• Journal of Korea Society of Industrial Information Systems
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• v.23 no.6
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• pp.59-66
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• 2018

In this paper, we experimented how long distance voice communication is possible After implemented PTT(Push to talk) Bi-directional radio using open source project Codec 2, which is a low speed voice codec for digital amateur radio and 900MHz FSK transceiver. In case of a general digital radio, the AMBE+2 codec, which is regarded as an industry standard in terms of performance, is expensive and has the monopoly of technology. Using the 400MHz band in terms of frequency, narrow bandwidth of DMR(12.5kHz) and DPMR(6.25kHz) is used, so the data rate is low. In the 900MHz bandwidth can be extended, which is advantageous in terms of data transmission. As a result of the voice quality and distance field test, we could find that the communication takes place within about 500m. In this paper, only voice communication is reviewed. if a review of data transmission such as a simple image is added, this solution can be used in various fields as a low cost IOT radio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.885-894
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• 2015

In this paper, it can be applied to a walkie-talkie, the RFID / USN 920 MHz band(917~923.5 MHz) and WiFi 2.4GHz band(2.4~2.483 5GHz) return loss is 10 dB over the band, on-board dual band with omni-directional radiation characteristics is proposed. The basic structure designed antenna is used meander monopole antenna. It was used as double stubs and tabs for antenna designs that meet the criteria proposed. The double stub and the tab affects the reactance of the antenna to form a common-mode and differential-mode in the stub to improve the antenna characteristics and return loss in the bandwidth, gain and radiation characteristics. The system size of walkie-talkie is $52{\times}77mm^2$, the size of the antenna is limited to $52{\times}15mm^2$, the thickness of FR4 dielectric substrate is 0.8 mm, FR4 dielectric constant 4.4 is used. For experimental results, the return loss is measured more than 10 dB, the maximum gain is measured 1.95 dB, the maximum bandwidth is measured 360 MHz, the radiation characteristic is measured omni-directional. By a walkie-talkie terminal design applying the results of the paper, the handset's price competitiveness and production efficiency can be improved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.417-418
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• 2010

• Defense and Technology
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• no.2 s.144
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• pp.67-69
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• 1991

세계청년축제를 보도하려는 언론인들은 자신들의 다주파 무전기를 보유할수 없었으며, 그들은 북한 주민들의 라디오는 정부 방송만 수신하게 되어 있다는 것을 알았다. 어떤 사람들은 북한에 불리한 보도는 하지 않도록 주의를 받기도 하였다. 최근 가장 논란이 많은 것은 워싱톤에 위치한 Asia Watch의 주장으로, 북한에는 인구의 0.7%인 15만2천명에 달하는 정치범이 있다고 전하고 있다

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.6
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• pp.752-761
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• 2016

Tactical Multiband Multirole radio(TMMR) has been developed and under some official testings now. Our army wants TMMR to be installed in Ground Fighting Vehicles(GFVs) and be incorporated with their Battlefield Management System(BMS). Also, BMS with TMMR should communicate with BMS on FM radio which is currently under use in most of GFVs. To achieve such goals, some significant changes should be made into the present BMS and in this paper, several considerations will be presented in the both sides of hardware and software point of view.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2385-2390
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• 2010

The PRC-999K radio widely used in Korean Army is half-duplex and also has the broadcasting radio wave character that all subscribers listen when one subscriber speaks in time. The radio data communication system configures a 1:1 unicast network between a command post and network members in a military fire control system. The system also applies CSMA/CA technique to avoid data collision and additionally applies SDLC protocol for efficiency and fast communication. This paper shows that allocating address to network members in serial order can reduce data transmitting/receiving time, and thereby a command post needs to broadcast data only one time and the assigned members can reply in order without data collision. It is validated through an experimental test.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.17-22
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• 2013

Heterogeneous radios are used in disaster management agencies for a variety of reasons though the radio must have the same radio frequency and protocol for voice communication. For this reason, the variety of heterogeneous radio voice connection methods have been studied but these are simple analog voice line cross connection or partial networked based on digitalization. In this paper, we suggest the method of voice packet transmission method based on All-IP per radio through IP network using SIP/RTP for scalability and openness and developed a prototype of the proposed method was verified.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.3
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• pp.431-440
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• 2017

HF communications are used as a last means of long distance communications without any relay node in NLOS (Non Line-Of-Sight) environment. Conventional analog voice communication in the HF band is vulnerable to security as well as severe background noise. To overcome these shortcoming, digital voice was introduced into HF radios in the early 1980s. In this paper, we analyze avaliable digital voice communication ground wave range of HF radios that applied MELPe CODEC and MIL-STD-188-110B physical layer standard using GRWAVE program. And we evaluate usefulness of digital voice communication in HF band.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.531-534
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• 2010

Currently the functionality of the PRC-999K radio that is widely used in Korean Army is half-duplex and the broadcasting system that all subscribers have to listen when one subscriber speaks in time. Radio data communication system configures peer-to-peer network between command post and network members in military fire control system. And the system applies CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance) technique to avoid data collision. Such a data transmitting/receiving time could be reduced by allocating address in serial order to each network members. By doing that, command post need to broadcast data only one time and assigned members will reply in order without data collision. This paper provides such a protocol and algorithm.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.310-312
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• 2014

현재 대구시 소방관들은 소화전, 위험물들의 위치가 모바일 어플리케이션화 되어있지 않다. 이로 인해 관리 및 화재시 현장에 나갈 때 바로 검색할 수 없기 때문에 어려움을 겪고 있다. 본 논문에서는 소화전과 위험물의 모든 정보를 제공하는 모바일 어플리케이션을 통하여 언제 어디서나 소화전과 위험물의 위치와 정보에 접근할 수 있게 하였다. 이와 함께 현재 소방대원들이 사용하는 무전기외 간섭, 끊김, 차단등과 같은 문제점을 개선하기 위하여 기존의 무전기가 사용하던 주파수대역보다 안정되고 좋은 품질의 Wi-FI 통신망을 이용하여 높은 통화품질의 모바일 단말기 기반의 무전통신 서비스를 제공한다.