JPS61100043A - Transmitter for multiple address communication - Google Patents

Abstract

PURPOSE:To attain retransmission of plural erroneous reception frames with retransmission of one frame by applying exclusively OR to an information frame to be transmitted at each bit, storing and transmitting it. CONSTITUTION:The information frame to be transmitted is inputted to an FIFO buffer 3 via a latch 2 and transmitted to a transmission line via a switch 7, a transmission information load circuit 8 and a transmitter 9. An output of the buffer 3 is inputted to one input terminal of an exclusive OR circuit 4, an output of a retransmission buffer 5 is inputted to the other input of the circuit 4, an output of the circuit 4 is stored again in a buffer 5 and its output is inputted to a buffer 6 and the switch 7. The reception acknowledgement from each reception station is inputted to a reception discrimination circuit 11 via a receiver 12 and when the received signal is the first retransmission request, the circuit 11 records the frame number and the reception station. Then the switch 7 is thrown to the position of the output of the buffer 5 and the signal is transmitted via the circuit 8 and the transmitter 9.

Description

[Detailed Description of the Invention] (Industrial Application Field) With the diversification of communication forms such as information provision services and conference communications, the decentralization of databases in communication networks, and the use of satellite lines, Broadcast communication, which transfers information to multiple destinations simultaneously, is becoming increasingly important. The present invention relates to a transmitting device in a transmitting station when performing the above-mentioned broadcast type communication.

(Prior art and its problems) Communication in which there are multiple communication partners and the same information is transferred to multiple destinations at the same time is called broadcast communication. Automatic error retransmission control in broadcast communication (person 1'L Q: A
Various protocols have been proposed for the U'IN) MATIC (ShoP 閘联联北ST), and one of them is a method called the selective retransmission method (5ELECTI REPEAT). In this method, the transmitting station transmits a plurality of information frames and retransmits only the information frames for which a retransmission request has been made due to erroneous reception from each receiving station. However, unlike in the case of one-to-one communication, since there are a plurality of receiving stations, the frames that are received in error are generally different for each receiving station. For example, among the 10 information frames sent by the transmitting station, receiving station 1 receives the second frame, receiving station 2 receives the seventh frame,
Assuming that the receiving station 3 receives the 9th frame by mistake, the transmitting station receives the retransmission request from each receiving station and receives the 3rd frame, the 2nd frame, the 7th frame, and the 9th frame.
one must be resent. However, in this case, for example, only receiving station 1 has received the second frame in error, and the other receiving stations have already received the second frame. In this way, each receiving station requires 1 retransmission.
Even though the number of frames is K, the transmitting station has to retransmit three frames, and the line utilization efficiency generally deteriorates significantly compared to the case of one-to-one communication.

(Objective of the present invention) An object of the present invention is to provide a system for retransmitting, when multiple receiving stations receive different information frames in broadcast communication, instead of retransmitting all the erroneously received frames one by one. To,
It is an object of the present invention to provide a transmitting device that can simultaneously achieve retransmission of a plurality of erroneously received frames by retransmitting one frame for the plurality of erroneously received frames.

(Structure of the Invention) According to the present invention, there is provided a transmitting device that enables each receiving station in broadcast communication to effectively perform retransmission when receiving an error message, and which transmits information frames to be transmitted bit by bit. An exclusive OR circuit and a buffer for sequentially exclusive ORing and storing information frames in a range that includes at most one erroneously received frame by the same receiving station, and in a range as large as possible. A transmitting device is obtained, which is characterized in that it is provided with a retransmission control section for checking and controlling whether or not to retransmit the exclusive ORed frame.

(Principle of the present invention) The present invention achieves the above object based on the principle described below.

N equal length M) bit strings (x(1,1).

x (2, 1), ・=, x (M, 1)), (x (1, 2
), x(2,2), .=.

x(M, 2)), ..., (x(1, N), x(2,
N), -, x (M, N)), then y (31"
X(J+')(J''1*2+...M) Here indicates exclusive OR.

The bit string of length M (y(1), yt2), ... y(to)) formed by y(jl) obtained by the operation is
We will call it an N-sum bit string. If we define each bit string as above, when we know any N-1 bit strings out of the original N bit strings, we can convert the N-1 bit strings and the N sum bit string into bits. The remaining one bit string can be obtained by performing an exclusive OR for each bit string. Based on this principle, the transmitting station does not retransmit a specific frame, but instead retransmits a frame obtained by exclusive ORing several frames bit by bit. At this time, by determining the frame to be exclusive-ORed according to the method described later, each receiving station can ensure that at most one frame is received in error among the multiple exclusive-ORed frames that make up the retransmitted frame. Therefore, regardless of the frame that each receiving station received in error, it is possible to recover the erroneous frame by retransmitting the one XOR 7 frame.

The transmitting station continuously transmits information frames, and when it receives the first retransmission request for a frame that is not included in the range of the previous retransmission, it records the receiving station name and the frame number that was received in error, and from then on For retransmission requests, the name of the receiving station is recorded.

If a second retransmission request comes from the same station, all bits of the frames transmitted before the second erroneously received frame (not including the second erroneously received frame) Resend the exclusive ORed frame. If a second retransmission request comes from the same station,
If a predetermined number of frames have been transmitted, counting from the first erroneously received frame that was not included in the previous retransmission range, reception confirmation must be performed by that point to prevent buffer overflow on the receiving station side. Exclusive OR is performed up to the received frame and retransmitted. In either case, each receiving station has only one erroneously received frame within the retransmitted frame range.

If a retransmission frame is received in error, there is a risk that the receiving station's buffer will overflow, so the same retransmission frame may be sent out in duplicate depending on the error rate of the transmission path.

(Example) The present invention will be described in detail below using the drawings. For the sake of explanation hereinafter, the round-trip propagation delay of the transmission path will be referred to as S frame. (In other words, after transmitting a certain seven frames, eight frames are transmitted until a reception response for that frame is received.) In summary, FIG. 1 is a block diagram showing an embodiment of the present invention. An information frame to be transmitted is input from a terminal 1 to a FIFO buffer 3 via a latch 2, and is also transmitted from a terminal 10 to a transmission line via a switch 7, a transmission information addition circuit 8, and a transmitter 9. Each time one frame is input from the left end of the FIFO buffer 3, its contents are shifted to the right by one frame.

The capacity of the FIFO buffer 3 is assumed to be (8+1) frames. Output from FIFO buffer 3 is exclusive.

is input to one input terminal of the logical OR circuit 4.

The output of the retransmission buffer 5 is input to the other input terminal of the exclusive OR circuit 4, and the output of the exclusive OR circuit 4 is stored in the retransmission buffer 5 again. The retransmission buffer 5 has a capacity for -frames, and its output is input to the input of the exclusive OR circuit 4, as well as to one input terminal of the buffer 6 and the switch 7. On the other hand, the reception from each receiving station.

The reception response is input to the reception determination circuit 11 via the terminal 13 and the receiver 12. If the received reception response is the first retransmission request for a frame that is not included in the range of the previous seven retransmitted frames, the reception determination circuit 11 records the frame number and receiving station. From then on, each time a retransmission request comes, record the receiving station name, and if a second retransmission request comes from the same station, or receive S-1 reception responses counting from the first retransmission request frame recorded above. If received, latch 2 is turned off, switch 7 is switched to output from retransmission buffer 5, and the contents of buffer 5 are transferred to switch 7,
It is transmitted via the transmission information addition circuit 8 and the transmitter 9. At that time, the buffer 5 contains the exclusive OR bit by bit of seven frames up to a frame number one smaller than the frame number of the reception response received immediately before.

FIG. 2 is a block diagram showing an example of a receiving device used in the present invention. The received information 7 frame is input terminal 14
, and is input to the reception determination circuit 16 via the receiver 15 . If the reception determination circuit 16 receives a frame other than the frame it expects to receive, it ignores it. When the received information frame is received normally, the information portion of the received frame is input to the FIFO buffer 17, and a signal indicating normal reception and a 7 frame number are sent to the reception response transmitter 24. A reception response indicating normal reception is transmitted from the terminal 26 via the reception response transmitter 244-i transmitter 25.

If the received information frame is erroneously received as 9, the reception determination circuit 16 returns zero of the information frame.
The frame number is input to the O buffer 17, and the frame number is notified to the reception response transmitter 24 along with a signal indicating erroneous reception. The reception response transmitting device 24 transmits a retransmission request from a terminal 26 via a transmitter 25. FIFO buffer 1
7 is a capacity] (S+1) frame, and every time one frame is inputted, the 8+1st frame from the right end is outputted, inputted to the buffer 22, and inputted to the exclusive OR circuit 19 via the latch switch 18.

The output from the buffer 20 is input to the other input terminal of the exclusive OR circuit 19, and the bit-by-bit exclusive OR output is sent to the buffer 20 again via the switch 21.
is stored in The buffer 20 has a capacity for -frames. If the received frame is a retransmission frame, the reception determination circuit 16 inputs the information portion of the retransmission frame to the exclusive OR circuit 19 via the latch switch 18. The output from the buffer 20 is input to the other input of the exclusive OR circuit 19, and the output obtained by calculating the exclusive OR for each bit is sent to the buffer 2 via the switch 21.
2, is written at the position of the frame that was received in error. The buffer 22 sequentially outputs one normally received information frame to the output terminal 23. On the other hand, the information part of the retransmitted frame is latched in the latch 18, and it is necessary to input it to the exclusive OR circuit 19 once again while keeping the other input of the exclusive OR circuit 19 cut off (that is, keeping it at zero). Therefore, the information part of the retransmitted frame is sent to the switch 21.
The data are stored as they are in the buffer 20 via. In this way, the buffer 20 of each receiving station always stores the bit-by-bit exclusive OR of frames in the same range as the incoming retransmitted frame, and moreover, if there is an error received within that range, Since retransmitted frames are sent at intervals of at most one frame, each receiving station performs an exclusive OR of the retransmitted frame and the one stored in the buffer 20 to eliminate the desired error reception. frames can be recovered.

(Effects of the Invention) As explained above, according to the present invention, the number of retransmissions can be reduced compared to the conventional automatic retransmission control method. The effects of the present invention are most noticeable when each receiving station receives different frames one by one. For example, if M receiving stations incorrectly receive different frames one by one, the conventional method requires retransmission of M frames, but with this method, only one retransmission is required. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 shows information 7 and 1 transmitted by the device of the present invention. FIG. 2 is a block diagram illustrating an example apparatus for receiving a program. In the figure, 1, 13, and 14 are input terminals, 2 is a latch, and 3
．． 17 is a FIFO buffer, 4.19 is an exclusive OR circuit, 5 is a retransmission buffer, 6.2022 is a buffer, 7
．． 21 is a switch, 8 is a transmission information adding circuit, 9.25 is a transmitter, 10, 23.26 is an output terminal, 11 is a reception judgment circuit, 12.15 is a receiver, 16 is a reception judgment circuit, 18
is a latch switch and a 24-digit reception response transmitter.

Claims (1)

[Claims] A transmitting device used in broadcast communication that simultaneously transfers information with the same content to multiple destinations, which receives information frames to be transmitted frame by frame from a source and retransmits the information frames or the retransmission buffer described later. A transmitting unit that adds transmission information to a source frame and sends it out to a transmission path, and a transmission unit that adds transmission information to a frame and sends it to a transmission path, and a transmission unit that adds transmission information to a frame and sends it to a transmission path, and an information frame that is obtained by exclusive ORing the information frame received from the source with information frames that were received before, bit by bit. An exclusive OR circuit for calculating an exclusive OR, a retransmission buffer for storing a retransmission frame obtained by exclusive ORing the information frame output from the exclusive OR circuit bit by bit, and A receiver receives a reception response, and checks the contents of the reception response received by the receiver, and collects information frames within a range that includes at most one erroneously received frame by the same receiving station, and in as wide a range as possible. 1. A transmitting device for broadcast communication, comprising a retransmission control section for checking and controlling for transmitting a frame obtained by exclusive ORing bit by bit as a retransmission frame.