JPS61154240A - Transmission method of retransmission request signal - Google Patents

Abstract

PURPOSE:To transmit simply and efficiently a retransmission signal by using a time location corresponding to the information relating to a packet received in error as the information for the retransmission request signal. CONSTITUTION:In the multiple address packet communication transmitting same message to plural reception stations 2-3 from a transmission station 1, the reception stations 2-4 detect an error of >=1 packet received and returns a burst signal to the transmission station 1 as the retransmission request signal at a time location corresponding to the information relating to the packet detected in error. The transmission station 1 detects the energy of each burst of the said return signal and decides the packet to be retransmitted corresponding to the time position of the burst in which the prescribed amount or over of the energy is detected. Whether each packet is received correctly or received in error, for example, is outputted as the result of discrimination to a shift register 23 sequentially. A gate circuit 25 turns on/off the output of an oscillator 24 based on the content of the shift register 23.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to packet transmission in which the same message is transmitted from one transmitting station to a plurality of receiving stations, particularly over a wireless line or a bus-type wired line. The present invention relates to a method for transmitting a bucket retransmission request signal in a network in which all stations connected to the network can observe information being transmitted on the line.

(Prior art and its problems) When performing broadcast communication in a bus-type network such as a wireless line, all stations connected to the network can observe the information, so information can be transmitted to all stations in one transmission. There is an advantage. However, on the other hand, if a retransmission request is made due to an error in the transmission path, there is a problem that if multiple stations request retransmission at the same time, collisions will occur on the line and information will not be transmitted correctly.

The problem of collision that occurs when a plurality of stations use the same line is well known as the multi-φ access problem, and various solutions have been proposed. This multi-access system is explained in detail in Section 7 of Volume 2 of the book ``Computer Network Construction Technology and Operation Practices'' published by Fuji Techno Systems in 1978. The basic methods for multi-access are a transmission right control method in which each station is given the right to transmit in sequence, and a station that has information transmits, and if a collision occurs, it is detected and delayed by an appropriate amount of time. There is a random access method that avoids collisions by retransmitting data.

In the transmission right control method, collisions do not occur, but in order to control the return timing of the retransmission request signal between each receiving station, it is necessary to soften some information, which makes the control complicated. There is.

Furthermore, the receiving station targeted for broadcast communication generally changes for each communication, making control of return timing between receiving stations even more complicated.

In the random access method, retransmission request signals for broadcast communications are almost always generated simultaneously at multiple receiving stations;
The problem is that the probability of collision is extremely high and the efficiency is low.

(Object of the Invention) An object of the present invention is to provide a simple and efficient method of transmitting a retransmission request signal by using the time position corresponding to information regarding an erroneous packet as information of the retransmission request signal. .

(Structure of the Invention) The method of the present invention detects errors in one or more packets received at each receiving station in broadcast packet communication in which the same message is transmitted from a transmitting station to a plurality of receiving stations; A burst signal is returned to the transmitting station as a retransmission request signal at a time position corresponding to the information regarding the detected erroneous packet, and the transmitting station detects the energy of each burst of the returned signal, and A bucket (1) to be retransmitted corresponding to the time position of a burst detected at a predetermined value or more is determined and configured.

(Principle of the Invention) The present invention utilizes the fact that the signal to be transmitted is a retransmission request signal, and shows a method that can correctly transmit retransmission request information even if a plurality of stations simultaneously transmit and cause a collision.

If the packet number of an erroneous packet is simply encoded and transmitted, when a collision occurs, the transmitting station will not be able to correctly recognize the erroneous packet number of each receiving station.

Therefore, in the present invention, a time position corresponding to the number of packets is set, and a burst signal is transmitted as a retransmission request signal at a time position corresponding to information regarding the packet in which the error occurred.

If the packet number is taken as information about the packet, some kind of burst signal will be observed at the time position corresponding to the packet number of the packet that was received by one or more receiving stations in error, even if interference occurs. Therefore, no signal will be observed at the time position corresponding to the packet number of the packet correctly received by all stations. Therefore, if the transmitting station monitors the received energy at each time position and retransmits only those packets with packet numbers for which energy above a certain level is observed, retransmission requests from all receiving stations can be satisfied.

Furthermore, as described above, each receiving station does not return a retransmission request signal in response to the correctness of each individual packet, but instead sends a retransmission request signal in response to the number of erroneous packets as information regarding erroneously received packets. There is also a method in which the data signal is sent back, and the transmitting station transmits a number of baqueratos corresponding to this number in the form of check pits that are error correction coded for the data signal. In this case, each receiving station discards the packet received in error and decodes it using the retransmitted check packet, so the transmitting station does not need information about which packet was erroneous. When using such a retransmission method, if you match the number of erroneous packets to the time position and use a retransmission request signal transmission method similar to the method described above,
Similarly, an efficient method of transmitting a retransmission request signal can be achieved.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention. In the first embodiment, a case will be explained in which a long message such as a facsimile signal is divided into a plurality of packets and transmitted.

The information input from input terminal 5 is sent to the buffer (BUFFE).
B) Accumulated once in 10. This information is read out sequentially, added with an error detection code by a coder (CODER) 11, modulated by a modem (MODEM) 12, and transmitted from an antenna 6. This information is received simultaneously by receivers 2.3 and 4. Since all receivers have the same configuration, the operation of receiver 2 will be described in detail.

When a packet is received from antenna 7, the modem (MO
It is demodulated by the DEM) 20 and sent to the error detection circuit (ERRORD).
ET) 21, errors in each packet are detected. The received packets are stored in a buffer (BUFFER) 22. At the same time, the judgment result as to whether each packet was received correctly or incorrectly is stored in the shift register (8
(FTR) 23 in sequence. When all packets are received, the shift register 23 stores information on whether each packet is correct or incorrect. Assuming that N packets are received, the number of stages of the shift register 23 will be N stages. Based on the contents of this shift register 23, the receiving line 2 generates a retransmission request signal. That is, shift register 23
Based on the contents of the gate circuit (GATE) 25, the oscillator 2
Turn on/on the output of 4.

As a result, the output of the gate circuit 25 becomes, for example, as shown in (■) in FIG. 3 1al.

Now, N=4, that is, four packets are received, the first and third packets are received at receiver 2, and '
Assume that the third packet and the fourth packet are received in error on the reception line 4, respectively. At this time, the signals transmitted from each station as a retransmission request signal and the signals on the line are shown in Figure 3 (al). These are the burst positions used for the retransmission request signals corresponding to the first, second, third and fourth packets.In the above example, receivers 2.3 and 4 are respectively shown in Figure 3 (al).

A retransmission request signal is issued at the time positions shown in ■ and ■.

The spacing between the burst positions is to absorb the delay difference between each reception therapy.

The transmitter 1 receives the signal shown in Figure 3 (al) from the antenna 6.The received signal is demodulated by the modem 12 and is connected to a time window circuit (WINDOW) which outputs only the burst position signals, bII, b3 and b4. ) 13.The output of the time window circuit 13 is sequentially input to a detector (DETECTOR).
14, and a determination circuit (DECISION) 15 determines whether the energy has reached a certain level. The determination results are sequentially input to the shift register (5FTR) 16. The received signal is as shown in (■) in FIG. 3 la, and it can be seen that the first, third, and fourth packets were received by the receiver in error. In the transmitter 1, the gate circuit (GATE) 18 gates the output of the packet e counter (ADDRE88) 17O indicating the address of the buffer 10 based on the contents of the shift register 16, thereby retransmitting only the packets for which retransmission has been requested.

Each receiving line detects errors only in necessary packets among the retransmitted packets, and if there is an error, a retransmission request signal is transmitted again. In this way, all information can be transmitted without error.

FIG. 2 shows a second embodiment of the invention. Input terminal 10
The information input from 5 is sent to the buffer (BUFFER) 11.
Accumulated once in 0. This information is read out one after another, added with an error detection code by a coder (CODER) 111, modulated by a modem (MODEM) 112, and transmitted from an antenna 106.

This information is received by receivers 102, 103 and 104 simultaneously. Since all receivers have the same configuration, the operation of receiver 102 will be described in detail.

When a packet is received from antenna 107, the modem (
MODEM) 120 and the error detection circuit (ERR)
, 0RDET) 121, errors in each packet are detected. The received packet is stored in the buffer (BUFFER) 12
It is stored in 2. At the same time, the error detection circuit 121 outputs a determination result as to whether each packet was received correctly or incorrectly, and the number of error packets is counted by a counter (COU).
NTER) 124. In the second embodiment, after all packets are received, the contents of the counter 124, that is, the number of error packets, is returned as information. For this purpose, oscillator 1
25 from the gate circuit 126 which outputs the output only at the time position corresponding to the contents of the counter 124, and the modem 12
Modulate it with 0 and send it back. If the same error as in the first embodiment occurs in each receiver, the retransmission request signal returned from each receiver will be as shown in Figure 3 (bl). 1.b2.b3 and b4 have 1 and 2 error packets, respectively.

This is the burst position used for the retransmission request signal in the case of three and four.

The received signal is demodulated by modem 112 and sent to burst position b1.
．． b2. It is input to a time window circuit (WINDOW) 113 that outputs only signals b3 and b4. Time window circuit 1
The output of 13 is sequentially detected by a detector (DETECTOR) 114, and a determination circuit (DECI8ION) 115 determines whether the energy has reached a certain level.

The determination result is stored in the maximum value detector (MAXDET) 116. The maximum value detector 116 stores the last burst position where a burst signal of a certain level or higher was output. In this way, the maximum number of packets received in error in each reception is transmitted to the transmitter 101. The transmitter 101 performs error correction coding on the contents of the buffer 110 in buckets corresponding to this number, and retransmits the data. Error correction encoder (FEC) 11
7 receives the output of the maximum value detector 116 and sends the buffer 11
Error correction encoding is performed on the information stored in 0, and the redundant pits are transmitted as a packet.

This number of redundant packets corresponds to the maximum number of erroneously received packets mentioned above. An example of such a technique is John, J.

Metzner)'s paper tI en imbrobut.
"An Improved Broadcast Redo Transmission Protocol"
etransm-4ssion Protocol)
(IEEE Transaction of Comm.
unications Vol, COM-32
No.

6 June 1984 P, 679-683), but an outline will be explained below. An example is shown in FIG.

In FIG. 4, packets from ■ to ■ are packets that have already been transmitted, and the shaded areas are check pits for detecting errors. On the other hand, an error correction encoder (FEC) 117 reads already transmitted data from the buffer 110 and encodes it in the direction of the arrow in FIG. 4 to form an error correction code. Therefore, the data in the packets ① and ② in FIG. 4 are check pits for the information packets ① to ② in the corresponding positions, respectively. Therefore, when each receiving station receives packets (1) and (2), it can use these packets to correct erroneous packets. Therefore, the transmitter 101 does not need information about which packets were erroneously received, but the receiver only needs to know how many packets were erroneously received.

The output of the error correction encoder 117 is added with an error detection code by the encoder 111, modulated by the modem 112, and transmitted.

In the receiver 102, the packet is demodulated by the modem 120 and an error is detected by the error detection circuit 121 in the same way as a normal packet. If this retransmitted check pit packet is received in error, each receiver repeats the above procedure again and retransmits the packet. Upon reception of a normal check pit packet, an error correction decoder (FECDEC) 123 reads out the already received packet from the buffer 122, performs error correction, and outputs it to the terminal 108. The above procedure is repeated again to retransmit the packet.

In the second embodiment, as in the first embodiment, the retransmission request signal is detected by detecting the energy of the received signal within the time window, so there is no possibility that the retransmission request signals will collide with each other. It is also possible to correctly detect retransmission request signals.

In the second embodiment, instead of sending a retransmission request signal for each packet, only the number of erroneously received packets needs to be sent as information, so the number of time positions required for a retransmission request is reduced. do.

In the embodiment described here, only an error detection code is added to each packet, but the retransmission request signal transmission method of the present invention can be used in the same way even if an error correction code is added. .

(Effects of the Invention) The present invention has the advantage that the retransmission request signal can be easily and efficiently transmitted by using the time position corresponding to the information regarding the erroneously received packet as the information of the retransmission request signal. There is.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the first embodiment of the present invention, FIG. 2 is a diagram showing the second embodiment of the invention, FIG. 3 is a diagram showing the burst position of the retransmission request signal, and FIG. 4 is a diagram showing the burst position of the retransmission request signal. FIG. 7 is a diagram illustrating the operation of the second embodiment of the present invention. 1, 101 ・= ・= transmitter, 2, 3, 4, 102,
103,104----Receiver, 10,110,2
2,122 ...-hay 7 a (BUFFER),
11,111 ・--- Encoder (C0DER),
12. 112.20,120-=-r-tem (MODEM)
, 13, 113... Time window circuit (WINDO
W), 14,114...Detector (DE TEC
TOR), 15,115...determination circuit (DBC
ISION), 16.23 ・-・・・Shift vshiy
, Evening (8FTR), 17 =”f っ) Kara 7ri (
ADDR, ESS), 18.25, 126...
Gate circuit (GATE), 21,121---
Error k) Detection circuit (ERRORDET), 24.1
25-... Oscillator (O20), 116... Maximum value detector (MAX DET), 117...-
・Error correction encoder (FEC), 123...Error correction decoder (FECDEC), 124...
Counter (COUNTBR). −), agent Susumu Uchihara, patent attorney, 72. '3 pa;,
'Figure 1

Claims (3)

[Claims] (1) In broadcast packet communication in which the same message is transmitted from a transmitting station to multiple receiving stations, each receiving station detects an error in one or more received packets, and performs a A burst signal is returned to the transmitting station as a retransmission request signal at a time position corresponding to the information, and the transmitting station detects the energy of each burst of the returned signal, and if the energy is detected to be equal to or greater than a predetermined value, A method for transmitting a retransmission request signal, characterized in that a packet to be retransmitted is determined in accordance with the time position of a burst. (2) The receiving station uses the packet number of the packet in which the error was detected as information about the packet in which the error was detected, and the transmitting station uses the packet number corresponding to the time position of the detected burst with energy above a certain value. A method for transmitting a retransmission request signal according to claim 1, characterized in that the packet is retransmitted. (3) The receiving station uses the number of error-detected packets as information about error-detected packets, and the transmitting station uses the maximum packet error among the time positions of detected bursts with energy above a certain value. The method for transmitting a retransmission request signal according to claim 1, characterized in that the error correction packet to be retransmitted is determined in accordance with the time position corresponding to the number of error correction packets.