JP3638939B2 - Header restoration apparatus and header restoration method - Google Patents

Description

  The present invention relates to a header compression method performed at the time of packet transmission, and more particularly to a header compression method that makes a request for updating reference information when an error occurs during packet transmission.

  At present, typical transmission protocols for performing data transmission on the Internet include Transmission Control Protocol (TCP) / IP (Internet Protocol) and UDP (User Datagram Protocol) / IP. When data is transmitted using these transmission protocols on a low to medium bit rate transmission path, there is a problem of communication overhead due to a large header size such as TCP, UDP, and IP. Sometimes. For example, when 10-byte data is transmitted by UDP / IP, the total size of UDP / IP including the 10-byte data portion is 38 bytes, which is about four times the data to be actually transmitted. If this happens frequently, the effective speed of the transmission path is significantly reduced as a result.

  As a technique for reducing the overhead due to such a header, V.V. There is a Jacobson header compression method. In this header compression method, only the fields changed from the previous packet are transmitted in the headers of successive packets. Actually, since there are few portions where the contents have changed, the header can be compressed and the packet can be transmitted. However, this method is a header compression method defined for a wired section as shown in FIG. 5, and is not efficient in a transmission path in which errors frequently occur.

  FIG. 6 is a diagram showing a communication network for a wireless terminal of a mobile phone network (W-CDMA or the like) whose number of subscribers has increased significantly in recent years. Such a cellular phone network includes a wireless transmission section in which errors frequently occur as described above. As an overhead reduction method using a header for a wireless section having a feature that transmission errors frequently occur in this way, a header compression method using ROHC (RObust Header Compression), which is being discussed by IETF (Internet Engineering Task Force), can be cited. The header compression method by ROHC is described in detail in “draft-ietf-rohc-rtp-00.txt (29 June 2000)”.

  In the header compression method using ROHC, reference information shared by both the transmission side (compression side) and the reception side (reconstruction side) is provided for data compression / decoding. That is, the reference information used for data compression on the transmission side is also used for data restoration on the reception side. By sharing reference information in this way, data restoration can be performed correctly. FIG. 7 is a diagram showing an example of data transmission for performing such header compression method by ROHC.

In FIG. 7, when data transmission is started, the transmission side and the reception side hold the correct reference information α. First, consider a case where the transmission side transmits the header H1 and the data D1 to the reception side. The transmission side performs data compression on the header H1 using the reference information α. Here, the relationship between the header H1 and the compressed header H′1 transmitted to the receiving side through data compression can be expressed as the following equation (1).
P1 = H1 * α (1)

  In the above equation (1), the calculation method represented by the calculation symbol * differs for each compression target information area. For example, when the compression target area is a UDP port number, it is unchanged, and when it is an RTP sequence number, it usually increases by 1 and when it is an RTP time stamp, it increases by 50.

  Thus, the reference information α includes all information necessary for compression for each information area as described above. Therefore, as long as the reference information α remains the same as that on the transmission side and is correctly held on the reception side, the reception side can correctly restore the received compressed header H′1 to the original header H1. Thus, the receiving side can correctly receive the header H1 and the data D1. Further, the header H2 and the data D2 to the header H4 and the data D4 are also transmitted in the same manner with the headers compressed using the reference information α.

  Next, consider the case where the reference information changes. FIG. 8 is a diagram illustrating an example of data transmission when the reference information changes in the middle. In FIG. 8, after transmitting the header H2 and the data D2, the reference information is changed from α to β, and the header H3 is compressed using the changed reference information β.

  For example, suppose that the RTP time stamp of the header to be transmitted has increased by 50, but has changed to increase by 100 when data D3 is transmitted. At this time, the transmitting side changes the reference information α (contents “increase RTP time stamp by 50”) held so far to β (contents “increase RTP time stamp by 100”). For updating such reference information, as shown in FIG. 8, reference update information further added to the compressed header to be transmitted (here, header H'3) is used. The receiving side updates the reference information based on this reference update information.

  Note that the reference information may be updated without explicitly transmitting the reference update information. A brief description is given below. In the compressed header, 4 bits are prepared for the sequence number. With 4 bits, integers up to 15 can be represented, but integers greater than 16 cannot be represented. Therefore, an integer N greater than or equal to 16 is expressed by Nmod16. Therefore, every time the received sequence number changes from the maximum value (here 15) to the minimum value (here 0), L is incremented by 1 and L * 16 + (received sequence number) is set. By calculating, the sequence number is calculated. In this method, the update information is not explicitly transmitted, but it can be considered that the reference information is updated on both the transmission side and the reception side when the sequence number exceeds the maximum value. .

  The header restoration method as described above can be realized by the following header restoration device. FIG. 9 is a block diagram showing a configuration of a header restoration device that realizes the header restoration method shown in the conventional example.

  In FIG. 9, the header restoration device 1007 includes a packet output unit 1001, an error detection unit 1002, a header restoration unit 1003, a packet reception unit 1004, a reference information management unit 1005, and an update request unit 1006.

  The packet receiving unit 1004 outputs the header-compressed packet sent from the transmitting side to the header restoring unit 1003. The header restoration unit 1003 refers to the reference information managed by the reference information management unit 1005, restores the compressed header, and outputs it to the error detection unit 1002. If reference update information is added to the compressed header, the header restoration unit 1003 updates the reference information managed by the reference information management unit 1005. The error detection unit 1002 detects an error in the packet whose header has been restored, and outputs the packet that has been correctly restored to the packet output unit 1001. Packets that could not be correctly restored are discarded. The update request unit 1006 receives the error notification detected by the error detection unit 1002 and transmits an update request to the transmission side. According to “draft-ietf-rohc-rtp-00.txt (29 June 2000)” described above, the update request unit 1006 specifically transmits a NACK packet. The reference information management unit 1005 manages reference information for header restoration. The packet output unit 1001 outputs the packet with the header restored.

  Thus, the header decompression device 1007 detects an error in the compressed header. Here, typically, a CRC (Cyclic Redundancy Code) for determining whether or not there is an error in the header-restored packet is added to the compressed header. Therefore, if an error occurs due to noise or the like during wireless transmission in the compressed header or payload, this can be detected and an erroneous packet can be discarded.

  FIG. 10 is a diagram illustrating an example of data transmission in which an error occurs due to noise during wireless transmission. In FIG. 10, during transmission of header H'2 and data D2 obtained by header compression of header H2 in a wireless section or the like, the compressed header H'2 is affected by noise or the like and an error occurs. In the figure, it is indicated by a dotted x. Therefore, as indicated by a solid x mark in the figure, the header is not correctly restored on the receiving side, and the entire packet is discarded.

  In addition, an error during transmission can naturally occur in a compressed header to which reference update information is added. FIG. 11 is a diagram illustrating an example in which an error occurs in a header to which reference update information is added, and the reference information is updated erroneously. In FIG. 11, the reference update information added to the compressed header H′3 is affected by noise or the like while the header H′3 obtained by header compression of the header H3 and the data D3 are transmitted in the wireless section or the like, and the contents thereof change. doing. In the figure, it is indicated by a dotted x. Therefore, on the receiving side, the reference information is erroneously updated based on the changed reference update information β ′. Therefore, the header H3 restored by referring to the incorrect reference information is not subjected to header compression on the transmitting side. This is different from the header H3. Further, the same applies to the headers H4 and subsequent transmitted thereafter. Therefore, as indicated by a solid line X in the figure, an error occurs because the header is not correctly restored on the receiving side, and the entire packet is usually discarded.

  However, in exceptional cases, if the header is not correctly restored, an error may not occur and the packet may not be discarded. FIG. 12 is a diagram showing that there is a packet that does not cause an error even when the reference information is updated by mistake. In FIG. 12, since the reference information on the receiving side is erroneously updated to α ′ different from the reference information α on the transmitting side, the headers H1 and H2 are erroneously restored on the receiving side. Therefore, a CRC error occurs because the header is not correctly restored, and the entire packet is discarded. However, since it is impossible in principle to detect all errors in the CRC, a header restored in error may be determined to be correct by chance. In FIG. 12, the header H3 and the data D3 are packets that have been accidentally determined to be correct and have not been discarded.

  As described above, even if a single error is detected, it is possible to determine whether the single error is a restoration error based on noise or a restoration error based on incorrect reference information. Can not. Therefore, according to the conventional example described above, an update request (typically NACK) is transmitted every time an error occurs. However, even if the reference information is correct and an error due to noise has occurred, an unnecessary update request is transmitted. Therefore, according to the conventional example, the more errors due to noise, the more efficient the header compression. There is a problem of getting worse.

  Accordingly, an object of the present invention is to provide a header compression method for requesting reference information update without making an unnecessary update request in accordance with an error state of a packet whose header has been restored.

In order to achieve the above object, the present invention has the following features.
First invention receives a packet including a header compressed according to the reference information, a header decompression apparatus that performs restore compressed header by using the reference information, stores and manages references information A reference information management unit, a header restoration unit that restores a compressed header with reference to the reference information stored in the reference information management unit by receiving a received packet, and a header restoration unit and an error detector for detecting a restoration error packet including a header with a number based on the presence or absence of errors detected by the error detection unit, consecutive packets errors about packet including a header header decompressor is restored there a counting storage unit for counting the number of consecutive no error packets, based on the two values counting storage unit counts, further references information stored in the reference information management unit And wherein the obtaining Bei an update request unit to send an update request for requesting.

  The second invention is an invention subordinate to the first invention, wherein the count storage unit counts and stores the number of consecutive times X of the errored packets detected by the error detection unit, A continuous restoration success counting unit that counts and stores the number Y of consecutive packets without error detected by the error detection unit after the counting by the continuous restoration error counting unit is stopped, and the update request unit includes a count storage unit The reference information stored in the reference information management unit is determined to be updated based on the values of X and Y counted by.

  The third invention is an invention subordinate to the second invention, and the update request unit updates the reference information stored in the reference information management unit when the relationship between X and Y is X ≧ Y. It is characterized by determining that it is necessary.

A fourth invention receives a packet including a header compressed according to the reference information, a header decompression method for the restoration of the compressed header by using the reference information, the inputted received packet A header restoration step for restoring the compressed header with reference to the stored reference information, an error detection step for detecting a restoration error of the packet including the restored header, and an error detection step. It was based on the presence or absence of an error, and counting steps of counting the number of the number of errors is continuous without consecutive packets of a packet error for a packet that contains the restored header there are counted in the counting step based on the two values, and an update requesting step of sending an update request for requesting update of the reference information stored.

  The fifth invention is an invention subordinate to the fourth invention, wherein the counting storage step counts and stores the number of consecutive times X of the packets with errors detected in the error detection step, and stores them. And a continuous restoration success counting step that counts and stores the number of consecutive times Y of the error-free packets detected in the error detection step after the counting is stopped by the continuous restoration error counting step, It is characterized in that it is determined whether or not the stored reference information needs to be updated based on the values of X and Y counted in the storing step.

  The sixth invention is an invention subordinate to the fifth invention, and the update request step needs to update the stored reference information when the relationship between X and Y is X ≧ Y. It is characterized by determining.

A seventh invention receives a packet including a header compressed according to the reference information, the computer system to restore a compressed header by using the reference information, is inputted received packets, stores A header restoration step for restoring a compressed header with reference to the reference information, an error detection step for detecting a restoration error of a packet including the restored header, and an error detected by the error detection step. based on the presence or absence, it restored and counting steps of counting the number of the number of errors is continuous without packet consecutive error there packet relates to packet including a header, two values that are counted in the counting step based on, up to and update requesting step, to be executed to send an update request for requesting update of the reference information stored A computer-readable recording medium recording a gram.

  The eighth invention is an invention subordinate to the seventh invention, wherein the counting storage step counts and stores the number of consecutive times X of the packets with errors detected in the error detection step and stores them. And a continuous restoration success counting step that counts and stores the number of consecutive times Y of the error-free packets detected in the error detection step after the counting is stopped by the continuous restoration error counting step, It is a computer-readable recording medium characterized by determining whether or not it is necessary to update stored reference information based on the values of X and Y counted in the storing step.

A ninth invention receives a packet including a header compressed according to the reference information, the computer system to restore a compressed header by using the reference information, is inputted received packets, stores A header restoration step for restoring a compressed header with reference to the reference information, an error detection step for detecting a restoration error of a packet including the restored header, and an error detected by the error detection step. based on the presence or absence, it restored and counting steps of counting the number of the number of errors is continuous without packet consecutive error there packet relates to packet including a header, two values that are counted in the counting step based on professional for executing an update requesting step of sending an update request for requesting update of the reference information stored It is a lamb.

  A tenth invention is an invention dependent on the ninth invention, wherein the counting storage step counts and stores the number of consecutive times X of the errored packets detected in the error detection step and stores them. And a continuous restoration success counting step that counts and stores the number of times the error-free packet detected in the error detection step continues after the count is stopped by the continuous restoration error counting step. The program is characterized by determining whether or not the stored reference information needs to be updated based on the values of X and Y counted in the storing step.

  As described above, according to the present invention, since the update request unit determines whether or not the reference information needs to be updated based on the information on the presence or absence of the error counted by the count storage unit, the reference information error By reducing the number of discarded packets caused by the packet, it is possible to efficiently transmit the packets. Further, according to the present invention, an update request is sent to the transmission side according to the number of restoration errors that occur continuously on the reception side and the number of restoration successes. As a result, the number of discarded packets due to an error in reference information can be reduced and packets can be transmitted efficiently. Furthermore, according to the present invention, when there is a relationship of at least X ≧ Y, there are many continuous restoration errors, so it can be said that there is a high possibility that there is an error in the reference information. Packets can be transmitted efficiently by reducing the number of discarded packets.

(First embodiment)
The header compression method according to the first embodiment of the present invention is realized by a header compression apparatus and a header decoding apparatus as shown in FIGS. Hereinafter, the configuration of each apparatus will be described with reference to these drawings.

  FIG. 1 is a block diagram showing the configuration of the header compression device 607. In FIG. 1, the header compression device 607 includes a packet input unit 601, a CRC addition unit 602, a header compression unit 603, a packet transmission unit 604, a reference information management unit 605, and an update request reception unit 606.

  The packet input unit 601 outputs the input packet to the CRC adding unit 602. The CRC adding unit 602 adds a CRC to the input packet and outputs it to the header compression unit 603. The header compression unit 603 compresses the header of the input packet with reference to the reference information managed by the reference information management unit 605, and outputs the compressed packet header to the packet transmission unit 604. Note that how the header is compressed will be described later. The packet transmission unit 604 transmits the input header-compressed packet to the reception side. The reference information management unit 605 manages reference information used by the header compression unit 603. The update request reception unit 606 receives an update request from the transmission side and notifies the reference information management unit 605 of the update request. Upon receiving the notification, the reference information management unit 605 outputs the reference information managed to the header compression unit 603 and instructs it to be added to the compressed header.

  FIG. 2 is a block diagram illustrating a configuration of the header restoration device 709. In FIG. 2, a header restoration device 709 includes a packet output unit 701, an error detection unit 702, a header restoration unit 703, a packet reception unit 704, a continuous restoration error count unit 705, a continuous restoration success count unit 706, A reference information management unit 707 and an update request unit 708 are provided.

  The packet reception unit 704 receives the header-compressed packet sent from the transmission side, and outputs the packet to the header restoration unit 703. The header restoration unit 703 restores the compressed header with reference to the reference information managed by the reference information management unit 707 and outputs the header to the error detection unit 702. The error detection unit 702 detects a CRC error of the packet whose header has been restored, and outputs only the packet that has been correctly restored to the packet output unit 701. The continuous restoration error count unit 705 counts the number of consecutive errors detected by the error detection unit 702. The continuous restoration success count unit 706 counts the number of consecutive restoration successes detected by the error detection unit 702. The update request unit 708 refers to the count numbers of the continuous restoration error count unit 705 and the continuous restoration success count unit 706 to determine the necessity of the update request as will be described later, and sends the update request to the transmission side as necessary. Send. The reference information management unit 707 manages reference information for header restoration.

  In the present invention, the continuous state as described above refers to a case where an error state continues two or more times, or a case where an error-free state continues two or more times, or an error state occurs once. Or a case where there is only one error-free state.

  The operations of the header compression apparatus and header decompression apparatus according to this embodiment configured as described above will be specifically described below. It is assumed that the input packet is a packet in which an RTP / UDP / IP header is added to video or audio data.

  First, a specific operation of the header compression device 607 in FIG. 1 will be described. The packet input unit 601 outputs an RTP / UDP / IP packet input from the outside to the CRC adding unit 602. The CRC adding unit 602 calculates a CRC for the entire packet and adds it to the packet.

  The header compression unit 603 performs header compression using the reference information managed by the reference information management unit 605. In the header compression performed here, when header restoration can be performed from the sequence number, the reference information is not updated and only the sequence number is used as the header. If the header cannot be restored from the sequence number, the sequence number is used as the header together with the update information of the header information. The packet transmission unit 604 transmits the packet compressed in this way to the reception side.

  The reference information management unit 605 stores and manages reference information used by the header compression unit 603. If the header compression unit 603 updates the reference information, the reference information management unit 605 updates the accumulated reference information. If there is a notification from the update request reception unit 606 that the update request has been received, the reference information management unit 605 instructs the header compression unit 603 to add the update information to the header.

  The update request receiving unit 606 receives an update request issued from the receiving side. When receiving the update request, the update request receiving unit 606 notifies the reference information management unit 605 that the update request has been received.

  Next, a specific operation of the header restoration device 709 in FIG. 2 will be described. The packet reception unit 704 receives the header compressed packet transmitted from the packet transmission unit 604 in FIG. 1 and outputs it to the header restoration unit 703.

  The header restoration unit 703 refers to the reference information in the reference information management unit 707 and restores the header of the header-compressed packet. The packet whose header is restored is output to the error detection unit 702. When update information of reference information is added to the header, the header restoration unit 703 notifies the reference information management unit 707 of the update information.

  The error detection unit 702 checks the presence or absence of an error in the header-restored packet using the CRC. Furthermore, the error detection unit 702 notifies the continuous restoration error count unit 705 and the continuous restoration success count unit 706 of the presence or absence of an error. The error detection unit 702 discards the packet when an error is detected, and outputs the packet to the packet output unit 701 by removing the CRC from the packet when no error is detected. The packet output unit 701 outputs RTP / UDP / IP packets for which no error has been detected to the outside.

  The reference information management unit 707 stores and manages reference information necessary for restoring the header. When the reference information is included in the compressed header, the reference information management unit 707 updates the stored reference information using the new reference information notified from the header restoration unit 703.

  The continuous restoration error count unit 705 counts the number of consecutive errors X based on the presence / absence of an error notified from the error detection unit 702. For example, X is 1 when an error is detected in a certain packet, and X is 2 when an error is detected in a subsequent packet. Further, when an error is subsequently detected, X increases by 1 from 3, but if no error is detected in the packet, the continuity is cut off and the count stops.

  The continuous restoration success counting unit 706 counts the number Y of successive restoration successes based on the presence / absence of an error notified from the error detection unit 702. For example, Y is 1 when no error is detected in a certain packet, and Y is 2 when no error is detected in subsequent packets. Further, when no error is subsequently detected, Y increases by 1 from 3. However, when an error is detected in the packet, the continuity is interrupted and the count stops.

  The update request unit 708 determines whether or not an update request is to be made by combining the output X of the continuous restoration error count unit 705 and the output Y of the continuous restoration success count unit 706 together. This determination operation will be described in more detail with reference to FIG.

  FIG. 3 is a diagram illustrating an example of restoration and the values of X and Y when packets P1 to P11 are received. In FIG. 3, it is assumed that a packet P12 (not shown) has a restoration error.

  In FIG. 3, when an error is detected in the packet P1, X = 1, but since no error is detected in the packet P2, X is held at 1 and Y = 1. Thereafter, no error is detected until packet P4, so X = 1 and Y = 3. Next, when an error is detected in the packet P5, a new combination corresponding to the presence or absence of a set of errors is obtained. Therefore, the values of X and Y from the packets P1 to P4 are set as one set, and X = 1 and Y = 3 are determined. Similarly, since errors are detected from the packets P5 to P8, X = 4, and since no errors are detected from the packets P9 to P11, Y = 3. Thereafter, when an error is detected in the packet P12, a new combination is established, so that X = 4 and Y = 3 are determined.

  In this way, the update request unit 708 compares the X and Y values with a predetermined value, with the continuous restoration error and the subsequent success in succession as a set. For example, when X is larger than 10 and Y is smaller than 2, it is determined that the reference information has an error, and the transmission side is requested to be updated. Of course, these predetermined values are merely examples, and are not limited thereto. However, it can be said that there is a high possibility that there is an error in the reference information because there are many consecutive restoration errors at least in the case of X ≧ Y.

  As described above, the header restoration device 709 according to the present embodiment makes an update request to the transmission side according to the number of restoration errors that occur continuously on the reception side and the number of restoration successes. As a result, the number of discarded packets due to an error in reference information can be reduced and packets can be transmitted efficiently.

(Second Embodiment)
The header compression method according to the second embodiment of the present invention is realized by a header compression device and a header decoding device as shown in FIGS. Therefore, the configuration of the header compression apparatus according to the second embodiment is the same as the configuration of the header compression apparatus 607 in FIG. Hereinafter, the configuration of the header decoding apparatus according to the present embodiment will be described with reference to FIG.

  FIG. 4 is a block diagram illustrating a configuration of the header restoration device 908. In FIG. 4, a header restoration device 908 includes a packet output unit 901, an error detection unit 902, a header restoration unit 903, a packet reception unit 904, a restoration error presence / absence storage unit 905, a reference information management unit 906, an update A request unit 907.

  The packet reception unit 904 outputs the header-compressed packet sent from the transmission side to the header restoration unit 903. The header restoration unit 903 restores the compressed header with reference to the reference information in the reference information management unit 906 and outputs the header to the error detection unit 902. The error detection unit 902 detects an error in the packet whose header has been restored, and outputs the correctly restored packet to the packet output unit 901. The restoration error presence / absence storage unit 905 counts and stores the presence / absence of errors in the packets detected by the error detection unit 902. The update request unit 907 receives the number counted in the restoration error presence / absence storage unit 905, determines the necessity of the update request as will be described later, and transmits the update request to the transmission side as necessary. The reference information management unit 906 manages reference information for header restoration.

  The operation of the header restoration apparatus according to this embodiment configured as described above will be specifically described below. The operation of the header compression apparatus 607 on the transmission side is the same as that in the first embodiment, and the RTP / UDP / IP header is added to the video and audio data in the same way for the input packet. Assume that it is a packet.

  4, the packet receiving unit 904 receives the header compressed packet transmitted from the packet transmitting unit 604 in FIG. 1 and outputs the header compressed packet to the header restoring unit 903.

  The header restoration unit 903 refers to the reference information in the reference information management unit 906, and restores the header of the header-compressed packet. The packet whose header is restored is output to the error detection unit 902. When update information of reference information is added to the header, the header restoration unit 903 outputs the update information to the reference information management unit 906.

  The error detection unit 902 checks the presence / absence of an error in the header-restored packet using the CRC. Furthermore, the error detection unit 902 notifies the restoration error presence / absence storage unit 905 of the presence / absence of an error. Further, the error detection unit 902 discards the packet when an error is detected, and outputs the packet to the packet output unit 901 by removing the CRC from the packet when no error is detected. The packet output unit 901 outputs RTP / UDP / IP packets for which no error has been detected to the outside.

  The reference information management unit 906 stores and manages reference information necessary for restoring the header. When the reference information is included in the compressed header, the reference information management unit 906 updates the stored reference information using the new reference information notified from the header restoration unit 903.

  Based on the presence / absence of an error notified from the error detection unit 902, the restoration error presence / absence storage unit 905 typically stores the number R of errors of the past W packets.

  The update request unit 907 compares the values of W and R output from the restoration error presence / absence storage unit 905 with a predetermined value to determine whether or not to make an update request. For example, if 45 of the past 50 packets are in error, the transmission side is requested to update, assuming that there is an error greater than a predetermined value. That is, when W = 50 and R> = 45, it is assumed that there is an error in the reference information, and an update is requested to the transmission side. Of course, the predetermined value mentioned above is only an example, and is not limited thereto.

  As described above, the header restoration device 908 according to the present embodiment makes an update request to the transmission side when the number of restoration errors increases in the packets received in the past on the reception side. As a result, the number of discarded packets due to an error in reference information can be reduced and packets can be transmitted efficiently.

  INDUSTRIAL APPLICABILITY The present invention can be used in a system in which packet header compression by a transmission side and packet header restoration by a reception side are performed using the same reference information, and particularly when an error occurs in packet transmission This is suitable when the side requests the reference side to update the reference information.

The block diagram which showed the structure of the header compression apparatus 607 which concerns on 1st Embodiment. The block diagram which showed the structure of the header decompression | restoration apparatus 709 which concerns on 1st Embodiment The figure which illustrated the mode of restoration, and the value of X and Y when packet P1 to packet P11 were received The block diagram which showed the structure of the header decompression | restoration apparatus 908 which concerns on 2nd Embodiment. Diagram for explaining header compression section in cable The figure for demonstrating the header compression area in radio | wireless The figure which showed the data transmission example which performs the header compression system by the conventional ROHC The figure which showed the data transmission example when reference information changes in the middle in the conventional header compression The block diagram which shows the structure of the header decompression | restoration apparatus which implement | achieves the header decompression | restoration method shown by the prior art example A diagram showing an example of data transmission in which errors occur due to noise during wireless transmission in conventional header compression A diagram showing an example in which an error occurs in a header to which reference update information is added and the reference information is erroneously updated in conventional header compression. Figure showing that there is a packet that does not cause an error even if the reference information is updated by mistake in conventional header compression

Explanation of symbols

601 Packet input unit 602 CRC addition unit 603 Header compression unit 604 Packet transmission unit 605, 906, 1005 Reference information management unit 606 Update request reception unit 607 Header compression device 701, 901, 1001 Packet output unit 702, 902, 1002 Error detection unit 703, 903, 1003 Header restoration unit 704, 904, 1004 Packet reception unit 705 Continuous restoration error count unit 706 Continuous restoration success count unit 707 Reference information management unit 708, 907, 1006 Update request unit 709, 908, 1007 Header restoration device 905 Restore error presence / absence storage

Claims (10)

A header restoration device that receives a packet including a header compressed based on reference information and restores the compressed header using the reference information ,
And reference information management unit for storing and managing the pre-Symbol reference information,
A header restoration unit that receives a received packet and refers to reference information stored in the reference information management unit to restore a compressed header;
An error detection unit for detecting a restoration error of a packet including the header restored by the header restoration unit ;
A count storage unit that counts the number of consecutive packets with errors and the number of consecutive packets without errors based on the presence or absence of errors detected by the error detection unit. When,
Based on two values where the count storing unit counts, and wherein the obtaining Bei an update request unit to send an update request for requesting update of the reference information stored in the reference information management unit, Header decompressor. The counting storage unit
A continuous restoration error count unit that counts and stores the number X of consecutive packets with errors detected by the error detection unit;
A continuous restoration success counting unit that counts and stores the number of times the error-free packet detected by the error detection unit continues after the counting is stopped by the continuous restoration error counting unit,
The update request unit determines whether or not the reference information stored in the reference information management unit needs to be updated based on the values of X and Y counted by the count storage unit. The header restoration device according to claim 1.   The update request unit determines that the reference information stored in the reference information management unit needs to be updated when the relationship between X and Y is X ≧ Y. The header decompression device according to claim 1. A header restoration method for receiving a packet including a header compressed based on reference information and restoring the compressed header using the reference information ,
Is inputted received packets, by referring to the reference information stored, and header decompression step of restoring the compressed header,
An error detection step for detecting a recovery error of the packet including the recovered header;
Based on the presence or absence of an error detected by said error detecting step, a counting step for counting the number of the number of errors is continuous without packet consecutive error there packets for packets containing the reconstructed header,
On the basis of the two values to be counted in the counting step, to send an update request for requesting update of the reference information stored including the update request step, a header recovery method. The counting storage step includes:
A continuous restoration error counting step for counting and storing the number of times X the packets with errors detected in the error detection step continue;
A continuous restoration success counting step that counts and stores the number of times Y that the error-free packets detected in the error detection step continue after counting is stopped by the continuous restoration error counting step;
5. The update request step determines whether or not the stored reference information needs to be updated based on the values of X and Y counted in the count storage step. The header restoration method described in 1.   6. The header restoration method according to claim 5, wherein the update requesting step determines that the stored reference information needs to be updated when the relationship between X and Y is X ≧ Y. . A computer system that receives a packet including a header compressed based on reference information and restores the compressed header using the reference information .
Is inputted received packets, by referring to the reference information stored, and header decompression step of restoring the compressed header,
An error detection step for detecting a recovery error of the packet including the recovered header;
Based on the presence or absence of an error detected by said error detecting step, a counting step for counting the number of the number of errors is continuous without packet consecutive error there packets for packets containing the reconstructed header,
Based on the two values to be counted in the counting step, to send an update request for requesting update of the reference information stored and updated requesting step, computer-readable recording a program for executing Recording medium. The counting storage step includes:
A continuous restoration error counting step for counting and storing the number of times X the packets with errors detected in the error detection step continue;
A continuous restoration success counting step that counts and stores the number of times Y that the error-free packets detected in the error detection step continue after counting is stopped by the continuous restoration error counting step;
The update request step determines whether or not the stored reference information needs to be updated based on the values of X and Y counted in the count storage step. A computer-readable recording medium described in 1. A computer system that receives a packet including a header compressed based on reference information and restores the compressed header using the reference information .
Is inputted received packets, by referring to the reference information stored, and header decompression step of restoring the compressed header,
An error detection step for detecting a recovery error of the packet including the recovered header;
Based on the presence or absence of an error detected by said error detecting step, a counting step for counting the number of the number of errors is continuous without packet consecutive error there packets for packets containing the reconstructed header,
On the basis of the two values to be counted in the counting step, an update requesting step of sending an update request for requesting update of the reference information stored, a program to be executed. The counting storage step includes:
A continuous restoration error counting step for counting and storing the number of times X the packets with errors detected in the error detection step continue;
A continuous restoration success counting step that counts and stores the number of times Y that the error-free packets detected in the error detection step continue after counting is stopped by the continuous restoration error counting step;
The update request step determines whether or not the stored reference information needs to be updated based on the values of X and Y counted in the count storage step. The program described in.

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