JPH0454735A - Modulator-demodulator - Google Patents

Abstract

PURPOSE:To make the operation of a demodulator stable even when an initial part is suppressed and missing by providing a modulator sending a short sequence in which a consecutive period of 180 deg. phase inversion is set to be a response time of a compander or over as the MODEM. CONSTITUTION:When a data is sent from its own station to an opposite station, a modulator 1a in a MODEM 1 converts a MODEM training signal with a short sequence and a transmission data S1 from a terminal equipment or the like into a transmission analog signal S3 in a voice band in response to a transmission request signal S2 from a terminal equipment and the signal S3 is inputted to a transmitter 2a in a radio equipment 2. Then its output is sent to a receiver 3a in a radio equipment 3 and demodulated into a reception analog signal R2 in a voice band. The reception analog signal R2 is inputted to a demodulator 4b through a hybrid circuit 3c in the radio equipment 3, a 2-wire public telephone line and a hybrid circuit 4c in a MODEM 4 of an opposite station and to a demodulator 4b. Since a segment 3 of the reception analog signal R2 is set longer, a part not effected remains toward the end of the segment and a signal component required for demodulation is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a short sequence training method for turnaround operation of a modulator/demodulator used in mobile communication such as a car telephone.

(Prior art) Standardized transmission speed of 4800 bp for general switched telephone network
The modem for sb is based on the CCITT (International Telegraph and Telephone Consultative Committee) recommendation V-27ter.
The figure shows an example of the configuration of a communication line including mobile communication such as a car phone using this modem. Also, CCI TT Recommendation V
, 27ter shows the structure of a short sequence modem training signal for turnaround operation. The operation when sending data from the local station to the partner station shown in FIG. 1 will be described below.

The modulator 1 & in the modem 1 in the own station is
In response to a transmission request signal S2 from a terminal device, etc., a modem training signal according to a short sequence for turnaround operation shown in FIG. Convert to analog data signal (hereinafter referred to as transmission analog signal) S3,
It is sent to the transmitter 2a in the radio device 2. This transmission analog signal S3 is modulated by the transmitter 2a into a high frequency analog data signal for a wireless line, and is transmitted to the base station via an antenna. The transmitted high-frequency analog data signal is received by the antenna of the base station, inputted to the receiver 31L in the radio 3, and converted into a phase-modulated analog data signal (
(hereinafter referred to as a received analog signal) is demodulated into R2. Since the communication path from the base station to the partner station is 211, the received analog signal R2 passes through a hybrid circuit 3c in the radio device 3, a 12-wire public telephone line, and a hybrid circuit 4C in the modem 4 of the partner station. , are input to the demodulator 4b. The received analog signal R2 input to the demodulator 4b is demodulated into a digital signal and sent to a terminal device or the like as received data R3.

In communication lines including mobile communication such as the above-mentioned car telephone, the reception SNR deteriorates due to fading, thermal noise, click noise, random FM noise, etc. occurring in the wireless line. To solve this problem, companders are used in car telephone lines to improve the SNR. This compander consists of a compressor and an expander, and includes transmitters 2a in the radio device 2 and radio device 3,
A compressor is added to each receiver 3b, and an expander is added to each receiver 3h and 2b.

This component was recommended by CCITT G, 162, and is also described, for example, in ``Car Telephone'' (1986 6O-2) edited by Moriji Kuwahara, Institute of Electronics and Communication Engineers P, 39-45. Its function is to improve the SN'R, which increases the voice level in the radio section during a call, and to greatly suppress noise generated in the radio system when there is no call. Therefore, the use of Con Gunda helps improve communication quality in mobile communications.

(Problem to be Solved by the Invention) However, when the above connosonder is used, the received analog signal R2 demodulated by the receiver 3a of the radio device 3 is affected by the response time of the rise of the compander, and the transmitted analog signal S3 The part corresponding to the first part of is suppressed and is input as is to the demodulator 4b of the modem 4 of the other station. The demodulator 4b receives the input received analog signal R2.
It is demodulated into a digital signal by a built-in phase demodulator, but the first part of the received analog signal R2 that is pressed is

The reception level of the reception carrier detected by the demodulator 4b is υ
Because of this, the first part of the modem's training signal, which is a short sequence for turnaround operation, is lost, causing the problem that the operation of the demodulator 4b becomes unstable. Then, this received analog signal R2
The time of the first part of the missing time varies depending on the level of the analog signal transmitted by the transmitter 2a in the radio device 2 of the local station and the transmitter 3b in the radio device 3 of the base station, and the transmission stop time.

FIG. 3(A) shows a time response waveform of a transmitted analog signal corresponding to the training signal of the modem shown in FIG. 2, and FIG. 3(B) shows a time response waveform of the received analog signal.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a modem that operates stably even when the training signal of the modem is affected by the compander used in the radio circuit. do.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a
The SK modulator/demodulator is equipped with a modulator that sends out a short sequence for a turnaround operation in which a continuous period of at least 180 degrees of phase inversion is set to be longer than the response time of the compander.

(Function) The modulator of the modem according to the present invention outputs a modem training signal in the form of a short sequence of turnaround operations in which the continuous period of at least 180 degree phase inversion is set appropriately long considering the influence of the compander. do.

When this modem's training signal is transmitted to the other party's modem via a wireless line that includes a compander, the first part of the modem's training signal is suppressed and lost by the compander, but the latter part is suppressed. Since the training data necessary for stable operation of the demodulator of the modulator/demodulator can be secured, the demodulator operates stably.

(Embodiment) FIG. 4 shows the structure of a modem training signal in the form of a short sequence for a turnaround operation generated by a modulator/demodulator according to this embodiment. As shown in FIG. 4, the training signal for the modem is longer in duration by 40 simple interdles (SL) than in the conventional case shown in FIG.

This corresponds to a time of 25m5 for a modem with a data rate of 4800 bit/s. Also, segment 4
Since the conventional sindel pattern generation circuit operates as is, the sindel pattern can be operated normally even in a demodulator that monitors the phase change when switching segments 3 and 4.

Next, the operation when the modem according to this embodiment is used in the modem 1 and modem 4 of the communication line shown in FIG. 1 will be described below. When transmitting data from the own station to the other station, the modulator 1a in the modem 1 trains the modem in a short sequence for turnaround operation based on FIG. 4 in response to a transmission request S2 from a terminal device, etc. The transmitter 2aK in the radio 2 converts the signal and the transmission data S1 from the terminal device etc. into a transmission analog signal S3 within the voice band:
Send. FIG. 5(A) shows a time response waveform of the transmitted analog signal S3 corresponding to the training signal of the modem. The transmission analog signal S3 is modulated by the transmitter 2a into a high frequency analog data signal for a wireless line, and is transmitted to the base station via an antenna. The high frequency analog data signal is received by the antenna of the base station, input to the receiver 3a in the radio device 3, and demodulated into the received analog signal R2 within the voice band. This received analog signal R2 is passed through a hybrid circuit 3c in the radio 3, a two-wire public telephone line, and a hybrid circuit 4C in the modem 4 of the partner station.
The signal is input to the demodulator 4b. FIG. 5(B) is a time response waveform of the received analog signal R2, which corresponds to the transmitted analog signal shown in FIG. is suppressed due to the influence of the compander's rise response time. However, since segment 3 of the received analog signal R2 is set to be long, there remains a portion at the rear that is not affected.
Signal components necessary for demodulation operation can be secured. The data portion of the received analog signal R2 is demodulated into a digital signal by a demodulator 4b, and sent to a terminal device or the like as received data R3.

(Effects of the Invention) As described in detail above, according to the present invention, the modem training signal in a short sequence for turnaround operation output from the modulator of the modem is
Since the response time of the demodulator has been increased by the amount of response time of the modem, even if the first part of the modem's training signal by the converter used in the wireless line is suppressed and lost, the training data necessary for stable operation of the demodulator can be ensured. You can get the effect that you can.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a communication line using a modem according to the present invention, Figure 2 is a diagram showing the configuration of a training signal for a modem based on CCI V, 27ter, and Figure 3 corresponds to Figure 2. FIG. 4 is a diagram showing the configuration of a modem training signal according to an embodiment of the present invention. FIG. 5 is a diagram showing the time response waveforms of a transmit analog signal and a receive analog signal. FIG. FIG. 3 is a diagram showing a time response waveform of an analog signal. 1.4...Modem, 2.3-...Radio device, Ja, 4a
...Modulator, lb, 4b...Demodulator, 2m, 3b...
...Transmitter, 2b, 3m...Receiver, 3c, 4c
...Hybrid circuit. Patent Applicant Oki Electric Industry Co., Ltd. CCITT V, 27ter Modem Training Signal Figure Segment 3 Segment 4 Segment i (A) Transmission Analog Signal - Reception Analog Signal Transmission analog signal and reception analog signal 3rd corresponding to Figure 2 Figure 4 Modem training according to an embodiment of the present invention Figure 4 Segment 3 Segment 4 Segment 1 Segment 4 Segment 1 Transmission analog signal and reception analog signal corresponding to Figure 4 Figure 5

Claims (1)

[Claims] In a PSK modem with half-duplex operation, at least one
A modulator/demodulator comprising a modulator that transmits a short sequence for a turnaround operation in which a continuous period of 80-degree phase inversion is set to be longer than a response time of a compander.