KR20110040514A - Method for improving header compression effeciency and packet transmitting apparatus for the same - Google Patents

Abstract

PURPOSE: A header compression improving method and a packet transmission apparatus are provided to increase the capacity of a relay line due to the increase of compression efficiency. CONSTITUTION: A packet transmission apparatus(100) includes a header regenerator(110) and an ROHC(Robust Header Compression) unit(120). The header regenerator determines the possibility of the ROHC of a mobile communications packet header. The header regenerator regenerates the mobile communications packet header. The ROHC unit performs the ROHC compression of a packet having the regenerated header.

Description

METHOD FOR IMPROVING HEADER COMPRESSION EFFECIENCY AND PACKET TRANSMITTING APPARATUS FOR THE SAME}

The present invention relates to a method for improving header compression efficiency and a packet transmitting apparatus, and more particularly, to a method for improving the efficiency of robust header compression (ROHC) used for the efficiency of a wireless section, and a mobile communication system therefor.

In general, IP (Internet Protocol) is a transport protocol typically used in a wired network as well as a wireless network. Existing services used in wireless networks were not suitable for real-time transmission due to limited bandwidth and relatively long round trip delay compared to wire. However, as the mobile communication system evolves, a mechanism for guaranteeing a certain quality of service (QoS) for each subscriber or service is provided, thereby providing real-time services such as voice over IP (VoIP), video telephony (VT), Various services and applications such as interactive games and messaging have begun to be demanded.

1 is a diagram illustrating a structure of a general wired and wireless IP network. One of the characteristics of these wired and wireless IP network services is that they have a header of RTP / UDP / IP and the header size is much larger than the payload size. 2 shows an example of IP overhead of a VoIP packet, and it can be seen that the RTP / UDP / IP header size is 2 to 4 times larger than the Enhanced Variable Rate CODEC (EVRC) full rate. By default, IP / UDP / RTP headers are added for VOIP services, and the header size is 40 bytes for IPv4 and 80 bytes for IPv6, resulting in several to tens of times larger overhead than the payload size. It can be seen that.

However, in the end-to-end connection that constitutes multiple hops, such RTP / UDP / IP header information is very important, but a hop-to-hop single link, i.e. For example, between the terminal and the base station, this header information is not very important information and consists of information that can be easily inferred even if it is not delivered. Therefore, in order to compress RTP / UDP / IP headers of some real time services such as VoIP and gaming, mobile communication standards such as CDMA, WCDMA and LTE may provide ROHC (Robust Header Compression). It is defined to be. ROHC reduces the bandwidth of Air Network section by efficiently compressing these headers (RTP / UDP / IP, UDP / IP, ESP / IP, etc.) to efficiently use radio frequency (RF) resources. This algorithm is based on RFC3095 as an algorithm to reduce packet loss or reduce interactive response time.

Fields included in IPv4, IPv6, UDP, and RTP headers, depending on their characteristics, are fields that can be derived from other values, such as the size of the frame of the packet frame, the packet stream. STATIC field with a constant value during the lifetime of the C #) field, and a STATIC-DEF field that is generally statically treated as a field that defines the packet stream, such as the source IP address. It may be classified into a STATIC-KNOWN field that does not need to be transmitted or received as a well-known value, and a CHNAGING field having values that vary randomly within a specific range.

Between peers compressing and decompressing headers of IP / UDP / RTP using ROHC, various compression algorithms according to the characteristics of each field such as Window Based Least Significant Bit (LSB) compression method or Scaled RTP Time Stamp compression method Use However, in order to use this compression algorithm, the fields must have the characteristics of the aforementioned STATIC or INFERRED fields, and in the case where the changing pattern such as IRREGULAR cannot be distinguished and the value can not be deduced from other fields, Since no compression is possible, the field must be passed as-is without compression. In addition, some compressible fields have a problem in that compression efficiency is inferior because additional operations such as feeding back more frequently or periodically transferring the original values are necessary to derive the original values.

The present invention provides a method for improving the efficiency of robust header compression used for the efficiency of the radio section and a mobile communication system therefor.

The packet transmission apparatus of the present invention includes a header regeneration unit for determining whether ROHC (robust header compression) of a mobile communication packet header is possible and regenerating the mobile communication packet header when ROHC of the mobile communication packet header is impossible; And an ROHC compression unit that performs ROHC compression of the packet having the regenerated header.

In addition, the header compression efficiency improvement method of the present invention, a) determining whether or not robust header compression (ROHC) of the mobile packet header; b) regenerating the mobile packet header if ROHC of the mobile packet header is not possible; And c) performing ROHC compression of the packet with the regenerated header.

According to the present invention, the value of the packet header is partially changed, but there is no effect on the service, and the compression efficiency is increased, so that the capacity of the relay line or the wireless network can be substantially increased, and the loss in the wireless section is caused by the reduced header size. (Loss), etc. are less affected, and the packet transmission time can be shortened, thereby improving the quality of service.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in the following description, when there is a risk of unnecessarily obscuring the gist of the present invention, a detailed description of a widely known function or configuration will be omitted.

In case of performing header compression through ROHC (Robust Header Compression) in the mobile communication system, the characteristics of the header and the changing pattern of the header (Changing Pattern) are identified to perform proper header compression to transmit the packet, and Restore the original header value for the packet. Therefore, the header compression efficiency decreases when the characteristics and the changing aspects of the header cannot perform compression. The present invention provides a method of increasing compression efficiency by regenerating a header that is not compressed or has low compression efficiency in a compressible form in order to maximize header compression efficiency. However, the restored header value is changed differently from the original header value, but it does not affect the payload transmitted by the packet.

The better the ROHC compression efficiency, the better the quality of the service. This is caused by the delay or loss caused by data packet including the header. Considering the case of poor quality, as the header size decreases, the probability of packet corruption is reduced. Therefore, changing the shape of the header to increase the compression efficiency can further improve the quality of service.

3 is a block diagram showing a packet transmission apparatus according to an embodiment of the present invention, Figure 4 is a flow chart showing a header regeneration process according to an embodiment of the present invention. The packet transmission apparatus 100 includes a header regeneration unit 110 and a ROHC compression unit 120. The header regeneration unit 110 operates according to the following procedure.

1. Check whether the header regeneration unit 110 can be operated (S110)

The header regenerator 110 operates for each packet stream, that is, for each IP flow. IP flow is a term used in packet-based mobile communication systems such as CDMA EV-DO or LTE, and is classified by source IP, destination IP, source port, destination port, and profile.

The system operator may separately define in the system management software (S / W) whether to apply header regeneration to a packet stream of a specific service provided by the mobile communication system. For example, the header regeneration function can be enabled for the packet stream of the VoIP service, and the header regeneration function can be disabled for the packet stream of the gaming service. If the specific service provided by the mobile communication system is deactivated, the header regenerator 110 does not operate on the packet stream of the corresponding service.

2. Check the operation of ROHC (S120)

Since this process is a method for improving the ROHC compression efficiency, if the ROHC does not operate, the header regenerating unit 110 does not perform any operation. With this in mind, system administrators can specify that header regeneration is disabled for the service, and even if header regeneration is enabled, it is automatically disabled for services that do not have ROHC enabled. Can be.

3. Investigate the characteristics of the packet stream header (S130)

It is a process to check whether the headers such as IP / UDP / RDP included in the packet stream are suitable for compression. Therefore, only one packet stream can be used to determine the characteristics of the header. . Therefore, the header regeneration function does not operate on the packet stream transmitted before the characteristics of the header are known.

4. Header Regeneration Process (S140)

In the case of a packet stream including an RTP header, the ROHC generally carries all header fields through LSB (Least Significant Bit) encoding based on an RTP time stamp or sequence. Therefore, if compression is impossible, such as when the IP identifier has a random value, the value is changed so that the IP identifier has a value proportional to the time stamp or sequence value of the RTP header. In the case of a UDP checksum, if the value exists, the checksum is deactivated, that is, the checksum value is changed to zero. In this process, the characteristics of the headers should be changed within a range that does not affect the original data (Payload) transfer, so the header regeneration unit 120 should check the change of the header for each packet stream in the last step. .

The ROHC compression unit 120 receives a packet stream having the regenerated header from the header regeneration unit 110 and performs ROHC compression.

In the present embodiment, regeneration of an IP identifier and a UDP checksum is taken as an example, but all fields of various headers in an IP network such as IPv4, IPv6, RTP, and UDP may be the target of header regeneration. For example, a source IP or a source port number classified as a STATIC field may also be regenerated. In this case, the header regenerating unit 110 operates as if it is a receiver of a packet stream. That is, by removing all headers of the received packet stream and leaving only the payload, the receiver of the service receives the payload included in the packet stream. In order to send the payload of the corresponding packet stream to the original receiver, a header of a new RTP / UDP / IP is generated and transmitted to the original receiver through the ROHC. In other words, in this case, all headers are regenerated as part of the header regeneration. Of course, even in this case, the header to be regenerated must be regenerated so that ROHC can be most efficiently performed.

Table 1 below shows classification according to characteristics of IP / UDP / RTP headers.

Classification Explanation INFERRED Fields that can be inferred from other values
(ex, size of the frame) STATIC This field has a constant value during the lifetime of the packet stream. It must be exchanged with each other once. STATIC-DEF Field defining a packet stream, usually treated as "STATIC". (ex, Source IP Address) STATIC-KNOWN It does not need to be communicated to a well-know value. CHANGING Randomly varying values within a certain range.

The CHANGING field of Table 1 is divided into five subclasses as shown in Table 2 below.

Subclass Explanation field STATIC In general, a field that can be classified as "STATIC" or "CANGING" or some assumptions. IPv4 ID (Sequential),
UDP Checksum (Disabled),
RTP CSRC Count (No mix),
RTP Sequence Number SEMI-STATIC Most of them have a constant value, but they are changed from time to time and return to their original value after a certain number of packets. RTP Marker RARELY-CHANGNING Occasionally fields that change and keep their values IPv4 sequential jump,
IP TOS,
IP Traffic-Class,
RTP CSRC Count (mixed)
RTP Payload Type,
RTP Timestamp,
RTP CSRC List (mixed) ALTERNATING Fields repeated between different values IP TTL,
IP HOP Limit IREEGULAR Fields indistinguishable from the changing pattern IPv4 ID (Random),
UDP Checksum (Enabled),

5 is an exemplary view showing an IPv4 header according to an embodiment of the present invention, Figure 6 is an exemplary view showing an IPv6 header according to an embodiment of the present invention, Figure 7 is a UDP header according to an embodiment of the present invention 8 is an exemplary diagram and FIG. 8 is an exemplary diagram showing an RTP header according to an embodiment of the present invention.

Referring to FIG. 5, each field is classified as "STATIC" because the "VER" field is a field indicating an IP version and all packets have the same value. The "IHL" field indicates the header length of the IP header. If the header has no option, it is classified as "STATIC-KNOWN" because it has a certain value. If the header has a separate option, Are classified as "STATIC". The "Type of Service" field is classified as a "CHANGING" field but has a value that is constant or hardly changes during the lifetime of the packet stream. The "Packet Length" field is classified as "INFERRED" because it can be derived during packet transmission. The "Identification" field is classified as "CHANGING" and may be classified into three different forms according to the IP identifier assignment method. The "Flags" field is divided into 'Reserved Flag', 'Don`t fragment (DF) Flag', and 'More Fragment (MF) Flag'. 'Reserved Flag' should be set to 0, so it is classified as 'STATIC-KNOWN'. 'Don't fragment (DF) Flag' is classified as 'STATIC' because it has a constant value in the packet stream, and 'More Fragment (MF) Flag' is classified as 'STATIC-KNOWN' because it is fixed to 0. do. The "Frame Offset" field is classified as "STATIC-KNOWN" because it does not distribute packet data (no fragmentation). The "Time to Live" field is classified as "CHANGING" but has a constant value during the lifetime, and is composed of a value that is changed occasionally when a route change is made. The "Protocol" field is classified as "STATIC" because all packets of the packet stream have the same value. Since the "Header Checksum" field is almost all headers are compressed, the value of this field should be classified as "INFERRED" since the value of this field should be regenerated later. "Source & Destination Address" is classified as "STATIC-DEF" because it has the same value for all packets in the packet stream.

While the above methods have been described through specific embodiments, the methods may also be implemented as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which are also implemented in the form of carrier waves (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, codes, and code segments for implementing the above embodiments can be easily deduced by programmers of the present invention.

In addition, while the present invention has been described in connection with some embodiments, it is to be understood that various modifications and changes can be made without departing from the spirit and scope of the invention as will be understood by those skilled in the art. You will need to know It is also contemplated that such variations and modifications are within the scope of the claims appended hereto.

1 is an exemplary view showing the structure of a general wired and wireless IP network.

2 is an exemplary diagram showing IP overhead of a VoIP packet.

3 is a block diagram showing a packet transmission apparatus according to an embodiment of the present invention.

4 is a flowchart showing a header regeneration process according to an embodiment of the present invention.

5 is an exemplary view showing an IPv4 header according to an embodiment of the present invention.

6 illustrates an IPv6 header according to an embodiment of the present invention.

7 is an exemplary view showing a UDP header according to an embodiment of the present invention.

8 is an exemplary view showing an RTP header according to an embodiment of the present invention.

Claims (8)

A packet transmitter, A header regenerating unit for determining whether ROHC (robust header compression) of a mobile communication packet header is possible and regenerating the mobile communication packet header when ROHC of the mobile communication packet header is impossible; And ROHC compression unit performing ROHC compression of the packet having the regenerated header Packet transmission apparatus comprising a. The method of claim 1, wherein the header regeneration unit, Packet transmission apparatus operating in unit of packet stream for each mobile communication service. The method of claim 2, wherein the header regeneration unit, And determining whether the header regeneration unit is operable before determining whether the ROHC is possible. The method of claim 3, wherein the header regeneration unit, And regenerating the mobile communication packet header to have a value proportional to a time stamp or a sequence value of the mobile communication packet when ROHC of the mobile communication packet header is impossible. As a method for improving header compression efficiency, a) determining whether robust header compression (ROHC) of the mobile communication packet header is possible; b) regenerating the mobile packet header if ROHC of the mobile packet header is not possible; And c) performing ROHC compression of the packet with the regenerated header Header compression efficiency improvement method comprising a. The method of claim 5, wherein step b) A method of improving header compression efficiency performed in packet streams for each mobile communication service. The method of claim 6, wherein before step a), And determining whether the header regeneration unit is operable. The method of claim 7, wherein step b) And regenerating the mobile communication packet header to have a value proportional to a time stamp or sequence value of the mobile communication packet when ROHC of the mobile communication packet header is impossible.

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