JPH08130541A - Method for transmitting data - Google Patents

Abstract

PURPOSE: To provide a data transmitting method capable of simplifying processing for data transmission and attaining high speed communication. CONSTITUTION: A transmitting side adds a CRC code and an RS code to data to be transmitted and transmits the code-added data by the processing of steps S1 to S5, S7. When prescribed packets out of received packets are continuously normal, a receiving side transmits information indicating the unnecessity of error correcting redundant data to the transmitting side. At the time of receiving the information from the receiving side (step S6), the transmitting side transmits data without adding the redundant data in accordance with the information.

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 transmitting data using a wireless data transmission line.

[0002]

2. Description of the Related Art There is a LAN (Local Area Network) as a comprehensive communication network for connecting images within a company or one region and transmitting images and sounds using a computer. This LA
Some Ns use a wireless data transmission line in addition to a telephone line. According to the wireless data transmission line, L
Since the AN terminal wirelessly transmits data, the degree of freedom of the installation location of the terminal or the like is increased.

Some LANs transmit data by dividing the data into packets. In a LAN using a wireless data transmission line, an error may occur in the received data due to the influence of this transmission line. However, since the data is transmitted in packets, the transmitting side may retransmit the data in the portion where the error has occurred. Therefore, in packet data transmission, the transmission efficiency can be improved.

However, in packet data transmission,
Since the transmitting side adds redundant data for error detection to the data or adds an address or the like to each packet, each packet length becomes long. As a result, the data transmission efficiency decreases.

Therefore, for packet data transmission,
Some transmitters change the packet length according to the number of retransmission requests. That is, when the quality of the transmission path is high and the packet is not retransmitted, the transmission side lengthens the packet length. This improves the data transmission efficiency. When the quality of the transmission path is poor and retransmission is performed, the packet length is shortened. This reduces the amount of data to be retransmitted.

Such a data transmission method is disclosed in Japanese Unexamined Patent Publication No.
No. 125551.

[0007]

However, the above-mentioned data transmission method has the following drawbacks. In this data transmission method, the transmission side measures the number of packet retransmissions.
Then, since the packet length is set according to the number of times of retransmission, processing on the transmitting side becomes complicated. For this reason, this data transmission method is not suitable for high-speed data communication, since the transmission side cannot perform rapid processing.

It is an object of the present invention to provide a data transmission method which eliminates such drawbacks and simplifies the processing relating to data transmission and enables high speed communication.

[0009]

In order to achieve the object, the invention of claim 1 is a data transmission method in which a reception side receives data from a transmission side via a wireless data transmission path. Then, the redundant data for error detection is added to the data to be transmitted, the data to which the redundant data is added is divided into blocks, the redundant data for error correction is added to each block, and a plurality of blocks of data are packetized. The receiving side sends an unnecessary notification of redundant data for error correction to the sending side when a predetermined number of consecutive packets are normal among the received packets, and the sending side sends the notification from the receiving side. When the notification is received, the data is transmitted according to the notification except the redundant data for error correction.

According to a second aspect of the present invention, in the data transmission method in which the reception side receives the data from the transmission side via the wireless data transmission path, the transmission side has the data to be transmitted.
Redundant data for error detection is added and the data is transmitted. When the receiving side detects an error in the received data, it sends a notification of the addition of redundant data for error correction to the transmitting side, and the receiving side receives it. When the notification from the side is received, the data to which the redundant data for error detection is added is divided into blocks, the redundant data for error correction is added to each block, and the plural blocks of data are transmitted as one packet.

[0011]

According to the first aspect of the invention, the receiving side sends an unnecessary notice of redundant data for error correction to the transmitting side when a predetermined number of packets among the received packets are in succession. Upon receiving the notification from the receiving side, the transmitting side transmits the data according to the notification without adding the redundant data.

As a result, the receiving side has only to decide whether or not to add redundant data for error correction, so that the processing can be simplified as compared with the conventional case.

Also, since the packet length is shortened when no error occurs, the data transmission efficiency and throughput can be improved, and high speed communication becomes possible.

According to the second aspect of the invention, when the receiving side detects an error, the receiving side sends a notification of addition of redundant data for error correction to the transmitting side. The transmitting side, in response to the notification from the receiving side, blocks the transmission data to which the redundant data for error detection is added, adds the redundant data for error correction to each block, and converts the plurality of blocked data into one. Send as a packet.

As a result, if the data transmission is normal, the data transmission is continued without adding redundant data for error correction. As a result, the processing related to data transmission can be simplified as compared with the conventional one, and high-speed communication becomes possible.

Further, when the data transmission is normal, the data length can be shortened from the start of the communication, so that the data transmission efficiency and the throughput can be improved, and the high speed communication can be realized. It will be possible.

[0017]

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

FIG. 5 is a schematic diagram showing a system for implementing the present invention. This system is necessary to configure the wireless LAN shown in FIG. Wireless LA
In N, the host computer 11 is connected to the controller 12. The controller 12 is a device capable of two-way wireless communication, and communication devices 13 and 14 are included in the service area of the controller 12. Communication device 1
Terminals 15 and 16 are connected to 3 and 14, respectively.

In the system used for this wireless LAN, the controller 12 includes the modem device 1 and the wireless device 2, and the communication device 13 includes the wireless device 3 and the modem device 4. The communication device 14 is similar to the communication device 13.

In this system, the controller 12 is
It is connected to the communication devices 13 and 14 by a wireless data transmission path. Terminals 15 and 16 are connected to the modulator / demodulators 1 and 4, respectively. Further, the modulation / demodulation devices 1 and 4 include error control units 1A and 4A that perform error control, and the wireless devices 2 and 3 include detection units 2A and 3A that detect a power level.

In this system, for example, when the controller 12 serves as the transmission side and the communication devices 13 and 14 serve as the reception sides to transmit data, the modulation / demodulation device 1 is operated from the terminal by the procedure shown in the flowchart of FIG. Process data. Upon receiving the data from the terminal, the modulation / demodulation device 1 adds dummy data to the input data,
The data length is set to a multiple of 16 bytes (step S1).
Since the CRC code described later is 16 bits, the modulation / demodulation device 1 sets the code length to 3276 including this CRC code.
Use 7 bits or less. The modulation / demodulation device 1 adds redundant data for error detection to the data to which the dummy data has been added (step S2).

As redundant data for error detection, for example, C
RC (Cyclic Redundancy Check) code is used. The modulation / demodulation device 1 transforms the input data according to a predetermined rule, and divides the transformed data using a preset generator polynomial. The modulation / demodulation device 1 adds the remainder of the division as a CRC code to the last part of the transformed data. This CRC code is 16-bit redundant data.

After step S2, the modulation and demodulation device 1 divides the data to which the redundant data for error detection is added into 16 bytes, and blocks the data (step S).
3). After step S3, the modulation / demodulation device 1 checks whether or not a notification of RS (Reed Solomon) coding has been received from the receiving side (step S4).

Upon receiving the RS encoding notification, the modem 1 performs RS encoding and adds an RS code which is 4-byte redundant data (step S5). The RS code is for correcting an error that occurs in one block. In the RS code, the code length is 20 bytes, the information portion is 16 bytes, and the minimum distance is 5.

When, for example, n blocks are generated by the processing in step S5, the data has the format shown in FIG. From the first block to the (n-1) th block, 16-byte data 101 is added with 4-byte redundant data 102 by RS coding. On the other hand, the CRC code 104 is added to the end of the data. For this reason, the n-th block has a structure in which 2-byte CRC code 104 is added to 14-byte data 103, and 4-byte redundant data 105 is added by RS encoding. Further, dummy data 103A is added after the data 103, if necessary.

The modulation / demodulation apparatus 1 treats the thus generated 1 block to n blocks as one packet which is a unit of communication.

The state of RS coding is the wireless LA of FIG.
It corresponds to the N controller 12 and the communication device 14. The communication device 14 is several tens of meters away from the controller 12, and there are obstacles and the like in the middle of the wireless data transmission path. Further, the communication device 14 is in a moving state. As a result, the power of the signal received on the receiving side fluctuates, and there is a high possibility that an error will occur. In this state, R
Since S-coding is required, the above-mentioned processing is performed.

When the RS coding notification is not received in step S4, the modem 1 does not perform the RS coding (step S6). As a result, the modulation / demodulation device 1 does not add the 4-byte redundant data 102 and 105 by RS coding in the data of FIG. As a result, the packets shown in FIG. 8 are generated.

The state where RS coding is not performed corresponds to the controller 12 and the communication device 13 of the wireless LAN shown in FIG. Since the communication device 13 is only a few meters away from the controller 12, there is no obstacle in the wireless data transmission path. In this state, fading does not occur, data errors rarely occur, and RS coding is unnecessary.

The processes of steps S4 to S6 are necessary for changing the packet length. Thereby, if the transmission characteristic is good, the modulation / demodulation device 1 shortens the packet length.

After step S5 or step S6, the modulation / demodulation device 1 modulates the data of each generated packet and outputs it to the radio device 2 (step S7). The wireless device 2 converts the modulated data from the modulation / demodulation device 1 into a high frequency signal and wirelessly transmits it to the receiving side.

The radio device 3 on the receiving side receives the data sent by the radio wave from the transmitting side, and converts the received signal into the intermediate frequency band (IF band) or the base band band. The detection unit 3A of the wireless device 3 detects the power level of the received signal,
The detection result is sent to the modem 4.

Upon receiving the data from the wireless device 3, the modulation / demodulation device 4 performs the processing shown in FIG. That is, the modulation / demodulation device 4 demodulates the data of the wireless device 3 and extracts the RS-coded data (step S11). The modulation / demodulation device 4 performs RS decoding of the demodulated data to correct the error (step S12). After that, the presence or absence of an error is determined by the CRC code (step S13).

At this time, if possible correction is made, an error of 2 bytes or less can be corrected for one block. In addition, the modulation / demodulation device 4 includes: The root of the error locator polynomial cannot be obtained b. When an error position is irrational when the error position is obtained, it is determined that an error of 3 bytes or more has occurred (step S14), and a retransmission request is made to the transmitting side (step S15).

When the error is 2 bytes or less in step S14, the modulation / demodulation device 4 notifies the receiving side terminal of step S12.
The error-corrected data is output in step S1 (step S1).
6). As a result, one packet of normal data is output. Then, when the modem device 4 receives all the data (step S17), the reception process relating to the data transmission is ended.

When performing these reception processes, the modulator / demodulator 4
The error control unit 4A performs the processing shown in FIGS. The error control unit 4A is provided with a flag f and a variable k is set. When the flag f is “0”, it represents a state where RS coding is performed, and when the flag f is “1”, it represents a state where RS coding is not performed. Further, the variable k is for indicating the number of packets that are continuously and normally received.

The error control unit 4A sets the flag f to "0" to indicate that the RS coding is performed (step S2).
1). In addition, the error control unit 4A sets the variable k to k = 0, which indicates that there is no packet that is continuously and normally received (step S22). If the reception has not ended (step S23), the power level from the wireless device 3 is equal to or higher than a predetermined value (step S24), and no error has occurred in the received packet (step S2).
5), the error control unit 4A sets the variable k to k = k + 1 (step S26).

After this, the error control unit 4A determines in step S2.
When 3 to S26 are repeated and the variable k becomes k = p, that is, when p packets are continuously and normally received (step S27), the flag f is "0".
In this case (step S28), the error control unit 4A transmits a notification that RS coding is unnecessary to the receiving side via the wireless device 3 (step S29). The value p is preset to a value such that the characteristics of the wireless data transmission line are good and no error occurs. The value p is set in consideration of various conditions.

After step S29, the error controller 4A
The flag f is set to "1", and the RS coding is not performed (step S30). Then, the process is step S
Return to 22. That is, when the power level is equal to or higher than the predetermined value and no error has occurred, the flag f is set to "1" and the detection operation is repeated. If all the data has been received in step S23, the process ends.

On the other hand, when the power level is less than the predetermined value in step S24 or when there is an error in step S25, the error control unit 4A checks whether the flag f is "1" (step S31). When the flag is "1" and RS coding is not performed, a notification for RS coding is transmitted to the transmission side via the wireless device 3 (step S32).

After step S32, the error controller 4A
The flag f is set to "0", and RS coding is performed (step S33). Then, the process proceeds to step S2
Return to 2.

That is, when p packets are not consecutive,
The flag f is kept at "0" and the detection operation is repeated. At this time, the variable k is set to k = 0.

As described above, according to this embodiment, in the data communication, the power level is equal to or higher than the predetermined value, and
When p packets are normally received, the receiving side estimates that an error hardly occurs, and notifies the transmitting side that RS coding is unnecessary. This simplifies the processing and shortens the packet length, thus improving the data transmission efficiency and throughput and enabling high-speed communication.

In this embodiment, whether or not RS coding is performed is switched at any time during data transmission. Other than this, there are the following methods. Whether or not an error occurs at the start of data transmission is detected, and based on the detection result, whether or not to add an RS code to the data to be transmitted is determined. Then, this state is not changed during communication.

According to this method, it is only necessary to detect an error at the start of communication, so that the processing can be lightened.

The following method is also available. In this example,
When one error occurs, the receiving side notifies the transmitting side of the addition of the RS code. However, the present invention is not limited to this, and the addition of the RS code may be notified to the transmitting side when a plurality of errors occur.

Further, there is the following method. In the process on the receiving side (process in FIG. 3), the flag f in step S21 is set to "1". That is, when it is estimated that the transmission characteristics are good, the receiving side instructs the transmitting side not to use RS coding.
Then, when it is detected that the transmission characteristic is poor, RS coding is performed.

According to this method, in data transmission, when the transmission characteristic is good, the packet length can be shortened from the start of communication.

In this embodiment, the receiving side detects the power level, but this detection may be omitted. This can simplify the process.

Further, in this embodiment, byte-unit data transmission is performed, and the RS code is used as the error correction code.
Although the CRC code is used as the error detection code, the invention is not limited to this. For example, data may be transmitted bit by bit and the BCH code may be used as the error correction code.

[0051]

As described above, according to the first aspect of the present invention, the receiving side does not need redundant data for error correction when a predetermined number of received packets are continuously normal. Is sent to the sender. Upon receiving the notification from the receiving side, the transmitting side transmits the data according to the notification without adding the redundant data.

As a result, the receiving side has only to decide whether or not to add redundant data for error correction, so that the processing can be simplified as compared with the conventional case.

Further, since the packet length is shortened when no error occurs, the data transmission efficiency and throughput can be improved, and high speed communication becomes possible.

In the second aspect of the invention, when the receiving side detects an error, the receiving side transmits a notification of addition of redundant data for error correction to the transmitting side. The transmitting side, in response to the notification from the receiving side, blocks the transmission data to which the redundant data for error detection is added, adds the redundant data for error correction to each block, and converts the plurality of blocked data into one. Send as a packet.

As a result, when the data transmission is normal, the data transmission is continued without adding the error correction redundant data. As a result, the processing related to data transmission can be simplified as compared with the conventional one, and high-speed communication becomes possible.

Further, when the data transmission is normal, the data length can be shortened from the start of the communication, so that the data transmission efficiency and the throughput can be improved and the high-speed communication can be realized similarly to the first aspect. It will be possible.

[Brief description of drawings]

FIG. 1 is a flowchart showing processing on the transmission side according to the present invention.

FIG. 2 is a flowchart showing processing on the receiving side according to the present invention.

FIG. 3 is a flowchart showing processing on the receiving side according to the present invention.

FIG. 4 is a flowchart showing processing on the receiving side according to the present invention.

FIG. 5 is a schematic diagram of a system for implementing the invention.

FIG. 6 is a diagram showing a wireless LAN.

FIG. 7 is a diagram showing a format of data to be transmitted.

FIG. 8 is a diagram showing a format of transmitted data.

[Explanation of symbols]

 Steps S1 to S7 processing steps

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04L 29/08

Claims (2)

[Claims] 1. A data transmission method in which a reception side receives data from a transmission side via a wireless data transmission path, wherein the transmission side adds redundant data for error detection to the data to be transmitted, The data added with is divided into blocks, redundant data for error correction is added to each block, and a plurality of blocks of data is transmitted as one packet. At the receiving side, a predetermined number of consecutive packets are received. When the packet is normal, redundant notification for error correction is sent to the sending side, and when the receiving side receives the notification from the receiving side, the sending side removes redundant data for error correction according to this notification. A data transmission method characterized by transmitting data. 2. A data transmission method in which a reception side receives data from a transmission side via a wireless data transmission line, wherein the transmission side adds redundant data for error detection to the data to be transmitted. When an error is detected in the received data, the receiving side sends a notification of the addition of redundant data for error correction to the sending side, and the sending side receives the notification from the receiving side and The data transmission method is characterized in that the data to which the redundant data is added is divided into blocks, redundant data for error correction is added to each block, and a plurality of the blocked data is transmitted as one packet.