1969-70 Connection Survey: High-Speed Voiceband Data Transmission Performance on the Switched Telecommunications Network

Balkovic, Mislav; Klancer, H. W.; Klare, S. W.; McGruther, W. G.

doi:10.1002/j.1538-7305.1971.tb02557.x

Cited by 26 publications

(10 citation statements)

References 9 publications

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“…Second, digital signals have been transmitted over tele phone lines and the difference between the transmitted and received signals has been analyzed, providing an indirect measurement of telephone channel noise. [4][5][6][7][8][9][10][11][12][13][14][15][16] It is extremely difficult to correlate these two types of measurements. This paper is solely concerned with direct measurements of telephone channel noise sample functions.…”

Section: Summary Of Past Workmentioning

confidence: 99%

A Statistical Analysis of Telephone Noise

Stuck¹,

Kleiner²

1974

Bell System Technical Journal

122

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The results of a statistical analysis of telephone noise are presented. The analysis consists of two stages: an exploratory data analysis stage, where the data are characterized through various nonparametric statistics and a model‐building stage, where the data are matched to models. The exploratory data analysis stage involved examination of noise waveforms, power spectra, and covariance estimates. The results show that telephone noise consists of a deterministic component (sinusoids at various frequencies) and a stochastic component. It is assumed that these components add. The data are filtered to remove the deterministic component. Next, central moment estimates are presented, as well as first‐order amplitude statistics (histograms and empirical cumulative distributions) for these filtered data. The results indicate that the filtered data appear wide‐sense stationary over short periods of time (typically 1 second) and, although close to gaussian, are distinctly nongaussian. The model‐building stage involved fitting the filtered data to two classes of models. The first class of models is based on symmetric stable distributions that arise from the central limit theorem. The second class of models assumes two different physical processes that contribute to the random component of telephone noise: The low‐variance process is assumed to be gaussian, while the high‐variance component is assumed to be a filtered Poisson process. Both classes of models agree intuitively with the physical processes generating telephone noise and are mathematically tractable. Based largely on graphical tests, both models appear to fit the filtered data reasonably well.

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Section: Summary Of Past Workmentioning

confidence: 99%

A Statistical Analysis of Telephone Noise

Stuck¹,

Kleiner²

1974

Bell System Technical Journal

122

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“…Also as over 90% of the bursts have length less than 53 [6], the error resulting from this assumption will not be very great. In the random error case P(single error in block / error in block) = l(BER)(l -BER)11t…”

Section: =2mentioning

confidence: 95%

“…From [6] one can observe that the average bit error rate within a burst is about 1 in 4. An average burst would then contribute only a single bit error to the block provided it started in the last 4 bits of the block or ended in the first 4 bits of the block.…”

Section: -(L -Ber)1mentioning

confidence: 98%

“…(6) The improvement tn bit (burst) error rate, as a result of encoding and judged via the frame error rate it produces is obtained as follows.…”

Section: -(L -Ber)1mentioning

confidence: 99%

“…A telephone line channel is a channel which exhibits both random and burst errors [6]. Codes that are suitable for such channels are given in [7,8].…”

Section: Cnding Considerationsmentioning

confidence: 99%

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Error correction scheme for telephone line transmission of RELP vocoder

Wadia

ICASSP '80. IEEE International Conference on Acoustics, Speech, and Signal Processing

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This paper presents a scheme for encoding the output bits of an 8500 bps residual excited linear predictive coder (RELPC), in which the quality of the synthesized speech is more sensitive to errors tn certatn btts.Fifty-two of the 272 bits in a 32 ms voice frame were identified as most critical and in need of protection. A Burst-trapptng code, using a (21,14) Single Error Correcting Double Error Detecting shortened Cyclic Hamming code as the basic block code was constructed. The code was selected with due consideration so computational load, delay sn decodtng and total bit rate requirement of less than 9.6 kbs. The paper also describes a Markov model for the decoding process and then determtnes the improvement in quality resulting from the use of the above scheme. In particular a bit error rate of 5 x l0 is reduced to 3 x 106 and a burst error rate of 5 x I o is reduced to 6.8 x I pS• Some of the effects of errors on auditory perception which appear counter intuitive are briefly dtscussed.Description of the RELP vocoder output.The RELPC vocoder used for this investigation [11, outputs 272 bits of vucoded information for each 32 ms interval (henceforth called a frame) of voice. The 272 hits consist of:1. 32 bits for the reflection coefficients of the vocal ttact filter.2. 20 hits for energy in the high frequency ( > 800 cycles) part of the residual excitation. 3. 200 bits for the residual excitation in 5 sub-bands between 250 and 875 cycles.4. 15 allocation bits. With 8 samples per sub-band, there are on the average 5 bits per sample per sub-band. However the 25 bits per sample are not equally distributed amongst the 5 sub-bands and the number of bits associated with each sub-band is encoded in an additional 3 bits, giving a total of 15 bits for the 5 sub-bands. 5. A 5 bit table-index for the quantization step sizes for the residual excitation of all sub-bands.The transmission of 272 bits in a interval of 32 ms, gives a transmission bit rate of 8.5 kbps. Since a 9.6 kbps modem is to be used, there are 35 remaining bits per frame which could be used as check bits for encoding the frame for crror correction. It is well known [2]-[5], that errors in different bits effect the quality and intelligibility of the synthesized speech to different degrees. Having performed some tests on the digitized speech files at our disposal, we obtained the following order, of decreasing sensitivity to the synthesized speech, among the bitt. a. The 32 bits of the 8 reflection coefficients.b. The 15 allocation bits. c. The 5 bits that give the quantizer step size of the residual signal.d. The 20 bits that give the high frequency energy. e. The 200 bits of residual excitation in the 5 sub-bands. It was therefore decided to protect only the 52 bits specified in a, b and c. Cnding considerations.A telephone line channel is a channel which exhibits both random and burst errors [6]. Codes that are suitable for such channels are given in [7,8]. According to these papers the Burst-trapping Codes give the best results. We designe the code to...

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1969-70 Connection Survey: Analog Transmission Performance on the Switched Telecommunications Network

Duffy¹,

Thatcher²

1971

Bell System Technical Journal

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To characterize the transmission performance of the Bell System switched telecommunications network, Bell Telephone Laboratories conducted a survey of toll connections during 1969 and 1970. Connections were established between Bell System end offices chosen by statistical sampling techniques. Both analog and data transmission tests were performed. A summary of analog transmission performance is presented in this paper. It contains estimates for noise, loss, attenuation distortion, envelope delay distortion, peak‐to‐average ratio, frequency offset, level tracking, nonlinear distortion, and phase jitter for toll calls within the Bell System. Accompanying papers discuss data transmission error performance at various speeds between 150 and 4800 bits per second.

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1969-70 Connection Survey: High-Speed Voiceband Data Transmission Performance on the Switched Telecommunications Network

Cited by 26 publications

References 9 publications

A Statistical Analysis of Telephone Noise

A Statistical Analysis of Telephone Noise

Error correction scheme for telephone line transmission of RELP vocoder

1969-70 Connection Survey: Analog Transmission Performance on the Switched Telecommunications Network

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