• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.775-779
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• 1999

This paper presents design of AGC(Automatic Gain Control) and DC offset remover suitable for cable modem which makes use of QAM(Quadrature Amplitude Modulation) scheme. Since QAM has multi-level signal characteristic, for high-order QAM, the constellation is dense and the distance of decision boundary between adjacent symbols is short. So AGC and DC offset remover must be designed optionally for preventing performance degradation. AGC is designed into feedback type and is related to the STR(Symbol Timing Recovery)and Paff interpolation algorithm. Whereas AGC need to perform average power detection during many symbols by comparison with the reference power, DC offset remover uses only the instant polarity decision such that simple implementation can be achieved with good performance. Though the AGC and DC offset remover are simulated here only for 256 QAM scheme for convenience'sake, it can be applied to other multi-level QAM or PSK modulation scheme.

• Journal of Digital Convergence
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• v.13 no.9
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• pp.219-224
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• 2015

The broadcasting communications service will accelerate its development with the convergence of broadcasting media and internet service. In the field of CATV network related technology, only those service providers will be able to survive in future, and they can combine available services in the most effective and economical way. This research aims to explain the CATV status of Korea and China and its technology trends. It also analyzes CMC(Cable Modem Concentrator) technology, suggested as one of the high-speed internet technology. CMC technology has the advantages of enhancing the transmission speed while using the existing basic structure of HFC network and expanding service area by adding amplifiers within CMC. The distance between coaxial cables is getting shorter with more concentrated areas in large cities in Korea. However, in China, the demand for long distance transmission service is increasing. CMC technology satisfies both short and long distance service subscribers without any geographical limitations. With these advantages, CMC technology is expected to generate lots of economic benefits if applied for the CATV network in the area of China, Middle East, and Southeast Asia.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.1-11
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• 2005

S-CDMA is the advanced physical layer modulation techniques of DOCSIS 2.0 specification. S-DMT is another challenging modulation technique for cable modem upstream channel due to the intrinsic robustness for fading and impulse noise. The BER performance of S-DMT and S-CDMA over the mixed channel model of AWGN and impulse noise were evaluated in comparison with TDMA. The mathematical BER derivation and the comparison of those three types of technique were performed based on the ${\varepsilon}-mixture$ non-Gaussian impulse noise model. The results of simulation show good compliance with those of analytic BER derivation. By the results of comparisons, it was verified that the performance of S-CDMA and S-DMT is almost the same, but the performance of S-DMT is far superior to that of TDMA at typical BER range of the practical data communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1803-1811
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• 2001

In this paper, Forward Error Correction(FEC) that is satisfied with ITU-T Recommendation J.83, Annex B(North American Data Over Cable Service Interface Specifications(DOCSIS) for Multimedia Cable Network System(MCNS)) is analyzed. The FEC consist of Reed-Solomon(RS) layer, interleaving layer, randomization layer, and trellis coded modulation(TCM) layer. The effects of quantization of input symbol and of trace-back depth in the Viterbi decoder are simulated over AWGN channels.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.939-942
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• 1998

This paper presents the process on the construction for the remote distribution pole transformer monitoring system. Especially, this system uses CATV cable as communication media which is located in KEPCO's main distribution line. It has four major components such as sensor for measuring secondary voltage and currents of distribution transformer, RF modem for data modulating/de-modulating, communication media for sending/receiving of data, and pc server for monitoring the results of sensing or computing information. This paper also describes the configuration of these each component's configuration and its functions.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.432-441
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• 2006

As the community antenna television (CATV) networks becomes ubiquitous, instead of constructing an entirely new broadband network infrastructure, it has emerged as one of the rapid and economic technologies to interconnecting heterogeneous network to provide broadband access to subscribers. How to support ubiquitous real-time multimedia applications, especially in a heavy traffic environment, becomes a critical issue in modern CATV networks. In this paper, we propose a time guaranteed and efficient upstream minislots allocation algorithm for supporting quality-of-service (QoS) traffic over data over cable service interface specification (DOCSIS) CATV networks to fulfill the needs of realtime interactive services, such as video telephony, video on demand (VOD), distance learning, and so on. The proposed adaptive fast expansion algorithm and the loading statistics with dynamic swapping algorithm have been shown to perform better than that of the multimedia cable network system (MCNS) DOCSIS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.4
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• pp.822-828
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• 2013

In this paper, a multi-modem for process automation of non-destructive inspection (NDI) which possibly generates various kinds of data is implemented and verified. Here, a variety of data such as control signals, text data, image data generated by inspection devices, sensors, computers are transmitted to the multi-modem via serial, Ethernet, and coaxial cable. We exploit a communication network in which powerlines are used as backbone transmission media. Thus, the implemented multi-modem has various ports and corresponding interfaces for data transmission. As a result of practical experiments, the multi-modem maintains almost constant data rate with little waveform distortion. In addition, the experiments confirm that the modem operates normally under extreme variation of temperature. It is, therefore, considered that the multi-modem can contribute significantly to implement powerline communication (PLC)-based process automation for NDI in which various kinds of data are practically generated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.4
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• pp.255-260
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• 1991

A voltage measuring system specified for the voltage fluctuation of the Pusan-Hamada submarine cable is developed by adding circuits of differential amplification and analog-to-digital conversion to a microprocessor-based data logger with a data modem. This system is charaterized by its small size. no power failure. fully unmanned operation. and precise instrumental drift correction. In addition to the cable voltage and current it measures an ambient temperature and a mercury cell voltage in order to calibrate temperature effect and check its long-term stability. The data acquired by this system show that the voltage signal. comprising fast random noises with a constant width of about 0.2V. fluctuates within a range of about 1V and the fluctuation frequency is similar to that of tidal motion. The source voltage of power feeding equipment (PFE) for the cable system seems to be affected when the room temperature changes rapidly.

• Proceedings of the CALSEC Conference
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• 2003.09a
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• pp.8-14
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• 2003

디지털콘텐츠 세상 디지털콘텐츠에 대한 기대 ㆍ멀티미디어 압축 기술 동의 발전 ㆍ인터넷을 통한 멀티미디어 전송 기술 발달 ㆍ광대역 네트워크 및 xDSL, Cable modem과 같은 네트워크 기술 발달 ㆍ이용자의 멀티미디어 기대치 증가 ㆍ디지털 정보의 장점(무한사용, 가공재생, 저장, 비손실성, 접근용이성,...)(중략)

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.257-269
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• 2003

S(Synchrous)-DMT(Discrete Multi Tone) is an emerging cable modem technology applicable to the upstream channel for high speed multimedia communication. In this paper we analyze the transmitting and receiving process of S-DMT scheme and derive bit error probability of S-DMT scheme in the $\varepsilon$-mixture impulse noise model which appropriately reflects impulse noise model which approproately reflects impulse noise characteristics of upstream channel. The analysis results show a good match with the simulation results. We also compare Eb/No gain performance of S-DMT with TDMA in 16-, 32-, 64-QAM.