Multi-path information packet coding and scheduling method for minimizing time delay

Abstract

The invention discloses a multi-path information packet coding and scheduling method for minimizing time delay, which comprises the following steps of: updating lost information packets at a sending end through feedback information, and planning a sending sequence of each packet in an information packet scheduling window according to different transmission rates, feedback delays and path erasing probabilities of multiple paths; according to the delay of the feedback information, the transmitting end estimates the total number of lost information packets according to the feedback information at the beginning of a scheduling window and arranges repair coding packet transmission at the head of the scheduling window, and a forward error correction coding packet is transmitted at the tail of the scheduling window; the method is used for overcoming data packet loss caused by channel errors. According to the method, the information packet loss in the feedback delay is estimated, the information packet and the coding packet are sent according to the receiving sequence, and the end-to-end time delay of information packet transmission in the feedback lagging multipath network is reduced under the condition of almost no information redundancy by introducing the repair coding packet and the forward error correction coding packet.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication standardization process, and in particular relates to a multi-path information packet encoding and scheduling method for minimizing delay. Background Art

[0002] With the continuous development of modern communication technology, communication devices are often equipped with various network access methods. For example, mobile phones can communicate simultaneously through Wi-Fi, LTE and Bluetooth. Therefore, multipath communication has become a promising technology to improve the reliability and capacity of wireless networks. At the same time, this technology can effectively reduce the delay of communication. Multipath communication can aggregate the spatial / frequency diversity of various paths and provide great flexibility between diversity and multiplexing. However, the correlation, dynamics and asymmetry of each path in the multipath make the packet scheduling in multipath communication quite challenging, and the design of packet scheduling also needs to adapt to different Quality of Service (QoS) goals. Therefore, in order to improve the delay and throughput performance of packet transmission, the design of packet scheduling algorithm under the multipath system model has become an important part of today's communication protocol.

[0003] The main difficulties of multipath packet scheduling are concentrated in the following four points: First, multipath packet scheduling should take into account the asymmetry of network paths, that is, different paths may have different transmission rates, path elimination probabilities and round-trip times (RTTs) to effectively utilize multipath scenarios; second, packet scheduling algorithms must balance multiple QoS objectives, such as maximizing average throughput, reducing overall data transmission time, minimizing end-to-end delay or minimizing the size of the receiver's out-of-order buffer, and maintaining jitter smoothness; packet erasure events between paths may be correlated; finally, multipath packet scheduling algorithms should adapt to the dynamics of the network environment. In real environments, network conditions fluctuate over time and vary greatly in different environments. Summary of the invention

[0004] The present invention aims to provide a multi-path information packet coding and scheduling method with minimized delay, which estimates the number of lost information packets through feedback information when each path has an asymmetric information packet transmission rate, erasure probability and feedback delay, combines the existing random linear network coding technology, and utilizes a priori and a posteriori error correction technology to minimize the end-to-end delay of information packet transmission while maximizing the use of multi-path channel capacity.

[0005] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0006] A method for multipath information packet encoding, scheduling and real-time transmission under delayed feedback conditions, which specifically includes the following steps:

[0007] Step 1: Before the transmission starts, the length of the scheduling window is determined according to the different transmission rates of each path in the multipath channel, that is, the number of paths is set to Z, and the time for each path to transmit a packet is T1, T2, ...T Z , then the length of the scheduling window is the least common multiple of the transmission time of each path, that is, w = lcm(T1, T2, ...T Z );

[0008] Step 2: At the beginning of transmission, the sender has N packets waiting to be transmitted, and the channel erasure probability of each path is e1, e2, ...e Z , the transmission time is T1, T2, ...T Z , the total number of packets transmitted in a scheduling window is n w ,Only when a single path completes the transmission of an information packet or a coded packet can the next packet be transmitted on that path, and the transmission of each path is carried out in parallel;

[0009] Step 3: When the receiving end successfully receives the information packet, it immediately uploads the information packet to the application layer and feeds back the feedback information of the information packet to the sending end. The feedback information of each path is fed back after the feedback delay D1, D2, ..., D Z Arrives at the sending end;

[0010] Step 4: When the sender starts to transmit, if it is the beginning of the scheduling window, the sender first confirms the packets that the receiver has not successfully received through the received feedback information, and then confirms the packets through the feedback delay D and the erasure probability of each path e1, e2, ...e Z , estimate the total number of unsuccessfully received packets, encode these estimated unsuccessfully received packets into repair coded packets, and decide the number of sent packets, repair coded packets, and forward error correction coded packets, the total number is n w , arrange these n according to the receiving time order of each sending position in the scheduling window w The sending position of each packet is determined to eliminate the out-of-order reception problem caused by different transmission rates of multiple paths. The repair coding packet is received first, followed by the information packet, and finally the forward error correction coding packet. After completing the scheduling, the sender sends the information packet on the currently available path according to the current scheduling.

[0011] Step 5: When the sender starts to transmit, if it is not the start of the scheduling window at this time, the sender first confirms the packets that the receiver has not successfully received through the received feedback information, and inserts these lost packets into the head of the current sending queue, and re-arranges the sending position of the lost packets and the remaining unsent packets and coded packets in the scheduling window according to the order of receiving time, so as to give priority to the retransmission of the lost packets. After completing the scheduling arrangement, the sender sends the packets on the currently available path according to the current scheduling arrangement;

[0012] Step 6: When the receiving end successfully receives the data packet, repeat step 3;

[0013] Step 7: After completing steps 1-6, repeat steps 4-6 until N information packets are transmitted.

[0014] Furthermore, the total number of packets that can be transmitted in a scheduling window in step 2 is n w is the length of the scheduling window w and the transmission time of each path T1, T2, ... T Z OK, w for:

[0015]

[0016] Furthermore, in step 4, the known number of unconfirmed packets u and the erasure probability of each path e1, e2, …e are obtained through feedback information in each scheduling window. Z and feedback delays D1, D2, …, D Z The estimated number of unconfirmed packets is recorded as For the transmitter, each path has a feedback delay of D1, D2, ..., D Z The number of unconfirmed packets sent within is known, and is denoted as k1, k2, ..., k Z , from which we can derive the estimated number of unconfirmed packets, namely for

[0017]

[0018] Furthermore, step 4 uses the erasure probability e1, e2, …e of each path Z , the length of the scheduling window w and the transmission time of each path T1, T2, ...T Z Determine the number of information packets, repair coding packets and forward error correction coding packets sent, which are:

[0019] Repair code package:

[0020] Information Packet:

[0021] Forward error correction coding packet:

[0022] The multipath information packet encoding and scheduling method of the present invention which minimizes delay has the following advantages:

[0023] 1. This method fully considers the different transmission rates, channel erasure probabilities and feedback delays of each path in the multipath case, and uses the asymmetric characteristics of each path to make scheduling decisions, thus eliminating the degradation of transmission performance caused by the asymmetric characteristics of each path to a certain extent.

[0024] 2. This method can complete the a priori and a posteriori error correction mechanisms by sending repair coding packets and forward error correction coding packets, and reasonably estimate the number of lost packets in the case of feedback delay, thereby efficiently utilizing the channel capacity to complete the transmission of each scheduling window packet.

[0025] 3. This method reorders the packet sending order within the scheduling window so that the packets in the sending queue are sent in the order of the receiving time of each sending position within the scheduling window, so that the sending queue can be received in order at the receiving end, thereby eliminating the disorderly reception problem caused by different transmission rates of multiple paths. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of an example of the transmission and encoding process of the transmitting end according to an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of generating a coding packet according to an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of a flow chart of an information packet encoding and transmission scheme according to an embodiment of the present invention;

[0029] Figure 4 is a schematic diagram of simulation performance of multipath erasure probability according to an embodiment of the present invention;

[0030] Figure 5 It is a schematic diagram of simulation performance of multipath feedback delay according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to better understand the purpose, structure and function of the present invention, a multi-path information packet encoding and scheduling method for minimizing delay of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0032] The present invention is applicable to a multi-path communication network with feedback delay. The sending end makes a corresponding scheduling strategy according to the characteristics of asymmetric paths in the multi-path channel (transmission rate, channel erasure probability and feedback delay); to ensure the orderly arrival of information packets, the sending end divides the scheduling of information packets into a plurality of scheduling windows for scheduling, and makes each information packet sent in the scheduling window in the receiving order; at the beginning of each scheduling window, the sending end will combine known feedback information and channel path characteristics to estimate the actual number of lost information packets, and encode the information packets of unknown receiving state into repair coding packets through random linear network coding and send them according to the estimated number of lost information packets, and send forward error correction network coding packets to compensate for the loss of subsequent information packets when it is unknown which information packets are lost.

[0033] The present invention specifically comprises the following steps:

[0034] A method for multipath information packet encoding, scheduling and real-time transmission under delayed feedback conditions, which specifically includes the following steps:

[0035] Step 1: Determine the scheduling window length. Specifically, first determine the scheduling window length based on the different transmission rates of each path in the multipath channel. If the number of paths is assumed to be Z, and the time required to transmit a data packet determined by the transmission rates of each path is T1, T2, ... T Z , then the length of the scheduling window is the least common multiple of the transmission time of each path, that is, w = lcm(T1, T2, ... T Z ). This step ensures that all paths can synchronously complete the transmission of their planned packets within a scheduling window period, thereby facilitating the scheduling of multi-path information packets.

[0036] Step 2: Schedule the transmission of data packets within the window. Specifically, at the beginning of the transmission, the sender has N packets waiting to be transmitted, considering that the channel erasure probability of each path is e1, e2, … e Z And the transmission time is T1, T2, ...T Z , the total number of packets that can be transmitted in a scheduling window is n w ,Only when a single path completes the transmission of an information packet or a coded packet can the next packet be transmitted on that path, and the transmission of each path is carried out in parallel;

[0037] Step 3: Packet processing and feedback at the receiving end. Specifically, when the receiving end successfully receives the information packet, it will immediately upload the information packet to the application layer and feedback the reception status of the information packet to the sending end. The feedback information will be delayed by a certain amount of time D1, D2, ..., D Z Arrives at the sender. This step is the key to updating the sender's status in real time so that the sender can adjust the next sending strategy according to the latest situation.

[0038] Step 4: Packet encoding, scheduling and sending at the beginning of the scheduling window. Specifically, when the sender starts to transmit, if this is the beginning of the scheduling window, the sender first confirms the packets that the receiver has not successfully received through the received feedback information, and then sends them to the receiver through the feedback delay D1, D2, ..., D Z And the erasure probability of each path e1,e2,…e Z , the transmitter knows that the feedback delay D1, D2, ..., D Z The number of information packets and coded packets sent within the path, according to the erasure probability e1, e2, ... e Z Obtain the expected number of unknown state packets lost and the expected number of unknown state coded packets received, thereby estimating the total number of unsuccessfully received packets. Encode these estimated unsuccessfully received packets into repair coded packets, and determine the number of sent packets, repair coded packets, and forward error correction coded packets, the total number of which is n. w , arrange these n according to the receiving time order of each sending position in the scheduling window w The sending position of each packet is determined to eliminate the out-of-order reception problem caused by different transmission rates of multiple paths. The repair coding packet is received first, followed by the information packet, and finally the forward error correction coding packet. After completing the scheduling, the sender sends the information packet on the currently available path according to the current scheduling.

[0039] Step 5: Scheduling and sending packets within the scheduling window. Specifically, when the sender starts to transmit, if it is not the start of the scheduling window at this time, the sender first confirms the packets that the receiver has not successfully received by receiving the feedback information fed back by the receiver, and inserts these lost packets into the head of the current sending queue, and re-arranges the sending position of the lost packets and the remaining unsent packets in the scheduling window according to the order of receiving time, so as to give priority to the retransmission of the lost packets. After completing the scheduling arrangement, the sender sends the packets on the currently available path according to the current scheduling arrangement;

[0040] Step 6: When the receiving end successfully receives the data packet, repeat step 3;

[0041] Step 7: After completing steps 1-6, repeat steps 4-6 until the N information packets that the sender initially needs to transmit are transmitted.

[0042] The scheduling window length w defined in step 1 is determined by the asymmetric packet transmission times T1, T2, ... T Z The lowest common multiple of is determined, w is:

[0043] w=lcm(T1,T2,…T Z ).

[0044] The total number of packets that can be transmitted in a scheduling window in step 2 is n w is the length of the scheduling window w and the transmission time of each path T1, T2, ... T Z OK, w for:

[0045]

[0046] In step 4, the known number of unconfirmed packets u and the erasure probability of each path e1, e2, …e are obtained through feedback information in each scheduling window. Z and feedback delays D1, D2, …, D Z The estimated number of unconfirmed packets is recorded as For the transmitter, each path has a feedback delay of D1, D2, ..., D Z The number of unconfirmed packets sent within is known, and is denoted as k1, k2, ..., k Z , from which we can derive the estimated number of unconfirmed packets, namely for

[0047]

[0048] Step 4: The erasure probability of each path is e1, e2, ... e Z , the length of the scheduling window w and the transmission time of each path T1, T2, ...T Z Determine the number of information packets, repair coding packets and forward error correction coding packets sent, which are:

[0049] Repair code package:

[0050] Information Packet:

[0051] Forward error correction coding packet:

[0052] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings.

[0053] Figure 1 1 is a schematic diagram of an example of a transmission and encoding process at a transmitting end and a decoding process at a receiving end under the delayed feedback condition mentioned in the first embodiment of the present invention.

[0054] There are a total of Z = 3 paths in the multipath channel. The fastest path packet transmission time is recorded as one time slot, that is, the first path. The transmission time of the other two paths is 2 time slots and 4 time slots. For the convenience of observation and simulation, the feedback information delay of each path is D1, D2, ..., D ZAll of them are D = 2 time slots, that is, if the information packet sent in the i-th time slot is successfully received, its feedback information will reach the sender at the end of the i+D-th time slot. Assume that the erasure probability of information packets on each path is [0.1, 0.2, 0.3].

[0055] Before transmission begins, set system parameters according to application requirements, including: scheduling window length lcm (T1, T2, ... T Z )=4, the total number of packets that can be transmitted in a scheduling window is n w =7, feedback delay D=2, and the number of forward error correction coding packets in one scheduling window is f=1.

[0056] At the beginning of the first time slot, no information packets need to be retransmitted. The sender schedules the 7 information packets and coding packets that need to be sent in the scheduling window so that these 7 information packets and coding packets can reach the receiving end in order under the condition of asymmetric path transmission rate, and adds f = 1 forward error correction coding packets at the end of the sending queue of the scheduling window. After the scheduling is completed, the sender immediately sends x1, x3 and c 1～6 On three paths respectively, packet x1 arrives at the receiving end, which uploads it to the application layer and sends feedback to the sending end for confirmation.

[0057] At the beginning of the second time slot, the transmitter does not receive feedback information. The transmitter sends x2 on path 1 according to the original schedule. At the end of the second time slot, the receiver successfully receives x2 and uploads it, but x3 is erased by the channel and feedback information is sent to the transmitter.

[0058] At the beginning of the third time slot, the sender does not receive feedback information. The sender transmits x4 on path 1 and x6 on path 2 according to the original schedule. Packet x6 arrives at the receiver, which uploads it to the application layer and sends feedback information to the sender for confirmation, but packet x6 is deleted by the channel.

[0059] At the beginning of the 4th time slot, the transmitter does not receive any feedback information. The transmitter sends x5 on path 1 according to the original schedule. At the end of the 4th time slot, the receiver successfully receives x4 and c 1～6 , the receiving end feeds back information confirmation to the sending end.

[0060] At the beginning of the 5th time slot, the transmitter arrives at the beginning of the second scheduling window. At this time, the transmitter learns from the feedback that packet x5 is lost, and estimates that another packet will be lost in the unknown receiving area. Therefore, the transmitter adds a repair coding packet to the head of the sending queue, and adds f = 1 forward error correction coding packets to the end of the sending queue in the scheduling window. The transmitter schedules the 7 information packets and coding packets that need to be sent in the scheduling window so that these 7 information packets and coding packets can reach the receiving end in order under the condition of asymmetric path transmission rate. After the scheduling is completed, the transmitter immediately sends c 1～6 , x8 and c 1～12 On three paths respectively. Packet c 1～6 Arrives at the receiving end and sends feedback to the sending end for confirmation.

[0061] At the beginning of the 6th time slot, the transmitter sends packet x7 on path 1 according to the original scheduling plan. Packet x7 is deleted by the channel.

[0062] At the beginning of the 7th time slot, the sender sends packets x9 and x1 on path 1 and path 2 respectively. 11 . Information packets x9 and x 11 When it reaches the receiving end, the receiving end uploads it to the application layer and sends feedback to the sending end for confirmation.

[0063] At the beginning of the 8th time slot, the sender sends x on path 1. 10 At the end of the 8th time slot, the receiver successfully receives x 10 、x 11 and c 1～11 , the receiving end feeds back information confirmation to the sending end.

[0064] In the above 1-8 time slots, the average end-to-end transmission delay is 6.3 time slots, and the transmission efficiency is 1, that is, the receiving end does not receive any redundant information.

[0065] Figure 2 is a schematic diagram of generating a coded packet provided by an embodiment of the present invention. If the transmitting end determines that a coded packet needs to be sent according to feedback information, the information packet in the coding window is encoded by random linear network coding. Specifically, if the coding window contains w data packets, the coded packet is obtained by multiplying the information packet in the coding window by the random coding coefficient and then summing them. The coding coefficient is generally selected from a finite field.

[0066] Figure 4: is a schematic diagram of the simulation performance of the embodiment of the present invention regarding the multipath erasure probability. The three schemes in the figure are the scheme proposed by the present invention, the retransmission scheme, and the reordered retransmission scheme. The reordered retransmission scheme is based on the retransmission scheme. The transmitting end obtains the reception and decoding status of the information packet through feedback, sends the information packet in the receiving order within the scheduling window, and updates the scheduling in real time according to the feedback information. Specifically, for the convenience of observation and simulation, the feedback delay D1, D2, ..., D of the fixed Z = 3 paths is Z When D = 15 time slots and the erasure probability of each path is [0.1, 0.2, 0.3], the erasure probability increase coefficient e0 of each path is set to 0 to 0.1 with a step size of 0.02, and the average end-to-end delay of sending N = 100 packets is observed. Figure 4 The results show that when the erasure probability increase coefficient e0 increases, the average end-to-end delay of the three schemes increases with the increase of e0. The end-to-end delay of the reordering and retransmission scheme is significantly better than the retransmission scheme based on the reordering of information packets within the scheduling window, thus verifying the improvement of the end-to-end delay performance by reordering. When the proposed scheme uses the a priori and a posteriori error correction mechanism, the end-to-end delay is better than the reordering and retransmission scheme.

[0067] Figure 5 : is a schematic diagram of the simulation performance of the embodiment of the present invention regarding the multi-path feedback delay. The three schemes in the figure are the scheme proposed by the present invention, the retransmission scheme, and the reordering retransmission scheme. Specifically, when the erasure probability of each path information packet of Z=3 paths is fixed to [0.1, 0.2, 0.3], the erasure probability increase coefficient e0 of each path is fixed to 0. For the convenience of observation and simulation, the feedback delays D1, D2, ..., D Z All are set to D = 0 time slots to D = 30 time slots with a step size of 5 time slots, and the average end-to-end delay of sending N = 100 information packets is observed. Figure 5 The results show that when the feedback delay D of each path increases, the average end-to-end delay of the three schemes increases with the increase of the feedback delay D. Among them, the end-to-end delay of the reordering and retransmission scheme is significantly better than the retransmission scheme based on the reordering of packets within the scheduling window, which verifies the improvement of the end-to-end delay performance by reordering. When the feedback delay D is small (D≤10), the proposed scheme does not use the feedback information in time, but only performs scheduling planning at the beginning of each scheduling window. Therefore, the end-to-end delay performance is lower than that of the reordering and retransmission scheme, which is equivalent to the retransmission scheme. When the feedback delay is high (D>10), the proposed scheme predicts the errors within the feedback delay and obtains a more accurate estimate of the number of packet losses under the condition of using the a priori and a posteriori error correction mechanism, and its end-to-end delay performance is better than that of the reordering and retransmission scheme.

[0068] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for multipath information packet encoding, scheduling and real-time transmission under delayed feedback, characterized in that: The following steps are involved: Step 1: Before the transmission starts, the length of the scheduling window is determined according to the different transmission rates of each path in the multipath channel, that is, the number of paths is set to Z, and the time for each path to transmit a packet is T1, T2, ... T Z , then the length of the scheduling window is the least common multiple of the transmission time of each path, that is, w = lcm(T1, T2, ... T Z ); Step 2: At the beginning of transmission, the sender has N packets waiting to be transmitted, and the channel erasure probability of each path is e1, e2, … e Z , the transmission time is T1, T2, ...T Z , the total number of packets transmitted in a scheduling window is n w ,Only when a single path completes the transmission of an information packet or a coded packet can the next packet be transmitted on that path, and the transmission of each path is carried out in parallel; Step 3: When the receiving end successfully receives the information packet, it immediately uploads the information packet to the application layer and feeds back the feedback information of the information packet to the sending end. The feedback information of each path is fed back after the feedback delay D1, D2, ..., D Z Arrives at the sending end; Step 4: When the sender starts to transmit, if it is the beginning of the scheduling window, the sender first confirms the packets that the receiver has not successfully received through the received feedback information, and then confirms the packets through the feedback delay D and the erasure probability of each path e1, e2, ... e Z , estimate the total number of unsuccessfully received packets, encode these estimated unsuccessfully received packets into repair coded packets, and decide the number of sent packets, repair coded packets, and forward error correction coded packets, the total number is n w , arrange these n according to the receiving time order of each sending position in the scheduling window w The sending position of each packet is determined to eliminate the out-of-order reception problem caused by different transmission rates of multiple paths. The repair coding packet is received first, followed by the information packet, and finally the forward error correction coding packet. After completing the scheduling, the sender sends the information packet on the currently available path according to the current scheduling. Step 5: When the sender starts to transmit, if it is not the start of the scheduling window at this time, the sender first confirms the packets that the receiver has not successfully received through the received feedback information, and inserts these lost packets into the head of the current sending queue, and re-arranges the sending position of the lost packets and the remaining unsent packets and coded packets in the scheduling window according to the order of receiving time, so as to give priority to the retransmission of the lost packets. After completing the scheduling arrangement, the sender sends the packets on the currently available path according to the current scheduling arrangement; Step 6: When the receiving end successfully receives the data packet, repeat step 3; Step 7: After completing steps 1-6, repeat steps 4-6 until N information packets are transmitted.

2. A method for multipath information packet encoding, scheduling and real-time transmission under delayed feedback according to claim 1, characterized in that: The total number of packets that can be transmitted in a scheduling window in step 2 is n w is the length of the scheduling window w and the transmission time of each path T1, T2, ... T Z OK, w for:

3. The method for multipath information packet encoding, scheduling and real-time transmission under delayed feedback according to claim 2, characterized in that: In step 4, the known number of unconfirmed packets u and the erasure probability of each path e1, e2, …e are obtained through feedback information in each scheduling window. Z and feedback delays D1, D2, …, D Z The estimated number of unconfirmed packets is recorded as For the transmitter, each path has a feedback delay of D1, D2, ..., D Z The number of unconfirmed packets sent within is known, and is denoted as k1, k2, ..., k Z , from which the estimated number of unconfirmed packets is obtained, that is, for 4. The method for multipath information packet encoding, scheduling and real-time transmission under delayed feedback according to claim 3, characterized in that: Step 4: The erasure probability of each path is e1, e2, ... e Z , the length of the scheduling window w and the transmission time of each path T1, T2, ...T Z Determine the number of information packets, repair coding packets and forward error correction coding packets sent, which are: Repair code package: Information Packet: Forward error correction coding packet:

Images