CN117294332A

CN117294332A - MPDU retransmission method

Info

Publication number: CN117294332A
Application number: CN202311237496.XA
Authority: CN
Inventors: 吴限
Original assignee: Wu Qi Technologies Inc
Current assignee: Wu Qi Technologies Inc
Priority date: 2023-03-06
Filing date: 2023-03-06
Publication date: 2023-12-26
Also published as: CN116318257B; CN116318257A; CN117294333A

Abstract

The invention relates to the technical field of power line carrier communication, in particular to an MPDU retransmission method, which comprises the following steps: s100, cutting an MSDU into a plurality of MPDUs; s200, a transmitting end sequentially transmits MPDUs to a receiving end; the retry flag of the first mpdu=0, and the retry flag of the other mpdus=1; s200 includes: s201, MPDU is sent; s202, receiving a SACK signal, executing S204 if the SACK signal is 1, otherwise executing S203; s203, retransmitting the current MPDU; if the number of physical blocks in the MPDU is more than two, only retransmitting the physical blocks which fail to be received when retransmitting the MPDU; s204, the next MPDU is transmitted. The MPDU retransmission method provided by the invention can improve the data retransmission efficiency and the data retransmission timeliness, reduce the data retransmission quantity, reduce the storage space required to be reserved by a receiving end and simultaneously maintain the compatibility of a national network.

Description

MPDU retransmission method

Technical Field

The invention relates to the technical field of power line carrier communication, in particular to an MPDU retransmission method.

Background

The application of PLC in national networks and under 1901.1 protocol requires a great deal of scene test support. In practical application, the requirements of transmission efficiency are continuously improved due to changeable application scenes and environmental interference factors.

For example, in a scene of long buried lines or a situation of strong interference, a protocol is designed with various FEC codes and physical block size combinations, so that the FEC codes and the physical block size combinations can be transmitted at different rates to improve the success rate. For the above scenario, a lower rate may be selected for transmission, but for larger application layer packets, this means that fragmentation, i.e. one MSDU needs to be cut into multiple MPDUs for transmission, to improve the transmission success rate. Fragmentation can be one MPDU per physical block (short MPDU) or multiple MPDUs per physical block (long MPDU). In the transmission process, if the receiving end receives all complete fragments, the receiving end can be combined into a complete MSDU, but if the receiving end has an unsuccessfully received physical block, in the original national network protocol definition, the whole message needs to be retransmitted, and the retransmission mode is simple but the efficiency is lost. For example, on a given SNR line, an optimal rate is calculated and processed in a variable rate selection form, and the FEC physical blocks corresponding to this rate are likely to be relatively small, and for an upper layer packet, such as a 1024-byte packet, if a single physical block with a physical payload of 134 size is required to transmit, 8 physical blocks will be required to complete the transmission, and if one of the physical blocks is wrong, the entire packet, i.e. the 8 physical blocks, will need to be retransmitted in its entirety, and the data transmission performed in the above manner will waste bandwidth and reduce the transmission efficiency.

Secondly, there is another problem that for variable rate selection, a message that fails to be retransmitted multiple times will need to be sent at a reduced rate, while for a message that has been partially sent successfully, if only one physical block is not sent successfully, the rate cannot be switched halfway, and the rate must be switched until the whole message is sent completely, otherwise, all physical blocks that have been sent successfully need to be discarded.

Again, in the original national network protocol definition, when the MSDU is transmitted for the first time, the retry flag of the MSDU is set to 0, and when the MPDU included in the MSDU is not transmitted successfully, the MSDU is retransmitted, and at this time, the retry flag of the MSDU is set to 1. However, in the above transmission process, if the current MSDU is not successfully transmitted, the transmitting end starts retransmitting the current MSDU, but the transmitting end does not retransmit the current MSDU due to the default retransmission number of the reached MSDU, etc., at this time, the transmitting end starts transmitting the next MSDU, but the transmitting end totally loses the MSDU due to the flush of the transmitting end and poor communication, etc., and the transmitting end starts retransmitting the MSDU with retry flag=1. At this time, for the receiving end, since it does not successfully receive the second MSDU transmitted by the transmitting end, when it receives the MPDU with retry flag=1, it still considers that retransmission of the last MSDU is performed, so that the data of the two MSDUs are integrated together, resulting in MSDU CRC errors, and finally, the received data are all discarded.

Finally, for the case that the transmission is still unsuccessful for many times at a very low basic rate, the current method considers the switching route, if the switching route is not solved, the relay needs to be manually added, and for the case that only a few nodes or a single node have poor temporary communication, the cost for doing so is relatively high.

Disclosure of Invention

The invention provides an MPDU retransmission method, which can improve the data retransmission efficiency and the data retransmission timeliness, reduce the data retransmission quantity, reduce the storage space required to be reserved by a receiving end, and simultaneously maintain the compatibility of a national network, thereby reducing the rate and improving the cost.

In order to achieve the above purpose, the present application provides the following technical solutions:

a MPDU retransmission method, comprising: s100, cutting an MSDU into a plurality of MPDUs; s200, the transmitting end sequentially transmits MPDUs to the receiving end, where retry flag=0 of the first MPDU and retry flag=1 of other MPDUs;

s200 includes:

s201, MPDU is sent;

s202, receiving a SACK signal, executing S204 if the SACK signal is 1, otherwise executing S203;

s203, retransmitting the current MPDU; if the number of physical blocks in the MPDU is more than two, only retransmitting the physical blocks which fail to be received when retransmitting the MPDU;

s204, the next MPDU is transmitted.

Further, the method further comprises the following steps: and S300, receiving the MPDU by the receiving end, and storing the received MPDU according to the retry flag of the MPDU.

Further, S300 includes:

s301, receiving MPDUs;

s302, if retry flag=0 of the MPDU, the MPDU corresponds to a new MSDU, and the previous receiving buffer is cleared and the received MPDU is stored; if retransmission flag=1 of the MPDU, the MPDU belongs to the current MSDU and stores the received MPDU.

Further, S200 includes: if the switching speed is needed, selecting the speed of which the physical block size corresponding to the speed is the same as the size of the successfully transmitted physical block to switch, and replacing the TMI with the TMI of the switched speed.

Further, the MPDU further includes a CRC;

s301, receiving MPDUs and feeding back SACK signals; and analyzing whether the MPDU is correctly received according to the CRC, and if so, setting the feedback SACK signal to be 1.

Further, if the number of physical blocks in the MPDU is two or more, only the physical blocks that failed to be received are retransmitted when the MPDU is retransmitted, including:

the receiving end feeds back SACK signals according to the receiving conditions of the physical blocks;

and the sending end integrates the physical block which is failed to be received by the receiving end into a new MPDU according to the SACK signal, and sets the retry flag of the MPDU to be 1 for retransmission.

The principle and the advantages of the invention are as follows:

1. the scheme overcomes the fixed definition of the retry flag in the national network protocol, and skillfully utilizes the retry flag instead, so that the improved scheme can realize compatibility under the original national network protocol, and the cost for improving the transmission efficiency is greatly reduced. In this scheme, only the retry flag of the first mpdu=0, and the retry flag of the other MPDUs is set to 1, and whether to retransmit or not does not wait for the whole MSDU to be sent is determined after the whole MSDU is sent, but is determined by the SACK signal sent by the transmitting end. Thus, when receiving each retransmission flag=1 packet, the receiving end considers that it receives a retransmission data, generates a SACK signal, feeds back to the transmitting end whether it successfully receives the content transmitted by the transmitting end, and does not empty the buffer until the MPDU of the next retransmission flag=0 is transmitted. That is, for the transmission of one MSDU, after each fragment MPDU is sent, the receiving feedback is timely performed, so that when the MPDU is received in failure or not, the current MPDU can be retransmitted in the first time, thereby not only improving the timeliness of data retransmission, but also reducing the data retransmission amount, improving the data retransmission efficiency, and particularly for some nodes with poor edge communication, the communication can be performed at a lower speed, and the generated overhead is small.

2. The receiving end can save the storage space which needs to be reserved, especially for the multi-link proxy nodes. In the scheme, the maximum MSDU length of the current link is not required to be reserved each time to keep the reception of the whole MSDU, but one MPDU can be received, and finally the physical blocks in each MPDU are spliced. In the technical scheme of the application, the MPDU can comprise a plurality of physical blocks (long MPDUs) or only comprises one physical block (short MPDU), and under the condition of poor network communication quality, the application preferably adopts the short MPDU to communicate so as to ensure the communication quality.

3. In the existing national network protocol, for variable rate selection, for a message which fails to be retransmitted for a plurality of times, the rate is reduced, and for a message which is already partially transmitted successfully, the rate cannot be switched in the middle, the rate can be switched only after the whole message transmission is finished, otherwise, all physical blocks which are originally transmitted successfully need to be discarded. By adopting the scheme, when the rate is required to be switched, only the physical blocks corresponding to the rates before and after switching are controlled to be the same, seamless connection can be performed by directly replacing the index (TMI) of the rate table, and retransmission of the whole message is required only when the rates with the same physical block size are not needed.

Drawings

Fig. 1 is a flowchart of an MPDU retransmission method according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of MPDU generation in an MPDU retransmission method according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of MPDU integration in an MPDU retransmission method according to an embodiment of the present invention.

Fig. 4 is a flow chart of a transmitting end in an MPDU retransmission method according to an embodiment of the present invention.

Fig. 5 is a block flow diagram of a receiving end in an MPDU retransmission method according to an embodiment of the present invention.

Detailed Description

The following is a further detailed description of the embodiments:

example 1:

as shown in fig. 1, the MPDU retransmission method includes the following steps (in this application, the reference numerals of the steps are merely used as distinction of the steps and are not used to limit the order of the steps):

s100, as shown in fig. 2, the MSDU is cut into several MPDUs, and for the sake of understanding of the principle, the example shown in the figure cuts the MSDU into two MPDUs, and in this embodiment, cuts the MSDU into 4 MPDUs (pbnum=4).

The MPDU includes a CRC and a physical block header, and in this embodiment, the MPDU includes a physical block.

S200, the transmitting end sequentially transmits MPDUs to the receiving end according to SACK signals; the retry flag of the first mpdu=0 and the retry flag of the other mpdus=1. And S300, receiving the MPDU by the receiving end, and storing the received MPDU according to the retry flag of the MPDU.

Specific:

s201, as shown in fig. 4, the transmitting end transmits MPDUs; in this embodiment, MPDUs are transmitted from a retransmission flag bit of 0 (pb_sn=0), and a total of 4 MPDUs are 0/1/2/3, where the retransmission flag of the first short MPDU is 0, and the retransmission flag=1 must be successfully received by the first short MPDU of pb_sn=0, otherwise, the retransmission flag is always 0 (in this sense, the retransmission flag indicates that 0 is a new MSDU, which is considered in terms of compatibility, because it can be interconnected with the existing protocol, and efficiency is improved).

S301, as shown in fig. 5, the receiving end receives the MPDU and feeds back a SACK signal; and analyzing whether the MPDU is correctly received according to the CRC, and if so, the fed-back SACK signal is 1. Whenever a retry flag=0 packet is received, this means that a new MSDU is received and any MPDUs received in the past need to be refreshed.

S202, the transmitting end receives the SACK signal, if the SACK signal is 1, S204 is executed, otherwise S203 is executed. S203, retransmitting the current MPDU; s204, the next MPDU is transmitted.

If the SACK signal received after the transmitting end transmits the current MPDU is 0 or the SACK signal is not received within the preset time, the MPDU needs to be continuously transmitted, and pb_sn is not increased; if the received SACK signal is 1, which indicates that the MPDU is successfully received, and then the retry flag=1, the next MPDU is continuously transmitted, and pb_sn+1 is transmitted until the last transmission is completed.

For a packet with retry flag=0, typically pb_sn must be 0 to represent the first block, and how many MPDUs (frame sequence number+1 of end of frame flag, since frame sequence number starts with 0) the MSDU has total are available from the physical block header, the size (pbsz) of each MPDU can be obtained from the TMI of this block, thus calculating the data size of the MSDU, and then allocating the corresponding buffer space for the MSDU.

For pb_sn-! A packet of =0, then the retry flag should be all 1, which indicates that the received MPDU is the current MSDU, and if the CRC of the MPDU is correct, a reply sack=1 indicates correct reception; if the number of physical blocks (pbnum) reaches the number that should be received, then an attempt can be made to calculate the CRC of the MSDU, which can be reported to the upper layer if it is correct, otherwise it will continue to wait for the next PB.

In this process, the receiving end will not actively refresh the current MSDU, and receive it passively, and the sending state machine is controlled by the sending end, if the sending end times out or refreshes, it will jump to S301 to send a new MSDU.

As shown in fig. 3, after the receiving end receives all MPDUs of the current MSDU, the receiving end integrates all MPDUs to form the MSDU.

Example 2:

the basic principle of embodiment 2 is the same as that of embodiment 1, and the difference is that in embodiment 2, the number of physical blocks in the MPDU is more than two, and correspondingly, the SACK reply message of the receiving end adopts a bitmap form, so that the transmitting end can learn the failure condition of the receiving end through the bitmap, and only retransmits the physical blocks with failed reception when retransmitting the MPDU.

The weight transmission mode is as follows:

in this embodiment, it is assumed that the current MSDU is cut into 5 MPDUs, each MPDU containing 4 physical blocks.

If the first MPDU sent by the transmitting end has been successfully received, and the first and second physical blocks in the second MPDU sent by the transmitting end have not been successfully received, the SACK reverts to 0011. At this time, the transmitting end integrates the first and second physical blocks into a new MPDU according to the SACK signal, and sets its retransmission flag to 1 for retransmission. And when the subsequent MPDU packet is not successfully received, retransmitting in the mode, wherein the retry flag in the subsequent retransmission is 1, namely, in the data retransmission of one MSDU, the retry flag=0 except the first MPDU transmitted in the retransmission is 1, and the subsequent retransmission retry flag is 1. In other embodiments of the present application, short MPDUs may also be used to retransmit physical blocks that need to be retransmitted in sequence.

Example 3:

the basic principle of embodiment 3 is the same as that of embodiment 1, except that in embodiment 3, S200 includes: if the switching speed is needed, selecting the speed of which the physical block size corresponding to the speed is the same as the size of the successfully transmitted physical block to switch, and replacing the TMI with the TMI of the switched speed.

According to the national network protocol, the sizes of physical blocks are typically 72, 136, 264, 520, etc., and there are cases where different rates correspond to the same physical block size. In this embodiment, when the rate switching is needed (e.g., retransmission of a message with multiple failures will be needed to perform rate reduction transmission), the transmitting end selects a rate corresponding to the rate and the size of the physical block with the same size as that of the successfully transmitted physical block to perform switching, i.e., the size of the physical block corresponding to the rate before and after the attempt to control switching is the same, so that seamless connection of the successfully transmitted physical block can be performed by directly replacing a rate table index (TMI), without retransmitting the entire message again.

The foregoing is merely exemplary of the present invention, and the specific structures and features well known in the art are not described in any way herein, so that those skilled in the art will be able to ascertain all prior art in the field, and will not be able to ascertain any prior art to which this invention pertains, without the general knowledge of the skilled person in the field, before the application date or the priority date, to practice the present invention, with the ability of these skilled persons to perfect and practice this invention, with the help of the teachings of this application, with some typical known structures or methods not being the obstacle to the practice of this application by those skilled in the art. It should be noted that modifications and improvements can be made by those skilled in the art without departing from the structure of the present invention, and these should also be considered as the scope of the present invention, which does not affect the effect of the implementation of the present invention and the utility of the patent. The protection scope of the present application shall be subject to the content of the claims, and the description of the specific embodiments and the like in the specification can be used for explaining the content of the claims.

Claims

1. A MPDU retransmission method, comprising: s100, cutting an MSDU into a plurality of MPDUs; s200, a transmitting end sequentially transmits MPDUs to a receiving end, and is characterized in that: the retry flag of the first mpdu=0, and the retry flag of the other mpdus=1;

s200 includes:

s201, MPDU is sent;

s204, the next MPDU is transmitted.

2. The MPDU retransmission method according to claim 1, wherein: further comprises: and S300, receiving the MPDU by the receiving end, and storing the received MPDU according to the retry flag of the MPDU.

3. The MPDU retransmission method according to claim 2, wherein: s300 includes:

s301, receiving MPDUs;

4. The MPDU retransmission method according to claim 1, wherein: s200 includes: if the switching speed is needed, selecting the speed of which the physical block size corresponding to the speed is the same as the size of the successfully transmitted physical block to switch, and replacing the TMI with the TMI of the switched speed.

5. The MPDU retransmission method according to claim 3, wherein: the MPDU further includes a CRC;

6. The MPDU retransmission method according to claim 1, wherein: if the number of physical blocks in the MPDU is two or more, only the physical blocks that failed to be received are retransmitted when the MPDU is retransmitted, including: