JP2000332660A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver capable of minimizing the deviation of symbol timing and executing re-equalization even in a short training period. SOLUTION: In the short training, a symbol timing decision part 112 outputs four different input timing to an adaptive equalizer 106, the input timing most close to a repeat pattern is decided from outputs of the equalizer 106 which correspond to four different kinds of input timing and the input timing is used as symbol timing for obtaining a succeeding output from the equalizer 106.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus which is used for a facsimile or the like and has a function of demodulating a modulated signal and an adaptive automatic equalizer.

[0002]

2. Description of the Related Art The carrier of FAX communication is an analog line (telephone line). To connect a digital device to the analog line, a digital signal handled by the digital device and
A modem (modulator / demodulator) is required as a means for mutually converting analog signals that can be handled by a telephone line.

A modem is a device having a means for modulating a digital signal into an analog carrier and a means for demodulating an analog carrier into a digital signal, and the transmission speed has been remarkably improved by the development of technology.

[0004] The transmission quality of a modem depends on the nature of the automatic equalizer. The automatic equalizer is provided on the data receiving side of the modem, and removes a line distortion component from a signal distorted on a transmission line to obtain an original transmission signal. Automatic equalization works from the training period immediately before the transmission period of the data to be transmitted, during which the transceiver transmits a predefined signal.

[0005] Even in the data transmission period following the training period, the automatic equalizing operation is continued in order to follow the change in the line condition. At this time, the fluctuation of the line characteristics is not large, and the performance such as the automatic equalization is the performance during the training period.

[0006] ITU-T Recommendation T. As specified in 30, FAX uses high-speed modulation / demodulation for image data to be transmitted, and low-speed modulation / demodulation for procedural signals other than image data. Therefore, in fax communication,
A modem including two types of high-speed / low-speed modems is used, and the modems are switched and used during data transfer.

For example, in the case of G3 FAX, high speed is 1
4400 bps (modulation and demodulation means of ITU-T Recommendation V.17) and low speed of 300 bps (modulation and demodulation means of ITU-T Recommendation V.21) are used. When switching between high speed and low speed, in order to save time for a high-speed training period, long training is first performed after call connection, and short training is performed after the second connection.

[0008] The filter coefficients at the time of long training of the automatic equalizer constituted by the transversal filter are stored and used for automatic equalization of short training.

[0009]

However, in such a modem that intermittently repeats long training and short training to transfer data,
During short training, the automatic equalization performance may deteriorate for the following reasons.

The signal point at the output of the automatic equalizer becomes a coordinate point on the layout, and is decoded according to the amplitude and phase assigned as a symbol. When the long training is successful, if the output of the automatic equalizer deviates from the symbol timing, a re-equalization operation is required. If the deviation is large, there is a problem that reliable equalization cannot be guaranteed in a short training period, and automatic equalization performance deteriorates.

The present invention has been made in view of the above, and an object of the present invention is to provide a receiving apparatus capable of minimizing a symbol timing shift and performing re-equalization even in a short training period.

[0012]

In order to achieve the above object, the invention according to claim 1 includes a built-in automatic equalizing means for equalizing distortion of a transmission path of a received signal, and performs long training and short training. In the receiving device that executes
At the time of receiving the repetition pattern of the short training signal, a timing phase unit that generates a plurality of input timings having different timing phases and outputs the input timings to the automatic equalizing unit, and an input having different timing phases output from the timing phase unit. Holding means for holding the output of the automatic equalizing means corresponding to each timing up to one symbol before, and current output of the automatic equalizing means and the holding means corresponding to the mutually different input timings of the timing phase. Symbol timing determining means for determining an optimum symbol timing from input timings having different timing phases based on a combination with the held output of the automatic equalizing means one symbol before. .

According to a second aspect of the present invention, in the receiving apparatus according to the first aspect, the automatic equalizing means includes a transversal filter.

According to a third aspect of the present invention, in the receiving apparatus according to the first aspect, the symbol timing determination unit determines a current output of the automatic equalization unit corresponding to the reception signals having different timing phases. The distance from the output of the automatic equalizing unit one symbol before, which is held in the holding unit, is determined, and the optimum symbol timing is determined from the input timings having different timing phases.

According to a fourth aspect of the present invention, in the receiving apparatus according to the first aspect, the symbol timing determining means includes an output of the automatic equalizing means corresponding to input timings different from each other in the timing phase. The distance from the signal point of the repetitive pattern is determined, and the optimum symbol timing is determined from the input timings having different timing phases.

According to a fifth aspect of the present invention, there is provided a receiving apparatus which includes a built-in automatic equalizing means for equalizing distortion of a transmission path of a received signal and performs long training and short training. At the time of reception, a plurality of input timings different in timing phase are generated and output to the automatic equalizing means, and a plurality of input timings different in timing phase input from the timing phase means are respectively corresponded. Holding means for averaging the output of the automatic equalizing means for every other symbol over a predetermined time, and holding two sets of average values for each of a plurality of input timings having mutually different timing phases; and Different input timings of the timing phases based on the two sets of average values held. A symbol timing determination means for determining an optimum symbol timing from among those having a.

According to a sixth aspect of the present invention, in the receiving apparatus according to the fifth aspect, the symbol timing determining means determines a distance between the two sets of average values of the output of the automatic equalizing means. Thus, the optimum symbol timing is determined from the input timings having different timing phases.

According to a seventh aspect of the present invention, in the receiving apparatus according to the fifth aspect, the symbol timing determining means is configured to output the output of the automatic equalizing means corresponding to input timings different from each other in the timing phase. The distance between the average value and the signal point of the repetition pattern is determined, and the optimum symbol timing is determined from the input timings having different timing phases.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, a receiving apparatus according to the present invention will be described below (Embodiment 1), (Embodiment 2)
Will be described in order.

(Embodiment 1) A receiving apparatus according to Embodiment 1 will be described with reference to FIGS. FIG. 1 is a block diagram illustrating a configuration example of a modem of a receiving device (receiving side).
FIG. 2 is a diagram showing formats of the long training signal and the short training signal. FIG. 3 is an explanatory diagram for explaining repetition patterns A and B of segment 1 of the long training signal and the short training signal.

In FIG. 1, reference numeral 100 denotes a modem. The modem 100 is input from an A / D converter 101 for converting a signal received from a transmission line into a digital signal, and an A / D converter 101. A complex processing section 102 for performing a complex processing on a digital signal, and a baseband filter (BBF) 103 for removing unnecessary high-frequency components and the like included in a signal received from a transmission path and removing intersymbol interference.
A fixed equalizer 104 composed of a first-order IIR filter for correcting the loss of the subscriber line, an automatic gain controller (AGC) 105 for automatically adjusting the signal level, An adaptive equalizer 106 that compensates for the distortion received by the adaptive equalizer 106, and a phase synchronization unit 107 that compensates for the frequency shift and phase fluctuation included in the signal output from the adaptive equalizer 106.

The modem 100 uses the reception points on a two-dimensional signal constellation (constellation of signal points) having two axes of a real number axis and an imaginary number axis to determine the state of the convolutional encoder on the transmission device side. A decision / decoder (maximum likelihood decoding) that performs Viterbi decoding (maximum likelihood decoding) using an error (error signal e) between the reception point and the decision point and decodes the signal (maximum likelihood decoding) Likelihood decoding unit) 108 and a descrambler 10 for restoring a signal randomized by scrambling.
9, an error calculator 110 for calculating the error signal e,
It includes a repetitive pattern detector 111 that detects a repetitive pattern that is always sent at the beginning of the training signal, and a symbol timing determination unit 112 that determines the optimal symbol timing.

Next, the operation of the receiving apparatus having the above configuration at the time of short training will be described. As described above, for example, in the case of G3 FAX, the high speed is 14400 bps.
(Modem of ITU-T Recommendation V.17), 30 for low speed
0 bps (modulation / demodulation means of ITU-T Recommendation V.21) is used. When switching between high speed and low speed, in order to save time for the high-speed training period, perform long training at the beginning after connecting the call,
Short training is conducted after the second time. Adaptive equalizer 106 composed of a transversal filter
The filter coefficients at the time of long training shown in FIG. 2A are stored and used for automatic equalization of short training shown in FIG. 2B.

V. In 17 Recommendations, the symbol timing is specified as 2400 baud. Here, the sampling timing is set to be four times the sampling timing. A / D converter 1
The operation from 00 to the AGC 108 is performed at the sampling timing. Since the adaptive equalizer 110 operates at twice the symbol timing, one data is input for every two samples to the filter.

Further, V.I. In the 17th recommendation, as shown in FIG. 2, the symbol time used for training of the adaptive equalizer 106 is specified to be 2976 symbols for long training and 38 symbols for short training.

At the time of short training, V.V. After detecting the repetition pattern that is the segment 1 signal in the 17 recommendations, the symbol timing determination unit 112 generates four types of input timings that can be changed within one symbol time, and outputs them to the adaptive equalizer 106.

After the data is filled in the delay line of the filter, the adaptive equalizer 106 outputs outputs respectively corresponding to four types of data input timings to the symbol timing determination section 112. The symbol timing determination unit 112 holds the output of the adaptive equalizer 106 up to one symbol before, obtains two symbols of outputs corresponding to the four types of data input timings of the adaptive equalizer 106,
The optimum symbol timing is determined from the four types of input timings to the adaptive equalizer 106. Here, since the filter coefficient of the adaptive equalizer 106 whose symbol timing has been sufficiently adjusted at the time of long training is used, two symbols correspond to the repetition pattern A shown in FIG.
And close to B.

That is, the symbol timing determination unit 11
2 determines the data input timing at which the output corresponding to each of the four types of data input timings of the adaptive equalizer 106 is closest to the repetition patterns A and B. Specifically, for example, the distance between the output of the adaptive equalizer 106 and the repetition patterns A and B may be determined to determine the data input timing. Then, symbol timing determination section 112 uses the determined data input timing as the timing for obtaining the output of adaptive equalizer 106 thereafter.

As described above, during short training, the symbol timing determination unit 112 outputs four different input timings to the adaptive equalizer 106,
Adaptive equalizer 10 according to four different input timings
The output of 6. Since the input timing closest to the repetition patterns A and B is determined and the input timing is used as the symbol timing for obtaining the output of the adaptive equalizer 106 thereafter, 38 symbols are used during the short training. The performance of the equalizer can be sufficiently obtained within the training time of the adaptive equalizer 106 defined as follows.

(Embodiment 2) Embodiment 2 will be described with reference to FIG. FIG. 4 is a block diagram showing a detailed configuration of symbol timing determination section 112 according to Embodiment 2. In the first embodiment, the symbol timing determination unit 1
Reference numeral 12 denotes an input in which the symbol timing determination unit 112 outputs four different input timings to the adaptive equalizer 106 during short training, and the output of the adaptive equalizer 106 is the closest to the repetition patterns A and B. Although the timing is determined, the symbol timing determination unit 112 determines the input timing by determining the distance between the output of the adaptive equalizer 106 one symbol before and the current symbol in the second embodiment. is there. The overall configuration of the receiving apparatus according to the second embodiment is the same as that of the first embodiment (FIG. 1). Therefore, only different points will be described here.

As shown in FIG. 4, the symbol timing determination unit 112 includes a sample 1 delay line 201, a sample 2 delay line 202, a sample 3 delay line 203, a sample 4 delay line 204, and inputs and outputs of each of the delay lines 201 to 204. 205 for switching the output, adaptive equalizer output buffer 20 corresponding to sample 1
6, an adaptive equalizer output buffer 207 corresponding to sample 2, an adaptive equalizer output buffer 208 corresponding to sample 3, an adaptive equalizer output buffer 209 corresponding to sample 4, and a distance calculator / determiner 210.

Next, the symbol timing determination section 120
Will be described. First, the first sample input from the AGC 105 is input to the sample 1 delay line 201, and the next sample is input to the sample 2 delay line 202.
Is input to The next sample is input to the sample 1 delay line 201 and the sample 3 delay line 203, and the next sample is input to the sample 2 delay line 202 and the sample 4 delay line 204. Thereafter, this is repeated. Thus, four sets of delay lines corresponding to the sample timing are configured. Data input timings (four types) of the delay lines 201 to 204 are sequentially selected by a selector and output to the adaptive equalizer 106.

The filter operation result of the adaptive equalizer 106 according to each data input timing is converted into an adaptive equalizer output buffer 206 corresponding to sample 1, an adaptive equalizer output buffer 207 corresponding to sample 2, and an adaptive equalizer corresponding to sample 3. Output buffer 208, output buffer 2 for sample 4 compatible adaptive equalizer
09.

The distance calculation / judgment unit performs adaptive equalizer 1 for each of the four types of data input timing one symbol before and this time.
06 is mapped on the signal point constellation, and its distance is determined. More specifically, the distance calculation / determination unit 210 determines that the one having the longest distance is closer to the symbol timing among the four types of data input timings. Then, the symbol timing determination unit 112 compares the determined data input timing with the subsequent adaptive equalizer 106.
Is used as the symbol timing for obtaining the output of

As described above, during short training, the symbol timing determination unit 112 outputs four different input timings to the adaptive equalizer 106,
The output of the adaptive equalizer 106 at one symbol before and at the current four data input timings is mapped on a signal point constellation to determine the distance, and the signal having the longest distance is determined at the four data input timings. Is determined to be close to the symbol timing, and the input timing is used as the symbol timing for obtaining the output of the adaptive equalizer 106 thereafter. The performance of the equalizer can be sufficiently obtained within the training time of the adaptive equalizer 106.

In the first and second embodiments, the symbol timing determination unit 112 uses the instantaneous value as the output of the adaptive equalizer 106. You may decide to take the average. Specifically, the symbol timing determination unit 112
The output value of the adaptive equalizer 106 is time-averaged every other symbol and held as two sets.
(See Embodiment 2) or the distance between the average value of the output of the adaptive equalizer 106 and the repetition patterns A and B (see Embodiment 2). 1), the symbol timing may be determined.

The present invention is not limited to the above-described embodiment, but can be implemented with appropriate modifications without departing from the spirit of the invention.

[0038]

As described above, according to the first aspect of the present invention, the timing phase means automatically generates a plurality of input timings having different timing phases when receiving the repetitive pattern of the short training signal. The output to the equalizing means, the holding means holds the output of the automatic equalizing means corresponding to each of the input timings different from each other in the timing phase outputted from the timing phase means to the output one symbol before, and the symbol timing determining means Is
Based on the combination of the current output of the automatic equalizer corresponding to the input timings different from each other in the timing phase and the output of the automatic equalizer one symbol earlier held in the holding unit, the input timings having the different timing phases are different. Since the optimum symbol timing is determined from the middle, the deviation of the symbol timing can be minimized, and the re-equalization can be performed by the automatic equalizing means even in a short training time.

According to a second aspect of the present invention, in the receiving apparatus according to the first aspect, the automatic equalizing means includes a transversal filter. In addition to the effects described above, the automatic equalizing means can be equalized with a simple configuration.

According to a third aspect of the present invention, in the receiving apparatus according to the first aspect, the symbol timing determining means determines whether the current output of the automatic equalizing means corresponding to the received signals having different timing phases corresponds to the current output. Since the distance from the output of the automatic equalization means one symbol before held in the holding means is determined, and the optimum symbol timing is determined from the input timings having different timing phases. In addition to the effects of the described invention, it is possible to determine the symbol timing by a simple method.

According to a fourth aspect of the present invention, in the receiving apparatus according to the first aspect, the symbol timing determining means repeats the output of the automatic equalizing means corresponding to each of the input timings having different timing phases. Since the optimum symbol timing is determined from the input timings having different timing phases by determining the distance from the signal point of the pattern, a simple method is provided in addition to the effect of the invention described in claim 1. To determine the symbol timing.

According to the fifth aspect of the present invention, the timing phase means generates a plurality of input timings having different timing phases and outputs the same to the automatic equalizing means when receiving the repeated pattern of the short training signal. , The holding means averages the output of the automatic equalization means corresponding to each of a plurality of input timings different from each other in the timing phase inputted from the timing phase means for every other symbol over a predetermined time, so that the timing phases differ from each other. Two sets of average values are held for each of a plurality of input timings, and the symbol timing determination means determines an optimum symbol timing from input timings having different timing phases based on the two sets of average values held in the holding means. The symbol timing shift can be minimized. It is possible to accurately perform the re-equalized by the automatic equalizer unit even in a short training time.

According to a sixth aspect of the present invention, in the receiving apparatus according to the fifth aspect, the symbol timing determining means determines a distance between two sets of average values of the output of the automatic equalizing means. Since the optimum symbol timing is determined from the input timings having different timing phases, the symbol timing can be determined by a simple method in addition to the effect of the invention described in claim 5. .

According to a seventh aspect of the present invention, in the receiving apparatus according to the fifth aspect, the symbol timing determination means is configured to calculate an average of outputs of the automatic equalization means corresponding to input timings having different timing phases. Since the value and the distance between the signal point of the repetition pattern are determined to determine the optimum symbol timing from the input timings having different timing phases, the effect of the invention according to claim 5 is obtained. The symbol timing can be determined by a simple method.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 1.

FIG. 2 is a diagram illustrating formats of a long training signal and a short training signal.

FIG. 3 is an explanatory diagram for explaining repetition patterns A and B.

FIG. 4 is a block diagram illustrating a configuration of a symbol timing determination unit according to Embodiment 2.

[Explanation of symbols]

 Reference Signs List 100 modem 101 A / D converter 102 complexization processing unit 103 baseband filter (BBF) 104 fixed equalizer 105 automatic gain control unit (AGC) 106 adaptive equalizer 107 phase synchronization unit 108 decision / decoder (maximum likelihood) Decoding section 109 descrambler 110 error calculation section 111 repetition pattern detector 112 symbol timing determination section 201 sample 1 delay line 202 sample 2 delay line 203 sample 3 delay line 204 sample 4 delay line 205 selector 206 sample 1 adaptive equalization Output buffer 207 Sample 2 adaptive equalizer output buffer 208 Sample 3 adaptive equalizer output buffer 209 Sample 4 adaptive equalizer output buffer 210 Distance calculator / determiner

Claims (7)

[Claims] 1. A receiving apparatus which includes an automatic equalizing means for equalizing distortion of a transmission path of a received signal and performs a long training and a short training. Timing phase means for generating a plurality of different input timings and outputting the same to the automatic equalizing means; and outputting one symbol from the automatic equalizing means corresponding to mutually different input timings of the timing phases output from the timing phase means. Holding means for holding up to the previous one; output of the automatic equalizing means corresponding to input timings different from each other in the timing phases, and output of the automatic equalizing means one symbol before held in the holding means Input timings different from each other based on the combination of And a symbol timing determining means for determining an optimum symbol timing from the timings. 2. The receiving apparatus according to claim 1, wherein said automatic equalizing means comprises a transversal filter. 3. The receiving apparatus according to claim 1, wherein the symbol timing determination unit holds the current output of the automatic equalization unit corresponding to each of the input timings having different timing phases and the holding unit. A receiving apparatus for determining a distance from an output of the automatic equalizing unit one symbol before, and determining an optimum symbol timing from input timings having different timing phases. 4. The receiving apparatus according to claim 1, wherein the symbol timing determination unit is configured to determine a distance between an output of the automatic equalization unit and a signal point of a repetition pattern corresponding to input timings different from each other in the timing phase. And determining an optimal symbol timing from the input timings having different timing phases. 5. A receiving apparatus which incorporates an automatic equalizing means for equalizing distortion of a transmission path of a received signal and performs long training and short training. A timing phase unit that generates a plurality of different input timings and outputs the plurality of input timings to the automatic equalization unit; and an output of the automatic equalization unit corresponding to each of a plurality of input timings different from each other in the timing phase input from the timing phase unit. Holding means for averaging every other symbol over a predetermined time and holding two sets of average values for each of a plurality of input timings having different timing phases; and two sets of average values held by the holding means. From the input timings having different timing phases based on the A receiver comprising: symbol timing determination means for determining the timing. 6. The receiving apparatus according to claim 5, wherein the symbol timing determining means determines a distance between the two sets of average values of the output of the automatic equalizing means, and the timing phases are different from each other. A receiving apparatus for determining an optimal symbol timing from input timings. 7. The receiving apparatus according to claim 5, wherein the symbol timing determination unit includes an average value of outputs of the automatic equalization unit corresponding to input timings different from each other in the timing phase, and a signal of a repetition pattern. A receiving apparatus for determining a distance from a point and determining an optimal symbol timing from input timings having different timing phases.