CN1152511C - Method for retransmitting information by changing intersection length through merging data package - Google Patents

Abstract

The invention discloses an information retransmission method that uses Turbo codes as forward error correction codes for H-ARQ transmission and reception, and changes the interleaving length by combining data packets. When the number of retransmissions of a data packet exceeds the maximum number of retransmissions, the data packet and its subsequent data packets can be combined before or after the CRC check code. The combined data contains one or two independent CRCs The check code is then encoded and sent. The receiving end decodes the combined data packets. By merging data packets, increasing the interleaving length improves Turbo decoding performance, thereby increasing the probability of correct reception of the H-ARQ system and reducing the average number of retransmissions of data packets.

Description

Information retransmission method changing interleaving length by merging data packets

The present invention relates to the technical field of data transmission, and more particularly relates to a method for error correction by feedback and retransmission of data information in the technical field of high-speed data transmission.

In the technical field of high-speed data transmission, a hybrid automatic repeat request (H-ARQ) technology using a turbo code as a forward error correction code is generally adopted. This technology is used in both High Speed Downlink Packet Access (HSDPA) and 1xEV-DV. In the existing H-ARQ technology, if a data packet is decoded incorrectly, there is no other way except to resend the redundant information of the data packet. For ARQ systems that use Turbo codes or serial concatenated codes, whose performance is very sensitive to the interleaving length, as forward error correction codes, the prior art cannot make full use of the interleaving depth to improve the performance of Turbo codes, which is limited to some extent. the efficiency of the system. In the existing solution, the two data packets of the same user are not related in the decoding process from sending to receiving. If a packet is received incorrectly, there is no other way to do it except to retransmit it.

The purpose of the present invention is to solve the problems in the above-mentioned prior art that the performance of the Turbo code cannot be fully utilized to improve the interleaving depth, which limits the efficiency of the system to a certain extent. The transmission method makes full use of the error correction performance of Turbo codes, and implements a certain retransmission strategy in conjunction with the Turob code decoding performance that is sensitive to the interleaving length, so as to improve the overall performance of the H-ARQ system.

The technical scheme of the present invention is realized by the following method: the present invention provides a kind of information retransmission method that changes the interleaving length of Turbo code by merging data packets, and the method comprises the steps: using Turbo code as forward error correction code During the retransmission process, if the receiving end makes a decoding error, the sending end is required to resend the redundant information of the data packet, which is characterized in that:

After the number of data packet retransmissions reaches a preset value T _i , if the decoding is still incorrect, the receiving end sends specific feedback information, requiring the sending end to perform data packet merging while retaining the received data for future merging;

After the sender receives the feedback signal requiring data packet merging, it merges the data packet that was not received correctly with at least one subsequent data packet;

After the receiving end decodes the combined data packet, it performs a cyclic redundancy code (CRC) check;

When the sender punches the merged data packets, it implements the method of non-uniform punching, and punches more redundant information of sub-packets that have been retransmitted, while punching less redundant information of subsequent data packets;

After the receiving end receives the information of the merged data packet, it merges with the saved redundant information, and the merged data is sent to the decoder for decoding.

The method also includes the following technical features:

There are two ways of merging the above data packets: merging before adding the CRC check code and merging after adding the CRC check code; if merging before adding the CRC check code, the combined data is encoded and sent as a whole, There is only one set of CRC check codes in the data packets. If they are combined after adding the CRC check codes, the combined data will still be encoded and sent as a whole. The combined data packets will have at least two sets of CRC check codes, corresponding to for each subpacket;

After the receiving end decodes the merged data packet, it performs a CRC check. If the data packet contains only one set of CRC check codes, the entire data packet is checked as a whole, and a feedback signal is sent according to the check result. Two sets of CRC check codes are checked with their respective CRCs, and feedback signals are sent according to their respective check results;

The above data packet merging process can be extended to multiple data packet merging. If two data packets cannot be received correctly through retransmission after merging, the merged data packet can still continue to be merged with subsequent data packets; multiple data packets are merged There are also two methods, merging before adding the CRC check code and merging after adding the CRC check code; if merging before adding the CRC check code, the combined data packet has only one set of CRC Combined after code verification, the combined data contains multiple sets of CRC check digits, each set of check codes corresponds to a sub-packet; after the receiving end decodes the combined data package, it passes the CRC check; if the combined data package only Contains a set of CRC check codes, the entire data packet is checked as a whole, and a feedback signal is sent according to the check result; if the combined data contains multiple sets of CRC check codes, each sub-packet uses its own CRC Carry out verification, and send feedback signals respectively according to their respective verification results; a maximum value can be set up for the above-mentioned multiple data packets, and the number of sub-data packets participating in the combination exceeds the maximum value, and the merging process will not continue.

The advantage of the present invention is that it can make full use of the characteristic that Turbo codes are sensitive to the depth of interleaving (the longer the interleaving length, the better the error correction performance of Turbo codes). Merge and increase the interleaving length to improve the performance of Turbo decoding, thereby increasing the probability of correct reception of the H-ARQ system. At the same time, because the error correction performance of the Turbo code is improved by increasing the interleaving length, the average number of retransmissions of the data packet can be reduced.

The method of the present invention will be further described below in conjunction with the accompanying drawings.

Fig. 1 is the schematic diagram that user data packet is transmitted by H-ARQ system in the method of the present invention;

Fig. 2 is a schematic diagram of sending end user data packet encoding;

Fig. 3 is the synoptic diagram of sending end coding under CRC combination mode (2 data packets are combined);

Fig. 4 is the schematic diagram of (2 data packets are merged) receiving end coding under CRC combination mode;

Fig. 5 is a schematic diagram of sending end coding under CRC non-combining mode (combining of 2 data packets);

Fig. 6 is a schematic diagram of receiving end coding under CRC non-combining mode (2 data packets are combined);

Fig. 7 is a schematic diagram of sending end coding under CRC combination mode (multiple data packets are combined);

Fig. 8 is a schematic diagram of receiving end encoding (combination of multiple data packets) under the CRC combination mode;

Fig. 9 is a schematic diagram of sending end coding under CRC non-combining mode (multiple data packets are combined);

FIG. 10 is a schematic diagram of encoding at the receiving end in a CRC non-combining mode (multiple data packets are combined).

The basic method for implementing the technical solution of the present invention is to provide a retransmission method that uses Turbo codes as forward error correction codes for H-ARQ transmission and reception and changes the interleaving length through combination. In the process of implementing ARQ, if the number of retransmissions of a certain data packet exceeds the maximum number of retransmissions, it means that only retransmission can not meet the requirements of transmission quality at this time. For ARQ systems using Turbo codes as FEC codes, there is another approach. Because the error correction performance of the Turbo code is sensitive to the interleaving length (the longer the interleaving length, the better the error correction performance of the Turbo code), so the data packet can be combined with its subsequent data packets, and the combined data packets can be encoded and sent . There are two ways of merging: merging before adding CRC check code and merging after adding CRC check code. According to different combining methods, the combined data contains one or two independent CRC check codes. The receiving end decodes the combined data packets, performs CRC check and sends feedback information according to the combination method.

FIG. 1 is a schematic diagram of user data packets being transmitted through an H-ARQ system in the method of the present invention. User data is decomposed into data packets P1, P2,..., Pi..., and transmitted through the H-ARQ system. The Turbo code used in the present invention is used as a forward error correction code. In the process of implementing ARQ, if the number of retransmissions of a data packet P _i exceeds a certain value T _i (preset), the receiving end retains the received redundant information data about P _i , and sends a request for data packet merging Feedback signal.

Fig. 2 is a schematic diagram of encoding of user data packets at the sending end. After receiving the feedback signal requiring data packet combination, the sending end combines the data packet P _i and its subsequent data packet P _i+1 . There are two ways of merging: merging before adding the CRC check digit and merging after adding the CRC check digit. If it is merged before adding the CRC check code, as shown in Figure 3, the combined data packet has only one set of CRC check code, which is used to check the combined data packet as a whole. The decoding quality (whether the decoding is correct) of the combined data packets is judged as a whole, as shown in FIG. 4 . This means that the two data packets P _i and P _i+1 are combined and treated as one data packet. If the merging is performed after adding the CRC check digit, as shown in Figure 5, the combined data packet contains two sets of CRC check codes CRC _i and CRC _i+1 , corresponding to the data packets P _i and P _i+1 respectively . In this way, after decoding at the receiving end, the decoding quality of the two data packets can be judged by two sets of CRC check codes, and respective feedback signals are sent, as shown in FIG. 6 .

It is worth noting that when the data packet P _i is retransmitted beyond T _i and the receiving end sends a signal to combine data packets, the information of the received data packet P _i is not discarded, and it needs to be retained to continue and combine The new data packets are merged. The reason for this is that for the data packet P _i , no matter before or after the combination, the codeword encoded by the Turbo code at least contains the original information sequence M _i (that is, the information bit of the Turbo code) , in addition, the check bits output by the first component encoder of the Turbo code are also the same and can be combined.

Because the receiving end still has redundant information of the data packet P _i , and this information is combined after multiple retransmissions, so its utilization will greatly improve the receiving quality of the sub-packet P _i . Relatively speaking, the reception quality of the subpacket P _i+1 in the merged packet is poor. Based on this, some adjustments need to be made on the sending end. In the puncturing process behind the turbo code encoder, a non-uniform puncturing method is used to delete more redundant information of P _i and less redundant information of P _i+1 . An optional solution is that since the receiving end has already stored the information sequence M _i of P _i , it is unnecessary to send this part of information.

Since there are two ways of merging, there are two kinds of feedback information sent by the receiving end after decoding the combined data packet: sending only one feedback information (as shown in Figure 4) and sending two independent feedback information (as shown in Figure 6 shown). The form of sending only one feedback message is relatively simple. The sender only needs to decide whether to retransmit according to the feedback signal. At this time, the combined data packets are completely regarded as a whole. That is to say, as long as one of the sub-packets P _i and P _i+1 has a decoding error, both sub-packets must be retransmitted. In the form of sending two independent feedback messages, the protocol and control are more complicated. After receiving the two feedback signals, the sending end judges whether the two sub-packets have been decoded correctly. At this time, flexible processing can be performed according to the decoding situation. If both subpackets are decoded incorrectly, the retransmission information can be sent as a whole, which is no different from the first form. If only one of the sub-packets is decoded incorrectly, when retransmitting, less or no redundant information about the sub-packet can be transmitted. The two forms of combining and feedback have their own advantages and disadvantages. The first form is relatively simple to control, but the disadvantage is that the transmission efficiency is relatively low. The second form of protocol and control is more complicated, and the feedback signaling needs to occupy more bandwidth, but the transmission efficiency is higher.

The above merging method can be extended to the situation of multiple data packets. The process and way of merging multiple packets is similar to merging two packets. If the combination of the two data packets still cannot be received correctly, the combined data packet can continue to be combined with subsequent data packets. There are two ways of merging: merging before adding CRC check digits and merging after adding CRC check digits. If the combination is performed before the CRC check code is added, as shown in FIG. 7 , the combined data packet has only one set of CRC check codes. After decoding, the receiving end performs an overall CRC check on the combined data packet, and sends a feedback signal according to the check result, as shown in FIG. 8 . If the merging is carried out after adding the CRC check code, as shown in Figure 9, the combined data contains multiple groups (k groups in Figure 9) CRC check codes, corresponding to each subpacket P _i to P _i respectively _+k . After decoding at the receiving end, the decoding quality of k data packets is judged respectively through k sets of CRC check codes, and respective feedback signals are sent, as shown in FIG. 10 .

Theoretically, if the combined data packets cannot be received correctly after retransmission, the combining process can continue forever. Considering the specific implementation and the system's requirement for time delay, a maximum value MH is set in this system (MH can be preset or dynamically adjusted). If the number of subpackets participating in merging exceeds the MH, the merging process will not continue.

According to the description of the above embodiments, although the present invention discloses an information retransmission method that uses Turbo codes as forward error correction codes for H-ARQ transmission and reception and changes the interleaving length by combining data packets, ordinary people in the art The skilled person can modify or deform the basic steps of the method of the present invention and apply it to a similar data transmission method, and its essential content should also belong to the protection scope of the method defined in the claims of the present invention.

Claims (5)

1. A method for retransmitting information by merging data packets to change the interleaving length of the Turbo code, the method comprising steps: in the retransmission process using the Turbo code as a forward error correction code, if the receiving end decodes an error, the sending end is required to Resend the redundant information of this data packet, it is characterized in that: After the number of data packet retransmissions reaches a preset value T _i , if the decoding is still incorrect, the receiving end sends specific feedback information, requiring the sending end to combine data packets, and at the same time retain the received data for future merging ; After the sender receives the feedback signal requiring data packet merging, it merges the data packet that was not received correctly with at least one subsequent data packet; After the receiving end decodes the combined data packet, it performs CRC check; When the sender punches the merged data packets, it implements the method of non-uniform punching, and punches more redundant information of sub-packets that have been retransmitted, while punching less redundant information of subsequent data packets; After the receiving end receives the information of the merged data packet, it merges with the saved redundant information, and the merged data is sent to the decoder for decoding. 2. The information retransmission method according to claim 1, characterized in that: said data packets are combined in two ways: combining before adding CRC check code and merging after adding CRC check code, if adding CRC Merge before the check code, the combined data is encoded and sent as a whole, the combined data packet has only one set of CRC check code, if it is combined after adding the CRC check code, the combined data is still processed as a whole Coding and sending, the combined data packet has at least two sets of CRC check codes, corresponding to each sub-packet; 3. The information retransmission method according to claim 2, characterized in that: after the receiving end decodes the combined data packet, the step of performing CRC check further comprises: if the data packet contains only one set of CRC Code verification, the entire data packet is verified as a whole, and a feedback signal is sent according to the verification result; if there are two sets of CRC verification codes, the respective CRCs are used for verification and sent separately according to the respective verification results Feedback signal. 4. The information retransmission method according to claim 1, characterized in that: the process of combining data packets can be extended to combine multiple data packets, if two data packets cannot be received correctly through retransmission after combining, then The merged data packet can still continue to be merged with subsequent data packets; there are also two methods for merging multiple data packets, merging before adding the CRC check code and merging after adding the CRC check code; If merged before adding the CRC check code, the merged data packet has only one set of CRC check codes; if combined after adding the CRC check code, the combined data contains multiple sets of CRC check digits. The code corresponds to a subpacket; After the receiving end decodes the merged data packet, it passes the CRC check; if the merged data packet contains only one set of CRC check codes, the entire data packet is checked as a whole, and a feedback signal is sent according to the check result; if The merged data contains multiple groups of CRC check codes, each sub-packet is checked with its own CRC, and feedback signals are sent respectively according to their respective check results. 5. The information retransmission method according to claim 4, characterized in that: a maximum value (MH) can be set up for the plurality of data packets, and the number of sub-packets participating in merging exceeds the maximum value, and the merging process is no longer continue.

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