• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.141-148
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• 2003

This paper presents and compares several techniques that detect the symbol rate of unknown received signal. Symbol rate is detected from the power spectral density of the circuits such as the delay and multiplier circuit, the square law circuit, and analytic signal, etc. As a result of discrete Fourier transform of the output signals of these circuits, a lot of spectral lines and some peaks appear in frequency domain and the position of first peak is corresponding to the symbol rate. If a spectral line on the frequency that is not located in symbol rate is larger than the first peak, the symbol rate is erroneously detected. Thus, the ratio between the value of first peak and the highest side spectral line is used for the measure of the performance of symbol rate detector. For the MPSK modulation, the analytic signal method shows better performance than the delay and multiplier and square law circuits when the received signal power is lager than -20dB. It is also noted that the delay and multiplier circuit is not able to detect the symbol rate for the QAM modulation.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.4
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• pp.29-35
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• 2014

The formula contains up between the text and the structural information, as well as their mathematical symbols. Research on-line or off-line recognition formula is underway actively used in various fields, and various forms of the equation are implemented recognition system. Although many documents are included in the various formulas, it is not easy to enter a formula into the computer. Recognition of the expression is divided into two processes of symbol recognition and structural analysis. After analyzing the location information of each character is specified to recognize the effective area after each symbol, and to the structure analysis based on the proximity between the characters is recognized as an independent single formula. Furthermore, analyzing the relationship between the front and back each time a combination of the position relationship between each symbol, and then to add the symbol which was able to easily update the structure of the entire formula. In this paper, by using a scanner to scan the book formula was used to interpret the meaning of the recognized symbol has a relative size and location information of the expression symbol. An algorithm to remove the formulas for calculation of the number of formula is present at the same time is proposed. Using the proposed algorithms to scan the books in the formula in order to evaluate the performance verification as 100% separation and showed the recognition rate equation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2831-2838
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• 2014

This paper proposes the off-line handwritten flowchart symbol recognition algorithm by type and strength of a cross region of the straight line strokes that is extracted based the normalized dominant slope vectors. In the proposed algorithm, first of all, a connector symbol which consisted only curves is recognized by the special features, and the other symbols with straight line strokes are recognized by type and strength of a cross region, and that is extracted by extension of minimum bounding rectangle of the clusters of the normalized dominant slope vectors, and the straight line strokes of the symbols is extracted by the normalized dominant slope vectors. To confirm the validity of the proposed algorithm, the experiments are conducted for 10 different kinds of flowchart symbols that mainly used for computer program, and the number of symbols is 198. Experiment results were obtained the recognition rate of 99.5%, and the flowchart symbols is recognized correctly robust to variations, and then the proposed algorithm were found very effective for off-line handwritten flowchart symbol recognition.

• Journal of electromagnetic engineering and science
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• v.4 no.2
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• pp.63-67
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• 2004

DAM(Delay-And-Multiplier) intercept receiver usually detects the symbol rate of the transmitted DS spread spectrum signal for the feature extraction. It is important for secure communication to reduce the normalized output signal-to-noise ratio that is generated at the DAM intercept receiver as a measure of detectability. In this paper, several kinds of chip waveforms are novelly analyzed for LPI(Low-Probability of Intercept) communication against DAM intercept receiver. Consequently, it is shown that the rectangular chip waveform shows the best LPI performance in the bandwidth of 2/$T_c$TEX>, 4/$T_c$TEX>, and 6/$T_c$TEX>/. Except the rectangular waveform, kaiser chip waveform show better LPI performance than the other waveforms in the bandwidth of 4/$T_c$TEX> and 6/$T_c$TEX>.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.594-599
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• 2001

The symbol rate which is the main feature of NRZ information signal is detected by DAM (Delay-And-Multiplier) receiver. It is important for secure communication to reduce the normalized output SNR which is calculated at the DAM output as a measure of detectability. In this paper, we use the signal which is modulated by the class of MSK modulation schemes as the input signal of the DAM receiver for analyzing LPI performance and the GMSK(BT=0.3) used in GSM system is highlighted. Consequently, GMSK which has better bandwidth efficiency than other modulation schemes(BPSK, QPSK, OQPSK, and MSK) has better LPI performance compared with other ones. To compare the performances of each modulation scheme fairly, the transmitted powers of each system are set to be same within useful bandwidth.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1793-1802
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• 2000

In this paper we propose an efficient implementation technique for cyclic extension in VDSL(Very High bit-rate Digital Subscriber Line) systems using Zipper duplexing and analyze its performances under typical telephone channel environments. In Zipper-based VDSL systems each DTM(discrete-multitone) block is appended by both cyclic prefix(CP) and cyclic suffix(CS). The CP is inserte to prevent both intersymbol interference (ISI) and iterchannel interference (ICI) while the CS is appended to ensure orthogonality between the upstream and downstream carriers thus preventing near-end crosstalk (NEXT). However in order to implement the CP in the transmitter side of the VDSL system an additional hardware is required to append the latter part of each DMT symbol to the beginning of the DMT symbol. In this paper we propose a VDSL system with Zipper duplexing using only CS to reduce hardware complexity (memory and processing delay) required for implementation of CP. It is shown by computer simulation that the proposed approach has the same capacity under typical channel environments as the previous Zipper-based VDSL system using both CP and CS. even with a significantly lower hardware complexity.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.887-890
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• 2003

High Speed data transmission over a long length of cable is limited due to the limited bandwidth of a cable which introduces ISI(Inter Symbol Interference). In order to compensate for the loss and phase dispersion in the cable, a pulse shaping in a transmitter and a line equalizer in receiver can be used. This paper presents a low-power and small-ana analog adaptive pulse shaping circuit and line equalizer, The design was fabricated in a 0.25${\mu}{\textrm}{m}$ mixed-signal CMOS process. The proposed pulse shaping circuit and equalizer operate at 400Mb/s on 50m STP(Shielded Twisted Pair) cable. It consumes 28.5${\mu}{\textrm}{m}$ with a 2.5-V power supply and occupies only 0.098 $\textrm{mm}^2$.

• Journal of Advanced Navigation Technology
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• v.16 no.3
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• pp.426-432
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• 2012

In this paper, we investigate the signal to noise ratio (SNR) estimation performance of Cross quadrature amplitude modulation (QAM), which is being used for asymmetric digital subscriber line (ADSL), very high bit rate digital subscriber line (VDSL), and digital video broadcasting - cable (DVB-C), and has been found to be useful in adaptive modulation and blind equalization. At first, the symbol error rate (SER) performance of Cross QAM is analyzed in Rayleigh fading channel. Then we suggest error vector magnitude (EVM) based SNR estimation utilizing the selected constellation points having different types of decision region from one another, and verify that SNR estimation performance of each points have different performance pattern through simulation. From the simulation results, it has been found that when suggested selected constellation points are used for SNR estimation in Cross QAM, estimation performance is enhanced in additive white Gaussian noise (AWGN) channel or Ricean fading channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.687-694
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• 1999

In this paper, to draw out the parameter of synchronization for ADSL(Asymmetric Digital Subscriber Line) chip design, we analyze the performance of STR(Symbol Timing Recovery) and frame synchronization with computer simulation. We analyze and design PLL(Phase Lock Loop) loop for ADSL. As a result, we obtained the optimum parameter of STR to design ADSL chip. Also, when performed frame synchronization with several algorithm, we analyzed the performance of FER(Frame Error Rate) and the effect of frame offset with computer simulation.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.29-39
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• 1993

For an economical or timely reason, the types of subscriber loops for ISDN basic rate access service will, at least initially, be that of the pre-existing telephone network, that is, 2-wire twisted-pair metallic cable. Therefore, it is important to assess the high-speed digital transmission capability of the 2-wire subscriber loops. In this paper, the impairments such as intersymbol interference, crosstalk, and impulse niose are modeled. And then, symbol error probabilities in terms of SNR in DSL system using ECH and 2B1Q line code are analytically derived and numerically calculated. Also, the relationship between the quality of service required in ISDN subscriber section and the loop parameters is investigated.