JPH1146161A - Method for transferring radio multicast data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reliability from being lowered, also to reduce time that is needed for response and to prevent data transfer efficiency from falling by a sending station performing polling to one in a receiving station group and requesting response after sending the final frame of broadcast data to the group. SOLUTION: A sending station 101 sends a series of multicast data and when it finishes sending them, it performs polling 341 to a receiving station 201 that is a representative station of a group 211. On the other hand, when the station 201 receives whole frames without errors, it returns an acknowledge(ACK) 311. A receiving station 202 which is a member of the group 211 monitors a polling signal to the station 201 and its response and returns a negative acknowledge(NAK) 321 following the ACK 311 if response that is returned by the station 201 does not notify the state of its own station, i.e., an error of a 2nd frame to the station 101. When the station 101 receives the NAK 321, it quickly resends a frame 331 that is requested.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a data transfer method in wireless multicast communication. In particular, the present invention, when performing broadcast data transfer by wireless multicast communication, the transmitting station fragments the broadcast data as needed, attached to an address and a transmission sequence number and framed,
Wireless multicast communication in which data is transferred to multiple receiving stations in one frame transmission, and the receiving station returns broadcast frames and then returns a response frame to the transmitting station, so that the transmitting station retransmits frames as necessary. About.

[0002]

2. Description of the Related Art In conventional multicast communication,
As means for transferring the same data to a plurality of specific receiving stations collectively, Internet Engi
Nearing Task Force and the like have been studied. Internet Protocol (hereinafter referred to as IP)
In IP multicast using, a best-effort service is assumed, and retransmission of an erroneous packet during data transfer is not considered (“Host Ext”).
enhancement for IP Multicast ",
IETF RFC 1112, 1989).

In a multicast communication system in which retransmission of erroneous data is taken into consideration, when a receiving station detects an error in a received packet or data frame, a negative acknowledgment () indicating an erroneous frame number is sent to the transmitting station as a response. Nega
active Acknowledgement: NA
K), a retransmission request is made.
The transmitting station performs retransmission when retransmission is requested by NAK.

FIG. 1 is a diagram showing an example of a conventional multicast data transfer.
The state of performing data transfer to multicasts 1 to 205 by multicast is shown over time. In the figure, a white rectangle is a data frame, and internal numbers are sequence numbers assigned to the frames. Downward arrows indicate the passage of time, and diagonal arrows indicate how frames are transmitted. In the figure, the multicast data is divided into four frames and sent to the receiving station.

[0005] After transmitting a series of multicast data frames, the transmitting station 101 waits for a response from the receiving station. In the figure, the transmitting station 101 transmits the first to fourth frames. When the receiving station detects an error in the received multicast data frame, the receiving station sets the erroneous frame number to N.
It returns to the transmitting station with an AK frame and requests retransmission. The figure shows that the receiving station 201 is in the second frame and the receiving station 2
05 is an example when an error is detected in the third frame. The receiving station 201 requests retransmission of the second frame N
AK 321 and the receiving station 205 sends a NAK 322 requesting retransmission of the third frame to the transmitting station 101, respectively.
Return to In the transmitting station 101, NAK321 and NAK3
22 and retransmits the second and third data frames requested by NAK321 and NAK322.
In the figure, the retransmissions of the second and third data frames are shown as retransmission frames 331 and 332, respectively.

[0006] After the retransmission is completed, the transmitting station 101 regards that the data transfer has been successful unless it is requested to retransmit another frame. At this point, if there is subsequent multicast data, the transmitting station 101 can transfer the next multicast data. After transmitting the series of multicast data, the transmitting station 101 performs the transfer according to the same procedure as described above as necessary. FIG. 3 shows a case where the transmitting station 101 transmits the fifth to eighth multicast data frames, and when the transmitting station 101 transmits a series of multicast data, the receiving station 203 makes an error in the seventh frame. Receiving station 20
3 returns a NAK 323 requesting retransmission of the 7th frame, but because the NAK 323 is incorrect on the transmission line, the transmitting station 1
Here is an example that did not reach 01. In this case, the transmitting station 101
Cannot recognize the need for retransmission. Therefore, the transmitting station 101
Deems that the transfer of the multicast data by the 5th to 8th frames has been successful.

[0007] Since the transmitting station 101 terminates the transmission if there is no subsequent data, the multicast data transfer to the receiving station 203 fails in this case.

FIG. 2 is a diagram showing another example of the conventional multicast data transfer.
The state of performing data transfer by multicast to 01 to 205 is shown over time. In the figure, a white rectangle is a data frame, and internal numbers are sequence numbers assigned to the frames. A black rectangle represents NAK, and a hatched rectangle represents an acknowledgment (Acknowledgmen).
t: ACK). Downward arrows indicate the passage of time, and diagonal arrows indicate how frames are transmitted. In the figure, the multicast data is divided into four frames and sent to the receiving station.

After transmitting a series of multicast data frames, transmitting station 101 waits for a response from the receiving station. In the figure, the transmitting station 101 transmits the first to fourth frames. The receiving station returns an ACK to the transmitting station 101 when all the transmitted multicast data frames are received without error. In the figure, the receiving station 202 and the receiving station 203 perform this operation by returning ACK 311 and ACK 312, respectively. When the receiving station detects an error in the received multicast data frame, the receiving station returns an erroneous frame number to the transmitting station in a NAK frame and requests retransmission. The figure shows an example in which the second frame is incorrect in the receiving station 201 and the third frame is incorrect in the receiving station 205. At this time, the receiving station 201 has the NAK 321 and the receiving station 205 has the NA
Returning K322 requests retransmission of the second and third frames, respectively.

[0010] When receiving the NAK, the transmitting station 101 retransmits the frame of the number requested by the NAK. In the figure, the transmitting station 101 retransmits the second and third frames requested by NAK321 and NAK322. The receiving station that has requested retransmission returns an ACK to the transmitting station 101 when the frame requested by itself has been correctly received. In the figure, the receiving station 201 and the receiving station 205
313 and ACK 314, and the transmitting station 10
1 has been notified. The transmitting station sends ACKs from all receiving stations.
Is considered complete when is returned. In the figure, when receiving the ACK 314, the transmitting station 101 regards that the transmission of the multicast data 301 has been completed.

After the transmission of the multicast data is completed, the transmitting station 101 can transfer the subsequent multicast data. In the figure, after the transfer of the multicast data 301 is completed, the transfer of the multicast data 302 is performed. The multicast data 302 is transferred in the fifth to eighth frames.
The case where the number frame is incorrect is shown. Also in this case, retransmission is performed according to the procedure described above.

In FIG. 1, AC from the receiving station 205
An example is shown at the same time in a case where K317 did not reach the transmitting station 101 due to an error. In this case, the transmitting station 101 cannot recognize the receiving status of the receiving station 205. Therefore, the transmitting station 101 polls the receiving station 205 in response to the timeout of the timer started at the end of the transmission of the multicast data 302 in order to know the receiving status of the receiving station 205. The receiving station 205 notifies the transmitting station 101 of its own state by responding to the polling signal 341 from the transmitting station 101. After receiving the ACK 319, it is assumed that the transmission station 101 has completed retransmission of the multicast data 302.

[0013]

Conventionally, multicast data transfer has been performed by the method described above. In the conventional multicast data transfer method shown in FIG. 1, the transmitting station performs retransmission upon NAK. in this case,
When the NAK does not reach the transmitting station correctly due to a transmission error, or when NAKs transmitted from a plurality of stations collide on the transmission path, the transmitting station cannot recognize the necessity of retransmission, so the necessary retransmission is not performed. However, there has been a problem that the reliability of the multicast data transfer is reduced.

In addition, when the last fragmented frame is incorrect, there is no subsequent frame, so that dropout of the sequence number cannot be detected, and no retransmission request is made, so that necessary retransmission is not performed. In particular, there has been a problem that the reliability of multicast data transfer is reduced particularly in a transmission path where errors frequently occur, such as wireless communication.

When the receiving station returns a NAK, the NAK
The back-off algorithm was used to reduce the probability of frame collision, or an individual connection was established to return a response, but in this case, if the number of receiving stations increases, the time for delivery confirmation becomes enormous. As a result, there has been a problem that the transfer efficiency of the multicast data is reduced.

In the conventional multicast data transfer method shown in FIG. 2, reliability is ensured by using ACK and NAK together for delivery confirmation, but the transmitting station needs to receive responses from all receiving stations. There is. The receiving station is ACK,
When returning a NAK response, a back-off algorithm was used to reduce the probability of a response frame collision, or an individual connection was established to return a response. There was a problem that the time for confirmation was enormous.

Also, in the multicast data transfer method shown in FIG. 2, if the last fragmented frame is erroneous, the receiving station cannot detect the frame error. Therefore, the receiving station cannot respond,
In this case, recovery measures such as polling performed by the transmitting station when the timer times out have been taken. For this reason, there is a problem that the time for performing the delivery confirmation becomes long and the data transfer efficiency is deteriorated.

Accordingly, the present invention has been made to solve the above-mentioned problems in the conventional multicast data transfer, and has as its object to prevent a decrease in reliability even in a communication path of poor quality and increase the number of receiving stations. It is an object of the present invention to provide a multicast data transfer method that can reduce the time required for a response even in such a case and can prevent a decrease in data transfer efficiency.

[0019]

According to the present invention, there are provided a transmitting station for transmitting broadcast data by wireless multicast communication, and a plurality of receiving stations for receiving the broadcast data.
The transmitting station performs fragmentation of broadcast data as necessary, creates a frame with an address of a destination receiving station group and a transmission sequence number, performs data transfer to the plurality of receiving stations in one frame transmission, The receiving station returns an ACK when the broadcast data is correctly received, and when the receiving station detects an error in the frame, the receiving station returns the number of the frame in which the error was detected to the transmitting station by NAK. , The transmitting station, upon receiving the NAK,
In the wireless multicast communication for retransmitting the broadcast data of the number described in K, (1) the transmitting station groups receiving stations that can directly transmit and receive, and (2) the transmitting station An arbitrary receiving station is selected as a representative station from among them. (3) The transmitting station transmits to the receiving station group a broadcast frame in which an address and a sequence number are added to broadcast data, and after transmitting the final frame, (4) The transmitting station:
Polling one of the groups and requesting a response; (5) the representative station of the polled group is:
If the broadcast data has been received correctly, an ACK will be sent.
If the broadcast data cannot be received correctly, the NAK is returned to the transmitting station together with the wrong frame number as a response. (6) The representative station returns any station other than the representative station in the polled group. Monitor the result, if the response returned by the representative station is ACK or if the response of the representative station could not be monitored, and if there was a broadcast data frame that could not be received correctly, Within a certain period of time T1, a number of a frame requested to be retransmitted to the NAK is added back to the transmitting station, and (7) the transmitting station
When the retransmission is requested by the NAK, the polling is interrupted, the frame having the requested number is immediately retransmitted by multicast, and after the retransmission is completed, the polling is performed again to the representative station of the group which has stopped the polling first. If NAK is not returned within a predetermined time T1 after receiving ACK, poll the next group and (8)
The transmitting station repeats (4) to (7), finishes polling for all groups, and completes multicast data transfer when receiving an ACK from the representative station of the last group. Is provided.

Further, according to the present invention, the broadcast station comprises a transmitting station for transmitting broadcast data by wireless multicast communication and a plurality of receiving stations for receiving the broadcast data. Perform fragmentation, create a frame with the address of the destination receiving station group and the transmission sequence number, transfer data to the plurality of receiving stations in one frame transmission, and the receiving station correctly received the broadcast data When the receiving station detects an error in the frame, the receiving station returns the number of the frame in which the error is detected to the transmitting station by NAK, and when the transmitting station receives the NAK, In the wireless multicast communication for retransmitting the broadcast data of the number described in the NAK, (1) the transmitting station groups receiving stations that can directly transmit and receive. (2) the transmitting station selects, as a representative station, a receiving station in which a transmission error is most likely to occur from each of the groups as a representative station; and (3) the transmitting station transmits broadcast data to the receiving station group. (4) the transmitting station polls one of the groups and requests a response, and (5) the polled group. The representative station returns an ACK to the transmitting station as a response together with an erroneous frame number when receiving the broadcast data correctly, or an NAK when the broadcast data cannot be received correctly, (6) Stations other than the representative station in the polled group monitor the result returned by the representative station, and if the response returned by the representative station is ACK or the response of the representative station cannot be monitored. And if there is a frame of the broadcast data that could not be received correctly, return to the transmitting station with the number of the frame requesting retransmission to NAK within a certain time T1, and When a retransmission is requested by the NAK, the transmitting station interrupts the polling, immediately retransmits the frame having the requested number by multicast, and after the retransmission is completed, performs polling again to the representative station of the group in which the polling was interrupted first. , After receiving an ACK from the representative station,
If AK is not returned, poll the next group. (8) The transmitting station repeats (4) to (7), finishes polling for all groups, and returns from the representative station of the last group. A wireless multicast data transfer method is provided, wherein the multicast data transfer is completed when an ACK is received.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a diagram showing a first embodiment of the present invention, and shows a state in which multicast data transfer is performed from the transmitting station 101 to the receiving stations 201 to 205 over time. In the figure, a white rectangle is a data frame, and internal numbers are sequence numbers assigned to the frames. Downward arrows indicate the passage of time, and diagonal arrows indicate how frames are transmitted. In the figure, the multicast data 301 and 302 are each divided into four frames and sent to the receiving station.

The receiving stations are grouped, and the receiving stations 2
01 and the receiving station 202 belong to the group 211, and the receiving station 203 and the receiving station 204 belong to the group 212. This situation is clearly shown in FIG. 6 illustrating the grouping of the receiving station groups in the present embodiment.

Prior to multicast data transmission, the transmitting station 101 randomly selects a representative station from each group. As shown in FIG.
1 assumes that the receiving station 203 is the representative station in the group 212. It is assumed that the receiving station 205 exists alone. That is, the receiving station 205 is assumed to form one group 213 by one station.

FIG. 4 shows an operation flowchart of the transmitting station 101 in the present embodiment, and FIG. 5 shows an operation flowchart of each of the receiving stations 201 to 205 in the present embodiment. Hereinafter, the wireless multicast data transfer operation in the present embodiment will be described with reference to FIGS.

The transmitting station 101 transmits a series of multicast data (S1 in FIG. 4). In FIG.
The number frame has been transmitted. After finishing transmitting the multicast data, the transmitting station 101 polls the representative station of each group (S2 in FIG. 4). First, polling is performed on the receiving station 201, which is the representative station of the group 211. The polling signal is denoted by reference numeral 341 in FIG.

On the other hand, upon receiving the multicast data (S10 in FIG. 5), the receiving station determines whether or not the own station is a representative station (S11 in FIG. 5). When the polling signal is received in the case of the representative station (S12 in FIG. 5), a response is transmitted (S13 in FIG. 5). In FIG. 3, the receiving station 201 returns ACK 311 because all the frames have been received without error (S14 in FIG. 5).

Receiving station 2 which is a member of group 211
02 receives the multicast data (S in FIG. 5).
10), it is determined whether or not the own station is a representative station (S1 in FIG. 5).
1). If the own station is not the representative station, it is determined whether there is an error in the received data (S15 in FIG. 5). If there is an error, the polling signal to the representative station 201 and its response are monitored (S16 in FIG. 5), and the response returned by the representative station 201 transmits the status of the own station, that is, the error of the second frame. If not to notify the station 101 (S17 in FIG. 5), A
NAK321 is returned following CK311 (S1 in FIG. 5).
8).

When receiving the NAK 321 (S3 in FIG. 4), the transmitting station 101 promptly sends the requested frame 331.
Is retransmitted (S5 in FIG. 4). Retransmission is performed by multicast, and all receiving stations within the area 111 covered by the transmitting station can receive the retransmission frame 331. However, a station that has already correctly received the second frame discards the second frame received during retransmission.

After the retransmission is completed, the transmitting station 101
The polling is performed again for the representative station 201 (see FIG. 4).
S2). Polling 342 in the figure corresponds to this.
The representative station 201 of the group 211 returns the ACK 312 (S12 to S14 in FIG. 5). When the receiving station 202 has successfully received the retransmitted frame 331, it has not received any data, and does nothing.

After receiving the ACK 312 from the representative station 201 of the group 211, the transmitting station 101 sets a time interval T1.
If the NAK is not received within this time (S4 in FIG. 4), polling is performed to the representative station of the next group. Therefore, in this case, the transmitting station 101 performs polling 343 to the receiving station 203, which is the representative station of the group 212.

According to the above procedure, the transmitting station 101 performs polling up to the group 213 which is the last group, and when the ACK 314 is received from the last group, the transmission of the multicast data 301 is regarded as completed (see FIG. 4). S6).

Next, the transmitting station 101 transmits the next multicast data 302 in the same manner.

FIG. 7 is a diagram for explaining the second embodiment of the present invention, and shows a state in which data transmission from the transmitting station 101 to the receiving stations 201 to 205 is carried out by multicast with the passage of time. In the figure, a white rectangle is a data frame, and internal numbers are sequence numbers assigned to the frames. Downward arrows indicate the passage of time, and diagonal arrows indicate how frames are transmitted. In the figure, the multicast data 301 and 302 are each divided into four frames and sent to the receiving station.

The receiving stations are grouped, and the receiving stations 2
01 and the receiving station 202 belong to the group 211, and the receiving station 203 and the receiving station 204 belong to the group 212. This situation is clearly shown in FIG. 8 illustrating the grouping of the receiving station groups in the present embodiment.

The transmitting station 101 uses the communication history information of each receiving station and the like, and prior to multicast data transmission of the receiving station, generates the most transmission error from each group based on past communication history or network topology management information. Select an easy-to-use station as the representative station. In the figure, it is assumed that the receiving station 202 is the representative station in the group 211 and the receiving station 203 is the representative station in the group 212. Also, the receiving station 205
Are present independently, and the receiving station 205 forms one group 213 by one station.

The transmitting station 101 transmits a series of multicast data 301. In FIG. 7, the first to fourth frames are transmitted. After finishing transmitting the multicast data, the transmitting station 101 polls the representative stations of each group. First, polling is performed on the receiving station 202, which is the representative station of the group 211.

The polled receiving station 202 returns NAK 321 because it detected an error in the second frame. The receiving station 201 which is a member of the group 211 monitors polling and its response. At this time, the receiving station 201 has correctly received all the frames of the multicast data 301, and does not return a response because the own station is not the representative station of the group.

When receiving the NAK, the transmitting station 101 promptly retransmits the requested frame. This retransmission is performed by multicast, and all receiving stations within the area covered by the transmitting station can receive the retransmitted frame 331. However, a station that has already correctly received the second frame discards the second frame received during retransmission.

After finishing the retransmission, the transmitting station 101 sets the group 2
Polling is again performed on the 11 representative stations (polling 2 in the figure corresponds to this). The receiving station 202 returns ACK 311 this time because the retransmitted frame 331 has been correctly received.

After receiving the ACK 311 from the representative station of the group 101, if the transmitting station does not receive the NAK from another receiving station within the time interval T1, the transmitting station polls the representative station of the next group. Therefore, the transmitting station 101 polls the receiving station 203 which is the representative station of the group 212 in FIG.

In the above procedure, the transmitting station performs polling up to the group 213 which is the last group, and when the ACK is received from the last group, it is considered that the transmission of the multicast data 301 has been completed.

When the transmitting station receives the ACK from the last group, it can start transmitting the next multicast data. In the figure, the multicast data 302 is 5
It is transferred in the 8th to 8th frames. After the transmission of the multicast data 302 is completed, the transmitting station 101 confirms the delivery by the above method. Here, an example is shown in which the seventh frame is passed between the receiving station 203 and the receiving station 205.

The transmitting station 101 performs polling for each group. When polling the group 212, the transmitting station 101 receives a poll from the receiving station 203 which is a representative station of the group 212.
Retransmission of the seventh frame is requested. The transmitting station 101
After receiving NAK 322 as a retransmission request from receiving station 203, retransmission of the seventh frame is started immediately. This retransmission is indicated by 332 in the figure. At this time, since the retransmission frame 332 can be received by all the receiving stations within the area of the transmitting station 101, the receiving station 205 also receives the seventh frame 332.

After transmitting 332, transmitting station 101 again polls group 212. And ACK315
Is received, polling is performed on the receiving station 205, which is a representative of the group 213. The receiving station 205 returns the ACK 316 here because the erroneous frame has been recovered in the first transmission by the previous retransmission frame 332.

After receiving the ACK 316, the transmitting station 101
It is considered that the transmission of the multicast data 302 has been completed.

The embodiments described above all show the present invention by way of example and not by way of limitation, and the present invention can be carried out in various other modified and modified forms. Therefore, the scope of the present invention is defined only by the appended claims and their equivalents.

[0048]

As described above, according to the present invention, when performing a multicast data transfer, a transmitting station groups a group of receiving stations with stations that can transmit and receive each other, and selects a representative station from each group one by one. After transmitting a series of multicast data, the transmitting station polls each group, returns an ACK only to the representative station, and monitors other stations in the group for a response returned by the representative station. The NAK is returned to the transmitting station only when it is necessary to request retransmission, judging from the reception result, and the transmitting station retransmits only the requested frame when the NAK is returned, and restarts polling after retransmission is completed. If only the ACK is returned, poll the next group, and the transmitting station starts ACKing from the last group.
Since the multicast data transfer is completed at the time when is returned, the multicast data transfer with high efficiency is possible by shortening the time for the delivery confirmation while providing high reliability.

According to the present invention, when a frame requested to be retransmitted by one receiving station in a group is requested to be retransmitted by another receiving station in the group, the frame is first retransmitted. Since all stations that request retransmission of a frame can receive the frame, the probability of the frame being retransmitted within the group is reduced, so that efficient retransmission can be performed.

Further, according to the present invention, when performing a multicast data transfer, the transmitting station manages the communication quality of the transmission line with each receiving station and the topology of the network in advance so that the receiving station groups can be mutually exchanged. The transmitting and receiving stations are grouped together, and the receiving station where transmission errors are most likely to occur is selected from each group as a representative station one by one. After transmitting a series of multicast data, the transmitting station polls each group and performs ACK. Is returned only to the representative station, and other receiving stations in the group monitor the response returned by the representative station and return a NAK to the transmitting station only when it is necessary to request retransmission based on the reception result of the own station. The transmitting station retransmits only the requested frame when NAK is returned, restarts polling after retransmission is completed, and polls the next group when only ACK is returned. , The transmitting station AC from the last group
Since the multicast data transfer is completed at the time when K is returned, the multicast data transfer with high efficiency can be performed by shortening the time for the delivery confirmation while providing high reliability.

In the present invention, in addition to the effects of the above-described invention, the number of frames returned as a response is reduced by polling the station where transmission errors are most likely to occur at the time of confirming delivery, and the time required for retransmission is reduced. , It is possible to perform highly efficient multicast data transfer.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a conventional multicast data transfer.

FIG. 2 is a diagram illustrating another example of conventional multicast data transfer.

FIG. 3 is a diagram illustrating a first embodiment of the present invention.

FIG. 4 is a flowchart of the operation of the multicast data transmitting station according to the present invention.

FIG. 5 is a flowchart of the operation of the multicast data receiving station according to the present invention.

FIG. 6 is a diagram illustrating an example of grouping of receiving stations according to the present invention.

FIG. 7 is a diagram illustrating a second embodiment of the present invention.

FIG. 8 is a diagram illustrating another example of grouping of receiving stations according to the present invention.

[Explanation of symbols]

 101 transmitting station 111 area covered by transmitting station 201-205 receiving station 211-213 receiving station group 221-222 non-multicast receiving terminal 301-302 multicast data 311-319 ACK frame 321-323 NAK frame 331-333 retransmission frame 341- 347 Polling signal T1 NAK response wait time

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Morikura Nippon Telegraph and Telephone Corporation, 3-9-1-2 Nishishinjuku, Shinjuku-ku, Tokyo

Claims (4)

[Claims] 1. A wireless multicast data transfer method for performing broadcast data transfer from a transmitting station to a plurality of receiving stations by wireless multicast communication, wherein the transmitting station groups the receiving stations and includes An arbitrary receiving station is selected from among them as a representative station, and after transmitting the final frame of the broadcast data to the receiving station group, one of the groups is polled and a response is requested. The representative station of the polled group sends an acknowledgment to the transmitting station as a response if the broadcast data was received correctly and a negative acknowledgment together with the wrong frame number if the broadcast data was not received correctly. A station other than the representative station in the polled group monitors the result returned by the representative station, and if the response returned by the representative station is an acknowledgment or If the response of the representative station could not be monitored, and if there was a broadcast data frame that could not be received correctly, add a frame number requesting retransmission to the negative response within a certain time,
Returning to the transmitting station, when the transmitting station is requested to retransmit by a negative acknowledgment,
The polling is interrupted, the frame having the requested number is immediately retransmitted by multicast, and after the retransmission is completed, the representative station of the group that interrupted the polling is polled anew, and after receiving an acknowledgment from the representative station, the predetermined time period has elapsed. If a negative response is not returned within a time period, the next group is polled. 2. A broadcast station comprising: a transmitting station for transmitting broadcast data by wireless multicast communication; and a plurality of receiving stations for receiving the broadcast data. Create a frame to which the address of the receiving station group and the transmission sequence number are assigned, perform data transfer to the plurality of receiving stations in one frame transmission, and the receiving station issues an acknowledgment when the broadcast data is correctly received. In addition, when the receiving station detects an error in the frame, the receiving station returns the number of the frame in which the error is detected to the transmitting station by a negative response, and when the transmitting station receives the negative response, A wireless multicast communication for retransmitting broadcast data of a number described in a negative acknowledgment, wherein (1) a transmitting station groups receiving stations that can directly transmit and receive, The transmitting station selects an arbitrary receiving station from each group as a representative station one by one. (3) The transmitting station assigns an address and a sequence number to broadcast data to the receiving station group. Broadcast frame transmission,
After transmitting the last frame, (4) the transmitting station polls one of the groups and requests a response; and (5) the representative station of the polled group correctly receives the broadcast data. If so, an acknowledgment is returned. If the broadcast data cannot be received correctly, a negative acknowledgment is returned to the transmitting station together with an incorrect frame number as a response. (6) The representative in the polled group Stations other than the station monitor the result returned by the representative station, and when the response returned by the representative station is an affirmative response or when the response of the representative station cannot be monitored, and the frame of the broadcast data is correct. If there is something that could not be received, a certain time T
Within one, the negative acknowledgment is returned to the transmitting station with the number of the frame requesting retransmission, and (7) the transmitting station suspends polling when requested to retransmit by a negative response and is immediately requested. If the frame having the number is retransmitted by multicast, and after the retransmission is completed, polling is performed again to the representative station of the group that has stopped polling first, and after receiving an acknowledgment from the representative station, if a negative response is not returned within a certain time T1 (8) The transmitting station repeats (4) to (7), finishes polling all groups, and receives an acknowledgment from the representative station of the last group. Wireless multicast data transfer method, wherein multicast data transfer is completed. 3. A wireless multicast data transfer method for performing broadcast data transfer from a transmitting station to a plurality of receiving stations by wireless multicast communication, wherein the transmitting station groups the receiving stations and sets each of the groups. From among the receiving stations, the receiving station in which a transmission error is most likely to occur is selected one by one as a representative station, and after transmitting the last frame of broadcast data to the receiving station group, one of the groups is polled and a response is made. The representative station of the polled group responds with an acknowledgment if the broadcast data was correctly received, and a negative acknowledgment with the wrong frame number when the broadcast data was not correctly received. The stations other than the representative station in the polled group monitor the result returned by the representative station, and the response returned by the representative station is acknowledged. If the answer is negative or if the response of the representative station could not be monitored, and if some of the broadcast data frames could not be received correctly, a frame requesting retransmission for a negative response within a certain time With the number of
Returning to the transmitting station, when the transmitting station is requested to retransmit by a negative acknowledgment,
The polling is interrupted, the frame having the requested number is immediately retransmitted by multicast, and after the retransmission is completed, the representative station of the group that interrupted the polling is polled anew, and after receiving an acknowledgment from the representative station, the predetermined time period has elapsed. If a negative response is not returned within a time period, the next group is polled. 4. A broadcasting station comprising: a transmitting station for transmitting broadcast data by wireless multicast communication; and a plurality of receiving stations for receiving the broadcast data. The transmitting station performs fragmentation of the broadcast data as necessary, and Create a frame to which the address of the receiving station group and the transmission sequence number are assigned, perform data transfer to the plurality of receiving stations in one frame transmission, and the receiving station issues an acknowledgment when the broadcast data is correctly received. In addition, when the receiving station detects an error in the frame, the receiving station returns the number of the frame in which the error is detected to the transmitting station by a negative response, and when the transmitting station receives the negative response, A wireless multicast communication for retransmitting broadcast data of a number described in a negative acknowledgment, wherein (1) a transmitting station groups receiving stations that can directly transmit and receive, The transmitting station selects, as a representative station, a receiving station in which the transmission error is most likely to occur from each group as a representative station. (3) The transmitting station sends an address and a sequence number to the receiving station group in broadcast data. The broadcast frame transmission given by
After transmitting the last frame, (4) the transmitting station polls one of the groups and requests a response; and (5) the representative station of the polled group correctly receives the broadcast data. If so, a positive acknowledgment is returned, and if the broadcast data cannot be received correctly, a negative acknowledgment is returned to the transmitting station as a response together with the wrong frame number. (6) The representative in the polled group A station other than the station monitors the result returned by the representative station.If the response returned by the representative station is an affirmative response or if the response of the representative station cannot be monitored, and the If there is something that could not be received, a certain time T
Within one, the negative acknowledgment is returned to the transmitting station with the number of the frame requesting retransmission, and (7) the transmitting station suspends polling when requested to retransmit by a negative response and is immediately requested. If the frame having the number is retransmitted by multicast, and after the retransmission is completed, the representative station of the group that interrupted the polling is polled again, and after receiving an acknowledgment from the representative station, if a negative response is not returned within a certain time T1 (8) The transmitting station repeats (4) to (7), finishes polling all groups, and receives an acknowledgment from the representative station of the last group. Wireless multicast data transfer method, wherein multicast data transfer is completed.