JP3031008B2 - Data transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method for an automatic retransmission request at the time of data transmission in a radio communication system or the like.

[0002]

2. Description of the Related Art In recent years, a data transmission system using wireless has been receiving attention, and a mobile communication system capable of communicating both voice and data has been developed.
In such a system, various error control methods are used to maintain high reliability of data transmission. However, a conventional automatic retransmission request (automatic transmission
Repeat request: Automatic-Repe
at-reQuest (hereinafter referred to as ARQ) will be described.

[0003] In the ARQ system, data to be transmitted on the transmission side is error-detected and coded according to a predetermined procedure and transmitted.
The receiving side performs error detection according to the procedure corresponding to the above procedure,
When an error is detected, a data transmission method for automatically requesting the transmitting side to perform a retransmission request. Typical examples are stop and wait (hereinafter referred to as SAW) and go-back N (Go-Back). −
N; hereinafter referred to as GBN), and repeated selection (Select)
ave-Repeat (hereinafter, referred to as SR)).

[0004] The SAW method is the most basic of the ARQ method. The transmitting side decomposes data to be transmitted into a plurality of blocks, transmits one block, and then receives an acknowledgment signal (ACK) or retransmission from the receiving side. This is a method of waiting without transmitting the next block until a request signal comes. Since both procedures and devices can be simplified, they are used in low-cost and low-speed systems.

In the GBN system, data blocks are sequentially transmitted without waiting for a response from the receiving side. When a retransmission request signal is received from the receiving side, not only the block requested to be retransmitted but also the N-1 block following the block are transmitted. This is a method for performing retransmission.

FIG. 3 shows a retransmission procedure of the conventional GBN system in which N =
4 is shown as an example. N is a return delay time until a response signal to the transmitted data block is received (Round-Trip-Delay: RT)
It is set to an integer equal to or greater than the number of blocks that can be transmitted in D).

The following is a brief description with reference to FIG. TX
B is the transmission block number, RXB is the reception block number,
TACK indicates the latest successful transmission block number confirmed on the transmission side, and RACK indicates the reception confirmation block number on the reception side. Further, as the judgment contents of the received data block on the receiving side, s is a valid block without error, e is a block in which error is detected and invalid, and d is a block received without error and the block number is not next to RACK. This indicates that the block has been invalidated. A solid line or a dotted line with a cross in the figure indicates that an error has occurred during wireless transmission.

The communication station on the transmitting side divides the transmission data stored in the buffer memory into a plurality of blocks in units of a predetermined number of information, and assigns a continuous block number (TXB) to each block data. Next, the transmission success block number counter (TACK) in the control unit is reset to zero.

Next, a line connection request is made to the partner communication station, and after the line is established, the data blocks are read out from the buffer memory in numerical order, and subjected to error detection coding according to a predetermined coding rule and transmitted. .

On the other hand, the receiving communication station resets the acknowledgment block number counter (RACK) when the line connection is first established in the same manner as the transmitting station. Next, when data is received, the received data block is subjected to error detection corresponding to the error correction coding rule. If no error is detected in the received data block and the block number is the number next to the number stored in the RACK, the RACK is updated to the block number that has been successfully received, and the data in the block is processed. To start. If an error is detected in the received block or if no error is detected, but the block number is not the number next to the RACK, the RACK is not updated and the data in the received block is discarded. The receiving side performs the above processing every time a data block is received, and returns RACK as a response signal to the transmitting side.

[0011] If no error is detected in the received response signal, the transmitting communication station compares the RACK of the receiving station in the response signal with the TACK of its own station.
If it is larger than ACK, the latest received RACK is TA
CK is set, and the block of the next number is sent as it is. RAC
If K is not updated on the receiving side and matches TACK, it is determined that an error has occurred in the transmission data, and the process returns to the block with the next number after TACK and starts retransmission. Also, when an error is detected in the received response signal, similarly, the process returns to the next number of TACK and performs retransmission.

The retransmission procedure of the GBN method has been described above. Since it has a relatively simple procedure and does not require a buffer memory on the receiving side, it is used in a wired system with good line quality. However, every time an error is detected in a retransmission request or response signal, N blocks are returned and retransmission is performed. Therefore, if these signals or the same block are repeated many times, the transmission speed will be significantly reduced.

In the SR system, similar to the GBN system, data blocks are sequentially transmitted without waiting for a response from the receiving side, but the retransmission procedure when an error is detected on the receiving side is different. The receiving side performs error detection for each received data block, and returns each block number and information indicating whether the block was received without error (ACK) or not (NAK) to the transmitting side as a response signal. The data block in which the error is detected is discarded after storing the block number, and the data processing is suspended until the data block of the discarded number is correctly received. The correctly received data blocks with numbers following the discarded number are stored in the buffer memory, and the discarded data blocks are retransmitted, correctly received and processed, and then stored in the buffer memory first. The processing is continued by sequentially reading the blocks.

On the transmitting side, a NAK is used as a response signal from the receiving side.
Is retransmitted, and if an error is detected in the received response signal, the block of the number to be responded by the response signal is retransmitted.

In the SR system, although the number of retransmission blocks is smaller than in the GBN system, a high transmission speed can be obtained, but the procedure and the device become complicated. In addition, since other data blocks received without error are stored before the data block in which the error is detected is correctly received, an infinite buffer memory is theoretically required on the receiving side.

[0016]

Among the above-mentioned conventional systems, the SR system can provide the highest transmission efficiency, but the complexity of the system and the necessity of a large-capacity buffer memory necessitate the simplification of the system. It is difficult to use mobile communication and the like aiming at miniaturization and weight reduction of mobile devices due to the increase in size. On the other hand, in the GBN system, although the apparatus can be relatively easily formed, there is a problem that the transmission efficiency is significantly reduced when the number of retransmissions is increased.

An object of the present invention is to solve the above-mentioned conventional problems and to improve transmission efficiency with a relatively simple apparatus by suppressing the number of retransmissions due to an error in a response signal based on the GBN system.

[0018]

In order to achieve the above object, an automatic retransmission request system according to the present invention is based on the GBN system and includes a case where an error is detected in a response signal on the transmitting side and a case where an error is not detected. Is used to switch the retransmission procedure.
The transmission side continues transmission without waiting for a response from the reception side, and detects an error in the response signal received after the return delay time by the same error detection coding as that on the reception side. If the response signal is received without error and is a retransmission request, N blocks are retransmitted starting with the number following TACK. During this time, RACK and TACK of the response signal are not compared until the retransmission of N blocks is completed. On the other hand, if an error is detected in the received response signal, the RACK information becomes unknown.
And TACK are not compared. However, since there is a possibility that a retransmission request has been made without updating the RACK, switching is made to a retransmission procedure of the SR method in which only a block that is to be received or acknowledged by the response signal is retransmitted, and the next response signal is transmitted. wait. The next response signal is received correctly and RA
If the CK has been updated, transmission is continued from the number following the block number transmitted before retransmission. If the RACK is not updated and the request is a retransmission request, switching to the retransmission procedure of the GBN method is performed. In this case, only the remaining blocks excluding the blocks already retransmitted by the SR method are retransmitted from the block number of the retransmission request. To return to the normal transmission state.

On the receiving side, the conventional GBN procedure is used. That is, error detection of a received data block is performed using error detection coding such as a cyclic code, and R
The ACK is compared with the reception block number to determine whether the received data is valid or invalid, and the RACK is updated if necessary, and returned as a response signal to the transmission side.

As described above, the automatic retransmission request method of the present invention is based on the GBN method. If an error is detected in the response signal on the transmission side, the procedure on the reception side is performed in the same way as the GBN method. It is configured to switch to the SR method.

[0021]

According to the present invention, when a response signal received on the transmitting side is incorrect by the above method, if it is determined in the next response signal that a retransmission request has been made with the response signal, retransmission is already performed by the SR method. Since the retransmission is performed after a certain block, the number of retransmission blocks is the same as that of the conventional GBN system. On the other hand, an error is detected in the response signal even though the data block is correctly received on the receiving side. Since the number of invalid retransmission blocks is reduced, the transmission efficiency can be improved as compared with the conventional GBN method. Furthermore, since the receiving device does not require a buffer memory, the conventional G
It is possible to simplify the device similar to the BN method.

[0022]

An embodiment of the present invention will be described below.

FIG. 1 is a block diagram of an apparatus for realizing a data transmission method according to one embodiment of the present invention, and FIG. 2 shows a retransmission procedure of the automatic retransmission method of the present invention in a case where N = 4. .

In FIG. 1, reference numerals 10 and 20 denote data control unit blocks of a radio communication device of a radio mobile station or a radio base station. For example, the data control unit 10 is a transmission side and the data control unit 20 is a reception side. In these circuit blocks 10 and 20, reference numerals 11 and 21 denote communication control units for transmitting and receiving control signals for data communication between a control unit for performing overall control and an encoding unit. In addition to encoding according to the conversion rule, an encoding unit for decoding the received data that has been encoded and received, 13 and 23 are buffer memories for temporarily storing transmission data, and 14 and 24 are encoding carrier waves of a predetermined frequency. The transmission data is modulated by the transmission data, and the antennas 17 and 27 are transmitted through the transmission / reception switches 16 and 26.
, Transmitting units 15 and 25 are antennas 17 and 27
Is a receiving unit that receives and demodulates the carrier wave received at. Each of the communication control units 11 and 21 has a counter (TACK, RACK) for storing the numbers of the transmission and reception blocks.

The operation will be described below. First, the communication control unit 11 on the transmission side divides transmission data stored in the buffer memory 13 into a plurality of blocks in units of a predetermined number of information (for example, in units of 256 bits), and assigns a continuous block number to each block data. . Next, the transmission success block number counter TACK in the communication control unit 11 is reset to 0.

Next, a line connection request is made to the partner radio station, and after the line is established, the data blocks are read out from the buffer memory 13 in numerical order, and an error in the encoding unit 12 according to a predetermined encoding rule is obtained. The detection encoding is performed and transmitted from the transmission unit 14. On the other hand, the receiving-side radio station resets the acknowledgment block number counter (RACK) when the line connection is first established in the same manner as the transmitting side. Next, when data is received, error detection of the received data block is performed according to the procedure of the receiving side of the GBN method,
It determines whether to update RACK and returns a response signal to the transmitting side.

When no error is detected in the received response signal, the transmitting-side radio mobile station determines whether or not the request is a retransmission request according to the GBN procedure as in the receiving side. It returns to the block of the number and starts retransmission.

On the other hand, if an error is detected in the reception response signal, the signal block is discarded, compared with RACK,
No processing such as updating of ACK is performed. Here, considering that there is a possibility that RACK has not been updated (retransmission request has been made), only one block of the data block of the number that was to be returned as RACK in the response signal is retransmitted. The SR method is used. At this time, the latest block number transmitted before retransmission is stored. Next, when the response signal is received without error, if the RACK in the response signal is larger than the block number retransmitted one time before, the state returns to the state before the retransmission processing is performed, and the block stored beforehand is returned. The block following the number is transmitted. Further, when the RACK is smaller than the block number retransmitted one time before, the number of retransmitted blocks can be minimized by performing further retransmission if necessary.

During retransmission of N blocks from the block requested to be retransmitted by the GBN method, retransmission is not performed by the SR method because retransmission has already been performed even if an error is detected in the reception response signal.

The procedure described above will be specifically described with reference to FIG. TXB indicates a transmission block number, RXB indicates a reception block number, TACK indicates a latest transmission success block number confirmed on the transmission side, and RACK indicates a reception confirmation block on the reception side. Also, as in the case of FIG. 3, the contents of the judgment of the received data block on the receiving side are s, a valid block without error, e, a block in which an error was detected and invalid, and d, a block number of RACK. Indicates a block that is invalid because it is not next to. A solid line or a dotted line with a cross in the figure indicates that an error has occurred during wireless transmission.

In this embodiment, since N = 4, a response signal on the receiving station side to the first block 1 is received after the transmission of block 4, and FIG.
1, since TACK = 0, the transmitting side control unit 11
K is updated to 1 and block 5 is transmitted as it is. The same processing is performed for the response signal of block 2 and block 6 is transmitted. However, since an error occurred during transmission to block 3 in the x1 part in the figure, RACK was not updated on the receiving side and RACK = 2 The response signal is returned as it is. The transmitting side receives this response signal without error, and RACK = TACK
Therefore, the process returns to block 3 to start retransmission by the GBN method (in the case of × 4, similarly, four blocks are retransmitted by going back to block 10). Until the next 6 blocks are retransmitted, even if the response signal is erroneous as in × 2, the retransmission process has already been started.
R-system retransmission is not performed. This is the same in the case of × 5.

Next, if the receiving side receives the block 6 without error, and if the transmitting side detects an error in the response signal updated to RACK = 6 (× 3 in FIG. 2), the transmitting side normally performs Is suspended, and block 6 is retransmitted. Then, since the RACK of the response signal received without error is 7, the operation returns to the normal state and the transmission from the block 10 is continued. On the other hand, when the response signal is continuously incorrect, such as the response signals of the transmission blocks 11, 12, and 13 in FIG.
8) Continue retransmission by the SR method until an error-free response signal is received. When an error-free response signal is received, RACK is compared with the previously transmitted block number,
When RACK is large, the state returns to the state before the retransmission process is performed, and when RACK is small, transmission is performed continuously from the next number of RACK. In this embodiment, since the RACK is 14 and is larger than the previously transmitted TXB = 13, the state returns to the state before the retransmission processing is performed, and the transmission is continued from the block number 15.

As described above, according to the present embodiment, the retransmission method at the time of data transmission is divided into a case where a retransmission request is made and a case where it cannot be determined whether or not a retransmission request has been made, by switching the retransmission method. The transmission efficiency can be increased without complicating the receiving device.

[0034]

As described above, as an effect of the present invention, as a transmitting side retransmission procedure at the time of data transmission, when a retransmission request is made, GBN retransmission is performed, and whether or not the retransmission request is made is determined. When it cannot be determined (when an error is detected in the reception response signal), the configuration is changed to the temporary SR method and retransmission is performed. In the case of the SR method, the state returns to the state before retransmission by the next response signal, or the mode is switched to the GBN method in which retransmission is continued. Therefore, the number of retransmissions can be reduced as compared with the conventional GBN method, and the receiving side can use the conventional GBN method. A procedure similar to the scheme can be used. Therefore, the transmission efficiency can be increased as compared with the conventional GBN system without complicating the receiving side device.

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus for realizing a data transmission method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a retransmission procedure of an automatic retransmission request in the apparatus.

FIG. 3 is a diagram showing a retransmission procedure of a conventional go-back N system.

[Explanation of symbols]

 10, 20 Data control unit block of wireless communication apparatus 11, 21 Communication control unit 12, 22 Encoding unit 13, 23 Buffer memory 14, 24 Transmission unit 15, 25 Receiving unit 16, 26 Transmission / reception switch 17, 27 Antenna

────────────────────────────────────────────────── (5) References JP-A-56-35550 (JP, A) JP-A-62-108632 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 1/18

Claims (2)

(57) [Claims] A transmission circuit has a function of transmitting a signal after performing predetermined error detection coding on transmission data, and a receiving circuit includes a decoding circuit corresponding to the error detection coding in a received signal. If an error is detected in the received signal during data transmission between wireless communication stations in a wireless data communication system with a transceiver having a function of detecting an error by performing transmission and reception, the data transmission side wireless communication station transmits to the reception side. When the response signal from the wireless communication station is received without error, and the response signal is a retransmission request, retransmission is performed according to the go-back N method of retransmitting N blocks up to the retransmission-requested block and performing retransmission. If an error is detected, the retransmission procedure is temporarily switched to the selective repetition method in which only the block that is to be acknowledged by the response signal is retransmitted, and retransmission is performed with the next response signal. If it is determined that the request was a transmission request, the procedure returns to the procedure of the go-back N method again, and the remaining blocks except the block retransmitted by the selective repetition method are retransmitted. If not, a data transmission method characterized by switching a retransmission procedure to return to a state before retransmission and continue transmission. 2. The data receiving wireless communication station has a reception confirmation block number counter, compares the number stored in the counter with the number of a data block received without error, and stores the data block number in the counter. Except for the number next to the stored number, the counter number is not updated and the data block is not processed, and a request is made to the transmitting communication station to retransmit the data block having the number next to the counter number. 2. The data transmission method according to claim 1, wherein a buffer memory for storing the received data block in the receiving circuit is not required.