JP2735844B2 - Data communication system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data communication system for transmitting digital data such as satellite communication, for example, and in particular, the transmission of data from a transmitting device is interrupted and another transmission is performed. Even in the case where data is transmitted by switching to the device, a data communication system that takes out a synchronization signal from the reception data after switching the transmission device on the receiving side and continues the receiving operation based on the synchronization signal. About. In addition, the present invention relates to a data communication system which prevents a receiving device from capturing a signal similar to a synchronization signal and causing an erroneous reception operation as a synchronization signal without causing loss of synchronization.

[Summary of the Invention]

According to the present invention, data transmitted by adding a synchronization signal from a transmission device is initially received by confirming that the synchronization signal completely matches in a reception device, and thereafter, synchronization is not easily lost. Therefore, synchronization is lost only when a signal that does not match all or part of the synchronization signal is repeated a certain number of times. Otherwise, reception operation is continued under that synchronization, and synchronization is lost. In such a case, synchronization is achieved by reconfirming the perfect match of the synchronization signal. In a data communication system that performs a synchronous reception operation, when transmission of data from a transmission device is interrupted and data is transmitted after being switched to another transmission device, the reception device may perform a pre-switching operation. Automatically removes synchronization based on the switching information sent from the transmitting device before switching.
By confirming the synchronization based on a perfect match with the synchronization signal from the transmitting device after switching and performing synchronization and receiving operation, the time required for de-synchronization is reduced, and from reception of data after switching to pull-in of synchronization Is to shorten the time.

ADVANTAGE OF THE INVENTION According to this invention, the interruption time of data at the time of transmission apparatus switching can be shortened.

In addition, when detecting out-of-synchronization, in order to prevent out-of-synchronization easily even at low C / N, when a part of the synchronization signal is used instead of using all of the synchronization signals, a signal similar to the synchronization signal is captured. It is intended to prevent an erroneous reception operation from being performed as a synchronization signal without any loss of synchronization.

[Conventional technology]

Currently, the sound of satellite broadcast television is transmitted as PCM data by digital subcarriers (see FIG. 3). In such a data communication system, the transmission data from the transmission device is transmitted with a synchronization signal having a predetermined synchronization pattern added to the head thereof and divided into frames. The receiving apparatus extracts data while synchronizing frames based on the synchronization signal.

Satellite broadcasting can be transmitted from a plurality of transmitting devices. That is, a program can be transmitted from each region based on a broadcast program, and transmission is performed by switching a transmission device. When the transmitting device is switched in this way, the temporal position of the synchronization signal in the data transmitted by each transmitting device before and after the switching does not always match. For this reason, when switching from the transmitting device A to the transmitting device B, it is important that the receiving device properly pull in the synchronization signal of the transmission data from the transmitting device B. Then, data can be correctly extracted based on the synchronization signal.

By the way, in order for the receiving device to not easily lose synchronization, once synchronization is established, synchronization is lost only when a signal that does not match all or part of the synchronization signal continues for a certain number of times, Otherwise, the receiving operation is continued under the synchronization. For this reason, even when the transmission device is switched, it takes a certain time to detect the loss of synchronization after the data from the transmission device before the switching is interrupted. Therefore, it is necessary to suspend the data in consideration of this time.

Also, depending on the receiving device, once the synchronization signal is completely matched and the receiving operation is started, transmission is performed by partial matching of the synchronization signal so that synchronization is not easily lost even at low C / N. Continue receiving data.

For example, in the case of a satellite television, the synchronization signal is composed of 16 bits.
Synchronization is achieved by checking that all 16 bits match, but once synchronization is established, the reception operation is continued by, for example, matching of 12 bits out of 16 bits. Then, when synchronization is lost once and synchronization is re-established, first, check all matches of the 16 bits of the synchronization signal, and thereafter, continue the reception operation only with a partial match of 12 bits of the 16 bits of the synchronization signal. I have.

By the way, the data transmitted from each transmitting device is subjected to fixed scrambling for frequency band spreading,
A signal obtained by performing an exclusive OR operation on the generated PCM data and a pseudo-random signal sequence of one frame period is transmitted. on the other hand
The PCM data includes an area that is not used depending on the operation mode, and all data in this area is 0. As described above, when all data in the specific area is 0, if exclusive OR with the pseudo random signal sequence is performed, the data fixed by frame synchronization, that is, the pseudo random signal sequence, Will appear. In current satellite television, 10th order M
Since the sequence is used and the initialization is performed immediately after the synchronization signal of the transmission data, a signal that partially matches the synchronization signal is generated. Therefore, when fixed scrambling is performed as described above, a signal that does not completely match the synchronization signal but partially matches the synchronization signal in an area that is not used in the operation mode, such as an independent data area, periodically. Will appear in

[Problems to be solved by the invention]

In the conventional data communication system, when the receiving device takes in a new synchronization at the time of switching of the transmitting device, it takes a certain time to temporarily cause the synchronization to be lost. Transmission must be interrupted.

In addition, once the synchronization is achieved, in the case of a receiver that synchronizes by partially matching the synchronization signal and continues receiving operation,
At the time of switching between the transmitting devices, the time positions of the synchronization signals of the transmission data of both transmitting stations do not always match (fifth.
Therefore, there is a possibility that a signal similar to the synchronization signal generated in the 0 data area in the frame signal of the transmitting apparatus B after the switching is taken in and checked. In this case, a signal similar to the synchronization signal is mistaken for the synchronization signal, and synchronization is not lost. Therefore, the synchronization is continued by the partial coincidence of the synchronization signals, so that it is not possible to escape from the state where the wrong synchronization is drawn. In addition, correct reception data cannot be taken out.

Therefore, an object of the present invention is to provide a data communication system for solving these problems.

[Means for solving the problem]

In order to achieve the above object, a data communication system according to the present invention is configured such that, when a receiving device receives digital data transmitted from one of a first transmitting device and a second transmitting device, the receiving device In the above, it is confirmed that the synchronization signals transmitted together with the digital data completely match, and the initial reception is started. Thereafter, a signal which does not match all or a part of the synchronization signals becomes a specific number of times. It is determined that synchronization has been lost only when continuous, and when it is determined that synchronization has been lost, synchronization is confirmed again by confirming the perfect match of the synchronization signal, and thereafter, based on all or partial matching of the synchronization signal, A data communication system for performing a receiving operation while maintaining synchronization, wherein the first transmitting device transmits digital data from the first transmitting device. Switching information transmission means for transmitting switching information indicating that digital data is transmitted by switching to the second transmission device when the transmission is interrupted. In the reception device, the switching information is transmitted from the first transmission device. Switching information detecting means for detecting the switching information, and loss-of-synchronization generating means for forcibly generating a loss-of-synchronization state in a synchronization generation circuit in response to the detection of the switching information. After that, the synchronization establishing process for the digital data signal transmitted from the second transmitting device is started.

Further, the receiving device according to the present invention is a receiving device used in the data communication system, wherein the switching information detecting means for detecting switching information of the transmitting device transmitted from the first transmitting device; An out-of-synchronization generating means for forcibly generating an out-of-synchronization state in the synchronization generation circuit in response to the detection of the switching information, and after the out-of-synchronization state is identified, the transmission of the first transmission device is interrupted. This is to start a synchronization establishment process for a digital data signal transmitted from the second transmission device which is switched later.

(Operation)

The present invention adds the switching information of the transmitting device to the data to be transmitted and transmits the data, and the receiving side automatically loses synchronization based on this information, and the transmitted data after the switching is received. As soon as the synchronization signal is completely matched, synchronization is achieved, and thereafter, the receiving operation is performed while maintaining synchronization based on all or partial matching of the synchronization signal. In other words, the data communication system is capable of promptly achieving appropriate synchronization even when the transmission device is switched.

〔Example〕

One embodiment of the present invention is shown in FIG. The data communication system shown in FIG. 1 includes a plurality of transmitting devices and receiving devices. Each transmitting device includes a data multiplexing unit and a modulation unit. The receiving device includes a demodulation unit, a synchronization generation unit, a data decoding unit, and a transmission device switching information detection unit.

The data input to the transmission device is taken into a predetermined area in the format shown in FIG. 3 in a predetermined position and order by a data multiplexing unit, and the synchronization signal and the structure information / switching information of the data format are converted for each frame. A control signal including the control signal is added and multiplexed. The multiplexed data is modulated by the modulator and transmitted. Each transmission device is switched and used to perform transmission from a different area based on, for example, a program schedule timetable. A plurality of transmitting devices do not perform a transmitting operation at the same time.

The receiving apparatus demodulates the modulated transmission data signal in a demodulation section, obtains a read timing of data from a synchronization signal included in the transmission data in a synchronization generation section, and multiplexes the data multiplexed based on the timing information in a data decoding section. Decompose the signal and extract individual data. In the synchronization generator, when starting to receive transmission data for the first time, synchronization is confirmed by confirming the coincidence of all bits of the synchronization signal, and thereafter, synchronization is checked based on all or partial coincidence of the synchronization signal to read data. However, it generates timing information. The transmission device switching detection unit detects the transmission device switching information included in the control signal in the PCM format of the satellite broadcast television, for example, and after a predetermined time, the transmission device after the switching enters the data transmission state for a predetermined period Over this time, the synchronization generation unit is controlled so as to cause loss of synchronization.

Control code b ₁₅ in PCM format of the aforementioned satellite TV is for data of various data broadcasting services using the data channel is provided so that it can reliably receive consecutive in the transmitting apparatus before and after switching (the 4), the information is always transmitted before and after the switching of the transmission device. The data of the transmitting device before the switching is invalid data after 36 ms from the reception of this signal, and the data from the transmitting device after the switching is canceled and the data up to 36 ms is invalid. In this embodiment, this control signal is used as switching information of the transmission device.

 The operation at the time of switching the transmitting device is as follows.

First, the control signal information is transmitted from the transmitting device A before the switching of the transmitting device. In the receiving apparatus, as shown in FIG. 2, this information is detected by the transmitting apparatus switching information detecting section, and based on this information, the synchronization generating section is controlled so that synchronization is lost for a fixed time after 36 ms. After the elapse of the predetermined time, the transmitting device B after the switching is in the transmitting state, and valid data is transmitted for the synchronization signal and the control signal. By doing so, it is possible to promptly enter the operation for pulling in a new synchronization signal and to make the transmission from the transmission device B easier than in the case where the synchronization from the transmission device before switching is lost due to interruption of the data from the transmission device. After the start, the receiver always performs the receiving operation from the beginning. A comparison with the operation of the receiver when such control is not performed is shown in the lower part of FIG. In this way, the receiver always synchronizes after confirming that all the synchronization signals completely match, and thereafter performs the operation of synchronizing by all or partial coincidence of the synchronization signals to acquire a correct synchronization signal. . That is, even when the transmission device is switched, it is possible to always receive accurate data.

〔The invention's effect〕

According to the present invention, when data transmission from a transmission device is switched to another transmission device, data to which switching information is added is transmitted before switching the transmission device, and synchronization is performed based on this information at the reception device side. Since the synchronization is lost and the reconfirmation of the perfect match of the synchronization signal is started by this, the data is interrupted for a shorter time compared to the case where the synchronization is lost due to the interruption of the data from the transmitting device before the switching. Data communication becomes possible.

In addition, an erroneous signal similar to the synchronizing signal is taken in as a synchronizing signal, and an erroneous receiving operation is not performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a data communication system according to one embodiment of the present invention, FIG. 2 is a diagram showing operation timing of a receiver, FIG. 3 is a diagram showing a PCM audio transmission format of satellite broadcasting, FIG. 4 is an assignment diagram of frame control codes, and FIG. 5 is an explanatory diagram of a phase shift of frame synchronization of transmission data before and after switching of the transmission device. 2, 6: Data multiplexing unit, 4, 8: Modulation unit, 10: Demodulation unit, 12: Synchronization generation unit, 14: Data decoding unit, 16: Transmission device switching information detection unit.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akio Yanagimachi 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute of Broadcasting Technology (56) References JP-A-61-276434 (JP, A) 63-126333 (JP, A)

Claims (2)

(57) [Claims] When receiving digital data transmitted from one of a first transmitting apparatus and a second transmitting apparatus by a receiving apparatus, the receiving apparatus receives a synchronization signal transmitted together with the digital data. Start the initial reception after confirming that they completely match, and then determine that synchronization has been lost only when a signal that does not match all or a part of the synchronization signal continues for a specific number of times.
If it is determined that the synchronization has been lost, data communication is performed again by confirming the complete match of the synchronization signal and synchronizing, and thereafter performing the receiving operation while synchronizing based on all or partial coincidence of the synchronization signal. In the system, in the first transmission device, when interrupting the transmission of digital data from the first transmission device, switching information indicating that the digital data is transmitted by switching to the second transmission device. Switching information transmitting means for transmitting the switching information, wherein in the receiving device, switching information detecting means for detecting the switching information transmitted from the first transmitting device; and in response to the detection of the switching information, An out-of-synchronization generating means for forcibly generating an out-of-synchronization state in the circuit; Data communication system, characterized in that to start the synchronization establishment process for the digital data signal transmitted from the transmitting device. 2. A receiving apparatus for use in the data communication system according to claim 1, wherein: switching information detecting means for detecting switching information of the transmitting apparatus transmitted from the first transmitting apparatus; An out-of-synchronization generating means for forcibly generating an out-of-synchronization state in the synchronization generation circuit in response to the detection of the switching information, and after the out-of-synchronization state is identified, the transmission of the first transmitting apparatus is interrupted. A receiver for use in a data communication system, which starts synchronization establishment processing for a digital data signal transmitted from a second transmitter which is switched later.