KR100937299B1 - Method of performing hybrid automatic repeat request harq in wireless communication system - Google Patents

Abstract

A method of performing a hybrid automatic repeat request (HARQ) in a wireless communication system performed by a terminal is provided. The method receives a downlink allocation in a first subframe, wherein the downlink allocation is transmitted based on a control channel element (CCE) which is a logically indexed resource unit, and in the first subframe Receives downlink data on a downlink shared channel, the downlink shared channel is allocated according to the downlink allocation, and receives an ACK / NACK signal indicating successful or unsuccessful reception of the downlink data. Generating and transmitting the ACK / NACK signal or the representative ACK / NACK signal using a subset of uplink resources in a second subframe, wherein the subset is mapped to the first subframe. One of the uplink resources is mapped to a plurality of CCEs in the first subframe. Limited resources for uplink feedback are efficiently used to support HARQ operation.

Wireless communication, complex automatic retransmission, HARQ, ACK / NACK

Description

How to perform HARV in wireless communication system {METHOD OF PERFORMING HYBRID AUTOMATIC REPEAT REQUEST (HARQ) IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to wireless communication, and more particularly, to a method of performing HARQ in a wireless communication system.

The next generation mobile communication system is not just a wireless communication service like the previous generation mobile communication system, but has been standardized for an efficient interworking and integration service between a wired communication network and a wireless communication network. As such, a high-speed mass communication system capable of processing and transmitting a variety of information such as video and wireless data beyond a voice-oriented service is required, thereby transmitting large-capacity data approaching the capacity of a wired communication network to a wireless communication network. There is a need for technology development. Therefore, an appropriate error detection method that can improve system performance by minimizing the reduction of information loss and increasing system transmission efficiency has become an essential element.

Examples of error handling methods include a forward error correction (FEC) method and an automatic repeat request (ARQ) method. In the FEC scheme, the receiver corrects an error from an extra information bit with an extra error correction code. In the ARQ scheme, if an error occurs in the received signal, the transmitter retransmits the data to correct the error. HARQ (Hybrid ARQ) method is a combination of the FEC method and ARQ method. According to the HARQ method, after checking whether there is an error in which data received at the physical layer is not decoded, if there is an error, a retransmission is requested to improve performance.

HARQ operation is performed by at least one HARQ entity (entity) included in the terminal or the base station. The HARQ entity allows for continuous data transmission while waiting for successful (ACK signal) or unsuccessful (NACK signal) feedback of previous data reception. In downlink transmission, the terminal receives resource allocation information from the base station, and the HARQ entity of the base station performs a HARQ process according to the HARQ information. To support the HARQ entity, the base station can operate a plurality of concurrent HARQ processes.

Hereinafter, downlink means communication from the base station to the terminal, and uplink means communication from the terminal to the base station. Downlink communication and HARQ operation may be performed as follows. The base station transmits downlink allocation to the terminal through a physical downlink control channel (PDCCH). In accordance with the downlink allocation, the terminal receives downlink data through a physical downlink shared channel (PDSCH). When the terminal receives downlink data from the base station, the terminal sends an ACK / NACK signal to the base station through a control channel (for example, a physical uplink control channel (PUCCH)). If there is no error in the received data, the ACK / NACK signal becomes an ACK signal. If an error is detected in the received data, the ACK / NACK signal becomes a NACK signal. When the base station receives the NACK signal, the base station retransmits data to the terminal. Hereinafter, downlink data may be referred to as a codeword or a transport block.

Resources such as frequency, time, code, and space must be distinguished between downlink transmission and uplink transmission, and therefore, the downlink resource and the uplink resource need not be duplicated. This is called duplexing. Duplexing can be divided into frequency division duplexing (FDD) in which uplink and downlink are divided into frequencies, and time division duplexing (TDD) in which uplink and downlink are separated by time.

In FDD, frequencies are assigned symmetrically to uplink and downlink. FDD is widely used because it is a structure suitable for symmetrical services (eg, voice calls). Recently, however, research is being actively conducted on asymmetric services (eg, Internet services) and suitable TTDs. In FDD, since uplink and downlink are distinguished in the frequency domain, seamless data transmission is possible between the base station and the terminal in the time domain.

TDD is suitable for asymmetric services because time slots having different ratios may be allocated to uplink and downlink. In addition, the uplink and the downlink are made in the same frequency band, so that the uplink and downlink channel states are almost the same. Therefore, the channel condition can be estimated immediately from the received signal. Thus, TDD is suitable for array antenna technology.

In TDD, the entire frequency band is used for uplink and downlink, and the uplink and downlink are distinguished in the time domain. Therefore, the frequency band is used as uplink at some time and downlink at other time, so that it is difficult to simultaneously transmit and receive data between the base station and the terminal. If uplink and downlink are selectively allocated for a certain period of time, the base station does not need to inform which time point is uplink transmission or downlink transmission.

In FDD as well as TDD, uplink resources are more limited than downlink resources. Uplink resources for uplink feedback for downlink data reception are not sufficient. For example, suppose that four resource blocks are used for downlink data and one resource block is used for uplink transmission. If the terminal receives data using four resource blocks from the base station, and transmits the ACK / NACK signal for the data through one resource block. The lack of uplink resources makes it difficult to perform HARQ, and the base station must determine through uplink feedback information lacking retransmission of new data or existing data.

There is a need for a method for efficiently performing HARQ using limited uplink resources for uplink feedback.

[Technical Challenges]

The present invention provides a method of performing HARQ in a wireless communication system. In addition, the uplink ACk / NACK resource allocation method associated with the CCE index for downlink allocation in the TDD mode as well as the FDD mode may provide efficient utilization of uplink PUCCH resources and commonality between the FDD and the TDD.

[Technical Solution]

In one aspect according to the present invention, a method for performing a hybrid automatic repeat request (HARQ) in a wireless communication system performed by a terminal is provided. The method receives a downlink allocation in a first subframe, wherein the downlink allocation is transmitted based on a control channel element (CCE) which is a logically indexed resource unit, and in the first subframe Receives downlink data on a downlink shared channel, the downlink shared channel is allocated according to the downlink allocation, and receives an ACK / NACK signal indicating successful or unsuccessful reception of the downlink data. Generating and transmitting the ACK / NACK signal or the representative ACK / NACK signal using a subset of uplink resources in a second subframe, wherein the subset is mapped to the first subframe. One of the uplink resources is mapped to a plurality of CCEs in the first subframe.

In another aspect according to the present invention, a method for transmitting an ACK / NACK signal in a wireless communication system performed by a terminal is provided. The method receives downlink data according to downlink allocation in a first subframe, wherein the downlink allocation is transmitted to a CCE, which is a logical resource unit, and indicates an successful or unsuccessful reception of the downlink data. Generating a / NACK signal, and transmitting the ACK / NACK signal using an uplink resource in a second subframe, wherein the second subframe is linked with the first subframe for HARQ operation; Uplink resources are mapped to a plurality of CCEs in the first subframe.

[Favorable effect]

The amount of reserved ACK / NACK resources may be set semi-statically. Limited resources for uplink feedback can be efficiently used to support HARQ operation.

1 shows a wireless communication system.

2 is an example of a radio frame structure.

3 is another example of a radio frame structure. This is a TDD radio frame structure.

4 is an example of a downlink subframe structure.

5 is an example of a structure of an uplink subframe.

6 illustrates an ACK / NACK resource grouping method according to an embodiment of the present invention.

7 illustrates a method of mapping CCEs to ACK / NACK resources according to an embodiment of the present invention.

8 illustrates a method of mapping a CCE to ACK / NACK resources according to another embodiment of the present invention.

9 illustrates a method of mapping CCEs to ACK / NACK resources according to another embodiment of the present invention.

10 is a flowchart illustrating ACK / NACK signal transmission according to an embodiment of the present invention.

The invention is described in more detail with reference to the following drawings, which illustrate exemplary embodiments. However, the present invention may be embodied in other forms and is not limited to the above-described embodiments. The following examples are provided to enable any person skilled in the art to fully practice the present invention. In the drawings, the thickness or area of a layer may be exaggerated for clarity. Like reference numerals refer to like elements.

1 shows a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice and packet data.

Referring to FIG. 1, a wireless communication system includes a base station 10 (BS) and a user equipment 20 (UE). The base station 10 generally refers to a fixed station that communicates with the terminal 20. In other terms, such as a Node-B, a Base Transceiver System (BTS), and an Access Point. Can be called. One or more cells may exist in one base station 10. The terminal 20 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device.

Hereinafter, downlink means communication from the base station 20 to the terminal 10, and uplink means communication from the terminal 10 to the base station 20. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20.

Multiple access schemes for downlink and uplink transmission may be different. For example, downlink may use Orthogonal Frequency Division Multiple Access (OFDMA) and uplink may use Single Carrier-Frequency Division Multiple Access (SC-FDMA).

There is no restriction on the multiple access method applied to the wireless communication system. Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Single-Carrier FDMA (SC-FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or other known modulation techniques. It can be based on the same multiple access techniques. These modulation techniques demodulate signals received from multiple users of a communication system to increase the capacity of the communication system.

The layers of the radio interface protocol between the terminal and the network are based on the lower three layers of the Open System Interconnection (OSI) model, which are well known in communication systems. It may be divided into a second layer L2 and a third layer L3. Among them, the physical layer belonging to the first layer provides an information transfer service using a physical channel, and is a radio resource control (RRC) layer located in the third layer. The role of controlling the radio resources between the terminal and the network. To this end, the RRC layer exchanges RRC messages between the UE and the network.

Examples of a downlink transport channel include a broadcast channel (BCH) used for transmitting system information and a downlink-shared channel (DL-SCH) used for transmitting traffic and control messages. User traffic or control messages of downlink multicast / broadcast may be transmitted on DL-SH or additional downlink multicast channel (DL-MCH). The downlink transport channel is mapped to a downlink physical channel. Examples of downlink physical channels include a physical downlink shared channel (PDSCH) mapped to a DL-SCH and a physical downlink control channel (PDCCH) used for transmission of a control signal.

Examples of an uplink transport channel include a physical downlink control channel (RACH) used for transmission of an initial control message, and an uplink-shared channel (UL-SCH) used for transmission of user traffic and control messages. The uplink transport channel is mapped to an uplink physical channel. Examples of an uplink physical channel include a physical random access channel (PRACH) mapped to a RACH, a physical uplink shared channel (PUSCH) mapped to a UL-SCH, and a physical uplink control channel (PUCCH) used to transmit an uplink control signal. . The PUSCH is used when the terminal transmits data in uplink.

The PDCCH transmits control information for the PUSCH or PDSCH. An uplink grant, which is scheduling information for uplink data transmission, and a downlink grant, which is scheduling information for downlink data transmission, are transmitted through a PDCCH. Hereinafter, the scheduling information includes radio resource allocation for transmitting downlink data to the terminal by the base station, radio resource allocation for receiving uplink data from the terminal, modulation and coding scheme (MCS), MIMO information, and the like.

2 is an example of a radio frame structure.

Referring to FIG. 2, a radio frame may consist of 10 subframes, and one subframe may include two slots. The basic unit of data transmission is a subframe unit, and downlink or uplink scheduling is performed on a subframe basis. One slot may include a plurality of OFDM symbols in the time domain and at least one subcarrier in the frequency domain. One slot may include 7 or 6 OFDM symbols.

The structure of a radio frame is merely an example. The number of subframes belonging to the radio frame, the number of slots belonging to the subframe, the number of OFDM symbols in the slot and the number of subcarriers may be variously changed.

3 is another example of a radio frame structure. This is a TDD radio frame structure.

Referring to FIG. 3, a radio frame includes two half-frames. Each half frame has the same structure. The half frame includes five subframes and three fields Downlink Pilot Time Slot (DwPTS), Guard Period, and Uplink Pilot Time Slot (UpPTS). DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. The guard period is a period for removing interference generated in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

4 is an example of a downlink subframe structure.

Referring to FIG. 4, up to three OFDM symbols in the first slot of a downlink subframe are control regions to which a PDCCH is allocated, and the remaining OFDM symbols are data regions to which a PDSCH is allocated. In addition to the PDCCH, the control region may be allocated a control channel such as a physical control format indicator channel (PCFICH) and a physical HARQ indicator channel (PHICH). The number of OFDM symbols included in the control region in the subframe can be known through the PCFICH. The UE may read data transmitted on the PDSCH through control information transmitted on the PDCCH. Here, it is merely an example that the control region includes 3 OFDM symbols.

The control region is composed of a set of CCEs which are a plurality of control channel elements (CCEs). Hereinafter, the CCE set is a set of a plurality of CCEs constituting the control region in one subframe. The CCE corresponds to a plurality of resource element groups. For example, the CCE may correspond to 9 resource element groups. Resource element groups are used to define the mapping of control channels to resource elements.

A plurality of multiplexed PDCCHs for a plurality of terminals may be transmitted in a control region. The PDCCH carries control information such as scheduling assignment. The PDCCH is transmitted on an aggregation of one CCE-based or several consecutive CCEs (control channel elements). The format of the PDCCH and the number of available bits are determined based on the number of CCEs in the CCE set. Hereinafter, the number of CCEs used for PDCCH transmission is referred to as a CCE aggregation level. The size of the CCE aggregation level is defined by the number of adjacent CCEs. For example, the CCE aggregation level may be an element of {1, 2, 4, 8}.

Table 1 shows the format of the PDCCH according to the CCE aggregation level and the number of available bits.

PDCCH format CCE aggregation level Number of resource element groups Number of PDCCH bits 0 One 9 72 One 2 18 144 2 4 36 288 3 8 72 576

Each UE may have a different CCE aggregation level. For example, the CCE aggregation level (L) is 1 for the second, fourth, and sixth terminals UE 2, UE4, and UE 6, and 2 for the third and fifth terminals UE 3, UE 5. 4 for the first and seventh terminals UE 1 and UE 7.

Control information on the PDCCH is called downlink control information (DCI). The DCI includes uplink scheduling information, downlink scheduling information, an uplink power control command, a paging control command, and an indicator for an RACH response. DCI format 0 is used for PUSCH scheduling, DCI format 1 is used for PDSCH codeword scheduling, DCI format 1A is used for simple PDSCH codeword scheduling, DCI format 1C is used for simple DL-SCH scheduling, and DCI format 2 is closed loop. It is used for PDSCH codeword scheduling in closed-loop spatial multiplexing mode, DCI format 2A is used for PDSCH codeword scheduling in open-loop spatial multiplexing mode, and DCI formats 3 and 3A are used for transmission power control of uplink channels. Used.

5 is an example of a structure of an uplink subframe.

Referring to FIG. 5, an uplink subframe may be divided into a control region and a data region. The control region includes a PUCCH and the data region includes a PUSCH. In order to satisfy the single carrier characteristics by applying SC-FDMA, the UE may not simultaneously transmit the PUCCH and the PUSCH.

PUCCH for one UE is allocated as a resource block pair (RB pair) in a subframe, and RBs belonging to the RB pair occupy different subcarriers in each of two slots. This is said that the RB pair allocated to the PUCCH is frequency hopping at the slot boundary.

PUCCH may support multiple formats. That is, uplink control information having different numbers of bits per subframe may be transmitted according to a modulation scheme.

The following table shows the PUCCH format, modulation scheme, and number of bits supported according to 3GPP TS 36.211 V8.2.0.

PUCCH format 1 is used for transmitting a scheduling request (SR), PUCCH format 1a / 1b is used for transmitting an ACK / NACK signal, PUCCH format 2 is used for transmitting channel quality information (CQI), and PUCCH format 2a / 2b is used for transmitting a scheduling request. It is used for transmission of CQI and ACK / NACK signals.

When an ACK / NACK signal is transmitted alone in any subframe, PUCCH format 1a / 1b is used, and when an SR is transmitted alone, PUCCH format 1 is used. If the ACK / NACK signal and the SR are to be transmitted simultaneously, the SR resource allocated for the SR transmission is used for the transmission of the ACK / NACK signal and the positive SR, and the ACK / NACK resource allocated to the ACK / NACK signal is the ACK / NACK signal. And negative SR transmission.

Table 3 shows an example of downlink / uplink configuration of a radio frame in a TDD system. The configuration of a radio frame is a rule indicating which rule is allocated (or reserved) for uplink and downlink.

Configuration Switch-point periodicity Subframe number 0 One 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U One 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6 5 ms D S U U U D S U U D

In Table 3, 'D' indicates that the subframe is used for downlink transmission, 'U' indicates that the subframe is used for uplink transmission. 'S' indicates that the subframe is used for a special purpose and is used for frame synchronization or downlink transmission. Hereinafter, a subframe used for downlink transmission is simply called a downlink subframe, and a subframe used for uplink transmission is simply called an uplink subframe. Each configuration has a different position and number of downlink subframes and uplink subframes in one radio frame.

The point of time from the downlink to the uplink or the time from the uplink to the downlink is called a switching point. The switch-point periodicity means a period in which an uplink subframe and a downlink subframe are repeatedly switched in the same manner, and are 5 ms or 10 ms. For example, in configuration 0, D-> S-> U-> U-> U is switched from 0th to 4th subframe, and D-> S is the same as before from 5th to 9th subframe. Switch to-> U-> U-> U. Since one subframe is 1ms, the periodicity at the switching time is 5ms. That is, the periodicity of the switching time is less than one radio frame length (10ms), and the switching mode in the radio frame is repeated once.

In all configurations, the 0th, 5th subframe, and DwPTS are used for downlink transmission. The first subframe of all settings and the sixth subframe of settings 0, 1, 2, and 6 consist of DwPTS, guard period, and UpPTS. The length of time for each field depends on the setting. The remaining eight subframes, except for the first and sixth subframes, consist of two slots.

If the period of switching time is every 5ms, UpPTS and the 2nd and 7th subframes are reserved for uplink transmission. On the other hand, when the switching period is every 10 ms, UpPTS and the second subframe are reserved for uplink transmission, and DwPTS, the seventh and ninth subframe are reserved for downlink transmission.

The configuration of Table 3 may be known as system information that both the base station and the terminal know. The base station may inform the terminal of the change of the uplink-downlink assignment state of the radio frame by transmitting only the index of the configuration information whenever the configuration information of the radio frame changes. The configuration information is a kind of downlink control information and may be transmitted through a physical downlink control channel (PDCCH) which is a downlink control channel like other scheduling information. Alternatively, the configuration information may be control information that is commonly transmitted to all terminals in a cell through a broadcast channel as broadcast information. Alternatively, the configuration information may be information included in system information. In the TDD system, the number of half frames included in the radio frame, the number of subframes included in the half frame, and the combination of the downlink subframe and the uplink subframe are merely examples.

In the HARQ operation, the UE receives downlink data in a downlink subframe and transmits an ACK / NACK signal as feedback in the uplink subframe. This may be a problem when there are more downlink subframes than uplink subframes in the radio frame. In Table 3, 'S' is a downlink subframe. In configuration 2, the radio frame has a downlink subframe to uplink subframe ratio of 4: 1. In this case, the UE feeds back a plurality of ACK / NACK signals through one uplink subframe for HARQ operation with respect to the data coming through the four downlink subframes. When there are more downlink subframes than uplink subframes, radio resources for transmitting ACK / NACK signals may be insufficient.

The linkage between the downlink subframe and the uplink subframe for the uplink ACK / NACK feedback needs to be defined for each downlink / uplink configuration of Table 3. The uplink subframe carries ACK / NACK signals for multiple downlink subframes depending on the downlink / uplink configuration. A predefined relationship between the downlink subframe and the uplink subframe is described below to prevent excessive uplink ACK / NACK resource reservation. The amount of reserved ACK / NACK resources may be semi-statically set such that the number of ACK / NACK resources is smaller than the number of CCEs in the corresponding downlink subframe.

Semi-static DL / UL linkage in the configuration of Table 3 is shown in Table 4.

In Table 4, the special downlink subframe (indicated by 'S' in Table 3) is used as the downlink subframe, so it is indicated as 'D' to prevent confusion. The ACK / NACK signal corresponding to the downlink subframe D # n is transmitted in the uplink subframe U # n. For example, the downlink subframe D1 of the i th radio frame corresponds to the uplink subframe U1 of the i + 1 th radio frame. Although there are subframes without #n among D or U, they may also be linked with other subframes for ACK / NACK signal feedback.

In most configurations, all or some uplink subframes are linked with a plurality of downlink subframes. That is, one uplink subframe is associated with at least one downlink subframe. In configuration 0, there is a 4: 1 downlink subframe-uplink subframe correspondence, and two uplink subframes are not linked with another downlink subframe. In configuration 1, there is a 2: 1 downlink subframe-uplink subframe correspondence and two 1: 1 downlink subframe-to-uplink subframe correspondences. In configuration 2, there are two 4: 1 downlink subframe-to-uplink subframe correspondences. In configuration 3, there are two 2: 1 downlink subframe-uplink subframe correspondences and one 3: 1 downlink subframe-to-uplink subframe correspondence. In the remaining configuration, it is easy to know the correspondence between the downlink subframe and the uplink subframe.

Hereinafter, an uplink radio resource used for transmission of an ACK / NACK signal is called an ACK / NACK resource. The ACK / NACK resource may be a combination of an RB, a cyclic shift, and an orthogonal cover. The ACK / NACK resource may be allocated according to uplink scheduling information such as an uplink grant. A subset including at least one ACK / NACK resource is called an ACK / NACK resource subset. The uplink subframe may include a plurality of ACK / NACK resource subsets. The number of ACK / NACK resources in each ACK / NACK resource subset may vary.

In configurations 0, 1 and 3, respectively, two different downlink subframe-to-uplink subframe correspondences exist in one radio frame for ACK / NACK feedback. In this case, the amount of ACK / NACK resources in the ACK / NACK resource subset may be adjusted according to the uplink subframe so as to have the same amount of ACK / NACK resources in all uplink subframes. Alternatively, the amount of ACK / NACK resources in all ACK / NACK resource subsets may be similar or the same by different ACK / NACK resources according to an uplink subframe.

Correspondence between the downlink subframe and the uplink subframe for ACK / NACK signal feedback according to each configuration in the radio frame is as described above. Hereinafter, a method of configuring an ACK / NACK resource subset in an uplink subframe will be described. This method efficiently groups or divides CK / NACK resources when it is difficult to provide enough ACK / NACK resources for all downlink data in AHARQ operation. This method can be applied to the FDD system as well as the TDD system.

6 illustrates an ACK / NACK resource grouping method according to an embodiment of the present invention.

Referring to FIG. 6, 3: 1 downlink subframe-uplink subframe correspondence is used in a radio frame configuration for HARQ operation. Three downlink subframes are indexed as i, (i + 1) and (i + 2), respectively, and the uplink subframes are indexed as j (j> i + 2). This means that the jth uplink subframe carries ACK / NACK signals corresponding to three downlink subframes. The ACK / NACK resources are divided into three ACK / NACK resource matches, and each subset is used for an ACK / NACK signal corresponding to one of three downlink subframes.

In general, when an uplink subframe is linked with L downlink subframes for ACK / NACK feedback, ACK / NACK resources are divided into L subsets in the uplink subframe. The number of ACK / NACK resource subsets in the uplink subframe is determined according to the number of downlink subframes linked with the uplink subframe.

Each subset contains the same or different amounts of ACK / NACK resources. Each subset includes the same number of ACK / NACK resources M. The uplink subframes together include L × M ACK / NACK resources. ACK / NACK resource subset 1, 2, .., L are 0 to M-1 ACK / NACK resources, M to 2M-1 ACK / NACK resources, ..., (L-1) × M to ( L × M) −1 each has ACK / NACK resources.

M ACK / NACK resources in each subset are mapped to one N CCEs of L downlink subframes. The CCE of the i th subframe is mapped to 0-1 M-1 ACK / NACK resources. The CCE of the i + 1th subframe is mapped to M to 2M-1 ACK / NACK resources. The CCE of the i + 2th subframe is mapped to 2M to 3M-1 ACK / NACK resources. The number of CCEs in each downlink subframe may be the same or different. The M value may be set to be less than or equal to N. Since the actual number of CCEs may be different for each downlink subframe, N may be a maximum number of CCEs in the downlink subframe.

In summary, when an uplink subframe carries an ACK / NACK signal for multiple downlink subframes, the ACK / NACK resources are divided into a plurality of subsets so that each subset of ACK / NACK resources is linked to the downlink subframe. .

A method of dividing ACK / NACK resources into a plurality of subsets is as follows.

Here, the CCE group is composed of a plurality of CCEs in one subframe, and N _CCE (j) is the number of (maximum) CCEs for the j th CCE group. If N _CCE (j) is set equal to the number of maximum CCEs for all subframes, it may be replaced with N _CCE . N _g is the number of CCE groups in the PUCCH. If the maximum number of CCEs for all subframes is set to be the same, N ^G _CCE is equal to N _g × N _CCE .

In the following, a mapping method between ACK / NACK resources and CCE is described. The ACK / NACK resources in the subset are remapped to other CCEs so that the number of ACK / NACK resources in the subset is smaller than the number of CCEs in the downlink subframe. As a result, the amount of reserved ACK / NACK resources is set semi-statically. This configuration and remapping scheme can also be applied to the FDD mode.

7 illustrates a method of mapping CCEs to ACK / NACK resources according to an embodiment of the present invention. M ACK / NACK resources in the subset are indexed from 0 to M-1, and N CCEs in the downlink subframe are indexed from 0 to N-1. The order of the CCE indexes may be virtually interleaved within each PUCCH resource block.

Referring to FIG. 7, seven CCEs from CCE indexes 'a' to 'g' and five ACK / NACK resources from indexes 0 to 4 are used to transmit ACK / NACK signals corresponding to the PDCCH. Since N> M, the same ACK / NACK resource is remapped to CCE. That is, a plurality of CCEs are mapped to ACK / NACK resources. 'b' and 'c' CCE is mapped to ACK / NACK resource 0, 'd' and 'e' CCE is mapped to ACK / NACK resource 1. However, 'a', 'f' and 'g' CCEs are mapped to ACK / NACK resources 3, 2 and 4, respectively.

Repeated CCE-to-ACK / NACK mapping may allow a base station to restrict PDCCH scheduling so that the same ACK / NACK resource is not associated with multiple PDSCH transmissions in a downlink subframe. However, it reduces the amount of uplink ACK / NACK resources required. In general, ACK / NACK indexes can be mapped to multiple CCE indexes even when L = 1. One uplink subframe corresponds to one downlink subframe. This is because there is no reason to prohibit the same mapping scheme to be applied. This mapping scheme can be applied to FDD mode for efficient PUCCH resource utilization and commonality between FDD and TDD.

8 illustrates a method of mapping a CCE to ACK / NACK resources according to another embodiment of the present invention. Assume three resource blocks, 12 ACK / NACK resources per resource block, and 18 CCEs per downlink subframe for an extended CP, ACK / NACK signal.

Referring to FIG. 8, CCEs are indexed from 0 to 17 in subframe x, and CCEs are indexed from 0 to 17 in subframe y. When the terminal receives the CCE in the subframes x and y, the terminal converts the index of the CCE in the subframe y. As a result, the index of the CCE in the subframe y is converted from 18 to 35. In the subframe x, the index of the CCE is maintained. In subframes x and y, the entire CCE is indexed from 0 to 35. In this way, the CCE indexes of multiple subframes may be contiguous. The converted CCE index may be mapped directly or mixed per resource block to the ACK / NACK index.

When the number of ACK / NACK resources in the subset is smaller than the number of CCEs in the downlink subframe corresponding to the subset, some ACK / NACK resources need to be remapped to other ACK / NACK resources. In this case, ACK / NACK resources in the subset are remapped to CCEs in the corresponding downlink subframe. This remapping can be done by converting a range of CCE indexes that are mapped to ACK / NACK resource subsets in the downlink subframe. Accordingly, the same converted CCE index may be allocated to other CCEs in the downlink subframe.

9 illustrates a method of mapping CCEs to ACK / NACK resources according to another embodiment of the present invention. Assume three resource blocks, 12 ACK / NACK resources per resource block, and 31 CCEs per downlink subframe for an extended CP, ACK / NACK signal.

Referring to FIG. 9, subframes x and y are mapped to feedback subframes having ACK / NACK resources for subframes x and y. The feedback subframe is used to transmit ACK / NACK signals for the subframes x and y. Since the feedback subframe is linked with two subframes, ACK / NACK resources are divided into two subsets in the feedback subframe.

Subset 1 containing ACK / NACK resources with indices from 0 to 17 is mapped to subframe x. Subset 2 containing ACK / NACK resources with indices from 18 to 35 is mapped to subframe y.

The number of CCEs in each subframe is larger than the number of ACK / NACK resources included in the corresponding subset. Some ACK / NACK resources in subset 1 are remapped to CCE with indices from 18 to 30 in subframe x. Some ACK / NACK resources in subset 2 are remapped to CCE with indices from 0 to 12 in subframe y.

Before remapping the ACK / NACK resource to the CCE, the index of the extra CCE may be converted to another index. A CCE with an index converted for remapping is called an extra CCE, and a CCE with an index that is not converted is called a regular CCE. For example, an index of an extra CCE having indices 18 to 30 in subframe x is converted into existing 0 to 12. The index of the extra CCE having indices 0 to 17 in subframe y is converted from 18 to 35.

The index of the extra CCE having an index converted from 0 to 12 is duplicated with the index of the regular CCE in subframe x. The index of the extra CCE having the index converted from 18 to 30 is duplicated with the index of the regular CCE in subframe y.

ACK / NACK resources with indices 0 through 12 in subset 1 are mapped to extra CCEs with transformed indexes and regular CCEs with indices 0-12. That is, remapping occurs. ACK / NACK resources with indices 13 through 17 in subset 1 are mapped to regular CCEs with indices 13 through 17.

The same remapping process is applied to subframe y and subset 2.

10 is a flowchart illustrating ACK / NACK signal transmission according to an embodiment of the present invention.

Referring to FIG. 10, downlink allocation is received (S100). Downlink allocation is also referred to as downlink scheduling information or downlink grant. Downlink allocation is received in a first subframe that includes downlink data. The downlink allocation is transmitted based on the CCE. The CCE is a resource unit logically indexed to the control region of the first subframe. Downlink allocation is transmitted on a downlink control channel, which is a PDDCH. The first subframe may be a downlink subframe or a plurality of downlink subframes in the TDD system.

Downlink data is received on a downlink shared channel in the first subframe (S110). The downlink shared channel is allocated according to the downlink allocation. The downlink shared channel is PDSCH.

An ACK / NACK signal is generated (S120). An ACK / NACK signal indicates successful or unsuccessful reception of the downlink data.

In the second subframe, the ACK / NACK signal or the representative ACK / NACK signal is transmitted using a subset of uplink resources (which are mapped to CCEs carrying downlink allocation) (S130). The subset is mapped to the first subframe, and one of the uplink resources is mapped to a plurality of CCEs in the first subframe. The second subframe may be an uplink subframe in the TDD system.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

Claims (13)

In a method of performing a hybrid automatic repeat request (HARQ) in a terminal in a time-division-duplex (TDD) mobile communication system, Receiving a first downlink assignment on a first control channel in a first downlink subframe, Receiving a second downlink allocation on a second control channel in a second downlink subframe, Receiving first downlink data in the first downlink subframe using a radio resource identified by the first downlink allocation, Receiving second downlink data in the second downlink subframe using a radio resource identified by the second downlink allocation, Determine an ACK / NACK resource in an uplink subframe, wherein the ACK / NACK resource is determined based on the number of a plurality of link downlink subframes linked for the HARQ feedback with the uplink subframe, and the plurality of links A downlink subframe includes the first downlink subframe and the second downlink subframe, wherein the plurality of link downlink subframes for the uplink subframe are predefined; and And transmitting ACK / NACK signals for the first downlink data and the second downlink data using the ACK / NACK resources in the uplink subframe. The method of claim 1, wherein the ACK / NACK support is determined based on the number of resource units used for transmission of the second control channel and the plurality of link downlink subframes linked with the uplink subframe. The method of claim 2, wherein the first control channel and the second control channel are physical downlink control channels (PDCCHs), and the resource unit is a control channel element (CCE). 2. The method of claim 1, wherein the second downlink subframe includes a control region and a data region in a time domain, the second control channel is transmitted in the control region, and the second downlink data is transmitted in the data region. How sent. The method of claim 1, wherein the plurality of link downlink subframes includes the first downlink subframe, the second downlink subframe, and at least one downlink subframe. In the TDD mobile communication system, a terminal confirms reception of downlink data, Receive downlink allocation on the control channel in the downlink subframe, Receiving downlink data in the downlink subframe using a radio resource identified by the downlink allocation, Determine an ACK / NACK resource in an uplink subframe, wherein the ACK / NACK resource is one of the number of at least one link downlink subframe linked with the uplink subframe and one of the link downlink subframes for HARQ feedback Determined based on a resource unit used for transmission of a control channel for the at least one link downlink subframe includes the downlink subframe, and And transmitting the ACK / NACK signal for the downlink data using the ACK / NACK resource in the uplink subframe. The radio frame of claim 6, wherein the radio frame includes a plurality of downlink subframes and the uplink subframe, wherein the uplink subframe includes at least one downlink subframe defined in or in a previous radio frame. How to be linked. 8. The method of claim 7, wherein an association for HARQ feedback between the uplink subframe and the link downlink subframe is predefined according to a downlink / uplink configuration of the TDD mobile communication system. The method of claim 6, wherein the control channel is a physical downlink control channel (PDCCH) and the resource unit is a control channel element (CCE). 7. The method of claim 6, wherein the ACK / NACK signal is a representative ACK / NACK signal for a plurality of link downlink subframes. The method of claim 6, wherein the downlink subframe includes a control region and a data region in a time domain, the control channel is transmitted in the control region, and the downlink data is transmitted in the data region. In a terminal in which a terminal confirms reception of downlink data in a TDD mobile communication system, the terminal Receive downlink allocation on the control channel in the downlink subframe, Receiving downlink data in the downlink subframe using a radio resource identified by the downlink allocation, Determine an ACK / NACK resource in an uplink subframe, wherein the ACK / NACK resource is one of the number of at least one link downlink subframe linked with the uplink subframe and one of the link downlink subframes for HARQ feedback Determined based on a resource unit used for transmission of a control channel for the at least one link downlink subframe includes the downlink subframe, and And a terminal configured to transmit an ACK / NACK signal for the downlink data using the ACK / NACK resource in the uplink subframe. 13. The method of claim 12, wherein the radio frame includes a plurality of downlink subframes and the uplink subframe, wherein the uplink subframe includes at least one downlink subframe defined in or in a previous radio frame. Terminal to be linked.

Images