Method for implementing mixed automatic retransmit in communication system containing repeater station

A hybrid automatic retransmission and communication system technology, applied in the field of hybrid automatic retransmission, can solve the problem of hybrid automatic retransmission that does not include base stations and terminals, and achieve the effects of improving transmission quality, realizing transparency, and improving performance

Inactive Publication Date: 2007-10-03
HUAWEI TECH CO LTD
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AI-Extracted Technical Summary

Problems solved by technology

[0007] However, in the 802.16 protocol, it does not include how to realize the hybrid automatic retransmission p...
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Method used

Step 107, adopt the mode of bitmap to encode the state of HARQ data block: because the state of data block has three kinds, generally speaking, need to adopt two bits to encode it, under the larger situation of feedback amount , this encoding method occupies more bandwidth. The present invention adopts a two-step encoding method, which can reduce the amount of feedback. The format of the message fed back by the relay station to the base station is shown in FIG. 8 . Among them, the message type field is used to identify the type of the message to distinguish it from other messages; the bitmap 1 length field indicates the length of the bitmap 1, and its unit can be the number of bytes or bits; the bitmap 1 field is used for In order to feed back the reception status of the terminal to the HARQ data block, that is, ACK or NAK, the kth bit of the bitmap indicates the reception status of the kth HARQ data block that the relay station is responsible for forwarding in the terminal. For example, binary "1" can ...
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Abstract

A method for realizing mixed automatic retransmission in communication system containing relay station includes sending data block to opposite end by terminal or base station through relay station, returning reception state of data block back to sending end by relay station after sending process is finished and confirming that it is necessary to retransmit data block or not by sending end according to said reception state.

Application Domain

Technology Topic

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  • Method for implementing mixed automatic retransmit in communication system containing repeater station
  • Method for implementing mixed automatic retransmit in communication system containing repeater station
  • Method for implementing mixed automatic retransmit in communication system containing repeater station

Examples

  • Experimental program(1)

Example Embodiment

[0062] In the present invention, the HARQ process after introducing the relay station into the communication system using time division duplex (TDD) and OFDMA mode similar to the 802.16 protocol is realized.
[0063] After introducing the relay station, the physical frame structure of the base station, the relay station and the terminal can be as shown in Figure 5, or as shown in Figure 6, where the part filled with oblique lines is the transmitting state, the part without filling is the receiving state, and the dotted line box is idle state, the grid filling part is the terminal frame header of the next frame. The base station frame includes four parts: terminal downlink subframe, relay downlink subframe, terminal uplink subframe and relay uplink subframe. The terminal downlink subframes and terminal uplink subframes are used by the base station to provide services for terminals within its coverage, and the relay downlink subframes and relay uplink subframes are used to provide services for relay stations under the jurisdiction of the base station. Corresponding to the base station frame, the relay station frame is also divided into four parts. In the terminal downlink subframe and terminal uplink subframe, it provides services for the terminals within the jurisdiction of the relay station. In the relay downlink subframe, it receives data from the base station. Send data to the base station in the uplink subframe. The relay station acquires the time-frequency resource allocation information of the relay downlink subframe and the relay uplink subframe by receiving the relay frame header. The terminal obtains synchronization with the base station or relay station through the terminal synchronization sequence, and obtains its own time-frequency resource allocation information by receiving the terminal frame header. Only the time-frequency resource allocation information of the terminal downlink subframe and the terminal uplink subframe is given in the terminal frame header, so Data is only received in the terminal downlink subframe, data is sent in the terminal uplink subframe, and the terminal does not work in the time slots corresponding to the relay downlink subframe and the relay uplink subframe. The idle area in FIG. 5 is only used to indicate that the relay station and the base station use the time-frequency resources orthogonally. In fact, the time-frequency resources can be divided arbitrarily as long as the orthogonality is ensured.
[0064] The two frame structures shown in FIG. 5 and FIG. 6 have in common that the time-frequency resource allocation of the downlink subframe of the terminal and the uplink subframe of the terminal by the base station and the relay station are uniformly given by the terminal frame header. Even in the frame structure shown in Figure 6, although the relay station also sends the terminal frame header, the information it sends is completely consistent with the base station, and the terminal frame header sent by the relay station must be sent to it by the base station in the previous frame. The purpose of this is to ensure the transparency of the relay station to the terminal. The terminal frame header received by the terminal is the superposition of the signals sent by the base station and the relay station, but the terminal cannot see the existence of the relay station.
[0065] The essential difference between the frame structure shown in Figure 5 and the frame structure shown in Figure 6 is that in the first frame structure, the relay station does not send the terminal synchronization sequence and the terminal frame header; while in the second frame structure, the relay station sends the terminal synchronization sequence and Terminal frame header.
[0066] In the terminal downlink subframe, when the terminal is in the receiving state, the relay station is in the transmitting state; in the terminal uplink subframe, when the terminal is in the transmitting state, the relay station is in the receiving state.
[0067] In the present invention, the terminal or the base station forwards the data block to the opposite end through the relay station, and the relay station returns the receiving state of the data block to the sending end after sending, and the sending end determines whether to retransmit the data block according to the receiving state, and The retransmission is performed at the relay station or at the opposite end, thereby realizing hybrid automatic retransmission in a communication system including a relay station. Here, the base station or terminal that sends the data block is called the sender, and the destination that receives the data block is called the opposite end.
[0068] FIG. 7 is a flowchart of a method for forwarding a downlink HARQ data block through a relay station in an embodiment of the present invention, specifically performing the following steps:
[0069] Step 101, the base station sends the HARQ data block to be sent to the terminal to the relay station to which the terminal belongs in the relay downlink subframe;
[0070] Step 102, the base station allocates time-frequency resources for the terminal in the terminal frame header, the time-frequency resources are used by the relay station to forward the data block, and inform the terminal of the parameters of the data block, the parameters include the HARQ type, sequence number and modulation of the data block In this way, the terminal can directly receive the information about the time-frequency resources and parameters of the HARQ data block sent by the base station or forwarded by the relay station.
[0071] Step 103, the relay station judges whether the HARQ data block is correctly received and demodulated, and if so, sends the data block to the terminal through the terminal downlink subframe in the time-frequency resource allocated by the base station; otherwise, does not send the data block.
[0072] Step 104, the terminal decodes the terminal frame header, and receives the data block in the time-frequency resource allocated to itself.
[0073] Step 105, the terminal decodes and verifies the received HARQ data block according to the parameter information, and judges whether the data block has passed the verification, and if so, feeds back acknowledgment (ACK) information in the HARQ sub-channel; otherwise, feedbacks no Acknowledge (NAK) information.
[0074] If the HARQ data block is retransmitted data, before decoding, the terminal needs to combine the retransmitted data with its cached data to obtain diversity gain.
[0075] Step 106. According to the feedback information and the state information of the HARQ data block received by the relay station from the base station, the relay station sets three states to mark the data block. The three states are respectively: the data block is correctly received by the terminal (ACK), and the data block is not received by the terminal. The relay station correctly received (NAK) and the data block was correctly received by the relay station but not correctly received by the terminal (RACK).
[0076] Step 107. Encode the state of the HARQ data block in the form of a bitmap: because there are three states of the data block, in general, two bits are required to encode it. In the case of a large amount of feedback, this The coding method occupies more bandwidth. The present invention adopts a two-step coding method, which can reduce the amount of feedback. The format of the message fed back by the relay station to the base station is shown in FIG. 8 . Among them, the message type field is used to identify the type of the message to distinguish it from other messages; the length field of bitmap 1 indicates the length of bitmap 1, and its unit can be the number of bytes or bits; the field of bitmap 1 is used for In order to feed back the reception status of the HARQ data block of the terminal, that is, ACK or NAK, the kth bit of the bitmap indicates the reception status of the kth HARQ data block that the relay station is responsible for forwarding in the terminal. For example, binary "1" can be used to indicate ACK , binary "0" means NAK or vice versa, if binary "1" means correct reception, binary "0" means incorrect reception, then the value of the kth bit of the bitmap is equal to the relay station receiving the kth HARQ data block from the base station The state and the feedback state of the terminal after receiving the data block are subjected to "AND" operation bit by bit; if binary "1" is used to indicate that it is not received correctly, and binary "0" is used to indicate that it is not received correctly, then its value is equal to the receiving state of the relay station and Bitwise OR operation of terminal feedback status. The "bitmap 2" field is used to indicate the reception status of the relay station for the HARQ data block corresponding to the NAK bit in bitmap 1.
[0077] The message format shown in FIG. 8 includes at least the above items, but is not limited thereto. For example, a field may be added to identify the total length of the message. In addition, the representation of the bitmap is not limited to this, it only needs to be able to identify the receiving status of the data block.
[0078]The encoding methods of bitmap 1 and bitmap 2 are illustrated below with an example. As shown in FIG. 9, binary "1" is used to represent the correct receiving state, and binary "0" is used to represent the incorrect receiving state. The receiving status of the relay station indicates that errors occurred in the 8th and 16th HARQ data blocks it received from the base station, and the feedback status of the terminal indicates that the 4th, 8th, 11th and 12th HARQ data blocks were not received correctly. Then the relay station performs bitwise "AND" operation according to these two state tables, and obtains bitmap 1=(1110111011001110) 2 ,in"() 2 "Represents a binary number. Here, if binary "0" is used to represent the correct receiving state, and binary "1" is used to represent the incorrect receiving state, it is a bitwise "OR" operation. Bitmap 2 shows that the relay station is equal to bitmap 1 The receiving status of the data block corresponding to the bit of 0, the bit equal to 0 in bitmap 1 is the 4th, 8th, 11th, 12th and 16th bits, according to the receiving status of the HARQ data block corresponding to these bits by the relay station, bitmap 2 can be obtained =(10110) 2. For the 16th HARQ data block, although the result of decoding the terminal feedback information by the relay station is ACK, because the relay station itself did not receive the data block correctly, the relay station believes that its decoding of the terminal feedback channel is unreliable Yes, when reporting to the base station, the NAK status is still fed back to the HARQ data block. After receiving the HARQ data block status feedback message from the relay station, the base station can judge the transmission status of each HARQ data block by combining the bitmap 1 and bitmap 2 fields in the message.
[0079] Step 108, the relay station encapsulates the bitmap into the message shown in Figure 8, and sends the message to the base station.
[0080] Step 109, the base station decodes the message, and judges whether the state of the HARQ data block is ACK, if yes, it indicates that the data block has been correctly transmitted to the terminal, and ends the processing of the data block; otherwise, execute step 110 .
[0081] Step 110, judging whether the state of the data block is NAK, if yes, it indicates that an error has occurred in the data block when the base station transmits it to the relay station, and executes step 111; otherwise, it indicates that the data block is correctly transmitted to the relay station by the base station, However, an error occurs during the transmission from the relay station to the terminal, and step 112 is executed.
[0082] Step 111 , the base station generates a data block that needs to be retransmitted, and executes step 101 .
[0083] Step 112, the base station allocates time-frequency resources for the terminal to be used by the relay station to send the data block that needs to be retransmitted to the terminal, and provides the parameters of the retransmitted data block while allocating the time-frequency resource, and the parameter includes the HARQ of the retransmitted data block Type, serial number and modulation method.
[0084] Step 113 , the relay station forwards the retransmitted data block to the terminal through the downlink terminal subframe in the time-frequency resource allocated by the base station to the terminal, and executes step 104 .
[0085] In the above process, for the frame structure shown in Figure 5, the terminal can directly receive the time-frequency resource allocation information sent by the base station, therefore, the relay station used in this case does not forward the terminal frame header; and for Figure 6 In the frame structure shown, the base station and the relay station send the same terminal frame header at the same time, and the terminal frame header sent by the relay station is sent to it by the base station in the relay downlink subframe of the previous frame, because this step is only available in the second frame format Therefore, this step is not written in the above process, but it does not mean that this step can be omitted.
[0086] FIG. 10 is a flowchart of a method for forwarding an uplink HARQ data block through a relay station in an embodiment of the present invention, specifically performing the following steps:
[0087] Step 201, the base station has allocated uplink time-frequency resources for the terminal in the terminal frame header, and the time-frequency resources are used for the terminal to send HARQ data blocks. The base station notifies the terminal of parameters related to the HARQ data block, and the parameters include the HARQ type, sequence number and modulation mode of the data block. For the frame structure shown in FIG. 6 , the base station and the relay station send the time-frequency resource allocation message and the HARQ data block parameter message at the same time.
[0088] Step 202, the terminal sends the HARQ data block to the relay station in the time-frequency resource allocated by the base station to the relay station through the uplink subframe of the terminal according to the data block parameters.
[0089] Step 203: After receiving the HARQ data block sent by the terminal, the relay station notifies the base station of its receiving status of the HARQ data block through an uplink HARQ data block receiving status message. The message format is shown in Figure 11. The message contains the receiving status of all uplink HARQ data blocks received by the relay station in the same frame, where the message type field identifies the message as an uplink HARQ receiving status message; the bitmap length field indicates the bitmap The length of the field can be in units of bytes or bits; the kth bit of the bitmap field indicates the receiving status of the kth HARQ data block that the relay station is responsible for receiving, and can be represented by binary "0" Receive failure (NAK), use binary "1" to indicate correct reception (ACK), or use binary "1" to indicate reception failure (NAK), and use binary "0" to indicate correct reception (ACK).
[0090] Step 204, if the relay station correctly receives the HARQ data block sent by the terminal, forward the HARQ data block to the base station in the uplink time-frequency resources allocated by the base station; otherwise, the data block is not sent;
[0091] Step 205, the base station generates an uplink HARQ data block receiving status message to be sent to the terminal according to the uplink HARQ data block receiving status message sent by the relay station, and then sends the receiving status message to the terminal. The content of this message is the same as that of the uplink HARQ data block receiving status message sent by the relay station, but the message format may be different, because the protocols of the sender and receiver may be different in the two cases. The sending method of the reception status message depends on the specific system. It can be sent on a dedicated HARQ feedback channel, or the feedback information of all uplink HARQ data blocks can be summarized in a message through a broadcast message, and sent in the form of a bitmap. , using each bit of the bitmap to represent the receiving status of the corresponding HARQ data block.
[0092] Step 206 , the base station judges whether there is a HARQ data block that needs to be retransmitted by the terminal according to the received uplink HARQ data block receiving status message, if yes, execute step 201 ; otherwise, execute step 207 .
[0093] The terminal receives the HARQ data block reception status message, if it receives the acknowledgment (ACK) information, it thinks that the data block has arrived at the receiving end correctly; if it receives the non-acknowledgement (NAK) information, it thinks that the data block it sent has not arrived correctly Receiving end. In fact, in the present invention, even if the terminal receives the acknowledgment information, it only indicates that the data sent by it has arrived at the relay station correctly, but it is not necessarily whether the data has been correctly forwarded to the base station. If the data is not correctly forwarded to the base station , then this part of data is retransmitted through the negotiation between the base station and the relay station. The terminal is completely unaware of the data transmission status between the base station and the relay station. The purpose of this is to ensure the transparency of the relay station to the terminal.
[0094] Step 207, the base station judges whether there is a HARQ data block that needs to be retransmitted by the relay station according to its own HARQ data block reception status, if yes, the base station allocates uplink time-frequency resources to the relay station, and sends it the HARQ data block that needs to be retransmitted The parameter message is used for the relay station to retransmit the HARQ data block; otherwise, it ends.
[0095] In the above process, step 203 and step 204 are performed in no order, and the relay station may also forward data first, and then send an uplink HARQ data block reception status message to the base station.
[0096] Through the present invention, the relay system can support HARQ transmission and improve the system performance; without changing the existing terminal, the compatibility with the traditional terminal is ensured.
[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be The scheme shall be modified or equivalently replaced without departing from the spirit and scope of the technical scheme of the present invention.
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