KR100315343B1 - Error estimating method and apparatus for channel modem for satellite communication system - Google Patents

Abstract

According to the present invention, when the burst mode is set in a channel modem of a satellite communication system, an estimated value is set by changing a phase of input voice data, and an error estimation initial value is generated based on the set estimated value. The present invention relates to an error estimation method and apparatus for a channel modem for a satellite communication system so that an estimation operation can be performed quickly.

In the present invention, the modulated frequency signal received through the channel modem is multiplied by a predetermined exponential function to shift the phase, sum and average each of the frequency shifted phase signals, obtain the magnitude thereof, and process the data into the transformed signal. The stored initial frequency data are stored in a predetermined unit and averaged, and the average value is output. When the output average value is compared with the set reference value for power detection, the initial value of the error estimate is generated. A value is set as a reference value for error estimation, and the error estimation initial value data is applied to the error estimating apparatus, and the error estimation operation is executed based on this.

Therefore, according to the present invention, as the error estimation reference value is set, the error estimation operation proceeds quickly, thereby reducing data processing time and the like.

Description

Error Estimation Method of Channel Modem for Satellite Communication System and Its Apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel modem of a communication system using satellites. In particular, in a burst mode, a phase of an input voice data is changed and an estimated value is set accordingly, and an initial error estimation value is set based on the set estimated value. The present invention relates to an error estimation method and apparatus for a channel modem for a satellite communication system that can generate an error estimation operation quickly.

1 is a block diagram showing an 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 512 kHz modulated signal by BPSK or QPSK modulation on the I, Q channel data output from the SDP 11, and 16 denotes a 512 kHz 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 frequency data corresponding to the corresponding frequency ID from the lookup table 19, and transmits the frequency synthesizer 13 and the received frequency synthesizer ( 14, a frequency signal (112.512 MHz ± 20 MHz, 112.384 MHz ± 20 MHz) having a variable range of 20 MHz is outputted from the frequency synthesizers 13 and 14.

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). ± 20 MHz) to detect a frequency signal of 384 KHz corresponding to a predetermined communication channel.

Meanwhile, in the satellite communication system, error components such as timing error and amplitude according to time delay generated by satellites are transmitted to the demodulator, and the demodulator performs an error estimation operation on the input data. do.

That is, the demodulator 18 performs an error estimation operation of data based on the carrier lock signal, compensates for the estimated error, and transmits the estimated error to the Viterbi decoder of the next voice / data processor (SDP).

In addition, when the burst mode is set to the burst mode, the demodulator 18 is enabled once when the carrier lock signal indicating that the error estimation has been performed to the allowable range for the system is input. The data is subsequently compensated for on the basis of the estimated error value and transmitted to the next stage.

However, after the carrier lock signal is enabled in the burst mode, the input data is estimated from the beginning, for example, from "0", to estimate the estimated error estimate at the time of enabling the carrier lock signal, thereby performing an error compensation operation. Will be performed.

Therefore, in the error estimation operation, since the reference estimation value is not set, the error estimation value is estimated from the beginning (for example, " 0 "), so that the time according to the error estimation becomes long, which causes a problem that the transmission speed of data is delayed. Done.

Accordingly, the present invention has been made in view of the above circumstances, and in the state in which the satellite communication system CHANNUM modem is set to the burst mode, the phase of the input voice data is changed to set an estimated value accordingly, and based on the set estimated value, It is an object of the present invention to provide an error estimation method and apparatus for a channel modem for a satellite communication system that can generate an error estimation reference value so that an error estimation operation can be quickly performed.

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

FIG. 2 is a block diagram showing an apparatus configuration for explaining an error estimation method of a channel modem for a satellite communication system according to an embodiment of the present invention. FIG.

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

11: Speech Data Processor

12: channel unit processor (CUP) 13: transmit frequency synthesizer

14: reception frequency synthesizer 15: modulator

16: intermediate frequency signal generator 17: intermediate frequency signal receiver

18: demodulation unit 19: lookup table

21: phase shift unit 22: data conversion unit

23: data processing unit 23a: processing storage unit

24: data comparison unit 25: drive value storage unit

26: initial value generating section 26a: linear coupling section

27: initial generation drive

An error estimation method of a channel modem for a satellite communication system according to the present invention for realizing the above object is error estimation and demodulation of a modulation frequency signal input from a down converter for downconverting an intermediate frequency signal into a predetermined frequency signal through an error estimating apparatus. A demodulation device for a channel modem for a satellite communication system, comprising: a phase shift step of shifting a phase by multiplying an input modulation frequency signal by a predetermined exponential function, summing and averaging respective frequency signals shifted in phase; A data conversion step of obtaining a size and processing the data into data, a data processing step of storing each averaged frequency data in a predetermined unit and outputting the average value, and comparing the output average value with a set reference value for power detection. Comparison step, error estimation initial stage based on the data comparison result And an error estimating step of applying the generated error estimation initial value data to an error estimating device and executing an error estimating operation based on the initial value generating step of generating a value.

In addition, if the average value output after the data comparison step is larger than the set power detection reference value, the initial phase for setting the initial value for error estimation by linearly combining the phase shifted frequency data based on the output average value. Characterized in that it comprises a value setting step further.

In addition, an error estimator for a channel modem for a satellite communication system according to the present invention for realizing the above object includes a phase shift unit for shifting a phase by multiplying an input modulation frequency signal by a predetermined exponential function, each phase shifted. A data converter that adds and averages frequency signals to obtain a magnitude thereof and processes the data into data, and a data processor that stores and averages each converted frequency data in a predetermined unit, and outputs the average value. A data comparison unit for comparing a reference value, an initial value generation unit for adding and averaging phase values of the frequency shifted phase signals, combining and generating an initial value for error estimation, and from the data comparison unit Including an initial generation driver for driving the initial value generating unit based on the output data Characterized in that configured.

The initial value generation unit may be configured to output the respective initial values for error estimation by linearly combining the frequency signals applied by phase shifting through the data conversion unit according to the comparison value output from the data comparison unit.

That is, according to the present invention having the above-described configuration, by generating an initial value as a reference for error estimation and applying it to the error estimating apparatus, the error estimation operation proceeds quickly, thus reducing the processing time of data and the like. do.

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

FIG. 2 is a block diagram illustrating an apparatus for explaining an error estimation method of a channel modem for a satellite communication system according to an embodiment of the present invention.

In FIG. 2, reference numeral 21 denotes a phase shift unit for shifting a phase by multiplying an input modulation frequency signal by a predetermined exponential function, so that one frequency input delays the phase by 90 degrees and the other by 90 degrees. 22 is a data converter which adds and averages each phase shifted frequency signal to obtain its magnitude and processes the data into data. 23 is a data processor which stores and averages each converted frequency data in a predetermined unit and outputs the average value. In this case, the sum of the averaged magnitude values output and applied from the data converter 22 is stored up to a predetermined unit, for example, four times through the processing storage unit 23a, and then the averages of the four times are averaged. The average value is output.

In addition, reference numeral 24 is a data comparison unit for comparing the average value output from the data processor 23 with the set reference value (POWER THRESHOLD) for power detection and outputting the compared value when the reference value is larger than the reference value. The result value processed by the processor 23 is temporarily stored, and when the compared value is applied from the data comparator 24, the result value stored as the drive value of the initial generation driver 27 to be described later. It is a drive value storage unit to output.

In addition, reference numeral 26 adds and averages phase values of respective frequency signals shifted in phase by the phase shift unit 21, and linearly combines the linear values through the linear combiner 26a to calculate an initial value for error estimation. An initial value generation unit for generating and outputting, and 27 is an initial generation driving unit for driving the initial value generation unit 26 based on the data output from the data comparison unit 24.

Next, the operation of the apparatus according to the first embodiment of the present invention having the above-described configuration will be described.

First, in the channel modem for the satellite communication system, the signal transmitted from the transmitting end passes through a demodulator to demodulate the signal transmitted from the original transmitting end in synchronization with the system through the RF end and the IF end of the receiving end. The received signal is demodulated by compensating for the frequency error on the satellite, the time error in sampling, and the error portion of the signal size.

Accordingly, the detailed operation of the demodulator is first, ± 70MHz received at the IF stage is down-converted to 384KHz through a down converter (not shown), and the 384KHz signal is applied to an encoder (not shown) to sample 512KHz. Sampled on click.

Thereafter, the sampled signal is quantized and input to the apparatus according to the present invention. The input frequency signal is multiplied by a predetermined exponential function through the phase shifter 21, for example, one phase is 90 degrees. The other quickly shifts 90 degrees later. Equation 1 below represents the received and input signal as an equation, and Equation 2 and Equation 3 describe the input signal as described above. The phase shifts are shown in FIG.

[Equation 1]

[Equation 2]

[Equation 3]

The frequency shifted phase signal is applied to the initial value generation section 26 and the data conversion section 22. The initial value generation section 26 operates according to the driving signal of the initial generation driving section 27. Until the driving signal is applied to the standby state, the data converter 22 performs a power sensing operation for generating an initial value by calculating according to the applied frequency-shifted frequency signal.

That is, the original frequency signal inputted to the data converter 22 and the frequency signal of each phase shift are calculated according to the following equations (4), (5) and (6).

[Equation 4]

[Equation 5]

[Equation 6]

When the sum is obtained as described above, the size is calculated according to the following Equation 7, Equation 8 and Equation 9, and then output.

[Equation 7]

[Equation 8]

[Equation 9]

Each size data output as described above is applied to the data processor 23 to be added or subtracted as shown in Equation 10 below.

[Equation 10]

Then, the frequency data processed as described above is stored in the processing storage unit 23a in the calculated error information each time the above-described process, i.e. , error information calculation operation on the input signal is executed, and the processing storage unit 23a. ) Stores this error information up to four times and outputs the average of these four times.

In addition, the average value output through the data processor 23 is stored in the drive value storage unit 25 and thereafter the magnitude value of the amplitude according to whether or not the output comparison value of the data comparator 24 is applied. Will be printed).

Subsequently, the average value output from the data processor 23 is applied to the non-inverting terminal (+) of the data comparator 24, and the data comparator 24 inputs the input average value to the inverting terminal (-). Compared with the power data for power detection (POWER THRESHOLD) and outputs the comparison value.

For example, assuming that the storage capacity of the calculation result of the processing storage unit 23a is 32 data, the data comparison unit 24 when the process of receiving, summing and averaging the data one by one is larger than the reference data for power detection only up to 20 data. ) Will print the comparison value.

In addition, when the data comparison unit 24 outputs the comparison value, the data comparison unit 24 generates and outputs a SOB (Start Of Burst) pulse signal which is a start signal of the burst, and the output comparison value is an initial generation driver 27. The initial value generating unit 26 is driven by being applied to.

Therefore, the initial value generating unit 26 calculates the initial frequency signals by applying the frequency signals applied from the phase shift unit 21 in the standby state according to the following equations (11), (12), (13) and (14). Perform linear combination to extract values.

[Equation 11]

[Equation 12]

[Equation 13]

[Equation 14]

The frequency signals output according to Equations 11, 12, 13, and 14 are calculated by the linear combiner 26a to capture frequency shifts or to initial values for timing error and phase error extraction. Equations 15, 16, and 17 are output as shown.

[Equation 15]

[Equation 16]

[Equation 17]

On the other hand, the frequency value, the timing value, and the phase value output from the initial value generator 26 are applied to the error estimating apparatus so that the error estimation operation is executed based on the applied initial value.

Therefore, as the reference value for the error estimation is set, the error estimating apparatus can execute the error estimation operation in a short time based on this.

That is, according to the embodiment, a channel modem for a satellite communication system capable of performing an error estimation operation in a short time by applying a reference value for error estimation to the error estimating apparatus by performing a phase shift on the received and input frequency signals, respectively. The error estimation method and apparatus can be realized.

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, by generating an initial value which is a reference for error estimation and applying it to the error estimation apparatus, the error estimation operation proceeds quickly, thereby reducing the processing time of data and the like.

Claims (4)

In the demodulation device of the channel modem for satellite communication system for error estimation, demodulating and outputting a modulated frequency signal input from the down-converter downconverting the intermediate frequency signal into a frequency signal of a predetermined level through an error estimator, A phase shift step of generating a positive phase shift signal and a negative phase shift signal by performing a predetermined level phase shift with respect to an input modulation frequency signal toward a positive (+) side and a negative (-) side, respectively; A data conversion step of generating respective magnitude data for a positive phase shift signal, a negative phase shift signal, and an input modulation frequency signal; A data processing step of calculating error information on an input modulation frequency signal based on each size data generated in the data conversion step, storing a predetermined number of calculated error information, and calculating an average error value of a plurality of stored error information; A data comparison step of comparing the average error value calculated in the data processing step with a preset reference value, A reference value generation step of generating a predetermined error estimation reference value based on the comparison result in the data comparison step, An error estimation initial value generation step of generating a predetermined error estimation initial value based on the error estimation reference value generated in the reference value generation step; And an error estimating step of performing an error estimating using the error estimating initial value generated in the error estimating initial value generating step as a starting value. The method of claim 1, If the average value output after the data comparison step is larger than the set power detection reference value, an initial value is set to linearly combine each phase shifted frequency data based on the output average value and set it as an initial value for error estimation. An error estimation method of a channel modem for a satellite communication system, characterized in that it further comprises a step. In the demodulation device of the channel modem for satellite communication system for error estimation, demodulating and outputting a modulated frequency signal input from the down-converter downconverting the intermediate frequency signal into a frequency signal of a predetermined level through an error estimator, A phase shift unit configured to generate a positive phase shift signal and a negative phase shift signal by performing a predetermined level phase shift on a positive (+) side and a negative (-) side with respect to an input modulation frequency signal; A data converter for generating respective magnitude data of the positive and negative phase shifted signals and the input signal applied from the phase shifter; A data processor for calculating error information on an input modulation frequency signal based on the size data from the data converter, storing a predetermined number of calculated error information, and calculating an average error value of a plurality of stored error information; A data comparing unit comparing the average error value applied from the data processing unit with a preset reference value; A reference value generation unit for generating a predetermined error estimation reference value based on a comparison result applied from the data comparing unit; A predetermined error estimation is performed by adding / averaging / combining the phase values of the positive and negative phase shift signals and the input modulation frequency signal applied from the phase shift unit based on the error estimation reference value applied from the reference value generator. An initial value generating unit generating an initial value, And an error estimator for performing a predetermined error estimation on an input modulation frequency signal using the initial value of the error estimation applied from the initial value generation unit as a start value. . The method of claim 3, wherein The initial value generating unit performs a phase shift through the data converter and linearly combines the applied frequency signals according to the comparison value output from the data comparator, respectively, and outputs each of the initial values for error estimation. Error estimator for channel modem.