• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.705-711
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• 2004

We propose novel OCDMA system with the structure of reconfigurable may encoder/decoder(RAE/ RAD), which are able to reallocate the 2-D optical codes to each subscriber and recover the transmitted data at all the receiving nodes. We have first implemented the double hard limiters composed of limiting amplifier(first hard limiter) that maintain a level of the encoded data from receiving node and AND detector(second hard limiter) for detecting the position of the encoded data and recovering the data. With the proposed system, it was successfully implemented to recover a specific channel data out of 16 code-multiplxed channels using FPGA and 4 DFB-LDs having distinct wavelengths. From experimental results, the code length resulted from increasing the number of the simultaneously connected channels has been reduced by using 2-D OCDMA multiplexed in time and wavelength instead of 1-D OCDMA. In addition, bit errors phenomenon on account of deterioration of autocorrelation peak-to-side lobe ratio is enhanced by using the double hard limiters composed of AND detector and limiting amplifiers.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1788-1791
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• 2010

위치 측정 기술의 발달로 인해 다양한 서비스들이 개발 되어 현대 사회에 제공되고 있다. 이러한 서비스들 중 GPS는 현재 우리 사회에 깊숙이 녹아 들어와 핸드폰, 내비게이션, 배송처리, 차량 위치 파악, 긴급구조서비스, 항공 및 선박 항법장치, DSLR 등 다양한 분야에서 활용되고 있다. GPS는 위성신호를 수신하여 위치를 파악하기 때문에 위성신호를 수신할 때 공간상의 제약이 있고, 매우 민감하게 방해요소에 의해 간섭을 받을 수 있다. 차량이 충돌위험 발생시 GPS가 방해요소로 인해 수신되지 않으면 충돌회피를 위한 시스템이 제대로 작동하지 못할 우려가 있다. 본 논문에서는 GPS가 수신율이 떨어지는 터널, 고가도로, 지하주차장과 같은 장소에서의 WLAN을 기반으로 한 위치측정 기술을 이용하여 차량의 충돌회피를 방지하기 위한 프로토콜을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.348-354
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• 2005

These days, Electronic mail is being used in everyday's life. And on the other hand, we are facing spam mails' problems. Spam mails are widely used by means of marketing in e-Commerce. To block these spam mails, we are using filtering or pricing systems. But these solutions are raising other problems such as impediment in reception or availability caused by false positive or payment resistance. To solve these problems, we propose an Indirect Model on Electronic Mail Control System(IMEMCS) which controls an unsolicited electronic mail and prevents an useful electronic mail from discarding. We design and implement the IMEMCS to enhance the usefulness and the availability. Being tested the IMEMCS to verify the usability and the efficiency, it gave us a very successful result.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.10
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• pp.951-963
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• 1991

In this paper M-ary Psk system for digital land mobile radio utilized the raised-cosine filter instead of LPF with rectangular frequency characteristic as luniting channel bandwidth are implemented to measure their performance and effect of ISI and jitter. Also the error probability is calcylated on the condition of fast Rayleihg fading, cochannel interference and AWGN, It is found that QPSK and 8-PSK system with 2-branch diversity, can be improved by 3 or 5 time of spectral effciency respectively, comparinng with one of the non diversity QPSK and 8.PSK system.

• The KIPS Transactions:PartC
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• v.17C no.1
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• pp.37-46
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• 2010

In an IPTV system, the rights of the content and service provider can be protected by using Conditional Access System (CAS) and Digital Right Management (DRM). In case of the CAS, only the authorized user who has structured authentication keys can decrypt the encrypted content. However, since the CAS establishes a secure channel only between content provider and Smart Card (SC), it cannot protect the system against McCormac Hack attack which eavesdrops on unsecure channel between SC and Set-Top Box (STB) and SC cloning attack. In this paper, we propose a robust multi-STB assisted SC / STB authentication protocol which can protect the IPTV system against not only McCormac Hack attack, but also SC cloning attack. The previous works which bind a STB and a SC during the SC registration phase against the SC cloning attack does not support multi-STB environments. The proposed system which dynamically updates the STB information in subscriber management system using the bi-directional channel characteristic of IPTV system can support the user's multi-STB device effectively.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.4
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• pp.31-40
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• 2010

The evolution of internet have opened the world of IPTV. With internet protocol, IPTV broadcasts contents stream. The IP protocol doesn't provide secure service due to IP characteristics. So, it is important to provide both connect and secure service. Conditional Access System and/or Digital Right Management are being used to protect IPTV contents. However, there exist restrictions in the view of security. In this paper, we analyse existing security technologies for IPTV and propose a novel method to enforce security efficiently. In the proposed method, OTP is used for encryption/decryption contents and CAS controls key for encryption/decryption and the right of user. With this scheme, it reduces the load of the system and provides more security.

• Journal of IKEEE
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• v.16 no.1
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• pp.7-14
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• 2012

In this paper, a reception rate of terrestrial digital TV broadcasting service is analyzed and a novel method which can estimate the broadcasting coverage rate more objectively and reliably than the existing method is proposed. Previous method measures the reception rate by means of electric field intensity measurement or subjective video quality assessment. Because of limited measuring points, it inherently has measurement error and cannot consider the viewer's receiving conditions in real-time. In order to consider the viewer's population and receiving environment, morphology which characterizes the viewer's receiving environment is extracted using household census data of National Statistical Office and the land cover map of Ministry of Environment. Using the extracted geographical morphology, the reception rate of terrestrial digital TV broadcasting service is calculated with Spectrum Management Intelligence System (SMIs). Proposed method can calculate the reception rate more objectively and reliably than the existing methods because it fully considers the viewer's receiving environments in real-time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.10
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• pp.2301-2308
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• 2013

These days, Rehabilitation psychology analysis system is being used by world wide web in everyday's life. And on the other hand, we are facing spam messages' problems. To block these spam message, we are using filtering or pricing systems. But these solutions are raising other problems such as impediment in reception or availability caused by false positive or payment resistance. To solve these problems, we propose an Indirect Model on Message Control System(IMMCS) which controls an unsolicited message and prevents an useful message from discarding. We design and implement the IMMCS to enhance the usefulness and the availability. Being tested the IMMCS to verify the usability and the efficiency, it gave us a very successful result.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.898-908
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• 2004

In this paper, we propose a high speed preamble searcher feasible for RACH(Random Access Channel) preamble structure in WCDMA reverse link receiver. Unlike IS-95, WCDMA system uses AISMA(Acquisition Indication Sense Multiple Access) process. Because of the time limit between RACH preamble transmission and AI(Acquisition Indicators), and the restriction on the number of RACH signatures assigned to RACH preamble, fast acquisition indication is required for efficient operation. The preamble searcher proposed in this paper is based on 2-antenna system and has adopted FHT algorithm that has the radix-2 16 point FFT structure. The acquisition speed using FHT is 64 times faster than the conventional method that correlates each signature. Based on their fast aquisition scheme, we improved the acquisition performance by calculating the correlation up to the 4096 chips of the total preamble length. The performance is analyzed by using Neyman-pearson method. The proposed algorithm has been applied for the implementation of WCDMA reverse link receiver modem successfully.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.6
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• pp.173-178
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• 2008

With the discontinuation of analog broadcasting in 2012, the cable broadcasters are investing in the conversion to DCATV (Digital Cable TV). DCATV is providing various broadcast of high quality to audiences through paid broadcasting called PPV (Pay Per View). Such services are using various kinds of CASs (Conditional Access System) in order to verify the viewing rights of subscriber. In addition, to respond to the fast changing environment of digital broadcast, not only simple digitalization of broadcast but also services such as PVR (Personal Video Recorder) and VOD (Video On Demand) are provided to subscribers. Because these additional services have many difficult areas to cover with traditional CAS alone, a new plan has become necessary. With the improvement of related regulations in 2008, the test service of IPTV (Internet Protocol TV) which is a broadcast service through the internet started. Because like DCATV, IPTV also sets the real time broadcast and the VOD service as the basic services, the use of appropriate CAS is required. In this study, the CASs for DCATV and IPTV undergo comparative analysis, and the development direction which will benefit both subscribers and broadcasting companies is suggested.