In this paper a new method of estimating error margin inTcarrier repeaters is proposed. This estimate is based on two sets of data: (a) measurements from a commonly used test wherein bipolar violations are inserted into the line at an audio rate, and (b) the crosstalk environment in which the repeater is operating. An audio component due to violations in the bipolar signal causes a shift in the eye pattern resulting in a change of repeater error rate. This in turn changes the regenerated audio signal power by an amount depending on the initial undisturbed error rate of the repeater. This then gives a basis for extrapolating the operating error rate of a repeater from a test measurement. This error rate combined with a knowledge of the cable crosstalk parameters and number of operating systems during the test, is then used to estimate the error margin or eye opening of the repeater, assuming a Gaussian distribution for the interference. A method of ranking repeaters in a repeatered line to indicate their relative margin is proposed wherein the effect of errors on the audio signal to an intermediate test repeater is taken into account. Results presented are quite general and valid at any line rate and repeater spacing, and hence applicable for differentT-carriers such asT1, T1C, T2, etc.

A straightforward procedure is described for estimating the effect of carrier mistracking and phase jitter on the error rate of a digital microwave radio receiver using a Quadrature Partial Response Scheme (QPRS) for modulation. Graphical results presented can be readily used to gain insight into the performance of a QPRS receiver.

We present in this paper a unified approach to the crosstalk interference problem arising in PCM transmission on paired cables. For bipolar signaling, and three types of commonly used channel shaping, viz., cosine, raised cosine, and Gaussian, we present the minimum average near-end crosstalk (NEXT) and far-end crosstalk (FEXT) loss requirements at any transmission rate as a function of repeater spacing and number of interfering pairs so as to meet a desired error rate objective. This will aid in indicating if new cables need to be developed for a proposed rate of transmission or, for a given cable, the error margin available for degradations other than crosstalk can be readily determined. Extension to other coding schemes is indicated, and crosstalk compatibility is examined for mixedTsystems, such asT1,T1C, andT2. Graphical results are presented to readily aid in system design of anyTcarrier with repeater spacings up to 70 dB.

In this concise paper we describe an efficient scheme for random and burst error checking by a combination of serial parity checking and convolutional interleaving. The framing for interleaved blocks is shown possible by a simple implementation, and the error detection capability is better than other schemes similar in complexity. The proposed scheme has useful applications for digital transmission.

We consider optimum uniform data quantization for noisy channels. We present a general formulation for natural encoding that results in simple expressions for the mean-square error. Specifically, we show that the optimum location of the center of the quantizer is at the mean of the distribution for all error rates. The optimum levels for quantization and the corresponding mean-square error are presented for Gaussian and uniform data. For the latter the width of the optimum quantizer for noisy channels is shown to be smaller than the entire range of probability distribution.