KR19990056909A - Error Estimation in Channel Modem Demodulation System for Satellite Communication System - Google Patents

Abstract

The present invention demodulates input data to estimate an error and outputs I, Q data that compensates for the error, and stores a predetermined number or more of the previous error estimation values based on an average value of the error estimation values when the error estimation of I, Q data is performed. The present invention relates to an error estimating method in a demodulator of a channel modem for a satellite communication system that estimates an error of data to be input thereafter, wherein the input frequency signal is demodulated into I, Q data, An apparatus for demodulating a channel modem for a satellite communication system for estimating / compensating an error with respect to demodulated data and outputting the error, comprising: an error detecting step of detecting an error component generated through satellites in the I and Q demodulated data; An error estimating step of estimating the error data detected in the step on the basis of the average value of the previous error estimating value; An error compensating step for compensating for the error of the I, Q data inputted to the data, updating the error estimation value estimated in the error estimation step to an error estimation information storage unit, and storing an error estimation information storing the oldest error estimation value; And an average error estimate calculation step of calculating an average error estimate value including the updated error estimate value in the error estimation information storage step.

Description

Error Estimation in Channel Modem Demodulation System for Satellite Communication System

The present invention relates to a channel modem of a communication system using satellites. In particular, in estimating an error by demodulating input data and outputting I, Q data that compensates for the error, the previous error estimation value at the time of error estimation of I, Q data is estimated. The present invention relates to an error estimating method in a demodulation device for a channel modem for a satellite communication system which stores a predetermined number and estimates an error of data to be subsequently input based on an average value of the error estimation values.

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.

On the other hand, the demodulator demodulates a signal of 384KHz input modulated by the QPSK method into I, Q data, and outputs the demodulator by accurately estimating an error value generated through satellites during I, Q data output. Based on the estimated error value, it is compensated for and output.

However, when the error of the input data is estimated by the general demodulator, the current phase error value is estimated based on the error estimation value of the data immediately before the input data, that is, the rate of change of the previous data. If the value suddenly increases or decreases, a problem arises in that it takes a lot of time to estimate the error.

Accordingly, the present invention was created in view of the above circumstances, and when a phase error estimation of the input data is performed, the previous error estimation values are stored in a plurality, and the error value of the currently input data is estimated based on the average error estimation value. In addition, the object of the present invention is to provide an error estimation method in a demodulation device of a channel modem for a satellite communication system that can reduce the error estimation time according to the error estimation.

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.

*** 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,

59A: error detector, 59B: error compensator,

59C: Error estimation information storage unit.

The error estimation method in the demodulation apparatus for the channel modem for satellite communication system according to the present invention for achieving the above object, demodulating the input frequency signal of the predetermined level into the I, Q data, the I, Q demodulated data A demodulation device for a channel modem for a satellite communication system for estimating / compensating for an error and outputting the error, comprising: an error detection step of detecting an error component generated through satellites in the I and Q demodulation data, and in the error detection step An error estimating step of estimating the detected error data based on an average value of the error estimating value, an error compensating step of compensating errors of the input I and Q data based on the error estimating value estimated in the error estimating step, and the error estimating step An error estimating information storing step of updating the error estimating value estimated in the error estimating information storage unit and deleting the oldest error estimating value, and the error estimating estimation Characterized in that configured to include the average error estimate calculation step of calculating a mean error estimates, including the updated error estimate in a storage step.

According to the error estimating method according to the present invention having the above-described configuration, even when an error value of I and Q data input to the error estimator is rapidly changed, the error is based on the average error estimation data of a predetermined number of previous error estimation data. By making the estimation, not only the error estimation time is reduced, but also when the previous error estimation value is incorrectly estimated, it is less affected by the wrong error estimation value, thereby reducing the error rate (BER) generated thereby.

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 50 according to the present invention.

In the figure, reference numeral 51 denotes a down-converted intermediate frequency signal transmitted from an intermediate frequency terminal (IF stage) to a band of 384 KHz based on a synchronization signal applied from an RX synchronizer (not shown). A converter 52 is an encoder for sampling the 384 KHz signal applied from the down converter 51 based on a sampling frequency of 512 KHz, and 53 is a quantizer for quantizing 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, which comprises an error detector 59A for detecting an error component of the I, Q data applied from the decimator 58, in particular a satellite error component, from the error detector 59A. An error compensator for compensating the error components of the input I and Q data based on the previous error estimation value applied from the error estimation information storage unit 59C to be described later, that is, the average data of the previous error variation rate ( 58B) and an error estimation information storage unit 59C for storing, for example, about three previous error estimation values, that is, error variation rates.

That is, according to the present invention as described above, the error estimator 59 stores the previous error estimation value, that is, the previous error variation rate in the error estimation information storage unit 59C, and at the time of error estimation of data input thereafter, The error is estimated based on the average value of the previous error estimation values stored in the error estimation information storage 59C. Then, by deleting the previous error estimate value and storing the currently estimated error value, the current error estimate value affects the error estimate value to be applied to the next data.

Therefore, even when the error values of the I and Q data input to the error estimator 59 suddenly change, the error estimation time is reduced by making the error estimate based on the average error estimation data of the predetermined number of previous error estimation data. In addition, if the previous error estimate is incorrectly estimated, this error error estimate is less affected, thereby reducing the error rate (BER).

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, even when an error value of I and Q data inputted to an error estimator is suddenly changed, the error estimation is performed by estimating the error based on the average error estimation data of a predetermined number of previous error estimation data. Not only is the time reduced, but when the previous error estimate is incorrectly estimated, it is less affected by the wrong error estimate, thereby reducing the error rate (BER) that is generated.

Claims (2)

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 an error component generated through satellites in the I and Q demodulated data; An error estimating step of estimating the error data detected in the error detecting step based on an average value of the previous error estimation values, An error compensating step of compensating for errors in the input I and Q data based on the error estimation value estimated in the error estimation step; An error estimation information storage step of updating the error estimation value estimated in the error estimation step to an error estimation information storage unit and deleting the oldest error estimation value; And an average error estimate calculation step of calculating an average error estimate value including the updated error estimate value in the error estimation information storing step. The method of claim 1, The error estimation information storing step includes storing the previous error estimation value of a predetermined number or more, and shifting the previous error estimation value when the updated error estimation data is input, thereby deleting the oldest error estimation value. Error Estimation Method in Modem Demodulator.