WO2011122825A2 - Method for setting a carrier indication field in a multi-carrier system - Google Patents

Abstract

Disclosed is a method for setting a carrier indication field indicating an element carrier in a multi-carrier system using a plurality of element carriers. The method includes: transmitting a value of a carrier indication field (CIF) and first CIF setting information that indicates a first mapping relationship between element carriers; transmitting downlink control information (DCI) including a carrier indication field; and transmitting a value of a CIF and second CIF setting information that indicates a second mapping relationship between element carriers, wherein the carrier indication field is a field indicating any one of the plurality of element carriers, and at least one element carrier is mapped with the same carrier indication field value in the first and second mapping relationships.

Description

How to Set Carrier Indication Fields in a Multicarrier System

The present invention relates to wireless communication, and more particularly, to a method of setting a carrier indication field in a multi-carrier system.

One of the most important requirements of the next generation wireless communication system is that it can support high data rate requirements. To this end, various technologies such as Multiple Input Multiple Output (MIMO), Cooperative Multiple Point Transmission (CoMP), and relay are being studied, but the most basic and stable solution is to increase the bandwidth.

However, frequency resources are saturated at present, and various technologies are partially used in a wide range of frequency bands. For this reason, in order to secure broadband bandwidth in order to meet higher data rate requirements, each scattered band is designed to satisfy the basic requirements for operating an independent system, and multiple bands are combined in one system. Carrier aggregation (CA) is introduced, which is a concept of grouping together. In this case, each independent operating band is defined as a component carrier (CC).

In order to support the increasing transmission capacity, recent communication standards such as 3GPP LTE-A or 802.16m, etc. continue to expand their bandwidth to 20 MHz or more. In this case, one or more component carriers are aggregated to support broadband. For example, if one component carrier corresponds to a bandwidth of 5 MHz, four carriers are aggregated to support a bandwidth of up to 20 MHz. As such, the carrier aggregation system uses a plurality of component carriers, and in this sense, it may be called a multi-carrier system.

In the multi-carrier system, the component carrier allocated to the terminal may be changed for various reasons such as a channel environment or an amount of data transmitted. For example, two component carriers may be allocated to a terminal to perform communication, and one component carrier may be added to allocate three component carriers. Alternatively, three component carriers may be allocated to perform communication, and one component carrier may be removed to allocate only two component carriers. As such, when the component carrier allocated to the terminal is changed, the mapping between the value of the carrier indication field indicating the component carrier and the component carrier may also be changed. In this case, it is necessary to clearly define how to map the value of the carrier indication field and the component carrier.

An object of the present invention is to provide a carrier indication field setting method for indicating a component carrier in a multi-carrier system.

In a multi-carrier system according to an aspect of the present invention, the method for setting a carrier indication field for indicating a component carrier includes first CIF configuration information indicating a first mapping relationship between a value of a carrier indication field (CIF) and a component carrier; Transmitting; Transmitting downlink control information (DCI) including a carrier indication field; And transmitting second CIF setting information indicating a value of a carrier indication field and a second mapping relationship between component carriers, wherein the carrier indication field is a field indicating one component carrier among the plurality of component carriers. At least one CC is mapped to the same carrier indication field value in the first mapping relationship and the second mapping relationship.

The first CIF configuration information and the second CIF configuration information may be transmitted through the at least one CC.

The downlink control information may be transmitted through the at least one component carrier.

The carrier indication field may have a 3-bit size.

The first mapping information and the second mapping information may be included in a radio resource control (RRC) message and transmitted.

If there is a component carrier added based on the component carriers mapped in the first mapping relationship among the component carriers mapped in the second mapping relationship, the added component carrier has a minimum value of a usable carrier indication field or The maximum value can be mapped.

If there is a component carrier removed based on component carriers mapped in the first mapping relationship among the component carriers mapped in the second mapping relationship, the component removed from the component carriers mapped in the second mapping relationship The value of the carrier indication field mapped to the remaining component carriers other than the carrier is kept the same as the first mapping relationship.

Carrier indication field usable for the added component carrier when there is a component carrier added and removed component carriers based on the component carriers mapped in the first mapping relationship among the component carriers mapped in the second mapping relationship The minimum or maximum value of may be mapped first.

According to the present invention, even if a component carrier allocated to a terminal is changed in a multi-carrier system, data and control signals can be transmitted between the terminal and the base station without error.

1 illustrates an example of a wireless communication system in which the present invention may be implemented.

2 shows a structure of a radio frame in 3GPP LTE.

3 shows an example of a resource grid for one downlink slot.

4 shows a structure of a downlink subframe.

5 shows a structure of an uplink subframe.

6 is an example of a base station and a terminal constituting a carrier aggregation system.

7 and 8 illustrate another example of a base station and a terminal constituting a carrier aggregation system.

9 is an example of a DL / UL asymmetric carrier aggregation system to which the present invention can be applied.

10 shows an example of the DCI format.

11 illustrates a case where there is no link relationship between the monitoring DL CC and the scheduled DL CC.

12 illustrates a case where there is a link relationship between the monitoring DL CC and the scheduled DL CC.

13 illustrates logical indexing of CIF values for a plurality of CCs.

14 shows an example of a process of changing a CIF setting between a base station and a terminal.

15 to 19 show examples of setting CC and CIF values.

20 is a block diagram illustrating a base station and a terminal.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various wireless communication systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA), or the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of Evolved UMTS (E-UMTS) using Evolved-UMTS Terrestrial Radio Access (E-UTRA), which employs OFDMA in downlink and SC in uplink -FDMA is adopted. LTE-A (Advanced) is an evolution of 3GPP LTE.

For clarity, the description will be given on the assumption that it is applied to the LTE-A system, but the technical spirit of the present invention is not limited thereto.

1 illustrates an example of a wireless communication system in which the present invention may be implemented.

The wireless communication system 10 includes at least one base station (BS) 11. Each base station 11 provides a communication service for a particular geographic area (generally called a cell) 15a, 15b, 15c. The cell can in turn be divided into a number of regions (called sectors). The UE 12 may be fixed or mobile, and may include a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a PDA. (Personal Digital Assistant), a wireless modem (wireless modem), a handheld device (handheld device) may be called other terms. The base station 11 generally refers to a fixed station communicating with the terminal 12, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like. have.

A terminal typically belongs to one cell, and a cell to which the terminal belongs is called a serving cell. A base station that provides a communication service for a serving cell is called a serving BS. The wireless communication system may be a cellular system and there may be other cells adjacent to the serving cell. Another cell adjacent to the serving cell is called a neighbor cell. A base station that provides communication service for a neighbor cell is called a neighbor BS. The serving cell and the neighbor cell are relatively determined based on the terminal.

In general, downlink means communication from the base station 11 to the terminal 12, and uplink means communication from the terminal 12 to the base station 11.

The wireless communication system may be any one of a multiple-in multiple-out (MIMO) system, a multiple input single output (MIS) system, a single input single output (SISO) system, and a single input multiple output (SIMO) system. The MIMO system uses a plurality of transmit antennas and a plurality of receive antennas. The MISO system uses multiple transmit antennas and one receive antenna. The SISO system uses one transmit antenna and one receive antenna. The SIMO system uses one transmit antenna and multiple receive antennas.

A transmit antenna means a physical or logical antenna used to transmit one signal or stream, and a receive antenna means a physical or logical antenna used to receive one signal or stream.

2 shows a structure of a radio frame in 3GPP LTE.

This is described in Section 5 of 3rd Generation Partnership Project (3GPP) TS 36.211 V8.2.0 (2008-03) "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation (Release 8)". Reference may be made. Referring to FIG. 2, a radio frame consists of 10 subframes, and one subframe consists of two slots. Slots in a radio frame are numbered with slots # 0 through # 19. The time taken for one subframe to be transmitted is called a Transmission Time Interval (TTI). TTI may be referred to as a scheduling unit for data transmission. For example, one radio frame may have a length of 10 ms, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

One slot includes a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in the time domain and a plurality of subcarriers in the frequency domain. The OFDM symbol is for representing one symbol period. The OFDM symbol may be called another name. For example, an Orthogonal Frequency Division Multiple Access (OFDMA) symbol or a single carrier-frequency division multiple access (SC-FDMA) is used as an uplink multiple access scheme and may be referred to as an SC-FDMA symbol.

3GPP LTE defines that one slot includes 7 OFDM symbols in a normal cyclic prefix (CP), and one slot includes 6 OFDM symbols in an extended CP. .

The structure of the radio frame is merely an example. Accordingly, the number of subframes included in the radio frame, the number of slots included in the subframe, or the number of OFDM symbols included in the slot may be variously changed.

3 shows an example of a resource grid for one downlink slot.

The downlink slot includes a plurality of OFDM symbols in the time domain and includes N _RB resource blocks (RBs) in the frequency domain. The RB includes one slot in the time domain and a plurality of consecutive subcarriers in the frequency domain in resource allocation units.

The number N _RB of resource blocks included in the downlink slot depends on a downlink transmission bandwidth set in a cell. For example, in the LTE system, N _RB may be any one of 60 to 110. The structure of the uplink slot may also be the same as that of the downlink slot.

Each element on the resource grid is called a resource element (RE). Resource elements on the resource grid may be identified by an index pair (k, l) in the slot. Where k (k = 0, ..., N _RB × 12-1) is the subcarrier index in the frequency domain, and l (l = 0, ..., 6) is the OFDM symbol index in the time domain.

One resource block includes 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain to include 7 × 12 resource elements, but the number of OFDM symbols and the number of subcarriers in the resource block is limited thereto. It is not. The number of OFDM symbols and the number of subcarriers can be variously changed according to the length of the CP, frequency spacing, and the like. For example, the number of OFDM symbols is 7 for a normal CP and the number of OFDM symbols is 6 for an extended CP. The number of subcarriers in one OFDM symbol may be selected and used among 128, 256, 512, 1024, 1536 and 2048.

4 shows a structure of a downlink subframe.

The downlink subframe includes two slots in the time domain, and each slot includes seven OFDM symbols in the normal CP. The leading up to 3 OFDM symbols (up to 4 OFDM symbols for 1.4Mhz bandwidth) of the first slot in the subframe are the control regions to which control channels are allocated, and the remaining OFDM symbols are the PDSCH (Physical Downlink Shared Channel). Becomes the data area to be allocated. The PDSCH refers to a channel through which the base station transmits data to the terminal.

The physical control format indicator channel (PCFICH), the physical hybrid ARQ indicator channel (PHICH), and the physical downlink control channel (PDCCH) may be transmitted to the control region. The PCFICH is a physical channel for transmitting a format indicator indicating a format of a PDCCH, that is, a number of OFDM symbols constituting the PDCCH, to be included in every subframe. The format indicator may be called a control format indicator (CFI).

The PHICH carries HARQ ACK / NACK signals in response to uplink transmission.

The PDCCH includes resource allocation of downlink-shared channel (DL-SCH) (also referred to as downlink grant) and transmission format, resource allocation information of uplink shared channel (UL-SCH) (also referred to as uplink grant). Paging information on paging channel (PCH), system information on DL-SCH, resource allocation of higher layer control messages such as random access response transmitted on PDSCH, transmission power control for individual UEs in any UE group a set of transmission power control (TPC) commands and activation of Voice over Internet Protocol (VoIP). Control information transmitted through the PDCCH as described above is called downlink control information (DCI).

The control region in the subframe includes a plurality of control channel elements (CCEs). The CCE is a logical allocation unit used to provide a coding rate according to the state of a radio channel to a PDCCH and corresponds to a plurality of resource element groups (REGs). The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

One REG includes four REs and one CCE includes nine REGs. {1, 2, 4, 8} CCEs may be used to configure one PDCCH, and each element of {1, 2, 4, 8} is called a CCE aggregation level.

A control channel composed of one or more CCEs performs interleaving in units of REGs and is mapped to physical resources after a cyclic shift based on a cell ID.

In 3GPP LTE, blind decoding is used to detect the PDCCH. Blind decoding is a method of demasking a desired identifier in a CRC of a received PDCCH (which is called a candidatetae PDCCH) and checking a CRC error to determine whether the corresponding PDCCH is its control channel. The UE does not know where its PDCCH is transmitted using which CCE aggregation level or DCI format at which position in the control region.

A plurality of PDCCHs may be transmitted in one subframe. The UE monitors the plurality of PDCCHs in every subframe. In this case, the monitoring means that the UE attempts to decode the PDCCH according to the monitored PDCCH format.

In 3GPP LTE, a search space is used to reduce the burden of blind decoding. The search space may be referred to as a monitoring set of the CCE for the PDCCH. The UE monitors the PDCCH in the corresponding search space.

The search space is divided into a common search space and a UE-specific search space. The common search space is a space for searching for a PDCCH having common control information. The common search space may be configured with 16 CCEs up to CCE indexes 0 to 15, and supports a PDCCH having a CCE aggregation level of {4, 8}. However, PDCCHs (DCI formats 0 and 1A) carrying UE specific information may also be transmitted in the common search space. The UE-specific search space supports a PDCCH having a CCE aggregation level of {1, 2, 4, 8}.

Existing DCI formats transmitted on the PDCCH will be described.

The DCI format includes fields to be described next, and each field may be mapped to information bits a ₀ to a _A-1 . Each field may be mapped in the order described in each DCI format, and each field may include '0' padding bits. The first field may be mapped to the lowest order information bit a ₀ and other consecutive fields may be mapped to the higher order information bits. The most significant bit (MSB) in each field may be mapped to the lowest order information bit of the field. For example, the most significant bit of the first field may be mapped to a ₀ . Hereinafter, a set of fields included in each existing DCI format is called an information field.

DCI format 0

DCI format 0 is used for PUSCH scheduling. Information (field) transmitted through DCI format 0 is as follows.

1) A flag for distinguishing DCI format 0 from DCI format 1A (0 indicates DCI format 0 and 1 indicates DCI format 1A), 2) hopping flag (1 bit), 3) resource block designation and hopping resources 4) modulation and coding scheme and redundancy version (5 bits), 5) new data indicator (1 bit), 6) TPC command (2 bits) for the scheduled PUSCH, 7) DM-RS Cyclic shift (3 bits), 8) UL index, 9) downlink designation index (TDD only), 10) CQI request, and so on. If the number of information bits in DCI format 0 is smaller than the payload size of DCI format 1A, '0' is padded to equal the DCI format 1A and the payload size.

2. DCI format 1

DCI format 1 is used for one PDSCH codeword scheduling. In DCI format 1, the following information is transmitted.

1) Resource Allocation Header (Indicates Resource Allocation Type 0 / Type 1) —If the downlink bandwidth is less than 10 PRBs, the resource allocation header is not included and is assumed to be resource allocation type 0. 2) resource block designation, 3) modulation and coding scheme, 4) HARQ process number, 5) new data indicator, 6) redundancy version, 7) TPC command for PUCCH, 8) downlink designation index (TDD only), etc. . When the number of information bits of DCI format 1 is equal to DCI format 0 / 1A, one bit having a value of '0' is added to DCI format 1. In DCI format 1, if the number of information bits is equal to any one of {12, 14, 16, 20, 24, 26, 32, 40, 44, 56}, bits having one or more '0' values are assigned to DCI format 1. In addition, the payload size is different from the payload size of the {12, 14, 16, 20, 24, 26, 32, 40, 44, 56} and DCI formats 0 / 1A.

3. DCI format 1A

DCI format 1A is used for a simple scheduling or random access procedure of one PDSCH codeword.

The following information is transmitted in DCI format 1A. 1) flag to distinguish DCI format 0 and DCI format 1A, 2) localization / distribution VRB designation flag, 3) resource block designation, 4) modulation and coding scheme, 5) HARQ process number, 6) new data indicator, 7 9) TPC command for PUCCH, 9) DL designation index (TDD only). If the number of information bits of DCI format 1A is less than the number of information bits of DCI format 0, bits having a value of '0' are added to make the payload size of DCI format 0 the same. If the number of information bits in DCI format 1A is equal to any one of {12, 14, 16, 20, 24, 26, 32, 40, 44, 56}, a bit having a value of '0' is assigned to DCI format 1A. Add.

4. DCI format 1B

DCI format 1B is used for simple scheduling of one PDSCH codeword including precoding information. The following information is transmitted in DCI format 1B.

1) localization / distribution VRB designation flag, 2) resource block designation, 3) modulation and coding scheme, 4) HARQ process number, 5) new data indicator, 6) redundancy version, 7) redundancy version for PUCCH, 8) downlink Link designation index (TDD only), 9) transmitted precoding matrix indicator (TPMI) information for precoding, and 10) PMI check for precoding. If the number of information bits of DCI format 1B is equal to any one of {12, 14, 16, 20, 24, 26, 32, 40, 44, 56}, the bit having one '0' value is a DCI format. Is added to 1B.

5. DCI format 1C

DCI format 1C is used for very compact scheduling of one PDSCH codeword. The following information is transmitted in DCI format 1C.

1) an indicator indicating a gap value, 2) resource block designation, 3) transport block size index, and the like.

6. DCI format 1D

DCI format 1D contains precoding and power offset information and is used for simple scheduling for one PDSCH codeword.

The following information is transmitted in DCI format 1D.

1) localization / distribution VRB assignment flag, 2) resource block assignment, 3) modulation and coding scheme, 4) HARQ process number, 5) new data indicator, 6) redundancy version, 7) TPC command for PUCCH, 8) downlink Link designation index (TDD only), 9) TPMI information for precoding, and 10) downlink power offset. If the number of information bits of the DCI format 1D is equal to any one of {12, 14, 16, 20, 24, 26, 32, 40, 44, 56}, the bit having one '0' value is converted to the DCI format 1D. Add to

7. DCI Format 2

DCI format 2 is used for PDSCH designation for Peruvian MIMO operation. The following information is transmitted in DCI format 2D.

1) resource allocation header, 2) resource block designation, 3) TPC command for PUCCH, 4) downlink designation index (TDD only), 5) HARQ process number, 6) transport block and codeword swap flag (transport block to codeword swap flag), 7) modulation and coding scheme, 8) new data indicator, 9) redundancy version, 10) precoding information, and so on.

8. DCI format 2A

DCI format 2A is used for PDSCH designation for open loop MIMO operation. The following information is transmitted in DCI format 2A.

1) resource allocation header, 2) TPC command for PUCCH, 3) downlink designation flag (TDD only), 4) HARQ process number, 5) transport block and codeword swap flag, 6) modulation and coding scheme, 7) New data indicator, 8) redundancy version, 9) precoding information, and so on.

9. DCI Format 3

DCI format 3 is used to send TPC commands for PUCCH and PUSCH with 2-bit power adjustment. In DCI format 3, the following information is transmitted.

1) N transmit power control (TPC) commands. Where N is determined as in Equation 1 below.

[Equation 1]

Here, L _format0 is equal to the payload size of DCI format 0 before the CRC is pasted. If the floor L _format0 / 2 is smaller than (L _format0 / 2), one bit having a value of '0' is added.

10. DCI format 3A

DCI format 3A is used to send TPC commands for PUCCH and PUSCH with one bit of power adjustment. The following information is transmitted in DCI format 3A.

1) M TPC commands. Where M is the same as the payload size of DCI format 0 before L _format0 is pasted CRC.

For description of the DCI formats, refer to 5.3G of 3GPP TS 36.212 V8.7.0 (2009-05).

Downlink transmission modes between the base station and the terminal may be classified into the following seven types.

Single antenna port: This mode does not precode.

Transmit Diversity: Transmit diversity can be used for two or four antenna ports using SFBC.

Open loop spatial multiplexing: Ranked open loop mode based on RI feedback. If the rank is 1, transmit diversity may be applied. If the rank is greater than 1, a large delay CDD may be used.

Peruvian spatial multiplexing: Pre-coded feedback with dynamic rank adaptation is applied.

Multi User MIMO

Peruvian rank 1 precoding

7. Single antenna port: This mode can be used for beamforming when a UE-specific reference signal is used.

Table 1 below shows an example of a DCI format that the UE should monitor according to the downlink transmission mode described above.

TABLE 1

Table 2 below shows an example of the number of blind decoding times of the UE.

TABLE 2

As shown in Table 2, the UE may need to perform blind decoding up to 44 times. The UE may know in advance the payload size of the PDCCH that should be detected during blind decoding by receiving information on the bandwidth, transmission mode, the number of antenna ports, etc. of the carrier through system information from the base station. UE performs 16 * 2 = 32 times in UE-specific search space and 6 * 2 = 12 times in common search space for a total of 44 blinds once for downlink and uplink targeting the payload size of PDCCH known in advance Perform decoding.

5 shows a structure of an uplink subframe.

The uplink subframe may be divided into a control region and a data region in the frequency domain. The control region is allocated a Physical Uplink Control Channel (PUCCH) for transmitting uplink control information. The data region is allocated a PUSCH (Physical Uplink Shared Channel) for transmitting data (which may optionally be transmitted with control information). In order to maintain the characteristics of a single carrier, the UE does not simultaneously transmit the PUCCH and the PUSCH.

PUCCH for one UE is allocated to an RB pair in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers in each of a first slot and a second slot. The frequency occupied by RBs belonging to the RB pair allocated to the PUCCH is changed based on a slot boundary. This is called that the RB pair allocated to the PUCCH is frequency-hopped at the slot boundary. The terminal may obtain a frequency diversity gain by transmitting uplink control information through different subcarriers over time.

The uplink control information transmitted on the PUCCH includes a hybrid automatic repeat request (HARQ) acknowledgment (ACK) / non-acknowledgement (NACK), a channel quality indicator (CQI) indicating a downlink channel state, and an SR that is an uplink radio resource allocation request. (Scheduling Request).

PUSCH is mapped to an uplink shared channel (UL-SCH) which is a transport channel. The uplink data transmitted on the PUSCH may be a transport block which is a data block for the UL-SCH transmitted during the TTI. The transport block may include user data. Alternatively, the uplink data may be multiplexed data. The multiplexed data may be a multiplexed transport block and control information for the UL-SCH. For example, control information multiplexed with data may include CQI, PMI (Precoding Matrix Indicator), HARQ, RI (Rank Indicator), and the like. Alternatively, the uplink data may consist of control information only.

In the LTE-A system, uplink may use the SC-FDMA transmission scheme. The transmission scheme in which IFFT is performed after DFT spreading is called SC-FDMA. SC-FDMA may also be referred to as DFT-s OFDM. In SC-FDMA, a peak-to-average power ratio (PAPR) or a cubic metric (CM) may be lowered. In the case of using the SC-FDMA transmission scheme, since a non-linear distortion section of a power amplifier can be avoided, transmission power efficiency can be increased in a terminal with limited power consumption. Accordingly, user throughput may be high.

Meanwhile, the 3GPP LTE-A system may support a carrier aggregation system. The carrier aggregation system may refer to 3GPP TR 36.815 V9.0.0 (2010-3).

The carrier aggregation system refers to a system in which one or more carriers having a bandwidth smaller than the target broadband is configured to configure the broadband when the wireless communication system attempts to support the broadband. The carrier aggregation system may be called other names such as a multiple carrier system, a bandwidth aggregation system, and the like. The carrier aggregation system may be classified into a contiguous carrier aggregation system in which each carrier is continuous and a non-contiguous carrier aggregation system in which each carrier is separated from each other. Hereinafter, when simply referred to as a multi-carrier system or a carrier aggregation system, it should be understood to include both the case where the component carrier is continuous and the case where it is discontinuous.

In a continuous carrier aggregation system, a guard band may exist between each carrier. When collecting one or more carriers, a target carrier may use the bandwidth used by the existing system as it is for backward compatibility with the existing system. For example, the 3GPP LTE system supports bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz, and the 3GPP LTE-A system may configure a bandwidth of 20 MHz or more using only the bandwidth of the 3GPP LTE system. Alternatively, broadband can be configured by defining new bandwidth without using the bandwidth of the existing system. The carrier (component carrier) may correspond to each cell.

In a carrier aggregation system, a terminal may simultaneously transmit or receive one or a plurality of carriers according to capacity. A terminal (LTE-A terminal) according to the LTE-A standard may simultaneously transmit or receive a plurality of carriers. A terminal according to the LTE Rel-8 standard (LTE terminal) may transmit or receive only one carrier when each carrier constituting the carrier aggregation system is compatible with the LTE Rel-8 system. Therefore, when at least the same number of carriers used in uplink and downlink, all component carriers need to be configured to be compatible with the LTE Rel-8 system.

In order to efficiently use the plurality of carriers, the plurality of carriers may be managed by a media access control (MAC).

6 is an example of a base station and a terminal constituting a carrier aggregation system.

In the base station of FIG. 6- (a), one MAC manages and operates all n carriers to transmit and receive data. The same is true for the terminal of Fig. 6- (b). One transport block and one HARQ entity per component carrier may exist from the UE's point of view. The terminal may be scheduled for a plurality of carriers at the same time. The carrier aggregation system of FIG. 6 may be applied to both a continuous carrier aggregation system and a discontinuous carrier aggregation system. Each carrier managed by one MAC does not need to be adjacent to each other, and thus has an advantage in that it is flexible in terms of resource management.

7 and 8 illustrate another example of a base station and a terminal constituting a carrier aggregation system.

In the base station of FIG. 7- (a) and the terminal of FIG. 7- (b), one MAC manages only one carrier. That is, MAC and carrier correspond one-to-one. In the base station of FIG. 8- (a) and the terminal of FIG. 8- (b), MAC and carrier correspond to one-to-one for some carriers, and one MAC controls a plurality of carriers for the remaining carriers. That is, various combinations are possible due to the correspondence between the MAC and the carrier.

The carrier aggregation system of FIGS. 6 to 8 includes n carriers, and each carrier may be adjacent to or separated from each other. The carrier aggregation system may be applied to both uplink and downlink. In the TDD system, each carrier is configured to perform uplink transmission and downlink transmission. In the FDD system, a plurality of carriers may be divided into uplink and downlink. In a typical TDD system, the number of component carriers used in uplink and downlink and the bandwidth of each carrier are the same. In the FDD system, an asymmetric carrier aggregation system may be configured by varying the number and bandwidth of carriers used in uplink and downlink.

Hereinafter, each carrier that can be used to configure a broadband carrier in a multi-carrier system (carrier aggregation system) is called a component carrier (CC). The component carrier may use the bandwidth used by the existing system as it is for backward compatibility with the existing system. For example, 3GPP LTE systems support bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz, so each element carrier in a 3GPP LTE-A system must be one of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz. It may have a bandwidth and may aggregate a plurality of component carriers when configuring a broadband of 20 MHz or more. For convenience, the component carrier used for uplink may be abbreviated as UL CC (uplink component carrier) and the component carrier used for downlink may be referred to as downlink component carrier (DL CC).

9 is an example of a DL / UL asymmetric carrier aggregation system to which the present invention can be applied.

9- (a) illustrates a case where the number of DL component carriers is larger than the number of UL component carriers, and FIG. 9- (b) illustrates a case where the number of UL component carriers is larger than the number of DL component carriers. 9- (a) shows a case where two DL component carriers are linked with one UL component carrier, and FIG. 9- (b) shows a case where one DL component carrier is linked with two UL component carriers. Although illustrated, the number of component carriers constituting DL and UL and the ratio of linking DL component carriers and UL component carriers may be variously changed according to a carrier aggregation system to which the present invention is applied. The component carrier constituting the DL and the component carrier constituting the UL may be applied to a symmetric carrier aggregation system in which 1: 1 is linked.

In the LTE-A system, a carrier having backward compatibility may be accessible by a conventional terminal in consideration of compatibility with terminals of a conventional 3GPP LTE system, and may function as a single carrier or as part of carrier aggregation. Can be. Carriers with backward compatibility are always configured in the form of a pair of DL and UL in an FDD system. On the other hand, a carrier having no backward compatibility is newly defined without considering compatibility with terminals operating in a conventional LTE system and thus cannot be accepted by a conventional terminal.

In a carrier aggregation system, a form using one or a plurality of carriers may be considered a cell-specific and / or UE-specific method. In the following description of the present invention, a cell-specific method refers to a carrier configuration from a viewpoint of an arbitrary cell or a base station, and a terminal-specific method refers to a carrier configuration from a terminal perspective.

Cell-specific carrier aggregation may be in the form of carrier aggregation set by any base station or cell. The form of cell-specific carrier aggregation may be a form in which an association between DL and UL is determined according to Tx-Rx separation defined in 3GPP LTE release-8 / LTE-A in case of FDD system. For example, carrier frequencies in uplink and downlink may be designated by an E-UTRA Absolute Radio Frequency Channel Number (EARFCN), and the range of EARFCM is 0 to 65535. The relationship between the EARFCN and the carrier frequency in the downlink MHz unit can be given by the following equation.

[Equation 2]

In the above formula, N _DL is a downlink EARFCN, and F _{DL_low} and N _Offs-DL are given by the following table.

TABLE 3

The separation of the E-URTA transmission channel (carrier center frequency) and the reception channel (carrier center frequency) according to the transmission and reception channel bandwidths can be defined as shown in the following table.

TABLE 4

For this matter, see section 5.7 of 3GPP TS 36.101 V8.4.0, which was launched in December 2008.

In the carrier aggregation system, the PDCCH monitoring DL CC set (hereinafter, abbreviated to monitoring DL CC set) refers to a control channel through which a specific UE can receive control information, that is, a set of DL CCs for monitoring a PDCCH. The monitoring DL CC set may be configured UE-specifically or cell-specifically.

Cross-carrier scheduling is a resource allocation of a PDSCH transmitted on another component carrier through a PDCCH transmitted on a specific component carrier and / or other components other than the component carrier basically linked with the specific component carrier. A scheduling method for resource allocation of a PUSCH transmitted through a carrier. That is, the PDCCH and the PDSCH may be transmitted on different DL CCs, and the PUSCH may be transmitted on a UL CC other than the UL CC basically linked to the DL CC on which the PDCCH including the UL grant is transmitted. As such, in a system supporting cross-carrier scheduling, a carrier indicator indicating a DL CC / UL CC through which a PDSCH / PUSCH for which PDCCH provides control information is transmitted is required. A field including such a carrier indicator is hereinafter called a carrier indication field (CIF).

10 shows an example of the DCI format.

Referring to FIG. 10, a multi-carrier system supporting cross carrier scheduling may further include a carrier indication field (CIF) in the above-described conventional DCI format (which may be composed of m bits). For example, in the LTE-A system, CIF may be added to an existing DCI format (that is, a DCI format used in LTE) to expand the bit size of the DCI format by n bits (for example, 1 to 3 bits), and a PDCCH structure. Can reuse existing coding methods, resource allocation methods (ie, CCE-based resource mapping), and the like.

Non-carrier scheduling may also be supported in a multi-carrier system that supports cross-carrier scheduling. Non-cross carrier scheduling is a scheduling method of resource allocation of PDSCH of the same CC through PDCCH transmitted through a specific CC and resource allocation of PUSCH transmitted through one CC linked with the specific CC. In the case of non-carrier scheduling, the CIF may not be included.

The base station may semi-statically set whether cross-carrier scheduling is activated. That is, the base station may semi-statically set whether or not to include the CIF in the DCI format, and may be configured terminal-specific or cell-specific. Through this semi-static configuration it is possible to reduce the signaling overhead between the base station and the terminal.

When cross-carrier scheduling is activated, the number of blind decodings may be determined depending on whether a link relationship is established between the monitoring DL CC and the scheduled DL CC. Here, the scheduled DL CC refers to a DL CC scheduled by downlink control information transmitted through the monitoring DL CC.

11 illustrates a case where there is no link relationship between the monitoring DL CC and the scheduled DL CC.

Referring to FIG. 11, the monitoring DL CC set includes DL CC # 2 and DL CC # 3, and the scheduled DL CCs are DL CC # 1 to DL CC # 4. If there is no link relationship between the monitoring DL CC and the scheduled DL CC, the UE should perform blind decoding for detecting PDCCHs for all the scheduled DL CCs in each monitoring DL CC. That is, the terminal attempts to detect PDCCH for DL CC # 1, DL CC # 2, DL CC # 3, and DL CC # 4 in the control region of DL CC # 2, and also in the control region of DL CC # 3 Attempt PDCCH detection for 1 to DL CC # 4. Therefore, the total number of blind decodings that the UE must perform in the UE-specific search space for DCI detection related to downlink is 2 X 4 X 16 = 128 times.

12 illustrates a case where there is a link relationship between the monitoring DL CC and the scheduled DL CC.

Referring to FIG. 12, the monitoring DL CC set includes DL CC # 2 and DL CC # 3, and the scheduled DL CCs are DL CC # 1 to DL CC # 4. In this case, PDCCHs for DL CC # 1 and DL CC # 2 may be transmitted in the control region of DL CC # 2, and PDCCHs for DL CC # 3 and DL CC # 4 are transmitted in the control region of DL CC # 3. There may be a link relationship that may be transmitted. Such a link relationship may be predefined between the terminal and the base station, or the base station may inform the terminal through a higher layer signal such as an RRC.

As such, when there is a link relationship between the monitoring DL CC and the scheduled DL CC, the number of blind decodings to be performed by the UE is reduced. For example, when the UE considers the number of blind decodings to be performed in the UE-specific search space for DCI detection related to downlink, the UE is assigned to DL CC # 1 and DL CC # 2 in the control region of DL CC # 2. Since only PDCCHs can be transmitted, only 1 X 2 X 16 = 32 blind decoding operations need be performed. In addition, since the UE knows that only PDCCHs for DL CC # 3 and DL CC # 4 can be transmitted in the control region of DL CC # 3, the UE only needs to perform 1 × 2 × 16 = 32 blind decoding operations. Therefore, the total number of blind decodings to be performed by the terminal is 64 times. That is, the number of blind decoding times can be significantly reduced compared to the number of 128 blind decoding times described with reference to FIG. 10. As such, when there is a link relationship between the monitoring DL CC and the scheduled CC, the number of blind decodings to be performed by the UE is greatly reduced.

13 illustrates logical indexing of CIF values for a plurality of CCs.

A unique index of each component carrier for identifying the plurality of component carriers may be referred to as a physical index. That is, the physical index may be referred to as a value unique to each component carrier. For example, suppose that CC 0, CC 1, CC 2, ..., CC K are included in a set of CCs having different frequencies. The physical index of each CC is unique to each CC and may be given as N1, N2, ..., Nk. In this case, CIF values indicating each component carrier may be given as M1, M2, ..., Mk. Here, Nn and Mn (n is any one of 1 to k) may be the same value or different values. The base station may inform the terminal about the setting between the physical index of the CC and the CIF value, that is, the mapping relationship. Hereinafter, the base station exemplifies a case of informing the terminal of the mapping relationship through an upper layer signal such as an RRC message, but is not limited thereto. The mapping relationship between the component carrier and the CIF value may be changed. For example, when the component carrier allocated to the terminal increases or decreases, or even if the component carriers allocated to the terminal do not change, the CIF value may change according to a specific condition.

For example, suppose that the mapping relationship between the component carrier and the CIF value is changed from the first mapping relationship to the second mapping relationship, and the base station can arbitrarily set the mapping relationship between the component carrier and the CIF value. Then, for example, the CCs assigned to the UE in the first mapping relationship may be CC 0 and CC 2, the CIF value indicating CC 0 may be 0, and the CIF value indicating CC 2 may be 1. The CCs assigned to the UE in the second mapping relationship are CC 0, CC 2, and CC 3, the CIF value indicating CC 0 is 1, the CIF value indicating CC 2 is 2, and the CIF value indicating CC 3. May be three. Then, in the first mapping relationship, the CIF value 1 may indicate CC 2, but in the second mapping relationship, the CIF value 1 may indicate CC 0.

The base station may transmit information related to the second mapping relationship between the CC and the CIF value, that is, the CIF reset message, to the UE through the RRC message. The terminal transmits ACK / NACK information to the base station to inform whether the CIF resetting message is received. When the base station receives the ACK, the base station transmits a DCI according to the second mapping relationship. When the UE successfully decodes the DCI according to the second mapping relationship, the terminal transmits a reset complete message.

When changing the mapping relationship between the CC and the CIF to a higher layer signal such as an RRC message, such as a process of changing the CIF setting between the base station and the UE, an ambiguous period or a transition period may exist. . The ambiguity interval (or transition period) is a subframe in which the base station performs the next transmission to the terminal after receiving the ACK from the terminal to a subframe in which the next transmission is transmitted to the terminal after receiving the reset completion message from the terminal. Can be defined as This ambiguity period is considered due to the possibility of error, for example, when the UE actually transmits a NACK to the CIF resetting message of the base station and an error occurs and the base station receives the ACK. When the base station immediately transmits the DCI according to the second mapping relationship because the terminal transmits the ACK, a normal control signal / data transmission may not be possible between the base station and the terminal. This is because the UE may attempt to receive control signals / data from component carriers not indicated by the base station by interpreting the DCI according to the second mapping relationship as the DCI according to the first mapping relationship.

14 shows an example of a process of changing a CIF setting between a base station and a terminal.

Referring to FIG. 14, the base station may transmit information related to the mapping relationship between the CC and the CIF value, that is, the CIF reset message, to the UE through the RRC message.

The terminal transmits ACK / NACK information to the base station to inform whether the CIF resetting message is received. The base station transmits two types of DCI after the m subframe in the subframe receiving the ACK. If the mapping relationship between the component carrier and the CIF value is called a first mapping relationship before transmitting the CIF reset message, and the mapping relationship between the component carrier and the CIF value changed by the CIF reset message is called a second mapping relationship, DCI according to the mapping relationship and DCI according to the second mapping relationship are transmitted together. Accordingly, the terminal may receive the DCI according to the first mapping relationship even when the configuration change to the second mapping relationship is not completed.

If the terminal successfully decodes the DCI according to the second mapping relationship, the terminal transmits a reset complete message to the base station. The base station transmits the DCI to the terminal by setting the CIF according to the second mapping relationship from n subframes after receiving the reset complete message. After the base station transmits the CIF reset message and receives the reset complete message from the terminal, the base station can know that the mapping between the CC and the CIF value has changed without error.

Hereinafter, when it is necessary to change the mapping relationship between component carriers and CIF values, for example, adding a new component carrier to communicate with a terminal, or removing one or more component carriers from the set of component carriers currently in communication, and the like This section describes how to set the mapping between CCs and CIF values.

The base station transmits first CIF configuration information indicating a first mapping relationship between the CIF value and the CC. If it is necessary to change the mapping between the component carrier and the CIF value, the second CIF configuration information indicating the second mapping relationship is transmitted. At this time, the base station changes the mapping of the component carrier and the CIF value, that is, the change from the first mapping relationship to the second mapping relationship in consideration of the following requirements.

1. It is preferable to keep the mapping of the component carrier and the CIF value before the change when adding or removing the component carrier.

2. The newly added component carrier may map the lowest or highest value among available CIF values, which may be signaled as a higher layer signal such as RRC or a physical layer signal such as L1 signal.

3. When addition and removal of component carriers are performed at the same time, a CIF value is first assigned to the component carriers to be added. That is, the addition of component carriers has priority in mapping CIF values over removal.

4. When a plurality of component carriers are added at the same time, the lowest CIF value (or the highest CIF value) is mapped to the component carrier having the lowest physical index among the added component carriers.

5. Optionally, the added CC may be mapped to any CIF value and the mapped CIF value may be signaled as an RRC or L1 signal.

In the following description, the mapping relationship between CC and CIF values is set in consideration of the aforementioned requirements, taking the case of 5 CCs and 5 assignable CIF values, that is, (0, 1, 2, 3, 4). How to change.

15 to 19 show examples of setting CC and CIF values.

If there are five CCs in the UE-specific CC set, these CCs may be referred to as CC0, CC1, CC2, CC3, and CC4. In each drawing, the mapping relationship between the upper component carrier and the CIF value is called a first mapping relationship, and the mapping relationship between the lower component carrier and the CIF value is called a second mapping relationship.

Referring to FIG. 15, CC 0, CC 1, and CC 2 are activated and allocated to the terminal. That is, according to the first mapping relationship, the CIF value indicating CC 0 is 0, the CIF value indicating CC 1 is 1, and the CIF value indicating CC 2 is 2.

CC assigned by the base station to the terminal may be changed according to a change in channel environment or data transmission amount. For example, only CC 0 and CC 2 may be allocated to the terminal except CC 1. At this time, it is preferable that the CIF values for CC 0 and CC 2 remain the same before and after the change. Therefore, according to the second mapping relationship, the CIF value indicating CC 0 is 0 and the CIF value indicating CC 2 is 2. That is, except for CC 1 removed from the CC set, the mapping relationship between the CIF value and the CC remains the same.

Referring to FIG. 16, CC 3 may be added in a state where CC 0 and CC 2 are allocated to the terminal. In this case, the CIF values of CC 0 and CC 2 remain the same before and after the change, and the newly added CIF values of CC 3 will be assigned the minimum value 1 among the currently assignable CIF values, i.e. {1, 3, 4}. Can be. Alternatively, a maximum value of 4 among the currently available CIF values may be assigned. Alternatively, one may arbitrarily select one of the currently available CIF values and inform it through signaling.

Referring to FIG. 17, CC 4 may be added while CC 0, CC 2, and CC 3 are allocated to the terminal. In this case, as described with reference to FIG. 16, the CIF values of CC 0, CC 2, and CC 3 remain the same before and after the change, and the newly added CIF values of CC 4 are among the currently available CIF values, that is, {3, 4}. You can assign a minimum or maximum value. Alternatively, one may arbitrarily select one of the currently available CIF values and inform it through signaling.

Referring to FIG. 18, in a state where CC 0, CC 2, CC 3, and CC 4 are allocated to the UE, CC 1 may be added and CC 2 and CC 3 may be removed at the same time. In this case, it is preferable to perform CIF value mapping for the newly added CC first and then remove the CIF value for the CC to be removed. If the CIF value for the removed CC is first removed, and then the CIF value for the added CC is added, the CIF value for the removed CC may be added to the newly added CC, resulting in confusion in the mapping of the CC and CIF values This can happen.

Referring to FIG. 19, CC 2 and CC 3 may be added while CC 0, CC 1, and CC 4 are allocated to the UE. That is, a plurality of CCs can be added at the same time. In this case, the lowest (smaller) CIF value that can be assigned to the CC having the lowest physical index based on the physical indexes of the plurality of CCs added, and the remaining CIF values can be allocated to the CC having the high physical index in ascending order. have. Alternatively, the highest (large) value that can be allocated to the CC having the lowest physical index may be allocated, and the remaining CIF values may be allocated to the CC having the high physical index in descending order. Alternatively, the BS may randomly allocate a CIF value to each CC and then signal the BS.

As described above, when the number of component carriers allocated to the terminal is changed, at least one component carrier allows the same CIF value to be mapped in the component carrier-CIF value mapping relationship before and after the change. As such, the base station may transmit information such as an RRC message including downlink control information (DCI), system information, first CIF configuration information, or second CIF configuration information through at least one CC that does not change the CIF value. .

In the above examples, the number of component carriers and the number of assignable CIF values are the same, the number of component carriers may be larger than the number of assignable CIF values, and all CIF values may be used for the activated component carriers. . At this time, a new n component carriers may be added and m component carriers may be removed (but m is equal to or larger than n). In this case, the CC may be first removed, and the CIF value allocated to the removed CC may be mapped to the CC. The lowest CIF value or the highest CIF value among the CIF values allocated to the removed CCs may be allocated to the CC having the lowest physical index (or CC having the highest physical index) among the CCs added.

Alternatively, a method of mapping an arbitrary CIF value among the CIF values of the removed CCs to the additional CC and signaling the same.

20 is a block diagram illustrating a base station and a terminal.

The base station 100 includes a processor 110, a memory 120, and an RF unit 130. The processor 110 implements the proposed functions, processes and / or methods. For example, the processor 110 may include first CIF configuration information indicating a first mapping relationship between a CIF value and a component carrier, downlink control information (DCI) including a carrier indication field, and a value and element of a CIF. The second CIF configuration information indicating the second mapping relationship of the carrier is transmitted. The memory 120 is connected to the processor 110 and stores various information for driving the processor 110. The RF unit 130 is connected to the processor 110 and transmits and / or receives a radio signal.

The terminal 200 includes a processor 210, a memory 220, and an RF unit 230. The processor 210 implements the proposed functions, processes and / or methods. For example, the processor 210 receives the first CIF configuration information or the second CIF configuration information to determine the mapping relationship between the component carrier and the CIF value. When the mapping relationship between the component carrier and the CIF value is changed, the DCI is received through at least one component carrier in which the CIF value is not changed. The memory 220 is connected to the processor 210 and stores various information for driving the processor 210. The RF unit 230 is connected to the processor 210 to transmit and / or receive a radio signal.

Processors 110 and 210 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, data processing devices, and / or converters for interconverting baseband signals and wireless signals. The memory 120, 220 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and / or other storage device. The RF unit 130 and 230 may include one or more antennas for transmitting and / or receiving a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in the memories 120 and 220 and executed by the processors 110 and 210. The memories 120 and 220 may be inside or outside the processors 110 and 210, and may be connected to the processors 110 and 210 by various well-known means.

Although the present invention has been described above with reference to the embodiments, it will be understood by 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 of the following claims.

Claims (8)

1. In a method of setting a carrier indication field for indicating a component carrier in a multi-carrier system using a plurality of component carriers,
   Transmitting first CIF configuration information indicating a first mapping relationship between a value of a carrier indication field (CIF) and a component carrier;
   Transmitting downlink control information (DCI) including a carrier indication field; And
   Transmitting second CIF setting information informing a second mapping relationship between a value of a carrier indication field and a component carrier,
   The carrier indication field is a field indicating one component carrier among the plurality of component carriers, and at least one component carrier is mapped to the same carrier indication field value in the first mapping relationship and the second mapping relationship. How to.
2. The method of claim 1, wherein the first CIF configuration information and the second CIF configuration information are transmitted through the at least one CC.
3. The method of claim 2, wherein the downlink control information is transmitted through the at least one CC.
4. 2. The method of claim 1, wherein the carrier indication field has a 3-bit size.
5. The method of claim 1, wherein the first mapping information and the second mapping information are included in a radio resource control (RRC) message and transmitted.
6. The carrier indication according to claim 1, wherein when there is a component carrier added based on the component carriers mapped in the first mapping relationship among the component carriers mapped in the second mapping relationship, a carrier indication usable to the added component carrier is available. The minimum or maximum value of the field value is mapped.
7. The component carrier of claim 1, wherein the component carriers mapped in the second mapping relation are present when the component carriers removed based on the component carriers mapped in the first mapping relation exist among the component carriers mapped in the second mapping relation. Among them, the value of the carrier indication field mapped to the remaining component carriers except for the component carrier to be removed is the same as the first mapping relationship.
8. The component carrier of claim 1, wherein the component carrier added and the component carrier removed based on the component carriers mapped in the first mapping relationship among the component carriers mapped in the second mapping relationship exist. The minimum value or the maximum value of the value of the carrier indication field usable in the first mapping method.

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