JP2006020130A - Data transmission system and method, data transmission device, data reception device, and its computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved data transmission system and its method capable of keeping real time characteristics in data reproduction, with no change in data transmission efficiency, even if transmission error of packets occurs. <P>SOLUTION: A data transmission device 210 comprises an interruption process means 266 which, if a prescribed second time or more is consumed for packet transmission, interrupts re-transmission of a packet and instructs a data reception device to interrupt re-transmission by a specified process. The data reception device 220 comprises a data process means 360 for processing data while a packet is missed according to the specified process in the data transmission device. With this configuration, real time property in data reproduction is maintained without changing data transmission efficiency, even if transmission error of packets occurs. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a data transmission system and method, a data transmission device, a data reception device, and a computer program therefor.

  As an example of a standard regarding a wireless network, the Institute of Electronic Engineers of the United States (IEEE) (The Institute of Electrical and Engineering Engineers) 802.11, HiperLAN / 2, IEEE 302.15.3, Bluetooth, and the like can be given.

  The IEEE802.11 standard includes various wireless communication protocols such as the IEEE802.11a standard and the IEEE802.11b standard depending on the wireless communication method and the frequency band to be used.

  In such a known wireless communication protocol, a data sequence is divided into packets on the data transmission side, and data transmission is performed using such packets as transmission units. In order to recognize whether the above communication is normally performed, the data receiving side transmits a reception completion signal (ACK) to the transmitting side in response to the reception of the packet, and the transmitting side receives the response and receives the packet. Confirming that the transmission was performed reliably. Further, when the reception completion signal (ACK) is not confirmed, it is considered that the packet has not been correctly transmitted, and a process of retransmitting the packet has been performed.

  However, when there is no response to the reception completion signal (ACK), the same packet is retransmitted many times. During this time, the next packet cannot be transmitted and data transmission does not proceed.

  In order to solve this problem, in a communication protocol such as IEEE802.11e, a plurality of packets are transmitted without waiting for a reception completion signal (ACK) on the transmission side, and a response of a reception completion signal (ACK) is collectively collected later. A method such as group ACK is used to determine whether or not there is. However, this technique also does not change the situation in which the data transmission rate changes depending on the communication status because the retransmission is performed many times for the packet for which the ACK is not returned.

  There is also known a data transmission technique that reduces the expected number of errors by finely dividing a packet that needs to be retransmitted and repeatedly transmitting the divided packet (for example, Patent Document 1). However, this transmission technique is also intended for perfect data communication, and packet division is repeated until the packet is completely transmitted.

JP 2004-40493 A

  For example, when taking up media such as a DVD (Digital Versatile Disk), real-time performance is required for playback of video data with the highest priority, and even if there is some image disturbance than displaying a complete video with no errors. A video with no delay is required. That is, rather than filling in the lost packets over time, it is possible to leave them missing, so it is a problem to perform data communication that does not affect the flow of moving image playback.

  The present invention has been made in view of the above problems of the conventional data transmission system, and the object of the present invention is to perform data reproduction without changing the data transmission efficiency even if there is a packet transmission error. To provide a new and improved data transmission system and method, a data transmission device, a data reception device, and a computer program thereof that can maintain real-time performance.

  In order to solve the above-described problem, according to a first aspect of the present invention, data transmission is performed by dividing data into a plurality of packets, assigning unique sequence numbers to the packets, and transmitting the packets according to the sequence numbers. Receiving the packet transmitted from the device and the data transmitting device, transmitting a reception completion signal to the data transmitting device, receiving a predetermined number of packet groups arranged in order of the sequence number, and then transmitting the packet group to the data In a data transmission system comprising: a data receiving device that decodes the data and starts processing the data: the data transmitting device retransmits a packet with a sequence number that does not receive a reception completion signal at a predetermined first time interval A packet retransmission unit; stopping retransmission of a packet with a sequence number that does not receive the reception completion signal within a predetermined second time period; And a cancellation processing means for performing a predetermined process indicating cancellation of retransmission, wherein the data receiving device performs predetermined data processing in a state where the predetermined number of packet groups are not aligned in accordance with the predetermined process. And a data processing system for performing the data transmission. Such a data transmission system may be intended for packet transmission by wireless communication.

  The data transmitting apparatus includes: a sequence adding unit that divides data into a plurality of packets and assigns unique sequence numbers; a transmission determining unit that determines a transmission order of the packets according to the sequence numbers; A packet transmitting means for transmitting packets to the data receiving apparatus in accordance with a transmission order; a counting means for counting the elapsed time since the packet was first transmitted for each packet; a reception completion signal received from the data receiving apparatus A count stop means for stopping the counting of packets corresponding to the above; a packet retransmission means for retransmitting a packet having a sequence number not receiving a reception completion signal at a predetermined first time interval using the count means; Stop retransmission of packets with sequence numbers that do not receive the above reception completion signal within the second time , A cancellation processing unit that performs a predetermined process indicating cancellation of retransmission, and the data reception device includes a packet reception unit that receives a packet transmitted from the data transmission device; In response, a reception response means for transmitting a reception completion signal to the data transmission device; a process of receiving a predetermined number of packet groups arranged in sequence number order, and then decoding the packet groups into data and starting processing of the data Start means; and data processing means for performing predetermined data processing in a state in which the predetermined number of packet groups are not arranged in accordance with predetermined processing in the data transmission device.

  The data transmitting device and the data receiving device include a personal computer, a PDA (Personal Digital Assistant), a mobile phone, a video conference system, and a communication device that is built in or connected to these devices.

  The present invention stops (abortions) further retransmission of a packet that has been retransmitted to some extent in the data transmission device, and the data reception device does not have a complete packet group (missing). However, it is characterized by data processing. In addition, as shown below, the data receiving device can easily determine that the retransmission of the packet has been stopped at the data transmitting device, and synchronization between valid data and invalid data can be ensured in both devices. Is possible. That is, data invalidated by the data transmitting apparatus is treated as invalid data also by the data receiving apparatus, and data validated by the data transmitting apparatus is treated as valid data by the data receiving apparatus without making an erroneous determination. In addition, the memory capacity for data retransmission can be reduced by canceling such retransmission.

  The fact that the above data transmission device cancels (abortions) retransmission of a packet gives priority to the real-time property of data processing on the data receiving device side over reliable transmission of the packet. It can be considered that it is intentionally transmitted to the data receiving device.

  The data receiving apparatus that has received such transmission processes data that does not have such a packet group, and resumes normal communication while maintaining synchronization with the data transmitting apparatus. At this time, the data processing means may abandon data that does not have such a packet group, or may perform some processing using the remaining packets (packets in a missing state).

  The sequence number is a number assigned to determine the order in which data including a data string is divided into a plurality of packets and then transmitted. Here, it is said that the packet re-transmission means interrupts the packet re-transmission in the past, and the packet transmission means transmits the packets in the order of the sequence number by the packet transmission means. Because there is no limit. Such a sequence number is given by incrementing a certain value (for example, 1). In the data receiving apparatus, a predetermined number of packet groups are arranged in the order of the sequence numbers and decoded into data. Therefore, even if the order of packets received by the data receiving device changes, it can be reliably restored to data by rearranging the sequence numbers in ascending or descending order. Even when the same packet is received twice by the data receiving device, decoding to correct data is executed by the sequence number.

  The first time indicates a packet retransmission interval, and the second time indicates an expiration date until the packet retransmission is stopped (abandoned). Both times can be arbitrarily set according to the usage of data. Usually, the second time is longer than the first time and can be an integer multiple of the first time, for example 2, 3, 4 times. Here, the first time or the second time is compared with the count value (count time) by the counting means. The time can be expressed by a count value incremented for each interrupt, and the count value can be expressed by time by a product with the interrupt interval, so that the above comparison is possible.

  The predetermined processing is processing for shifting a sequence number of a packet transmitted after the second time by a predetermined value, and the data processing means may detect the change of the predetermined value and perform the predetermined data processing. good.

  With this configuration, the data transmission device can transmit the packet retransmission cancellation to the data reception device by a simple and simple process such as changing the sequence number without using a separate means.

  Here, the predetermined value may be a value approximately half of the maximum value of the sequence number, and the data processing means may change the predetermined value by more than about a quarter of the maximum value of the sequence number. It is also possible to perform the predetermined data processing by detecting that the

  The reason why the predetermined value is approximately half of the maximum value of the sequence number is that the numerical value indicates the maximum distance (deviation) in the sequence number to be circulated. Further, in order to determine the transition of the predetermined value, approximately half of the predetermined value is set as a threshold value. Any numerical value is an example of implementation, and any numerical value that can be easily calculated can be selected.

  The predetermined processing is processing for resetting a sequence number of a packet to be transmitted after the second time to a predetermined value, and the data processing means detects the reset to the predetermined value and performs the predetermined data processing. It is also good.

  Even in such a configuration, the data transmission device can transmit the cancellation of packet retransmission to the data reception device by a simple and simple process such as resetting the sequence number to a certain value without using a separate means. Become.

  Here, the predetermined value may be 0 (zero), and the data processing means may perform the predetermined data processing by detecting that the sequence number is 0 (zero). The predetermined value 0 represented by so-called NULL is obtained by resetting the count value in hardware and is easy to use.

  The predetermined processing may set a flag indicating that retransmission is to be stopped in the next packet to be transmitted after the second time, and the data processing means may perform the predetermined processing when the flag is set in the received packet. The data processing may be performed.

  With such a configuration, the data transmission apparatus can transmit the cancellation of packet retransmission to the data reception apparatus with only a simple and simple process of continuously transmitting a packet without using a separate means.

  The predetermined process may be a process of indicating that the retransmission is stopped after the second time and transmitting another packet having a different frame, and the data processing means receives the other packet and Predetermined data processing may be performed.

  With such a configuration, it is possible to transmit a packet retransmission stop to the data receiving apparatus in a packet different from the packet to be transmitted.

  Here, the cancellation processing means may transmit the other packet at a reduced packet transmission rate. With this configuration, the data transmission device can reliably transmit the cancellation of packet retransmission to the data reception device.

  The predetermined processing may be a beacon indicating that retransmission is stopped after the second time, and the data processing means may receive the beacon and perform the predetermined data processing. .

  The above-mentioned beacon is a network of communication devices that are not superior to each other, what kind of device the data transmission device or data reception device is, what device is desired to communicate with, and under what circumstances In order to let other devices know whether there is any information, the information transmission frame is transmitted at regular intervals or constantly.

  The beacon is transmitted regardless of whether or not the data transmission apparatus performs data transmission processing. Therefore, using this existing transmission means, it is possible to notify the data reception device of the suspension of packet retransmission without providing a new means.

  The predetermined process may be a process for stopping transmission of the packet for a certain period, and the data processing means may perform the predetermined data process upon detecting that the packet is not received for the certain period. .

  The reason why the cancellation processing unit cancels the transmission for a certain period is to intentionally indicate to the data receiving device that the retransmission is stopped, which is different from the configuration of a timeout due to a transmission error. This indicates that the data transmission apparatus side has the decision right to cancel the retransmission of the packet.

  With this configuration, the data transmitting apparatus can transmit the cancellation of packet retransmission to the data receiving apparatus without transmitting special information. In this case, the predetermined period may be determined in advance in the data receiving device, but may be specified from the data transmitting device at the time of initialization. In either case, the data transmission device resumes packet transmission after the predetermined period has elapsed.

  In addition, a data transmission device and a data reception device constituting the data transmission system, a computer program for causing a computer to function as the data transmission device and the data reception device, and the data transmission device and the data reception device are used. A data transmission method for transmitting data is also provided.

  In order to solve the above-mentioned problem, according to a second aspect of the present invention, there is provided sequence providing means for dividing data into a plurality of packets and assigning unique sequence numbers to each of the packets; A transmission determining means for determining a transmission order; a packet transmitting means for transmitting a packet to the data receiving device in accordance with the transmission order of the packets; a count for counting an elapsed time from the first transmission of the packet for each of the packets Means; a count stop means for stopping counting of packets corresponding to the reception completion signal received from the data receiving device; and a packet having a sequence number not receiving the reception completion signal for a predetermined first time using the counting means. A packet retransmission means for retransmitting at an interval; a buffer used at the time of transmitting the packet has a predetermined capacity; When there was example, it stops transmission of the next subsequent packet, the abort processing means performs predetermined processing that indicates the termination of transmission; characterized in that it comprises a data transmission device is provided.

  When the frequency of occurrence of buffer overflow due to retransmission is higher than the frequency at which retransmission of packets is canceled by comparison with the second time described in the first aspect, there is a high probability that data will be invalidated due to buffer overflow. Become. With this configuration, buffer overflow can also be prevented.

  The cancellation processing means may further clear the input data of the buffer when the buffer exceeds a predetermined capacity. In the configuration in which the packet is discarded due to the overflow, the packet still remaining in the buffer is handled as invalid data in the data receiving apparatus. Therefore, the packet stored in the buffer may be cleared as an invalid packet. Also, if data processing is continued without such clearing, the same overflow can occur immediately.

  The data transmission in the first and second aspects may be used in a CW network that is a network of communication devices that are not superior to each other. In such a CW network, there is no specific control station, and each communication device manages itself and has no superiority or inferiority relationship. Accordingly, each communication device operates in an autonomous and distributed manner to form an ad hoc network.

  The data may be moving image data representing real-time image operation. The present invention can be used mainly for reproducing moving image data that requires the highest priority on real-time performance, such as a DVD (Digital Versatile Disk), and the flow of moving image reproduction changes due to reliable restoration of missing packets. No, that is, it is suitable for data communication that allows some image disturbance.

  Also provided are a computer program for causing a computer to function as the data transmission device, and a data transmission method for transmitting data using the data transmission device and the data reception device.

  Further, the data transmitting device and the data receiving device can be configured as one device.

  As described above, according to the present invention, even if there is a packet transmission error, it is possible to maintain real-time data reproduction without changing the data transmission efficiency. Therefore, it is possible to realize a high-speed wireless network that can forcibly recover from a transmission error without duplicating data or changing the order even when packets are continuously transmitted at high speed.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment: data transmission system)
In this embodiment, a data transmission system using a plurality of communication devices capable of exchanging data using various communication paths is provided. Among such communication paths, data is exchanged between a plurality of communication devices, particularly assuming communication via a wireless transmission path. Each communication device has a communication station for wireless communication. Each communication station performs radio communication using a transmission medium composed of a single channel or a plurality of frequency channels (multi-channel).

  FIG. 1 is a schematic diagram illustrating an arrangement example of communication devices in a data transmission system. In this data transmission system, there is no specific control station as a communication station, and each communication device operates in an autonomous distributed manner to form an ad hoc network. Here, four communication devices 102, 104, 106, 108 are shown, and each communication device 102, 104, 106, 108 is another communication device 102, 104, 106, 108 within its own communicable range 120, respectively. Wireless communication with 108 is performed. For example, the communication device 102 is a communication device 104, 106, the communication device 104 is a communication device 102, 106, the communication device 106 is a communication device 102, 104, 108, and the communication device 108 is a wireless communication transmission path with the communication device 106. Form. Here, each communication device 102, 104, 106, 108 recognizes a communication device within the communicable range 120 as a communication device capable of communication and as a communication device that may interfere with its own communication data.

  Further, the present embodiment is not limited to the above-described autonomous distributed wireless communication, but can also be applied to wireless communication having a control station and wired communication.

  FIG. 2 is a block diagram for explaining another communication path of the present embodiment. The communication device 102 and the communication device 104 form the autonomous distributed wireless communication described above. The communication devices 102 and 104 can further perform wireless communication with the control station 150. In this case, the communication devices 102 and 104 transmit and receive data in accordance with a control signal from the control station 150. It is also possible to communicate by connecting to the user terminal 154 via a wired transmission line such as the communication network 152. As described above, the present embodiment can be applied to any communication network regardless of wireless cable.

  3A and 3B are block diagrams showing individual device configurations of the data transmission system shown in FIG. 1 and FIG. Referring to FIG. 3A, the data transmission system includes a data transmission device 210 that transmits data and a data reception device 220 that receives data transmitted from the data transmission device 210. In addition, as shown in FIG. 3B, one communication device 234 can include a data transmission unit 230 that functions as the data transmission device 210 and a data reception unit 232 that functions as the data reception device 220. In such a communication device 234, data can be transmitted from one data transmission unit 230 to the other data reception unit 232 (indicated by an arrow in the figure), and mutual data exchange is possible.

  Here, in order to facilitate understanding, the data transmission device 210 and the data reception device 220 shown in FIG. 3A will be taken and described in detail.

  In the present embodiment, the data transmission device 210 stops (abortions) further retransmission of a packet that has been retransmitted to some extent, and the data reception device 220 cancels the retransmission (regardless of such a packet loss). It is characterized by data processing in response to abandonment. Further, as will be described below, the data receiving device 220 can easily determine that a packet is not retransmitted, and it is possible to reliably synchronize valid data and invalid data in both devices. That is, data invalidated by the data transmission device 210 is treated as invalid data by the data reception device 220, and data validated by the data transmission device 210 is valid data without being erroneously determined by the data reception device 220. Are treated as

  The fact that the data transmission device 210 cancels the retransmission of the packet gives priority to the real-time property of the data processing on the data reception device side over the reliable transmission of the packet, and “the packet is transmitted completely. Can be considered to be transmitted to the data receiving device 220.

  The data receiving device 220 that has received such transmission processes data lacking such a packet, and resumes normal communication while maintaining synchronization with the data transmitting device. At this time, the data receiving device 220 may abandon the data in which the packet is missing, or may perform some processing using the remaining packet (packet in the missing state).

(Data transmission device 210)
FIG. 4 is a block diagram showing the configuration of the data transmission device 210. The data transmission device 210 includes a data transmission control unit 250, a sequence assignment unit 252, a transmission determination unit 254, a packet transmission unit 256, an antenna unit 258, a count unit 260, a count stop unit 262, a packet retransmission unit, and the like. A transmission unit 264 and a cancellation processing unit 266 are included.

  The data transmission control unit 250 centrally manages and controls a series of processes in the data transmission device 210 by a control device including a central processing unit (CPU).

  The sequence assigning means 252 divides the data to be transmitted in the data transmission device 210 into a plurality of packets represented by a predetermined frame, arranges the plurality of packets in the order of transmission, and each packet is, for example, a continuous number Gives the unique sequence number represented.

  The transmission determining unit 254 determines a temporary transmission order of packets according to the sequence number assigned by the sequence assigning unit 252. Here, the reason is that the packet retransmitting means 264, which will be described later, interrupts a packet transmitted in the past as a transmission packet again, so that the packets are not always transmitted in the order of the sequence numbers by the packet transmitting means 256. is there. Such a sequence number is given by incrementing a certain value (for example, 1). With such a sequence number, even if the order of packets received by the data receiving apparatus is changed, it can be reliably restored to the data before division.

  The packet transmitting unit 256 transmits the packet to the data receiving device 220 in accordance with the transmission order determined by the transmission determining unit 254. Further, the packet transmission unit 256 or the transmission determination unit 254 may have a data buffer for temporarily storing packets from the transmission determination unit 254 and the packet retransmission unit 264, and the packet input to the buffer may be stored. , And sent through the antenna unit 258 in the order of input to the buffer.

  The antenna unit 258 wirelessly transmits an electromagnetic wave signal to the data reception device 220 on a predetermined frequency channel, and receives a reception completion signal (hereinafter referred to as ACK) sent from the data reception device 220. Also, other packets, beacons, etc., which will be described later, can be transmitted.

  When the packet transmission unit 256 transmits a packet for the first time (not including the retransmission of the packet), the counting unit 260 counts the elapsed time using the transmission of this packet as a trigger. Such counting may be performed using a counter provided for each packet, but it is also possible to count the transmission elapsed time of all packets using one counter.

  FIG. 5 is an explanatory diagram showing an example of counting all transmission elapsed times using one counter. The counter 280 of the counting means 260 counts a number from 0 to 9999 in response to an interrupt of 1 msec, for example. Accordingly, the count value advances to 0, 1, 2, 3,... And repeats 0 to 9999. When the packet transmission means 256 transmits the packet A when the count value becomes “102”, the count value 282 at the time of transmission of the packet A becomes “102”. Similarly, if the packet B is transmitted when the count value is “203” and the packet C is transmitted when the count value is “405”, the count value 284 at the time of transmission of the packet B is set to “203”. The count value 286 is “405”.

  When calculating the elapsed time at a certain point, the difference between the count value at that point and the count value at the time of transmission is taken. For example, if the count value 290 at a certain time is “1010”, the elapsed time at this time is calculated by taking the difference between the count value 290 and the count value at the time of transmission. Accordingly, the elapsed time 292 of the packet A is “908”, the elapsed time 294 of the packet B is “807”, and the elapsed time 296 of the packet C is “605”. Although the elapsed time at this time is expressed as a count value, when calculating the actual elapsed time, it is calculated by taking the product of 1 msec which is the interrupt interval. In this way, the elapsed time from the transmission of all packets can be counted by one counter.

  When the ACK is returned from the data receiving device 220, the count stopping unit 262 stops counting the packet corresponding to the ACK by the counting unit 260. For example, in the example shown in FIG. 5, the count can be stopped by stopping incrementing the elapsed time or deleting the packet from the count target packet.

  The packet retransmitting means 264 retransmits a packet having a sequence number that has not received an ACK from the data receiving apparatus 220 at a predetermined first time interval using the counting means 260. That is, when the counting of the counting unit 260 is continuing and the count value does not exceed the predetermined second time, the transmission determining unit 254 changes the transmission order and retransmits the packet every predetermined first time. Let The second time is represented by, for example, “3000” (3 seconds), and the first time is represented by, for example, “1000” (1 second). If the count value indicating the elapsed time exceeds "1000" under the above conditions, the target packet is considered not to be transmitted correctly, and the packet to be retransmitted is the packet that is normally arranged according to the sequence number. Interrupt. If there is no ACK reply from the data receiving device 220 even after the first time has elapsed since the retransmission of the packet, the packet retransmission means 264 retransmits the packet again.

  FIG. 6 is an explanatory diagram for explaining the determination of the transmission order of packets by the transmission determination means 254. Usually, the transmission determining unit 254 sets the transmission order 314 according to the sequence number 312 assigned to each packet 310 in the sequence assigning unit 252. However, if there is no ACK response from the data receiving apparatus 220 even if the first time has passed with respect to the packet 316 having the sequence number “1” transmitted in the past, the packet 316 having the sequence number “1” should be transmitted. It is added to the end 318 of the packet. The addition of the packet with the sequence number “12” that should be originally arranged at the position of the packet 316 with the sequence number “1” is awaited, and the transmission order determined by the transmission determination unit 254 is “9”, “10”. , “11”, “1”, “12”,.

  Here, it is assumed that the packet 316 with the sequence number “1” is added to the tail 318 of the packet to be transmitted by the transmission determination unit 254. However, the packet 316 is forcibly set before the packet with the sequence number “9” that is the front row. It may be added.

  The cancel processing means 266 cancels retransmission of a packet having a sequence number that does not receive an ACK within a predetermined second time, and performs a predetermined process indicating that the retransmission is stopped. That is, when the count is continuing and the count value exceeds a predetermined second time, the retransmission of the packet is stopped, and the stop of the retransmission is transmitted to the data receiving device 220 by a predetermined process. The cancellation processing unit 266 will be described in detail later.

  In addition, the cancellation processing unit 266 determines that the buffer used for packet transmission by the packet retransmission unit 264 has a predetermined capacity instead of stopping the packet retransmission by determining whether the count value exceeds a predetermined second time. It is also possible to adopt a configuration in which retransmission of a packet is canceled when the number exceeds. In stopping this retransmission, the predetermined processing described above may be performed.

  When the frequency of occurrence of buffer overflow due to retransmission is greater than the frequency at which packet retransmission is stopped by comparison with the second time described above, the probability that data will be invalidated due to buffer overflow increases. At this time, communication with high transmission efficiency can be resumed by stopping the retransmission of the packet. The cancellation processing unit 266 due to overflow may be configured independently, or may be used in combination with a configuration in which the second time is compared with the count value to stop packet retransmission.

  Further, the cancellation processing unit 266 may further clear the input data of the buffer when the buffer exceeds a predetermined capacity. In the configuration in which the packet is discarded due to the overflow, the packet still remaining in the buffer is handled as invalid data in the data receiving apparatus. Therefore, the packet stored in the buffer may be cleared as an invalid packet.

(Data receiving device 220)
FIG. 7 is a block diagram illustrating a configuration of the data transmission device 220. The data reception device 220 includes a data reception control unit 350, an antenna unit 352, a packet reception unit 354, a reception response unit 356, a processing start unit 358, and a data processing unit 360.

  The data reception control unit 350 centrally manages and controls a series of processes in the data reception device 220 by a control device including a central processing unit (CPU).

  The antenna unit 352 receives an electromagnetic wave signal from the data transmission device 210 and transmits an ACK signal to the data transmission device 210. Further, another packet, a beacon, or the like composed of different frames, which will be described later, can be received.

  The packet receiving unit 354 receives the packet transmitted from the data transmission device 210 via the antenna unit 352.

  The reception response unit 356 sends an ACK response to the data transmission apparatus 210 in accordance with the packet received by the packet reception unit 354. Here, an error check of the received packet, for example, a CRC (Cyclic Redundancy Check) check may be performed, and an ACK may be returned only for a packet in which no error is detected by the check.

  After receiving a predetermined number of packet groups arranged in the order of sequence numbers, the process starting means 358 decodes the packet groups into data that can be processed by the data receiving device 220, and the data receiving device 220 processes the data. Start.

  The data processing unit 360 gives up the complete restoration of the packet to be processed in response to a predetermined process for stopping the retransmission of the packet in the data transmission apparatus 210, and the packet group is not completely aligned ( Normal packet communication is resumed while maintaining the synchronization with the data transmission device. At this time, the data processing unit 360 may abandon the data in which such a packet is lost, or may perform some processing such as forcibly processing using the remaining packet. The data processing unit 360 will be described in detail later together with the cancellation processing unit 266.

(Data transmission system)
In order to deepen the understanding of the data transmission system, the basic flow of data transmission in the data transmission system will be described.

  FIG. 8 is a diagram for explaining the flow of data in the data transmission system. Here, data 410 is transmitted from data transmitting apparatus 210 to data receiving apparatus 220.

  First, in the data transmission apparatus 210, the data 410 to be transmitted by the sequence assigning means 252 is divided into a plurality of packets 412 formed from frames having the same configuration, and the packet 412 is assigned with a sequence number 414 of “1”, “2 ”,“ 3 ”,... Communication in the present embodiment is performed in units of packets. Thereafter, the transmission order of the packets is determined by the transmission determining means 254. Here, it is assumed that the packets are transmitted in the order of sequence numbers for simplicity.

  In FIG. 8, packets 412 having sequence numbers “1” and “2” have already been transmitted to the data receiving apparatus, and the data receiving apparatus 220 rearranges the packets in the order of the sequence numbers regardless of the order of reception. Here, regardless of the order of reception, the transmitted packets may not reach the data reception device 220 for some reason. Even if the data transmission device 210 transmits the packets in the order of the sequence numbers, the order is not necessarily limited. This is because it is not always received by the data receiving device 220.

  The packets received in this way are arranged in the sequence number order 416 and restored to the original data 410 when a predetermined number of packets are arranged as a packet group.

  FIG. 9 is an explanatory diagram showing a frame of a packet transmitted in the data transmission system. The frame includes a PHY header 450, a destination address 452, a transmission source address 454, a frame length 456, a sequence number 458, divided data 460, and a CRC 462.

  The PHY header 450 describes header information of this frame, and the destination address 452 describes the destination address of this packet, that is, the address of the data receiving device 220. In the transmission source address 454, the address of the data transmission apparatus 210 is described. The frame length 456 indicates the frame length of the packet. The sequence number 458 describes the sequence number assigned to each packet by the sequence assigning means 252. The divided data 460 describes data having a predetermined length after the original data is divided into packets. The CRC 462 describes a cyclic code for checking a data transmission error.

  Next, packet transmission according to the present embodiment is compared with transmission according to the conventional IEEE802.11a standard in which the packet is retransmitted many times until ACK is returned.

  FIG. 10 is a flowchart showing communication between the transmission-side communication device 470 and the reception-side communication device 472 according to the IEEE 802.11a standard. In the wireless communication protocol based on the IEEE802.11a standard, data is divided into packets by the transmission side communication device, and the packet is transmitted to the reception side communication device. In FIG. 10, an ACK response regarding the packet 480 having the sequence number “1” transmitted first among the divided packets is not obtained, and the packet 480 is retransmitted a plurality of times. In this case, the packet 486 with the sequence number “2” to be transmitted next is waited until the transmission of the packet with the sequence number “1” is completed, and transmission processing is not performed until there is an ACK 488 from the data receiving apparatus. In such a transmission system, when there is no response to the ACK signal, the same packet is retransmitted many times. During this time, the next packet cannot be transmitted, and there is a problem that data transmission is delayed. .

  Next, the flow of the data transmission system according to this embodiment will be described. Here, the description will focus on the stop processing unit 266 and the data processing unit 360, which are the features of the present embodiment.

  FIG. 11 is a flowchart showing communication between the data transmission device 210 and the data reception device 220 in the present embodiment. Here, the divided packets are transmitted sequentially without waiting for ACK. For example, if the data to be transmitted is divided and the sequence number is assigned from “1”, the packet 510 having the sequence number “1” is transmitted, and then the next sequence number “2” is not waited for the ACK for the packet. ”,“ 3 ”, and“ 4 ”packets 512 are transmitted.

  In response to this continuous packet transmission, the data receiving apparatus 220 returns an ACK regarding the packet for which reception has been completed. This ACK signal may be transmitted for each packet, or may be transmitted collectively (group ACK 514) for a plurality of packets.

  When the transmission of the packet 512 with the sequence number “4” is completed and the counter of the packet 510 with the sequence number “1” has passed the predetermined first time 516, the packet retransmission unit 264 uses the same packet as the packet 510. 520 is retransmitted. Since the ACK is returned from the data receiving apparatus 220 for the other packets 512 having the sequence numbers “2”, “3”, and “4” that have already been transmitted, the packet to be transmitted next depends on the normal transmission order. It becomes the packet 522 of the sequence number “5”. Similarly, if no ACK is returned to the packet 520, the same packet 524 as the packet 510 is transmitted after the first time 516 has elapsed since the transmission of the packet 520.

  In this manner, the retransmission of the packet 510 with the sequence number “1” is repeated, and when the fixed second time 530 has elapsed, the cancel processing unit 266 gives a signal to give up the retransmission of the packet 510. Here, the sequence number of the packet to be transmitted next is shifted by “128” which is a predetermined value. Therefore, the sequence number “11” of the packet 532 to be transmitted next is added to “128” and rewritten to “139”, and is transmitted to the data receiving apparatus 220 with a new sequence number. The Similarly, the sequence number “12” of the packet 536 is rewritten to “140”, and the sequence number “13” of the packet 540 is rewritten to “141” and transmitted to the data receiving apparatus 220.

  Sequence number assignment by the sequence assigning means 252 circulates numbers “0” to “255”, and the predetermined value “128” is “256”, which is the number of times the sequence number is circulated (or the maximum value). Divided.

  The data processing unit 360 of the data receiving apparatus 220 detects the change of the predetermined value and proceeds with the process. In the data processing means 360, in order to determine the change of the predetermined value, “64” which is half of the predetermined value “128” is set as a threshold value. Therefore, the data processing unit 360 determines that the difference between the sequence number “10” of the packet 544 received a little earlier and the sequence number “139” of the next received packet 532 is “64” or more, and Packet groups that have been restored but not restored as data, for example, sequence numbers “2”, “3”, “4”, “5”, “6”, “7”, “8”, “9” , “10” is discarded as invalid data.

  At this time, if the above communication data is acceptable even if there is some disturbance in the image such as moving image data, the packet group is not discarded as described above, and the original packet is forcibly left missing. It can also be restored to the data. Of course, in this case, it is not possible to expect a complete image to be displayed when such data is displayed.

  Next, a case where the cancel processing unit 266 cancels retransmission of a packet by processing different from the above will be described.

  FIG. 12 is a flowchart showing communication between the data transmission device 210 and the data reception device 220 in the present embodiment. Here, similar to the above-described communication, the divided packets are sequentially transmitted without waiting for ACK. Since the communication procedure already described as a component in the embodiment shown in FIG. 11 has substantially the same function in FIG. 12, a duplicate description is omitted, and the sequence number reset that is different between FIG. 11 and FIG. In the following.

  Similarly to FIG. 11, when the ACK for the packet 510 with the sequence number “1” is not returned and the fixed second time 530 has elapsed, the cancel processing unit 266 gives a signal to give up the retransmission of the packet 510. Here, the sequence number of the packet to be transmitted next is reset to “0” which is a predetermined value. Therefore, the sequence number “11” of the packet 532 to be transmitted next becomes “0”, and is transmitted to the data receiving apparatus 220 with a new sequence number assigned. Similarly, the sequence number “12” of the packet 536 is rewritten to “1” and the sequence number “13” of the packet 540 is rewritten to “2” and transmitted to the data receiving apparatus 220.

  The predetermined value “0” is represented by so-called NULL, and can be easily set by resetting the count value in hardware.

  After the packet is transmitted, the data processing unit 360 of the data receiving device 220 detects the reset to the predetermined value “0” and proceeds with the process. Accordingly, the data processing means 360 of the data receiving apparatus 220 has the sequence number “10” of the received packet 532 as “0” and the sequence number “10” of the previously received packet 544 as the maximum value “255” of the sequence number. , And a packet group that has been received but not restored as data, for example, sequence numbers “2”, “3”, “4”, “5”, “6”, “7” ”,“ 8 ”,“ 9 ”,“ 10 ”are discarded as invalid data. Again, if the above communication data is acceptable even if there is some image disturbance, such as video data, the packet group is not discarded as described above, and the original packet is forcibly left missing. It can also be restored to the data.

  Also, the cancellation processing unit 266 can express the cancellation of packet retransmission by the process of setting a flag. When the count is continuing and the count value exceeds a predetermined second time, the cancel unit 266 sets a flag indicating the stop of retransmission provided in the packet transmitted to the data receiving device 220 next. . In addition, the data processing unit 360 of the data receiving apparatus 220 proceeds with the process by determining whether or not a flag indicating that retransmission has been stopped is set in the received packet.

  FIG. 13 is an explanatory diagram showing a packet frame when a flag 570 is added. The flag 570 is arranged between the frame length 456 and the sequence number 458, and has at least 1-bit information regarding cancellation of packet retransmission. Further, the arrangement of the flag 570 is not limited to the above case, and may be arranged anywhere in the frame.

  Also, the cancellation processing unit 266 can express the cancellation of packet retransmission by a packet different from the main packet into which data is divided. When the count is continuing and the count value exceeds a predetermined second time, the other packet including the stop of retransmission of the packet as data is transmitted. On the other hand, the data processing unit 360 determines that the received packet is the other packet and proceeds with the next processing. In this case, another packet can be transmitted at a reduced transmission rate in order to avoid a state where another packet cannot be received.

  FIG. 14 is an explanatory view showing an example of a frame of such another packet. Within the frame of such another packet, the frame has a field of the frame type 580 indicating that it is not a data frame but a control frame, and the sequence number is inconsistent in the field of the control data 582 indicating the control content. Indicates a sequence number error indicating that has occurred. When the data processing unit 360 receives the other packet, the data processing unit 360 recognizes that this is a signal for stopping the packet retransmission, and proceeds with the data processing in a state where the packet is missing.

  In addition, the cancellation processing unit 266 can be expressed by putting a signal indicating cancellation of packet retransmission on the beacon. This beacon is transmitted from all the data transmission devices 210, particularly in the CW network, regardless of whether or not the data transmission processing of the data transmission device 210 is performed. Therefore, using this existing transmission means, it is possible to notify the data reception apparatus 220 of the suspension of packet retransmission without providing any new means.

  The above-mentioned beacon is a network of communication devices that are not superior to each other, what kind of device the data transmission device or data reception device is, what device is desired to communicate with, and under what circumstances In order to let other devices know whether or not there is an information transmission frame, the information transmission frame is transmitted at regular intervals or constantly.

  FIG. 15 is an explanatory diagram showing an example of such a beacon frame. In such a beacon frame, the frame has a field indicating a beacon type 590 indicating that it is not a data frame but a beacon, and a control field 592 for controlling a radio station in the same network. The control field 592 further includes fields of control type, first target station, and second target station. For example, a sequence number error, the MAC address of the first target station, and the MAC address of the second target station are described. Yes. By using such a beacon, it is transmitted to the transmitting station and receiving station of the data stream that the sequence number is initialized, and the data processing means 360 of the wireless station that has received the beacon transmits a sequence number error to its own data communication. The processing of data is performed in a state where packets are lost. In this way, synchronization of each station is established.

  In addition, the cancellation processing unit 266 can express the cancellation of packet retransmission by changing the packet transmission time. When the count is continuing and the count value exceeds a predetermined second time, the packet transmission by the packet transmission unit 256 is temporarily stopped, and the transmission is resumed after a certain period, for example, 1 second. The data processing unit 360 detects that a packet is not received for a certain period and proceeds with the processing.

(Second Embodiment: Data Transmission Method)
Next, a data transmission method for transmitting data using the data transmission device 210 and the data reception device 220 described above will be described.

  FIG. 16 is a flowchart illustrating a conceptual flow of the data transmission method. In the above transmission method, first, the data transmitting apparatus 210 divides data to be transmitted into a plurality of packets composed of the same frame, and sequentially assigns sequence numbers expressed in ascending or descending order to the plurality of packets (S700). ). Then, the transmission order of packets to be actually transmitted is determined according to the sequence number (S702). At this time, if the packet retransmission in the packet retransmission step (S722) described later is not requested, the transmission order can be the same as the sequence number. Subsequently, the data transmission device 210 transmits the packet to the data reception device 220 via a wireless or wired transmission path according to the packet transmission order in the transmission determination step (S702) (S704). The elapsed time starts counting immediately after the transmission (S706). Such a count is managed for each packet.

  Next, the data receiving device 220 receives the packet transmitted from the data transmitting device 210 (S710), confirms that this packet is a normal packet without an error using a CRC check, etc. An ACK that is a reception completion signal is transmitted to the transmission device 210 (S712). When all the packets forming a predetermined number of packet groups arranged in sequence number order are received, the packet groups are decoded into data, and processing of the data is started (S714).

  Subsequently, when receiving an ACK from the data receiving apparatus 220, the data transmitting apparatus 210 only stops counting packets related to the ACK (S720). If the ACK is not received, that is, if the count for the specific packet is continuing and the predetermined first time has passed, the transmission order determined in the transmission determination step (S702) is changed and no ACK is returned. The packet is retransmitted (S722). Further, when the count continues further without receiving the ACK and the predetermined second time has elapsed, the data transmission device 210 stops (abortions) the retransmission of the packet, and retransmits the data reception device 220 by a predetermined process. The cancellation of transmission is transmitted (S724).

  In response to the predetermined processing in the data transmission device 210, the data reception device 220 proceeds with the data processing or the next processing in a state where the packets are not completely aligned (a state where the packet is missing) (S730).

  The predetermined processing described here has substantially the same function as the predetermined processing described in the data transmission system according to the first embodiment, and thus a duplicate description is omitted.

  Thus, the data transmission method is largely divided into a sequence adding step (S700), a transmission determining step (S702), a packet transmitting step (S704), a counting step (S706), a packet receiving step (S710), and a reception response step (S712). , A process start step (S714), a count stop step (S720), a packet retransmission step (S722), a stop processing step (S724), and a data processing step (S730). Below, this process is demonstrated in detail.

  The data transmission method is realized by generating an interrupt at every predetermined sampling time and performing the following processing for each interrupt. Here, the processing in the data transmission device 210 and the processing in the data reception device 220 will be described separately.

  FIG. 17 is a flowchart showing the flow of the sequence assigning step (S700). 17 to 21 describe processing in the data transmission apparatus 210. FIG. In the sequence assigning step (S700), an interrupt is received (S750), and data is input for transmission (S752). The input data is divided into a plurality of packets formed in the same frame (S754), and the divided packets are input one by one (S756). At this time, if it is indicated that the retransmission has been abandoned, that is, if the ACK for the packet is not returned even after a predetermined second time has elapsed (S758), a new sequence number is set (S760). The new sequence number may be a value obtained by adding approximately half the maximum value of the sequence number to the original sequence number, or may be a predetermined value, for example, zero (0). When the sequence number is determined in this way, the new sequence number is assigned to the divided packet (S762).

  When the sequence number is given, the sequence number held in the data transmitting apparatus 210 is not assigned to the other packet so as not to assign the sequence number to the other packet and to define the packet transmission order in the packet transmission step (S704). Update, that is, increment by a predetermined value (S764). Then, it is determined whether or not the divided packet still remains (S766). If it remains, the process repeats from the packet input process (S756).

  FIG. 18 is a flowchart showing the flow of the transmission determination step (S702). In the transmission determination step (S702), whether or not a buffer (such as a FIFO) that is provided in the data transmission device 210 and temporarily holds a packet is empty, that is, the buffer has a sufficient capacity and can be input. It is confirmed whether the current state is correct (S770). When it is confirmed that the buffer is free, it is confirmed whether there is a packet to be retransmitted in a packet retransmission step (S722) described later (S772). If it is found in this confirmation step (S772) that there is a retransmission packet, the packet is loaded into the buffer (S774). If there is no retransmission packet, a packet to be newly transmitted is loaded into the buffer according to the sequence number assigned in the sequence assignment step (S700) (S776).

  FIG. 19 is a flowchart showing the flow of the packet transmission step (S704) and the counting step (S706). In the packet transmission step (S704), it is confirmed whether or not the transmission device is ready for transmission (S780). If the transmission device is ready for transmission, the packet is transmitted to the data reception device 220 according to the transmission order input to the buffer. Transmission is performed (S782). Simultaneously with the transmission of this packet, counting as to the packet is started (S784) as part of the counting step (S706). This count is incremented in units of interrupts as described above.

  FIG. 20 is a flowchart showing the flow of the count stop step (S720). In the count stop step (S720), the ACK of the data receiving device 220 for the packet transmitted in the packet transmission step (S704) is confirmed (S800). Here, when the ACK is received, the counting in the counting step (S706) regarding the ACK is stopped, and the transmission of the packet is completed (S802).

  FIG. 21 is a flowchart showing the flow of the packet retransmission step (S722) and the cancellation processing step (S724). In the packet retransmission step (S722), whether the count value in the counting step (S706) exceeds the second time is compared (S810). If the count value is less than the second time, They are compared (S812). If the count value exceeds the first time, the packet is retransmitted, and the transmission order determined in the transmission determination step (S702) is changed (S814). This packet retransmission (S814) is performed every time the first time elapses. When the count value exceeds the second time in the comparison between the count value and the second time (S810), the packet retransmission is stopped (abandoned), and the data reception device 220 is canceled by a predetermined process. Transmit (S816). Thus, the interrupt process is completed (S818).

  FIG. 22 is a flowchart showing the flow of the packet reception process (S710), the reception response process (S712), and the process start process (S714). 22 and 23 illustrate processing in the data receiving apparatus 220. FIG. In the packet receiving step (S710), it is confirmed whether or not a packet has been received from the data transmitting apparatus 210 in the repeated processing upon receiving an interrupt (S830) (S832). When the reception of the packet is confirmed here, it is confirmed whether or not the packet is a normal packet by calculating the packet length, parity, CRC, and the like (S834). If it is determined that the packet is normal, the received packet is stored, and an ACK is returned to the data transmitting apparatus 210 as the reception response step (S712) (S836). Subsequently, it is confirmed whether or not a predetermined number of packet groups arranged in the order of sequence numbers are prepared by the received packet (S838). If the packet groups are prepared, the packet group is decoded into data as the processing start step (S714). Then, the processing of the data is started (S840).

  FIG. 23 is a flowchart showing the flow of the data processing step (S730). In the packet receiving step (S710) described above, a plurality of packets transmitted from the data transmitting device 210 are received, and when a prescribed packet is prepared, it is restored to data forming a predetermined processing unit. However, if the re-transmission is stopped by a predetermined process of the data transmitting apparatus 210, the data processing step (S730) is performed. First, the data transmission apparatus 210 detects whether or not the retransmission is stopped (S850). When the retransmission is detected, the reception is completed and the missing of the packet that has not been restored to the data is determined. The data receiving apparatus 220 processes the data while the packet is missing, or proceeds with the data processing ignoring the missing data (S852). Thus, the interrupt process is completed (S854).

  By such a data transmission method, even if there is a packet transmission error, it is possible to maintain real-time data reproduction without changing the data transmission efficiency.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are of course within the technical scope of the present invention. Understood.

  For example, in the above embodiment, the transmission of the packet retransmission stop was described by giving several examples. However, the data transmission apparatus intentionally stops the packet transmission and reliably transmits it to the data reception apparatus. As long as it is possible, various implementation means such as changing the length of the data frame are possible without being limited to the example of the present embodiment.

  Further, in the above embodiment, the data transmission device notifies the data reception device of the suspension of retransmission by a predetermined process. However, this is not the case, and the data transmission device intentionally receives data. The predetermined processing of this embodiment can also be used when initializing a packet or data of an apparatus.

  The present invention is applicable to a data transmission system and method, a data transmission device, a data reception device, and a computer program thereof.

It is the schematic which showed the example of arrangement | positioning of the communication apparatus in a data transmission system. It is a block diagram for demonstrating the other communication path | route of 1st Embodiment. It is a block diagram which shows each apparatus structure of a data transmission system. It is a block diagram which shows each apparatus structure of a data transmission system. It is a block diagram which shows the structure of a data transmitter. It is explanatory drawing which showed an example which counts all the transmission elapsed time using one counter. It is explanatory drawing for demonstrating the determination of the transmission order of the packet by a transmission determination means. It is a block diagram which shows the structure of a data transmitter. It is a figure explaining the flow of data in a data transmission system. It is explanatory drawing which showed the flame | frame of the packet transmitted in a data transmission system. It is the flowchart which showed communication with the transmission side communication apparatus by the IEEE802.11a standard, and the reception side communication apparatus. It is the flowchart which showed communication with the data transmitter in 1st Embodiment, and a data receiver. It is the flowchart which showed communication with the data transmitter in 1st Embodiment, and a data receiver. It is explanatory drawing which showed the flame | frame of the packet at the time of adding a flag. It is explanatory drawing which showed an example of the flame | frame of another packet. It is explanatory drawing which showed an example of the flame | frame of a beacon. It is the flowchart figure explaining the rough flow of the data transmission method. It is the flowchart which showed the flow of the sequence provision process. It is the flowchart which showed the flow of the transmission determination process. It is the flowchart which showed the flow of the packet transmission process and the count process. It is the flowchart which showed the flow of the count stop process. It is the flowchart which showed the flow of the packet re-transmission process and the cancellation process process. It is the flowchart which showed the flow of the packet reception process and a reception response process. It is the flowchart which showed the flow of the data processing process.

Explanation of symbols

210 Data transmission device 220 Data reception device 252 Sequence giving means 254 Transmission decision means 256 Packet transmission means 260 Count means 262 Count stop means 264 Packet retransmission means 266 Cancel processing means 354 Packet reception means 356 Reception response means 358 Processing start means 360 Data Processing means S722 Packet retransmission step S724 Cancel processing step S730 Data processing step

Claims (33)

Data is divided into a plurality of packets, each is assigned a unique sequence number, the data transmission device transmits the packet according to the sequence number, and the packet transmitted from the data transmission device receives the data A data receiving device that transmits a reception completion signal to the transmitting device, receives a predetermined number of packet groups arranged in the sequence number, and then decodes the packet groups into data and starts processing the data; In the transmission system:
The data transmission device includes:
A packet retransmission means for retransmitting a packet having a sequence number that does not receive a reception completion signal at a predetermined first time interval;
Stop processing means for canceling retransmission of a packet having a sequence number that does not receive the reception completion signal within a predetermined second time period, and performing a predetermined process indicating the cancellation of retransmission;
With
The data receiving device is:
Data processing means for performing predetermined data processing in a state where the predetermined number of packet groups are not aligned in accordance with the predetermined processing;
A data transmission system comprising: The predetermined process is a process of shifting a sequence number of a packet to be transmitted after the second time by a predetermined value,
The data transmission system according to claim 1, wherein the data processing means detects the change of the predetermined value and performs the predetermined data processing. The predetermined process is a process of resetting a sequence number of a packet to be transmitted after the second time to a predetermined value,
The data transmission system according to claim 1, wherein the data processing means detects the reset to the predetermined value and performs the predetermined data processing. Sequence assigning means for dividing data into a plurality of packets and assigning unique sequence numbers;
Transmission determining means for determining a transmission order of the packets according to the sequence number;
Packet transmission means for transmitting packets to the data receiving device according to the transmission order of the packets;
Counting means for counting, for each packet, an elapsed time since the packet was first transmitted;
Count stopping means for stopping counting of packets corresponding to the reception completion signal received from the data receiving device;
Packet retransmission means for retransmitting a packet having a sequence number not receiving a reception completion signal at a predetermined first time interval using the counting means;
Stop processing means for canceling retransmission of a packet having a sequence number that does not receive the reception completion signal within a predetermined second time period, and performing a predetermined process indicating the cancellation of retransmission;
A data transmission device comprising:   5. The data transmission apparatus according to claim 4, wherein the predetermined process is a process of shifting a sequence number of a packet to be transmitted after the second time by a predetermined value.   6. The data transmission apparatus according to claim 5, wherein the predetermined value is a value that is substantially half of the maximum value of the sequence number.   5. The data transmission apparatus according to claim 4, wherein the predetermined process is a process of resetting a sequence number of a packet to be transmitted after the second time to a predetermined value.   The data transmission device according to claim 7, wherein the predetermined value is 0 (zero).   5. The data transmission apparatus according to claim 4, wherein the predetermined processing sets a flag indicating that retransmission is stopped in a packet transmitted after the second time.   5. The data transmission device according to claim 4, wherein the predetermined process transmits another packet indicating cancellation of retransmission after the second time.   11. The data transmission apparatus according to claim 10, wherein the cancellation processing unit transmits the another packet at a reduced packet transmission rate.   5. The data transmission apparatus according to claim 4, wherein the predetermined process hits a beacon indicating cancellation of retransmission after the second time.   5. The data transmission apparatus according to claim 4, wherein the predetermined processing temporarily stops transmission of subsequent packets after the second time and restarts transmission after a predetermined period.   5. The data transmission apparatus according to claim 4, wherein the data is moving image data expressing a real-time image operation. Computer
Sequence assigning means for dividing data into a plurality of packets and assigning unique sequence numbers;
Transmission determining means for determining a transmission order of the packets according to the sequence number;
Packet transmission means for transmitting packets to the data receiving device according to the transmission order of the packets;
Counting means for counting, for each packet, an elapsed time since the packet was first transmitted;
Count stopping means for stopping counting of packets corresponding to the reception completion signal received from the data receiving device;
Packet retransmission means for retransmitting a packet having a sequence number not receiving a reception completion signal at a predetermined first time interval using the counting means;
Stop processing means for canceling retransmission of a packet having a sequence number that does not receive the reception completion signal within a predetermined second time period, and performing a predetermined process indicating the cancellation of retransmission;
A computer program characterized by functioning as a function. Sequence assigning means for dividing data into a plurality of packets and assigning unique sequence numbers;
Transmission determining means for determining a transmission order of the packets according to the sequence number;
Packet transmission means for transmitting packets to the data receiving device according to the transmission order of the packets;
Counting means for counting, for each packet, an elapsed time since the packet was first transmitted;
Count stopping means for stopping counting of packets corresponding to the reception completion signal received from the data receiving device;
Packet retransmission means for retransmitting a packet having a sequence number not receiving a reception completion signal at a predetermined first time interval using the counting means;
Cancellation processing means for canceling transmission of the next and subsequent packets when a buffer used at the time of transmission of the packet exceeds a predetermined capacity and performing predetermined processing indicating the cancellation of transmission;
A data transmission device comprising:   The data transmission device according to claim 16, wherein the cancellation processing unit further clears input data of the buffer. Computer
Sequence assigning means for dividing data into a plurality of packets and assigning unique sequence numbers;
Transmission determining means for determining a transmission order of the packets according to the sequence number;
Packet transmission means for transmitting packets to the data receiving device according to the transmission order of the packets;
Counting means for counting, for each packet, an elapsed time since the packet was first transmitted;
Count stopping means for stopping counting of packets corresponding to the reception completion signal received from the data receiving device;
Packet retransmission means for retransmitting a packet having a sequence number not receiving a reception completion signal at a predetermined first time interval using the counting means;
Cancellation processing means for canceling transmission of the next and subsequent packets when a buffer used at the time of transmission of the packet exceeds a predetermined capacity and performing predetermined processing indicating the cancellation of transmission;
A computer program characterized by functioning as a function. A packet receiving means for receiving a packet transmitted from the data transmitting device;
Reception response means for transmitting a reception completion signal to the data transmission device in response to reception of the packet;
Processing start means for receiving a predetermined number of packet groups arranged in sequence number order and then decoding the packet groups into data to start processing the data;
Data processing means for performing predetermined data processing in a state where the predetermined number of packet groups are not aligned in accordance with predetermined processing in the data transmitting device;
And a data receiving device. The predetermined process is a process for shifting the sequence number of the packet by a predetermined value,
The data receiving device according to claim 19, wherein the data processing means detects the change of the predetermined value and performs the predetermined data processing.   21. The data processing means performs the predetermined data processing by detecting that the predetermined value has shifted more than approximately a quarter value of the maximum value of the sequence number. The data receiving device described in 1. The predetermined process is a process of resetting the sequence number of the packet to a predetermined value,
The data receiving device according to claim 19, wherein the data processing means detects the reset to the predetermined value and performs the predetermined data processing.   23. The data receiving apparatus according to claim 22, wherein the data processing means detects that the sequence number is 0 (zero) and performs the predetermined data processing. The predetermined process is a process of setting a flag indicating that retransmission of a packet to be transmitted next is stopped,
The data receiving device according to claim 19, wherein the data processing means performs the predetermined data processing when the flag is set in the received packet. The predetermined process is a process of transmitting another packet having a different frame,
The data receiving device according to claim 19, wherein the data processing means receives the another packet and performs the predetermined data processing. The predetermined process is a process of hitting a beacon indicating suspension of retransmission,
The data receiving device according to claim 19, wherein the data processing means receives the beacon and performs the predetermined data processing. The predetermined processing is processing for stopping transmission of the packet for a certain period of time,
20. The data receiving apparatus according to claim 19, wherein the data processing means detects that no packet is received for a certain period of time and performs the predetermined data processing.   The data receiving apparatus according to claim 19, wherein the data is moving image data expressing a real-time image operation. Computer
A packet receiving means for receiving a packet transmitted from the data transmitting device;
Reception response means for transmitting a reception completion signal to the data transmission device in response to reception of the packet;
Processing start means for receiving a predetermined number of packet groups arranged in sequence number order, then decoding the packet groups into data and starting processing of the data;
Data processing means for performing predetermined data processing in a state where the predetermined number of packet groups are not aligned in accordance with predetermined processing in the data transmitting device;
A computer program characterized by functioning as Data is divided into a plurality of packets, each is assigned a unique sequence number, the data transmission device transmits the packet according to the sequence number, and the packet transmitted from the data transmission device receives the data A data reception device that transmits a reception completion signal to a transmission device, receives a predetermined number of packet groups arranged in the sequence number sequence, and then decodes the packet groups into data and starts processing the data. Data transmission method:
The data transmitting device is
A packet retransmission step of retransmitting a packet with a sequence number that does not receive a reception completion signal at a predetermined first time interval;
A cancellation processing step of canceling retransmission of a packet with a sequence number that does not receive the reception completion signal within a predetermined second time period and performing a predetermined process indicating the cancellation of retransmission;
The data receiving device is
A data processing step of performing predetermined data processing in a state where the predetermined number of packet groups are not aligned in accordance with the predetermined processing;
A data transmission system comprising: The predetermined process is a process of shifting a sequence number of a packet to be transmitted after the second time by a predetermined value,
The data transmission method according to claim 30, wherein the data processing step performs the predetermined data processing by detecting a change in the predetermined value. The predetermined process is a process of resetting a sequence number of a packet to be transmitted after the second time to a predetermined value,
The data transmission method according to claim 30, wherein the data processing step detects the reset to the predetermined value and performs the predetermined data processing. Data is divided into a plurality of packets, each is assigned a unique sequence number, the data transmission device transmits the packet according to the sequence number, and the packet transmitted from the data transmission device receives the data A data reception device that transmits a reception completion signal to a transmission device, receives a predetermined number of packet groups arranged in the sequence number sequence, and then decodes the packet groups into data and starts processing the data. Data transmission method:
The data transmitting device is
A packet retransmission step of retransmitting a packet with a sequence number that does not receive a reception completion signal at a predetermined first time interval;
A cancellation processing step of canceling transmission of the next and subsequent packets when a buffer used at the time of transmission of the packet exceeds a predetermined capacity, and performing predetermined processing indicating the cancellation of transmission;
The data receiving device is
A data processing step of performing predetermined data processing in a state where the predetermined number of packet groups are not aligned in accordance with the predetermined processing;
A data transmission method comprising:

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