JP2650317B2 - Broadcast control method in wireless communication system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling broadcast communication by wireless communication, and in particular, to a wireless communication system for communicating information between slave stations via a master station. In the broadcast communication control method described above.

[Conventional technology]

Conventional broadcast control methods in the field of wireless communication include:
For example, as disclosed in JP-A-60-85631, a method in which broadcast information is transmitted only unilaterally from a transmitting station to a receiving station, and response information from the receiving station to the transmitting station is not transmitted It is common to take This method can be applied when sufficient line quality can be ensured and the information error rate can be sufficiently reduced, or when information errors do not cause operational problems. An example is a screen transmission with a high degree of information redundancy, such as a TV broadcast. The same applies to the case of digital communication. However, a method is employed in which error control information is further added, an error detection / correction mechanism for information is provided, and the error rate of information is reduced.

Conventional broadcast control methods in the field of wired communication are:
In addition to the same method as the above wireless communication,
As disclosed in Japanese Patent No. 3993, a method of transmitting response information from a receiving station of broadcast information to a transmitting station using time division communication may be adopted. Also, as disclosed in Japanese Patent Application Laid-Open No. 61-84140, a broadcasting-only transmitting station is provided, and this broadcasting-only transmitting station is used instead of another station (broadcast requesting station). There is a method for controlling broadcast communication.

[Problems to be solved by the invention]

As described above, in the conventional broadcast communication system, all the stations that receive the broadcast information frame (that is, the slave stations) are connected to the station that transmits the broadcast information frame (that is, the parent station). To the station, (1) no response frame is transmitted, or (2) a response frame is transmitted each time a broadcast information frame is received.

When the response frame of the above (1) is not transmitted, it is obvious that the reliability of the received information in each slave station cannot always be ensured because confirmation of arrival is not taken. on the other hand,
In the method of transmitting a response frame every time a broadcast information frame is received in (2), when retransmission occurs due to abnormal reception of a certain slave station, the master station continues the next (continuous transmission possible) until the retransmission processing is completed. The control method cannot transmit a broadcast information frame (following an allowable continuous transmission frame), and thus has a problem in that the throughput of the entire broadcast communication system is reduced. The problem is that, as the number of slave stations increases, the frequency of retransmission processing increases, so that the reception processing overhead for response frames in the master station increases, and the throughput of the entire broadcast communication system further decreases. .

On the other hand, there is a method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-84140, in which a broadcasting-only transmitting station is provided, and the broadcasting-specific transmitting station controls the broadcasting. is there.
However, in this system, there is a problem in that the system cost is increased by newly providing a transmission station dedicated to broadcast communication to perform processing related to broadcast communication.

The first object of the present invention has been made in view of the above circumstances, and aims at solving the above-mentioned problems in the conventional broadcast communication system, simplifying the broadcast control, and An object of the present invention is to provide a broadcast communication control method in a wireless communication system, which does not cause a rise in system cost accompanying a broadcast service.

A second object of the present invention is to reduce unnecessary retransmission by a master station and to secure a throughput related to broadcast communication.

[Means for solving the problem]

In order to achieve the above object, a broadcast control method in a wireless communication system according to the present invention is directed to a wireless communication system in which bidirectional communication of information between slave stations is performed in a frame unit via a master station by wireless. The slave station requesting the broadcast sets destination information (A) indicating the broadcast in the address field of the header of the frame, and sets a data type indicating whether the frame is for data or response data in the header. Information (R) and sub-address information (SA) used to identify the own station, and transmit the same. The master station adds the destination information (A) and the data type information (R) of the header of the frame received from the slave station to the destination. When the information frame to be broadcast is recognized based on this, this frame is transmitted in the same format,
The slave station requesting the broadcast analyzes the header of the frame received from the master station, and based on the destination information (A) and the subaddress information (SA), the frame is the frame of the broadcast request requested by itself. In this case, the completion of the broadcast communication by the master station for this frame is detected.

[Action]

In the broadcast control method in the wireless communication system according to the present invention, a slave station having broadcast information transmits the broadcast information to a master station, and the master station transmits all broadcast information to the master station by means of a frame header analyzing means. Broadcast the broadcast information frame to the station;
By detecting the completion of the transmission of the broadcast information frame by the master station by the slave station having the broadcast information, the master station can control the completion of the transmission of the broadcast information without notifying the slave station.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following explanation, VSAT (Very Small Aparture Termin
al) In the system, a case where a broadcast service is realized will be described as an example.

Note that the present invention is not realized only in a satellite communication system such as a VSAT system, but is a wireless communication system in which information communication between slave stations is performed wirelessly and via a master station, such as a VSAT. Can be realized.

Before describing a specific embodiment, an outline of a VSAT system will be described with reference to FIG. In the figure, 1 is a satellite,
Reference numeral 2 denotes a master station (hereinafter, referred to as “Hub station”) in the VSAT system, and 3i (i = a to n) denotes slave stations (hereinafter, referred to as “VSAT station”) in the VSAT system. The Hub station 2 and the VSAT station 3i are connected to an information processing device related to data, voice, images, and the like, but are omitted here.

Generally, the Hub station 2 has a parabolic antenna with a diameter of several meters, and each VSAT station 3i has a diameter of 1 to 2 meters. In such a VSAT system, since the antenna size of each VSAT station 3i is small, its gain is small and each VSAT station 3i
There is no direct communication between them. Naturally, if the repeater gain of the satellite 1 becomes large, communication between the VSAT stations 3i having a parabolic antenna having a diameter of 1 to 2 meters becomes possible, but in that case, the system cost is reduced and the installation is easy. Therefore, it is necessary to further reduce the antenna size in order to achieve the realization, and it is still possible that direct communication cannot be performed between the VSAT stations 3i. Accordingly, communication between the VSAT stations 3i is realized via the Hub station 2. In this case, a line 4 (hereinafter referred to as “in-band”) from each VSAT station 3i to the hub station 2 via the satellite 1
Is called TDMA (Time Division Multiple Access)
Depending on the system, and each VSAT from Hub station 2 via satellite 1
Line 5 to station 3i (hereinafter referred to as "outband") is TD
Generally, the M (Time Division Multiplexer) method is used.
It is provided to a later-described line control device 8 of the station 2.

In this way, by specifying a partner station between the VSAT stations 3i, n: n communication can be realized. The above is the outline of the VSAT system.

An embodiment of the present invention realized in the VSAT system will be described below.

FIG. 1 is a configuration diagram showing an outline of a VSAT system that realizes a broadcast service. In the figure, the same reference numerals as those in FIG. 2 indicate the same means. In the Hub station 2 and each VSAT station 3i shown in FIG. 1, 6 and 7i are transmission / reception devices, 8 and 9i are line control devices, 10 and 11i are broadcast control devices, and 12 and 13i are Hub stations 2 and each
It shows an information processing device (hereinafter, referred to as “processing device”) such as a computer and a terminal connected to the VSAT station 3i.

Next, the operation of the system shown in FIG. 1 will be described by dividing it into (1) normal communication operation and (2) broadcast communication operation.

(1) Normal communication operation The normal communication operation is performed by performing communication between the VSAT stations 3i and 3j, that is, transmitting data in the processing device 13i connected to the VSAT station 3i to the processing device 13j connected to the VSAT station 3j. The case of transfer will be described as an example.

When the processing device 13i sends data with a transmission destination address (here, j) to the line control device 9i of the VSAT station 3i via a signal line 15i including a bidirectional data line, the line control device 9i The data is further transmitted to the transmission / reception device 7i, and the transmission / reception device 7i transmits the data to the hub station 2 via the satellite 1 using the time slot allocated to the VSAT station 3i of in-band 4. I do.

In the hub station 2, the line control device 8 having received the data via the transmission / reception device 6 sends the data to the transmission / reception device 6 in order to transmit the data using the out-of-band 5 with the address j attached. . The transmitting / receiving device of each VSAT station continuously receives data of outband 5, and the VSAT station
The line controller 9j of 3j selectively extracts data having the address j from the continuously received data.
The line controller 9j sends the extracted data to the processor 13j via the signal line 15j. In many communication protocol rules,
It is common to return a response from the processing device 13j to the processing device 13i, but only the transmission path is in reverse order to the data,
The other sequence is the same as the case of data, and the description is omitted.

The above is the outline of the normal communication operation in the VSAT system.

(2) Broadcast communication operation The processing device 13i connected to the VSAT station 3i has broadcast data, and transmits the broadcast data to the other VSAT stations 3a to 3n (excluding 3i) and the Hub station 2 all at once. Will be described.

The processing device 13i sends broadcast data to the broadcast control device 11i via a signal line 17i including a bidirectional data line. The configuration and operation of the broadcast control device 11i will be described later in detail. The broadcast communication control device 11i attaches a code (here, “0”) indicating that it is broadcast data as an address of a transmission destination, and a signal line including a bidirectional data line.
The broadcast data is sent to the transmission / reception device 7i via the line control device 9i via 19i.

The transmission / reception device 7i transmits the broadcast data to the hub station 2 via the satellite 1 using the time slot allocated to the in-band 4 VSAT station 3i. In the hub station 2, the line control device 8, which has received the broadcast data via the transmission / reception device 6, recognizes that the data is broadcast data since the address is "0", and performs the broadcast communication. Control device
At the same time, the broadcast data is transmitted to 10 (the detailed configuration and operation thereof will be described later) via the signal line 18 and the broadcast data is transmitted to the transmission / reception device 6 for transmission using the out-of-band 5. .

The transmitting / receiving device 7i of each VSAT station continuously receives data of outband 5, and the line control device 9j of the VSAT station 3j (including j = a to n, i) continuously receives data. The data whose address is "0" is recognized as the broadcast data from the stored data and selectively extracted. The line controller 9j sends the extracted broadcast data to the broadcast controller 11j via the signal line 19j. The broadcast communication control device 11j sends the broadcast data to the processing device 13j via the signal line 17j, and at the same time, creates response data to the broadcast data and sends the response data to the line control device 9j via the signal line 19j. , And further to the transmitting / receiving device 7j.

The transmission / reception device 7j transmits the response data to the hub station 2 via the satellite 1 using the time slot assigned to the VSAT station 3j in the in-band 4. When the line control device 8 receives the response data via the transmission / reception device 6 and recognizes that the data is response data, the line control device 8
The response data is sent to signal line 10 via signal line 18. The broadcast control device 10 analyzes response data from each of the VSAT stations 3j (j = a to n), and retransmits the previously transmitted broadcast data if retransmission is necessary. The transmission sequence accompanying the retransmission is 1
This is the same as the case where the broadcast data is transmitted the second time. When it is determined that retransmission of the broadcast data is not necessary, the series of control sequences ends when the broadcast control device 10 determines.

As an overview, the repetition of the control related to the length of the broadcast data and the control termination sequence, that is, the method in which the processing device 13i recognizes the completion of the control sequence and the like are omitted. This will be described when describing the configuration and operation of the communication control devices 10 and 11i.

FIG. 3 shows a transmission frame format used in the present system. The transmission frame format shown in Fig. 3 is the frame format of the HDLC procedure (JIS C-6363).
, Except for the R and SA fields. In FIG. 3, F is a flag field, A is an address field,
C is a control field, R is a data / response identification field, SA is a subaddress field, D is an information field, and FCS is a frame check sequence field.

Among the above fields, R and SA are not included in the HDLC procedure but are newly added fields. Field F,
The usage of C and FCS is based on the HDLC procedure (JIS C-6364 and 636).
Since it is the same as 5), the description is omitted. For convenience of explanation, the fields A to SA will be referred to as headers.

FIG. 4 shows how to use each field of the transmission frame format shown in FIG. In the figure, "N
"o." is the type number of the transmission frame format added for convenience of explanation. “Type” indicates a communication mode type, and indicates one-to-one communication and broadcast communication. “Case” indicates a data transmission direction and the like in each communication mode. The “data / response type” indicates whether data or a response is transmitted in each case. "Line" indicates whether the information indicated by the data / response type is transmitted in-band 4,
Indicates whether the signal is transmitted in outband 5. Each of the above items is shown for convenience of explanation.

Next, items A, R, SA and D represent each field of the same code in the transmission frame format shown in FIG. The ￥ symbol in the item A and SA columns indicates that the subsequent character string is a hexadecimal number. For example, “￥ FE” is (11111110)
Is shown. In the following description, the addressing of each station is as follows. That is, the address of the Hub station 2 is set to {FF, and the address of the VSAT station 3i (i = a to n) is set to 1 to {}.
The FEs are set so as to have a one-to-one correspondence (so that the addresses of the respective stations are different). As described above, the address “0” is used when the transmission frame is involved in the broadcast. Item R represents data when "0", and response data when "1". Item D represents the contents of the information field, that is, data or response data.

Under the above arrangement, some transmission frame formats will be described.

First, the No. 1 transmission frame format will be described. This transmission frame format is a transmission frame format when the Hub station 2 transmits data to a specific VSAT station 3i (address: i). At this time, the address i of the VSAT station 3i as the transmission partner is set in the field A. Since the content to be transmitted is data, "0" is set in the field R. In field SA, Hub station 2
Set the own station address (￥ FF) of Further, data to be transmitted is set in the field D. At this time,
If the length of the data to be transmitted is longer than the length of the field D, a new transmission frame is configured to transmit data corresponding to the longer length. That is, when the data to be transmitted is long, the data is transmitted by a plurality of frames. In this case, a series of plural frames are managed by the transmission sequence number. However, since this system also follows the standard procedure of the HDLC procedure (JIS C-6364 and 6365), the description is omitted.

Next, the No. 2 transmission frame format will be described. In the transmission frame format, when the Hub station 2 transmits data to a specific VSAT station 3i, the VSAT station 3i that has received the data transmits the reception state of the data to the Hub station 2 as response data. Is the transmission frame format. The difference between the transmission frame format of No. 2 and the transmission frame format of No. 1 is only the set value of the field R, but since it is a transmission frame of the VSAT station 3i, only the hub station 2 can receive. , Hub Station 2
Is distinguishable from other transmission frame formats.

Next, a transmission frame format related to broadcast communication will be described. The transmission frame format of No. 7 is a transmission frame format when a certain VSAT station 3i has broadcast data and transmits it. Field A
Is set to "0" indicating that the data is broadcast data. Since the content to be transmitted is data, "0" is set in the field R. Field SA has VSAT station 3i
Set the own station address i. In the field D, broadcast data to be transmitted is set. At this time, if the length of the broadcast data to be transmitted is longer than the length of the field D, the method described in the description of the No. 1 transmission frame format is used.

Next, the transmission frame format No. 8 used when the Hub station 2 that has received the No. 7 transmission frame further transmits to all the VSAT stations 3i (i = 1, 2,..., N) explain. The transmission frame format of No. 8 is exactly the same as the transmission frame format of No. 7, but there are differences between the in-band 4 and the out-band 5 in the transmission lines, and the receiving station Since it is limited to the station 2 or the VSAT station 3i, its identification is possible.

Finally, the No. 9 transmission frame format will be described. This is a transmission frame format when each VSAT station 3i responds to the transmission frame format of No. 8, and only the setting values of the field R differ from the transmission frame formats of No. 7 and No. 8. . Therefore,
Hub station 2, which receives the transmission frames No. 7 and No. 9,
The transmission frame is identified based on the difference in the field R.

Regarding the transmission frame formats of No.3 to No.6,
Since it is considered that the above description of each transmission frame format and the description in FIG. 4 can be sufficiently understood, the description is omitted. In addition to the transmission frame format shown in FIG. 4, for example, a line setting command, a disconnection command, or a response command to these are used.
These commands use HDLC procedures (JIS C-6364 and 636
The description will be omitted because it conforms to 5).

FIG. 5 shows the configuration of the line control device 8 in the Hub station 2. In the figure, reference numeral 80 indicates the transmission of a carrier wave of outband 5,
A control unit for setting a time reference for the in-band 4 and managing time slots, etc., 81 is a reception buffer, 82 is a transmission buffer, 83 is a header analysis unit, and 84 and 85 are interface units. The interface unit 84 is connected to the processing device 12 via the signal line 14, and the interface unit 85 is connected to the broadcast control device 10 via the signal line 18.

In order to explain the operation of the line control device 8, a processing flow of the header analysis unit 83 is shown in FIG. In FIG. 6, the header analysis unit 83 determines whether or not there is a transmission frame (the reception frame of No. 2, 3, 4, 6, 7, 9) in the reception buffer 81 in step 83a. If there is no transmission frame in the reception buffer 81, the step 83a is repeated. Receive buffer 81
If there is a transmission frame, one frame is extracted from the reception buffer 81 in step 83b. Next, it is determined whether or not the field A of the transmission frame extracted in step 83c is "0". If the field A is "0", the process proceeds to step 83h. If the field A is not "0", it is determined in a step 83d whether or not the field A is "$ FF". If the field A is "@FF", the process proceeds to step 83g. If the field A is not "@FF", it is determined in a step 83e whether or not the field SA is "@FF". If the field SA is "$ FF", the flow proceeds to step 83g. If the field SA is not "$ FF", the flow advances to step 83f to store the transmission frame in the transmission buffer 82.
And returns to step 83a. The transmission frame up to this step 83f is the transmission frame No. 3 or No. 4 shown in FIG.

Next, step 83 is branched from step 83d or 83e.
In g, the transmission frame is output to the signal line 14 via the interface unit 84, and the process returns to step 83a. The transmission frame leading to this step 83g is No. 2 shown in FIG.
Or it is a No. 3 transmission frame. The case where the No. 3 transmission frame of the same transmission frame type reaches step 83f or step 83g is that the address of the field A of the frame is the address of the VSAT station 3i or the address of the Hub station 2. It depends.

Next, a case where it is determined in step 83c that the field A is “0”, that is, a case where the frame is a transmission frame related to broadcast, will be described from step 83h. In step 83h, it is determined whether or not the field R of the transmission frame is “0”. If the field R is "0", the transmission frame is written to the transmission buffer 82 in step 83. The transmission frame written in the transmission buffer 82 is the transmission frame No. 7 in FIG. When this No. 7 transmission frame was written to the transmission buffer 82,
It is regarded as the No. 8 transmission frame in FIG. Subsequently, in step 83j, the transmission frame is output to the signal line 18 via the interface unit 85, and the process returns to step 83a. on the other hand,
The frame that reaches step 83j without passing through step 83i is the No. 6 or No. 9 transmission frame in FIG. This concludes the description of the header analysis unit 83 shown in FIG.
Hereinafter, transmission frames that do not pass through the header analysis unit 83 will be described.

The transmission frames that do not pass through the header analysis unit 83 are the transmission frames No. 1 and No. 5 in FIG. The No. 1 transmission frame is input from the signal line 14 to the line controller 8 through the interface unit 84 in FIG. Similarly, the transmission frame of No. 5
The signal is input from the signal line 18 to the line controller 8 via the interface unit 85, and is directly written into the transmission buffer 82.

FIG. 7 shows the configuration of the line control device 9i of the VSAT station 3i.
In the figure, reference numeral 90 denotes a control unit for controlling transmission of a carrier wave to a time slot allocated to the VSAT station 3i in band 4, reference numeral 91 denotes a reception buffer, reference numeral 92 denotes a transmission buffer, and reference numeral 93 denotes a header analysis unit. . Reference numerals 94 and 95 denote interface units. The interface unit 94 is connected to the processing device 13i via the signal line 15i, and the interface unit 95 is connected to the signal line 19i.
Is connected to the broadcast control device 11i.

In order to explain the operation of the line control device 9i, FIG. 8 shows the flow of processing of the header analysis unit 93. In FIG. 8, the header analysis unit 93 determines whether or not there is a transmission frame (the reception frames of Nos. 1, 3, 4, 5, and 8) in the reception buffer 91 in step 93a. If there is no transmission frame in the reception buffer 91, the step 93a is repeated. If there is a transmission frame in the reception buffer 91, one frame is extracted from the reception buffer 91 in step 93b. Next, it is determined whether or not the field A of the transmission frame extracted in step 93c is "0". If the field A is "0", the flow proceeds to step 93i. If the field A is not "0", it is determined in a step 93d whether the field A is the address i of the own station. If the field A is the address i of the own station, the process proceeds to step 93h. If the field A is not its own address i, it is determined in a step 93e whether or not the field SA is its own address i.

If the field SA is not the address i of the own station, the process proceeds to step 93g. If the field SA is the address i of the own station, it is determined in a step 93f whether or not the field R is "1". If the field R is "1",
Proceed to step 93h. If the field R is not "1", the process proceeds to step 93g, and after discarding the transmission frame, returns to step 93a. The transmission frame reaching step 93h is the transmission frame of No. 1, No. 3, or No. 4 in FIG. However, the No. 1 and No. 3 transmission frames are data addressed to the own station, and the No. 4 transmission frame is response data to the No. 3 data.

Next, if the field A is "0" in step 93c, that is, if the transmission frame is a transmission frame related to broadcasting, in step 93i, the transmission frame is transmitted to the signal line via the interface unit 95. Output to 19i and return to step 93a. The transmission frame up to this step 93i is the transmission frame No. 5 or No. 8 in FIG. This concludes the description of the processing of the header analysis unit 93 shown in FIG. 7, and the following describes transmission frames that do not pass through the header analysis unit.

The transmission frame that does not pass through the header analysis unit is shown in FIG.
No.2, No.3, No.4, No.6, No.7 and No.9. Of these, the transmission frames of No. 2, No. 3 and No. 4 are input from the signal line 15i to the line controller 9i through the interface unit 94 in FIG. It is. However, No. 3 is the data transmitted from the local station i, and No. 4
Is the response data to the No. 3 data. No.6, No.7
The No. 9 transmission frame is input from the signal line 19i to the line controller 9i via the interface unit 95, and is directly written into the transmission buffer 92.

FIG. 9 shows the configuration of the broadcast control device 10 of the Hub station 2. In FIG. 9, reference numeral 101 denotes an interface unit connected to the line control device 8 via the signal line 18, reference numerals 102, 103, and 106 denote buffers, 102 denotes a reception buffer, 103 denotes a transmission buffer, 106 denotes an interface unit, and 105 A reception buffer for input frames, 104 is a control unit, and 105 is the interface unit, which is connected to the processing device 12 via a signal line 16. Note that what is stored in the reception buffer 106 is H
The broadcast data transmitted from the ub station 2 and the like are stored in the reception buffer 102 in response to the broadcast data transmitted from the hub station 2 and the broadcast request data from the VSAT station 3i (No in FIG. 4). .7 transmission data) or response data to it.

In order to explain the operation of the broadcast control device 10, a processing flow of the control unit 104 is shown in FIG. In FIG. 10, the control unit 104 determines whether or not there is a transmission frame in the reception buffer 106 in step 40a. Receive buffer 106
If there is no transmission frame, the process proceeds to step 40d. If there is a transmission frame in the reception buffer 106, step 4
At 0b, one frame is extracted from the reception buffer 106. Next, a response management table (details will be described later) for the transmission frame extracted in step 40c is created. This processing, that is, the transmission frame up to step 40c is limited to the broadcast data transmitted from the own station and the Hub station 2, that is, No. 5 in FIG. In addition,
When the above-mentioned No. 5 transmission frame is written into the reception buffer 106, it is also written into the transmission buffer 103 by the interface unit 105 at the same time.

Subsequently, in step 40d, it is determined whether or not there is a transmission frame in the reception buffer 102. If there is no transmission frame in the reception buffer 102, the process returns to step 40a. If there is a transmission frame in the reception buffer 102, one frame is extracted from the reception buffer 102 in step 40e. Then step 4
At 0f, it is determined whether or not the field R of the transmission frame is “0”. Step if the field R is "0"
Proceeding to 40g, create a response management table for the transmission frame.

Subsequently, in step 40h, the transmission frame is output to the signal line 16 via the interface unit 105, and “1” is set in the ￥ FF area of the response confirmation area of the transmission frame in the response management table described later. Return to step 40a. This process, that is, the transmission frame that reaches step 40h is limited to No. 7 in FIG. On the other hand, when it is determined in step 40f that the field R of the transmission frame is not "0", a response process (described in detail later) is performed in step 40i, and the process returns to step 40a. This processing, that is, the transmission frame that reaches step 40i is performed in accordance with No. 6 and No. 9 in FIG.
Limited to In the transmission frame related to the broadcast shown in FIG.
It is No. 8 that does not pass through the control unit 104, and the transmission frame of No. 8 is copied from the transmission frame of No. 7 by the line control device 8 and already passed to the transmission / reception device 6 as described above. .

Next, the response management table provided in the control unit 104 of the broadcast control device 10 and the response process in step 40i in FIG. 10 will be described with reference to FIG. The response management table includes a transmission frame storage area and a response confirmation area (a, b, ..., i,
j,..., n, $ FF) and a timer management area (T). There are m areas composed of these areas. Each time new broadcast data is generated, the control unit 104 searches for an empty area (an area where the transmission frame storage area is cleared) in the response management table, and stores the data in the transmission frame storage area on a frame basis. At the same time, the response confirmation areas a, b,..., I, j,..., N, and ￥ FF are cleared, and the timeout time is set in the timer management area T. Further, each time a response frame to the transmission frame is received, "1" is set in the response confirmation area corresponding to the value of the field SA of the response frame. When the timeout time set in the timer management area T has been reached, the status of the response confirmation areas a, b,..., I, j,..., N, 送 FF is checked. Resend. If retransmission is unnecessary, the transmission frame storage area in the area is cleared. At this time, if the transmission frame is broadcast data transmitted from the own station, that is, the Hub station 2, a transmission completion signal is output to the signal line 16 via the interface 105 and transmitted to the processing device 12 to be connected. The method of using the m areas follows a general method of using a cyclic buffer or the like.

The timeout is controlled by the following method. A time-out control program that operates with a timer interrupt at a fixed period is provided in the control unit 104. If the value of the timer management area T is positive in the program, the time is set to a time corresponding to the timer interrupt period from the value. Subtract. The program repeats the above processing for the m timer management areas T. Therefore, if the value of the timer management area T is 0 or less, it can be determined that the time-out period has been reached.

Further, the determination of the necessity of retransmission is performed by the following method.

(1) The method proposed by the applicant in Japanese Patent Application No. 62-114276, "broadcast communication system". (2) Of the response confirmation areas a, b,..., I, j,. , 1
If there is an area that is at least "0", a method of retransmitting the corresponding data is omitted. If the response processing for the broadcast station of the broadcast data is omitted, that is, "1" May not be set, and accordingly, in the determination as to whether retransmission is necessary, it is necessary to exclude the processing related to the transmitting station. However, in the present embodiment, the processing is simpler without such exception processing. Therefore, the same processing is performed for the broadcasting data transmitting station. Also, confirming the response regarding the broadcasting station of the broadcast data requires that the transmitting station
This is equivalent to confirming the output of the transmission completion signal sent to the processing device to be connected, and improves the reliability of the system.

FIG. 12 shows a configuration of the broadcast control device 11i of the VSAT station 3i. In the figure, 111 is an interface unit connected to the line controller 9i via a signal line 19i, 112, 113 and 116 are buffers, 112 is a reception buffer, 113 is a transmission buffer, and 116 is input from the interface unit 115. A receiving buffer 114 for the transmission frame, a control unit 114, and the interface unit 115 are connected to the processing device 13i via a signal line 17i. The reception buffer 116 stores the broadcast data transmitted from the own station and the VSAT station 3i, and the reception buffer 112 stores the broadcast data from the hub station 2 and the own station. Broadcast data (data corresponding to the No. 8 transmission frame in FIG. 4) from the included VSAT station 3i (i = a, b,..., N) or response data thereto.

In order to explain the operation of the broadcast control device 11i,
FIG. 13 shows the flow of processing of the control unit 114. In FIG. 13, the control unit 114 determines whether or not there is a transmission frame in the reception buffer 116 in step 50a. Receive buffer 116
If there is no transmission frame, the process proceeds to step 50d. If there is a transmission frame in the reception buffer 116, one frame is extracted from the reception buffer 116 in step 50b. Next, in step 50c, the flag corresponding to the transmission frame in the flag area built in the control unit 114 is turned on. This processing, that is, the transmission frame to step 50c is limited to the broadcast data transmitted from the own station and the VSAT station 3i, No. 7 in FIG. Note that the transmission frame No. 7 described above is
When the data is written to 116, the data is also written to the reception buffer 113 by the interface unit 115 at the same time.

Subsequently, in step 50d, it is determined whether or not there is a transmission frame in the reception buffer 112. If there is no transmission frame in the reception buffer 112, the process returns to step 50a. If there is a transmission frame in the reception buffer 112, 1 is set in step 50e.
The frame is taken out, and the field SA of the transmission frame is set to “￥
FF "is determined. If the field SA is" @FF ", the process proceeds to step 50j. The field SA is" @FF "
If not, the flow advances to step 50f to determine whether or not the field SA is the address of another station. If the field SA is the address of another station, the process proceeds to step 50j. If the field SA is not the address of the other station, that is, the address of the own station, the process proceeds to step 50g, and the flag corresponding to the transmission frame in the flag area built in the control unit 114 is turned off.

Next, in step 50h, a transmission completion signal is output to the signal line 17i via the interface unit 115, and the process proceeds to step 50i. This processing, that is, the transmission frame that reaches step 50h is limited to No. 8 transmitted from the own station in FIG. By inputting the transmission completion signal through the signal line 17i,
The processing device 13i completes the control sequence. Step 50i
Then, a response frame is created and written into the buffer 113.
The address of the own station is set in the field SA of the response frame. The response frame written in the buffer 113 is No. 6 or No. 9 in FIG. On the other hand, in step 50j branched from steps 50e and 50f, the received frame is output to the signal line 17i via the interface unit 115, and the process proceeds to step 50i. This processing, that is, the transmission frame reaching step 50j is limited to No. 5 in FIG. 4 and No. 8 transmitted from another station.

According to the above embodiment, the transmission of broadcast data from the VSAT station is looped back from in-band to out-band by the line control device of the Hub station, so that the delay time accompanying the processing of the Hub station is small, and Since the VSAT station does not need to perform a response process accompanying the broadcast of its own data, there is an advantage that the configuration is simplified. In addition, the Hub station acknowledges the completion of the broadcast
There is no need to notify the VSAT station that transmitted the broadcast data, and this has the effect of facilitating the processing.

Incidentally, as a method for solving the above-mentioned problem, there is a method proposed by the present applicant in Japanese Patent Application No. 62-114276, "Broadcast Communication System".

This method is used in a broadcast communication system including a master station transmitting broadcast information and a plurality of slave stations receiving the broadcast information. A writing means capable of selecting a common (global) address and a group address for grouping the slave stations is provided so as to perform simultaneous broadcast of all slave stations and broadcast to a group. Out of the response frames from the slave stations, the number of frames including information indicating that the slave station has abnormally received the broadcast information frame having the same transmission order number from the master station is equal to or greater than a predetermined value. A detecting means for retransmitting the broadcast information frame in group units when an output of the detecting means is provided.

With respect to the above method, a slave station group having a high frequency of abnormal reception is separated from a plurality of slave station groups, and after a series of broadcast data transmission sequences is completed, retransmission of broadcast data to the separated slave station group is performed. The retransmission timing is desirably controlled as follows.

That is, in a broadcast communication system having a master station transmitting broadcast data and a slave station group including one or more slave stations receiving the broadcast data, the broadcast control device of the master station is Means for separating a slave station group having a poor response from a target among the slave station groups, and applying the separated slave station group to an application (an information processing device such as a computer or a terminal connected to the broadcast control device or operated by the device). And a means for notifying the application of the master station, and a means for storing the slave station group from which the master station application has been disconnected. Report data to each slave station group, monitor the response failure of each slave station group by the response frame from each slave station, and The slave station group disconnected from the subject of the broadcast control. Then, when there is a group in which the poor response has been recovered among the slave station groups that have been disconnected in the middle when a series of broadcast data transmission sequences is completed,
The broadcast control device of the master station retransmits the broadcast data for all disconnected slave station groups.

The broadcast control device of the master station repeats the above processing until there is no detached slave station group or until the response failure of the detached slave station group does not recover, and at the end, the information about the detached slave station group, Pass it to the master station application. The application of the master station knows the slave station group having a poor response from the received information about the detached slave station, and determines broadcast data to be subsequently broadcast (including retransmission) according to the situation. In this way, by monitoring the retransmission timing of broadcast data between the application of the master station and the broadcast control device, the retransmission timing can be captured more accurately.

 Hereinafter, a specific example will be described.

FIG. 14 is a diagram showing the configuration of the broadcast communication system, wherein 1 is a satellite, 20 is a master station, and 30 is a plurality of slave stations. Further, 4 (i) (i = 1, 2,... N) indicates a group composed of slave stations.

Here, a case where broadcast data is transmitted from the master station 20 to each slave station 30 will be considered. The master station 20 divides the broadcast data into broadcast frames of a certain size, adds one or more groups to receive the broadcast data, and adds a group address to each of the slave stations. (The solid line in FIG. 14). On the other hand, the slave station 30 that has received the broadcast frame determines whether or not it is addressed to the group to which it belongs, based on the group address added to the broadcast frame. If it is addressed to the group to which the own station belongs, a response frame is returned to the master station 20 (broken line in FIG. 14). Based on the response frame from each slave station, the master station 20 grasps the reception status of the broadcast frame of each group.

 Next, the operation of the master station 20 will be described.

FIG. 15 is a block diagram of the master station 20, which comprises a transmitting / receiving device 21, a broadcast control device 22, and an application 23. The broadcast data is passed from the application 23 to the broadcast control device 22 together with the broadcast target group address. The broadcast control device 22 creates a broadcast frame from the broadcast data received from the application 23, and broadcasts the broadcast frame to each slave station via the transmission / reception device 21. The response frame from each slave station is passed to the broadcast control device 22 via the transmission / reception device 21.

FIG. 16 shows the configuration of the broadcast control device 22. The configuration is the same as that of the broadcast control devices 10 and 11i.

The operation of the broadcast control device 22 will be described with reference to FIG. In step 60a, the broadcast data and the broadcast target group address are received from the application 23. Steps
In 60b, received broadcast data is stored in a fixed size 1
It is divided into one or more broadcast frames, and a transmission order number is attached to each broadcast frame. Then, in step 60c, initialization is performed so that transmission starts from the broadcast frame having the transmission order number at the head. At step 60d, a broadcast information frame to be transmitted (including retransmission) is transmitted with the broadcast target group address added. At step 60e, a timer is set in correspondence with the transmitted broadcast frame.

In step 60f, it is determined whether or not a response frame has been received from the slave station, and if it has been received, the response frame is analyzed in step 60g. The total of received and unreceived is taken. As a result of the accumulation, the timer of the broadcast frame whose reception status has reached the set reference is reset. In step 60h,
Broadcast data transmission sequence, that is, step 60b
It is determined whether or not the transmission sequence of a series of broadcast frames divided by the above is completed. If a response frame has not been received in step 60f, or if the broadcast data transmission sequence has not been completed in step 60h, the process proceeds to step 60p, and it is determined whether the timer set in step 60e has timed out. Find out what. If no time-out has occurred, the process returns to step 60d to transmit the next broadcast frame. If a timeout has occurred, the process proceeds to step 60q, and it is checked whether or not the number of retransmissions of the broadcast frame corresponding to the timeout has reached a certain number. From the results, isolate the group with poor response,
Return to step 60d.

Here, the term “disconnect” means that a group of slave stations is excluded from broadcast communication, and control based on a response from a slave station belonging to the group is not performed. However, in order to detect the recovery of the poor response of the separated group, the cumulative processing of the response frames is continued even in the separated group.

When the broadcast data transmission sequence is completed, it is determined in step 60i whether or not there is a group disconnected in the middle of the sequence, and if not, the normal termination information is passed to the application in step 60m and the processing is terminated. . If there is a separated group, it is determined whether or not any of the groups separated in step 60j has recovered from the poor response. If there is at least one group, all the separated groups are determined in step 60k. The process returns to step 60c for the broadcast target, and retransmits the broadcast data. One of the separated groups has recovered from the poor response (as described above, since the cumulative processing of the response frames is continued even in the separated group, recovery of the poor response is detected from the cumulative result).
If not, in step 60n, the group address of the separated group is passed to the application, and the process ends.

Before describing the operation of the application 23, a table held by the application 23 will be described. FIG. 18 shows the structure of the table. The application 23 has _ns pieces of broadcast data (i = 1, 2,..., _Ns ) to be broadcasted, and stores _ng groups j (j = 1, 2,..., _Ng ). It is a slave station group to be broadcast. In the figure, r _ij represents the reception status of the group j with respect to the broadcast data i, and has three states of “not received”, “received”, and “not received”. here,
"Not receiving" indicates a group that does not need to transmit the broadcast message. S _j represents the communication state of group j at time t _{j, and} has two states of “communicable” and “communicable”.

Next, the operation of the application 23 will be described with reference to FIG. In step 70a, the table is initialized as follows. According to the broadcast data and the corresponding slave station group to be broadcast, the reception status _rij is “not received”.
Or, set “not to be received”, and for all n _s broadcast data i, set “communication disabled” to the communication state s _j for the group j that is “not to be received”, and "Communication enabled" is set, and the current time is set in _tj . In step 70b, the broadcast data i having the maximum number of groups whose communication status s _j is “communicable” is set to 1
Search for one. In step 70c, the broadcast data i found in step 70b and the group addresses of all the groups j whose reception status r _ij is “not received” for the broadcast data i are
It is passed to the broadcast control device 22.

In step 70d, the broadcast end information is received from the broadcast control device 22 (the application 23 waits in step 70d until the broadcast control device 22 is broadcasting, that is, until the broadcast end information is passed to the application). Status). In the case of normal termination (step 60 cm in FIG. 17)
), “Received” is set to the reception status r _ij for all the groups j corresponding to the broadcast data i and the group address passed in step 70c, and the communication status s
_{j is set} to “communicable” and t _j is set to the current time. If the broadcast end information received in step 70d is the separation group address described in the description of FIG. 17, the reception status r _ij regarding the broadcast data i passed in step 70c and the group j corresponding to the group address is Among the communication states s _j , the reception state r _ij of the communication state s _j corresponding to the separated group address is “not received”, the communication state s _j is “communication impossible”, and the others are received. The status r _{ij is set} to “received”, the communication status s _j is set to “communicable”, and the current time is set to t _j .

Then, in step 70e, all broadcast messages
i, checking the reception status r _ij for all groups j,
It is determined whether or not there is an “unreceived” item. If there is no “unreceived” item, the process is terminated. If at least one item is “unreceived”, the process proceeds to step 70f. In step 70f, for a certain broadcast data i, for the group j in which the reception status r _ij is “not received” and the difference between the current time and t _j is equal to or longer than a certain time, the communication state s _{j is set} to “ "Communication possible" is set to the current time in _tj , so that broadcast transmission to the group can be performed in order to obtain the latest communication state for the group.

In step 70g, for a certain broadcast data i, the communication status s of the group j whose reception status r _ij is “not received”
It is determined whether or not _j is all “communication impossible”. If all _j is “communication impossible”, the process proceeds to step 70h; otherwise, the process returns to step 70b to continue the process. In step 70h, since all of the "non-received" broadcast target groups are "communication disabled", it is determined whether to end abnormally or proceed to step 70i to retry. The criterion for this retry is determined based on the value, significance, and the like of the broadcast data. In step 70i, after a certain period of time such that the communication failure is recovered, for a certain broadcast data i, for all the groups j whose reception status r _ij is “not received”, the communication status s _{j is changed} to “communication enabled”. Is set to the current time in t _j and the process returns to step 70b to retry.

As described above, the broadcast control unit 22 recovers the group of the slave stations disconnected from the broadcast target because the broadcast data cannot be received due to the temporary deterioration of the line quality. By monitoring the broadcast data in the application 23, the retransmission timing of the broadcast data can be accurately grasped, which has the effect of reducing unnecessary retransmission of the broadcast data.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the broadcast control in a radio | wireless communications system can be simplified, the increase in the system cost accompanying a broadcast service can be avoided, and the throughput at the time of a broadcast communication can be ensured.

[Brief description of the drawings]

FIG. 1 shows a VS implementing a broadcast service based on the present invention.
FIG. 2 is a diagram illustrating a schematic configuration of an AT system, FIG. 2 is a diagram illustrating an outline of a VSAT system, FIG. 3 is a diagram illustrating a transmission frame format used in the present system, and FIG. Explanatory diagram, fifth
The figure shows the configuration of the line control device of the Hub station, and FIG.
FIG. 7 is a diagram showing a flow of processing of a header analysis unit of a line control device of a station, FIG. 7 is a diagram showing a configuration of a line control device of a VSAT station, and FIG. 8 is a diagram showing a flow of processing of a line control device of a VSAT station. FIG. 9 is a diagram showing the configuration of a broadcast control device of a Hub station, FIG.
The figure shows the processing flow of the broadcast control device of the Hub station,
FIG. 11 is a configuration diagram of a response management table provided in the control unit of the broadcast control device of the Hub station, FIG. 12 is a diagram showing a configuration of the broadcast control device of the VSAT station, and FIG. FIG. 14 is a diagram showing a process flow of a broadcast control device, FIG. 14 is a diagram showing a configuration of a broadcast communication system, FIG. 15 is a diagram showing a configuration of a master station, and FIG. 16 is a broadcast control device of a master station. FIG. 17 is a diagram showing the flow of processing of the broadcast control device of the master station, FIG. 18 is a diagram showing the structure of a table held by the application of the master station, and FIG. 19 is a diagram of the master station. FIG. 7 is a diagram illustrating a flow of processing of an application. 1: Satellite, 2: Hub station, 3i (i = a to n): VSAT station, 4: In band, 5: Out band, 6 and 7i: Transceiver, 8 and 9i: Line controller, 10 and 11i: Broadcast control devices, 12 and 13i: processing device, 20: master station, 30: slave station.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Morita 1479, Kamizuhoncho, Kodaira-shi, Tokyo Inside Hitachi Microcomputer Engineering Co., Ltd. (72) Inventor Hiroyuki Wada 4-6 Kitahama, Higashi-ku, Osaka-shi, Osaka Sun Rishiseibu Software Co., Ltd. (72) Inventor Yasuo Matsui 4-6-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. (56) References JP-A-61-84140 (JP, A) JP-A-63-278440 (JP, A) IEEE COMMUNICATION NS MAGAZINE, MAY 1988, Vol. 26, No. 5P. 10-24

Claims (1)

(57) [Claims] 1. A broadcast control method in a wireless communication system for performing bidirectional communication of information between slave stations in units of frames via a master station by radio, comprising the steps of: The slave station sets destination information indicating that the information frame is the object of the broadcast in the address field of the header of the information frame to be broadcast, and sets the information frame in the header to the master station. Data type information indicating whether the data is for transmission request data or response data to the master station and station identification information unique to the own station are added and transmitted, and the master station receives information from the slave station. When the header of the frame is analyzed and the information frame to be broadcasted is recognized based on the destination information and the data type information, the information frame to be broadcasted is transmitted in the same format including the header. The slave station requesting the broadcast analyzes the header of the received information frame from the master station, and transmits the received information frame from its own station based on the destination information and the station identification information. And determining whether the master station has completed transmission of the broadcast information frame transmitted from the own station by determining that the information frame is a broadcast target information frame. Communication control method.