JP2004328586A - Data transmission device, data reception device, and data transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reproduce video with high quality while maintaining high throughput even in the environment of much noise such as in a wireless network. <P>SOLUTION: In a data transmission system for storing input data in a data frame of a predetermined structure and transmitting the data via the wireless network, the data are transmitted while adding a significant data flag indicating whether or not the input data contain significant data and a parity bit for error detection to the data frame and when it is detected on the basis of the significant data flag and the bit for error detection that an error is present in the received data frame and that the input data stored in the received data frame contain the significant data, the data frame is retransmitted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data transmission device, a data reception device, and a data transmission method suitable for transmitting data via a wireless network.
[0002]
[Prior art]
In a wireless network using a wireless transmission path as a communication medium, a transmission error may occur in a data frame composed of a packet sequence. In a wireless network defined by the standard IEEE 802.11a, an error detection code is added to a data frame on a transmission device side, and a transmission error of a data frame received using the error detection code is detected on a reception device side, If there is a transmission error, a request for retransmission of the data frame is made to the transmitting device. The transmitting device responds to the retransmission request and retransmits the data frame to the receiving device. By this series of operations, transmission errors are repaired.
[0003]
More specifically, when the receiving device has an error in the received data frame, the receiving device does not transmit an ACK (Acknowledge) frame to the transmitting device, thereby causing the transmitting device to time out receiving the ACK frame. When the transmission timeout of the ACK frame occurs, the transmitting device determines that the data frame has not been correctly transmitted to the receiving side, and retransmits the data frame having the same content after a predetermined time has elapsed.
[0004]
However, the reception timeout time EIFS (Extended Interframe Space) of the ACK frame defined by IEEE802.11a is relatively long. Therefore, if the retransmission of the same data frame is repeated many times, the effective throughput is greatly reduced and the video data In the case of transmission, there is a problem that the real-time property of video is not ensured.
[0005]
To cope with this, when transmitting video data via a wireless network, the transmitting side counts the number of times a retransmission request accompanied by a transmission error is notified from the receiving side, and if the number exceeds a predetermined number, A configuration is known in which retransmission is stopped and the next video data is transmitted (for example, see Patent Document 1). This prevents the transmission time of one image from becoming excessively long by re-transmitting the transmission many times when a transmission error occurs, and transmits the video data over a noisy transmission line such as a wireless network. Even in such a case, the real-time property of the video is ensured.
[0006]
[Patent Document 1]
JP-A-10-262256
[0007]
[Problems to be solved by the invention]
When decoding the received video data and reproducing the video, even if there is an error in the received data, the effect on the reproduced image greatly depends on the content of the data in which the error has occurred. For example, when an error occurs in a part of the picture data (pixel data) that constitutes the video itself, it is often the case that only block noise is generated, and the image quality is relatively small. When an error occurs in data including information, it is often impossible to reproduce a group of pictures decoded using a common parameter included in the same header information, and the image quality is greatly reduced.
[0008]
In the configuration described in Patent Document 1, regardless of the content and importance of video data, retransmissions that have been retransmitted a predetermined number of times uniformly stop retransmission, so that video data is transmitted via a wireless network. In an environment with a lot of noise, retransmission of important data such as header information is stopped, and as a result, there is a possibility that the reproduction quality is significantly reduced.
[0009]
The present invention has been made in view of such a problem, and by transmitting important data without errors while maintaining high throughput, video can be reproduced with high quality even in a noisy environment such as a wireless network. The purpose is to.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a data transmitting device of the present invention includes a transmitting unit that stores input data in a data frame having a predetermined structure and transmits the data to a data receiving device, and determines whether the input data includes important data. Important data detecting means for detecting the data frame, wherein the transmitting means adds an important data flag having a value corresponding to a detection result of the important data detecting means and an error detection parity bit to the data frame. And
[0011]
In order to achieve the above object, a data receiving apparatus of the present invention receives a data frame storing input data in a predetermined structure from a data transmitting apparatus and extracts the input data from the data frame; Error detection means for detecting whether or not an error exists in the received data frame based on the error detection bit added to the data frame, and extracted based on the important data flag added to the data frame. Important data detecting means for detecting whether or not the input data contains important data; and detecting that the received data frame has an error by the error detecting means, and extracting the error from the detected data frame. When the important data detecting means detects that important data is included in the input data, Characterized in that it comprises a retransmission request means for requesting retransmission to the data transmission device.
[0012]
In order to achieve the above object, a data transmission method of the present invention in which input data is stored in a data frame having a predetermined structure and transmitted via a wireless network, is an important data indicating whether or not the input data includes important data. A data flag and a parity bit for error detection are added to the data frame and transmitted. An error exists in the received data frame, and important data is included in input data stored in the received data frame. Is retransmitted when a data frame is detected based on the important data flag and the error detection bit.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
One specific example of the data transmission device of the present invention will be described below. As shown in FIG. 1, a data transmission device 10 of the present invention includes an MPEG data input unit 11, a data frame generation unit 12, an important data detection unit 13, and a wireless transmission control unit 14, and includes an MPEG-input unit 11 Based on data (hereinafter, referred to as MPEG data) according to the TS format, a MAC (Media Access Control) frame (hereinafter, referred to as a data frame) according to the wireless network standard IEEE802.11a is generated, and a data receiving device (not shown) is generated via the wireless network. Send to
[0014]
FIG. 2 shows a structure of a data frame generated by the data transmission device 10. This data frame is based on a data frame defined in the wireless network standard IEEE 802.11a and is an extension of the data frame. As shown in the figure, this data frame stores a Frame Control field for specifying a frame type and the like, a MAC header 21 including an Address field for specifying a source address and a destination address, and the like, and the data to be transmitted itself. A Frame Body field 23, an important data flag 22 indicating whether the data stored in the Frame Body field 23 is important data, and an error detection parity bit for detecting a transmission error of the data frame are stored. It comprises an FCS (Frame Check Sequence) field 24.
[0015]
The MPEG data input unit 11 takes in MPEG data from an external device and sends it to the data frame generation unit 12. The data frame generation unit 12 stores the MPEG data sent from the MPEG data input unit 11 in the Frame Body field 23, sets the important data flag 22 based on the detection result of the important data detection unit 13, and further sets By setting the FCS field 24 for storing the parity bits, a data frame having the above structure is generated.
[0016]
The MPEG data input to the MPEG data input unit 11 is composed of a sequence of TS packets as shown in FIG. As shown in the figure, a TS packet 31 includes a transport error indicator (hereinafter, referred to as TEI) 32 that indicates whether there is an error in the TS packet, and a type of data (video Stream, audio stream, data stream, various information tables, etc.), a PID (Packet Identifier) 33, a program, a video stream or an audio stream, or a payload 34 in which table information described below is stored. Including.
[0017]
A plurality of streams (a video stream, an audio stream, a data stream, etc.) constituting one program are multiplexed on the MPEG data and transmitted as one TS (Transport Stream). Further, a plurality of programs may be multiplexed into one TS. Each stream is composed of a packet sequence having the above structure, and a different PID is assigned to each stream. In order to describe the relationship between a large number of PIDs and contents, the TS includes table information such as a PAT (Program Association Table) and a PMT (Program Map Table) indicating PID values of a plurality of streams constituting a program. ing. The PAT and PMT are stored in a TS packet having a PID value of 0. A target stream, for example, a video stream can be extracted by extracting packets by performing PID filtering with reference to the table information on the receiving side.
[0018]
The structure of the video stream will be described with reference to FIG. The video stream includes an I picture 404 which is an intra-coded image, a P picture 405 in which inter-frame forward prediction and encoding are performed based on the I picture, and bidirectional prediction and encoding based on the I picture and the P picture. B picture 406 to be performed. In front of each picture, there is a picture header 43 for storing header information necessary for reproducing the picture. In addition, a GOP header 42 including header information necessary for editing the group of pictures and the like exists before the screen group including a group of pictures constituting the minimum unit of random access. Further, a sequence header 41 for storing common attribute information (header information) exists before a screen sequence including a plurality of screen groups having the same attribute (image size and image rate).
[0019]
In the sequence header, GOP header, and picture header, start codes for identifying respective start positions are defined. Specifically, a sequence header code (Sequence Header Code) which is 32-bit data (0x represents hexadecimal notation) having a value of 0x000001B3 exists at the beginning of the sequence header, and exists at the beginning of the GOP header. A GOP start code (GOP Start Code), which is 32-bit data having a value of 0x000001B8, is present, and a picture start code (Picture Start Code), which is 32-bit data having a value of 0x00000100, is present at the head of the picture header.
[0020]
The important data detecting unit 13 searches the extracted video stream for the start code to check whether header information as important data exists, and notifies the data frame generating unit 12 of the result.
[0021]
The operation of the important data detection unit 13 detecting important data will be described more specifically with reference to the flowchart of FIG.
The important data detection unit 13 searches for a PAT (that is, a TS packet with a PID value of 0) from the data frame sent from the data frame generation unit 12 (step S501). If it is determined that the PAT does not exist, the process proceeds to step S507, and notifies the data frame generation unit 12 that important data is not included. If it is determined in step S501 that the PAT is included, the PMT is further searched (step S502). If it is determined that the PMT does not exist, the process proceeds to step S507, and the data frame generating unit 12 is notified that important data is not included.
[0022]
If it is determined in step S502 that a PMT is included, a video stream is further searched (step S503). If it is determined that there is no video stream, the process advances to step S507 to notify the data frame generation unit 12 that important data is not included. If it is determined in step S503 that a video stream is included, a header code is extracted from the video stream (step S504).
[0023]
Next, a header code is searched from the extracted video stream (step S505). If it is determined that the header code is not included, the process advances to step S507 to notify the data frame generation unit 12 that important data is not included. If it is determined that the header code exists, the data frame generation unit 12 is notified that important data is included (step S506).
[0024]
The data frame generation unit 12 sets the important data flag 22 of the data frame based on the detection result notified from the important data detection unit 13. In the present embodiment, the important data flag is set when at least one of the sequence header, the GOP header, and the picture header exists. However, the present invention is not limited to this. It is also possible to set the important data flag only when performing the operation.
[0025]
The data frame generation unit 12 also performs a CRC (Cyclic Redundancy Check) operation on the MAC header 21, the important data flag 22, and the Frame Body field 23, and stores a parity bit for detecting a data frame transmission error according to the operation result. The FCS field 24 to be set is set. The data frame generated as described above is sent to the wireless transmission control unit 14.
[0026]
The wireless transmission control unit 14 transmits the data frame transmitted from the data frame generation unit 12 to the data receiving device via a wireless network.
FIG. 6 is a flowchart illustrating the transmission operation of the data transmission device described above. As shown in the figure, MPEG data input from an external device is cut out to a fixed size (step S601), a data frame is generated, and an important data flag is set (step S602). Further, an error detection parity bit is set (step S603) and transmitted as a wireless packet (step S605). After the transmission, if the ACK frame is received, the transmission operation is terminated. However, if the ACK frame is not received after a certain period of time after the transmission, the wireless packet is transmitted again (step S605).
[0027]
Next, a specific example of the data receiving apparatus of the present invention will be described below. As shown in FIG. 7, the data receiving device 70 of the present invention includes a wireless reception control unit 71, a data frame analysis unit 72, an error detection unit 73, a header detection unit 74, a retransmission determination unit 75, and an MPEG data output unit 74. The data frame transmitted by the data transmitting apparatus having the configuration shown in FIG. 1 is received via a wireless network, and MPEG data is extracted and output to an external device.
[0028]
The data frame analysis unit 72 sends the data frame received by the wireless reception control unit 71 via the wireless network to the error detection unit 73 and the header detection unit 74. The MPEG data output unit 76 outputs the MPEG data sent from the data frame analysis unit 72 to an external device. The data frame analysis unit 72 also sends the MPEG data included in the received data frame to the MPEG data output unit 76 or discards it based on the retransmission determination result notified from the retransmission determination unit 75. The error detection unit 73 performs an error detection process on the data frame in which the error detection parity bit is stored in the FCS field to check whether the data frame has an error, and sends the result to the retransmission determination unit 75. Notice.
[0029]
The header detection unit 74 determines whether or not important data is stored in the Frame Body field of the data frame based on the important data flag, and notifies the retransmission determination unit 75 of the result. The retransmission determination unit 75 determines whether or not to request retransmission of the received data frame based on the determination results notified from the error detection unit 73 and the header detection unit 74, and as a retransmission determination result, the wireless reception control unit 71 And the data frame analysis unit 72.
[0030]
The operation of the data receiving apparatus having the above configuration when receiving a data frame is one of the following three patterns.
[0031]
Pattern 1.
When receiving from the error detection unit 73 that the received data frame has no error detected, the retransmission determination unit 75 determines that retransmission is unnecessary regardless of the result notified from the header detection unit 74. Then, the determination result is notified to the data frame analysis unit 72. Upon receiving the notification that retransmission is unnecessary, the data frame analysis unit 72 extracts MPEG data from the Frame Body field of the data frame, and sends the extracted MPEG data to the MPEG data output unit 76. The MPEG data output unit 76 outputs the MPEG data sent from the data frame analysis unit 72 to an external device. At this time, the wireless reception control unit 71 transmits an ACK frame to the data transmission device when a predetermined time has elapsed from the time when the data frame was received.
[0032]
Pattern 2.
The retransmission determination unit 75 receives a notification from the error detection unit 73 that an error has been detected in the data frame received, and receives a notification from the header detection unit 74 that this data frame contains important data. , It is determined that retransmission is necessary, the determination result is notified to the data frame analysis unit 72, and the wireless reception control unit 71 is instructed to make a retransmission request. Upon receiving the notification that the retransmission is necessary, the data frame analysis unit 72 discards the received data frame.
On the other hand, the radio reception control unit 71 that has received the instruction to perform the retransmission request does not transmit the ACK frame even if a predetermined time has elapsed from the time at which the data frame was received, and accordingly, the data transmission apparatus transmits the ACK frame. Generate a reception timeout. As a result, the data transmitting apparatus determines that a transmission error has occurred in the transmitted data frame and that retransmission has been requested, and retransmits the data frame storing the same MPEG data.
[0033]
Pattern 3.
Even when the retransmission determination unit 75 receives a notification from the error detection unit 73 that an error has been detected in the received data frame, the header detection unit 74 determines that the data frame does not contain important data. When the notification is received, it is determined that retransmission is unnecessary, and the determination result is notified to the data frame analysis unit 72. Upon receiving the notification that the retransmission is unnecessary, the data frame analysis unit 72 extracts the MPEG data from the data frame, sets the TEI (Transport Error Indicator) of the TS packet containing the error, and then outputs the MPEG data. Send to section 76. The MPEG data output unit 76 outputs the MPEG data sent from the data frame analysis unit 72 to an external device. At this time, the wireless reception control unit 71 transmits an ACK frame to the data transmission device when a predetermined time has elapsed from the time when the data frame was received.
[0034]
FIG. 8 is a flowchart illustrating the receiving operation of the data receiving device described above. As shown in the drawing, when a data frame is received (step S801), it is checked whether or not the data frame has an error (step S802). If no error is detected, the process advances to step S807 to transmit an ACK frame and end the receiving operation. When an error is detected, it is checked whether or not the packet stored in the data frame contains important data based on the important data flag included in the data frame (step S803). If it is determined that no important data is included, TEI is set (step S806), and the process proceeds to step S807 to transmit an ACK frame and end the receiving operation. If it is determined in step S803 that important data is included, retransmission is requested (step S804), and the received packet is discarded (step S805).
[0035]
Next, a specific example of a data transmission operation in a data transmission system in which the data transmission device having the configuration shown in FIG. 1 and the data reception device having the configuration shown in FIG. 7 are connected via a wireless network will be described below. .
[0036]
FIG. 9 is a communication sequence diagram of the transmission system when data transmission is normally performed without error. As shown in this figure, the data transmitting apparatus transmits frame data 91 storing MPEG data to the data receiving apparatus. After receiving the data frame 91, the data receiving device checks whether or not the data frame 91 has a transmission error by using the parity bit for error detection set in the FCS field in the data frame 91. When the data receiving device determines that there is no transmission error in the data frame 91, the data receiving device transmits an ACK frame 92 to the data transmitting device when a predetermined time has elapsed from the reception time of the data frame 91.
[0037]
FIG. 10 is a communication sequence diagram of the transmission system when a transmission error occurs. The data transmitting device transmits the data frame 101a storing the MPEG data to the data receiving device. When the data receiving apparatus receives the data frame 101a, the data receiving apparatus checks whether or not there is a transmission error in the data frame 101a using the parity bit for error detection stored in the FCS field 14 and sets the important data flag. Based on the stored value, it is checked whether or not important data is included in the MPEG data stored in the Frame Body field.
If the receiving apparatus determines that a transmission error exists in the data frame 101a and that the data frame 101a contains important data, the receiving apparatus does not transmit the ACK frame even if a predetermined time has elapsed from the reception time of the data frame 101a. , The transmission device generates an ACK frame reception timeout.
[0038]
Due to the reception timeout of the ACK frame, the transmitting device determines that the data frame 101a could not be transmitted normally, and transmits a data frame 101b storing the same MPEG data as the MPEG data stored in the data frame 101a after a predetermined time. . When the data receiving apparatus that has received the data frame 101b determines that there is no transmission error in the data frame 101b, the data receiving apparatus transmits an ACK frame 102 to the data transmitting apparatus when a predetermined time has elapsed from the reception time of the data frame 101b. .
[0039]
Although the data frame 101b is a retransmission frame of the data frame 101a, they are not completely the same frame. For example, the value of the Retry field in the Sequence Control field of the MAC header shown in FIG. 2 is different. The Retry flag is a flag indicating that the frame is a retransmission data frame, and is set to a value "0" in the data frame 101a, but is set to a value "1" in the data frame 101b to be retransmitted. According to the above-described communication sequence, when a transmission error occurs in a data frame, the data frame is retransmitted only when important data is included, and the transmission error is restored.
[0040]
Embodiment 2 FIG.
Hereinafter, a method for transmitting data using a data frame having a different structure from the data frame used in the first embodiment will be described as a second embodiment. The data transmitting device and the data receiving device used in the second embodiment are the same as those used in the first embodiment.
[0041]
As shown in FIG. 2, the data frame generated by the data transmitting apparatus 10 according to the first embodiment newly includes a field for storing an important data flag in the header of the data frame defined by the wireless network standard IEEE 802.11a. Therefore, the structure is slightly different from that specified in IEEE802.11a.
[0042]
FIG. 11 shows the structure of a data frame used in the second embodiment. As shown in the drawing, in this data frame, the important data flag 112 is incorporated in a frame body field 113. Since the provisions of the wireless network standard IEEE802.11a are not applied to the data inside the frame body field 113, the user and the application can freely configure the data. That is, by incorporating the important data flag 112 in the Frame Body field, the important data flag can be transmitted as a part of the data. According to the second embodiment, data transmission can be performed using a data frame having a structure conforming to the wireless network standard IEEE 802.11a.
[0043]
In FIG. 11, the important data flag 112 is located at the head of the frame body field 113, but is not limited to this, and may be located at any position as long as it is incorporated in the frame body field 113. be able to.
[0044]
Embodiment 3 FIG.
Hereinafter, a method of performing data transmission using a data frame different from those of the first and second embodiments will be described as a third embodiment. The data transmitting device and the data receiving device used in the third embodiment are the same as those used in the first embodiment.
[0045]
In the data frame used in the second embodiment, since the important data flag 112 is incorporated in the frame body field 113 as shown in FIG. 11, the data receiving device 70 shown in FIG. 7 receives this data frame. In this case, the important data flag 112 cannot be detected by the header detection unit 74 alone, and the Frame Body field 113 must be analyzed.
[0046]
The data receiving apparatus must transmit an ACK frame to the data transmitting apparatus within a predetermined time after receiving data when not performing a retransmission request, but the time SISF (Short Interframe Space) defined by IEEE 802.11a is It is short, and it is difficult to analyze the Frame Body field 113 of the data received within this time, determine the importance of the data, and determine whether to make a retransmission request.
[0047]
FIG. 12 shows the structure of a data frame used in the third embodiment. In the figure, the values of the Type field 124 (2 bits) and the Sub Type field 125 (4 bits) in the Frame Control field 121 are fields for identifying the type of data stored in the Frame Body field 122. is there.
[0048]
FIG. 13 is a table showing main combinations of the values of the Type field 124 and the Sub Type field 125. From this table, for example, when “10” is set in the Type field and “0000” is set in the Sub Type field, it can be determined that data is stored in the Frame Body field.
[0049]
As shown in the table of FIG. 13, when the value of the Type field is “10”, the range of the value of the Sub Type field from “1000” to “1111” is defined as “Reserved”. Therefore, as shown in FIG. 12, when the value of the type field 124 is “10” and the value of the sub type field 125 is “1000”, if important data is included in the frame body field 122, it is newly added. By defining, it becomes possible to inform the data receiving apparatus of the importance of the transmission data using a data frame having a structure conforming to the definition of the wireless network standard IEEE 802.11a.
[0050]
Since the data receiving apparatus can determine the importance of the received data only by analyzing the header part without analyzing the Frame Body field 122, it is possible to easily determine whether to make a retransmission request within the SISF time. .
[0051]
In FIG. 12, when important data is included in the data stored in the Frame Body field, “10” is set in the Type field 124 and “1000” is set in the Sub Type field 125. However, the present invention is not limited to this, and any combination defined as “Reserved” in the combinations shown in FIG. 13 can be used.
[0052]
【The invention's effect】
According to the present invention, when a transmission error occurs in a data frame, the data frame is retransmitted only when important data such as header information is included, so even in a noisy environment such as a wireless network. Video can be reproduced with high quality while maintaining high throughput.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a specific example of a data transmission device of the present invention.
FIG. 2 is a diagram illustrating a MAC frame (data frame) structure according to the IEEE 802.11a standard.
FIG. 3 is a diagram showing the structure of MPEG data according to the MPEG-TS format.
FIG. 4 is a diagram showing the structure of a video stream included in MPEG data.
FIG. 5 is a flowchart illustrating an operation of detecting important data by the data transmitting apparatus of FIG. 1;
FIG. 6 is a flowchart illustrating a data transmission operation of the data transmission device of FIG. 1;
FIG. 7 is a diagram showing a configuration of a specific example of a data receiving device of the present invention.
FIG. 8 is a flowchart illustrating a data receiving operation of the data receiving device of FIG. 7;
9 is a communication sequence diagram in a data transmission system including the data transmission device of FIG. 1 and the data reception device of FIG. 7 when data transmission is normally performed without errors.
FIG. 10 is a communication sequence diagram when an error occurs in transmission data in a data transmission system including the data transmission device of FIG. 1 and the data reception device of FIG. 7;
FIG. 11 is a diagram showing a structure of a data frame used in the data transmission method of the present invention.
FIG. 12 is a diagram showing the structure of a data frame used in the data transmission method of the present invention.
FIG. 13 is a table showing main combinations of a Type field and a Sub Type field defined in the IEEE 802.11a standard.
[Explanation of symbols]
Reference Signs List 10 data transmission device, 11 MPEG data input unit, 12 data frame generation unit, 13 important data detection unit, 14 radio transmission control unit, 70 data reception device, 71 radio reception control unit, 72 data frame analysis unit, 73 error detection unit 74 a header detection unit; 75 a retransmission determination unit; 76 an MPEG data output unit.

Claims (8)

Transmitting means for storing input data in a data frame having a predetermined structure and transmitting the data to a data receiving device;
With important data detection means for detecting whether the input data contains important data,
The data transmission device, wherein the transmission unit adds an important data flag having a value according to a detection result of the important data detection unit and an error detection parity bit to the data frame. The data transmission device according to claim 1, wherein the data frame is retransmitted in response to a retransmission request from the data reception device. 3. The data transmitting apparatus according to claim 1, wherein the input data is data conforming to an MPEG-TS format, and the important data detecting unit detects whether the input data includes header information. . The data transmission device according to claim 3, wherein the header information is at least one of a sequence header, a GOP header, and a picture header. Receiving means for receiving a data frame storing input data in a predetermined structure from a data transmitting device, and extracting the input data from the data frame;
Error detection means for detecting whether an error exists in the received data frame based on the error detection bit added to the data frame,
Important data detection means for detecting whether or not important data is included in the extracted input data, based on the important data flag added to the data frame,
The error detection unit detects that the received data frame has an error, and the important data detection unit detects that important data is included in input data extracted from the data frame where the error is detected. And a retransmission request unit for requesting the data transmission device to retransmit the data frame in the case. In a data transmission method of storing input data in a data frame having a predetermined structure and transmitting the data through a wireless network,
An important data flag indicating whether the input data contains important data and an error detection parity bit are added to the data frame and transmitted,
An error is detected in the received data frame, and the data is detected based on the important data flag and the error detection bit, indicating that the input data stored in the received data frame contains important data. A data transmission method comprising retransmitting a frame. The input data is data conforming to the MPEG-TS format, and the important data flag indicates that there is an error in the received data frame and that the input data stored in the received data frame includes header information. 7. The data transmission method according to claim 6, wherein a data frame is retransmitted when the data frame is detected based on the error detection bits. The method according to claim 7, wherein the header information is at least one of a sequence header, a GOP header, and a picture header.

Images