Distinguishing between final coding of received signals in a PCM modem

Abstract

A method for determining the encoding law of an incoming signal in a network which possibly contains an A-μ or μ-A conversion includes obtaining digital impairment learning (DIL) probing data, generating an ordered table of levels therefrom, using the table to find two functions, and using a logical analysis of the functions to determine the encoding law of the signal. A first function is a maximum from the values DL(i) and the threshold Th1 which are less than T(i), with T(i)=a +bi, and DL(i)=L(i+16)−2L(i) with L(i) being the DIL signal corresponding to the transmitted Ucode=i. A second function Q is defined by: 1 Q = 1 2 ⁢ ( ∑ i = i5 i - i6 ⁢ ⁢ DL ⁡ ( i ) + ∑ i = i5 i = i6 ⁢ ⁢ DLm ⁡ ( i ) ) - S m ⁢ Ly 2 2 where DLm(i) is the median value of a windowed group of values for DL(i) where i ranges from i5 to i6, Ly=i6−i5−1, and Sm is a mean of a windowed group of slopes, wherein each slope relates to the difference between certain DLm(i) values.

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