Method and apparatus for transformation of a signal
OwnerGerald Hoeferinventor
Life of this patent
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Abstract
A method and an apparatus for the transformation of a signal on a four-wire line are proposed where the signal comprises of discrete amplitude height levels that are intended for a conversion into a corresponding analog signal with amplitude height levels suitable for a two-wire line and the analog signal is intended for a data communication unit that connects to the two-wire line and which has a predefined amplitude resolution for the analog signal. The amplitude height levels of the signal on the four-wire line are transformed in such a way in the domain of the four-wire line that the number of amplitude height levels which the communication unit can discern in the analog signal match a presetable criterion.
Claims41
A method for transforming a signal (DS) on a four-wire line which comprises discrete amplitude height values (P1, . . . , Pn) for conversion into a corresponding analog signal (AS) with amplitude height values (A1, . . . , An) on a two-wire line where said analog signal (AS) is intended for a data communication unit connectable to the two-wire line and where said data communication unit has a predefined capability for resolution of the amplitude of said analog signal (AS) and said method being determined by:
- said amplitude height values (P1, . . . , Pn) of signal DS on the four-wire line are each transformed by application of a transformation (T) where said transformation is determined in such a way that the number (n) of said amplitude height values (A1, . . . , An) which said communication unit can discern in said analog signal (AS) matches a presetable criterion (K).
A method according to one of the previous claims, wherein said transformation (T) is a multiplication of said amplitude height values (P1, . . . , Pn) with a factor (V).
A method according to one of the previous claims, wherein said factor (V) is calculated by the determination of the constellation of said signal (DS).
A method according to one of the previous claims, wherein said factor (V) is calculated by the determination of the minimal difference (Dmin) of two amplitude height values (Ai, Aj) of said analog signal (AS) that said communication unit (10) can discern.
A method according to one of the previous claims, wherein said signal (DS) comprises amplitude height values (P1, . . . , Pn) according to a predefined characteristic, in particular a characteristic adhering to ITU recommendation G.711.
A method according to one of the previous claims, wherein said transformation is done by replacing each amplitude height value (P1, . . . , Pn) according to a mapping by a predefined amplitude height value.
A method according to one of the previous claims, wherein said transformed amplitude height values (P1, . . . , Pn) exhibit a predefined accuracy, in particular at least 12 bit.
A method according to one of the previous claims, wherein said communication unit (10) is a PCM modem and said signal (DS) originates form a digital modem (50).
A method to detect the presence of a modem connection from said signal (DS) comprising the steps of:
- a) checking, whether said signal (DS) exhibits a silence period in the range of 70 to 80 ms and, if the signal amplitude matches a predefined low amplitude height value during said silence period, issuing a modem detect signal;
- b) otherwise, if the silence period exceeds 80 ms, checking whether the signal following the silence period (DS) represents a predefined characteristic signal of a PCM modem and, if positive, issuing a modem detect signal.
A method according to one of the previous claims implemented in a network termination unit.
An apparatus adapted for the implementation of the methods according to one of the previous claims.
An apparatus according to the previous claim, further comprising means to store the constellation.
An apparatus according to one of the previous claims referring to apparati, wherein an implementation in a network termination unit is intended.
An apparatus according to one of the previous claims referring to apparati, wherein the apparatus is activated at the start of a data communication between a transmission unit and said communication unit.
An apparatus according to one of the previous claims referring to apparati, wherein said communication unit (10) is an analog PCM modem and said signal (DS) is generated by a digital modem (50).
An apparatus according to one of the previous claims referring to apparati, further comprising a control unit (40), in particular a microcontroller or a digital signal processor.
An apparatus for detection of a modem connection from a signal (DS) comprising:
- a) first means (310, 315, 316) to check whether said signal (DS) comprises amplitude height values corresponding to a silence period in between 70 and 80 ms;
- b) second means (320, 325, 326, 330) to check whether said signal (DS) following said silence period is a predefined characteristic signal of a PCM modem;
- c) means (340) for issuing a modem detect signal.
A codec device (21) that contains an apparatus according to one of the apparatus claims.
A network termination unit (2) that contains an apparatus according to one of the apparatus claims.
Dependencies are inferred from the claim text.