KR100352895B1 - A transmission method of side information to support hybrid ARQ in W-CDMA system - Google Patents

Abstract

According to the present invention, when a hybrid HARQ mechanism is applied to ensure efficient data transmission performance in an asynchronous communication system such as a wideband code division multiple access (W-CDMA) system or an asynchronous IMT-2000 system, The present invention relates to a method for efficiently transmitting HARQ-related additional information to be transmitted to a receiving side. In a plurality of RLCs, a plurality of packet data units (PDUs) and parameter information for HARQ for each packet data unit are generated. A first step of transmitting to the lower layer MAC; In the MAC, transmitting the transmitted packet data unit and the additional information into a data transport block and an additional information transport block, each of which is a transport block unit in the MAC, and delivering the additional information transport block to a lower layer physical layer; And a third step of physically mapping the transmitted transport block to a counterpart receiving side in the physical layer, thereby minimizing the change in the transmitting physical layer and required for data decoding at the receiving side. Minimize processing time.

Description

A transmission method of side information to support hybrid ARQ in W-CDMA system

The present invention relates to a method for transmitting additional information for the application of hybrid ARQ in an asynchronous mobile communication system, and more particularly, to a wideband code division multiple access (W-CDMA) system or an asynchronous IMT-2000 system. The present invention relates to a method for efficiently transmitting HARQ-related additional information to be transmitted from a transmitting side to a receiving side when applying a hybrid ALQ (hereinafter referred to as HARQ) mechanism to ensure efficient data transmission performance in the same asynchronous communication system. .

The HARQ mechanism complements the channel coding method (e.g., convolutional coding or turbo coding, etc.) that can effectively adapt to the distortion of the signal due to interference on the channel, and the ARQ method of confirming transmission by receiving an acknowledgment of the data transmission. By combining them, as a method for maximizing transmission efficiency, this mechanism can be applied in various forms to data transmission, and can be used more effectively for a radio channel with a severe channel environment change and a high relative error rate.

The efforts of domestic and foreign companies to reflect HARQ in the standard for the radio section protocol for the asynchronous IMT-2000 system are continuing. There are three types of HARQ currently considered in 3GPP, I, II and III types.

In HARQ Type I, the transmitting side transmits after forward error correction (FEC) coding with error correction for data to be transmitted, and the receiving side performs decoding process, discards any errors and radio link control (radio Error control can be performed by requesting retransmission through the ARQ mechanism in the link control: RLC) layer.

In the case of HARQ type II, the transmitting side includes more redundancy information at the time of retransmission than the initial transmission, thereby making it possible to respond more strongly to the error. In addition, the receiving side reduces the probability of occurrence of an error by performing a soft combine between data previously received and detected by an error and data received by retransmission.

HARQ type III is basically the same as type II, but the retransmission data has a self-decoder function, that is, to perform error detection on the retransmission data and to perform soft combine only when an error exists.

HARQ application in an asynchronous communication system such as W-CDMA is controlled by interworking of the RLC, MAC and PHY layers. At the transmitting side, the RLC layer transmits side information for operating HARQ, such as sequence number and retransmission version information, to the MAC layer along with a packet data unit (PDU). The MAC layer generates a data synchronization process and a Transport Format Combination Indicator (TFCI) and delivers it to the PHY layer, which is a physical layer. The physical layer performs rate matching according to retransmission version information and transmits to the UE through a physical channel.

At the receiving side, the UE decodes additional information for HARQ on the received data, performs decoding on the data portion through this, checks the CRC, and delivers to the upper layer if there is no error. If a CRC error occurs during decoding, it is stored in the form of information in an undecoded state, and then data recovery is attempted through soft combine for radio frames having the same sequence number.

In order to apply HARQ type II / III to W-CDMA system, First, the types of additional information required for applying HARQ, second, a method of transmitting these additional information to the receiving side, and third, a processing procedure at the receiving side.

In order to perform soft combine in HARQ type II / III, it is possible to identify which data frame is retransmission. In practice, since retransmission is performed by RLC, the frame sequence number of RLC must be provided as additional information. Since the coding rate varies depending on the number of times, additional information on the number of retransmissions must be transmitted. That is, in the RLC of the transmitting side, as the additional information for supporting the HARQ type II / III, the lower layer and the sequence number (RLC frame sequence number), retransmission repetition information (or redundancy version information), etc. of the RLC PDU as described above are used. Should be able to transmit to the receiver.

In HARQ type II / III, retransmission for transmission error uses the ARQ mechanism in the RLC layer, and a soft combine to reduce the error probability of channel coded symbols is performed by the physical layer. On the basis of the additional information transmitted in the A, the data transmission block is decoded and the CRC of the transport block is checked for error. If an error exists, the MAC layer is notified of the error, and the additional information and coded symbol level information on the transport block in which the error occurs are stored in the buffer of the physical layer. After a certain time, the retransmission mechanism in the RLC layer is activated, and the sender retransmits a previously failed transport block. The physical layer on the receiving side decodes the received data and checks whether there is an error in the transport block. In this case, when an error is detected again, when the symbol level information of the transport block previously stored in the buffer and the received symbol level information have the same RLC sequence number as additional information, by combining these pieces of information, more reliable symbol level information is obtained. Create a soft combine to reduce the probability of error by creating an error check.

As can be seen from the above description, additional information such as sequence number and retransmission repetition number of the RLC PDU is a very important factor, and the transmission of such additional information is transmitted in the form of a data frame or separate from the data transmission block in the physical layer. The addition method in symbol form may be used. Depending on these transmission methods, the processing procedure on the receiving side is also different. When the additional information is transmitted in the form of a data frame, it takes a long time to decode the data transmission block. When the additional information is added in the form of symbols in the physical channel, a separate processing logic for processing the additional information is provided. If required, this will be described in more detail with reference to FIGS. 1 and 2 as follows.

1 is a flowchart illustrating an example of a conventional method of transmitting additional information, and a procedure for a case in which additional information is processed in a form of a data frame such as a PDU of an RLC in a downlink is shown.

In the transmitting side, the RLC transfers the data PDU to be transmitted to the MAC (S101), and also transfers the PDU for additional information required for HARQ to the MAC (S102). The MAC performs processing on these PDUs, configures them in the form of transport blocks, and delivers them to the physical layer (S103). In this case, the data portion and the additional information portion are composed of separate transport blocks, but additional information transmitted in the form of parameters to the physical layer also exists, affecting the processing in the physical layer.

In the W-CDMA system, HARQ does not change the channel coding rate in the physical layer to minimize the influence on the existing system, and adjusts the amount of puncturing during the rate mapping process. Use the same method to change the channel coding rate. Therefore, the coding rate in HARQ indicates the degree of punching, and the higher the coding rate, the lower the ability to adapt to channel error. Additional information transmitted in the form of a parameter to the transmitting physical layer includes an indicator of whether HARQ is applied, a sequence number of a retransmission RLC PDU, and a number of retransmissions of the RLC PDU. Assuming that the coding rates available in the physical layer are 1, 2/3, 1/2, 1/3, if the PDU retransmission count of the RLC PDU for a transport block is 0, the highest transmission efficiency of 1 is used. As the number of retransmissions (redundancy version value) of the RLC PDU increases, the coding rate is changed in the order of 2/3, 1/2, 1/3. In the case of a transport block including additional information, 1/3 coding having the lowest coding efficiency is always applied to prevent a case in which the transport blocks including data cannot be decoded due to an error of the additional information (S104).

On the receiving side, the physical layer preferentially decodes a transport block including additional information among the received transport blocks to the MAC (S105), which is again RRC (radio) capable of controlling the physical layer through RLC (S106). resource control) to the layer (S107). The RRC layer forwards the additional information transmitted from the RLC to the physical layer (S108). The physical layer decodes transport blocks including data based on these additional information, and then performs a CRC check to determine whether there is an error. A transport block without an error is transmitted to the MAC, and a transport block having an error is stored in a buffer together with the RLC sequence number in the form of a transport block symbol before decoding and notified of the error to the MAC layer (S109). ). The MAC transmits the data transport block without error to the RLC layer (S110), and the RLC transmits the reception fact to the transmitting side (S111). If the received data transport block is retransmitted information, it is checked whether there is a block having the same RLC sequence number in the buffer of the physical layer. If there is, the soft combine is performed, and then decoding is performed to reduce the probability of error. do.

However, when the additional information is processed and transmitted in the form of a data frame like the PDU of the RLC, the physical layer does not need to be changed, but the transmitting side generates the RLC PDU for additional additional information. There is a problem that the information of the transport format set to be maintained in the MAC is doubled, and after decoding the additional information at the receiving side, the information is transmitted to the physical layer through an upper layer such as RRC. Since decoding is performed on the data transport block, there is a problem that a delay occurs in this process.

FIG. 2 is a flowchart for explaining another example of a conventional method of transmitting additional information, and a procedure for a case in which additional information is added to a physical layer in a symbol form separate from a data transmission block in downlink is transmitted.

In this scheme, the transmitting side RLC configures only data to be transmitted into a PDU and delivers it to the MAC, and additional information used in HARQ is transmitted to the MAC layer in the form of a parameter when transmitting the data PDU (S201). The MAC layer delivers these additional information in the form of parameters when delivering the data transport block to the physical layer (S202). Therefore, the physical layer on the transmitting side actually performs coding on a transport block for data to be transmitted, and after performing separate coding, parameters are multiplexed on the physical channel. In this case, additional information consisting of information such as the RLC sequence number, HARQ identifier, PLC PDU retransmission number, etc. for the transport block is separately included in the physical layer. In this case, since the transmitting MAC configures a transport block only for data PDUs transmitted from the RLC, the size of the transport block set is smaller than that of the scheme of FIG. In addition, since the additional information is transmitted in a form that can be identified in the physical layer, decoding of the transport block received at the receiving side can also be performed quickly.

However, in this scheme, when the amount of additional information increases, there is a problem that it is difficult to multiplex it on the channel in the physical layer, and the increase of the additional information also affects resource management of the MAC and RRC. Since the procedure at the receiving side indicated by step S203 in FIG. 2 is a known procedure regardless of the present invention and technical background, a description thereof will be omitted.

In conclusion, in the conventional method of transmitting additional information, the method of transmitting additional information in the form of a data frame generates an RLC PDU for additional additional information at the transmitting side, thereby transmitting information of a transport format set to be maintained in the MAC. Is increased by 2 times, and the decoding side of the additional information is received at the receiving side and then transferred to the physical layer through an upper layer such as RRC, and then the decoding of the data transport block is performed. There is a problem that a delay occurs, and a method of adding and transmitting a symbol in a physical channel is difficult to multiplex it on the channel when the amount of additional information increases, and also in resource management of MAC and RRC. There was a problem that the increase of information affects.

The present invention was created to solve the above-mentioned conventional problems, and an object thereof is to transmit additionally required additional information in applying HARQ type II / III for efficient data transmission in an asynchronous IMT-2000 system. A method of transmitting additional information for application of HARQ in an asynchronous mobile communication system, which minimizes a change in a transmitting physical layer and minimizes processing time required for data decoding at a receiving side when transferring between a receiving side and a receiving side. It is to provide.

1 is a flowchart illustrating an example of a conventional method of transmitting additional information, which is a flowchart illustrating a case in which additional information is processed in a downlink with a data frame form like a PDU of an RLC.

2 is a flowchart illustrating another example of a method of transmitting additional information, which is a flowchart illustrating a case in which additional information is added to a physical layer in a symbol form separate from a data transmission block and transmitted in downlink.

3 is a block diagram of an RLC and MAC layer for explaining the present invention;

4 is a structural diagram showing a format of an additional information transport block according to the present invention;

5 is a diagram illustrating a conceptual structure after physical channel mapping according to the present invention;

6 is a flowchart illustrating an additional information processing procedure according to the present invention.

※ Explanation of code for main part of drawing

310: RLC layer 320: MAC layer

321: MAC-d 322: MAC-c

In order to achieve the above object, a method of transmitting additional information for applying HARQ in an asynchronous mobile communication system according to the present invention includes applying additional information for HARQ when transmitting downlink packet data by applying HARQ to an asynchronous data communication system. A transmission method comprising: a first step of generating, in a plurality of RLCs, a plurality of packet data units (PDUs) and additional information in a parameter form for HARQ for each packet data unit and transmitting the additional information in a lower layer to a MAC; In the MAC, transmitting the transmitted packet data unit and the additional information into a data transport block and an additional information transport block, each of which is a transport block unit in the MAC, and delivering the additional information transport block to a lower layer physical layer; And a third step of, at the physical layer, transmitting the transmitted transport block to a counterpart receiver by performing physical channel mapping.

The additional information transport block of the second step may be configured to include indicator information for determining whether to retransmit (whether to apply HARQ) to a data transport block within the same transmission time interval as the transport block. Based on the information, the variable size should be allocated.

According to the present invention, by combining the additional information in the MAC to configure a separate transport block and deliver it to the physical layer in the same form as the data block, to minimize the physical layer change requirements due to the introduction of HARQ on the transmitting side In addition, the decoding delay time at the receiver is reduced. Accordingly, the present invention provides a method for effective transmission of additional information essential in HARQ type II / III required for efficient data service in an asynchronous IMT-2000 system, thereby securing technology for these services. Effective system implementation is possible, so it is possible to secure service competitiveness when applied to commercial services.

Hereinafter, a method of transmitting additional information for applying HARQ in an asynchronous mobile communication system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The present invention proposes a method for reconfiguring and transmitting additional information on RLC PDUs transmitted from a plurality of RLCs in units of transport blocks in a MAC layer.

3 is a block diagram of an RLC and MAC layer for explaining the present invention. The MAC layer 320 is divided into MAC-d 321 for processing dedicated data and MAC-c 322 for processing common data and connected to each other. The data is switched to the MAC-c 322. Accordingly, the MAC layer 320 may collect information on all dedicated channel data transmitted from the RLC 310, thereby supporting control of radio resources.

Even in the case of supporting HARQ, if the additional information is transmitted from the RLC 310 in the form of a parameter, the additional information can be collected in the MAC layer 320, and a separate transport block composed of only the additional information can be generated. Do.

In addition, only a small amount of required hybrid ARQ application indicator information is inserted into the physical channel, and most of the additional information is transmitted in the form of a transport block configured in the MAC layer 320 to minimize the change of the physical layer. .

In addition, since the transport block including the additional information does not include the additional information on the MAC layer 320, it may be immediately used for decoding the data transport block in the physical layer. Therefore, no additional interface is required at the receiving side for decoding the data transport block.

The MAC layer 320 of the transmitting side schedules RLC data PDUs to be transmitted within a transmission time interval (TTI), and then checks additional parameters for each RLC data PDU. At this time, it is checked whether each RLC data PDU is required for HARQ transmission (ie, retransmission) and the number of retransmission repetition numbers of the RLC data PDU. If all RLC data PDUs to be transmitted in the next TTI do not use HARQ, the HARQ indicator is set to 0, and in other cases, 1 is set. If the HARQ indicator is 1, the additional information transport block is configured for the RLC data PDU to be transmitted in the next TTI.

4 shows a structure of an additional information transport block according to the present invention.

The additional information transport block is composed of two parts, the HARQ indicator area and the HARQ side information area. The HARQ indicator area records as true / false information whether HARQ is applied among data transmission blocks to be transmitted in the same TTI. For transport blocks to which HARQ is applied, additional information is inserted in the HARQ additional information region of FIG. 3. In addition, the additional information transport block is configured by assigning a variable size based on the recorded HARQ indicator information.

This additional information transport block is delivered to the physical layer in the same manner as the data block, and a coding rate is applied to minimize the influence of channel error. The remaining data transport blocks are also coded based on retransmission repetition count information (redundancy version information) among the additional information. The coded data is mapped to a physical channel. In this case, the HARQ indicator is separately inserted into the front of the physical channel as shown in FIG. 5. FIG. 5 conceptually illustrates a transmission structure after mapping to a dedicated data physical channel, in which a HARQ indicator is located at the top, followed by an additional information transport block, and a plurality of data transport blocks are configured after the additional information transport block. have.

The receiving side acquires the number of transport blocks through the dedicated physical control channel, and restores the data transport block of the dedicated physical data channel based on this. In this case, the HARQ indicator is first decoded, and the HARQ indicator is HARQ lyrics. If it is not used, the existing process is performed.

If the HARQ indicator has a value of true, the additional information transport block is decoded, and the corresponding processing is performed by dividing a block to which HARQ is applied and a block not to be applied among the transport blocks. If a soft combine is required for the block to which HARQ is applied based on the RLC sequence number and the redundancy version information, the HARQ process for performing error detection by CRC is performed.

6 shows an additional information processing procedure according to the present invention. The basic procedure is similar to the method of mapping the additional information to the physical channel, but the interface is similar, but the additional information is configured as a transport block in the MAC and transmitted in step S600. In this respect, there is a difference from the conventional methods of FIGS. 1 and 2, and thus, physical channel mapping is smoothly performed.

The present invention described above has the following features.

In the MAC layer, additional information for HARQ is configured and transmitted as a separate transport block, and the receiving side adds an HARQ branch region to determine whether HARQ is applied to a transport block within the same TTI. HARQ is applied to distinguish the transport block, and the additional information transport block is allocated to the variable size HARQ indicator region based on the information, and if there is a HARQ applied transport block in the physical channel mapping process, having additional information about this The additional information transport block is located next to the HARQ indicator, and the additional information transport block is allocated to the additional information transport block by transmitting a separate transport format indicator, or the additional information transport block is transmitted separately by the transmitting party. Instead of assigning an indicator, the side information field can be processed to a fixed size based on TFCI information. There.

As described in detail above, the additional information transmission method for applying HARQ in the asynchronous communication system according to the present invention is essential in applying HARQ type II / III for efficient data transmission in the asynchronous data mobile communication system. When the additional information is transmitted between the transmitting side and the receiving side, the change in the transmitting physical layer is minimized and the processing time required for data decoding at the receiving side is minimized. In other words, by integrating the additional information in the MAC to form a separate transport block and forwarding it to the physical layer in the same form as the data block, it minimizes the requirement to change the physical layer due to the introduction of HARQ at the transmitting side and decoding at the receiving side Creates the effect of reducing latency. Accordingly, the present invention proposes a method for effective transmission of HARQ side information required when applying HARQ type II / III for efficient service of an asynchronous system such as an asynchronous IMT-2000 system and / or a W-CDMA system. By securing the technical skills for these services and realizing more effective system, it is possible to secure service competitiveness when applied to commercial services.

Claims (4)

In the method of transmitting additional information for HARQ when transmitting downlink packet data by applying HARQ to an asynchronous data communication system, A first step of generating a plurality of packet data units (PDUs) and additional information in a parameter form for HARQ for each packet data unit in a plurality of RLCs and transmitting the additional information in a lower layer MAC; In the MAC, transmitting the transmitted packet data unit and the additional information into a data transport block and an additional information transport block, each of which is a transport block unit in the MAC, and delivering the additional information transport block to a lower layer physical layer; And And in the physical layer, a third step of physically mapping the transmitted transport block and transmitting the physical block to a counterpart receiver. The method of claim 1, The additional information transport block of the second step is configured to include indicator information for determining whether to retransmit the data transport block within the same transmission time interval as the transport block. Method of transmitting additional information for application. The method of claim 2, The additional information transport block is allocated in a variable size based on the indicator information. The additional information transmission method for the application of HARQ in the asynchronous mobile communication system, characterized in that the allocation. The method of claim 2, wherein the indicator information is added for each transport block and transmitted.