• Title/Summary/Keyword: Telephone channel

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A Study on the Improvement of Isolated Word Recognition for Telephone Speech (전화음성의 격리단어인식 개선에 관한 연구)

  • Do, Sam-Joo;Un, Chong-Kwan
    • The Journal of the Acoustical Society of Korea
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    • v.9 no.4
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    • pp.66-76
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    • 1990
  • In this work, the effect of noise and distortion of a telephone channel on the speech recognition is studied, and methods to improve the recognition rate are proposed. Computer simulation is done using the 100-word test data whichwere made by pronouncing ten times 100-phonetically balanced Korean isolated words in a speaker dependent mode. First, a spectral subtraction method is suggested to improve the noisy speech recognition. Then, the effect of bandwidth limiting and channel distortion is studied. It has been found that bandwidth limiting and amplitude distortion lower the recognition rate significantly, but phase distortion affects little. To reduce the channel effect, we modify the reference pattern according to some training data. When both channel noise and distortion exist, the recognition rate without the proposed method is merely 7.7~26.4%, but the recognition rate with the proposed method is drastically increased to 76.2~92.3%.

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Determination of Channel Capacity Bounds of Narrow Band ISDN Subscriber Line in the Presence of Impulsive Noise (임펼스성 잡음이 있을때 협대역 ISDN 가입자 전송로의 통신로 용량 한계 결정)

  • Lee, Jong-Heon;Sung, Tae-Kyung;Chin, Yong-Ohk
    • Proceedings of the KIEE Conference
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    • 1987.07b
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    • pp.854-858
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    • 1987
  • This paper considers impulsive noise which produce burst error in high speed(approx.160Kbps) data transmission like ISDN(Integrated Servise Digital Network) using PSTN(Public Switching Telephone Network). To begin with, we obtains the transfer function of subscriber line to calculate the variation of bandwidth when the gain of receiver is fixed and channel capacity of non-gaussian channel in upper-and lower bound, and evaluates the transmission capability. In this paper compares channel capacity bounds which obtains when probability density function of impulsive noise is Laplacian distribution function with impulsive noise generated by waveform synthesier.

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On new channel estimation method (새로운 채널 추정방법에 관한 연구)

  • 송석일;한영열
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.23 no.9A
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    • pp.2240-2247
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    • 1998
  • This paper presents a new method for channel impulse response measurment with a suitably designed binary sounding sequence. This method results in ideal channel estimation using three correlators instead of one. This system complexity can be easily overcome by the present technologies. The class of sounding sequences used in this method are the training sequence for channel impulse response measurment with the zero values of autocorrelation function at all shifts except zero and middle shifts in digital cellular mobile telephone system based on GSM. Computer searches are carried out to find the suitable sounding sequences.

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Manufacturing and its Performance of the Underwater Wireless Telephone Using Single Side Band Modulation (단측파대 변조방식의 수중 무선 전화기 제작 및 성능)

  • 윤종락;박규칠;박문갑;김석재;노용주
    • The Journal of the Acoustical Society of Korea
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    • v.23 no.2
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    • pp.134-145
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    • 2004
  • The study aims to develop the underwater wireless telephone system. The system is designed based on the underwater acoustic communication channel parameters such as ambient noise, multipath effect and diver breathing noise. The system adopts SSB modem and its carrier frequency is about 33 kHz in which ambient noise level is low and therefore a high S/N ratio is easily obtained. The source level of the transmitter is designed as 131 dB re 1μPa. Its intelligibility index of sentence shows as 80% or mure in the range of less than 300m in the sea trial.

Quitline Activity in the Republic of Korea

  • Yun, E Hwa;Lim, Min Kyung;Oh, Jin-Kyoung;Ki, In Ha;Shin, Sang-Hwa;Jeong, Bo Yoon
    • Asian Pacific Journal of Cancer Prevention
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    • v.17 no.sup2
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    • pp.1-5
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    • 2016
  • To reduce tobacco use and related harm in Korea, telephone based cessation services (Quitlines) began full operation to provide regular behavioral counseling for smoking cessation in 2006. After registration in the cessation program, at least 21 calls per year are given to each client to help quit and encourage maintenance. Tailored programs for males, females, and adolescent smokers have been offered taking into account smokers' characteristics and smoking behavior. Mailing self-help quit packs and e-mail and SMS services are allowable as additional services.A total of 23,201 smokers were registered on the Quitline program from 2006 to 2014. In 2014, an average of 13,343 calls per month have been received by 28 coaches, the 1 year abstinence rate of clients is 26%, and clients' satisfaction rate is 81.6%. After introduction of the call system in 2007, client convenience and effective operations have been achieved with high technology support of a computer-based telephone system. Systematic education and evaluation programs for quit coaches have contributed to quality assurance of the services. Currently, research into development of new programs and evaluation of Quitline performance is being undertaken. A Comprehensive Multi-channel Cessation Center (CMCC) has been suggested and is now planned as a next step in the national program for smoking cessation.

Isolated-Word Speech Recognition in Telephone Environment Using Perceptual Auditory Characteristic (인지적 청각 특성을 이용한 고립 단어 전화 음성 인식)

  • Choi, Hyung-Ki;Park, Ki-Young;Kim, Chong-Kyo
    • Journal of the Institute of Electronics Engineers of Korea TE
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    • v.39 no.2
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    • pp.60-65
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    • 2002
  • In this paper, we propose GFCC(gammatone filter frequency cepstrum coefficient) parameter which was based on the auditory characteristic for accomplishing better speech recognition rate. And it is performed the experiment of speech recognition for isolated word acquired from telephone network. For the purpose of comparing GFCC parameter with other parameter, the experiment of speech recognition are carried out using MFCC and LPCC parameter. Also, for each parameter, we are implemented CMS(cepstral mean subtraction)which was applied or not in order to compensate channel distortion in telephone network. Accordingly, we found that the recognition rate using GFCC parameter is better than other parameter in the experimental result.

Field Trial of the Korean-Made 45Mb/s Optical Fiber Communication System (45Mb/s 국산 광직유 통신 시스템의 현장 시험)

  • 강민호;이용택;이상호;이만섭;유강희;박희갑;이성은;추흥로
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.32 no.2
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    • pp.50-58
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    • 1983
  • In this paper, a field trial of the Korean-made optical fiber communication system is described. This system was installed between Gu-Ro and Ann-Yang telephone offices on November 1981, and carries a 44.7Mb/s NRZ signal(672 voice channel equivalent). For this trial, optical fiber cable, optical terminal equipment, optical repeater, fusion splicer and measurement equipment have been developed. Employing graded index optical fiber at a wave length of $0.85\;\mu\textrm{m}$, average optical attenuation and splicing losses of 3.6 dB/km and 0.4 dB, resectively, were realized. With link margins of 8~20dB and bit error rate of less than $10^{-10}$, this system has been carrying live traffic between Seoul and Ann Yang telephone offices.

A Study on the Per-Channel CPCM Method by means of the 1-Bit Interpolation (1-Bit Interpolation을 이용한 Per-Channel CPCM부호화방식에 관한 연구)

  • 정해원;조성준
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.7 no.2
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    • pp.47-54
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    • 1982
  • In this paper, a improved per-channel PCM Coder with 1-bit interpolation is proposed. The coder converts a telephone signal to 15-segments u-law PCM signal of a large dynamic range. The A/D conversion technique of the proposed converter requires a feedback loop around a quantizer operates at high speed, and a accumulater for accumulating the quantized values to provide PCM outputs. To obtain both linear and compressed PCM signals a improved table look-up method is presented. The operations of the proposed converter are certified through the experiments to be good. The experimental circuit comprises TTL logic gates, a resistive D/Z converter and a simple differential amplifier. From the results of the experiments, it is known that the proposed converter has many advantage to be adopted economically for per-channel onverter used in rural area service.

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Implementation of echo canceller for mobile communications interworking switch network (스위치네트워크와 연동에 의한 이동통신용 반향제거장치 구현)

  • 오돈성;이두수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.8
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    • pp.2033-2042
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    • 1996
  • In this papre, we describe a recently implemented echo canceller for digital cellular communication of Code Division Multiple Access(CDMA) that features time sharing of digital signal processor(DSP) over four channels in one DSP to reduce per channel costs. In the Public Land Mobile Network(PLMN), it is important to cancel the echo reflected from the Public Switched Telephone Network(PSTN) side. In case of digital mobile system, the round-trip delay of the echo is in excess of about 180 milliseconds due to frame-by-frame voice coding. It is necessary to cancel the echo in PLMN. We have developed a multi-channel echo canceller tht operates with Time Switch Module in a Mobile Switching Center(MSC). The general echo canceller needs PCM trunk interface circuits and the tone detection and disabling circuits, but the multi-channel echo canceller linked with Time Switch Module does not need them. Therefore we could develop the effective and economical echo canceller.

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An Integrated Emergency Call System based on Public Switched Telephone Network for Elevators

  • Lee, Guisun;Ryu, Hyunmi;Park, Sunggon;Cho, Sungguk;Jeon, Byungkook
    • International journal of advanced smart convergence
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    • v.8 no.3
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    • pp.69-77
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    • 2019
  • Today, most of elevators have an emergency call facility for emergency situations. However, if the network installed in the elevator is also out of power, it cannot be used for the elevator remote monitoring and management. So, we develop an integrated and unified emergency call system, which can transmit not only telephone call but also data signals using PSTN(Public Switched Telephone Network) in order to remote monitoring and management of elevators, even though a power outage occurs. The proposed integrated emergency call system to process multiple data such as voice and operational information is a multi-channel board system which is composed of an emergency phone signal processing module and an operational information processing module in the control box of elevator. In addition, the RMS(remote management server) systems based on the Web consist of a dial-up server and a remote monitoring server where manages the elevator's operating information, status records, and operational faults received via the proposed integrated and unified emergency call system in real time. So even if there's a catastrophic emergency, the proposed RMS systems shall ensure and maintain the safety of passengers inside the elevator. Also, remote control of the elevator by this system should be more efficient and secure. In near future, all elevator emergency call system need to support multifunctional capabilities to transmit operational data as well as phone calls for the safety of passengers. In addition, for safer elevators, it is necessary to improve them more efficiently by combining them with high-tech technologies such as the Internet of Things and artificial intelligence.