This application claims the priority of Korean Patent Application No. 2003-64157, filed on Sep. 16, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method for measuring the quality of an input signal, and more particularly, to a method for measuring the quality of an input signal to confirm whether the input signal is capable of being restored to an original signal through signal processing.
2. Description of the Related Art
When a signal containing noise is received by a communication system and a data storage apparatus, it is necessary to determine whether or not the received signal is of high enough quality to be restored without error through signal processing to an original signal before transmission.
At this time, if the original data before transmission is known, it is possible to determine the presence of errors by comparing data actually obtained through signal processing with the original data, and by doing so, the quality of the signal can be evaluated. However, in most cases, the original data before transmission is not known, and it is difficult to evaluate the quality of an input signal.
Meanwhile, in order to transmit more data within a limited transmission bandwidth in a communication system and to store more data in a limited area in a storage device, complex signal processing algorithms for an adaptive equalizer and a viterbi detector came into use in a data detection process, supplanting the older signal processing method of simply determining the polarity of a signal.
In the system using such a complex signal processing algorithms, for the adaptive equalizer and the viterbi detector, the bit error rate (BER) after signal processing and the detected jitter value came to show dissimilar characteristics.
According to an aspect of the present invention, a signal quality measuring method and apparatus, in which, by measuring the quality of an input signal based on the characteristic of a channel, a more accurate measurement of signal quality can be obtained than by the conventional method, and a recording medium having embodied thereon a computer program to execute the method are provided.
According to an aspect of the present invention, there is provided a method of detecting the quality of an input signal, including calculating an estimated signal from the input signal by using a predetermined filter coefficient, updating the filter coefficient so that a difference value between the estimated signal and the input signal is minimized, and based on the updated filter coefficient, calculating the quality of the input signal.
According to another aspect of the present invention, there is provided an apparatus for detecting the quality of an input signal, including, an estimated signal calculation unit which calculates an estimated signal from the input signal by using a predetermined filter coefficient; a filter coefficient calculation unit which updates the filter coefficient so that a difference value between the estimated signal and the input signal is minimized; and an input signal quality determination unit which, based on the updated filter coefficient, calculates the quality of the input signal.
According to still another aspect of the present invention, there is provided a computer readable recording medium having embodied thereon a computer program for executing a method of detecting the quality of an input signal, wherein the method includes, calculating an estimated signal from the input signal by using a predetermined filter coefficient, updating the filter coefficient so that a difference value between the estimated signal and the input signal is minimized, and based on the updated filter coefficient, calculating the quality of the input signal.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The above and/or other aspects and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings of which:
Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.
The data detection unit 422 converts an input RF signal from a channel 490 into digital data and outputs the digital data to the channel characteristic detection filter 424. The data detection unit 422 may use a slicer algorithm that distinguishes between 1 and 0 by considering only the polarity of a signal. Alternatively, it may use a complex signal processing algorithm in order to more accurately detect data. An appropriate algorithm for the data detection unit 422 is chosen in consideration of the complexity of a circuit and detection error, which is within the ordinary skill in the art and will not be described in detail.
The channel characteristic detection filter 424 converts the digital data input from the data detection unit 422 into an RF signal with the same form as the input signal, according to filter coefficient Wk input from the filter coefficient calculation unit 460. The channel characteristic detection filter 424 outputs an estimated RF signal Yk The method for calculating filter coefficient Wk will be explained in more detail below.
In order to generate a delayed RF signal Xk, the input signal delay unit 440 delays the input RF signal a time which is the amount of time taken from the input of the RF signal to the data detection unit 422, to the generation of the estimated RF signal yk in the channel characteristic detection filter 424, and outputs the signal xk to the filter coefficient calculation unit 460.
By using the difference between the estimated RF signal yk input from the channel characteristic detection filter 424, and the delayed input RF signal xk input from the input signal delay unit 440, the filter coefficient calculation unit 460 updates the filter coefficient Wk used in the channel characteristic detection filter 424 so that the estimated RF signal yk matches the delayed input RF signal xk as closely as possible.
In other words, in order to obtain the filter coefficient Wk used in measuring the quality of a signal, the difference between the delayed input RF signal xk and the estimated RF signal yk is obtained, and then the coefficient Wk is modified so that the difference can be minimized. And, this operation is performed repeatedly until the filter coefficient Wk converges. At this time, a method for converging a coefficient may involve a variety of adaptive equalization algorithms frequently used in signal processing theory. An appropriate algorithm is chosen in consideration of converging time, error, and the complexity of a circuit.
If the number of unit input signals reaches a predetermined value, by using the filter coefficient Wk from the filter coefficient calculation unit 460 and the input RF signal, the interval setting unit 482 determines that the filter coefficient Wk has converged, and outputs the result to the signal quality calculation unit 484. For example, if the number of channel bits reaches 216, the interval setting unit 482 determines that the filter coefficient Wk has converged. Alternatively, a width variation of the filter coefficient Wk may be considered. For example, if the width variation of the filter coefficient Wk during a predetermined time period is within a predetermined range, it is determined that the filter coefficient Wk has converged.
When the result that the filter coefficient Wk has converged is received from the interval setting unit 482, the signal quality calculation unit 484 calculates a final signal quality by using the filter coefficient Wk input from the filter coefficient calculation unit 460, and outputs the result.
A function used by the signal quality calculation unit 484 is determined such that signal quality can be represented most characteristically in filter coefficient Wk for each signal quality in actual communication systems and storage apparatuses.
Aspects of the signal quality detection apparatus 400 shown in
ek=xk−yk (1)
Wk+1=Wk+2μekXk (2)
Here, ek denotes the difference value between the delayed input RF signal and the estimated RF signal, μ denotes a gain value to determine a compensation speed, and Xk denotes delay values corresponding to input RF signals.
At this time, the input signal used is obtained by adding noise corresponding to tangential tilt −0.6 through 0 when data is recorded with a density of 31 GB on a 12 cm Blu-ray (BD) disk used to obtain the data plotted in
Thus, the characteristic of a signal with respect to tilt is expressed in the sixth through tenth taps, the 15th tap, and the 20th through 24th taps. Accordingly, by reflecting these findings, Equation 3 expressing the quality of a signal is obtained. Equation 3 shows how much distortion has occurred compared to a reference gain.
SQ=k−{C15+(C6−C7)+(C6−C8)+(C6−C9)+(C6−C10)}−{(C24−C20)+(C24−C21)+(C24−C22)+(C24−C23)} (3)
Here, SQ denotes a signal quality value and k is a constant. In the example aspect, k is set to 0.25.
In the embodiment of
In operation 1010, the input RF signal is converted into digital data. In operation 1020, the digital data converted in operation 1010 is converted into an RF signal like the input signal, by using a filter having a predetermined filter coefficient Wk and calculating an estimated RF signal yk. The method of calculating the filter coefficient Wk will now be explained in detail.
In operation 1030, the delayed RF signal xk is generated by delaying the input RF signal for the time taken from input of the input RF signal to generation of the estimated RF signal yk. In operation 1040, by using the difference between the estimated RF signal yk calculated in operation 1020, and the delayed input RF signal xk calculated in the operation 1030, filter coefficient Wk used as the filter coefficient in the channel characteristic detection filter is updated so that the estimated RF signal yk matches the delayed input RF signal xk as closely as possible.
In operation 1050, it is determined whether or not filter coefficient Wk updated in operation 1040 has converged.
If it is determined that filter coefficient Wk has converged, then operation 1060 is performed.
If it is determined that filter coefficient Wk is not converged, then the operation 1020 is performed again. In the operation 1020, based on filter coefficient Wk updated in operation 1040, the estimated RF signal yk is generated and then the next operation is performed.
In the above embodiment of the present invention, when the number of input RF signals reaches a predetermined value, that is, if the number of channel bits reaches 216, it is determined that the filter coefficient Wk has converged.
Alternatively, width variation of the filter coefficient Wk may be considered. For example, if the width variation of the filter coefficient Wk during a predetermined time period is within a predetermined range, the coefficient Wk is determined to have converged.
In operation 1060, if it is determined in operation 1050 that the filter coefficient Wk has converged, the final signal quality is calculated by using the filter coefficient Wk updated in operation 1040, and the result is output.
The present invention can also be embodied as computer readable codes on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission over the Internet). The computer readable recording medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.
As described above, the method and apparatus for measuring the quality of an input signal according to the present invention measures the quality of an input signal based on the characteristics of a channel, such that a more accurate measurement of signal quality can be obtained than in the conventional art. Thus, the present invention can be effectively applied to next-generation communications systems and recording apparatuses for transmitting and recording increasingly larger amounts of data.
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Number | Date | Country | Kind |
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2003-64157 | Sep 2003 | KR | national |