KR100651441B1 - Method for constructing bitmap and method for re-transmitting packet using the bitmap - Google Patents

Abstract

The present invention relates to a bitmap configuration method for providing transmission result information in a packet transmission system, wherein the received packets are grouped into a predetermined number and classified, and whether there is a packet reception error for each group is determined. Each bit is assigned a representative bit indicating whether a packet reception error occurs, and each bit of each received packet of a group having a packet reception error is allocated to a single bit indicating whether a reception error occurs. In the packet retransmission method using such a bitmap, the packet receiving side constructs a bitmap and transmits it to the packet transmitting side, and the packet transmitting side confirms the representative bit and the individual bit in the bitmap transmitted from the packet receiving side. Check the packet with a reception error and retransmit the packet.

Bitmap, packet, retransmission

Description

Bitmap composition and packet retransmission method using the same {METHOD FOR CONSTRUCTING BITMAP AND METHOD FOR RE-TRANSMITTING PACKET USING THE BITMAP}             

1 is an exemplary diagram of a block ACK message for notification of a transmitted packet and a reception result in a general block ACK scheme;

2 illustrates an example of a block ACK message using a bitmap in a block ACK scheme;

3 is a flowchart of a bitmap configuration operation at a receiving side of a packet transmission system according to an embodiment of the present invention.

4 is a flowchart of a bitmap analysis operation at a transmitting side of a packet transmission system according to an embodiment of the present invention.

5 is a comparison configuration diagram of a bitmap constructed in accordance with an embodiment of the present invention and a bitmap constructed in a conventional manner.

6 is a schematic block diagram of a packet transmission system to which the present invention is applied.

The present invention relates to a packet retransmission scheme used in a mobile communication system, and more particularly, to a configuration of a bitmap that is packet retransmission information and a packet retransmission method using the same.

In a wireless channel, errors in a transmitted packet are likely to occur due to multipath fading and interference between subscriber transmission signals and noise. Therefore, in order to cope with the error of the transport packet, Forward Error Correction Code (FEC) method that reduces the probability of error by sending extra information additionally, and when an error occurs, an error occurs from the receiving side to the transmitting side. An Automatic Repeat Request (ARQ) scheme for requesting to retransmit a packet or an H-ARQ scheme in which the two schemes are combined is commonly used.

In more detail, the ARQ scheme (or H-ARQ scheme) is used. The receiver uses an acknowledgment (ACK) / not acknowledgment (NACK) signal to inform the transmitter of whether there is an error in the received packet. The ACK signal indicates that the reception of the packet has been normally performed, and the NACK signal indicates that there is an error in receiving the packet (packet reception failure). When the transmitting side receives the NACK signal, the transmitting side retransmits the packet.

In the ARQ scheme (or H-ARQ scheme), there is a so-called block ACK scheme that notifies a reception result at a time by a plurality of packets appropriately grouped in addition to the general ACK scheme that reports a reception result for each transport packet. In the block ACK scheme, a plurality of packets are continuously transmitted, and the receiving side generates information on a reception result for each of the plurality of transmitted packets in a predetermined format and transmits the information to the transmitting side.

FIG. 1 illustrates an example of transmitting a block ACK message in units of three packets, as an example of a packet transmitted in a general block ACK scheme and a reception result of a block ACK message. Referring to FIG. 1, the transmitting side sequentially transmits three packets (Packet # 1, Packet # 2, Packet # 3) having the same destination address (ie, the transmitting address DA2). Each transmitted packet is assigned a sequence number (SN) and a fragment number (FN). The sequence number indicates the order in which packets are delivered from an upper layer, and the fragment number indicates the order of packets in which data having the same sequence number is divided.

In the example of FIG. 1, the first and third packets Packet # 1 and # 3 are successfully received at the receiving side, and a state in which the second packet (Packet # 2) has failed to be received is illustrated. The receiving side constructs a block ACK message according to the reception result and transmits it to the transmitting side. The block ACK message may include a header in which the destination address DA1 corresponding to the sender's address is recorded, and a payload in which reception results of the respective packets are recorded, wherein the payload is in the first and third packets. ACK information is recorded as a corresponding reception result, and NACK information is recorded as a reception result corresponding to the second packet.

Subsequently, by receiving the block ACK message configured as described above, the transmitter determines that the transmission of the second packet has not been normally performed, and retransmits the second packet.

A method of recording information on a reception result of all packets received in one block ACK message as shown in FIG. 1 may be implemented in various ways. However, in order to construct a message having the smallest length, a bitmap ( bitmap) is commonly used.

2 is a diagram illustrating an example of a block ACK message using a bitmap in a block ACK scheme. The block ACK message shown in FIG. 2 is composed of a block ACK starting sequence field and a bitmap of N ACK report fields. In this case, N is a value corresponding to the maximum SN and indicates 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 starting from the packet having the SN recorded in the block ACK start sequence field is recorded.

On the other hand, each of the ACK report fields constituting the bitmap field is divided into regions [b0, b1, b2, ... b (n) by the number of fragment packets Mx8 that can be divided up from one SN level packet. ), ... b (8xM-1)]. This is because the reception result information is notified for each fragment packet. Therefore, when the constant reception result information is represented by 1 bit, M octets are required as total reception result information fields for one SN level packet, 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 occasional result information for the fragment packet whose SN is 1 and the FN is n-1 is shown in the reception result information field indicated by reference numeral 210 [b (n). Will be recorded. At this time, if the fragment packet is successfully received, 1 is recorded. If the packet fails to be received, 0 is recorded.

As described above, since the reception result notification method using the bitmap notifies the reception result using only one bit per packet, the number of bits required in constructing the reception result notification message can be considerably reduced. There is still room for improvement in the reception result notification method.

In the present invention, a bitmap configuration and packet retransmission using the same are further reduced by minimizing the waste of bits by further reducing the number of bits for the reception result notification message used in the bitmap. In providing a method.

In order to achieve the above object, an aspect of the present invention provides a method for constructing a bitmap for providing transmission result information in a packet transmission system, comprising: classifying and classifying received packets into a predetermined number; Determining whether there is a packet reception error; allocating a representative bit of 1 bit indicating whether a packet reception error is performed for each group according to the determination result; and whether or not a reception error is received for each received packet of the group having the packet reception error. And allocating individual bits of 1 bit representing each.

According to another aspect of the present invention, in a packet retransmission method using a bitmap that provides transmission result information in a packet transmission system, at the packet receiving side, grouping and classifying the received packets into a predetermined number; Determining whether there is a packet reception error for each step, allocating a representative bit of 1 bit indicating whether a packet reception error is performed for each group according to the determination result, and receiving error for each corresponding received packet of the group having the packet reception error. Allocating the individual bits of the 1-bit indicating whether the bitmap is configured to transmit the packet to the packet transmitting side, the packet transmitting side, the representative bit and the bitmap transmitted from the packet receiving side. The process of retransmitting the packet by checking the packet with a reception error by checking the individual bit It characterized in that it comprises.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific details such as specific components are shown, which are provided to help a more general understanding of the present invention, and it is understood that these specific details may be changed or changed within the scope of the present invention. It is self-evident to those of ordinary knowledge in Esau.

In the present invention, the reception result information is not indicated by allocating one bit for each received packet. For example, the reception packet is grouped by K packets and the reception result is grouped. To this end, a set of 1 bits, a so-called 'representative bit', representing a reception result for each group of K packets is set. The representative bit is set to '1', for example, if there is no error in the received packets of the group represented by the representative bit, and set to '0' if there is an error. Therefore, when the representative bit is set to '1', it indicates that there is no error in all the received packets of the corresponding group, and thus the reception result information of the received packets can be represented by only one bit of the representative bit.

In this case, when the representative bit is set to '0', one bit for each received packet of the corresponding group is additionally allocated a so-called 'individual bit' to indicate reception result information. Of course, when the representative bit is set to '1' (that is, there is no reception error in the received packets of the group), the individual bit is not added. At this time, the individual bit is to indicate the reception result information of each received packet. If there is no error in the received packet, for example, it is set to '1', and if there is an error, it is set to '0'. For example, if each of the five packets are grouped, assuming that there is a reception error of the third packet in a specific group, the representative bit of the corresponding group is set to '0' and the individual bits are set to '11011'.

By using the representative bits and the individual bits, the total number of bits of the bitmap representing the reception result information can be reduced. Hereinafter, this will be described in more detail with reference to the accompanying drawings.

3 is a flowchart of a bitmap configuration operation at a receiving side of a packet transmission system according to an embodiment of the present invention, in which an operation of grouping received packets into K packets and configuring a bitmap indicating a reception result for each group is disclosed. . Referring to FIG. 3, first, K received packets are classified in step 310. Thereafter, in step 312, it is determined whether there is a reception error in the K classified packets. If there is no reception error, the flow proceeds to step 314, and if there is a reception error, the flow proceeds to step 316.

In step 314, the representative bit is set to 1 and then proceeds to step 320. In step 316, the representative bit is set to 0 and then proceeds to step 318. In step 318, individual bits corresponding to the K packets are sequentially set. Thereafter, in step 320, the representative bit and the individual bit set as described above are added to the entire bitmap. In step 322, it is determined whether the generated bitmap is a preset condition. For example, the packet transmission operation may be completed at the transmitting side, or may be set in advance to transmit the generated bitmap whenever KxN (for example, N = 4) packets are transmitted. In the case of the bitmap transmission condition, the process proceeds to step 330 and the bitmap is transmitted to the packet transmission side. If the bitmap transmission condition is not, the process proceeds to step 310 and the process is repeated. At this time, when the packet transmission operation is completed on the transmitting side, when the total number of transmitted packets does not become a multiple of K, a dummy packet for arbitrarily adjusting the multiples of K may be configured.

As illustrated in FIG. 3, a bitmap construction operation according to the present invention may be performed. In this case, if the representative bit represents 5 individual bits (K = 5, and the K value can be adjusted according to the network environment and error rate of the transmitting and receiving side), one of the received packets corresponding to the 5 individual bits needs retransmission. The representative bit is represented by 0, and then 5 individual bits indicate which packet needs retransmission. If retransmission of all received packets corresponding to five individual bits is not necessary, the representative bit is represented by 1 and thus individual bits are not added to the bitmap.

5A illustrates an example of a bitmap generated by the bitmap construction operation as shown in FIG. 3. In the bitmap illustrated in FIG. 5A, for example, when 20 (K = 5, N = 4) packets are transmitted, a transmission error occurs in the 11th, 12th, 15th, and 20th received packets. Example generated in In more detail, since there is no error in the first group, that is, the first to fifth received packets, and the second group, that is, the fifth to tenth received packets, the representative bits are set to 1, respectively, so that the first bit of the bitmap b1 and the second bit b2 are each set to one. Since there is an error in the third group of received packets, that is, the 11th to 15th received packets, the representative bit (bit b3 of the bitmap) is set to 0, and the corresponding bit is 00110 (bits b4 to b8 of the bitmap). 11, 12, 15th received packet indicates an error). Since there is an error in the fourth group in the received packet, that is, the 16-20th received packet, the representative bit (bit b9 of the bitmap) is set to 0, and the individual bits according to this are 11110 (bits of the bitmap) as shown. b10 to b14). Therefore, the total bitmap is 11000110011110 having a total of 14 bits, as shown in FIG.

Meanwhile, an example of the configuration of a conventional bitmap is disclosed in FIG. 5B. In the bitmap illustrated in FIG. 5B, as illustrated in FIG. 5A, after 20 (K = 5, N = 4) packets are transmitted, 11, 12, 15 In this case, the transmission error occurs in the 20th received packet. In this case, each bit of the bitmap represents individual reception result information of the received packet, and the entire bitmap has a total of 20 bits 11111111110011011110 in which the 11th, 12th, 15th, and 20th bits (b11, b12, b15, b20) are 0. to be.

As can also be seen in the example of the 14-bit bitmap of the present invention shown in Fig. 5A and the example of the conventional 20-bit bitmap shown in Fig. 5B, the bit of the present invention The map can reduce the number of bits required for its construction compared with the conventional one. According to the present invention, the number of bits necessary for constructing the bitmap decreases as the representative bit represents a larger number of individual bits. When the representative bit is 1, all received packets of the group represented by the corresponding representative bit are retransmitted. Since it simply shows that there is no need, confirmation work of the reception result information can be made more quickly.

4 is a flowchart of a bitmap analysis operation at a transmitting side of a packet transmission system according to an embodiment of the present invention. In FIG. 4, a variable K is a number of packets represented by a representative bit promised at a transmitting side and a receiving side. X indicates the order of bits currently identified in the corresponding bitmap, and Y indicates the order of packets corresponding to the bits currently identified in the bitmap.

Referring to FIG. 4, when a bitmap is transmitted from a receiver, the packet transmitter determines whether the bit is 0 or 1 from the first bit in the bitmap. To this end, in step 410, each variable X, Y is initialized to 1. In operation 412, it is determined whether the X-th bit is 0 in the corresponding bitmap. If it is determined that the X-th bit is not 0, that is, 1, the process proceeds to step 414. In step 414, X is increased by 1, Y is increased by K, and then the process returns to step 412 to determine whether the X-th bit (second bit) is 0. Through operation 412 and 414, it is checked whether the representative bit information in the bitmap is 1 or 0. On the other hand, if it is determined in step 412 that the X-th bit is 0 in the current bitmap, the process proceeds to step 416. Taking the bitmap shown in FIG. 5A as an example, since the first (X = 1) bit b1 is 1 in the bitmap, the process proceeds to step 412 (X = 1, Y = 1) and step 414 again. Step (X = 2, Y = 6) is performed, and since the second (X = 2) bit b2 is 1 in the bitmap, it proceeds to step 414 again to step 412 (X = 3, Y = 11). do. In this case, since the third (X = 3) bit b3 is 0 in the bitmap, the flow proceeds to step 416.

From step 416, when the corresponding representative bit is 0, it is an operation for checking individual bits derived by K number (K = 5 in the bitmap of FIG. 5 (a)). Increase by 1 (the current X = 4 in the bitmap of FIG. 5A), and initialize the variable i to count the number of times of individual bit repetition check to zero. Thereafter, in step 418, it is determined whether the X-th bit (currently b4 in the bitmap of FIG. 5 (a)) of the bitmap is 0, and if not 0, it proceeds to step 422, and if it is 0, it proceeds to step 420. In step 420, it is determined that a transmission error has occurred in the Y-th packet (currently Y = 11 in the bitmap of FIG. 5A), and the Y-th packet is classified as a retransmission packet.

In step 422, the variables X, Y, and i are increased by 1 (X = 5, Y = 12, i = 1 in the bitmap of FIG. 5 (a)). Then, in step 424, i is less than K. To judge. If i is less than K, the process proceeds to step 418, and if i is not less than K, the process proceeds to step 426. That is, in the bitmap example of FIG. 5, since K = 5, steps 418 to 422 are repeated five times. [Y = 12, Y = 15th packet is added as a retransmission packet in the bitmap of FIG. More classified as].

In step 426, if it is determined that the current bitmap has ended, if the bitmap is not terminated, the process proceeds to step 412, and if the bitmap is terminated, proceeds to step 430 and retransmits in step 420 Resend the packet classified as a packet to the receiver.

6 is a schematic block diagram of a packet transmission system to which the present invention is applied. Referring to FIG. 6, the packet transmitter 700 may include a memory 720 for storing a packet to be transmitted and a bitmap transmitted from the receiver 600, a packet transmitter 730, a bitmap receiver 740, and A transmission control unit 710 for controlling a packet transmission operation is provided. The transmitting-side transmission control unit 700 includes a bitmap reader 712 for reading a bitmap stored in the memory 720, and a bitmap checking unit 714 for interpreting the read bitmap.

The packet receiving side 600 includes a memory 620 for storing a packet transmitted from the transmitting side 700 and a bitmap generated accordingly, a packet receiving unit 640, a bitmap transmitting unit 630, and a packet receiving operation. The transmission control unit 610 for controlling the. The receiving side transmission control unit 610 includes an error checking unit 612 for checking an error of a received packet stored in the memory 620 and a bitmap generating unit 614 for generating a bitmap according to the confirmed error state.

When the packet transmitter 700 transmits a packet through the packet transmitter 730, the packet receiver 640 of the receiver 600 receives the received packet and stores the packet in the memory 620. Thereafter, the receiving side transmission control unit 610 checks the received packet stored in the memory 620 by performing the process as shown in FIG. 3, generates a bitmap, and then sends the received signal to the receiving side through the bitmap transmission unit 630. Send a bitmap.

When the bitmap is transmitted from the packet receiving side 600, the bitmap receiving unit 740 of the transmitting side 700 receives the bitmap and stores it in the memory 720. Thereafter, the transmitter-side transmission controller 710 checks a packet requiring retransmission according to the received bitmap by performing the process illustrated in FIG. 4, and then retransmits the packet to the packet transmitter 730.

As described above, a bitmap configuration and an operation of a packet retransmission method using the same may be performed. Meanwhile, in the above description of the present invention, specific embodiments have been described. Can be implemented without departing. Therefore, the scope of the present invention should not be defined by the described embodiments, but by the claims and equivalents of the claims.

As described above, the bitmap configuration and the packet retransmission technique using the same reduce the number of bits for the reception result notification message used in the bitmap, thereby minimizing the waste of bits, and Confirmation operation can be performed more quickly.

Claims (6)

In the bitmap configuration method for providing transmission result information in a packet transmission system, Grouping and classifying packets received at the packet receiving end into a predetermined number; Determining whether there is a packet reception error for each group; Allocating a representative bit of 1 bit indicating whether a packet reception error is generated for each group according to the determination result; And allocating each of the received packets of the packet to each of the received packets of the group by individually assigning 1-bit individual bits indicating whether there is a reception error. The method of claim 1, wherein the representative bit and the individual bit indicate a reception error for each group or for each received packet as '0'. In the packet retransmission method using a bitmap for providing transmission result information in a packet transmission system, Grouping and classifying the received packets into a predetermined number on the packet receiving side; determining whether there is a packet reception error for each group; and determining whether there is a packet reception error for each group according to the determination result. Allocating a representative bit, and allocating individual bits of 1 bit indicating whether a reception error exists for each received packet of the group for each group having the packet reception error. Transmitting the packet to the packet transmission side; And retransmitting the corresponding packet by identifying a packet having a reception error by checking the representative bit and the individual bit in the bitmap transmitted from the packet receiving side. 4. The method of claim 3, wherein the representative bit and the individual bit indicate a reception error for each group or for each received packet as '0'. The method of claim 1, wherein each of the individual bits is allocated. And if the representative bit indicates a packet reception error, separately assigning one bit of an individual bit indicating whether a reception error exists for each corresponding received packet of the group in addition to the representative bit. 4. The method of claim 3, wherein assigning each individual bit comprises: And if the representative bit indicates a packet reception error, allocating one individual bit indicating whether a reception error exists for each corresponding received packet of the group in addition to the representative bit.

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