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

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

1 is a flowchart for explaining an example of a conventional additional information delivery method. It is a flowchart for processing and transmitting additional information in the form of a data frame like a PDU of RLC in downlink;

2 is a flowchart for explaining another example of a conventional additional information delivery method. It is a flowchart for transmitting additional information in a downlink in a symbol form separate from a data transport block by adding it to a physical layer;

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

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

5 is a diagram showing 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 symbols for the main parts of the drawing

310: RLC layer 320: MAC layer

321: MAC-d 322: MAC-c

<background-art><p>The present invention relates to a method for transmitting additional information for 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 and When applying a hybrid ARQ (hereinafter referred to as HARQ) mechanism to ensure efficient data transmission performance in the same asynchronous communication system, it relates to a method for efficiently transmitting HARQ-related additional information to be transmitted from a transmitter to a receiver .</p><p>The HARQ mechanism complements the channel coding method that can effectively adapt to signal distortion caused by interference on the channel (eg, convolutional coding or turbo coding, etc.) and the ARQ method that confirms the transmission by receiving an acknowledgment for data transmission. As a method for maximizing transmission efficiency by combining them effectively, this mechanism can be applied to data transmission in various forms, and in particular, it can be used more effectively for a radio channel with a high channel environment change and a high relative error rate. </p><p>Efforts by domestic and foreign companies to reflect HARQ in the standard for the radio section protocol for the asynchronous IMT-2000 system are continuing. Currently, there are three types of HARQ under consideration in 3GPP: I, II, and III types.</p><p>In HARQ Type I, the transmitting side transmits the data to be transmitted after forward error correction (FEC) coding having an error correction function, and the receiving side performs a decoding process, and if there is an error, discards it and controls the radio link. Error recovery can be performed by requesting retransmission through the ARQ mechanism in the link control: RLC layer. </p><p>In the case of HARQ type II, the transmitter includes more redundancy information in the retransmission than in the initial transmission, so that it can respond more strongly to errors. In addition, it is a method of reducing the probability of an error by performing error detection after soft-combining previously received and error-detected data and data received through retransmission.</p><p>HARQ Type III is basically the same as Type II, but the retransmission data has a self-decoder function, that is, error detection is performed on the retransmission data and soft combine is performed only when there is an error. </p><p>HARQ application in an asynchronous communication system such as W-CDMA is controlled by interworking of RLC, MAC and PHY layers. At the transmitting side, the RLC layer transmits side information for operating HARQ, such as a sequence number and retransmission version information, to the MAC layer together 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 the retransmission version information and transmits it to the UE through a physical channel.</p><p>At the receiving side, the UE decodes additional information for HARQ on the received data, performs decoding on the data part through this, checks the CRC, and if there is no error, it is transmitted to a higher layer. If a CRC error occurs during decoding, it is stored in the form of information in an undecoded state, and data recovery is attempted through soft combine for a radio frame having the same sequence number received thereafter.</p><p>What should be considered to apply HARQ Type II/III to W-CDMA system? First, the types of additional information required to apply HARQ, second, a method of delivering these additional information to the receiving side, and thirdly, the processing procedure at the receiving side.</p><p>In order to perform soft combine in HARQ type II/III, it is necessary to identify which data frame the retransmission is for. Since retransmission is actually performed by the RLC, the frame sequence number of the RLC must be provided as additional information, and the retransmission is repeated. Since the coding rate varies depending on the number of times, additional information on the number of retransmissions should be transmitted. That is, in the RLC of the transmitting side, as additional information for supporting HARQ Type II/III, the sequence number (RLC frame sequence number) of the RLC PDU, information on the number of retransmission repetitions (or redundancy version information), etc. It must be able to transmit to the receiving end.</p><p>In HARQ type II/III, retransmission for transmission errors uses the ARQ mechanism in the RLC layer, and soft combine to reduce the error probability of channel-coded symbols is performed by the physical layer, and the physical layer of the receiving side is the transmitting side. On the basis of the additional information transmitted from , the error is checked by decoding the data transport block and checking the CRC for the transport block. If an error exists, the fact of the error is notified to the MAC layer, and additional information on the transport block in which the error has occurred and information on the coded symbol level are stored in the buffer of the physical layer. After a certain period of time, the retransmission mechanism in the RLC layer operates, and the transmitter retransmits the previously erroneous transport block. The physical layer of 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 symbol level information of a transport block previously stored in the buffer and received symbol level information have the same RLC sequence number as additional information, more reliable symbol level information by combining these information , and performs a soft combine to reduce the error probability by performing error checking on it.</p><p>As can be seen from the above description, additional information such as the sequence number of the RLC PDU and the number of repetitions of retransmission are very important elements, and the transmission of such additional information is transmitted in the form of a data frame or separate from the data transport block in the physical layer. A method of adding in the form of a symbol may be used. Depending on these transmission methods, the processing procedure of the receiving side is also different. When the additional information is transmitted in the form of a data frame, it takes a lot of time to decode the data transport block. When the additional information is added in the form of a symbol in the physical channel, a separate processing logic for processing the additional information is required. It is required, which will be described in more detail with reference to FIGS. 1 and 2 as follows.</p><p>FIG. 1 is a flowchart for explaining an example of a conventional additional information delivery method. In the downlink, a procedure for processing and transmitting additional information in the form of a data frame like an RLC PDU is shown.</p><p>At the transmitting side, the RLC transmits a data PDU to be transmitted to the MAC (S101), and also transmits a PDU for additional information required for HARQ to the MAC (S102). The MAC processes these PDUs, configures them in the form of transport blocks, and delivers them to the physical layer (S103). In this case, the data part and the additional information part are composed of separate transport blocks, but additional information transmitted in the form of parameters to the physical layer also exists, which affects processing in the physical layer.</p><p>HARQ in the W-CDMA system does not change the channel coding rate in the physical layer in order to minimize the impact on the existing system, but adjusts the amount of puncturing in the rate mapping process so that the amount transmitted to the physical channel is generally Use the same method as when changing the channel coding rate. Accordingly, the coding rate in HARQ indicates the degree of punching, and the higher the coding rate, the lower the ability to adapt to the channel error. The additional information delivered to the transmitting-side physical layer in the form of parameters includes an indicator of whether HARQ is applied, the sequence number of the retransmitted RLC PDU, and the number of retransmissions of the RLC PDU. Assuming that the coding rates usable in the physical layer are 1, 2/3, 1/2, and 1/3, if the number of PDU retransmissions of the RLC PDU for the transport block is 0, the highest transmission efficiency 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, and 1/3 for transmission. In the case of a transport block including additional information, 1/3 coding with the lowest coding efficiency is always applied, thereby preventing the failure of decoding the transport blocks including data due to an error in the additional information (S104).</p><p>On the receiving side, the physical layer preferentially decodes a transport block including additional information among the received transport blocks and transmits it to the MAC (S105), which is again via RLC (S106) RRC (radio) capable of controlling the physical layer resource control) layer (S107). The RRC layer transfers the additional information delivered from the RLC back to the physical layer (S108). The physical layer decodes the transport blocks including data based on the additional information, and then performs a CRC check to determine whether there is an error. Transport blocks that do not have an error are transmitted to the MAC, and the transport blocks with errors are stored in the buffer together with the RLC sequence number as information in the form of transport block symbols before decoding, and the error is notified to the MAC layer (S109). ). The MAC transfers the error-free data transport block to the RLC layer (S110), and the RLC transmits the reception fact to the transmitter (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. do.</p><p>However, when the additional information is processed and transmitted in the form of a data frame like the RLC PDU, there is an advantage that the physical layer does not need to be changed, but the transmitting side generates an RLC PDU for additional additional information. There is a problem in that the information of the transport format set to be maintained in the MAC is doubled. Also, after decoding the additional information on the receiving side, it is transmitted to the physical layer through an upper layer such as RRC, and then Since the data transport block is decoded in the , there is a problem in that a delay time occurs in this process. </p><p>FIG. 2 is a flowchart for explaining another example of a conventional additional information transmission method, and shows a procedure for transmitting additional information in a downlink in the form of a symbol separate from a data transport block by adding it to a physical layer.</p><p>In this scheme, the transmitting-side RLC configures only data to be transmitted as PDUs and transmits them to the MAC, and additional information used in HARQ is transmitted to the MAC layer in the form of parameters during data PDU transmission (S201). The MAC layer transmits these additional information in the form of parameters when transferring the data transport block to the physical layer (S202). Accordingly, the physical layer of the transmitting side performs coding on the transport block for the data to be actually transmitted, and after performing separate coding, the parameters are multiplexed on the physical channel. In this case, additional information including information such as the RLC sequence number for the transport block, the HARQ identifier, and the number of PLC PDU retransmissions is separately included in the physical layer. In this case, since the transmitting MAC configures the transport block only for the data PDU transmitted from the RLC, the size of the transport block set becomes smaller than that of the method of FIG. 1 . In addition, since the additional information is transmitted in a form that can be discriminated in the physical layer, it has an advantage that decoding of the transport block received by the receiving side can also be performed quickly. </p><p>However, in the case of this method, when the amount of additional information increases, there is a problem that it is difficult to multiplex it on a channel in the physical layer, and the increase in additional information also affects the resource management of 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.</p><p>In conclusion, in the conventional method for transmitting additional information, the method in which the additional information is transmitted in the form of a data frame generates an RLC PDU for additional additional information at the transmitting side, and thus information on the transmission format set to be maintained in the MAC. In addition, after decoding the additional information on the receiving side, it is transmitted to the physical layer through an upper layer such as RRC, and then the data transport block is decoded. There is a problem in that there is a delay time, and when the amount of additional information increases, it is difficult to multiplex it on the channel in the physical layer, and additional information is added in the resource management of MAC and RRC. There was a problem that the increase in information had an effect.</p></background-art><tech><p>The present invention was created to solve the problems of the prior art, and its purpose is to transmit additional information essential in applying HARQ Type II/III for efficient data transmission in an asynchronous IMT-2000 system. A method for transmitting additional information for application of HARQ in an asynchronous mobile communication system, which minimizes changes in the physical layer of the transmitting side and the processing time required for data decoding at the receiving side when transmitting between the side and the receiving side that you want to provide.</p></tech>

<p>In order to achieve the above object, the additional information transmission method for the application of HARQ in the asynchronous mobile communication system according to the present invention is a method of transmitting additional information for HARQ when downlink transmission of packet data by applying HARQ to the 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 the form of parameters for HARQ for each packet data unit, and transmitting the generated additional information to a lower layer MAC; a second step of composing, in the MAC, the transmitted packet data unit and additional information into a data transport block and an additional information transport block, which are transport block units in the MAC, respectively, and transmitting the transmitted packet data unit and additional information to a physical layer, which is a lower layer; and a third step of performing physical channel mapping on the transmitted transport block in the physical layer and transmitting it to a counterpart receiving side.</p><p>In addition, the additional information transport block in the second step may include indicator information for determining whether to retransmit (HARQ application or not) for a data transport block within the same transmission time interval as the transport block, and the indicator Based on the information, the variable size is allocated.</p><p>According to the present invention as described above, by integrating additional information in the MAC to form a separate transport block and transmitting it to the physical layer in the same form as the data block, the requirement to change the physical layer due to the introduction of HARQ at the transmitting side is minimized. In addition, the decoding delay time at the receiving side 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 the asynchronous IMT-2000 system, thereby securing technical skills for these services and more Since it is possible to implement an effective system, it is possible to secure service competitiveness when applied to commercial services. </p><p>Hereinafter, an additional information transmission method 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.</p><p>The present invention provides a method for reconfiguring and transmitting additional information on RLC PDUs transmitted from a plurality of RLCs in units of transport blocks in the MAC layer. </p><p>3 is a block diagram of RLC and MAC layers for explaining the present invention. The MAC layer 320 is divided into a MAC-d 321 that processes dedicated data and a MAC-c 322 that processes common data, and is connected to each other. Data is switched to the MAC-c 322 . Accordingly, the MAC layer 320 can collect information on all dedicated channel data transmitted from the RLC 310, and can support control of radio resources through this.</p><p>Even when HARQ is supported, if additional information is transmitted from the RLC 310 in the form of a parameter, it is possible to collect the additional information in the MAC layer 320, and it is possible to create a separate transport block composed only of the additional information. do. </p><p>In addition, for the physical layer, only a small amount of essential hybrid ARQ application status 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, thereby minimizing the change of the physical layer. . </p><p>In addition, since the additional information on the MAC layer 320 is not included in the transport block including the additional information, it can be immediately used for decoding the data transport block in the physical layer. Therefore, an additional interface for decoding the data transport block at the receiving side is not required.</p><p>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 HARQ transmission (ie, retransmission) is requested for each RLC data PDU and what is the number of retransmission repetition times 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, it is set to 1. When the HARQ indicator is 1, an additional information transport block is formed for the RLC data PDU to be transmitted in the next TTI.</p><p>4 shows the structure of an additional information transport block according to the present invention. </p><p>The additional information transport block consists of two parts: a HARQ indicator region and a HARQ additional information region. The HARQ indicator area records whether or not HARQ is applied among data transport blocks to be transmitted within the same TTI as true/false information. For a transport block to which HARQ is applied, additional information is inserted in the HARQ additional information area of FIG. 3 . In addition, the additional information transport block is configured by allocating a variable size based on the recorded HARQ indicator information.</p><p>The additional information transport block created in this way is transmitted to the physical layer in the same way as the data block, and a coding rate capable of minimizing the influence of channel errors is applied. 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. At this time, the HARQ indicator is separately inserted into the front part of the physical channel as shown in FIG. 5 . 5 is a conceptual diagram of a transmission structure after being mapped to a dedicated data physical channel. There is an HARQ indicator at the leading end, followed by an additional information transport block, and a plurality of data transport blocks are configured after the additional information transport block. have.</p><p>The receiving side acquires the number of transport blocks through the dedicated physical control channel and recovers the data transport blocks of the dedicated physical data channel based on this. In this case, the HARQ indicator information is first decoded, and the HARQ indicator is If it indicates that it has not been used, the existing processing is performed. </p><p>If the HARQ indicator has a value of 'true', the additional information transport block is decoded, and through this, the HARQ-applied block and the non-applied block among the transport blocks are distinguished and the corresponding processing is performed. For blocks to which HARQ is applied, if soft co-bining is required based on the RLC sequence number and redundancy version information, this is performed, and HARQ processing for error detection by CRC is performed.</p><p>6 shows an additional information processing procedure according to the present invention. The basic procedure is similar to the method of mapping additional information to a physical channel and the interface is similar, but as in step S600, the additional information is transmitted in the MAC as a transport block. It has a difference from the existing methods of FIGS. 1 and 2 in that it performs smooth physical channel mapping. </p><p>The present invention described above has the following characteristics.</p><p>In the MAC layer, additional information for HARQ is configured as a separate transport block and transmitted, and a HARQ branch area for determining whether or not HARQ is applied to a transport block within the same TTI is added to the additional information transport block, and the receiving side transmits it. HARQ-applied transport blocks are distinguished through The additional information transport block is placed next to the HARQ indicator indicator, and for the additional information transport block, the transmitter allocates a separate transport format indicator for transmission, or for the additional information transport block, the transmitter uses a separate transport format Without allocating an indicator, the additional information field may be processed with a fixed size based on the TFCI information.</p>

<p>As described in detail above, the additional information transmission method for applying HARQ in an asynchronous communication system according to the present invention is essential in applying HARQ Type II/III for efficient data transmission in an asynchronous data mobile communication system. When transmitting additional information between the transmitting side and the receiving side, the change in the physical layer of the transmitting side is minimized and the processing time required for data decoding at the receiving side is minimized. That is, by integrating additional information in the MAC to form a separate transport block and transmitting it to the physical layer in the same form as the data block, the requirement for changing the physical layer due to the introduction of HARQ at the transmitting side is minimized and decoding at the receiving side It creates the effect of reducing the delay time. Accordingly, the present invention proposes a method for effective transmission of HARQ additional information, which is essential when HARQ type II/III is applied for efficient service of asynchronous systems such as asynchronous IMT-2000 systems and/or W-CDMA systems. By doing so, technology for these services can be secured, and more effective system implementation is possible, so when applied to commercial services, service competitiveness can be secured.</p>