An uplink sliding window HARQ method based on Raptor code

Abstract

The present invention discloses an uplink sliding window HARQ method based on Raptor code. In the 5G system, when there is no uplink space division multiplexing, one HARQ process schedules one transmission block, and each DCI feeds back the retransmission information of one transmission block, which has the disadvantages of low throughput and high number of signaling interactions. Based on the traditional HARQ method, the present invention proposes a sliding window HARQ method to configure multiple windows for one HARQ process to schedule transmission blocks. And a new DCI format is added, which can use one DCI to configure the retransmission information of transmission blocks in multiple windows. The present invention combines the Raptor code with the sliding window HARQ at the same time, and uses partial windows to transmit redundant transmission blocks. The receiving end only needs to correctly decode the transmission blocks of a certain number of windows to recover the transmission blocks of all windows. In this way, the throughput is improved, the number of signaling interactions is reduced, and the block error rate is also reduced.

Description

Technical Field

[0001] The present invention relates to an uplink sliding window HARQ (Hybrid Automatic Repeat Request) method based on Raptor code (fast cyclone code), which can be used in a 5G wireless communication system. Background Art

[0002] As a key technology of 5G, HARQ has received a lot of attention in recent years. In wireless communications, data transmission is often affected by the channel. Poor channel quality will lead to data packet loss and errors, affecting the reliability and efficiency of data transmission. HARQ uses an adaptive retransmission mechanism to retransmit packets when they are lost or erroneous, which can significantly improve the reliability and efficiency of data transmission.

[0003] During the 5G uplink PUSCH (physical uplink shared channel) transmission process, the gNB (next generation base station) side supports up to 16 HARQ processes. When there is no uplink spatial division multiplexing, one HARQ process only supports scheduling one transport block, and only the retransmission information of this transport block can be fed back through DCI (downlink control information). When a certain number of data packets need to be transmitted, the mechanism of scheduling one transport block at a time causes the gNB to frequently schedule PUSCH through DCI, which increases the network overhead and affects the network performance and throughput. In addition, in some scenarios with poor channel quality, the transport block is difficult to be received correctly, resulting in an increase in the block error rate, and the limitation on the number of retransmissions may further cause the transport block to be unable to be transmitted correctly. Therefore, the present invention improves on the basis of the 5G HARQ mechanism, and proposes an uplink sliding window HARQ method based on Raptor code. The method of scheduling multiple transport blocks through one HARQ process reduces the overhead of signaling interaction and improves the throughput, and further introduces Raptor coding to reduce the block error rate under low signal-to-noise ratio. The present invention is applicable to 5G wireless communication systems. Summary of the invention

[0004] Technical problem: The main technical problem to be solved by the present invention is to avoid the shortcomings of the above-mentioned background technology and provide an uplink sliding window HARQ method based on Raptor code.

[0005] Technical solution: Based on the 5G HARQ mechanism, the present invention proposes an uplink sliding window HARQ method based on Raptor code suitable for a 5G wireless communication system. The method comprises the following steps:

[0006] Step 1: After receiving the UE scheduling request, the gNB allocates a HARQ process to it, configures its window length N, NDI (new data indication) of all windows, and RV (redundancy version). The corresponding DCI is configured according to the parameters of the HARQ process and sent to the UE (user end) through the PDCCH (physical downlink control channel).

[0007] Step 2: The UE obtains the DCI by decoding the PDCCH, and further obtains the PUSCH time-frequency resources allocated to it, the HARQ process number, the window length N, the number of Raptor coding source symbols K, the NDI of each Raptor coding source window, and the RV.

[0008] Step 3: UE configures the new or specified redundant version of the transport block data according to the NDI and RV of the previous K windows. [0:K-1] Then these K transmission blocks are encoded as K source symbols of Raptor coding to generate N coded symbols e [0:N-1] , the last NK redundant coding symbols c [K:N-1] As the transmission block data of the remaining window.

[0009] Step 4: The UE performs LDPC (low-density parity check) encoding on the transport block data of each window, and then sends it to the gNB via the PUSCH configured on the specified time-frequency resources.

[0010] Step 5: After receiving the PUSCH corresponding to each window, the gNB first performs LDPC decoding on its transport block, counts the number of correctly decoded transport blocks N', and obtains the received coded symbol e' [0:N'-1] , and record its window index in ESIs (encoding symbol identifier). ESIs is the encoding symbol identifier of the Raptor code, indicating the index of the encoding symbol corresponding to the correctly decoded data block.

[0011] Step 6: When N'≥K, further Raptor decoding is performed, using the deactivation decoding algorithm to recover all source symbols t [0:K-1] , and then get the transmission blocks sent by the first K windows. When N'<K, Raptor decoding cannot be performed. At this time, when a source transmission block is decoded successfully, the NDI of the redundant window is inverted and the RV is set to 0 to indicate the transmission of a new redundant transmission block. Otherwise, the NDI and RV are configured according to the decoding status of each window.

[0012] Step 7: The gNB configures the corresponding DCI according to the parameters of the HARQ process and sends it to the UE through PDCCH.

[0013] Beneficial effect: The advantage of the present invention is that, based on the 5G HARQ mechanism, an uplink sliding window HARQ method based on Raptor code suitable for 5G wireless communication systems is proposed. By configuring multiple windows to schedule transmission blocks for a HARQ process and adding a new DCI format, multiple transmission blocks are scheduled at one time and retransmission information of multiple windows is configured. At the same time, Raptor coding is introduced in the transmission block data processing, so that when the gNB correctly receives a certain number of window transmission block data, all the source transmission blocks can be restored through Raptor decoding. In this way, the throughput can be improved, the number of signaling interactions can be reduced, and the block error rate can also be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a UE side design flow chart of the present invention.

[0015] Figure 2 This is the gNB side design flow chart of the present invention.

[0016] Figure 3 It is an example of the sliding window HARQ mechanism of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings:

[0018] Figure 1 The flowchart of the UE side design of the present invention is as follows: an uplink sliding window HARQ method based on Raptor code of the present invention comprises the following steps on the UE side:

[0019] Step 1: The UE obtains the DCI by decoding the PDCCH, and further obtains the PUSCH time-frequency resources allocated to it, the HARQ process number, the window length N, the number of Raptor coded source symbols K, the NDI of each window, and the RV.

[0020] Step 2: UE configures the new or specified redundant version of the transport block data according to the NDI and RV of the previous K windows. [0:K-1] Then, these K transport blocks are encoded as K source symbols of Raptor coding. First, at t [0:K-1] Add (S+H) all-zero symbols in front of , and get the encoded input symbol vector d [0:L-1] . Where L=S+H+K.

[0021] d [0:L-1] =[z T [0:S+H+1] t T [0:K-1] ] T

[0022] D[0:L-1] Multiplying the inverse matrix of the precoder encoding matrix A to obtain the intermediate symbol vector c [0:L-1] ,

[0023] c [0:L-1] =A -1 [L×L] ·d [0:L-1]

[0024] The encoding matrix A is as follows

[0025]

[0026] Then the LT encoding matrix G LT With the intermediate symbol vector c [0:L-1] Multiply and get the coded data symbol e [0:N-1]

[0027] e [0:N-1] =G LT[1:N] ·c [0:L-1]

[0028] The last NK redundant coding symbols c [K:N-1] As the transmission block data of the remaining window.

[0029] Step 3: The UE performs LDPC encoding on the transport block data of each window, and then sends it to the gNB via the PUSCH configured on the specified time-frequency resources.

[0030] Figure 2 The flowchart of the gNB side design of the present invention is as follows: an uplink sliding window HARQ method based on Raptor code of the present invention comprises the following steps on the gNB side:

[0031] Step 1: After receiving the PUSCH corresponding to each window, the gNB first performs LDPC decoding on its transport block, counts the number of correctly decoded transport blocks N', and obtains the received coded symbol e' [0:N'-1] , and record its window index in ESIs. ESIs is the coding symbol identifier of the Raptor code, indicating the index of the coding symbol corresponding to the correctly decoded data block.

[0032] Step 2: When N' ≥ K, further Raptor decoding is performed. First, in e' [0:N'-1] Add (S+H) all-zero symbols in front of , and get the decoded input symbol vector d' [0:L-1] .

[0033] d' [0:L-1] =[z T [0:S+H+1] e' T [0:K-1] ] T

[0034] The precoder decoder matrix A' and the LT encoding matrix G are determined by the parameters ESIs, K and N' LT . Substitute the inverse matrix of A' with d' [0:L-1] Multiply to get the intermediate symbol vector c' [0:L-1] .

[0035] c' [0:L-1] =A' -1 [L×L] ·d' [0:L-1]

[0036] Then the LT encoding matrix G LT With c' [0:L-1] Multiply to get the source symbol t.

[0037] t [0:K-1] =G LT[1:K] ·c' [0:L-1]

[0038] Then the transmitted transport blocks of the first K windows are obtained. When N'<K, Raptor decoding cannot be performed. At this time, when a source transport block is decoded successfully, the NDI of the redundant window is inverted and the RV is set to 0 to indicate the transmission of a new redundant transport block. Otherwise, the NDI and RV are configured according to the decoding status of each window.

[0039] Step 3: The gNB configures the corresponding DCI according to the parameters of the HARQ process and sends it to the UE through the PDCCH.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An uplink sliding window HARQ method based on Raptor code, characterized in that: The steps include: On the gNB side, one uplink HARQ process schedules the transmission of transport blocks of multiple windows and feeds back retransmission information of all window data through one DCI. The UE decodes the DCI to obtain the scheduling information of multiple windows in a HARQ process, and performs PUSCH transmission at the corresponding time-frequency resources; The UE first performs Raptor encoding on the transport block, uses part of the window to transmit the Raptor code source transport block, and uses the remaining window to transmit the Raptor code redundant transport block; The UE side performs LDPC encoding on the transport blocks of all windows; LDPC decoding and Raptor decoding are performed on the gNB side. A certain number of transport blocks in a window are successfully decoded through LDPC decoding, and all source transport block data can be further recovered through Raptor decoding.

2. The uplink sliding window HARQ method based on Raptor code according to claim 1, characterized in that: Multiple windows are configured in a HARQ process. When the transmission block in the window fails to pass LDPC decoding and Raptor decoding, the data in this window needs to be retransmitted, and the RV(i) in the DCI is used to indicate the retransmitted redundant version of the transmission block in this window on the UE side. When the transmission block in the window is decoded successfully, this window can be used to transmit new data, and the NDI(i) in the DCI is inverted and the RV(i) is set to 0 to indicate to the UE side that this window is new data transmission; i is the index of the window.

3. The uplink sliding window HARQ method based on Raptor code according to claim 2, characterized in that: Some new parameters are added to DCI to feedback the retransmission information of all windows: the 2-bit parameter Window length indicates the window length scheduled by a HARQ process, and 00, 01, 10, and 11 represent lengths of 1, 2, 4, and 8 respectively; the N-bits parameter New data indicator indicates whether each window is new data transmission; the 2*N-bits parameter Redundancy version indicates the redundant version of each window transmission block; the 2-bit parameter Symbol length indicates the number of Raptor coded source symbols, and 00, 01, 10, and 11 represent the number of 1, 2, 3, and 4 respectively; where N is the window length.

4. The uplink sliding window HARQ method based on Raptor code according to claim 1, characterized in that: The Raptor encoding steps are as follows: The UE side uses R10 Raptor coding, takes the transmission blocks in the first K windows as the coded source symbols, encodes to generate N coded symbols, and takes the last NK redundant coded symbols as the transmission blocks of the remaining windows; K is the number of Raptor coded source symbols.

5. The uplink sliding window HARQ method based on Raptor code according to claim 1, characterized in that: The Raptor decoding steps are as follows: The gNB first performs LDPC decoding on the transport blocks in each window. When the cumulative number of successfully decoded transport blocks reaches K, Raptor decoding is performed, and deactivated decoding is used to recover the transport blocks with decoding errors. If any source transport blocks are successfully decoded in the first K windows or all transport blocks are recovered through Raptor decoding, the last NK window needs to be transmitted with a new Raptor code redundancy block through DCI indication.

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