KR100501713B1 - A Network system for transmitting packet with header compression and control method thereof - Google Patents

Abstract

A network system for transmitting a packet compressed with a header and a control method thereof are disclosed. The network according to the present invention applies a compression node and a predetermined decompression when decompressing a header of a packet to be transmitted and a transmitting node compressing a header of a packet to be transmitted based on a predetermined compression application context. If the contexts are inconsistent with each other, a receiving node that piggybacks the feedback message, which is the context mismatch information, is added to the MAC layer ACK signal corresponding to the reception of the packet transmitted after the transmission target packet. Include. According to the present invention, it is possible to promptly solve a problem caused by a context mismatch in a unidirectional service.

Description

A network system for transmitting a packet compressed with a header and a control method thereof

The present invention relates to a network system for transmitting a packet compressed with a header and a control method thereof. More particularly, the present invention relates to a network system for compressing a header of a packet transmitted in order to provide a unidirectional service and transmitting the same by using a ROHC method. It relates to a control method.

In recent years, IP (Internet Protocol) technology is rapidly developing, and in particular, in the public land mobile network (PLMN), IP technology has been activated by providing many advantages. However, in a mobile network, radio resources are limited and expensive, and radio resources should be used as effectively as possible.

Typically, the various header fields involved in IP-based protocols are very large, while the payload is relatively small. For example, when data is transmitted over an IPv4 (Internet protocol version 4) network, a packet header including data is 40 bytes in size. Here, 40 bytes means the sum of 20 bytes of IPv4 header, 8 bytes of User Data Protocol (UDP) header, and 12 bytes of routing table protocol (RTP) header. In addition, when data is transmitted over an IPv6 (Internet protocol version 6) network, the header length is 60 bytes. In this example, 40 bytes of IPv6 headers are used instead of 20 bytes of IPv4 headers. However, considering the fact that the data to be transmitted is voice data, the size is about 15 to 20 bytes, the header size of 40 bytes in the IPv4 network and 60 bytes in the IPv6 network corresponds to the overhead, resulting in unreasonable bandwidth. It results in wasting money. The problem may become more serious if such data transmission is performed under poor conditions of bit error rate (BER) of the air interface and round trip times (RTT) in the uplink and downlink directions.

As a solution to this problem, the Internet Engineering Task Force (IETF) has recently studied the header field compression method known as ROHC (ROrust Header Compression). ROHC is a protocol designed for compression of headers. The protocol is made with a focus on compression efficiency and robustness.

Generally, data transmission service is divided into one-way service and two-way service based on the flow of data.

In order to provide a bidirectional service by applying the ROHC method, a ROHC compression unit and a ROHC decompression unit are provided in each ROHC module of a terminal and an access point (AP) in a network system, respectively. This structure has the same forward and reverse channels due to the nature of the bidirectional service. In the case of the bidirectional channel structure, if compression and decompression in one direction fail, the result can be fed back to the channel in the opposite direction, so that error recovery can be performed quickly. Examples of two-way services include video telephony and Voice over IP (VoIP).

However, the ROHC module operating on a service having a unidirectional channel structure cannot recover the error quickly because there is no channel in the opposite direction to send feedback even if compression and decompression in one direction fails. The ROHC decompressor periodically retransmits the context, and the ROHC decompressor can recover the error only by receiving the retransmitted context. Therefore, there is a problem that error recovery is not as fast as the bidirectional channel structure. In order to describe this in more detail, a description will be given of a network system providing a unidirectional service by applying the ROHC method with reference to FIG. 1. The network system includes one or more APs and one or more terminals and transmits and receives data between them. In FIG. 1, the structure of the ROHC module operating in the unidirectional service is simplified. The AP 10 includes a first ROHC module 12 and a first MAC layer controller 14, and the first ROHC module 12 includes a first ROHC module 12. And a contact storage 12a and a ROHC compression section 12b. The terminal 20 includes a second ROHC module 22 and a second MAC layer controller 24, and the second ROHC module 22 includes a second context storage 22a and a ROHC decompression unit 22b. .

The first context storage unit 12a stores the compression application context, and the second context storage unit 22a stores the decompression application context. The context may be a criterion of compression and decompression and may include information identifying a data packet flow, such as serial numbers and IP addresses or time stamps of the data packets.

When transmitting predetermined data, the ROHC compression unit 12b performs a compression process based on the compression application context stored in the first context storage unit 12a. The header-compressed packet is transmitted to the second MAC layer control unit 24 of the terminal 20 via the first MAC layer control unit 14 of the AP 10, where a forward channel is used. The second MAC layer controller 24 transfers the transmitted packet to the ROHC decompression unit 22b, and the ROHC decompression unit 22b decompresses the header of the transmitted packet in the second context storage unit 22a. Decompress based on application context. In this case, the decompression application context is required to be identical to the compression application context, and the headers are normally decompressed only when they are identical. One-way services include video on demand (VOD), audio on demand (AOD), and various packet multicasting services.

The terminal-side context and the AP-side context must coincide, and when the context needs to be changed at both sides, information about the change must be transmitted to the other ROHC module. Through this method, the synchronization application context of the ROHC compression unit 12b and the decompression application context of the ROHC decompression unit 22b are synchronized. However, if there is an error in conveying information on the change of context and the two contexts do not coincide with each other, the successfully delivered packet may be malfunctioning of the second ROHC module 22, that is, the compression applied and decompressed applied context. There is a problem of discarding due to mutual inconsistency. Of course, such a problem may be solved by the ROHC decompressor transmitting a feedback message through the forward channel or the reverse channel in the case of the bidirectional service using the ROHC method.

However, in the unidirectional service structure, there is basically no channel corresponding to the reverse channel in the bidirectional service structure. Therefore, to compensate for the absence of such a reverse channel, an initialization and refresh (IR) process is introduced. That is, the IR process periodically transmits a context for the ROHC decompression unit 22b from the AP 10 to the terminal 20. The second context storage 22a updates and stores the periodically transmitted context.

FIG. 2 is a timing diagram illustrating a state in which a packet is transmitted from an AP to a terminal in a network system providing a unidirectional service by employing a conventional ROHC method.

Here, the solid line means a packet for transmitting data (hereinafter referred to as a 'data packet') and the dotted line indicates a packet for transmitting a context (hereinafter referred to as a 'context packet'). In addition, as described above, the IR process is performed at a predetermined cycle. In this figure, it is assumed that an IR process is performed after six data packets are transmitted.

1 and 2, the packet a is compressed by the ROHC in the AP 10 and transmitted to the terminal 20. In this case, the header of the packet a is normally decompressed because the compression applying context and the decompression applying context coincide with each other. Therefore, the data of packet a is processed normally.

The packet b is transmitted to the terminal 20 as a context packet. The transmitted context is updated and stored in the second context storage 22a shown in FIG. 1 to become a new decompression application context. In the case of the bidirectional service, that is, in the bidirectional mode, the success or failure of the transmission of the context packet is notified through a reverse channel as a feedback message, whereas in the one-way service without the reverse channel, that is, in the one-way mode, the ROHC compression unit transmits the contact packet transmitted by itself. There is no way to check whether it has been successfully sent. Therefore, when the context packet is discarded or misinterpreted as a transmission failure in the unidirectional mode, the context synchronization of the ROHC compression unit and the ROHC decompression unit is corrupted when the context is updated to a completely different form.

Next, the packet c is compressed and transmitted to the terminal 20 based on the compression application context stored in the first context storage unit 12a of FIG. 1. However, if it is assumed that the decompression application context stored in the second context storage unit 22a, that is, the context transmitted from the packet b, is different from the compression application context of the packet c, the header of the packet c does not decompress normally. Packet c is discarded. In addition, as described above, since the context update by the IR process is to transmit six data packets, packet d, packet e, packet f, packet g, packet h, and packet i are discarded like packet c.

As described above, when the IR process is applied to the unidirectional service, even if the context is inconsistent with each other as described above, the inconsistency has to be solved by periodically transmitting / updating the context. In other words, when the IR process is applied, the error rate is very high compared to the case of transmitting a packet without header compression.

In summary, the error rate will be small if the packet is transmitted without header compression. However, there is a problem in that the size of the header is too much to cover and the bandwidth is wasted. In the case of applying the IR process, if the IR process cycle is shortened, the discarded data packet can be reduced, but the header compression rate is lowered. And frequent transmission of context packets is disadvantageous in terms of bandwidth. If the IR process period is lengthened, there is a problem that an error rate increases due to an increase in discarded data packets.

The technical problem to be solved by the present invention is to give priority to mutual inconsistency information when mutual inconsistency of compression application / decompression application context occurs in unidirectional service that transmits packet from AP to terminal using ROHC method. It is an object of the present invention to provide a network system and a control method thereof that can quickly restore mutual inconsistency by transmitting to an AP.

In order to solve the above technical problem, the network according to the present invention is a network system for compressing / decompressing a header of a packet to be transmitted based on a context (context) that is compression / decompression reference information. A transmitting node for compressing a header of the packet to be transmitted based on the test host; And a MAC corresponding to reception of a packet transmitted after the transmission target packet when the compression applying context and the predetermined decompression application context are inconsistent with each other when decompressing the header of the transmission target packet compressed. And a receiving node for adding a feedback message, which is context mismatch related information, to the layer ACK signal and transmitting the feedback message to the transmitting node.

The receiving node may include: a context storage unit storing the decompression application context; Decompressing the header of the transmission target packet based on the decompression application context, and generating the feedback message when it is determined that the decompression application context and the compression application context are inconsistent with each other during the decompression process; Decompression unit; And a MAC layer control unit for receiving the transmission target packet from the transmitting node and transmitting it to the decompression unit, generating a predetermined MAC layer ACK signal corresponding to the reception of the packet transmitted from the transmitting node, and transmitting the predetermined MAC layer ACK signal to the transmitting node. And the MAC layer controller adds the feedback message to generate the predetermined MAC layer ACK signal when the generation of the feedback message before the transmission of the predetermined MAC layer ACK signal is detected.

The receiving node, when it is determined that the compression applied context and the decompression applied context are inconsistent with each other, sets a contact mismatch state to an indicator provided to indicate whether or not the contact mismatch occurs and temporarily stores the feedback message. The apparatus further includes a feedback controller, wherein the MAC layer controller checks the indicator before transmitting the predetermined MAC layer ACK signal, and reads the temporarily stored feedback message when the indicator is set to a context mismatch state. The feedback message is added to generate the predetermined MAC layer ACK signal.

The compression / decompression process of the header is preferably performed based on a RObustness Header Compression (ROHC) method.

The frame of the MAC layer ACK signal includes a duration field and a feedback field generated based on a bit value of the duration field, and the feedback message is set in the feedback field.

The packet transmitted after the transmission target packet is preferably the next packet of the transmission target packet.

In addition, in order to solve the above technical problem, the control method according to the present invention, in order to provide a service for transmitting a transmission target packet from a transmitting node to a receiving node, the context of the header of the transmission target packet compression / decompression reference information A control method of a network system for compressing / decompressing based on a method, comprising: (a) compressing a header of a packet to be transmitted based on a compression application context preset to the transmitting node; (b) transmitting the header-compressed packet to the receiving node; And (c) if the decompression application context set in the receiving node and the compression application context are inconsistent with each other when decompressing the transmitted header of the transmission target packet, transmission after the transmission target packet. And adding a feedback message, which is context mismatch related information, to a MAC layer ACK signal corresponding to the reception of a packet, and transmitting the feedback message from the receiving node to the transmitting node.

Furthermore, in order to solve the above technical problem, in order to provide a service for transmitting a transmission target packet from a transmission node to a reception node, the control method includes a context of compressing / decompressing headers of the transmission target packet as reference information. A control method of a network system for compressing / decompressing based on the received data, the control method comprising: receiving the header-compressed packet to be transmitted based on a compression application context preset to the transmitting node; Determining whether the decompression application context information preset to the receiving node and the compression application context information coincide with each other; Piggybacking a feedback message, which is context mismatch related information, to a MAC layer ACK signal corresponding to reception of a packet transmitted after the transmission target packet when it is determined that the mutual mismatch is determined; And transmitting the MAC layer ACK signal to which the feedback message is added, to the transmitting node.

Hereinafter, a network system and a control method thereof according to the present invention will be described in detail with reference to an embodiment.

3 is a block diagram showing the internal structure of a terminal and an AP according to the present invention.

The AP 100 includes a first ROHC module 120 and a first MAC layer controller 140. The first ROHC module 120 includes a first context storage unit 122, a ROHC compression unit 124, and a first feedback adjustment unit 126.

The ROHC compression unit 124 compresses the header of the data packet to be transmitted to the terminal 200 based on the compression application context stored in the first context storage unit 122. The header compressed data packet is transmitted to the terminal 200 via the first MAC layer controller 140. At this time, the data packet is transmitted through the forward channel.

In addition, the MAC layer ACK signal to which the message including the context mismatch state information and the decompression application context information (hereinafter referred to as a feedback message) from the terminal 200 is piggybacked, is the first feedback in the AP 100. When sent to the adjuster 126, the first feedback adjuster 126 generates a new context based on the feedback message and the compression application context. The generated context is transmitted to the terminal 200 through the forward channel through the ROHC compression unit 124 and the first MAC layer control unit 140 and updated and stored in the second context storage unit 222 which will be described below.

In addition, the terminal 200 includes a second ROHC module 220 and a second MAC layer controller 240. The second ROHC module 220 includes a second context storage unit 222, a ROHC decompression unit 224, and a second feedback adjustment unit 226. The second feedback adjustment unit 226 also has a flag 226a. The flag 226a is set to false if there is no delivery of the context mismatch state information from the ROHC decompression unit 224 (flag = false), and the delivery of the context mismatch state information from the ROHC decompression unit 224 is prevented. If present, set to true (flag = true). When the packet transmitted through the forward channel is transmitted, the second MAC layer controller 240 transmits a MAC layer ACK signal to the AP 100 in response to the transmitted packet. The AP 100 may check whether the packet is transmitted through this.

The data packet transmitted through the forward channel is input to the ROHC decompressor 224 through the second MAC layer controller 240 and decompressed. At this time, it is decompressed based on the decompression application context stored in the second context storage unit 222.

The ROHC decompression unit 224 according to the present invention determines whether the compression application context and the decompression application coincide with each other when decompression. If they match, the transmitted data packet is decompressed normally, and the data of the data packet is processed normally. However, if they do not coincide with each other, the ROHC decompression unit 224 sets and changes the flag 226a of the second feedback adjustment unit 226 from false to true and transmits a feedback message to the second feedback adjustment unit 226 and sends the second message. The feedback adjuster 226 temporarily stores this.

The second MAC layer controller 240 according to the present invention checks the flag 226a of the second feedback controller 226 before transmitting the MAC layer ACK signal for each packet transmitted to the terminal 200 to the AP 100. do. As a result of the check, when the flag 226a is set to false, the second MAC layer controller 240 generates a normal MAC layer ACK signal and transmits it to the AP 100. However, as a result of checking, when the flag 226a is set to true, the second MAC layer controller 240 reads a feedback message to the second feedback controller 226. The second MAC layer controller 240 generates a MAC layer ACK signal based on the read feedback message. The frame of the MAC layer ACK signal to which the feedback message is added will be described in detail below. The MAC layer ACK signal to which the feedback message is added is transmitted to the AP 100. In this specification, such transmission of the MAC layer ACK signal is referred to as transmission of a feedback message through a reverse channel as in a bidirectional service. This is referred to as a virtual reverse channel.

4 illustrates a frame structure of a MAC layer ACK signal for adding a feedback message according to the present invention.

The frame structure of the MAC layer ACK signal according to the present invention includes a frame control field of 2 bytes, a duration field of 2 bytes, an address field of 6 bytes, and a frame inspection order of 4 bytes (FCS). It includes a Frame Check Sequence field and a feedback field.

The basic frame of a typical MAC layer ACK signal has a size of 14 bytes consisting of a frame control field of 2 bytes, a duration field of 2 bytes, an address field of 6 bytes, and an FCS field of 4 bytes. However, the size of the frame of the MAC layer ACK signal may be increased by adjusting the 15th bit among the 16 bits of the duration field. That is, when the fifteenth bit is '0', the value of the 0th through 14th bits represents the remaining bytes added to the basic frame. By using this, a feedback message may be added to a conventional MAC layer ACK signal. For example, when the value of the 0 th to 14 th bits indicates 20 bytes, a feedback field for adding a feedback message in addition to 6 bytes for an address and 4 bytes for an FSC is allocated 10 bytes.

5 is a timing diagram illustrating a packet transmission from an AP to a terminal in a network system according to the present invention. Hereinafter, a description will be given with reference to FIG. 3 simultaneously.

FIG. 5 does not apply the IR process applied to FIG. 2. That is, a context packet is initially transmitted without performing an IR process periodically, and a predetermined context is updated and stored in the second context storage 222, and then only the data packet is continuously transmitted. When a context mismatch is found during transmission, a method of recovering an error by transmitting a feedback message to the MAC layer ACK signal is applied.

Assume that packet a is a initially transmitted context packet. The context transmitted through the context packet is updated and stored in the second context storage unit 222.

The packet b, which is a data packet, is transmitted from the AP 100 to the terminal 200, and the ROHC decompression unit 224 applies a compression application context and a second context applied to header compression to decompress the header of the packet b. It is determined whether the decompression application contexts stored in the storage unit 222 coincide with each other. Packet b is discarded when it is assumed that the compression applying context and the decompression applying context are inconsistent with each other.

The next packet c transmitted is also discarded for the same reason as the packet b.

However, according to the present invention, as described with reference to FIG. 3, a feedback message is added when the MAC layer ACK signal of the packet c is transmitted due to the context mismatch state of the packet b. However, a feedback message may be added to MAC layer ACK signals such as packet d and packet e. The MAC layer ACK signal to which the feedback message is added is transmitted to the AP 100, and the AP 100 transmits a packet c ′, that is, a context packet including a new context, to the terminal 200 based on the feedback message. . The transmitted new context is updated and stored in the second context storage 222, whereby the header is subsequently decompressed based on the new context. Accordingly, packets d, packet e, packet f, packet g, packet h, and packet i transmitted thereafter are normally processed. In this figure, the MAC layer ACK signal to which the feedback message is added is illustrated by a dashed line. As fewer packets are discarded compared to FIG. 2, efficient use of radio resources is ensured.

6 is a flowchart illustrating a control method for preferentially repairing mutual inconsistency of a context of a network system according to the present invention.

First, in order to transmit the data packet, the ROHC compression unit 124 in the AP 100 compresses the header by the ROHC method (S300), and the header compressed data packet is transmitted to the terminal 200 (S310). Then, the terminal 200 starts decompressing the header by the ROHC decompressing unit 224 in the header compressed data packet (S320). However, header decompression is possible only when the compression applied context and the decompression applied context coincide with each other (S330). In this case, the header is decompressed normally when the data packet is transmitted. S400). However, if there is a mismatch, the ROHC decompression unit 224 changes the flag 226a of the second feedback adjustment unit 226 from false to true, generates a feedback message, and then sends it to the second feedback adjustment unit 226. Temporarily save (S340).

On the other hand, the second MAC layer controller 240 according to the present invention adds a feedback message when generating the MAC layer ACK signal when the compression applied context and the decompression applied context do not coincide with each other (S350). In this case, the second MAC layer controller 240 checks the flag 226a of the second feedback controller 226 before transmitting the MAC layer ACK signal corresponding to the transmitted packet (S352). As a result of the check, if the flag is set to false, the second MAC layer controller 240 generates a normal MAC layer ACK signal and transmits it to the AP 100. If the flag 226a is set to true, the second MAC layer controller 240 240 reads the feedback message temporarily stored in the second feedback adjustment unit 226 (S354) and adds the read feedback message when generating the MAC layer ACK signal (S356).

The second MAC layer controller 240 transmits a feedback message added to the MAC layer ACK signal to the AP 100 (S360). The AP 100 generates a new context based on this and transmits a context packet including the same to the terminal 200 (S360 and S370). The transmitted new context is updated and stored in the second context storage unit 222, and the header of the data packet transmitted thereafter is decompressed and processed normally (S390 and S400).

As described above, according to the present invention, in the unidirectional service applying the ROHC method, virtual reverse channelization of the existing MAC layer ACK signal is transmitted to the AP to transmit contact mismatch state information to the terminal, thereby limiting radio resources. There is an advantage that can be used efficiently.

In addition, it is possible to promptly solve a problem caused by a context mismatch in a unidirectional service using the conventional ROHC method. In other words, by adding a feedback message from the terminal to the MAC layer ACK signal in the unidirectional service, the context mismatch status information may be transmitted to the AP. This can quickly resolve the context mismatch between the terminal and the AP.

In addition, the present invention has the advantage of maintaining a lower error rate while maintaining the same header compression rate compared to the case of applying the IR process.

In the above description of the preferred embodiment of the present invention, the present invention is not limited to the above-described specific embodiment, it is common in the art to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

1 is a block diagram showing the internal structure of a conventional terminal and an AP,

2 is a timing diagram illustrating a packet transmission from an AP to a terminal in a network system providing a conventional unidirectional service.

3 is a block diagram showing the internal structure of a terminal and an AP according to the present invention;

4 illustrates a frame structure of a MAC layer ACK signal for adding a feedback message according to the present invention;

FIG. 5 is a timing diagram illustrating how packets are transmitted from an AP to a terminal in a network system providing one-way service according to the present invention.

6 is a flowchart illustrating a control method for preferentially repairing mutual inconsistency of a context of a network system according to the present invention.

<Description of Major Symbols in Drawing>

100: access pointer (AP) 120: first ROHC module

122: first context storage unit 124: ROHC compression unit

126: first feedback control unit 140: first MAC layer control unit

200: terminal 220: second ROHC module

222: second context storage unit 224: ROHC decompression unit

226: second feedback adjustment unit 226a: flag

240: second MAC layer control unit

Claims (12)

A network system for compressing / decompressing a header of a packet to be transmitted based on a context that is compression / decompression reference information. A transmitting node for compressing a header of the transmission target packet based on a predetermined compression application context; And MAC layer corresponding to the reception of the packet transmitted after the transmission target packet when the compression application context and the predetermined decompression application context are inconsistent with each other when decompressing the header of the transmission target packet compressed And a receiving node that adds a feedback message as context mismatch related information to an ACK signal and transmits the feedback message to the transmitting node. The method of claim 1, The receiving node, A context storage unit for storing the decompression application context; Decompressing the header of the transmission target packet based on the decompression application context, and generating the feedback message when it is determined that the decompression application context and the compression application context are inconsistent with each other during the decompression process; Decompression unit; And A MAC layer control unit which receives the transmission target packet from the transmission node and transmits it to the decompression unit, generates a predetermined MAC layer ACK signal corresponding to the reception of the packet transmitted from the transmission node, and transmits the predetermined MAC layer ACK signal to the transmission node; Including, The MAC layer control unit generates the predetermined MAC layer ACK signal by adding the feedback message when generation of the feedback message is detected before transmission of the predetermined MAC layer ACK signal. The method of claim 2, The receiving node, when it is determined that the compression applied context and the decompression applied context are inconsistent with each other, sets a contact mismatch state to an indicator provided to indicate whether or not the contact mismatch occurs and temporarily stores the feedback message. It further comprises a feedback adjustment unit; The MAC layer controller checks the indicator before transmission of the predetermined MAC layer ACK signal, reads the temporarily stored feedback message when the indicator is set to a context mismatch state, and adds the feedback message to the predetermined message. A network system, characterized in that for generating a MAC layer ACK signal. The method of claim 1, The compression / decompression process of the header, the network system, characterized in that performed based on the ROHC (RObustness Header Compression) method. The method of claim 1, The frame of the MAC layer ACK signal includes a duration field and a feedback field generated based on a bit value of the duration field.  The feedback message is set in the feedback field. The method of claim 1, And a packet transmitted after the transmission target packet is a packet next to the transmission target packet. In order to provide a service for transmitting a transmission target packet from a transmitting node to a receiving node, a control method of a network system for compressing / decompressing a header of the transmission target packet based on a context of compression / decompression reference information, (a) compressing a header of the packet to be transmitted based on a compression application context preset to the transmitting node; (b) transmitting the header-compressed packet to the receiving node; And (c) if the decompression application context preset to the receiving node and the compression application context are inconsistent with each other when decompressing the transmitted header of the transmission target packet, the packet is transmitted after the transmission target packet. Piggybacking a feedback message, which is context mismatch related information, to the MAC layer ACK signal corresponding to the reception of the packet and transmitting the feedback message from the receiving node to the transmitting node. The method of claim 7, wherein Step (c) is, determining whether the decompression application context information and the compression application context information coincide with each other; (c2) if it is determined that there is a mutual mismatch, adding the feedback message to a MAC layer ACK signal corresponding to reception of a packet transmitted after the transmission target packet; And (c3) transmitting the MAC layer ACK signal to which the feedback message is added, from the receiving node to the transmitting node. The method of claim 7, wherein The compression / decompression process of the header is a control method, characterized in that performed based on the ROHC (RObustness Header Compression) method. The method of claim 7, wherein The frame of the MAC layer ACK signal includes a duration field and a feedback field generated based on a bit value of the duration field.  The feedback message is set in the feedback field. The method of claim 7, wherein And a packet transmitted after the transmission target packet is a packet next to the transmission target packet. In order to provide a service for transmitting a transmission target packet from a transmitting node to a receiving node, a control method of a network system for compressing / decompressing a header of the transmission target packet based on a context of compression / decompression reference information, Receiving the packet to be transmitted, which is header-compressed based on a compression application context preset to the transmitting node; Determining whether the decompression application context information preset to the receiving node and the compression application context information coincide with each other; Piggybacking a feedback message, which is context mismatch related information, to a MAC layer ACK signal corresponding to reception of a packet transmitted after the transmission target packet when it is determined that the mutual mismatch is determined; And And transmitting the MAC layer ACK signal added with the feedback message to the transmitting node.