JP3894014B2 - Modulator / demodulator, communication control method and processing program thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to V.I. Communication control of a modem having a half-duplex function conforming to the 34 standard, in particular, a modem and a communication control method capable of preventing misperception due to a delay failure between tone signals composed of the same frequency components received in phase 2 And its processing program.
[0002]
[Prior art]
A data communication procedure via a telephone line is defined by the ITU-T (International Telecommunication Union Telecommunication Standardization Sector) as, for example, a V series recommendation. V. of these The 34 recommendation defines a modem (hereinafter referred to as a modem) that operates at a data communication speed corresponding to 33600 bps. This V. In the half-duplex operation of 34, phases 1 to 3 are performed as a preparation stage of data communication. The communication control operation between the calling side and the response side in phase 2 will be described below with reference to FIG.
[0003]
In phase 2, the calling modem accesses the INFO0c signal to notify the modem capabilities (supported symbol rate, carrier frequency, presence of power suppression function, etc.) after the silence period of 75 ± 5 ms after phase 1 has elapsed. Sent to the target answering modem. Similarly, the answering modem transmits the INFO0a signal toward the calling modem after the silence period of 75 ± 5 ms after the phase 1 has elapsed. Thereby, the function information of the modems is exchanged, and preparations for detecting the later tone signals A and B are made.
The calling modem continues to send a tone B signal towards the answering modem. The answering modem sends a tone A signal to the calling modem for at least 50 ms, followed by a tone A phase reversal signal (denoted inv A) to the calling modem.
[0004]
Upon detecting this, the calling modem transmits a tone B phase inversion signal for 10 ms toward the answering modem after waiting for 40 ± 10 ms. The calling modem then transmits a line probing signal L1 to the answering modem for 160 ms. Further, the calling modem transmits a line probing signal L2 indicating the line state to the answering modem.
[0005]
The response modem receives the line probing signal L1 in the 160 ms period, and receives the line probing signal L2 in a period not exceeding 500 ms. The answering modem receives the line probing signals L1 and L2 and transmits a tone A signal to the calling modem for 25 ms. When the calling modem detects this tone A signal, it transmits a tone B signal to the answering modem, thereby analyzing the line status from the answering modem and using information such as the selected symbol rate, carrier frequency, and pre-emphasis coefficient. A certain INFOh signal is received.
[0006]
[Problems to be solved by the invention]
The above is a normal sequence, but on the other hand, generally, there are various failure elements in the line, and troubles in the phase stage may occur due to delay failures such as communication delay and echo. Specifically, if a tone A signal is detected during transmission of the line probing signal L2 due to this delay failure, the calling modem may interrupt transmission of the line probing signal L2 halfway. . This will be described below.
[0007]
As for the communication delay of the delay failure, for example, it is known that there is a delay of up to 1.2 seconds in a round trip in an international call through two satellites.
As for the echo of a delay fault, in communication using a telephone line, an echo is generated if there is an impedance mismatch at a place where 2-line 4-line conversion is performed at the line end.
As shown in FIG. 4, there are two types of echoes, a near-end echo generated in a part of the line and a far-end echo generated in almost the entire line. The return amount of the signal due to this echo changes from time to time depending on the line impedance, that is, the communication path.
[0008]
In the initial step of Phase 2 described above, the answering modem transmits a tone A signal following INFO0a, which echoes at the calling modem end, returns to the answering modem end, and further echoes at this answering modem. The calling modem end is reached and an echo failure occurs. Although this echo is attenuated compared to the original signal, there is a possibility that the calling modem may determine that it is a tone A signal depending on the line condition or the electrical characteristics of the modem itself. That is, depending on the line delay, the echo corresponding to the tone A signal may reach the calling modem end while the calling modem is transmitting the line probing signal L2. In such a case, the calling modem transmits the tone B signal (1200 Hz) to the answering modem while the transmission of the line probing signal L2 is also in progress.
[0009]
Upon receiving this, the answering modem reflects the symbol rate, carrier frequency, and pre-emphasis coefficient determined by performing FFT (Fast Fourier Transform) analysis based on the incompletely transmitted line probing signals L1 and L2. The generated INFOh signal is generated. As a result, the subsequent communication control may not be established.
[0010]
The present invention has been made in view of the above-described problems. Modulator / demodulator, communication control method and method capable of preventing misperception due to delay interference between tone signals composed of received same frequency components in phase 2 of communication control of modem / modulator having half duplex function compliant with 34 standard To provide a processing program.
[0011]
[Means for Solving the Problems]
(1) In order to achieve the above object, the modem device according to the present invention provides A tone signal receiving means for receiving a tone B signal transmitted following a line probing signal L1, L2 representing a line state in phase 2, in a modem apparatus for performing modulation / demodulation by half-duplex communication based on the 34 standard; A creation means for creating INFOh information obtained by analyzing the line state based on the probing signals L1 and L2, and a predetermined frequency 1200 Hz component corresponding to the tone B signal in the analysis value obtained by frequency analysis of the line probing signals L1 and L2. A determination means for determining whether or not the frequency is higher than at least one of components at 1050 Hz and 1350 Hz which are the surrounding frequencies, and selection of selecting 2400 as a symbol rate if it is recognized that the determination is larger. Means and greater in the determination Once Tsu sends said INFOh information, if larger by the determination was observed, characterized by having a transmitting means for transmitting the INFOh information reflecting the selected symbol rate.
[0012]
(2) The modem of (1) may be incorporated in a communication device such as a facsimile.
[0013]
(3) Further, in order to achieve the above object, a communication control method according to the present invention includes In the communication control method for performing communication control by half duplex communication based on the 34 standard, the tone B signal transmitted following the line probing signals L1 and L2 representing the line state in phase 2 is received, and the line probing signal L1 is received. , L2 is used to generate INFOh information obtained by analyzing the line state, and a predetermined frequency 1200 Hz component corresponding to the tone B signal in the analysis value obtained by frequency analysis of the line probing signals L1 and L2 is the peripheral frequency. It is determined whether or not it is larger than at least one of the components of 1050 Hz and 1350 Hz, and if it is found that the determination is larger, 2400 is selected as the symbol rate and it is not recognized that the determination is larger. If the INFOh information is transmitted, If it is heard were observed, and transmits the INFOh information reflecting the selected symbol rate.
[0014]
(4) Further, as a communication control program for causing a communication device such as a modem, a facsimile, or a computer such as a computer to execute each process in the communication control method of (3), it is used as a hard disk or ROM (Read Only). Memory) or the like.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a block diagram for explaining a modem according to the present invention. FIG. 2 is a flowchart for explaining the operation of the modem device of FIG.
[0016]
First, the configuration of a modem that is a modem according to the present invention will be described with reference to FIG.
The modem 10 includes a control unit 20, an A / D conversion unit 30, and a modem unit 40.
[0017]
In the control unit 20, a program for performing condition determination processing, data bit processing, and the like is stored in the ROM 24. For example, command interpretation from a connected PC, instructions to the modem unit (dialing instructions, response start instructions), Transmission / reception data compression / decompression and error correction processing are executed by a CPU (Central Processing Unit) 22.
[0018]
The A / D converter 30 includes a CODEC 32 that mutually converts an analog signal from a telephone line and a digital signal from a PC.
[0019]
Based on the processing request from the control unit 20, the modulation / demodulation unit 40 performs V.P. It has a function of performing modulation / demodulation processing according to the 34 standard. In the modulation / demodulation unit 40, a digital signal processor (DSP) 42 performs digital signal processing such as sequence control processing and modulation / demodulation processing of each phase, which is a program stored in the ROM 46.
The processing units 50 to 54 specifically shown in the ROM 46 for realizing the modulation / demodulation processing of the present invention will be described below. Note that description will be given using the sequence in phase 2 of FIG. 3 as appropriate.
[0020]
The tone signal receiving unit 50 receives the tone B signal transmitted from the calling modem following the line probing signals L1 and L2 in the phase 2.
The INFOh information creation unit 51 analyzes the line state based on the line probing signals L1 and L2, and creates INFOh information for notifying the calling modem.
[0021]
The determination unit 52 determines whether or not a predetermined frequency component in the frequency analysis value obtained by performing the FFT analysis on the line probing signals L1 and L2 is larger than the surrounding frequency components. Here, it is determined whether or not the 1200 Hz component (this is the frequency corresponding to the tone B signal) is larger than the components of 1050 Hz and 1350 Hz that are the surrounding frequencies as the predetermined frequency.
[0022]
If the determination unit 52 determines that the 1200 Hz component is larger than both 1050 Hz and 1350 Hz, the selection unit 53 selects 2400 as the symbol rate.
The signal transmission unit 54 transmits INFOh information as shown in FIG. 3 in the prior art if the determination unit 52 does not recognize that the predetermined frequency is large. Is found to be large, INFOh information reflecting the symbol rate 1200 is created and transmitted to the calling modem.
[0023]
Next, the communication control operation according to the present invention realized by the modem of FIG. 1 will be described using the flowchart of FIG.
[0024]
The answering modem receives the call modem from the calling modem. The line probing signals L1 and L2 in phase 2 of half-duplex communication based on the 34 standard are received (step S201), and then the tone B signal is received by the tone signal receiving unit 50 (step S202).
The INFOh information creation unit 51 of the response modem performs FFT on the line probing signals L1 and L2 (step S203).
[0025]
The determination unit 52 of the response modem determines whether or not the predetermined frequency 1200 Hz component is larger than the surrounding 1350 Hz and 1050 Hz (step S204).
If it is recognized that the value of the predetermined frequency 1200 Hz component is larger, the response modem selection unit 53 selects 2400 as a symbol rate and sets it (step S205). If it is not recognized that the value of the predetermined frequency 1200 Hz component is larger, a symbol rate that is to be optimum is selected and set by symbol rate selection by normal (conventional) line diagnosis (step S207).
[0026]
When step S205 is executed, the INFOh information creating unit 51 creates INFOh information reflecting the fixed symbol rate value (step S206). When step S207 is executed, the INFOh information creation unit 51 creates INFOh information by normal phase 2 processing reflecting the set symbol rate value (step S208).
[0027]
The signal transmission unit 54 of the response modem transmits the INFOh information created in step S206 or S208 to the calling modem (step S209).
[0028]
Thus, by making the symbol rate selection in phase 2 fixed, it becomes possible to prevent misperception due to a delay failure of the tone signal, and the subsequent communication control can be reliably established. .
[0029]
The present invention is not limited to the embodiment described above and the example described with reference to FIGS. 1 and 2, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, 1350 Hz and 1050 Hz are set as the determination frequencies in the determination unit 52 in FIG. 1 and step S204 in FIG. 2, but only one of them may be set as the determination frequency.
[0030]
In addition, the modem described above is particularly V. Although described as a device having a function of performing half-duplex communication based on the 34 standard, it is naturally not limited to a device having only this function. 90 and V.V. Even a modem that is compatible with the 29 standard, etc., is a V.C. The present invention can be applied as long as it supports the communication function of the 34 standard, and the effect can be achieved.
[0031]
By mounting the modulation / demodulation device in the above-described embodiment on an electronic computer such as a personal computer or a communication device such as a facsimile, it is possible to stabilize communication.
[0032]
Further, in the above-described embodiment, each of the steps S201 to S209 in FIG. 2 for performing the communication control and the processing program in various modified examples are stored as application software in a recording medium such as a hard disk, and the recording medium is arbitrarily set. The program may be installed on a computer or a communication device or installed by downloading from another computer via a network. In this way, the program or the like can be stored in a portable recording medium such as a CD-ROM and sold or carried.
[0033]
【The invention's effect】
By making the selection of the symbol rate in phase 2 according to the present invention fixed, it becomes possible to prevent misperception due to a delay failure of the tone signal, and the subsequent establishment of communication control can be performed reliably. It becomes like this.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining a modem according to the present invention.
FIG. 2 is a flowchart for explaining the operation of the modem device of FIG. 1;
FIG. 3 is a diagram for explaining the operation of phase 2 in a conventional modem.
FIG. 4 is a diagram for explaining an echo failure.
[Explanation of symbols]
10: Modem 20: Control unit 30: A / D converter 40: Modem 42: DSP
50: tone signal receiving unit 51: INFOh information creating unit 52: determining unit 53: selecting unit 54: signal transmitting unit

Claims (4)

V. In a modem that performs modulation / demodulation by half-duplex communication based on the 34 standard,
Tone signal receiving means for receiving the line probing signals L1 and L2 representing the line state and the tone B signal transmitted following the line probing signals L1 and L2 in the phase 2;
Received said line probing signal L1, L2 frequency analysis to be that frequency 1200Hz component corresponding to the tone B signal in the analysis value was found whether larger than that before and after the at least one component of the frequency of 1200Hz Determining means for determining
If it is found that the determination is larger, a fixed value is selected as the symbol rate. If it is not recognized that the determination is larger, the line state is analyzed based on the received line probing signals L1 and L2. Selecting means for selecting the optimum symbol rate ;
Creating means for creating INFOh information reflecting the fixed symbol rate if it is found to be greater than the determination; otherwise, creating INFOh information reflecting the optimum symbol rate; ,
If larger by the determination was not observed, and transmits the INFOh information reflecting the optimal symbol rate, if greater by the determination was observed, INFOh information reflecting the symbol rate of the fixed value A modulation / demodulation apparatus comprising: transmission means for transmitting   A communication apparatus comprising the modulation / demodulation apparatus according to claim 1. V. In a communication control method for performing communication control by half-duplex communication based on the 34 standard,
In line 2, the line probing signals L1 and L2 representing the line state and the tone B signal transmitted following the line probing signals L1 and L2 are received,
Received line probing signal L1, L2 that correspond to the tone B signal in the analysis value obtained by frequency analysis of the frequency 1200Hz component, whether larger than that before and after the at least one component of the frequency of 1200Hz Judgment,
If it is found that the determination is larger, a fixed value is selected as the symbol rate, and INFOh information reflecting the selected symbol rate is generated and transmitted.
A communication control method characterized by creating and transmitting INFOh information obtained by analyzing a line state based on the received line probing signals L1 and L2 if it is not found that the determination is larger.   The communication control program for making a computer or a communication apparatus perform each process in the communication control method of Claim 3.

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