JP2948860B2 - ISDN terminal equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ISDN terminal device having 3.1 KHz audio or voice as a transmission capability.

[Prior Art] In general, ISDN has an interconnection function (internet working function) with a conventional line network such as a public telephone network, whereby telephone and facsimile terminals connected to ISDN are Data can be transmitted to and from a telephone terminal and a group 3 facsimile terminal connected to a public telephone network.

Further, as the data terminal using the ISDN as a transmission line, a data terminal having a configuration in which an adapter device for connecting to the ISDN is added to a data terminal used in a conventional public telephone network or the like can be used, FIG. 3 shows an example of a group 3 facsimile apparatus having such a configuration.

In FIG. 1, a control unit 1 performs a control process of each unit of the facsimile apparatus and a facsimile transmission control procedure process. A system memory 2 stores a control processing program and a processing program executed by the control unit 1. In addition to storing various data and the like necessary when executing the processing, the work area of the control unit 1 is configured.
The parameter memory 3 stores various information unique to the group 3 facsimile apparatus.

The scanner 4 is for reading a document image at a predetermined resolution, the plotter 5 is for recording and outputting an image at a predetermined resolution, and the operation display unit 6 is for operating this facsimile machine. It consists of various operation keys and various indicators.

The encoding / decoding section 7 encodes and compresses the image signal and decodes the encoded and compressed image information into the original image signal. The image storage device 8 encodes and compresses the image signal. This is for storing a large number of image information in the state of being closed.

The group 3 facsimile modem 9 is for realizing a group 3 facsimile modem function, and is a low-speed modem function (V.21
Modem), and a high-speed modem function (V.29 modem, V.27ter modem) for mainly exchanging image information, and a modem processing unit 10 for realizing a digital modem processing function and a modem processing unit 10 It comprises a signal conversion unit 11 for mutually converting a digital signal to be input / output into an analog signal.

The network control unit 12 is for connecting the facsimile apparatus to a public telephone line network, and has an automatic transmission / reception function with the public telephone line network.
It has a function of interconnecting the facsimile modem 9 and the ISDN network controller 13.

The ISDN network control device 13 is for connecting the facsimile device to ISDN, and has an ISDN interface circuit 14 for exchanging data with the S / T point of ISDN,
D channel transmission control unit for performing call control between
And a CODEC 16 for mutually converting analog signals input and output by the group 3 facsimile modem 9 into digital signals exchanged on ISDN.

These control unit 1, system memory 2, parameter memory 3, scanner 4, plotter 5, operation display unit 6,
The encoding / decoding unit 7, the image storage device 8, the group 3 facsimile modem 9, and the ISDN network control device 13 are connected to the system bus 17, and the exchange of data among these elements is mainly This is performed via the system bus 17.

In this way, by adding the ISDN network control device 13 to the group 3 facsimile apparatus connected to and used by the public telephone network, the group 3 facsimile apparatus can be connected to ISDN and used. A group 3 facsimile machine for ISDN can be realized at low cost.

In other words, in this case, the digital signal used in the internal processing of the group 3 facsimile apparatus is converted into an analog signal once, and then converted into a PCM signal (digital signal) on ISDN using a so-called sound contact. A 3 facsimile machine is connected to ISDN.

[Problems to be Solved by the Invention] However, in the above-described conventional apparatus, a function of mutually converting a digital signal generated inside the group 3 facsimile apparatus into an analog signal (in this case, a group 3 facsimile modem) and a group 3 facsimile modem are provided. A function to convert between analog signals sent and received by the facsimile machine to digital signals on ISDN (in this case, CODEC) is required. This may be disadvantageous and disadvantageous in terms of cost.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide an ISDN terminal device capable of reducing the size and cost of the device.

Means for Solving the Problems The present invention relates to a digital modulation means for modulating a digital transmission signal into an analog transmission signal by a predetermined digital modem modulation method in an ISDN terminal device having a transmission capability of 3.1 kHz audio or voice. A first auxiliary sampling circuit that samples the band signal at the sampling rate of the nonlinear PCM signal, a linear / nonlinear conversion unit that converts the sampling output of the interpolation sample circuit into a nonlinear PCM signal, and a linear / nonlinear conversion unit An output circuit that outputs the output as a transmission signal, and a nonlinear PC received from ISDN
A non-linear / transformation conversion unit that converts the M signal into a linear signal, a demodulation unit that converts an output signal of the non-linear / linear conversion unit into a corresponding baseband signal, and a baseband signal output from the demodulation unit. A second interpolation sample circuit for sampling at a data rate of a predetermined digital modem modulation method, and a digital demodulation means for converting a sampling output of the second interpolation sample circuit to a corresponding digital reception signal by the digital modem modulation method It is provided with.

[Operation] Therefore, the baseband signal of the digital modulation means of the digital modem is sampled at the sampling rate of the nonlinear PCM signal and converted to a nonlinear PCM signal to form a transmission signal, and the received nonlinear PCM signal is converted to a baseband signal. Converts, samples the baseband signal at the data rate of the digital modem and applies it to the digital demodulation means, so there is no need for an analog / digital mutual conversion function, using a conventional analog communication device and using ISDN Data transmission.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a main part of a modem device according to an embodiment of the present invention. Note that this modem device has a CCITT recommendation V.29 modem function, and is capable of data transmission with a transmission speed of 9600 bps (16-level quadrature amplitude modulation (16QAM); modulation speed of 2400 baud). Elements other than the main part, for example, a training sequence control unit and the like are not directly related to the present invention, so that illustration and description are omitted.

The transmission data SD output from the transmission data generating means (not shown) is scrambled by the scrambler 21 and then decomposed by the encoder 22 into four bits (quad bits), which are one modulation unit, and represents corresponding signal points. The symbol data is converted to symbol data, and the symbol data is applied to the signal point generation circuit 23.

The signal point generation circuit 23 forms a signal having an amplitude and a phase corresponding to the input symbol data. The signal is subjected to waveform shaping (spectrum shaping) via a low-pass filter 24, and then applied to a modulation unit 25. The resultant signal is subjected to quadrature amplitude modulation and applied to the interpolation sample circuit 26.

Here, the sample rate of the modulated data output from the modulation unit 25 is a rate obtained by multiplying the modulation rate Fb by the number of bits per symbol. In this case, the modulation rate Fb is 2.4 KHz.
Since the number of bits per symbol is 4 bits, the sample rate of the data output from the modulator 25 is 9.6 KHz
(= 4Fb).

On the other hand, the data rate of the PCM signal on ISDN is 64 Kbps, and since the sample rate is 8 bits, the sample rate becomes 8 KHz.
Is extracted by an ISDN transceiver circuit 27 for transmitting and receiving data and output from the ISDN transceiver circuit 27.

The interpolation sample circuit control 26 outputs from the modulation unit 25 9.
The digital signal having a sample rate of 6 KHz is interpolated and sampled (decimated in this case) into a digital signal of 8 KHz based on a sampling clock PC, and the sampled data is applied to a linear / non-linear converter 28. I have.

The linear / nonlinear conversion unit 28 converts linear code data output from the modulation unit 25 into data of the same non-linear code as the PCM signal on ISDN, and the converted data is used as transmission data TX. It is added to the ISDN transceiver circuit 27.

That is, in order to execute the modulation process of the digital modem, the output data is a linear code in which the weight of each bit value corresponds to the bit position itself.

On the other hand, as is well known, the PCM signal on ISDN has μ = 255
The non-linear code of the 15-fold linear μ characteristic or the 13-fold linear A characteristic of A = 87.6 is used.

Therefore, the output data of the modulator 25, which is a linear code, is converted into a PCM signal, which is a nonlinear code, by the linear / nonlinear converter.

The received data RX from the ISDN output from the ISDN transceiver circuit 27 is sampled by a sampling circuit 29 that performs a sampling operation with a sampling clock PC, and is applied to a nonlinear / linear conversion unit 30.

The non-linear / linear conversion unit 30 converts a PCM signal on ISDN into a linear digital signal, and the output data is applied to a demodulation unit 31 having an operation rate of 8 KHz.

The demodulation unit 31 demodulates input data to form a baseband signal. The output signal is applied to an interpolation sample circuit 33 via a low-pass filter 32.

The interpolation sample circuit 33 interpolates and samples a digital signal having a data rate of 8 KHz at 9.6 KHz, which is four times the modulation speed Fb, and the sampling data is applied to a symbol selector 34.

At the time of training to be executed at the start of reception of the digital modem, the symbol selector 34
While the data inputted from 33 is output to the timing reproducing section 35 as it is, one of four consecutive symbols is selected at the time of data reception, and the selected symbol data is output to the automatic equalizing circuit 36.

The timing reproduction unit 35 forms a timing adjustment signal TS for adjusting the sampling timing of the interpolation sample circuit 33 so that the frequency component of the modulation speed Fb included in the input symbol data is maximized. The timing adjustment signal TS is output to the interpolation sample circuit 33, and as a result, the sampling timing of the interpolation sample circuit 33 is adjusted. This timing adjustment signal TS is
After the end of the training, the value at the end of the training is held.

The automatic equalization circuit 36 adjusts the amplitude and phase of the input symbol data so as to be a predetermined value, and the output signal is applied to a decision unit 37.

The determiner 37 determines the signal point of the received data based on the data output from the automatic equalization circuit 36, and the determination result is converted to the original 4-bit data via the decoder 38, After being descrambled by the descrambler 39, the 4-bit data is output as a reception data RD to a reception data processing unit (not shown).

Further, the error control unit 40 adjusts the characteristics of the automatic equalization circuit 36 based on an error signal SE indicating an error between the input data output by the determiner 37 and the data of the signal point of the determination result. .

FIG. 2 shows an ISDN implemented using the modem device of FIG.
1 shows a group 3 facsimile apparatus for use in the present invention. In addition,
In this figure, the same parts as those in FIG. 3 and corresponding parts are denoted by the same reference numerals.

The modem unit 50 realizes a group 3 facsimile modem function and is capable of inputting and outputting PCM signals on ISDN.

The modem device 50 has a low-speed modem function for exchanging transmission procedure signals and a high-speed modem function for transmitting image signals. It has a function of mutually converting codes and non-linear codes.

In this manner, in the present embodiment, the conventionally added IS
Since the codec for the DN is not required, the size of the device can be reduced, and the cost of the device can be reduced.

By the way, in the embodiment described above, the case where the present invention is applied to the case where the data rate of the CCITT recommendation V.29 modem is 9600 bps is described. The present invention can be similarly applied to a .21 modem.

[Effects of the Invention] As described above, according to the present invention, in an ISDN terminal device having a transmission capability of 3.1 KHz audio or voice, a baseband signal of a digital modulation means of a digital modem is converted at a sampling rate of a nonlinear PCM signal. Along with sampling and converting to a nonlinear PCM signal to form a transmission signal, the received nonlinear PCM signal is converted to a baseband signal, and the baseband signal is sampled at the data rate of the digital modem and applied to the digital demodulation means. Since it does not require an analog / digital mutual conversion function, it can transmit data to and from a conventional analog communication device using ISDN, so that it is possible to reduce the size and cost of the device. Get the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a CCITT recommendation V.29 modem according to an embodiment of the present invention. FIG. 2 is a block diagram showing an example of a group 3 facsimile apparatus using the modem of FIG. FIG. 3 is a block diagram showing a conventional example of a group 3 facsimile apparatus for ISDN. 26,33 ... Interpolation sample circuit, 27 ... ISDN transceiver circuit, 28 ... Linear / non-linear conversion unit, 29 ... Sampling circuit, 34 ... Symbol selector, 35 ... Timing recovery unit.

Claims (1)

(57) [Claims] 1. An ISDN terminal device having 3.1 KHz audio or voice as a transmission capability, wherein a baseband signal of a digital modulation means for modulating a digital transmission signal into an analog transmission signal by a predetermined digital modem modulation method is converted to a non-linear PCM signal. A first auxiliary sample circuit for sampling at a sampling rate, and a sampling output of the interpolation sample circuit, a non-linear PC
A linear / nonlinear converter for converting to an M signal, an output circuit for outputting the output of the linear / nonlinear converter as a transmission signal, and a non-linear / transformation converter for converting a non-linear PCM signal received from ISDN to a linear signal; A demodulator for converting an output signal of the non-linear / linear converter to a corresponding baseband signal; and a second for sampling the baseband signal output from the demodulator at a data rate of a predetermined digital modem modulation method. An ISDN terminal device comprising: an interpolation sample circuit; and digital demodulation means for converting a sampling output of the second interpolation sample circuit into a corresponding digital reception signal by the digital modem modulation method.