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

Abstract

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.

Frequency domain data transmission using reduced computational complexity algorithms

“…e j2,t 30<t<NT, T=* , fn= equivalently, x(t) is a sum of sinusoidal signals whose amplitudes are determined by the sets of data values {A5} and {B5} , as depicted in figure (2). This interpretation makes the transmitter an implementation of a frequency division multiplexing (FDM) system [lj If the signal x(t) is transmitted thru a linear channel with impulse response h(t) and frequency response H(w) , then the signal at the output of the channel s(t) is determined by the convolution of x(t) and h(t) , or in the frequency domain by S(w) H(w).X(w).…”

“…We also define the updated equalizer for the k + 1n frame Since the subsequence frame boundary is out of synchronization, Dk (12a) the receiver picks-up a time shifted version of the response of the = k channel to the repeated PN subsequence. Based on the spectral characteristics of the telephone channel, as obtained in the last survey on analog transmission performance of telephone lines [2] , allocation of frequency bins can be made as shown in fig. (3).…”

1982/83 End Office Connection Study: ASPEN Data Acquisition System and Sampling Plan

“…With 20 RTUs allocated to the EOCS* at least 380 basic experi-• Examination of data from Ref. 7 suggests that one deployment of 20 RTUs would be sufficient to achieve the goals of the study. As we noted, the sample was required to adequately represent various strata.…”

A 2400-Bit/s Microprocessor-Based Modem

“…By analyzing a recent survey of voiceband channels [9], it was found that a good compromise between performance and complexity was to consider that the first leading and trailing echoes i_, and *, are dominant, and also that the second trailing echo ij is small enough to allow approximating (9) by (10) where fi^ is considered as additional noise. In (10), e and 0, which will be termed "phase echoes," can take on 16 and 4 possible values, respectively, depending on the data sequence transmitted.…”