KR100262154B1 - Method for generating data transmission signal in a demodulator of channel modem for satellite communication system - Google Patents

Abstract

PURPOSE: A method of generating data transmission signal in a demodulator of a channel modem for satellite communication system is provided to generate a data transmission signal if the error rate of I, Q data is below a predetermined rate in case of making up an error according to the error prediction of an input data and send the I, Q data to the next unit on the basis of the signal received. CONSTITUTION: In the demodulator of a channel modem for a satellite communication system which demodulates a frequency signal of a predetermined level into I, Q data and outputs them after predicting/making up an error with respect to the I, Q data, in the first step, a timing error, amplitude error and phase error generated through the satellite are detected out of the I, Q demodulated data. In the second step, errors of the I, Q data are made up on the basis of the error data detected in the first step. In the third step, out of the error data made up in the error make up step, an average error rate is calculated with respect to the I, Q data input. The error rate is compared to an error rate threshold data. In the last step, If the error rate is lower than the threshold data, a data transmission signal is generated.

Description

Data transmission signal generation method in channel modem demodulation device for satellite communication system

The present invention relates to a channel modem of a communication system using satellites, and more particularly, demodulates input data to estimate an error and transmits I, Q data that compensates for the error. The present invention relates to a method for generating a data transmission signal in a demodulation device for a channel modem for a satellite communication system.

With the recent rapid development of communication technology, wireless communication is being spread and activated to transmit and receive voice signals or data through airwave transmission network rather than the conventional wired network, so that subscribers located at remote sites can perform mutual communication through satellites. Satellite communication is becoming more and more common.

1 is a block diagram showing the internal configuration of a channel modem for a general satellite communication system.

In the figure, reference numeral 11 denotes a voice / data processor that performs an interface function between the UPH bus and the MPH bus and the channel unit processor 12, which will be described later, and specifically processes voice and data transmitted and received through an airwave transmission network. Data Processor (hereinafter referred to as SDP), and 12 is a channel unit processor (hereinafter referred to as CUP) that controls the overall configuration of the channel modem.

Further, reference numeral 13 denotes a transmission frequency synthesizer for synthesizing and outputting a predetermined frequency signal for generating an intermediate frequency signal, for example, 112.512 MHz ± 20 MHz, based on the control data from the channel unit processor 12, 14 is a reception frequency synthesizer for synthesizing and outputting a predetermined frequency signal for receiving an intermediate frequency signal, for example, 112.384 MHz ± 20 MHz, based on the control data from the channel unit processor 12.

Reference numeral 15 denotes a modulator for outputting a 512KHz modulated signal by BPSK or QPSK modulating the I, Q channel data output from the SDP 11, and 16 denotes a 512KHz output from the modulator 15. An intermediate frequency generator generates and outputs an intermediate frequency signal of 70 MHz ± 20 MHz based on a modulation signal and a frequency of 112.512 MHz ± 20 MHz and a reference frequency of 42 MHz applied from the transmission frequency synthesizer 13.

Reference numeral 17 denotes an intermediate frequency signal for outputting a modulated signal of 384 KHz based on the received 70 MHz ± 20 MHz intermediate frequency signal, the frequency of 112.384 MHz ± 20 MHz applied from the receiving frequency synthesizer 14 and the reference frequency of 42 MHz. A demodulator 18 is a demodulator for demodulating and outputting I and Q channel data from a 384 KHz modulated signal applied by the intermediate frequency signal receiver 17, and 19 stores frequency data for each frequency ID. Look-up Table.

In the above configuration, when a predetermined frequency ID is input through the UPH bus, the CUP 12 reads the frequency data corresponding to the corresponding frequency ID into the lookup table 19 to transmit the synthesizer 13 and the receive frequency synthesizer ( 14), the frequency signal (112.512 MHz ± 20 MHz, 112.384 MHz ± 20 MHz) having a variable range of 20 MHz is output-controlled from the corresponding frequency synthesizer.

In the intermediate frequency signal generator 16, a 20 MHz variable is mixed by mixing a frequency signal (112.512 MHz ± 20 MHz) applied from the transmission frequency synthesizer 13 to a 512 KHz modulated signal output from the modulator 15. An intermediate frequency signal (70 MHz ± 20 MHz) having a range is generated, and in the intermediate frequency signal receiving unit 17, a frequency signal having a variable range of 20 MHz is again applied to the intermediate frequency signal having a variable range of 20 MHz (112.384 MHz). By mixing ± 20 MHz), a frequency signal of 384 KHz corresponding to a predetermined communication channel is detected.

Meanwhile, the demodulator demodulates an input signal of 384KHz into I, Q data, and outputs the demodulated part by estimating an error generated through satellites when outputting I, Q data and compensating it for output.

However, since the time required for the error estimation of the input data depends on how much the error of the input data is, the error compensation according to the error estimation of the input data is executed, and then the data is the next voice. You need a signal that tells you when to send it to the data processor.

In addition, since the error recovery capability varies depending on the performance of the system, the error estimation signal indicating the data transmission time when it is determined that the error rate (Bit Error Rate) at the time of error estimation of I, Q data is less than a predetermined value. Will be needed.

Accordingly, the present invention was created in view of the above circumstances, and when the error compensation according to the error estimation of the input data is executed and the error rate of the I and Q data is determined to be less than or equal to the predetermined value, the data transmission signal is generated. The purpose of the present invention is to provide a method for generating a data transmission signal in a demodulator of a channel modem for a satellite communication system that transmits I, Q data to the next stage based on this signal.

1 is a block diagram showing the internal configuration of a channel modem for a general satellite communication system.

2 is a block diagram showing an internal configuration of a demodulation device 50 in a channel modem for a satellite communication system according to the present invention.

3 is a view showing a data transmission signal generation process of the data transmission signal generator 106 shown in FIG.

*** Explanation of symbols for the main parts of the drawing ***

50: demodulation device, 51: down converter,

52: encoder, 53: quantizer,

54: demodulation section, 55: low pass filter (LPF),

56: synthesizer, 57: matching filter,

58: data message, 59: error estimator,

60: data transmission signal generator, 101: timing error detection unit,

102: amplitude error detection unit, 103: phase error detection unit,

104: error compensator, 105: error rate comparator,

106: data transmission signal generator.

In the demodulation device for the channel modem for satellite communication system according to the present invention for achieving the above object, the data transmission signal generation method, in addition to demodulating the input frequency signal of the predetermined level into I, Q data, I, Q A satellite modem system demodulation device for estimating / compensating an error with respect to demodulated data and outputting the detected signal, comprising: detecting a timing error, an amplitude error, and a phase error generated through satellites in the I and Q demodulated data; An error detection step, an error compensation step of compensating for errors in the input I and Q data based on the error data detected in the error detection step, and an error compensation step of the error data compensated in the error compensation step for the input I and Q data. An error rate calculation step of calculating an average error rate, an error rate comparison step of comparing the error rate calculated in the error rate calculation step with error rate threshold data, and the error rate comparison step If the error rate calculated in the error rate is less than the threshold data, characterized in that configured to include a data transmission signal generating step for generating a data transmission signal.

In the demodulation device according to the present invention having the above-described configuration, when error compensation is performed for a predetermined value or more, which is allowed by the system, the error is received for the next data without going through an error estimation process for the input data. Since the estimation process is performed, the processing time of the data can be shortened.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a block diagram showing an internal configuration of a demodulation device according to the present invention.

In the figure, reference numeral 51 denotes a down converter that down-converts the intermediate frequency signal transmitted from the intermediate frequency stage (IF stage) to a band of 384 KHz based on a synchronization signal applied from an RX synchronizer (not shown). Where 52 is an encoder that samples the 384 KHz signal applied from the downconverter 51 based on a sampling frequency of 512 KHz, and 53 is a quantizer that quantizes the 128 KHz sampled signal applied from the encoder 52.

Reference numeral 54 is a demodulation unit for synchronously detecting the 128 KHz signal transmitted from the quantizer 53 on the basis of the oscillation frequency applied from the 128 KHz oscillator and converting the signal band to 0 Hz. A low pass filter (LPF) that performs baseband filtering around a reference frequency (0 Hz). The signal passing through the low pass filter 55 is an original signal before both sides of the band are removed and modulated. Q data is output.

Reference numeral 56 denotes a synthesizer which synthesizes and outputs a signal applied from the low pass filter 55 and a signal applied through the error estimator 59 to be described later.

On the other hand, reference numeral 57 is a matched filter for filtering to a band having a predetermined filter coefficient value in order to detect the sampling instant value of the signal applied from the synthesizer 56, which is a route selected by a modulator (not shown). By convoluting the same root-laid cosine function with the signal applied by the lased cosine function, the sampling instant value of the applied signal is detected, and a predetermined carrier lock is generated from the carrier lock signal generator 60 to be described later. When the signal is applied, the input data is output to the voice / data processor (SDP).

Also, reference numeral 58 denotes a decimator which detects the data applied from the matching filter 57 at predetermined intervals, which has a predetermined size between the information data in a modulator (not shown) on the transmitting side. As a corresponding process of the receiving side in inserting the dummy data and performing the modulation process, if the size of the dummy data is one bit, the decimator 58 of the demodulator is defined to have a detection interval of '2'.

Further, reference numeral 59 detects an error component of data applied from the decimator 58, applies the detected signal to the synthesizer 56, and matches the timing error component data along the satellite. An error estimator applied to the filter 57, and 60 denotes data for applying a data transmission signal to a next voice / data processor when the error rate BER according to the error estimation result of the error estimator 59 is less than or equal to a predetermined value. Transmission signal generator.

Meanwhile, the voice / data processor receives only data after the data transmission signal is applied.

3 is a diagram schematically showing a signal generation process of the data transmission signal generator 60 shown in FIG.

In FIG. 3, reference numeral 101 denotes a timing error detector which detects a predetermined timing error from data fed back from the decimator 58 of FIG. 2, and 102 denotes a predetermined value from the data fed back from the decimator 58. An amplitude error detection unit 103 for detecting an amplitude error of the phase error detection unit 103 is a phase error detection unit for detecting a predetermined phase error in the data fed back from the data meter 58.

Further, reference numeral 104 denotes an error compensator for compensating for errors in data input based on the error data applied from the timing error detector 101, the amplitude error detector 102, and the phase error detector 103, respectively. The error rate is summed and averaged, and the calculated error rate is applied to the error rate comparing unit 105 which will be described later.

On the other hand, reference numeral 105 is an error rate comparison unit for comparing the error rate data applied from the error compensation unit 101 with the set error rate (BER) threshold data, which is an error rate applied from the error compensation unit 101 When the threshold data is smaller than the set error rate threshold data, a predetermined control signal is applied to the next stage. The error rate threshold data set in the error rate comparison unit 105 can be arbitrarily set by an operator according to the performance of the system. For example, the error rate threshold data is set to 0.7.

That is, the error rate comparison unit 105 stores error estimate values of input data, for example, 64 or 128 error estimate values, and subsequently stores error estimate values equal to or less than a predetermined number of error rates. The control data is applied to the data transmission signal generator 106 to be transmitted.

On the other hand, reference numeral 106 denotes a data transmission for transmitting a data transmission signal, for example, a carrier lock signal, to the matching filter 57 based on the predetermined control signal from the error rate comparison unit 105. It is a signal generator.

That is, according to the present invention as described above, if the error component of the input data is detected and compensated, and it is determined that the input data has an error rate below a certain value by the above-described error compensation, By applying to the voice / data processor SDP, I and Q data are transmitted.

Therefore, when the demodulation device performs error compensation on the input data more than a predetermined value, the error estimation process is performed on the next data without going through an error estimation process on the input data. The processing time of data can be shortened.

In addition, this invention is not limited to the said Example, It can variously deform and implement within the range which does not deviate from the technical summary of this invention.

As described above, according to the present invention, when error compensation is performed for a predetermined value or more, which is allowed by the system, the error estimation process is performed on the next data without performing an error estimation process on the input data. As a result, the processing time of data can be shortened.

Claims (1)

A demodulation apparatus for a channel modem for a satellite communication system that demodulates an input frequency signal of a predetermined level into I and Q data, and estimates and compensates an error for the I and Q demodulated data. An error detection step of detecting a timing error, an amplitude error, and a phase error generated through the satellites in the I and Q demodulated data; An error compensating step of compensating for errors in the input I and Q data based on the error data detected by the error detection step; An error rate calculation step of calculating an average error rate of the error data compensated in the error compensation step with respect to the input I and Q data; An error rate comparing step of comparing the error rate calculated in the error rate calculating step with error rate threshold data; When the error rate calculated in the error rate comparison step is smaller than the error rate threshold data, data transmission signal generation step for generating a data transmission signal, characterized in that it comprises a data transmission signal generation step in the demodulator of the channel modem for satellite communication system Signal generation method.

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