KR19990002695A - Method for Determining Optimum Transmission Symbol Rate of Modulator - Google Patents

Abstract

The present invention provides a method for determining an optimal transmission symbol rate of a modem for determining a symbol rate of a modulator and a transmission frequency band in handshaking for determining a transmission channel between modulators used in a data transmission apparatus. It is about.

The present invention analyzes the power distribution of the frequency including the received signal, and compares the average frequency power of the lower band with the lower threshold of the frequency band including the signal source and the signal source includes the average frequency power of the upper band. The optimal symbol rate and carrier frequency are determined by comparing with the upper limit threshold of the frequency band.

Description

Method for Determining Optimum Transmission Symbol Rate of Modulator

1 is a table showing the symbol rate of a modulator and its carrier frequency.

2 is a block diagram of a typical data transmission apparatus.

3 is a flowchart illustrating a process of determining an optimal transmission symbol rate of a conventional modulator.

4 is a flowchart illustrating an optimal transmission symbol rate method of a demodulator according to an embodiment of the present invention.

5 is a table showing the symbol rate and frequency characteristics of the demodulator used in the present invention.

* Description of the symbols for the main parts of the drawings *

10: input / output device 11: communication network

16 microcontroller device 14 memory

16: change demodulator

The present invention relates to a handshaking process for determining a transmission channel between modulators used in a data transmission apparatus, and in particular, an optimal transmission symbol of a modem for determining a symbol rate and a transmission frequency band of a modulator. It relates to a rate determination method.

In general, a demodulator is a kind of data relay that is used in a digital transmission device to modulate the digital data to be transmitted in the form of an analog signal and to recover the digital data from the received analog signal. Such a demodulator must maintain an optimal channel state with the other side's demodulator in order to accurately relay digital data.

In addition, the modulator demodulates in accordance with the demand for high speed data transmission, and has a trend of having a plurality of symbol rates and carrier frequencies to enable data communication with a low demodulation demodulator. For example, the demodulator may have six symbol rates of 2400, 2743, 2800, 3000, 3200, and 3429 symbol rates, and corresponding carrier frequencies, as shown in the table of FIG. In the full duplex modem, the transmitting or receiving modem had to handshak with the other modem to match the symbol rate and carrier frequency with the other modem.

To this end, in the data transmission apparatus including the demodulator, the symbol demodulation and carrier frequency of the demodulator are gradually lowered from the best value to the lowest value, and the optimal transmission symbol rate of the modulator for detecting an error-free symbol rate and carrier frequency is detected. Determination methods are used. This optimal transmission symbol rate determination method causes the demodulators on both sides (i.e., the transceiver side) to attempt handshaking several times until the symbol rate is matched from the symbol value of the highest value. As a result, the conventional method for determining the optimal transmission symbol rate of the modulator requires a lot of time until the symbol rate and carrier frequency between the modulators are matched. Problems of the conventional transmission symbol rate determination method of the conventional demodulator will be described with reference to FIGS. 2 and 3.

2 shows a typical data transmission apparatus including a modulator. In FIG. 2, the data transmission device includes an input / output device 10 for inputting and outputting data, and a micro controller unit (hereinafter referred to as MCU) connected in series with the input / output device 10 ( 14) and a modulator 16, and a memory 12 connected to the MCU 14. The input / output device 10 transmits data and control commands to be transmitted from the operator to the MCU 14. The MCU 14 transmits data from the input / output device 10 to the communication network 11 via the modulator 16, and inputs data received from the communication network 11 via the modulator 16. Output is via the output device 10. The MCU 14 performs handshaking to match the symbol rate and carrier frequency of the demodulator (not shown) and the demodulator 16 of the counterpart connected to the communication network 11. The memory 12 temporarily stores the data to be transmitted and the information processed by the MCU 14, and also stores the symbol rate and carrier frequency tables shown in FIG. The modulator 16 modulates data to be transmitted to the communication network 11 in the form of an analog signal using a carrier wave of the frequency specified by the MCU 14 and demodulates the data from the analog signal from the communication network 11.

3 is a flowchart illustrating a method of determining an optimal transmission symbol rate of a conventional modem, which is performed by the MCU 14 shown in FIG. The flowchart of FIG. 3 will be described in conjunction with the circuit of FIG.

The MCU 14 sets the modulator 16 to the mode of the highest symbol rate and carrier frequency (step 20), and then searches whether the received data symbol from the modulator 16 contains an error ( Step 22). If an error occurs in the data symbol received in step 22, the MCU 14 resets the modulator 16 to the mode of the next symbol rate and carrier frequency and then returns to step 22 (step 24). ).

On the other hand, when there is no error in the data symbol received in step 22, the MCU 16 sets the symbol rate and carrier frequency set in the modulator 16 to the symbol rate and carrier frequency of the transmission channel (26th). step). The MCU 14 transmits and receives data through the modulator 16 (step 28).

As described above, in the conventional method of determining the optimal transmission symbol rate of the modulator, handshaking is performed until the error does not occur in the received data symbol while sequentially setting the symbol rate and the carrier frequency of the modulator from the highest value to the lower value. Must be repeated. For this reason, the conventional method for determining the optimal transmission symbol rate of a modulator has not only a long time to match the symbol rate and carrier frequency between modulators, but also has a disadvantage of delaying data transmission.

Accordingly, an object of the present invention is to provide an optimal transmission symbol rate determination method of a demodulator capable of minimizing a handshaking process to reduce a data transmission delay time.

In order to achieve the above object, the method for determining an optimal transmission symbol rate in a modem according to the present invention comprises the steps of determining the average power at the carrier frequency of the received signal, initial setting of the highest symbol rate, the lower band upper and lower reference frequency A process of searching for power, a process of searching for a lower band center frequency power from the lower band upper and lower frequency powers, and a first comparison process of comparing the lower band center frequency power with a lower threshold of a frequency band including a signal source And searching for the upper / lower limit reference frequency power of the upper band according to the first comparison process, searching for the average frequency power of the upper band from the upper / lower reference frequency power of the upper band, and receiving the average frequency power of the upper band. Results of the third comparison process comparing the upper bound threshold with circles and the third comparison process resulted in an optimal symbol rate Including the process of finalizing wave frequency.

Other objects and advantages of the present invention in addition to the above object will become apparent from the detailed description of the embodiments of the present invention with reference to the accompanying drawings.

Hereinafter, with reference to FIGS. 4 and 5 attached to an embodiment of the present invention will be described in detail.

4 is a flowchart illustrating a step-by-step method for determining an optimal transmission symbol rate of a demodulator according to an embodiment of the present invention, and is performed by the MCU 14 shown in FIG. The flowchart of FIG. 4 performed by this MCU 14 is explained as follows.

First, the MCU 14 obtains power distribution in the frequency domain with respect to the input signal received by the modulator 16. This power distribution data is stored in the memory 12 by the MCU 14. The MCU 14 sets the highest symbol rate R (0) of 3429 and the low carrier frequency (fc (0) (0)) mode of 1959 Hz in the symbol characteristic frequency characteristic table as shown in FIG. 5 ( Step 32). The MCU 14 then receives the received high frequency at the primary lower band lower limit reference frequency f _A , e.g. 150 Hz, for the mode of 3429 symbol rate and the low carrier frequency f (0) (0) of 1959 Hz. The power P _A of the signal, the first lower band upper limit reference frequency f _B , for example, the power P _B of the received high frequency signal at 300 Hz is retrieved from the input power distribution data (step 34). First lower-sideband lower limit reference frequency power P _A of the high-frequency signal at f _A, and the first lower-sideband upper reference frequency f by using the power P _B of the high-frequency signal in the _B primary lower sideband power of the RF signal at the center frequency P _L is calculated by the following equation (36).

P _L = P _A (1-K _L ) + K _L P _B (Equation 1)

K _L in Equation 1 is an experimentally obtained constant and is calculated by Equation 2 below.

(Equation 2)

In Equation 2, f _L is the center frequency of the first lower band. Next, the MCU 14 compares whether the power P _L of the high frequency signal at the first lower band center frequency f _L is greater than the product of the first critical slope α and the reference power P _ref (step 38). The first critical slope α and the reference power P _ref are experimentally obtained values, and the reference power P _ref is assumed to be a power value at a frequency of 1050 kHz in the distribution. This is because the linear distortion is the least at 1050 ㎑. Steps 34 to 38 calculate the power of the high frequency signal at the first lower band frequency with respect to the set carrier frequency and determine whether the power is above a predetermined value.

In step 38, when the power P _L of the high frequency signal at the center frequency of the first lower side band is smaller than the product of the first critical slope α and the reference power P _ref , the MCU 14 performs the carrier frequency of the current received high frequency signal. And the lower carrier frequency fc (0) (0) of the modulator 16 set as described above do not coincide, and the carrier frequency fc that can be used for the highest symbol rate R (0) is determined by the low frequency carrier frequency fc (0) (0). Instead, it readjusts to the high carrier frequency fc (0) (1) (step 40). At this time, if the current symbol rate is R (1) = 3200 in the table of FIG. 5, in step 40 according to the comparison result in step 38, it is 1920 instead of the low carrier frequency fc (0) (0) of 1829 Hz as the carrier frequency. The high frequency carrier frequency fc (0) (1) of f is set. Subsequently, the MCU 14 performs the power P _A of the received high frequency signal at the first lower band lower limit reference frequency f _A for the set high carrier frequency fc (0) (1), at the first lower band upper limit reference frequency f _B. The power P _B of the received high frequency signal is retrieved from the input power distribution data (step 42). First lower-sideband lower limit reference frequency power P _A of the high-frequency signal at f _A, and the first lower-sideband upper reference frequency f by using the power P _B of the high-frequency signal in the _B primary lower sideband power of the RF signal at the center frequency P _L is calculated by Equation 1 (44). Next, the MCU 14 compares whether the power P _L of the high frequency signal at the first lower band center frequency f _L is greater than the product of the first critical slope α and the reference power P _ref (step 46). At this time, when the power P _L of the high frequency signal at the center frequency of the first lower side band is smaller than the product of the first critical slope α and the reference power P _ref , the MCU 14 may compare with the carrier frequency of the current received high frequency signal. It is determined that the high frequency carrier frequency fc (0) (1) of the modulator 16 is not identical.

When the power P _L of the high frequency signal at the lower band center frequency in step 38 or 46 is greater than the product of the first threshold slope and the reference power P _ref , that is, the currently received high frequency signal is set to the modulator 16. In the case of including the primary lower band component for the carrier frequency, the MCU 14 performs the power P _D and the upper band upper limit reference frequency f _E of the high frequency signal at the set symbol rate and the upper band lower limit reference frequency f _D for the carrier frequency. In step 48, the power P _E of the high frequency signal is detected from the input frequency power distribution. For example, if R (0) = 3429, which is the symbol rate and the highest symbol rate shown in FIG. 4, and the carrier frequency is 1959 Hz, the upper band lower limit reference frequency f _D is 3600 Hz, and the upper band upper limit reference frequency f _E becomes 3750 kV. The received high frequency signal power P _U at the upper band center frequency f _U for the carrier frequency set in the modulator 16 is converted to the power P _D and P _E of the high frequency signal at the upper and lower band reference frequencies retrieved in step 48. Is calculated by the following Equation 3 (50th step).

P _U = P _D (1-K _U ) + K _U P _U (Equation 3)

In Equation 3, K _U is an experimentally obtained constant and is determined by Equation 4 below.

(Equation 4)

As in Equation 4, K _U is determined by the upper band lower limit reference frequency f _D and the upper band center frequency f _U obtained in the 48th step. In step 52, the power P _U of the high frequency signal at the upper band center frequency obtained in step 50 is greater than the product of the second critical slope β and the reference power P _ref (step 52). At this time, if the power P _U of the high frequency signal at the upper band center frequency obtained in the 50th step is smaller than the product of the second threshold slope β and the reference power P _ref , the MCU 14 determines that the carrier frequency of the received high frequency signal is It is assumed that it does not match the set carrier frequency.

The power P _L of the high frequency signal at the center frequency of the first lower band in step 46 is less than the product of the first critical slope α and the reference power P _ref , or the power of the high frequency signal at the center frequency of the upper band in step 52. When P _U is less than the product of the second critical slope β and the reference power P _ref , the MCU 14 determines that the carrier frequency of the current received high frequency signal and the high frequency carrier frequency fc (0) of the modulator 16 are set. Determining that there is a mismatch, the symbol rate R (i) and the corresponding carrier frequency fc (j) are manufactured to the next symbol rate and the low carrier frequency fc (0) that can be used for the symbol rate, and then the process returns to step 34. Go to step 54. If the current symbol rate in FIG. 4 is R (0) = 3429 and the carrier frequency is fc (1) = 1959 ㎐, the readjusted symbol rate R (i) and the carrier frequency fc (j) are respectively the next lower order. The symbol rate R (1) = 3200 and the low carrier frequency fc (1) (0) = 1829 kHz.

Finally, when the upper band average frequency power P _U is greater than the product of the upper limit threshold slope β and the reference frequency power P _ref in step 52, the MCU 14 may have a symbol rate and a carrier frequency to be applied to the current demodulator 16. If appropriate, the symbol rate and carrier frequency are determined as the symbol rate and carrier frequency of the modulator 16 (step 56).

As described above, the method for determining the optimal transmission symbol rate of the demodulator according to the present invention can analyze the power distribution of the received signal frequency and determine the symbol rate and the carrier frequency of the modulator so that the handshaking can be shortened by one time and the determination time. Can shorten. Accordingly, the method of determining the optimal transmission symbol rate of the modulator according to the present invention can minimize the transmission delay of data and further improve the reliability of the product.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (2)

Determining an average power at a carrier frequency of the received signal; Initial symbol rate and low-frequency carrier frequency initial setup, Searching for the lower / lower band upper / lower reference frequency power; Searching for the lower band center frequency power from the lower band upper / lower reference frequency power; A first comparison process of comparing the lower band center frequency power with a lower limit threshold of a frequency band including a signal source; Searching for upper / lower limit reference frequency power of the upper band according to the first comparison process; Searching for the center frequency power of the upper band from the upper / lower limit reference frequency power of the upper band; A third comparison process of comparing the upper band center frequency power with an upper limit threshold including a signal source; And determining the optimal symbol rate and the carrier frequency as a result of the third comparison process. The method of claim 1, And a symbol rate and carrier frequency adjustment process according to the third comparison process.