• Information and Communications Magazine
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• v.26 no.5
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• pp.30-35
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• 2009

본고에서는 무선 가시광 통신을 위한 Medium Access Control (MAC) 프로토콜의 설계에 관해 기술한다. 조명등을 이용한 가시광 무선랜 네트워크는 고정된 상태의 Access Point (AP)에 의한 인프라를 Mobile Node (MN)를 상대로 구성하고 인터넷과 같은 기존의 인프라와 연결되는 구조적 특징을 가진다. 이러한 네트워크에 사용되는 무선 가시광 통신 채널의 특성을 이해하고 MAC프로토콜의 기능에 대한 요구조건을 도출하였다. 주어진 가시광 통신 채널을 효율적으로 사용할 수 있도록 시 분할다중 접속 방식과Full duplex를 도입하는 Frame 구조를 구성하였고 가시성을 이용한 접속 절차를 제안하였다.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.68.2-68
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• 2002

The purpose of this paper is to monitor ECU's self-diagnostic signal without wire. In order to measure the ECU's self-diagnostic signal, the interfaced circuit is developed to communicate ECU with a designed display terminal according to the ISO, SAE regulation of communication protocol standard. An 80C196KC processor is used for communicating ECU's self-diagnostic signal and communication data are sent to PDA monitoring system that is based on the Windows CE. Software on PDA is developed to monitor the ECU's self-diagnostic signal in which RS232 port is programmed by half duplex method. The algorithms for measuring the ECU's self-diagnostic signals are verified to mo...

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.73-75
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• 2010

Current communication and broadcasting services are moved to integrated convergence service. So IPTV(Internet Protocol based TeleVision) services are growth rapidly. Traditional TV were provide simplex service. but IPTV will provide duplex service that is possible of interaction with TV and audience. Therefore current researches are focusing the Social TV service. at this point, we see the trend of Social TV system for research and implementation.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.519-523
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• 2003

This paper describes the communication system of sequencing sorter. Generally sequencing sorter is a machine that sorts mails by delivery order. And designed sequencing sorter is composed of 5 physical modules. So, it is necessary to communicate with each module and to control this communication. A computer called Machine Management Computer, controls this. This paper is about the communication system with MMC and module controllers. This is PC-based, asynchronous full-duplex 4-wire serial systems. 3 protocol layers are presented and stop-and-wait flow control is adopted. Because designed sequencing sorter has to be operated high speed about 27,000 letters per hour, we analyzed the network traffic in the worst case. So, we could find that the communication system has to use above 115,200bps speed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.7
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• pp.26-40
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• 2010

We propose a new routing protocol, MCQosR, that is based on bandwidth estimation, admission control, and a routing metric, MCCR - suitable for wireless ad-hoc networks with multiple radios and channels. To use the full capacity of a wireless link, we assume a node with multiple radios for full duplex operation, and a radio using multiple channels to exclude route-intra interference. This makes it possible to use the capacity of a wireless link. Then, to provide bandwidth and delay guarantee, we have a radio with a fixed channel for layer-3 data reception at each node, used to estimate the available bandwidth and expected delay of a wireless link. Based on the estimate of available bandwidth and delay, we apply the call admission control to a new call requiring bandwidth and delay guarantee. New calls with traffic that will overflow link or network capacity are rejected so the accepted calls can use the required bandwidth and delay. Finally, we propose a routing metric, MCCR, which considers the channel contentions and collisions of a wireless link operating in CSMA/CA. MCCR is useful for finding a route with less traffic and distributing traffic over the network to prevent network congestion as much as possible. The simulation of the MCQosR protocol and the MCCR metric shows traffic is distributed and guaranteed service is provided for accepted calls.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.3
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• pp.239-246
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• 2013

The IEEE 802.15.4 offers standard about PHY and MAC layer and features low power, low bandwidth, and low speed data communication. Because of this reason, IEEE 802.15.4 is only within a limited range such as sensor detection and home network; nevertheless, the research about transmission multimedia data like voice packet through wireless sensor networks is conducted widely. In this paper, we proposed the group communication system based on the sensor network. TDMA/TDD MAC based on the IEEE 802.15.4 PHY for voice communication on the sensor network is designed by improvement existing peer-to-peer voice communication on the sensor network and hardware is implemented for group communication. To measure the quality of designed system, mean opinion score (MOS) is obtained from the experiment and verified by using sine wave method. As a result of an experiment, we expect that a many cases of application solution can be developed using presented system.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.157-162
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• 2010

In this paper, We propose that the adaptive cooperative relay transmission technique using closed-loop MIMO scheme for duplex communication system. As the mobility between relay and base station is little, closed-loop MIMO is better diversity gain than open-loop MIMO. At this time, more than one relaying terminals are included in one cooperative group to share their transmission and take precoding weight feedback. For minimization of throughput reduction caused by increasing feedback bits, we use codebook-based MRT that limit the number of feedback bits. Among the cooperative relay group, the best relays are selected from the base stataion and get the feedback. A protocol senarios are also proposed for this relay system.

• Journal of Digital Contents Society
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• v.7 no.3
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• pp.161-168
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• 2006

Wibro(Wibro - Wireless Broadband Internet ) is a system that can accept effectively the IP-based Wireless data traffic with upward / downward asymmetric transfer characteristic by using a Wirelss broadband transfer technology in OFDMA/TDD (Orthogonal frequency Division Multiple Access/Time Division Duplex). Wibro service should support handover to maintain connection continuously in movement because the service is based on If system which is different from cellular system. Current Micro Mobility system and general Mobile If system has got a problem of delayed speed and lost packets during handover. IETF protocol has been proposed for minimizing this problem and its standardization is under process, mainly focused on Mip4, Mip6 and Mipshop WG. This article studies and analyzes an effective method of minimizing handover delay to improve the problem of WiBro system and its revitalization & outlook.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.921-929
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• 2010

Group communication that involves the setup of a list of users has been a topic of interest in mobile industry. Push to Talk over Cellular (PoC), a group communication service for cellular phone network, is a type of half duplex communications that allows a single person to reach an active talk group without making several calls, but a single button press. Based on this service, we build a new protocol called Push to Talk over Mobile Wimax that uses group communication service in 802.16e network. Also, weper formed simulation to verify and evaluate performance of the designed service in Mobile Wimax network. From the results of performance evaluation, network administrators can evaluate the stability of network and make a better of network's shortcoming and have decision to build the robust network.

• Hip & pelvis
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• v.36 no.2
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• pp.108-119
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• 2024

Purpose: The incidence of deep vein thrombosis (DVT) following total hip arthroplasty (THA) without chemoprophylaxis could be as high as 50% in Caucasians. However, according to several subsequent studies, the incidence of venous thromboembolic events (VTE) in Asians was much lower. The routine use of chemoprophylaxis, which could potentially cause increased bleeding, infection, and wound complications, has been questioned in low-incidence populations. The objective of this study is to determine the incidence of VTE after primary THA without chemoprophylaxis in an Asian population using a fast-track rehabilitation protocol and to verify the safety profile for use of 'mechanical prophylaxis alone' in patients with standard risk of VTE. Materials and Methods: This is a retrospective cohort study of 542 Hong Kong Chinese patients who underwent primary THA without chemoprophylaxis. All patients received intermittent pneumatic compression and graduated compression stockings as mechanical prophylaxis. Multimodal pain management was applied in order to facilitate early mobilisation. Routine duplex ultrasonography was performed between the fourth and seventh postoperative day for detection of proximal DVT. Results: All patients were Chinese (mean age, 63.0±11.9 years). Six patients developed proximal DVT (incidence rate, 1.1%). None of the patients had symptomatic or fatal pulmonary embolism. Conclusion: The incidence of VTE after primary THA without chemical prophylaxis can be low in Asian populations when following a fast-track rehabilitation protocol. Mechanical prophylaxis alone can be regarded as a reasonably safe practice in terms of a balanced benefit-to-risk ratio for Asian patients with standard risk of VTE.