the environment. Then it converts the scavenged mechanical energy to electrical energy for powering a sensor, a controller and a circuit for regulating voltage and transmitting sensor value. This study explains the properties of piezo material through theoretical analysis and experiments, and demonstrates powering sensor and transmitting data with stored energy (35mJ) for 14 sec. The developed system provides a solution to overcome the critical problem of making up wireless sensor networks.

• Convergence Security Journal
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• v.8 no.4
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• pp.51-56
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• 2008

A combination of VPNs and dial-up access, such as DSL and Cable, usually provides the cost-effective solution as the substitution of private networks on high-cost leased line. The business demand for high availability has increased with VPN spreading. This paper presents the schemes for a high availability of network access and a load balancing of network traffic in VPN gateways by using multiple links or multihoming capability based on active-active approach. The high availability and load balancing of network links can be achieved by duplicating external network access into multiple independent links. This can provide a continuous network connection to internal users even if one of the links is failed. Moreover, it can provide twice network bandwidth by distributing the traffic into the links. Static and dynamic algorithms are proposed as the load balancing algorithms.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.797-800
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• 2011

The objective of MPEG Media Transport (MMT), which is on going standard, is to develop efficient delivery of media over packet based networks in an adaptive, progressive, download/streaming fashion over various IP based networks, including terrestrial, satellite and cable broadcast networks. In this paper we introduce utilization of signal strength information based on Cross Layer Design(CLD) to efficient multimedia delivery over wireless network in which in practice the wireless conditions can vary significantly. Many recent studies have shown that a significant improvement in wireless video throughput can be achieved by utilizing signal strength information on CLD [1][2]. Despite of its usefulness, however, it was difficult to employ signal strength information in rate adaptation applications due to different representation of signal strength information for each underlying wireless network. To that end, we proposed syntax and semantics of signal strength information in such a way that the information can be interpreted in the unified way. The proposed signal strength information was proposed for the MMT standardization.

• Journal of Korea Technology Innovation Society
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• v.7 no.2
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• pp.459-479
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• 2004

As the high-speed internet access market steadily nears its maturity phase, growth is quickly tapering off and competition, intensifying. As a result telecommunications companies are at present faced with the urgent need to evolve away from a growth model based on continuous acquisition of new subscribers. The recent convergence of telecommunication and broadcasting has come about precisely at this transitional period in the telecommunications market, and is perceived by the industry both as a new business opportunity and as a threat. TV-based VOD(Video on Demand), for one, is able to attract new customers desiring multimedia services of superior quality and to lock-in existing customers. Meanwhile, the latest evolution in network development is brightening the market prospect for TV-based VOD. The service has now hit the market, deployed over VDSL networks - a next-generation high-speed internet - and advanced cable modem networks, delivering high-definition DVD-quality videos. TV-based VOD is a service whose deployment is closely linked to the evolution of subscriber networks. According to the forecast produced by the present study, based on the forecast on the post-ADSL market and a survey conducted on VOD, as post-ADSL subscribers increase from 1.53 million in 2003 to 4.44 million in 2004, and 9.87 million in 2006, the percentage of post-ADSL subscribers with intention to also subscribe to a VOD service is expected to rise from 16% to 34% in 2006. Accordingly, VOD subscribers are estimated to increase from 0.24 million in 2003 to 0.98 million in 2004 and to 3.35 million in 2006.

• Journal of KIISE:Information Networking
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• v.33 no.3
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• pp.277-287
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• 2006

Most of the existing broadband access networks based on DSL, cable modem, and Ethernet support the best-effort internet access service, and adopt the flat rate pricing mechanism. It is almost impossible to provide the differentiated communication services, in current broadband access networks, for the different users and/or the different application services. Currently, however, the advances in multimedia, communication, and security technologies push the interactive and/or streaming multimedia services and VPN services to be widely deployed over Internet, and they require more QoS-sensitive services than the best-effort service. Though various QoS technologies such as RSVP-based IntServ and DiffSern were already developed and under standardization in Internet world, it is impractical to replace the existing QoS-unaware access networks with the QoS-enabled ones at a time to deploy QoS-sensitive services. In this paper, after analyzing current broadband access network architectures and the status of QoS support, we propose a practical approach to support multimedia QoS in the broadband access networks. The approach will be based on the integration of the differentiated pricing and the DiffServ technology. And it will be a step-wise approach to support backward compatibility with the legacy broadband access networks as much as possible.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.461-471
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• 2004

Recently, subscribers have strong desire to get QoS based personalized services in high-speed Internet access. Service providers have been rapidly replacing ADSL, cable broadband access networks with Metro-Ethernet based VDSL. But, it is difficult for Motto-Ethernet based broadband access networks to provide QoS based personalized services, because already deployed network elements cannot distinguish subscribers by specific traffic characteristics. In this paper, when the access network has tree topology, we show that it is possible to provide QoS for each downstream flow with only per flow traffic shaping at the edge node without QoS functions in access networks. In order to show that our suggested scheduling algorithm at the edge node can support the assured service in tree topology access networks, we evaluated its performance by simulation. The suggested scheduling algorithm can shape per-flow traffic based on the maximum bandwidth, and guarantees minimum bandwidth per flow by modifying the DRR scheduler. Simulation results show that congestion and loss in the access network elements are greatly reduced, TCP performance is highly enhanced and loss for assured CBR service flows is reduced by only shaping per-flow traffic at the edge node using our proposed scheduling algorithm.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.140-145
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• 2001

In order to apply for silane crosslinking process to PTC products, especially. self-regulating heater, silane crosslinked samples were compared with radiation crosslinked sample in terms of PTC characteristic and PTC stability. Silane crosslinked samples have lower PTC intensity than radiation crosslinked sample. It can be explained that multiple networks of silane crosslink restrict the movement of molecules in the composite as the sample is heating. As a result of heat cycles at $140^{\circ}C$, the changes of volume resistivity and PTC intensity for radiation crosslinked sample were higher than those of silane crosslinked samples. Whereas, in the case of heat cycles at $85^{\circ}C$, which is limiting temperature for self-regulating heater, both silane and radiation crosslinked samples show stable results without pronounce changes of resistivity up to five cycles.