Telecommunications – Transmitter and receiver at separate stations – Distortion – noise – or other interference prevention,...
Reexamination Certificate
1999-02-05
2001-09-04
Maung, Nay (Department: 2681)
Telecommunications
Transmitter and receiver at separate stations
Distortion, noise, or other interference prevention,...
C455S278100, C375S296000
Reexamination Certificate
active
06285859
ABSTRACT:
OBJECT OF THE INVENTION
The present invention refers to a method for predistortion of a signal transmitted or sent from a first unit to a second unit of a telecommunications system, as well as a unit for carrying out the method. For example, the two units exchange data or voice signals through a radio channel, an optical fibre, a copper wire, or any other type of physical medium.
STATE OF THE ART
Typically, a unit in accordance with the present invention equalizes the received signal and predistorts the transmitted signal. The unit comprises an equalizer in the reception chain and a predistorter in the transmission chain. The object of incorporating the equalization and predistortion functions in the same unit is to reduce the cost of the other remote unit/s exchanging data with the said unit; these remote units do not need equalizers.
A unit of this type, including an equalizer and a predistorter, is known from the document “Adaptive channel precoding for personal communications” by W. ZHUANG et al., published in the magazine “Electronics Letters” on Sep. 15, 1994, Vol. 30, No. 19, pages 1570-1571. In accordance with this document, over a period of time, the same equalization coefficients computed in reception are used to predistort the signal transmitted. This solution results from the hypothesis that the interferences or distortions that are applied to the sent or transmitted signal are the same as the interferences that are applied to the signal received, that is, that the characteristics of the transmission and reception channels are the same.
This hypothesis is false if the respective transmission and reception channels are different, for example (a)—through being defined by respective frequencies that are different among themselves, as is the case in Frequency Duplex Division (FDD), or—(b)—through being defined by physical media that are different among themselves, etc . . .
CHARACTERIZATION OF THE INVENTION
One object of the present invention is to define methods of predistorting a signal transmitted from a first unit to a second unit in a telecommunications system, taking into account the difference in characteristics between the respective transmission and reception channels. Accordingly, a method of predistorting a signal sent from a first unit to a second unit, the first unit sending data to the second unit through a first channel and the second unit sending data to the first unit through a second channel, the method comprising the following step:
in the first unit, the computing of representative coefficients of the second channel on the basis of a second predetermined sequence sent from the second unit to the first unit; is characterized in that it comprises the following steps:
the sending by the first unit of a first predetermined sequence to the second unit which sends it back in the form received to the first unit, in the form of a return sequence;
in the said first unit, the computing of representative coefficients of the first and second channels jointly, on the basis of the return sequence received; and
predistortion of the signal sent by the first unit by means of inverse coefficients of the first channel which are computed according to the said representative coefficients of the second channel and the said representative coefficients of the first and second channels jointly.
According to a first sub-alternative, the representative coefficients of the second channel are inverse coefficients of the second channel, and the representative coefficients of the first and second channels jointly are direct coefficients of the first and second channels jointly, predistortion being carried out with the inverse coefficients of the convolution of both the inverse coefficients of the second channel and the direct coefficients of the first and second channels jointly.
According to another sub-alternative, the representative coefficients of the second channel are direct coefficients of the second channel and the representative coefficients of the first and second channels jointly are inverse coefficients of the first and second channels jointly, predistortion being carried out by means of he coefficients of the convolution of the direct coefficients of the second channel and of the inverse coefficients of the first and second channels.
Another object of the present invention is to define units for predistorting a signal to be transmitted in accordance with the methods defined above. Accordingly, a unit for carrying out this method comprises:
means to predistort the signal to be sent; and it is characterized in that it comprises:
means to compute representative coefficients of the second channel on the basis of a second predetermined sequence sent from the remote unit to the unit;
means to send a first predetermined sequence to the remote unit, which sends it back in the form received to the said unit, in the form of a return sequence;
means to compute representative coefficients of the first and second channels jointly, on the basis of the return sequence received; and in that
the predistorting means predistort the signal sent by the inverse coefficients of the first channel which are computed according to the said representative coefficients of the second channel and the said representative coefficients of the first and second channels jointly.
In accordance with the present invention, another method to predistort a signal sent from a first unit to a second unit, the first unit sending data to the said second unit through a first channel and the second unit sending data to the first unit through a second channel, the method comprising the following step:
in the first unit, the computing of representative coefficients of the second channel on the basis of a second predetermined sequence sent from the second unit to the first unit; and it is characterized in that it comprises the following steps:
the sending by the first unit to the second unit of a first sequence which results from the convolution of a predetermined sequence and of the said representative coefficients of the second channel, the first sequence being sent back in the form it was received by the second unit to the first unit in the form of a return sequence;
in the said first unit, the computing of inverse coefficients of the first channel on the basis of the said return sequence; and
predistortion of the signal sent by the first unit on the basis of the said inverse coefficients of the first channel.
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Duran Alfonso Fernandez
Nunez Leon De Santos Gregorio
Alcatel
Gelin Jean A
Maung Nay
Sughrue Mion Zinn Macpeak & Seas, PLLC
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