JPH0294840A - Data communication system - Google Patents

Abstract

PURPOSE:To reduce data interruption time attended with switching by sending a data with switching information prior to the switching of a transmitter, allowing a receiver side to cause synchronizing step-out based on the information, thereby starting the reconfirmation of complete coincidence of a synchronizing signal. CONSTITUTION:A synchronization generating section 12 in a receiver confirms the coincidence of all bits of the synchronizing signal at the start of reception at first to take synchronization, decides it to be the synchronizing step-out only when a dicordant signal is consecutive for a prescribed number of times to all or a part of the synchronizing signal after that and checks the synchronization to generate readout timing information. In the case of switching the transmitter, control signal information including switching information from the transmitter A is sent from the transmitter prior to the switching of the transmitter at first. A transmitter switching information detection section 16 of the receiver detects the information and controls a synchronization generating section 12 to cause the synchronizing step-out for a prescribed time based thereupon. After the prescribed time elapses, the transmitter B after the switching is in the transmission state and after the transmission from the transmitter is started, the receiver implements the reception from the start without fail.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a data communication system that transmits digital data, such as satellite communication, and in particular, the present invention relates to a data communication system that transmits digital data, such as satellite communication. A data communication system in which, even when data is transmitted by switching to another device, the receiving side extracts a synchronization signal from the received data after switching to the transmitter, and continues receiving operations based on this synchronization signal. Regarding. The present invention also relates to a data communication system that prevents a receiving device from capturing a signal similar to a synchronization signal and using it as a synchronization signal to perform an erroneous reception operation without causing synchronization.

[Summary of the invention]

The present invention performs initial reception of data transmitted from a transmitting device with a synchronizing signal added thereto by confirming that the synchronizing signals completely match in a receiving device, and thereafter the synchronization is not easily lost. In order to ensure that all or part of the synchronization signal is a monarchy, the synchronization will be lost only if No. 8 is repeated a certain number of times in a row, otherwise the reception operation will continue under that synchronization, and the synchronization will continue. If the synchronization signal is out of alignment, check again that the synchronization signals match completely and synchronize.
From then on, data transmission from the transmitter will be interrupted in data communication systems that perform synchronous reception operations under that synchronization, unless a signal that does not match all or part of the synchronization signal occurs a certain number of times in a row. When data is transmitted by switching to another transmitting device, the receiving device automatically removes synchronization based on the switching information sent from the previous transmitting device and transmits the data after switching. By confirming the synchronization by completely matching the synchronization signal from the transmitter, synchronizing, and performing the reception operation,
This shortens the time required to lose synchronization and the time from reception of data after switching to synchronization pull-in.

According to the present invention, it is possible to shorten the data interruption time when switching between transmitting devices.

In addition, when detecting out of synchronization, in order to prevent out of synchronization easily even when the C/N is low, when using a part of the synchronization signal instead of all of it, a signal similar to the synchronization signal is captured, This prevents an erroneous reception operation by using this signal as a synchronization signal without causing synchronization loss.

[Conventional technology]

Currently, satellite TV audio is transmitted as PCM data using digital subcarriers (see Figure 3).
. In such a data communication A2 system, data to be transmitted from a transmitter is appended with a synchronization signal having a predetermined synchronization pattern at the beginning of the data, and is divided into frames and transmitted.

The receiving device extracts data while synchronizing frames based on this synchronization signal.

Satellite broadcasting can be transmitted from multiple transmitting devices.

That is, programs can be transmitted from each region based on the broadcast program organization, and transmission is performed by switching transmission devices. When the transmitting devices are switched in this way, the temporal positions of the synchronization signals in the data transmitted by the eight transmitting devices before and after the switching do not necessarily match. Therefore, when switching from transmitting device A to transmitting device B, it is important for the receiving device to accurately pull in the synchronization signal of the transmission data from transmitting device B. This makes it possible to correctly extract data based on the synchronization signal.

By the way, in order to prevent the receiving device from easily becoming out of synchronization, once synchronization has been established, the receiving device will lose synchronization only if a signal that does not match all or part of the synchronization signal occurs a certain number of times in a row. , otherwise continue receiving operations under that synchronization. For this reason, even when switching the transmitting device, a certain amount of time is required until the synchronization is detected after the data from the transmitting device before switching is interrupted. Therefore, it is necessary to interrupt data taking this time into consideration.

Also, depending on the receiving device, after the - degree synchronization signals completely match and start receiving operation, in order to prevent synchronization from being easily lost even when the C/N is low, some receivers may use a partial match of the synchronization signals to prevent synchronization from being easily lost even when the C/N is low. Continuing to receive transmitted data.

For example, in the case of satellite TV, the synchronization signal consists of 16 bits, and the receiving device synchronizes by checking that all 16 bits match on the first reception. After establishment, the receiving operation continues depending on a match of, for example, 12 bits out of 16 bits. If synchronization is lost and synchronization is to be re-established, first check if all 16 bits of the synchronization signal match, and then continue receiving operation with only a partial match of 12 bits of the 16 bits of the synchronization signal. There is.

By the way, the data transmitted from each transmitting device is fixedly scrambled to spread the frequency band, and a signal obtained by exclusive ORing the generated PCM data and a pseudo-random signal sequence synchronized with one frame is Sent. On the other hand, the PCM data has an area that is not used depending on the operation mode, and all data in this area is 0. In this way, when the data in a specific area is all 0, if you take an exclusive OR with the pseudo-random signal sequence, the data fixed by frame synchronization, that is, the pseudo-random signal sequence, becomes the data in the specific data area. There is a lot of shouting when it appears. Current satellite television broadcasts have 10 pseudo-random sequences.
Since the next M sequence is used and initialized immediately after the synchronization signal of the transmission data, a signal that partially matches the synchronization signal is generated. Therefore, when fixed scrambling is applied as described above, a signal that does not completely match but partially matches the synchronization signal may periodically appear in an area that is not used depending on the operation mode, such as an independent data area. It will appear in

(Problems to be Solved by the Invention) In conventional data communication systems, when a receiving device acquires new synchronization when switching between transmitting devices, it takes a certain amount of time for the receiving device to lose synchronization. It is necessary for the data transmission side to suspend data transmission for a period that takes this time into consideration.

In addition, in the case of a receiver that synchronizes and continues receiving operation by a partial coincidence of the synchronization signals after synchronization is achieved, when switching the transmitter, the time position of the synchronization signal of the transmitted data of both transmitting stations Since they do not necessarily match (see FIG. 5), there is a possibility that a signal similar to the synchronization signal generated in the O data area of the frame signal of transmitter B after switching is taken in and checked. In that case,
A signal similar to this synchronization signal will be mistaken for a synchronization signal, and no synchronization will occur. Therefore, since synchronization is subsequently achieved by partial coincidence of the synchronization signals, it becomes impossible to escape from a state in which incorrect synchronization has been drawn. Furthermore, it becomes impossible to extract the correct received data.

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

[Means to solve the problem]

In order to achieve such an object, in the data communication system according to the present invention, data transmitted from a transmitter with a synchronization signal added thereto is initially received by the receiver after confirming that the synchronization signals completely match. After that, in order to prevent synchronization from being easily lost, synchronization is only considered to be lost if a signal that is inconsistent with all or part of the synchronization signal occurs a certain number of times in a row, and if not, the synchronization is If synchronization is lost, synchronization is established by reconfirming that the synchronization signals completely match, and from then on, the reception operation continues while synchronizing based on the complete or partial match of the synchronization signals. In this data communication system, when data transmission from a transmitting device is interrupted and data is transmitted by switching to another transmitting device, the transmitting device before switching sends switching information, and the receiving device side Based on this information, the synchronization generation circuit causes out-of-synchronization, thereby controlling the synchronization signal from the transmitting device after switching to be quickly pulled in, shortening the interruption time of data due to switching, and It has a communication control function that prevents a signal similar to the above from being erroneously pulled in as a synchronization signal and performing an erroneous data retrieval operation.

(Function) The present invention adds switching information of the transmitting device to the transmitted data and transmits the data, automatically causes synchronization loss based on this information on the receiving side, and transmits the data after switching. As soon as data is received, synchronization is established by immediately confirming that the synchronization signals completely match, and thereafter, reception operations are performed while synchronizing based on the complete or partial match of the synchronization signals. In other words, the data communication system is capable of always achieving accurate synchronization quickly even when the transmitter is switched.

(Embodiment) An embodiment of the present invention is shown in FIG. 1. The data communication system shown in the figure is composed of a plurality of transmitting devices and receiving devices. Each transmitting device has a data multiplexing section and a modulating section. The receiving device includes a demodulating section, a synchronization generating section, a data decoding section, and a transmitting device switching information detecting section.

The data input to the transmitting device is inputted into a predetermined area in the format shown in Fig. 3 in a predetermined position and order in a data multiplexing section, and a synchronization signal and data format structure information/switching information are transmitted for each frame. A control signal including a control signal is added and multiplexed. The multiplexed data is modulated by a modulator and transmitted. Each transmitting device is used in a switched manner to transmit data from different areas based on, for example, a programming timetable. Multiple transmitting devices do not perform transmitting operations at the same time.

The receiving device demodulates the modulated transmission data signal in the demodulation section, obtains the data read timing from the synchronization signal included in the transmission data in the synchronization generation section, and converts the multiplexed data signal based on the timing information in the data decoding section. Disassemble and extract individual data. When the synchronization generator first starts receiving transmission data, synchronization is achieved by checking that all the bits of the synchronization signal match. From then on, synchronization is checked based on the complete or partial match of the synchronization signals, and the data is read. Generates timing information. In the transmitting device switching detection section, for example, the P of satellite broadcast television
Detects the transmitting device switching information included in the control signal in the CM format, and controls the synchronization generator to cause synchronization loss for a certain period of time from a certain period of time until the switched transmitting device enters the data transmission state. do.

The control code b15 in the PCM format of the satellite broadcast television mentioned above is provided to ensure that the data of various data broadcasting services using the data channel can be continuously and reliably received before and after switching the transmitter.
(see FIG. 4), is information that is always sent before and after switching the transmitting device. The data of the transmitting device before switching is invalid data after 36m5 after receiving this signal, and the data from the transmitting device after switching up to 36m5 with this code removed is also invalid. In this embodiment, this control signal is used as switching information for the transmitter.

The operation when switching the transmitter is as follows.

First, this control signal information is sent from transmitter A before switching the transmitter. In the receiving device, the transmitting device switching information detection unit detects this information as shown in Fig. 2, and
Based on this, the synchronization generator is controlled to cause synchronization to occur for a certain period of time after 36m5. After this certain period of time has elapsed, the switched transmitting device B is in a transmitting state, and valid data is being transmitted for synchronization signals and control signals. By doing this, it is possible to start the pull-in operation to the new synchronization signal more quickly than when synchronization occurs due to interruption of data from the transmitter B before switching, and the transmission from transmitter B is After being started, the receiver always performs the receiving operation from the beginning. A comparison with the receiver operation without such control is shown in the lower part of FIG. In this way, the receiver always performs synchronization after confirming that all synchronization signals completely match, and thereafter performs synchronization operations based on all or partial matches of the synchronization signals to capture the correct synchronization signal. . That is, even if the sending device 2 is switched, it is possible to always receive data accurately.

〔Effect of the invention〕

According to the present invention, when switching data transmission from a transmitting device to another transmitting device, before switching the transmitting device, data with switching information added is transmitted, and the receiving device side synchronizes based on this information. This causes synchronization to start reconfirming that the synchronization signals are completely consistent, so compared to the case where synchronization is caused by an interruption in data from the transmitting device before switching, the synchronization is caused by a shorter period of data interruption. Data communication becomes possible.

Further, an incorrect signal similar to a synchronization signal is not taken in as a synchronization fX signal and an incorrect reception operation is not performed, and an accurate reception operation can always be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a data communication system that is an embodiment of the present invention, FIG. 2 is a diagram showing the operation timing of the receiver, and FIG. 3 is a diagram showing the PCM audio transmission format of satellite broadcasting. FIG. 4 is an allocation diagram of frame control codes, and FIG. 5 is an explanatory diagram of a phase shift in frame synchronization of transmission data before and after switching the transmitter. 2.6...Data multiplexing unit, 4.8...Modulation unit, IO...Demodulation unit, 12...Synchronization generation unit, 14...Data decoding unit, 16...Transmission device switching information Detection part. □ Figure 3 shows the PCM audio format 1-mat (configuration of 1 frame) of the 2048 Hinode, Ims 1 family.

Claims (1)

[Claims] 1) Data transmitted from a transmitter with a synchronization signal added is initially received by the receiver after confirming that the synchronization signals completely match, and thereafter synchronization is performed. In order to prevent this from occurring easily, the synchronization is determined to be lost only when a signal that is inconsistent with all or part of the synchronization signal occurs a certain number of times in a row, and if not, the reception operation continues under that synchronization. , if the synchronization is lost,
A data communication system that reconfirms the complete match of the synchronization signals to establish synchronization, and thereafter performs reception operations while maintaining synchronization based on the complete or partial match of the synchronization signals, and the transmission of data from the transmitting device is When the transmission is interrupted and data is transmitted by switching to another transmitter, the transmitter before switching sends switching information, and the synchronization generating circuit on the receiver side uses this information to cause the synchronization to go out of synchronization. , controls to quickly pull in the synchronization signal from the transmitter after switching, shortens the data interruption time due to switching, and prevents signals similar to the synchronization signal from being mistakenly pulled in as a synchronization signal, resulting in incorrect data being retrieved. A data communication system characterized by having a communication control function that prevents the operation from occurring.