KR101298544B1 - Apparatus and method for processing of received packets in mobile communication system - Google Patents

Abstract

The present invention relates to an apparatus and a method for processing a received packet in a mobile communication system. The method for processing a received packet in a mobile communication system includes: when a MAC processor restores a packet by using a predetermined number of frames, the MAC processing unit transmits to a previous packet. Determining whether or not to wait for retransmission, and setting information indicating whether the MAC processor is waiting for retransmission for the previous packet to the restored packet using one section of the TCP header according to the determination. Including the process of transmitting the restored packet to the IP processing unit, it is possible to expect almost the same performance as the case of performing the restoration in the MAC layer by modifying the operation of the TCP layer without performing the restoration in the MAC layer. Since additional order restoration is not performed, the buffer size required for the MAC processing unit The advantage is that the speed of the interface is reduced to make implementation easier.

MAC, IP, TCP, Sequence Restoration, Packet Restoration

Description

Apparatus and method for receiving packet processing in mobile communication system {APPARATUS AND METHOD FOR PROCESSING OF RECEIVED PACKETS IN MOBILE COMMUNICATION SYSTEM}

1 is a block diagram showing the configuration of a receiving packet processing apparatus of a mobile communication system according to the present invention;

2 is a flowchart illustrating a procedure of a received packet processing method of a MAC processing unit in a mobile communication system according to an embodiment of the present invention;

3 is a flowchart illustrating a procedure of a received packet processing method of a TCP processing unit in a mobile communication system according to an embodiment of the present invention;

4 illustrates a format of a TCP header according to the present invention, and

5 is a graph comparing TCP performance for the existing technology and the technology according to the present invention.

The present invention relates to a receiving packet processing apparatus and method of a mobile communication system.

In the wired network environment, most packet loss is caused by network congestion. When a packet loss occurs due to the network congestion, a transmission control protocol (hereinafter referred to as 'TCP') drives a congestion control mechanism that suppresses the amount of data transmission. Here, TCP is a transmission protocol for reliably delivering data packets. The TCP congestion control mechanisms include slow start, congestion avoidance, and fast retransmit / recovery methods, and adjust the amount of transmission according to network conditions through the mechanism.

On the other hand, in the wireless network environment, the characteristics of the wireless link, that is, the congestion of the network, are more frequent, that is, the frequency of packet loss due to high error rate and handoff is greater. Therefore, if the control mechanism of TCP presented according to the characteristics of the wired network environment is applied to the mobile wireless network environment as it is, an inappropriate situation occurs. That is, the TCP determines that packet loss due to the characteristics of the radio link is also caused by congestion of the network, and reduces the transmission speed by processing in the same manner as packet loss due to congestion of the network. For example, the slow start or fast recovery mechanism reduces the congestion window size. As a result, the bandwidth of the link is wasted due to repeated packet loss, which causes a problem that the performance of the entire network is degraded.

Therefore, TCP, which has been suitably developed for the wired network, is improved according to the characteristics of the wireless network, and the cause of packet loss is regarded as an error rather than a packet loss due to congestion, so that the TCP protocol can be effectively used in the wireless network. This is recognized as an important issue.

In the prior art proposed to prevent the degradation of TCP performance in the wireless environment, as described above, a technique relating to a method for dealing with a packet loss after occurrence, and another method to reduce the packet loss itself detected by the TCP layer Techniques for more efficient retransmission in the MAC layer.

The retransmission scheme in the MAC layer includes a stop-n-go scheme and a selective-repeat scheme. The stop-and-go scheme is simple to implement and is based on IEEE 802.11. It is used in wireless LAN. However, because of poor performance, many other wireless networks use the selective retransmission scheme.

In the case of using the selective retransmission method, when the packet reception of the MAC processing unit is completed, the order of the retransmitted packet and the non-retransmitted packet may be reversed. Therefore, when the MAC processing unit sends the packet to the TCP layer in the order of reception completion, the TCP layer detects a packet sequence error, which causes a duplicate ACK and is eventually recognized as a packet loss. May occur. In particular, the higher the speed wireless environment, the higher the probability that the packet loss is recognized. To prevent this, the MAC layer uses a method of restoring the order of the packets and uploading them to the TCP layer. As such, when restoring the order of packets in the MAC layer, an improvement in TCP throughput may be expected compared to the case where the order of the packets is not restored.

However, in order to recover the order in the MAC layer, a buffer size proportional to retransmission time and packet error rate is required, and a fast inter-layer interface speed is required to wait until the order of the packet is restored and send it to the upper layer at once. . This is not a big problem when the speed of the wireless network is slow, but if the wireless network evolves faster and faster, the necessary buffer size is increased and the interface speed is high, which makes it difficult to implement a single chip. In addition, there is a disadvantage that the power consumption is increased.

In addition, if the retransmission scheme and the TCP operation on the radio link are not properly harmonized, performance degradation will occur. Therefore, there is a need for a method capable of preventing TCP performance degradation through a linkage operation between the MAC layer and the TCP layer that is responsible for retransmission on the wireless link.

An object of the present invention is to provide an apparatus and method for receiving packet processing in a mobile communication system.

Another object of the present invention is to provide an apparatus and a method for processing a received packet which can prevent TCP performance degradation through a linkage operation between a MAC layer and a TCP layer in a mobile communication system.

Another object of the present invention is to provide an apparatus and a method for processing a received packet which can prevent TCP performance degradation by modifying the operation of the TCP layer without performing an order restoration in the MAC layer of the mobile communication system.

According to an embodiment of the present invention to achieve the above object, the received packet processing method in a mobile communication system, when the packet is restored by using a predetermined number of frames received, the MAC processing unit retransmits the previous packet Determining whether to wait, and setting information indicating whether the MAC processor is waiting for retransmission for the previous packet to the restored packet using one section of the TCP header according to the determination, and restoring And transmitting the packet to the IP processor.

According to an embodiment of the present invention to achieve the above object, the reception packet processing apparatus in the mobile communication system, when restoring the packet using a predetermined number of frames received, whether or not waiting for retransmission for the previous packet; And a MAC processor for setting information indicating whether or not the MAC processor is waiting for retransmission for the previous packet to the restored packet using one section of the TCP header according to the determination; And an IP processor for receiving the restored packet in which information indicating whether to wait for retransmission for the previous packet is set.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, the present invention will be described with respect to a received packet processing apparatus and method of a mobile communication system.

1 is a block diagram showing the configuration of a receiving packet processing apparatus of a mobile communication system according to the present invention. The received packet processing apparatus includes a MAC processing unit 101, an IP processing unit 103, and a TCP processing unit 105 for receiving data. Here, the MAC processing unit 101 and the TCP processing unit 105 may include buffers 107 and 109, and the buffers 107 and 109 may be external buffers or internal buffers.

The MAC processing unit 101 restores the IP packet from the data received from the radio link and transfers the IP packet to the IP processing unit 103. When a data loss occurs, the MAC processing unit 101 requests retransmission to the transmitting MAC processing unit 101.

The IP processing unit 103 performs a normal IP layer operation, examines an IP packet header received from the MAC processing unit 101, and transmits TCP data excluding the IP packet header to the TCP layer.

The TCP processing unit 105 performs a normal TCP layer operation, receives the TCP data from the IP processing unit 103, restores the order, and transfers application layer data excluding the TCP header to the application layer.

2 is a flowchart illustrating a method of processing a received packet by a MAC processing unit in a mobile communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the MAC processor 101 checks whether a frame is received in step 201. If the frame is not received, the MAC processing unit 101 proceeds to step 221 and checks whether the timer of the frame has expired. If the timer of the frame has not expired, the process returns to step 201 to receive the frame. Check if it is. When the timer of the frame expires, the MAC processor 101 sets an expiration indication on the timer in step 223, and returns to step 201 to check whether the frame is received.

When the frame is received in step 201, the MAC processor 101 checks whether the timer of the frame is set in step 203. When the timer of the frame is set, the MAC processing unit 101 releases the setting of the timer in step 204 and proceeds to step 205 to check whether there is an error in the frame. If the timer of the frame is not set, the MAC processing unit 101 proceeds directly to step 205 to check whether there is an error in the frame.

If there is an error in the frame, the MAC processing unit 101 requests retransmission for the frame to the transmitter in step 225, sets a timer for the frame, and returns to step 201 to check whether the frame is received. . If there is no error in the frame, the MAC processing unit 101 attempts to restore the packet in step 207 and checks whether the packet is restored. If the packet is not recovered, the MAC processing unit 101 returns to step 201 to check whether another frame is received. Here, one TCP / IP packet is generally divided into small frame units on a wireless link and transmitted. The MAC processing unit 101 receives the frame and stores the frame in an internal buffer 107. When all the frames are normally received, the corresponding TCP / IP packet is transmitted to the upper layer. When the packet is restored, the MAC processing unit 101 checks whether a timer expiration indication is present in the restored packet in step 209. Since the timer expiration indication is present because the timer is set while waiting for retransmission, the WAIT bit of the TCP / IP packet restored after the timer expiration may be set to 0 because the timer expiration indication is not present.

When the timer expiration indication does not exist in the recovered packet in step 209, the MAC processor 101 checks whether a timer set for some frames of the previous packet exists in step 215. That is, it checks whether there is a packet waiting for retransmission for some frames of the previous packet. If there is a timer set for the previous frame, the MAC processor 101 sets the WAIT bit to 1 in step 217, and proceeds to step 213 to transmit the recovered packet to the IP processor 105. In this case, all packets after the packet waiting for retransmission have the WAIT bit set to one. When there is no timer set for the previous frame, that is, when all previous packets are restored, the MAC processing unit 101 sets the WAIT bit to 0 in step 219, and proceeds to step 213 to restore the restored packet. The packet is transmitted to the IP processing unit 105. Here, the WAIT bit is defined as one bit among six reserved bits of the TCP header of FIG. 4.

When there is a timer expiration indication in the restored packet in step 209, the MAC processor 101 sets the WAIT bit to 0 in step 211, releases the timer expiration indication for the corresponding frame, and then in step 213. Proceeds to and transmits the restored packet to the IP processing unit 105. Thereafter, the MAC processing unit 101 returns to step 201 to check whether the frame is received. Thereafter, the MAC processing unit 101 terminates the algorithm according to the present invention.

3 is a flowchart illustrating a procedure of a received packet processing method of a TCP processing unit in a mobile communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the TCP processor 105 initializes wait_tcp_flag to 0 in step 301 and checks whether a packet is received in step 303. In this case, setting the wait_tcp_flag to 1 means to perform a normal TCP operation without waiting any longer even if a packet error occurs. When the packet is received, the TCP processing unit 105 checks whether there is an error in the order of the received packet in step 305. That is, it is checked whether the sequence number of the waiting packet is different from the sequence number of the arrived packet.

When an error is not checked in the order of the received packets, that is, when the sequence number of the waiting packet is the same as the sequence number of the arriving packet, the TCP processing unit 105 performs a normal TCP operation in step 319. In step 321, it is checked whether the buffer 109 is empty. In other words, the packet is transmitted to the application layer until the last packet in which the sequence numbers of the packets stored in the buffer 109 are continuous, and the ACK packet corresponding to the sequence number is generated and transmitted to the transmitting side. Check if it is empty. When the buffer 109 is empty, the TCP processing unit 105 initializes the wait_tcp_flag to 0 in step 323, and returns to step 303 to check whether a packet is received. When a packet remains in the buffer 109, the TCP processing unit 105 keeps the wait_tcp_flag as it is, and returns to step 303 to check whether a packet is received.

When an error is checked in the order of the received packets, that is, when the sequence number of the waiting packet and the sequence number of the arriving packet are different, the TCP processing unit 105 determines in step 307 that the packet has already been received. Check for cognition. Here, if the received packet is a packet already received, the packet means a retransmitted packet, the sequence number of the packet will be smaller than the waiting sequence number, if the received packet is not already received packet The sequence number of the packet will be greater than the sequence number waiting.

When the received packet is a received packet, that is, when the sequence number of the packet is smaller than the waiting sequence number, the TCP processing unit 105 performs a normal TCP operation in step 309, and proceeds to step 303. Go back and check that the packet is received. At this time, the wait_tcp_falg is maintained as it is.

When the received packet is not a packet that has already been received, that is, a packet is larger than the waiting sequence number, the TCP processing unit 105 checks whether the wait_tcp_falg is 1 in step 311. When the wait_tcp_flag is 1 day, the process proceeds to step 309 and performs normal TCP operation without waiting. At this time, the wait_tcp_falg is maintained as it is. When the wait_tcp_flag is 0, the TCP processor 105 checks whether the WAIT bit is 1 at 313. That is, the MAC processing unit 101 checks whether there is a packet waiting for retransmission.

When the WAIT bit is 1, the TCP processing unit 105 stores the packet in the buffer 109 in step 317, and proceeds to step 303 to check whether a packet is received. At this time, the ACK packet for the packet is not generated. When the WAIT bit is 0, the TCP processing unit 105 needs TCP retransmission due to the retransmission failure of the MAC layer, so in step 315, the wait_tcp_flag is set to 1 and the received packet is stored in the buffer 109. After generating and transmitting ACK packets corresponding to the number of packets stored in the buffer 109, the process returns to step 303 to check whether packets are received. Here, the ack numbers of the ACK packets are currently waiting sequence numbers. Thereafter, the TCP processing unit 105 terminates the algorithm according to the present invention.

For example, when the MAC processing unit 101 restores packets in the order of sequence numbers 1,2,4,3, that is, when packet 4 is restored while waiting for retransmission for packet 3, the MAC processing unit ( 101 sets the WAIT bit of the 4th packet to 1 and transmits the WAIT bit to the TCP processing unit 105. At this time, the TCP processing unit 105 detects an order error by the arrival of packet 4 after packet 2, and at this time, since the WAIT bit of the packet 4 is 1, the TCP processor 105 does not generate the ACK packet. The second packet is stored in the buffer 109.

Thereafter, the MAC processing unit 101 receives the third packet through retransmission, restores the received third packet, and sets the WAIT bit of the third packet to 0 to the TCP processing unit 105. send. In this case, the TCP processing unit 105 stores the packet 3 in the buffer 109, transmits the packet 3 to the application layer in order 3, 4, and then generates a TCP ACK packet to the generating and transmitting side.

As another example, when the MAC processing unit 101 attempts to restore packets in the order of sequence numbers 1,2, 4, and 3, retransmission fails for packet 3 and packet 5 is restored, that is, packet 3 When packet 5 is restored in a situation in which retransmission fails for the retransmission timer for, the MAC processing unit 101 sets the WAIT bit of the 4 packet to 1 and transmits the packet to the TCP processing unit 105. At this time, the TCP processing unit 105 detects an order error by the arrival of packet 4 after packet 2, and at this time, since the WAIT bit of the packet 4 is 1, the TCP processor 105 does not generate the ACK packet. The second packet is stored in the buffer 109.

Thereafter, the MAC processor 101 sets a timer expiration indication for retransmission of the third packet, and restores the packet # 5 to the TCP processing unit 105 when the timer expiration indication is set. Send with bit set to 0. In this case, the TCP processing unit 105 detects an order error because packet 5 arrives instead of packet 3, and the wait_tcp_flag is set to 1 because the WAIT bit of packet 5 is 0. In this case, two TCP ACK packets corresponding to packet # 4 and packet # 5 stored in the buffer 109 are generated and transmitted to the sender.

5 is a graph comparing TCP performance of the existing technology and the technology according to the present invention. If the probability of retransmission failure is as low as about 10 ^-4 or less, as in a conventional wireless network, the technique according to the present invention has almost the same performance as the conventional technique of order restoration in the MAC layer. In addition, as shown in FIG. 5, when the probability of retransmission failure is a large order of ^10-3 orders, in the prior art in which the MAC layer performs order restoration (5a), the MAC layer exhibits an average performance of 3.7 Mbps. In the case of the technique 5b according to the present invention which does not perform this order restoration, it can be seen that the average performance is 3.4 Mbps. In other words, it can be seen that there is no significant difference in performance.

Here, the example according to the present invention is also applicable to a server mainly performing TCP communication and a base station processing a MAC layer of a wireless network. In particular, the TCP transmitter does not need to be changed, and only the receiver needs to be changed. It is effective when applied to a wireless terminal.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention provides a receiving packet processing apparatus and method that can prevent the TCP performance degradation through the interworking operation of the MAC layer and the TCP layer in the mobile communication system, the TCP layer without having to restore the order in the MAC layer You can expect the same performance as the case of order restoration in the MAC layer by modifying the operation of, and since the MAC processor does not perform order restoration, it is easy to implement by reducing the buffer size required for the MAC processor and the interface speed with the upper layer. There is an advantage to this. In addition, since the MAC processor basically manages the timer for indicating how long to wait for retransmission, the TCP processor does not need to manage the timer, so there is an advantage that the implementation complexity is not so great.

Claims (14)

In the received packet processing method in a mobile communication system, Determining whether the MAC processor waits for retransmission of a previous packet when restoring the packet by using a predetermined number of frames received; Setting, by the MAC processor, information indicating whether the previous packet is waiting for retransmission to the restored packet by using one section of the TCP header, and transmitting the restored packet to the IP processing unit according to the determination. Method comprising a. The method of claim 1, When an error is detected in a specific frame, the MAC processor requesting retransmission for the frame and setting a timer for the frame; And when the timer expires, setting the expiration indication of the timer by the MAC processor. The method of claim 2, When the packet is restored, checking, by the MAC processor, whether a timer expiration indication is set in the restored packet; Determining whether the MAC processor waits for retransmission of a previous packet when a timer expiration indication is not set in the restored packet; When the timer expiration indication is set in the restored packet, the MAC processing unit sets that the previous packet is not waiting for retransmission by using the interval, releases the expiration indication of the corresponding timer, and then restores. And transmitting the packet to the IP processing unit. The method of claim 1, And inspecting, by the IP processing unit, an IP packet header received from the MAC processing unit, and delivering a TCP packet except the IP packet header to a TCP layer. 5. The method of claim 4, When the TCP packet is received from the IP processor, checking whether the packet is in error by using the sequence number of the TCP header; When an error is detected in the order of the packet, checking, by the TCP processor, whether the MAC processor is waiting for retransmission for a previous packet by using the header of the packet; And when the MAC processor is checked that it is waiting for retransmission, storing the packet in a buffer and not generating an ACK packet. 6. The method of claim 5, And when the MAC processor is checked that it is not waiting for retransmission, the TCP processor storing the packet in a buffer and generating ACK packets as many as the number of packets in the buffer. 6. The method of claim 5, When an error is detected in the order of the packet, the TCP processor checks whether the packet is already received, performs a normal TCP operation when the packet is already received, and receives the packet. When the packet is not a packet, checking whether the MAC processor is waiting for retransmission of a previous packet by using the header of the packet; And when the error is not detected in the order of the packet, performing the normal TCP operation by the TCP processing unit. In the received packet processing apparatus in a mobile communication system, When restoring the packet using a predetermined number of frames received, it is determined whether a previous packet is waiting for retransmission, and according to the determination, the MAC processor uses one section of the TCP header to restore the packet. A MAC processing unit for setting information indicating whether to wait for retransmission for the previous packet at  And an IP processing unit for receiving the restored packet in which information indicating whether to wait for retransmission for the previous packet is set from the MAC processing unit. 9. The method of claim 8, The MAC processor, when an error is detected in a specific frame, requests retransmission for the frame, sets a timer for the frame, and sets an expiration indication of the timer when the timer expires. Device. The method of claim 9, When the MAC processor restores the packet, the MAC processor determines whether a timer expiration indication is set in the restored packet. When a timer expiration indication is not set in the restored packet, it is determined whether a retransmission is waiting for a previous packet, When a timer expiration indication is set in the restored packet, the interval is set to not wait for retransmission for the previous packet by using the interval, the expiration indication of the corresponding timer is released, and then the restored packet is read. Device for transmitting to the IP processing unit. 9. The method of claim 8, The IP processing unit, characterized in that for inspecting the IP packet header received from the MAC processing unit, and delivers the TCP packet except the IP packet header to the TCP processing unit. The method of claim 11, When a TCP packet is received from the IP processing unit, the TCP header sequence number is used to check whether there is an error in the sequence of the packet, and when an error is detected in the sequence of the packet, the previous packet is determined using the header of the packet. The packet processing unit further checks whether the MAC processing unit is waiting for retransmission, and when the MAC processing unit is waiting for retransmission, stores the packet in a buffer and does not generate an ACK packet. Device characterized in that. 13. The method of claim 12, And when the TCP processing unit determines that the MAC processing unit is not waiting for retransmission, stores the packets in a buffer and generates ACK packets as many as the number of packets in the buffer. 13. The method of claim 12, When the TCP processor detects an error in the order of the packets, the TCP processor checks whether the packets are already received, and when the packets are already received, performs a normal TCP operation. When the packet is not a packet already received, the MAC processing unit checks whether the packet is waiting for retransmission for a previous packet by using the header of the packet, and when an error is not detected in the order of the packet, Device for performing a TCP operation.

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