Distinguishing between final coding of received signals in a PCM modem

摘要

A method for determining the encoding law of an incoming signal in a network which possibly contains an A-mu or mu-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 $Q=\frac{1}{2}\left(\sum _{i=\mathrm{i5}}^{i-\mathrm{i6}}\mathrm{DL}\left(i\right)+\sum _{i=\mathrm{i5}}^{i=\mathrm{i6}}\mathrm{DLm}\left(i\right)\right)-S_m\frac{{\mathrm{Ly}}^2}{2}$ 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.