Quality evaluation method
The invention relates to a method for evaluating the quality of a signal transmission path ( 2 ) presenting non-linear distortions. According to said method a specified test signal is sent from a transmitter ( 1 ) to a receiver ( 3 ). First the level of the received signal is adjusted in the receiver ( 3 ) and then a global quality evaluation is carried out using a specified comparative method. To adjust the signal level a local quality evaluation ( 11 ) based on the specified comparative method is carried out in a specified number of different, predefined windows (V 1 , à, VN−1, VN). Thereafter at least one window with an adequate local transmission quality is determined. The ratio of signal level of the test signal to signal level of the received signal is calculated in at least one window and the level of the entire received signal is adjusted on the basis of this ratio. Preferably only windows containing, for example, at least 50% of the total signal energy are used for adjusting the level. The quality evaluation can be carried out using a known method such as the BSD method.
1. Method for performing a quality assessment of a signal transmission link having non-linear distortion, in which a predetermined test signal is transmitted from a transmitter to a receiver, the level of the received signal is first adjusted in the receiver and then a global quality assessment is performed by means of a predetermined comparison method, characterized in that, for the purpose of adjusting the level,
a) a local quality assessment based on the predetermined comparison method is performed in a predetermined number of different, predefined time windows (V 1 , . . . VN−1, VN), in that
b) at least one window having adequate local transmission quality is determined, in that
c) the ratio of the signal level of the test signal to the signal level of the received signal is calculated in at least one of the windows determined, and in that
d) the level of the total received signal is set on the basis of said ratio.
2. Method according to claim 1 , characterized in that only those windows in which the spectral energy density of the test signal exceeds a predetermined threshold are used for the level control.
3. Method according to claim 2 , characterized in that the threshold is selected in such a manner that the selected windows together contain at least 50%, preferably about 70% of the total signal energy of the test signal.
4. Method according to claim 3 , characterized in that a voice signal is used as a test signal and in that the selected windows are free of silence intervals.
5. Method according to claim 3 , characterized in that the transmission quality is determined in accordance with the BSD method.
6. Method according to claim 2 , characterized in that a voice signal is used as a test signal and in that the selected windows are free of silence intervals.
7. Method according to claim 2 , characterized in that the transmission quality is determined in accordance with the BSD method.
8. Method according to claim 1 , characterized in that a voice signal is used as a test signal and in that the selected windows are free of silence intervals.
9. Method according to claim 8 , characterized in that the transmission quality is determined in accordance with the BSD method.
10. Method according to claim 1 , characterized in that the transmission quality is determined in accordance with the BSD method.
11. Device for carrying out the method according to claim 1 , comprising a receiver for receiving a received signal transmitted from a transmitter via a signal transmission link, the receiver comprising a level control for adjusting the level of the received signal, and a quality assessment, characterized in that the level control comprises
a) a circuit for performing a local quality assessment in a predetermined number of different, predefined time windows,
b) a circuit for determining at least one window having adequate local transmission quality,
c) a circuit for calculating the ratio of the signal level of the test signal to the signal level of the received signal in at least one of the windows determined,
d) an amplifier which adjusts the level of the total received signal on the basis of the said ratio.
12. Method for performing a quality assessment of a signal transmission link having non-linear distortion comprising the steps of:
transmitting a test signal from a transmitter to a receiver;
defining a number of time windows;
determining that the received signal in at least one time window has adequate local transmission quality by performing a local quality assessment of the received signal in a predetermined number of different time windows based on a predetermined comparison method;
calculating a ratio of a signal level of the test signal to a signal level of the received signal in the at least one time window; and
setting the level of the total received signal on the basis of said ratio.
13. Method for performing a quality assessment of a signal transmission link having non-linear distortion comprising the steps of:
transmitting a test signal from a transmitter to a receiver;
defining a number of time windows;
selecting at least one of the time windows based on the transmission quality of the received signal in the selected at least one time window;
calculating a ratio of a signal level of the test signal to a signal level of the received signal in the selected at least one time window; and
setting the level of the total received signal on the basis of said ratio.