WO2012148169A2 - Method and apparatus for transmitting channel state information in carrier aggregation system - Google Patents

Abstract

Provided are a method and an apparatus for transmitting channel state information (CSI) by a user equipment in a carrier aggregation system, in which a plurality of serving cells are set. The method is comprises the following steps: selecting serving cells which are set by receiving setting information on allocation of the plurality of serving cells; selecting at least one activated serving cell from the serving cells that are set by receiving activation information, which expresses activation of each of the serving cells that are set; deciding the size of a channel state information reporting field based on the serving cells that are set; generating the channel state information based on priority; and transmitting the channel state information that is generated through the channel state information reporting field having the size which is decided.

Description

Method and apparatus for transmitting channel state information in carrier aggregation system

The present invention relates to wireless communication, and more particularly, to a method and apparatus for transmitting channel state information in a carrier aggregation system.

Recently, a carrier aggregation system has attracted attention. The carrier aggregation system refers to a system that configures a broadband by collecting one or more component carriers (CCs) having a bandwidth smaller than a target broadband when the wireless communication system attempts to support the broadband. In a carrier aggregation system, the term serving cell may be used instead of the term component carrier. Here, the serving cell includes a downlink component carrier (DL CC) and an uplink component carrier (UL CC) or DL CC only. That is, the carrier aggregation system is a system in which a plurality of serving cells are configured in one terminal.

In the downlink of the carrier aggregation system, the base station configures a plurality of DL CCs to the terminal, and then only some DL CCs may be activated or deactivated through signaling as necessary. In this case, the UE may transmit channel state information (CSI) only for the activated DL CC. The CSI may be transmitted through an uplink control channel such as a physical uplink control channel (PUCCH) or with uplink data through an uplink data channel such as a physical uplink shared channel (PUSCH). When the CSI is transmitted together with the uplink data through the uplink data channel, the CSI is represented by piggybacking and transmitting.

However, when misrecognition occurs between the base station and the terminal with respect to the activated DL CC, an error may occur in the DL CC that is the target of the channel state information. In addition, when piggybacking and transmitting channel state information to an uplink data channel, when the type of channel state information and the number of payload bits are changed due to a change in the DL CC serving as the channel state information, the uplink data is changed. Problems can also occur in the encoding / decoding process. This is because uplink data and CSI are multiplexed in the uplink data channel when piggyback transmission of the CSI, because the multiplexing method may vary depending on the type of the CSI.

There is a need for a method and apparatus capable of transmitting channel state information and uplink data without error even when misidentification occurs in activation / deactivation of a DL CC between a base station and a terminal in a carrier aggregation system.

An object of the present invention is to provide a method and apparatus for transmitting channel state information in a carrier aggregation system.

In one aspect, a method for transmitting channel state information (CSI) performed by a terminal in a carrier aggregation system in which a plurality of serving cells is configured is provided. The method determines configuration of serving cells by receiving configuration information on a plurality of serving cell assignments, and receives activation information indicating whether activation of each of the configured serving cells is performed to determine at least one activated serving cell among the configured serving cells. Determine the size of the channel state information reporting field based on the set serving cells, generate channel state information according to priority, and generate the channel state information through the channel state information reporting field of the determined size. It characterized in that for transmitting.

The size of the channel state information reporting field is determined by the number of bits of channel state information for the serving cell determined according to a predetermined rule among the set serving cells, and the set serving cells may include an active serving cell and an inactive serving cell. Can be.

The size of the channel state information reporting field may be determined as the number of bits of channel state information for the serving cell determined according to the predetermined rule among the set serving cells scheduled to simultaneously transmit channel state information in the same subframe.

The size of the channel state information reporting field may be determined as the number of bits of channel state information of a serving cell that transmits channel state information with the maximum number of bits in the same subframe among the set serving cells that are scheduled to transmit channel state information simultaneously in the same subframe. Can be.

The size of the channel state information reporting field may be determined as the number of bits of channel state information of a serving cell that transmits channel state information at the maximum number of bits regardless of subframes among the set serving cells.

The size of the channel state information reporting field may be given as a constant value.

The size of the channel state information reporting field is the number of bits of the channel state information of the secondary cell having a higher priority than the channel state information of the primary cell among the set serving cells scheduled to simultaneously transmit channel state information in the same subframe, and the primary It may be determined as a larger value among the number of bits of channel state information of a cell.

The channel state information generated according to the priority may be generated according to the priority among channel state information of the at least one active serving cell.

The channel state information generated according to the priority may be generated according to the priority among the channel state information of the set serving cells.

The channel state information may include at least one of a channel quality indicator (CQI) indicating channel quality, a precoding matrix index (PMI) indicating a precoding matrix, and a rank indicator (RI) indicating the number of layers recommended by the terminal. .

In another aspect, a terminal includes a radio frequency (RF) unit for transmitting or receiving a radio signal; And a processor connected to the RF unit, wherein the processor receives configuration information regarding a plurality of serving cell assignments to determine set serving cells, and receives activation information indicating whether each of the set serving cells is activated. Determine at least one active serving cell among the set serving cells, determine a size of a channel state information reporting field based on the set serving cells, generate channel state information according to priority, and channel of the determined size The generated channel state information is transmitted through a state information reporting field.

Among the plurality of serving cells configured for the UE, uplink data can be transmitted without error even when an error occurs in activation / deactivation of some serving cells, more specifically, some DL CCs, and errors of channel state information can be minimized. have.

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

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

3 shows a structure of a downlink subframe.

4 shows a structure of an uplink subframe.

5 shows a channel structure of PUCCH format 2 / 2a / 2b for one slot in a normal CP.

FIG. 6 shows an example in which 20-bit coded bits according to PUCCH format 2 are mapped to resource blocks of each slot in one subframe.

7 shows an example of piggybacking (multiplexing) CSI and transmitting it.

FIG. 8 illustrates a process of processing uplink data and uplink control information when piggyback transmission of uplink control information such as CSI and ACK / NACK is performed on a PUSCH.

FIG. 9 illustrates an example of resource mapping of uplink control information to a PUSCH region of subframe n of FIG. 7 through a processing process as illustrated in FIG. 8.

10 shows single RM coding and dual RM coding used in PUCCH format 3.

11 is a comparative example of a single carrier system and a carrier aggregation system.

12 shows an example of selecting one serving cell in a situation where CSIs for a plurality of downlink DL CCs collide in a carrier aggregation system.

FIG. 13 shows an example of an activation / deactivation state of each serving cell in a situation in which a plurality of serving cells are configured for a terminal in a carrier aggregation system.

14 illustrates an example in which a misperception occurs on whether to activate a DL CC between a base station and a terminal.

FIG. 15 illustrates an example of transmitting ACK / NACK and CSI through joint coding through PUCCH format 3. FIG.

16 shows a CSI transmission method according to an embodiment of the present invention.

17 illustrates a situation applied to FIGS. 18 to 21.

18 shows an application example of Method 1 above.

19 shows an application example of Method 2 above.

20 shows an application example of Method 3 above.

21 shows an application example of Method 4 above.

22 is a block diagram illustrating a base station and a terminal in which an embodiment of the present invention is implemented.

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 the evolution of 3GPP LTE. For clarity, the following description focuses on LTE-A, but the technical spirit of the present invention is not limited thereto.

The wireless communication system includes at least one base station (BS) and a terminal. Base stations provide communication services for specific geographic areas. A base station generally refers to a fixed station communicating with a terminal, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), and an access point.

Terminal (User Equipment, UE) can be fixed or mobile, MS (Mobile Station), MT (Mobile Terminal), UT (User Terminal), SS (Subscriber Station), wireless device, PDA (Personal) It may be called other terms such as a digital assistant, a wireless modem, a handheld device, and the like.

Hereinafter, downlink means communication from the base station to the terminal, and uplink means communication from the terminal to the base station. The base station and the terminal may perform communication through a radio frame.

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

Referring to FIG. 1, 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 used to represent one symbol period since 3GPP LTE uses OFDMA in downlink, and may be called a different name according to a multiple access scheme. For example, when SC-FDMA is used as an uplink multiple access scheme, it may be referred to as an SC-FDMA symbol. A resource block (RB) includes a plurality of consecutive subcarriers in one slot in resource allocation units. 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. For example, in 3GPP LTE, one slot includes 7 OFDM symbols in a normal cyclic prefix (CP), and one slot includes 6 OFDM symbols in an extended CP. It is defined.

2 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 N _RB resource blocks in the frequency domain. The number N _RB of resource blocks included in the downlink slot depends on the downlink transmission bandwidth set in the cell. For example, in the LTE system, N _RB may be any one of 6 to 110. One resource block includes a plurality of subcarriers in the frequency domain. 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.

Here, an exemplary resource block includes 7 × 12 resource elements including 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain, but the number of OFDM symbols and the number of subcarriers in the resource block is equal to this. It is not limited. 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. The number of subcarriers in one OFDM symbol may be selected and used among 128, 256, 512, 1024, 1536 and 2048.

3 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.

PDCCH includes resource allocation and transmission format of downlink-shared channel (DL-SCH), resource allocation information of uplink shared channel (UL-SCH), paging information on PCH, system information on DL-SCH, random access transmitted on PDSCH Resource allocation of upper layer control messages such as responses, sets of transmit power control commands for individual UEs in any UE group, activation of Voice over Internet Protocol (VoIP), and the like. A plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH is transmitted on an aggregation of one or several consecutive CCEs. CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups. 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.

The base station determines the PDCCH format according to downlink control information (DCI) to be sent to the terminal, and attaches a CRC (Cyclic Redundancy Check) to the control information. In the CRC, a unique identifier (RNTI: Radio Network Temporary Identifier) is masked according to an owner or a purpose of the PDCCH. If the PDCCH is for a specific terminal, a unique identifier of the terminal, for example, a C-RNTI (Cell-RNTI) may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier, for example, P-RNTI (P-RNTI), may be masked to the CRC. If the PDCCH is for a System Information Block (SIB), the system information identifier and the System Information-RNTI (SI-RNTI) may be masked to the CRC. A random access-RNTI (RA-RNTI) may be masked to the CRC to indicate a random access response that is a response to the transmission of the random access preamble of the UE.

A higher layer signal such as downlink data and terminal specific radio resource control (RRC) message may be transmitted to the PDSCH.

4 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 PUCCH (Physical Uplink Control Channel) for transmitting uplink control information (UCI). The data region is allocated a physical uplink shared channel (PUSCH) for transmitting uplink data. The UE may support simultaneous transmission of PUSCH and PUCCH or may not support simultaneous transmission of PUCCH and PUSCH.

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 be user information. Alternatively, the uplink data may be multiplexed data. The multiplexed data may be multiplexed of a transport block for UL-SCH and uplink control information. For example, uplink control information multiplexed to data includes channel quality indicator (CQI), precoding matrix indicator (PMI), HARQ ACK / NACK (acknowledgement / not-acknowledgement), RI (Rank Indicator), and PTI (precoding type indicator). ) And the like. CQI is information indicating channel quality, and PMI is an index of a precoding matrix recommended by the terminal when codebook based precoding is applied. RI represents the number of layers recommended by the terminal, that is, the number of streams that can be independently transmitted. HARQ ACK / NACK is acknowledgment information for data transmitted by a base station. PTI is information that informs the base station of the type of CSI to be transmitted (type of PMI) and configuration. CQI / PMI / RI / PTI is referred to as channel state information (CSI). The uplink data may consist of only uplink control information.

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 the first slot and the second slot. The frequency occupied by the resource block belonging to the resource block 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.

PUCCH carries various types of uplink control information according to a format. PUCCH format 1 carries a scheduling request (SR). In this case, an OOK (On-Off Keying) method may be applied. PUCCH format 1a carries ACK / NACK (Acknowledgement / Non-Acknowledgement) modulated in a Bit Phase Shift Keying (BPSK) scheme for one codeword. PUCCH format 1b carries ACK / NACK modulated by Quadrature Phase Shift Keying (QPSK) for two codewords. PUCCH format 2 carries a channel quality indicator (CQI) modulated in a QPSK scheme. PUCCH formats 2a and 2b carry CQI and ACK / NACK. PUCCH format 3 transmits uplink control information (ACK / NACK and SR) of a maximum 21-bit payload size.

5 shows a channel structure of PUCCH format 2 / 2a / 2b for one slot in a normal CP. As described above, the PUCCH format 2 / 2a / 2b is used for transmission of CQI.

Referring to FIG. 5, SC- FDMA symbols 1 and 5 are used for a DM RS (demodulation reference symbol) which is an uplink reference signal in a normal CP (SC-FDMA symbol 3 is used for a DM RS in case of an extended CP). do). CQI information bits having a payload size of 10 bits are channel coded, for example, at a rate of 1/2 to be coded bits of 20 bits. Reed-Muller (RM) codes may be used for channel coding. In each slot, channel coded 10-bit coded bits are transmitted, and 20-bit coded bits are transmitted throughout the subframe.

Table 1 below is an example of an (20, A) RM code used for channel coding of uplink control information (UCI) of 3GPP LTE. Here, A may be the number of bits of the UCI information bit string. The UCI information bit string is denoted by a ₀ , a ₁ , a ₂ , ..., a _A-1 . The UCI information bit string may be used as an input of a channel coding block using an RM code of (20, A).

TABLE 1

The channel coded bits are denoted by b ₀ , b ₁ , b ₂ , ..., b _B-1 . Channel coded bits may be generated by Equation 1 below.

[Equation 1]

In Equation 1, i = 0,1,2, ..., B-1.

Referring back to FIG. 5, the channel coded bits are scrambling and then QPSK constellation mapping to generate QPSK modulation symbols (d ₀ to d ₄ in slot 0). Each QPSK modulation symbol is modulated with a cyclic shift (eg, 52) of a basic RS sequence 51 having a length of 12 and OFDM modulated, and then transmitted in each of 10 SC-FDMA symbols (eg, 53) in a subframe. 12 uniformly spaced cyclic shifts allow 12 different terminals to be orthogonally multiplexed in the same PUCCH resource block. As a DM RS sequence applied to SC- FDMA symbols 1 and 5, a basic RS sequence 51 having a length of 12 may be used.

FIG. 6 shows an example in which 20-bit coded bits according to PUCCH format 2 are mapped to resource blocks of each slot in one subframe.

Referring to FIG. 6, the first 10 bits of the 20 bit coded bits are mapped to the resource block of the first slot, and the remaining 10 bits are mapped to the resource block of the second slot. The resource block of the first slot and the resource block of the second slot indicate frequency hopping.

In LTE rel-8, when CSI is transmitted in PUCCH format 2, channel coding of up to 13 bits of CSI (or 13 bits in combination with CSI and ACK / NACK) is performed using the (20, A) RM code of Table 1 above. Can be.

The CSI may be transmitted through the PUCCH, but may be transmitted after being piggybacked on the PUSCH.

7 shows an example of piggybacking (multiplexing) CSI and transmitting it.

Referring to FIG. 7, the UE does not transmit CSI in the PUCCH region in subframe n but transmits uplink data in the PUSCH region. On the other hand, in the subframe n + 1, the CSI is transmitted only through the PUCCH region, and in the subframe n + 2, the uplink data is transmitted only through the PUSCH region. As in subframe n, transmitting the CSI together with the uplink data in the PUSCH region is called piggyback transmission of the CSI.

In 3GPP LTE Rel-8, a single carrier having good peak-to-average power ratio (PAPR) characteristics and cubic metri (CM) characteristics affecting the performance of the power amplifier for efficient utilization of the power amplifier of the terminal in the uplink. Maintain transmission. In 3GPP LTE Rel-8, in case of PUSCH transmission, data to be transmitted is spread to maintain single carrier characteristics by DFT (discrete Fourier Transform), and in the case of PUCCH transmission, control information is transmitted by transmitting control information in a sequence having a single carrier characteristic. Carrier characteristics were maintained. However, when the DFT spreading data is allocated to discontinuous subcarriers in the frequency domain or when PUSCH and PUCCH are simultaneously transmitted, a single carrier characteristic is broken. Therefore, when simultaneous transmission of PUCCH and PUSCH is scheduled in the same subframe, CSI to be transmitted on PUCCH is transmitted together with data in PUSCH, that is, piggybacked to maintain single carrier characteristics.

FIG. 8 illustrates a process of processing uplink data and uplink control information when piggyback transmission of uplink control information such as CSI and ACK / NACK is performed on a PUSCH.

Referring to FIG. 8, data bits a ₀ , a ₁ ,..., A _A-1 are given in the form of one transport block for every TTI. First, data bits a _0, a _1, ..., in _{a A-1 CRC (Cyclic Redundancy} Check) parity bits to _{p 0, p 1, ...,} p L-1 are added, CRC bit addition B ₀ , b ₁ , ..., b _B-1 are generated (S200). Here, the subscripts B, A, and L are related to B = A + L. The relationship between a _k and b _k can be expressed as

[Equation 2]

The CRC additional bits b ₀ , b ₁ ,..., B _B-1 are split into code block units, and CRC parity bits are added to the code block units (S210). The bit sequence output after code block segmentation is called c _r0 , c _r1 , ..., c _{r (Kr-1)} . Here, when the total number of code blocks is C, r is a code block number and K _r is the number of bits for the code block number r.

Channel coding is performed on the bit sequence for the given code block (S220). Encoded bits are represented by d ⁽ⁱ⁾ ₀ , d ⁽ⁱ⁾ ₁ , ..., d ⁽ⁱ⁾ _D-1 , where D is the number of encoded bits per output stream, i is the index of the encoder output bit stream .

The encoded bits are subjected to rate matching (S230) and code block concatenation (S240) to generate a data bit sequence f ₀ , f ₁ , ..., f _G-1 . . Rate matching means that the amount of data to be transmitted is matched with the maximum transmission amount of the actual channel for each transmission unit time, for example, TTI. Here, G represents the total number of encoded bits used for transmission except for bits used for uplink control information transmission when uplink control information is multiplexed on the PUSCH.

Meanwhile, uplink control information together with uplink data may be multiplexed (piggybacked). The uplink data and the uplink control information may use different coding rates by allocating different numbers of coded symbols for transmission. The uplink control information includes CQI, PMI, RI, PTI, and ACK / NACK.

CQI o₀, o_One, ..., o_O-1 (O is the number of bits of the CQI) is the channel coding is performed to control information bit sequence q₀, q_One, ..., q_QCQI-1Is generated (S250). RI o₀                 ^RI, o_One                 ^RI , ..., o_oRI-1                 ^RI Channel coding is performed to control the bit sequence q₀                 ^RI, q_One                 ^RI, ..., q_QRI-1                 ^RIIs generated (S260). Similarly ACK / NACK o₀                 ^ACK , o_One                 ^ACK ,… , o_oACK-1                 ^ACK Channel coding is performed to control the bit sequence q₀                 ^ACK, q_One                 ^ACK, ..., q_{QACK                                  -One}                 ^ACKIs generated (S270).

The generated data bit sequence f ₀ , f ₁ , ..., f _G-1 and CQI control information bit sequence q ₀ , q ₁ , ..., q _QCQI-1 is a multiplexed sequence g ₀ , g ₁ , ..., g multiplexed by _H-1 (S280). During multiplexing, the control information bit sequences q ₀ , q ₁ , ..., q _QCQI-1 of the _CQI can be placed _first , and then the data bit sequences f ₀ , f ₁ , ..., f _G-1 can be arranged. have. That is, when H = G + Q, [g ₀ , g ₁ , ..., g _H-1 ] = [q ₀ , q ₁ , ..., q _QCQI-1 , f ₀ , f ₁ , .. , f _G-1 ].

The multiplexed sequence g ₀ , g ₁ , ..., g _H-1 is mapped to the modulation sequence h ₀ , h ₁ , ..., h _H'-1 by a channel interleaver (S280). In addition, the control information bit sequence of RI or ACK / NACK is mapped to modulation sequence h ₀ , h ₁ , ..., h _H'-1 by the channel interleaver. Where h _i is a modulation symbol in constellation and H '= H + Q _RI . Each modulation symbol of modulation sequence h ₀ , h ₁ , ..., h _H'-1 is mapped to a resource element for PUSCH. A resource element is an allocation unit on a subframe defined by one SC-FDMA symbol (or OFDMA symbol) and one subcarrier.

As described above, when the CSI is piggybacked on the PUSCH and transmitted, up to 11 bits of the CSI may be channel coded using the (32, A) RM code to adjust the code rate to be transmitted in the PUSCH. Truncation or circular repetition is performed. Table 2 below shows an example of the (32, A) RM codes.

TABLE 2

FIG. 9 illustrates an example of resource mapping of uplink control information to a PUSCH region of subframe n of FIG. 7 through a processing process as illustrated in FIG. 8.

Piggyback (multiplexing) methods in the PUSCH region may be different according to the type of uplink control information. As shown in FIG. 9, in a PUSCH region of a subframe, one symbol in a first slot or a second slot is assigned a DM demodulation reference signal (DM RS). The DM RS is a reference signal used for demodulation of uplink data and uplink control information transmitted in a PUSCH region. 9 shows an example in which the DM RS is allocated to the fourth symbol of the first slot and the second slot.

Some of the uplink control information, for example, CQI / PMI (control information type 1) is allocated from the first symbol of the subframe to the last available symbol for one subcarrier in the region in which the PUSCH is transmitted, and then to the next subcarrier in the frequency domain. Can be assigned. That is, the CQI / PMI may be allocated from the first symbol to the last symbol of the subframe except for the symbol to which the DM RS is allocated.

ACK / NACK (control information type 2) of the uplink control information may be allocated to a symbol adjacent to a symbol to which a DM RS is allocated. The number of symbols to which ACK / NACK can be allocated may be up to four. Using this allocation method, ACK / NACK can use the best channel estimation result. The ACK / NACK may be allocated to a symbol adjacent to a symbol to which a DM RS is allocated after puncturing data, that is, PUSCH data. The control information type 3 (RI) may be assigned to a symbol adjacent to a symbol to which ACK / NACK can be allocated. CQI / PMI / RI, etc. of the uplink control information occupy a portion of PUSCH resources and are multiplexed through rate matching. In addition, ACK / NACK is multiplexed by puncturing among PUSCH resources.

Meanwhile, in LTE-A, PUCCH format 3 is introduced to transmit up to 21 bits of UCI information bits. In a normal CP of PUCCH format 3, a 48-bit coded bit may be transmitted by encoding up to 21 bits of UCI information bits. In this case, channel coding, interleaving, and resource element mapping may vary according to the number of UCI information bits, that is, the payload size of the UCI.

10 shows single RM coding and dual RM coding used in PUCCH format 3.

Referring to FIG. 10, in the PUCCH format 3, when the number of UCI information bits is 11 bits or less, 32 bits are generated by channel coding using one (32, A) RM code shown in Table 2 as shown in FIG. After generating a 48-bit coded bit stream through cyclic iteration, interleaving and resource element mapping are performed (single RM coding). On the other hand, if the number of UCI information bits exceeds 11 bits, as shown in (b) of FIG. 10, 32 bits are generated by channel coding using two (32, A) RM codes shown in Table 2, and then truncated. Generate two 24-bit coded bitstreams. Then, interleaving and resource element mapping are performed (dual RM coding).

If up to 21 bits of UCI information bits are transmitted in the PUSCH, when the number of UCI information bits is 11 bits or less, truncation is performed to adjust the code rate to be transmitted in the PUSCH using (32, A) RM coding as in the existing LTE REL-8. Or perform a recursive iteration. On the other hand, if the number of UCI information bits exceeds 11 bits, two coded bit streams are generated using dual RM coding, and truncation or cyclic iteration is performed to match the code rates transmitted to the PUSCH. When PUCCH format 3 is used in an SR transmission subframe, the UCI information bit string is configured with ACK / NACK first, and a bit string configured in such a manner that an SR is connected to ACK / NACK.

As described above, the channel coding process varies according to the payload size of the UCI information bit string.

The carrier aggregation system will now be described.

11 is a comparative example of a single carrier system and a carrier aggregation system.

Referring to FIG. 11, a single carrier system supports only one carrier for uplink and downlink to a user equipment. The bandwidth of the carrier may vary, but only one carrier is allocated to the terminal. On the other hand, in a carrier aggregation system, a plurality of component carriers (DL CC A to C, UL CC A to C) may be allocated to a terminal. For example, three 20 MHz component carriers may be allocated to allocate a 60 MHz bandwidth to the terminal.

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, simply referred to as 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.

When one or more component carriers (CCs) are collected, a target component 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 system frequency band of a wireless communication system is divided into a plurality of carrier frequencies. Here, the carrier frequency means a center frequency of a cell. Hereinafter, a cell may mean a downlink frequency resource and an uplink frequency resource. Alternatively, the cell may mean a combination of a downlink frequency resource and an optional uplink frequency resource. In addition, in general, when a carrier aggregation (CA) is not considered, one cell may always have uplink and downlink frequency resources in pairs.

In order to transmit and receive packet data through a specific cell, the terminal must first complete configuration for a specific cell. In this case, the configuration refers to a state in which reception of system information necessary for data transmission and reception for a corresponding cell is completed. For example, the configuration may include an overall process of receiving common physical layer parameters required for data transmission and reception, or MAC layer parameters, or parameters required for a specific operation in the RRC layer. When the set cell receives only the information that the packet data can be transmitted, the cell can be immediately transmitted and received.

The cell in the configuration complete state may exist in an activation or deactivation state. Here, activation means that data is transmitted or received or is in a ready state. The UE may monitor or receive a control channel (PDCCH) and a data channel (PDSCH) of an activated cell in order to identify resources (which may be frequency, time, etc.) allocated thereto.

Deactivation means that transmission or reception of traffic data is impossible, and measurement or transmission of minimum information is possible. The terminal may receive system information (SI) required for packet reception from the deactivated cell. On the other hand, the terminal does not monitor or receive the control channel (PDCCH) and data channel (PDSCH) of the deactivated cell in order to check the resources (may be frequency, time, etc.) allocated to them.

The cell may be divided into a primary cell, a secondary cell, and a serving cell.

The primary cell refers to a cell operating at a primary frequency, and is a cell in which the terminal performs an initial connection establishment procedure or connection reestablishment with the base station, or is indicated as a primary cell in a handover process. It means a cell.

The secondary cell refers to a cell operating at the secondary frequency and is set up once the RRC connection is established and used to provide additional radio resources.

The serving cell is configured as a primary cell when the CA is not configured or the terminal cannot provide the CA. When a CA is set, the term serving cell is used to denote a set composed of one or a plurality of cells of a primary cell and all secondary cells.

That is, the primary cell refers to one serving cell that provides security input and NAS mobility information in an RRC connection or re-establishment state. According to the capabilities of the terminal, at least one cell may be configured to form a serving cell set together with a primary cell, wherein the at least one cell is called a secondary cell. Therefore, the set of serving cells configured for one terminal may be configured of only one primary cell or one primary cell and at least one secondary cell.

A primary component carrier (PCC) refers to a component carrier corresponding to a primary cell. The PCC is a CC in which the terminal initially makes a connection (connection or RRC connection) with the base station among several CCs. The PCC is a special CC that manages a connection (Connection or RRC Connection) for signaling regarding a plurality of CCs and manages UE context, which is connection information related to a terminal. In addition, the PCC is connected to the terminal and always exists in the active state in the RRC connected mode.

Secondary component carrier (SCC) refers to a CC corresponding to the secondary cell. That is, the SCC is a CC allocated to the terminal other than the PCC, and the SCC is an extended carrier for the additional resource allocation other than the PCC and may be divided into an activated or deactivated state.

The downlink component carrier corresponding to the primary cell is called a downlink primary component carrier (DL PCC), and the uplink component carrier corresponding to the primary cell is called an uplink major component carrier (UL PCC). In the downlink, the component carrier corresponding to the secondary cell is referred to as a DL secondary CC (DL SCC), and in the uplink, the component carrier corresponding to the secondary cell is referred to as an uplink secondary component carrier (UL SCC). Is called.

 The primary cell and the secondary cell have the following characteristics.

First, the primary cell is used for transmission of the PUCCH. Second, the primary cell is always activated, while the secondary cell is a carrier that is activated / deactivated according to specific conditions. Third, the primary cell always consists of a pair of DL PCC and UL PCC. Fourth, different CCs may be configured as primary cells for each UE. Fifth, procedures such as reconfiguration, adding, and removal of the primary cell may be performed by the RRC layer. In the addition of a new secondary cell, RRC signaling may be used to transmit system information of a dedicated secondary cell.

The DL CC may configure one serving cell, or the DL CC and the UL CC may be connected to configure one serving cell. However, the serving cell is not configured with only one uplink component carrier.

The activation / deactivation of the component carrier is equivalent to the concept of activation / deactivation of the serving cell. For example, assuming that serving cell 1 is configured with DL CC1, activation of serving cell 1 means activation of DL CC1. If the serving cell 2 assumes that DL CC2 and UL CC2 are connected and configured, activation of serving cell 2 means activation of DL CC2 and UL CC2. In this sense, each component carrier may correspond to a cell.

The number of component carriers aggregated between the downlink and the uplink may be set differently. The case where the number of downlink CCs and the number of uplink CCs are the same is called symmetric aggregation, and when the number is different, it is called asymmetric aggregation. In addition, the size (ie bandwidth) of the CCs may be different. For example, assuming that 5 CCs are used for a 70 MHz band configuration, 5 MHz CC (carrier # 0) + 20 MHz CC (carrier # 1) + 20 MHz CC (carrier # 2) + 20 MHz CC (carrier # 3) It may be configured as + 5MHz CC (carrier # 4).

The present invention will now be described. First, the problems that may occur when the prior art is described, and then the solution according to the present invention will be described.

In a carrier aggregation system, a base station may transmit parameters for determining a period (periodicity given in subframe units), an offset value, and the like for transmitting CSI for each serving cell through a higher layer signal. The UE can know the period, offset value, etc. for transmitting the CSI for each serving cell through these parameters. The UE may be semi-statically configured to feed back different periodic CSI through the PUCCH according to the PUCCH reporting mode set by the higher layer signal. The PUCCH reporting mode may also be referred to as a CSI reporting mode. The PUCCH reporting mode may exist in various ways as follows.

Type 1: CQI feedback on subbands selected by the UE

Type 1a: subband CQI, subband PMI feedback

Type 2, Type 2b, Type 2c: Wideband CQI, PMI Feedback

Type 2a: wideband PMI feedback

Type 3: RI feedback

Type 4: wideband CQI

Type 5: RI and Wideband PMI Feedback

Type 6: RI and PTI Feedback

The PUCCH reporting type payload size according to the PUCCH reporting mode and mode state is shown in the following table. The payload size refers to the information bit size of the CSI fed back through the PUCCH.

TABLE 3

The PUCCH reporting mode shown in Table 3 may refer to Section 7.2.2 of 3GPP TS 36.213 V10.1.0 (2011-03). In addition, a CSI report of a given PUCCH reporting type is transmitted through PUCCH resources given by a UE-specific higher layer signal for each serving cell.

In a carrier aggregation system, only CSI for one DL CC may be transmitted and CSI for the other DL CCs may be dropped according to a priority when a CSI collides in the same subframe. An example of priority in a CSI collision is as follows.

Type 1, 1a, 2, 2a, 2b, 2c, or 4 PUCCH reporting for the same serving cell as the above-described type 3, 5, or 6 PUCCH reporting for one serving cell collide with each other, type 1, PUCCH reporting of 1a, 2, 2a, 2b, 2c or 4 is dropped with low priority.

If two or more serving cells are configured for the UE, the UE transmits only CSI reporting for only one serving cell in a given subframe. In a given subframe, if there is a conflict between PUCCH reporting of type 3, 5, 6, or 2a of any serving cell and PUCCH reporting of type 1, 1a, 2, 2b, 2c or 4 of another serving cell, type 1, PUCCH reporting of 1a, 2, 2b, 2c or 4 has a lower priority and is dropped. If there is a conflict between PUCCH reporting of type 2, 2b, 2c, or 4 of any serving cell and PUCCH reporting of type 1 or 1a of another serving cell in a given subframe, PUCCH reporting of type 1 or 1a has a lower priority. Has and is dropped.

In addition, when a plurality of serving cells collide in a given subframe in a state of being set to a PUCCH reporting type having the same priority, the CSI of the serving cell having the lowest serving cell index ( ServCellIndex) is selected and the rest are dropped.

12 shows an example of selecting one serving cell in a situation where CSIs for a plurality of downlink DL CCs collide in a carrier aggregation system.

Referring to FIG. 12, in the first subframe 121, CSI for cell A, CSI for cell B, and CSI for cell C may collide. In this case, only the CSI for the cell C may be transmitted through the PUCCH of the first subframe 121 by priority.

In addition, the CSI for the cell A and the CSI for the cell B may collide in the second subframe 122. In this case, only the CSI for the cell A may be transmitted through the PUCCH of the second subframe 122 by priority.

As described above, when transmission timings of the CSI reports for each serving cell (more specifically, each DL CC) collide with each other, only the CSI report for one DL CC is transmitted according to the priority, and for the remaining DL CCs. CSI reports are not sent but dropped.

In addition, when the PUSCH transmission is performed in a subframe in which periodic CSI should be transmitted on the PUCCH, the UE may piggyback on the PUSCH without transmitting the periodic CSI on the PUCCH. In this case, as described above with reference to FIG. 9, the PUSCH resources may be multiplexed by puncturing, or may be multiplexed by occupying a part of the PUSCH resources and performing rate matching to transmit the PUSCH data to the remaining portions.

FIG. 13 shows an example of an activation / deactivation state of each serving cell in a situation in which a plurality of serving cells are configured for a terminal in a carrier aggregation system.

Referring to FIG. 13, in an LTE-A system, a base station may transmit and receive a plurality of CCs or a plurality of cells by setting them to the terminal through RRC. In this case, the base station may activate / deactivate some of the plurality of DL CCs set to RRC through signaling as necessary. For example, DL CC 0, DL CC 1, and DL CC 2 may be set to the UE by an RRC signal. In addition, DL CC 0 and DL CC 1 may be in an activated state, and DL CC 2 may be in an inactive state.

In this case, according to the prior art, the UE reports CSI for DL CC 0 and DL CC 1 in an activated state, but does not report CSI for DL CC 2 in an inactive state. That is, the terminal transmits only the CSI for the activated DL CC among the plurality of configured DL CCs and does not transmit the CSI for the deactivated DL CC.

However, an error may occur in transmission / reception of activation / deactivation signaling for the DL CC between the base station and the terminal. Alternatively, an error may occur at the time of activation / deactivation of the DL CC. In this case, a misrecognition may occur between the base station and the terminal as to whether the specific DL CC is activated.

14 illustrates an example in which a misperception occurs on whether to activate a DL CC between a base station and a terminal.

Referring to FIG. 14, the base station configures DL CC 0, DL CC 1, and DL CC 2 to the terminal, and then activates only DL CC 0. On the other hand, the UE may recognize that DL CC 0 and DL CC 1 are activated among three DL CCs.

If the priority among the three DL CCs is set in order of DL CC 1 (CC 1), DL CC 0 (CC 0), DL CC 2 (CC 2), and the three DL CCs in the same subframe Assume that CSI reporting is set for. Then, since the base station recognizes that DL CC 1 is in an inactive state, it will recognize that CSI for DL CC 0 having the next priority is reported. On the other hand, since the UE recognizes that DL CC 1 is in an active state, it will report CSI for DL CC 1 having the highest priority. Thus, a mismatch occurs between the base station and the terminal with respect to the object of CSI reporting.

In addition, a problem may occur in the data transmitted in the PUSCH as well as the inconsistency of the DL CC that is the target of CSI reporting. For example, in case of a UE that does not support simultaneous PUCCH and PUSCH transmission or is not configured for simultaneous transmission, when the PUSCH transmission is performed in a subframe in which PUCCH transmission is scheduled, periodic CSI is piggybacked on the PUSCH and transmitted. In this case, the number of CSI payload bits varies according to the CSI reporting type, the type of CSI, and the like, thereby changing the number of coded bits. Therefore, if the number of CSI payload bits and the CSI types of the DL CC 0 and the DL CC 1 are different from each other, the number of bits to be multiplexed or rate matched for data transmitted through the PUSCH is changed. As a result, inconsistency occurs in transmitting and receiving PUSCH data between the base station and the terminal.

For example, if the corresponding CSI is a type (eg, CQI, PMI, RI, PTI, etc.) multiplexed with the PUSCH data through rate matching, the base station may misunderstand the coded bit alignment order of the PUSCH data. It can cause a fatal error in the HARQ combining operation.

In addition, misrecognition of the number of CSI payload bits may also occur when multiplexing DL HARQ ACK / NACK and CSI through PUCCH.

FIG. 15 illustrates an example of transmitting ACK / NACK and CSI through joint coding through PUCCH format 3. FIG.

Referring to FIG. 15, when the number of input bits of the RM encoder is 11 bits or less due to the limitation of the RM code and basis sequence defined in PUCCH format 3, one RM code is used. On the other hand, when the number of input bits of the RM encoder exceeds 11 bits, the maximum number of input bits of 22 bits can be processed using two RM codes.

In this case, the bit field is configured in accordance with the set number of ACK / NACK bits. In contrast, the number of CSI bits is configured based on the activated cells. Therefore, when an error occurs regarding activation / deactivation of a specific cell, the UE recognizes that the number of bits of ACK / NACK + CSI exceeds 11 bits, and performs channel coding using two RM codes, and the base station performs ACK / The decoding may be performed assuming that the channel coding is performed using one RM code by recognizing that the number of NACK + CSI bits is 11 bits or less.

In the case of using one RM code and using two RM codes, there are problems in decoding not only CSI but also ACK / NACK bits because the number of encoding bits and resource element mapping are different.

Now, a method for solving the above problems will be described. In the following, CSI includes CSI transmitted for all periodic CSI or DL CCs in an activated state (eg, CQI / PMI, RI, PTI, etc.). In addition, the control information (for example, ACK / NACK) and CSI transmitted regardless of the activation / deactivation state of the serving cell may be applied to the multiplexed transmission. In addition, the CSI may be a periodic CSI of a type that is multiplexed with the PUSCH through rate matching. In addition, CSI may be CSI in the case of multiplexing ACK / NACK and CSI using a single RM or two RM codes in PUCCH format 3.

16 shows a CSI transmission method according to an embodiment of the present invention.

Referring to FIG. 16, the terminal receives configuration information on a plurality of serving cell assignments from a base station (S110). Configuration information for the plurality of serving cell assignments may be transmitted in an RRC message.

The terminal receives the activation / deactivation information for each serving cell from the base station (S120).

The terminal determines the size of the CSI reporting field based on the configured serving cells (S130). Here, the CSI reporting field may be referred to as the size of the CSI information bit. The UE determines the size of the CSI reporting field for all of the configured serving cells instead of determining the size of the CSI reporting field by comparing priorities with only active serving cells as in the prior art. A detailed method of determining the size of the CSI reporting field will be described later in detail.

The terminal generates the CSI according to the priority among the activated serving cells (S140). That is, the size of the CSI reporting field is determined based on the set serving cells, but the CSI itself may be generated according to the priority among the activated serving cells. Alternatively, the terminal may generate the CSI according to the priority among the configured serving cells. This process will be described later in detail.

The terminal transmits the CSI according to the determined number of CSI reporting field bits (S150). The CSI may be transmitted on the PUCCH or may be piggybacked on the PUSCH and transmitted. In particular, when the CSI is piggybacked and transmitted to the PUSCH, according to the present invention, misunderstanding of the payload bit number (ie, the number of CSI reporting field bits) of the CSI does not occur between the base station and the terminal. Therefore, there is no problem in decoding the PUSCH data because no misrecognition occurs in rate matching for the PUSCH data between the base station and the terminal.

Now, a method of determining the size of the CSI reporting field in FIG. 16 will be described in detail.

17 illustrates a situation applied to FIGS. 18 to 21.

Referring to FIG. 17, DL CC 0, DL CC 1, DL CC 2, and DL CC 3 are set in a terminal according to configuration information on a plurality of serving cell assignments, and DL CC 0 and DL in the same subframe. Assume that the CSI reports for CC 1 and DL CC 2 are in conflict. That is, DL CC 3 is in a state in which a CSI report is not scheduled in the same subframe. In addition, it is assumed that a state has priority in order of CSI for DL CC 1, CSI for DL CC 0, and CSI for DL CC 2. And, it is assumed that the base station recognizes the deactivated state for DL CC 1 but the terminal recognizes the activated state due to an error.

Method 1. A method of determining a size of a CSI reporting field according to priority among CSIs of different DL CCs colliding in the same subframe.

18 shows an application example of Method 1 above.

Referring to FIG. 18, DL CCs in which collision occurs in the same subframe among DL CC 0 to DL CC 3 configured for the UE are DL CC 0 to DL CC 2. At this time, the size of the CSI reporting field is determined according to the priority. That is, the base station assumes that the size of the CSI reporting field is determined to be 6 bits, which is the number of CSI bits in the DL CC 1 even though the DL CC 1 is inactive because the CSI of the DL CC 1 has the highest priority. Since the CSI of DL CC 1 has the highest priority, the UE also assumes that the size of the CSI reporting field is determined to be 6 bits, which is the number of CSI bits of DL CC 1.

In other words, the size of the channel state information reporting field may be determined as the number of bits of channel state information for the serving cell determined according to the priority among the set serving cells scheduled to transmit the channel state information at the same time in the same subframe.

Method 2. A method of determining a size of a CSI reporting field according to a maximum number of CSI bits among CSIs of different DL CCs colliding in the same subframe.

19 shows an application example of Method 2 above.

Referring to FIG. 19, DL CCs in which collision occurs in the same subframe among DL CC 0 to DL CC 3 configured for the UE are DL CC 0 to DL CC 2. In this case, the number of CSI reporting field bits is determined as the maximum number of bits among the CSI bits of each DL CC without comparing the priority of the CSIs for the respective DL CCs. For example, if the number of CSI bits for DL CC 0 is 8 bits, the number of CSI bits for DL CC 1 is 6 bits, and the number of CSI bits for DL CC 2 is 11 bits, the number of bits for CSI for DL CC 2 is Since it is the largest of 11 bits, the number of CSI reporting field bits is determined to be 11 bits.

In other words, the size of the channel state information reporting field is the number of bits of the channel state information of the serving cell that transmits the channel state information at the maximum number of bits in the same subframe among the set serving cells scheduled to transmit the channel state information at the same time in the same subframe. Can be determined.

Method 3. A method of determining the maximum value as the number of CSI reporting field bits by comparing the maximum number of CSI bits that can be transmitted according to the CSI reporting mode among DL CCs configured to the UE.

20 shows an application example of Method 3 above.

Referring to FIG. 20, DL CCs to which CSI transmission collides in the same subframe are DL CC 0 to DL CC 2. In this case, rather than comparing the number of CSI bits of each DL CC in the same subframe, the maximum number of CSI bits that can be transmitted is compared according to the CSI reporting mode of each DL CC. For example, assume that the number of CSI bits in DL CC 0 is 8 bits, the number of CSI bits in DL CC 1 is 6 bits, and the number of CSI bits in DL CC 3 is 6 bits in subframe #N. According to the CSI reporting mode, the maximum number of CSI bits that can be transmitted in DL CC 0 is 6 bits, 6 bits in DL CC 1, 8 bits in DL CC 2, and 10 bits in DL CC 3. In this case, the number of CSI reporting field bits selected in the subframe #N becomes 10 bits. Therefore, it is not necessary to compare the CSI priority of each DL CC in a subframe in which collision occurs.

In other words, the size of the channel state information reporting field may be determined as the number of bits of channel state information of the serving cell transmitting the channel state information with the maximum number of bits regardless of subframes among the set serving cells.

Further simplifying this method, the size of the maximum CSI reporting field transmitted in one subframe may be fixed to a specific value (ie, the maximum number of CSI bits, for example, 11 bits) for all CSI reporting modes. Alternatively, dual RMs may always be used for simultaneous transmission of ACK / NACK and CSI.

Method 4. Determining the maximum number of CSI bits among the CSIs of the secondary cell and the CSIs of the primary cell except the CSI having a lower priority than the CSI of the primary cell among the CSIs colliding in the same subframe, the number of CSI reporting field bits How to.

21 shows an application example of Method 4 above.

Referring to FIG. 21, DL CC 0 is a primary cell and the remaining DL CCs are secondary cells. And, it is assumed that the order of priority is CSI for DL CC 1, CSI for DL CC 0, and CSI for DL CC 2.

In this case, the CSI for DL CC 2, which is the secondary cell, has a lower priority than the CSI for DL CC 0, which is the primary cell. Thus, CSI for DL CC 2 is excluded. Thereafter, the number of CSI bits for DL CC 0 and the number of CSI bits for DL CC 1 are compared to determine the maximum value as the number of CSI reporting field bits. In FIG. 21, since the number of CSI bits of DL CC 0 is 8 bits and the number of CSI bits of DL CC 1 is 6 bits, 8 bits are determined as the number of CSI reporting field bits.

In other words, the size of the channel state information reporting field is the number of bits of the channel state information bits of the secondary cell having a higher priority than the channel state information of the primary cell among the set serving cells scheduled to simultaneously transmit the channel state information in the same subframe. It may be determined as a larger value among the number of bits of channel state information of the primary cell.

And, if there is no CSI of the primary cell, it can operate as in Method 2. That is, the size of the CSI reporting field is determined according to the maximum number of CSI bits among the CSIs of secondary cells colliding in the same subframe.

According to this method, since the CSIs of the secondary cell having a lower priority than the CSI of the primary cell are excluded from the CSI bit number comparison, it is possible to prevent an unnecessary increase in the number of CSI reporting field bits. Since the primary cell is always active, it is essential to include the primary cell in the CSI bit number comparison when there is CSI for the primary cell.

Now, a method of determining the content of the CSI actually transmitted through the CSI reporting field determined by any one of the methods 1 to 4 will be described. That is, the step of 'generating CSI according to priority' of FIG. 16 will be described in detail.

1. The UE may transmit the CSI determined according to the priority among the CSIs for the DL CCs activated in the subframe in which the collision occurs to the base station. In this case, since there may be a misperception about the activation / deactivation state between the base station and the terminal, misunderstanding may occur in the target of the CSI. However, there is no misunderstanding of the size of the CSI reporting field. Therefore, even if the PSI is piggybacked and the CSI is transmitted, there is no problem in PUSCH data decoding. If the size of the CSI reporting field is larger than the actual CSI bit, the actual CSI may map from the most significant bit (MSB) of the CSI reporting field and pad the remaining bits with '0'.

2. The terminal may transmit the CSI determined according to the priority among the configured DL CCs (including the deactivated DL CCs) to the base station instead of the activated DL CCs. For example, in FIG. 19, the CSI reporting field determined to be 11 bits is loaded with CSI (6 bits) for DL CC 1. When using this method, it may also occur when reporting the CSI for the deactivated DL CC.

3. The UE reports the scheduled CSI if the CSI of the DL CC selected by the method 2. is for the activated DL CC, and if the CSI of the selected DL CC is for the deactivated DL CC, a dummy value or Send a null value. Alternatively, if the size of the CSI reporting field determined in Method 1 is larger than the number of bits of the actual CSI selected by the method of the above method, the CSI is transmitted as in the method of the above method. Send it.

In addition, when the CSI is piggybacked and transmitted on the PUSCH, the payload bit number of the CSI is maintained so that the PUSCH data rate matching operation is not affected.

The following table shows CQI index values as an example of CSI used for CSI reporting on an activated DL CC.

TABLE 4

In Table 4, the CQI index '0' indicates that the channel state is not good enough to properly receive a signal through the corresponding DL CC. In the case of using the present invention in a carrier aggregation system, the CQI index '0' may be used when the selected DL CC is in an inactive state.

22 is a block diagram illustrating a base station and a terminal in which an embodiment of the present invention is implemented.

The base station 100 includes a processor 110, a memory 120, and a radio frequency unit (RF) 130. The processor 110 implements the proposed functions, processes and / or methods. For example, the processor 110 may transmit configuration information on serving cell allocation to an MS through an upper layer signal such as an RRC message, and transmit activation information indicating activation of each serving cell. In addition, the CSI report can be received from the terminal. Layers of the air interface protocol may be implemented by the processor 110. 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. Layers of the air interface protocol may be implemented by the processor 210. The processor 210 receives configuration information of the serving cells and receives activation information indicating whether the serving cell is activated. In addition, the size of the CSI reporting field is determined based on the set serving cells, and the actual CSI to be transmitted is determined and then transmitted. This process has been described with reference to FIGS. 16 to 21. 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, and / or data processing devices. 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 a baseband circuit for processing 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. In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Claims (11)

1. In a method for transmitting channel state information (CSI) performed by a terminal in a carrier aggregation system in which a plurality of serving cells are configured,
   Receive configuration information on a plurality of serving cell assignments to determine configured serving cells,
   Receiving activation information indicating whether each of the set serving cells is activated, and determining at least one activated serving cell among the set serving cells,
   Determine a size of a channel state information reporting field based on the set serving cells,
   Generate channel status information according to priority, and
   And transmitting the generated channel state information through the channel state information reporting field of the determined size.
2. The method of claim 1, wherein the size of the channel state information reporting field is
   And determining the number of bits of channel state information for the serving cell determined according to a predetermined rule among the set serving cells, wherein the set serving cells include an active serving cell and an inactive serving cell.
3. The method of claim 2, wherein the size of the channel state information reporting field is
   And determining the number of bits of the channel state information for the serving cell determined according to the predetermined rule among the set serving cells scheduled to transmit the channel state information at the same time in the same subframe.
4. The method of claim 2, wherein the size of the channel state information reporting field is
   And determining the number of bits of channel state information of the serving cell transmitting the channel state information with the maximum number of bits in the same subframe among the set serving cells scheduled to transmit channel state information at the same time in the same subframe.
5. The method of claim 2, wherein the size of the channel state information reporting field is
   And determining the number of bits of channel state information of the serving cell that transmits channel state information at the maximum number of bits regardless of subframes among the set serving cells.
6. The method of claim 5, wherein the size of the channel state information reporting field is
   Characterized in that it is given a constant value.
7. The method of claim 2, wherein the size of the channel state information reporting field is
   Among the set serving cells scheduled to transmit channel state information simultaneously in the same subframe, the larger of the number of bits of channel state information of the secondary cell having a higher priority than the channel state information of the primary cell and the number of bits of channel state information of the primary cell Characterized in that the value is determined.
8. The method of claim 1, wherein the channel state information generated according to the priority is generated according to the priority among channel state information for the at least one active serving cell.
9. The method of claim 1, wherein the channel state information generated according to the priority is generated according to the priority among channel state information for the set serving cells.
10. The method of claim 1, wherein the channel state information includes at least one of a channel quality indicator (CQI) indicating channel quality, a precoding matrix index (PMI) indicating a precoding matrix, and a rank indicator (RI) indicating the number of layers recommended by the terminal. A method comprising one.
11. RF (Radio Frequency) unit for transmitting or receiving a radio signal; And
    Including a processor connected to the RF unit,
    The processor receives configuration information on a plurality of serving cell assignments to determine configured serving cells,
    Receiving activation information indicating whether each of the set serving cells is activated, and determining at least one activated serving cell among the set serving cells,
    Determine a size of a channel state information reporting field based on the set serving cells,
    Generate channel status information according to priority, and
    And transmitting the generated channel state information through the channel state information reporting field of the determined size.

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