KR20060015198A - Method for reporting packet process result in a mobile communication system - Google Patents

Abstract

The present invention proposes a message having a structure that can significantly reduce the size of a region (bitmap field) in which information according to a reception result is recorded while performing a role of notifying a packet reception result faithfully. To this end, the present invention allocates a message area for recording identifiers for confirming reception failure for each of the maximum allowed packets that can be processed by the block ACK. The message area is allocated so that only the reception result for the packet that fails to receive can be recorded. Correspondingly, the receiving side identifies the packet that failed to receive through the identifiers, and retransmits the packet that failed to receive according to the reception result of the packet.

ARQ, Bitmap, SN level packet, Block ACK, Sequence Number, Fragmentation Number

Description

Packet processing result notification method in mobile communication system {METHOD FOR REPORTING PACKET PROCESS RESULT IN A MOBILE COMMUNICATION SYSTEM}             

1 is a view for explaining the basic concept of a general block ACK scheme.

2 to 4 are diagrams showing examples of notifying a reception result using a bitmap.

5 illustrates a hierarchical bitmap structure proposed by the present invention.

6 and 7 illustrate examples of a message for notifying a reception result when the present invention described above is applied to 802.11n.

The present invention relates to a method for transmitting / receiving data packet processing results according to application of a retransmission scheme in a mobile communication system.

In a wireless channel, there is a possibility that an error occurs in a transmitted packet due to multipath fading and interference between users and noise. In order to solve this problem, forward error correction code (FEC) method is used to reduce the probability of an error by sending extra information, and ARQ (request to send the packet in error to the transmitter when an error occurs). Automatic Repeat Request) method and H-ARQ method combining the above two methods. In the ARQ scheme, the receiver uses an acknowledgment (ACK) / not acknowledgment (NACK) signal to inform the transmitter whether or not there is an error in the received packet. On the other hand, the transmitter confirms that the receiver has successfully received the packet by the ACK signal, and confirms that the receiver has failed to receive the packet by the NACK signal. Therefore, when the transmitter receives the MACK signal, the transmitter retransmits the packet.

The ARQ scheme includes a block ACK scheme in addition to the general ACK scheme for receiving a reception result notification for each transport packet. The block ACK method is a method in which a plurality of packets are continuously transmitted and then collectively notified of the reception results of the transmitted plurality of packets through a block ACK message.

1 is a diagram illustrating a basic concept of a general block ACK scheme. In FIG. 1, an example of applying a block ACK scheme in units of three packets is assumed.

Referring to FIG. 1, the transmitter sequentially transmits three packets (Packet # 1, Packet # 2, Packet # 3) having the same DA (ie, DA 2). A sequence number (SN) and a fragment number (FN) are assigned to each of the packets Packet # 1, Packet # 2, and Packet # 3. The SN means an order in which packets are delivered from an upper layer. Meanwhile, even a packet having the same SN may be divided into a plurality of packets and transmitted when necessary. The FN refers to a transmission order of packets divided from packets having the same SN. Therefore, the receiver checks whether or not the packet is continuously received by comparing the SN and FN of the newly received packet with the SN and FN of previously received packets. In the following description, a packet at the SN level is called an SN level packet, and a packet divided from the SN level packet is called a fragmentation packet. In the case of naming the packet rather than the SN level packet or the fragment packet, it should be interpreted as collectively referring to the aforementioned two types of packets. The first and second packets Packet # 1 and Packet # 2 of the three packets are fragment packets having the same SN (ie, SN 1) and different FNs (ie, Frag 1, Frag 2). The third packet (Packet # 3) is an SN level packet having a different SN (that is, SN 2) than the first and second packets (Packet # 1, Packet # 2).

In FIG. 1, it is assumed that the receiver successfully receives the first and third packets Packet # 1 and Packet # 3 and fails to receive the second packet (Packet # 2).

The receiver constructs a block ACK message based on the reception result and transmits the block ACK message to the transmitter. The block ACK message includes a header in which a destination address DA1 corresponding to the transmitter address is recorded, and a payload in which reception results for each of the packets are recorded. According to the reception result assumed above, ACK information is recorded as a reception result corresponding to the first and third packets Packet # 1 and Packet # 3, and a reception result corresponding to the second packet # 2. NACK information is recorded. At this time, when the ACK information or the NACK information is recorded, the SN and the FN of the corresponding packet are recorded together.

By receiving the block ACK message, the transmitter confirms that the first and third packets Packet # 1 and Packet # 3 have been normally received but failed to receive the second packet (Packet # 2). Thereafter, although not shown in FIG. 1, the transmitter retransmits the second packet (Packet # 2).

As described above, a method of recording information on a reception result for all packets received in one block ACK message may be variously implemented. However, the bitmap method is commonly used to use the smallest length of messages.

2 to 4 illustrate examples of notifying a reception result using a bitmap.

Referring to FIG. 2, a general example of a block ACK message includes a block ACK starting sequence filed and a bitmap field of N ACK report fields. N is a value corresponding to the maximum SN, and means the number of sequences capable of maximum ACK. That is, N may be defined as the maximum allowable number of SN level packets that can be processed by one block ACK.

The SN of the first SN level packet handled by the bitmap in the message is recorded in the block ACK start sequence field. In the bitmap field, reception result information of N consecutive packets is recorded starting from a packet having an SN recorded in the block ACK start sequence field.

On the other hand, each of the ACK report fields constituting the bitmap field are areas (hereinafter referred to as a reception result information field ') b0 and b1 corresponding to the number of fragment packets Mⅹ8 that can be divided up from one SN level packet. , b2,, b (n), and b (8ⅹM-1), because the reception result information is notified for each fragment packet, so that the reception result information is represented by one bit, The total reception result information fields for the level packet require M octets, and the total length of the bitmap field is MⅹN octets.

For example, when SN 1 is recorded in the block ACK start sequence field, the reception result information for the fragment packet whose SN is 1 and the FN is n-1 is recorded in the reception result information field b (n) indicated by reference numeral 210. Will be. If the fragment packet is successfully received, 1 is recorded in the reception result information field b (n). Otherwise, if it fails to receive the fragment packet, 0 is recorded in the reception result information field b (n). This assumes that 1 is an identification bit indicating reception success and 0 is an identification bit indicating reception failure. As another example, when 5 is written in the block ACK start sequence field, when the fragment packet having SN 6 and FN 3 is successfully received, the third bit of the second octet is set to 1.

3 illustrates an example of applying the above-described general example to 802.16, and FIG. 4 illustrates an example of applying the above-described general example to 802.11e.

The block ACK message shown in FIG. 3 includes a connection ID field, an ACK control field, and a plurality of ACK MAP fields. Meanwhile, the ACK control field includes an area (FSN) in which a start sequence number is recorded and an area in which the number of sequences (Number of ACK MAP (m)) is recorded. The ACK MAP fields exist as many as the number of sequences. Each of the ACK MAP fields has the same structure as the ACK report field described with reference to FIG. 2. In FIG. 3, each of the connection ID field, the ACK control field, and the plurality of ACK MAP fields consists of two octets, so that the block ACK message has a total length of (m + 2) ⅹ2. . Typically, in 802.16, m is a variable value and the maximum number of fragment packets is 16.

The block ACK message shown in FIG. 4 includes a BA Starting Sequence Control field and a BA Bitmap field. In the BA start sequence control field, information indicating a start sequence recorded in the BA bitmap field is recorded. The BA bitmap field consists of a plurality of ACK MAP fields. Each of the ACK MAP fields has the same structure as the ACK report field described with reference to FIG. 2. For example, in the case of 802.11, ACK processing for up to 64 SN level packets can be performed simultaneously, and one SN level packet can be divided into up to 16 operation packets. Therefore, when each of the ACK MAP fields is composed of two octets, in FIG. 4, the BA bitmap field must maintain a size of 128 octets.

As described above, if the reception result is notified using the conventional bitmap, unnecessary resource waste occurs. That is, in the related art, a bitmap is constructed in consideration of the fact that each of the SN level packets is divided into maximum fragment packets. Therefore, when the reception result information is transmitted in response to an SN level packet not divided into an operation packet or divided into a maximum number of fragment packets, reception result information fields not used in the bitmap field are generated. These reception result information fields may be referred to as unnecessary resources.

Accordingly, an object of the present invention for solving the above problems is to provide a method for minimizing the length of a message to transmit the reception result information.

Another object of the present invention is to provide a method of allocating an identification bit area to a message for transmitting received information to quickly identify a packet that fails to receive.

Another object of the present invention is to provide a method of transmitting reception result information only for a packet that fails to receive.

It is still another object of the present invention to provide a method for checking a packet that fails to receive through identification bits corresponding to each packet and receiving only reception result information regarding the packet that failed to receive.

It is still another object of the present invention to provide a method for determining the size of a bitmap field in which a reception result information is recorded in a message transmitting reception result information by the number of packets that fail to receive.                         

It is another object of the present invention to provide a method for extending a message area for transmitting reception result information when the number of unsuccessful packets exceeds a predetermined threshold.

In a first aspect for achieving the above object, the present invention provides a method for constructing a message for notifying the transmitter of a reception result for each star, the packet in the first bitmap field assigned to the message. Recording an identifier indicating whether the reception is successful for each, and generating an area (ACK report field) in which a reception result is to be recorded in response to the packet which failed to receive among the packets in the second bitmap field of the message; And recording a reception result of the packet that failed to be received in the generated area.

In a second aspect for achieving the object as described above, the present invention is notified through a predetermined message in the transmitter of the mobile communication system for continuously transmitting packets having a sequence number and a fragment number assigned for mutual discrimination A method for retransmitting a packet that has failed to be received due to a reception result for each packet corresponding to the maximum number of sequences that can be answered, the reception success of each packet having a different sequence number recorded in the first bitmap field of the message Checking whether there is a packet that failed to receive through an identifier indicating whether or not, and if the packet that failed to receive exists, an ACK report allocated corresponding to the packet that failed to receive in the second bitmap field of the message. Checking the fragment number of the packet which failed to be received according to the reception result of the field; And a packet having failed sequence number and fragment number, characterized in that it comprises the step of re-transmitting the received group.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. DETAILED DESCRIPTION In the following detailed description, one exemplary embodiment of the present invention will be presented to accomplish the above technical problem. And other embodiments that can be presented with the present invention are replaced by the description in the configuration of the present invention.

The present invention proposes a message having a structure that can significantly reduce the size of a region (bitmap field) in which information according to a constant reception result is recorded while faithfully performing a role of notifying a packet reception result. This can be achieved by considering two aspects. The first consideration is that the packet error rate (PER) is designed at the level of typical wireless data communication systems. The second consideration is that packet loss is concentrated at a specific moment rather than evenly distributed.

Referring to the above two considerations, it can be seen that the number of packets in which an error occurs is extremely small, and that an error occurs only at a specific moment. Therefore, it can be expected that for most packets, even if the reception succeeds, the reception failure will occur only in a portion of consecutive packets among the maximum allowable packets that can be processed by the block ACK. From this point of view, when the ARQ scheme is implemented to notify the reception result of only a packet that fails to receive, the amount of information according to the reception result notification can be greatly reduced. Reducing the amount of information according to the reception result notification implies that the size of the bitmap is reduced.

The detailed description to be described later will propose a block ACK message to notify the reception result information only for each of the fragment packets divided from the SN level packet that failed to receive. In addition, a field (hereinafter, referred to as an SN level bitmap field) for transmitting identifiers for confirming reception failure for each of the maximum allowed SN level packets that can be processed by the block ACK is newly defined.

To this end, the transmitting side (packet receiving side) checks whether a packet fails to receive. If there is a packet that fails to receive, an identifier indicating a reception failure is set in a region corresponding to the packet in the SN level bitmap field. Otherwise, an identifier indicating successful reception is set in a region corresponding to the packet in the SN level bitmap field. The packet that fails or succeeds in receiving is an SN level packet when it is not divided into fragment packets, and when it is divided into fragment packets, it corresponds to fragment packets.

An ACK report field is generated in response to the packet that fails to receive, and an identifier indicating a reception failure is set in a reception result information field corresponding to the packet among reception result information fields constituting the ACK report field. An identifier indicating success of reception is set for the remaining reception result fields among the reception result information fields constituting the ACK report field. Of course, in case of failing to receive a plurality of fragment packets, an identifier indicating a reception failure may be set in reception result fields corresponding to each of the plurality of fragment packets.

As described above, when the block ACK message is configured by the reception result for the maximum allowed SN level packets that can be processed as the block ACK, the block ACK message is transmitted to the receiver.

The receiving side (the transmitting side of the packet) may check whether the reception of the SN level packets failed by checking the identifiers recorded in the SN level bitmap field. When the receiving side confirms that there is an SN level packet that failed to receive, the receiving side checks an ACK report field corresponding to the SN level packet. In this case, the ACK report field includes reception result information fields corresponding to each of the maximum fragment packets that can be divided from one SN level packet. Therefore, the receiving side can check the received result information fields of the ACK report field corresponding to the SN level packet which failed to receive, so that it is possible to know which fragment packet failed to receive.

5 illustrates a hierarchical bitmap structure proposed in the present invention.

Referring to FIG. 5, a block ACK message having a hierarchical bitmap structure proposed by the present invention includes a block ACK starting sequence filed and a SN level bitmap filed. It consists of a bitmap field consisting of M ⅹ m ACK report fields. M corresponds to the number of zeros set in the SN level bitmap field. That is, m is the number of packets which failed to receive among the maximum allowable SN level packets that can be processed by the block ACK. This is because an ACK report field is generated in response to a packet that fails to receive.                     

The SN of the first SN level packet handled by the bitmap in the message is recorded in the block ACK start sequence field. In this case, the first SN level packet may be defined as a first SN level packet to report a reception result through the block ACK message. Note that this is not the first SN level packet that fails to receive.

Meanwhile, in the present invention, the bitmap field is divided into two bitmap fields. That is, the bitmap field is divided into an SN-level bitmap filed and an Erroneous SN packet bitmap filed.

When the number of maximum allowable SN level packets that can be processed by the block ACK is 8 nN, the SN level bitmap field has a length of N octets corresponding to 8 n N bits. Each of the 8ⅹN bits corresponding to the N octets corresponds to the SN quick reference bits. The SN quick reference bits are used to indicate reception success or failure of each of the maximum allowable SN level packets. That is, 1 is used as the SN quick reference bit indicating the reception success, and 0 is used as the SN quick reference bit indicating the reception failure.

For example, when successfully receiving all fragment packets divided from SN level packets whose SN is n + 1, the n + 1th SN quick reference corresponding to the SN level packet among the SN quick reference bits. Bit (SN quick reference bit) b (n) is set to one. However, when it fails to receive any fragment packet among the fragment packets divided from the SN level packet, the n + 1 th SN quick corresponding to the SN level packet among the SN quick reference bits Set the SN quick reference bit (b (n)) to zero. The above example applies equally to SN level packets that are not divided into fragment packets.

The failed SN packet bitmap field includes an ACK report field corresponding to an SN level packet set to 0 as the SN quick reference bit. That is, the number m of ACK report fields constituting the Erroneous SN Packet bitmap filed corresponds to the number of SN quick reference bits set to zero. Thus, the Erroneous SN Packet bitmap filed has a length of M_m octets. Here, M octets are the total length of the ACK report field and have a fixed value. In other words, it can be seen that the total length (M_m octets) of the Erroneous SN Packet bitmap filed is determined by the number m of failed SN level packets. For example, as the number of SN-level packets failed to be received increases, the total length (M_m octets) of the Erroneous SN Packet bitmap filed becomes longer. Otherwise, the smaller the number of failed SN level packets, the shorter the total length (M_m octets) of the Erroneous SN Packet bitmap filed. In extreme cases, if there is no SN level packet that fails to receive among the maximum allowable SN level packets, the Erroneous SN Packet bitmap field is not necessary. Meanwhile, the mapping relationship between the SN quick reference bit set to 0 and the ACK report field may be variously established. As an easy example, the ACK report fields are sequentially mapped in correspondence with the order of the quick quick reference bits set to zero. For example, assuming that the value of the block ACK start sequence field is 5 and the value of the SN level bitmap field is 11101011, there are two ACK report fields in the failed SN packet bitmap field. The first ACK report field of the two ACK report fields is a bitmap of an SN level packet with an SN of 8, and the second ACK report field is a bitmap of an SN level packet with an SN of 10. It may also be implemented by a method of assigning an identifier to the ACK report field.

Each of the ACK report fields constituting the Erroneous SN Packet bitmap filed includes reception result information fields b0 corresponding to the number of fragment packets Mⅹ8 that can be divided up from one SN level packet. , b1, b2,, b (n), and b (8-1M-1), because the reception result information is notified for each fragment packet, so that the reception result information is represented by 1 bit. The total reception result information fields for the SN level packet of the M octet are required, so the total length of the Erroneous SN Packet bitmap filed is Mⅹm octets.

For example, assuming that SN and FN each fail to receive a fragment packet of n + 1, b, which is the n + 1th SN quick reference bit among the SN quick reference bits constituting the SN level bitmap, is assumed. (n) is set to zero. An ACK report field (hereinafter assumed to be the m th ACK report field) to be mapped to the b (n) is allocated to the failed SN packet bitmap field. Thereafter, a reception result information bit indicating reception failure is set in the n + 1th reception result information field b (n) among the reception result information fields in the m th ACK report field. For example, 0 may be used as a reception result information bit value indicating the reception failure. In this case, a value indicating success of reception is set in the remaining reception result information bits except the n + 1 th reception result information field b (n) among the reception result information fields in the m th ACK report field.

6 and 7 illustrate examples of a message for notifying a reception result when the present invention described above is applied to 802.11n. The example shown in FIG. 6 and the example shown in FIG. 7 are distinguished by the number of packets failed to be received among packets (MSDUs) transmitted from a transmitter. That is, if the number of MSDUs that have failed to receive is less than the predetermined threshold (12 as an example), the message structure shown in FIG. 6 is used. However, if the number of MSDUs that failed to receive is equal to or exceed a predetermined threshold (12 as an example), the message structure shown in FIG. 7 is used.

Referring to FIG. 6, the block ACK message includes a BA control field, a BA starting sequence control field, and a BA failed packet bitmap field.

The BA control field has a length of 2 octets, and includes a TMS field and a bit map field (BA MSDUs' bitmap filed) consisting of quick reference bits for indicating whether each of the SN level packets has been successfully received. The bitmap field (BA MSDUs' bitmap filed) is an area not used in the existing 802.11. It is used again for the present invention. As shown in FIG. 6, the case of having less than 12 MSDUs is used. Thus, the BA MSDUs' Bitmap field is composed of 12 bits of quick reference bits.

Meanwhile, a random bit is allocated in the BA control field and used as a message identifier. The first one bit of the BA control field may be allocated for the message identifier. The message identifier is used to indicate whether to use the message type shown in FIG. 6 or the message type shown in FIG. 7 as a block ACK message. In FIG. 6, 1 is used as the message identifier.

In the BA start sequence control field, the SN of the first SN level packet handled by the bitmap in the corresponding message is recorded. In this case, the first SN level packet may be defined as a first SN level packet to report a reception result through the block ACK message. Note that this is not the first SN level packet that fails to receive.

The BA Erroneous MSDUs' Bitmap filed consists of a plurality of ACK MAP fields not exceeding eleven. The structure of the BA Erroneous MSDUs' Bitmap filed has the same structure and function as the Erroneous SN Packet bitmap filed described above with reference to FIG. 5. Therefore, a detailed description of the BA Erroneous MSDUs' Bitmap filed will be omitted.                     

Referring to FIG. 6, a block ACK message includes a BA control file, a BA starting sequence control field, a BA starting sequence control field, a BA MSDUs' bitmap field, and a BA failed packet bitmap field. filed).

Any one bit is allocated in the BA control field and used as a message identifier. The first one bit of the BA control field may be allocated for the message identifier. 7 corresponds to a case where the number of failed MSDUs reaches an arbitrary threshold (12 as an example), and thus, 0 is used as the message identifier. The other bit is allocated in the BA control field and used as a success identifier for indicating success in receiving all packets (assuming 64 MSDUs in FIG. 7) (indicated by A in the drawing). box). If the reception of all SN level packets to report the reception result via the message is successful, the success identifier is set to a value of one. However, if any SN level packet of all SN level packets to report a reception result through a message fails to receive, the success identifier will be set to a value of zero. If the success identifier is set to a value of 1, the BA MSDUs 'Bitmap field and the BA Erroneous MSDUs' Bitmap filed for recording the reception result do not need to be present in the message.

Since the BA MSDUs 'Bitmap field performs the same function as the BA MSDUs' Bitmap field present in the BA control field in FIG. 6, detailed description thereof will be omitted. However, the BA MSDUs' Bitmap field in FIG. 7 has a size of 64 bits (8 octets) by indicating whether reception of 64 packets is successful.                     

The BA Erroneous MSDUs' Bitmap filed consists of ACK MAP fields corresponding to the number of unsuccessful packets. The structure of the BA Erroneous MSDUs' Bitmap filed has the same structure and function as the Erroneous SN Packet bitmap filed described above with reference to FIG. 5. Therefore, a detailed description of the BA Erroneous MSDUs' Bitmap filed will be omitted.

In the present invention, it is possible to efficiently use transmission resources by proposing a hierarchical bitmap structure to notify the reception result of the transmitted packets. In addition, considering the actual environment, it is expected that not only can the gain of transmission resources be improved, but also the effect is great in terms of performance.

Claims (5)

A method of configuring a message for notifying a transmitter of a reception result for each packet corresponding to the maximum responsive sequence number transmitted from a transmitter in a receiver of a mobile communication system, Recording an identifier indicating whether the reception is successful for each of the packets in a first bitmap field allocated to the message; An area (ACK report field) is generated in a second bitmap field of the message corresponding to a packet that failed to receive, and an reception result of the packet that failed to receive is recorded in the generated area. The method comprising the step of. The method as claimed in claim 1, wherein the generated area (ACK report field) is divided by identification bits for indicating a reception result of each fragment packet that can be divided into a maximum from one packet. 3. The method of claim 2, wherein if the packet that fails to receive is a fragment packet divided from one packet, an identification bit corresponding to the fragment packet among the identification bits divided in the generated area (ACK report field) is received. The method as set to a value indicating failure. In the transmitter of the mobile communication system, which continuously transmits packets having a sequence number and a fragment number assigned to distinguish each other, the reception fails by the reception result for each packet corresponding to the maximum responsive sequence number notified through a predetermined message. In a method for retransmitting a packet, Checking whether there is a packet that failed to receive through an identifier indicating whether the reception of each packet having a different sequence number recorded in the first bitmap field of the message is successful; If there is a packet that fails to receive, checking the fragment number of the packet that failed to receive according to a reception result of an ACK report field allocated corresponding to the packet that failed to receive in the second bitmap field of the message; And retransmitting a packet having a sequence number and a fragment number that failed to be received to the receiver. The identification field according to claim 4, wherein the generated area (ACK report field) is divided into a maximum from one packet having a random sequence number and indicates a reception result of each fragment packet having a different fragment number. Said method comprising of bits.

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