KR20090083269A - Method for searching pdcch in wireless communication - Google Patents

Abstract

A method for searching a PDCCH in a wireless communication is provided to reduce the overhead caused by blind decoding and shorten the time taken for the search of the PDCCH that a terminal requires. A terminal demaps physical resources elements into a CCE(Control Channel Elements)(S210), and demodulates a CCE aggregation level(S220). The terminal dematches the demodulated data with a transmission rate according to the correspondent payload and the CCE aggregation level(S230). The error occurrence is detected based on the CRC(Cyclic Redundancy Check) of encoded data(S240), and the terminal that detects its PDCCH(Physical Downlink Control Channel) removes the CRC from the decoded data and obtains the necessary control information(S250).

Description

METHOD FOR SEARCHING PDCCH IN WIRELESS COMMUNICATION}

The present invention relates to wireless communication, and more particularly, to a PDCCH retrieval method for efficient detection of control information.

In a wireless communication system, generally, one base station provides a service to a plurality of terminals. The base station schedules user data for a plurality of terminals, and transmits control information including scheduling information for the user data together with the user data. In general, a channel carrying the control information is called a control channel, and a channel carrying user data is called a data channel. The terminal monitors the control channel to find its control information and processes its data using the control information. Monitoring means that the terminal attempts to decode the control channel candidates.

In order for the terminal to receive user data allocated to the terminal, control information on user data on a control channel must be received. However, in a given bandwidth, control information of a plurality of terminals is generally multiplexed within one transmission interval. That is, the base station multiplexes control information for a plurality of terminals and transmits them through a plurality of control channels in order to provide services to the plurality of terminals. The terminal finds its own control channel among the plurality of control channels.

One of techniques for detecting specific control information among the multiplexed control information is blind decoding. In the blind decoding, the terminal attempts to recover the control channel using various combinations of information in a state where there is no information necessary for restoring the control channel. That is, the terminal does not know whether the control information transmitted from the base station is its own control information, and decodes all the given control information until the terminal finds its own control information without knowing where its control information is located. . In order to determine whether the terminal is its own control information, the unique information of the terminal may be used. For example, when the base station multiplexes control information of each terminal, the base station may mask and transmit a unique identifier of each terminal to a cyclic redundancy check (CRC). CRC is a code used for error detection. After demasking the unique identifier of the received control information to the CRC of the received control information, the CRC check may determine whether or not the control information.

If the terminal does not correctly detect its control information from the multiplexed control information, it is not possible to decode the user data on the data channel. Therefore, it can be said that the fast and accurate detection of control information has a significant effect on the performance of the entire system. However, simple blind decoding may have difficulty in detecting control information.

Since each terminal may require different control information, and a channel encoding method using a different code rate may be used, the size of the control information may be different for each terminal. Therefore, the number of blind decoding attempts in the control region in which the control information is transmitted may be unexpectedly increased. As the number of detection attempts increases, battery consumption of the terminal increases.

Accordingly, there is a need for an efficient control channel search method capable of reducing battery consumption of a terminal by reducing the number of detection attempts to quickly detect control information.

An object of the present invention is to provide an efficient PDCCH search method.

In one aspect, there is provided a PDSCH (Pysical Downlink Control Channel) search method in a wireless communication system. The method includes setting a transmission mode used for receiving downlink data over a physical downlink shared channel (PDSCH) associated with downlink control information (DCI) signaled by a PDCCH, and the format of the DCI is determined in the transmission mode. Subordinately searching for the PDCCH in the search space by monitoring at least one PDCCH candidate in the search space, wherein the PDCCH is transmitted through a group of one or several CCEs (Control Channel Element). The DCI is mapped to at least one CCE, and the aggregation level is a collection of CCEs for one DCI, wherein the search space composed of at least one PDCCH for monitoring is adjacent to the CCEs in the control region of the subframe. Defined as a set, wherein the control region consists of N _CCE CCEs, and the search space is from a starting point in the control region. Beginning, the starting point is a function of the aggregation level, N _CCE, and a User Equipment Identity (UE ID).

In another aspect, a method of transmitting DCI in a wireless communication system is provided. The method includes setting a transmission mode used for receiving downlink data on a PDSCH associated with a DCI signaled by a PDCCH, and a format of the DCI depends on the transmission mode, wherein the DCI is transmitted through the PDCCH. Wherein the PDCCH is transmitted through a population that is one or several CCEs, the DCI is mapped to at least one CCE, and the population level is a collection of CCEs for one DCI.

The terminal can efficiently monitor the downlink control channel. In addition, the base station can efficiently multiplex and transmit a plurality of control channels carrying control information for a plurality of terminals. Through this, the number of detection attempts due to blind decoding for monitoring the downlink control channel can be reduced. The overhead of blind decoding is reduced, and the time required for the UE to find the downlink control channel required by the UE is reduced. The battery consumption of the terminal can be reduced, and the performance of the entire system can be expected.

1 is a block diagram illustrating a wireless communication system. This may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may be referred to as a Long Term Evolution (LTE) system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) includes a base station (BS) 20 that provides a control plane and a user plane.

The UE 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, and the like. The base station 20 generally refers to a fixed station communicating with the terminal 10, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), and an access point. have. One base station 20 may provide a service for at least one cell. The cell is an area where the base station 20 provides a communication service. An interface for transmitting user traffic or control traffic may be used between the base stations 20. Hereinafter, downlink means communication from the base station 20 to the terminal 10, and uplink means communication from the terminal 10 to the base station 20.

The base stations 20 may be connected to each other through an X2 interface. The base station 20 is connected to an Evolved Packet Core (EPC), more specifically, a Mobility Management Entity (MME) / Serving Gateway (S-GW) 30 through an S1 interface. The S1 interface supports a many-to-many-relation between base station 20 and MME / S-GW 30.

2 is a block diagram illustrating a functional split between an E-UTRAN and an EPC. The hatched box represents the radio protocol layer and the white box represents the functional entity of the control plane.

Referring to FIG. 2, the base station performs the following function. (1) Radio Resource Management such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic Resource Allocation to UE RRM), (2) Internet Protocol (IP) header compression and encryption of user data streams, (3) routing of user plane data to S-GW, and (4) paging messages. Scheduling and transmission, (5) scheduling and transmission of broadcast information, and (6) measurement and measurement report setup for mobility and scheduling.

The MME performs the following functions. (1) Non-Access Stratum (NAS) signaling, (2) NAS signaling security, (3) Idle mode UE Reachability, (4) Tracking Area list management , (5) Roaming, (6) Authentication.

S-GW performs the following functions. (1) mobility anchoring, (2) lawful interception. P-GW (P-Gateway) performs the following functions. (1) terminal IP (allocation) allocation (allocation), (2) packet filtering.

3 is a block diagram illustrating elements of a terminal. The terminal 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit 55. . The processor 51 is implemented with layers of the air interface protocol to provide a control plane and a user plane. The functions of each layer may be implemented through the processor 51. The memory 52 is connected to the processor 51 to store a terminal driving system, an application, and a general file. The display unit 54 displays various information of the terminal, and may use well-known elements such as liquid crystal display (LCD) and organic light emitting diodes (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The RF unit 53 is connected to a processor and transmits and / or receives a radio signal.

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

4 is a block diagram illustrating a radio protocol architecture for a user plane. 5 is a block diagram illustrating a radio protocol structure for a control plane. This shows the structure of the air interface protocol between the terminal and the E-UTRAN. The user plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

4 and 5, a physical layer (PHY), which is a first layer, provides an information transfer service to a higher layer using a physical channel. The physical layer is connected to the upper Media Access Control (MAC) layer through a transport channel, and data between the MAC layer and the physical layer moves through this transport channel. Data moves between physical layers between physical layers, that is, between physical layers of a transmitting side and a receiving side.

The MAC layer of the second layer provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The RLC layer of the second layer supports reliable data transmission. In the RLC layer, there are three operation modes according to a data transmission method: transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). The AM RLC provides a bidirectional data transmission service, and supports retransmission when an RLC Protocol Data Unit (PDU) fails to transmit.

The Packet Data Convergence Protocol (PDCP) layer of the second layer performs a header compression function to reduce the IP packet header size.

The radio resource control (RRC) layer of the third layer is defined only in the control plane. The RRC layer is responsible for controlling logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers (hereinafter, RBs). RB means a service provided by the second layer for data transmission between the UE and the E-UTRAN. If there is an RRC connection (RRC Connection) between the RRC of the terminal and the RRC of the network, the terminal is in the RRC Connected Mode, otherwise it is in the RRC Idle Mode.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

6 shows a mapping between a downlink logical channel and a downlink transport channel. This includes 3GPP TS 36.300 V8.3.0 (2007-12) Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; See section 6.1.3.2 of Stage 2 (Release 8).

Referring to FIG. 6, a paging control channel (PCCH) is mapped to a paging channel (PCH), and a broadcast control channel (BCCH) is mapped to a broadcast channel (BCH) or a downlink shared channel (DL-SCH). Common Control Channel (CCCH), Dedicated Control Channel (DCCH), Dedicated Traffic Channel (DTCH), Multicast Control Channel (MCCH) and Multicast Traffic Channel (MTCH) are mapped to DL-SCH. MCCH and MTCH are also mapped to MCH (Multicast Channel).

Each logical channel type is defined by what kind of information is transmitted. There are two types of logical channels: control channels and traffic channels.

The control channel is used for transmission of control plane information. BCCH is a downlink channel for broadcasting system control information. PCCH is a downlink channel that transmits paging information and is used when the network does not know the location of the terminal. CCCH is a channel for transmitting control information between the terminal and the network, and is used when the terminal does not have an RRC connection with the network. The MCCH is a point-to-multipoint downlink channel used for transmitting multimedia broadcast multicast service (MBMS) control information and is used for terminals receiving MBMS. DCCH is a point-to-point unidirectional channel for transmitting dedicated control information between the terminal and the network, and is used by a terminal having an RRC connection.

The traffic channel is used for transmission of user plane information. DTCH is a point-to-point channel for transmitting user information and exists in both uplink and downlink. MTCH is a point-to-many downlink channel for transmission of traffic data, and is used for a terminal receiving an MBMS.

Transport channels are classified according to how and with what characteristics data is transmitted over the air interface. The BCH has a predefined transmission format that is broadcast and fixed in the entire cell area. The DL-SCH supports hybrid automatic repeat request (HARQ), dynamic link adaptation by changing modulation, coding and transmission power, possibility of broadcasting, possibility of beamforming, and dynamic / semi-static resources. It is characterized by allocation support, discontinuous reception (DRX) support for UE power saving, and MBMS transmission support. PCH is characterized by DRX support for terminal power saving and broadcast to the entire cell area. The MCH is characterized by broadcast to the entire cell area and MBMSN (MBMS Single Frequency Network) support.

7 shows mapping between a downlink transport channel and a downlink physical channel. This may be referred to Section 5.3.1 of 3GPP TS 36.300 V8.3.0 (2007-12).

Referring to FIG. 7, a BCH is mapped to a physical broadcast channel (PBCH), an MCH is mapped to a physical multicast channel (PMCH), and a PCH and DL-SCH are mapped to a physical downlink shared channel (PDSCH). PBCH carries the BCH transport block, PMCH carries the MCH, and PDSCH carries the DL-SCH and PCH.

There are several downlink physical control channels used in the physical layer. The physical downlink control channel (PDCCH) informs the UE about resource allocation of the PCH and DL-SCH and HARQ information related to the DL-SCH. The PDCCH may carry an uplink scheduling grant informing the UE of resource allocation of uplink transmission. The physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for transmission of PDCCHs in a subframe. PCFICH is transmitted every subframe. PHICH (physical Hybrid ARQ Indicator Channel) carries a HARQ ACK / NAK signal in response to uplink transmission.

8 shows the structure of a radio frame.

Referring to FIG. 8, a radio frame consists of 10 subframes, and one subframe consists of two slots. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

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

9 is an exemplary diagram illustrating a resource grid for one downlink slot.

Referring to FIG. 9, the downlink slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain. Here, one downlink slot includes 7 OFDM symbols and one resource block includes 12 subcarriers in the frequency domain, but is not limited thereto.

Each element on the resource grid is called a resource element (RE), and one resource block includes 12 × 7 resource elements. The number N ^DL of resource blocks included in the downlink slot depends on the downlink transmission bandwidth set in the cell.

10 shows the structure of a subframe.

Referring to FIG. 10, a subframe includes two consecutive slots. The maximum 3 OFDM symbols of the first slot in the subframe are the control region to which the PDCCH is allocated, and the remaining OFDM symbols are the data region to which the PDSCH is allocated. In addition to the PDCCH, the control region may be allocated a control channel such as PCFICH and PHICH. The UE may read the data information transmitted through the PDSCH by decoding the control information transmitted through the PDCCH. Here, it is merely an example that the control region includes 3 OFDM symbols. The number of OFDM symbols included in the control region in the subframe can be known through the PCFICH.

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

A plurality of multiplexed PDCCHs for a plurality of terminals may be transmitted in a control region. The PDCCH carries control information such as scheduling assignment. The PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). Hereinafter, the number of CCEs used for PDCCH transmission is referred to as a CCE aggregation level. For example, the CCE aggregation level may be an element of {1, 2, 4, 8}. The CCE aggregation level is the number of CCEs used for PDCCH transmission and is a CCE unit for searching for a PDCCH. The size of the CCE aggregation level is defined by the number of adjacent CCEs. Each UE may have a different CCE aggregation level. For example, in FIG. 10, the CCE aggregation level L of the second, fourth, and sixth terminals UE 2, UE4, and UE6 is 1. The CCE aggregation level L of the third and fifth UEs UE 3 and UE 5 is 2, and the CCE aggregation level L of the first and seventh UEs UE 1 and UE 7 is 4.

The reason why the CCE aggregation level is different for each UE is because a format or a modulation and coding scheme (MCS) level of control information carried on the PDCCH is different.

First, the format of the control information will be described. Control information transmitted through the PDCCH is referred to as downlink control information (DCI). The DCI transmits uplink or downlink scheduling information, an uplink power control command, control information for paging, control information for indicating a random access response, and the like. According to the DCI format, the configuration of information carried in the PDCCH payload may vary. The PDCCH payload is an information bit.

The DCI format includes format 0 for PUSCH scheduling, format 1 for scheduling one physical downlink shared channel (PDSCH) codeword, and format 1A for compact scheduling of one PDSCH codeword. Format 1C for very simple scheduling of DL-SCH (Downlink Shared Channel); format 2 for open-loop spatial multiplexing mode for PDSCH scheduling in closed-loop spatial multiplexing mode There are formats 2A for PDSCH scheduling and formats 3 and 3A for transmission of a transmission power control (TPC) command for an uplink channel. DCI format 1A may be used for PDSCH scheduling, regardless of which transmission mode is configured for the UE.

The PDCCH payload length may vary depending on the DCI format. In addition, the type and length thereof of the PDCCH payload may vary depending on whether it is a simple scheduling or a transmission mode set in the terminal.

The transmission mode may be configured for the UE to receive downlink data through the PDSCH. For example, the downlink data through the PDSCH may include scheduled data, paging, random access response, or broadcast information through BCCH. Downlink data through the PDSCH is related to the DCI format signaled through the PDCCH. The transmission mode may be set semi-statically to the terminal through higher layer signaling. For example, higher layer signaling is RRC signaling.

The transmission mode may be classified into single antenna transmission or multi-antenna transmission. The terminal is set to a semi-static transmission mode through higher layer signaling. For example, multi-antenna transmission includes transmit diversity, open-loop or closed-loop spatial multiplexing, and multi-user-multiple input multiple outputs. ) Or beamforming. Transmit diversity is a technique of increasing transmission reliability by transmitting the same data in multiple transmit antennas. Spatial multiplexing is a technology that allows high-speed data transmission without increasing the bandwidth of the system by simultaneously transmitting different data from multiple transmit antennas. Beamforming is a technique of increasing the signal to interference plus noise ratio (SINR) of a signal by applying weights according to channel conditions in multiple antennas.

The DCI format is dependent on a transmission mode configured in the terminal (depend on). The UE has a reference DCI format that monitors according to a transmission mode configured for the UE. The following table shows an example of a reference DCI format according to a transmission mode configured in a terminal. This is for illustrative purposes only and is not a limitation.

Transmission mode Reference DCI Format Single-antenna port; port 0 1, 1A Transmit diversity 1, 1A Open-loop spatial multiplexing 2A Closed-loop spatial multiplexing 2 Multi-user MIMO To Be Determined Closed-loop Rank = 1 precoding 1B Single-antenna port; port 5 1, 1A

A terminal set as a single antenna port having a transmission mode of port 0 or 5 or a terminal set to transmit diversity may receive control information of DCI format 1 or 1A. The terminal in which the transmission mode is set to open-loop spatial multiplexing may receive control information of DCI format 2A, and the terminal in closed-loop spatial multiplexing may receive control information of DCI format 2. A terminal having a transmission mode set to precoding having a closed loop rank 1 may receive control information of DCI format 1B.

The UE having no transmission mode configured may receive downlink data related to control information of DCI format 1A through PDCCH through PDSCH.

Next, the relationship between the MCS level and the CCE aggregation level will be described.

MCS level refers to a code rate and a modulation order used for data coding. Adaptive MCS levels are used for link adaptation. In general, three to four MCS levels may be considered in a control channel for transmitting control information.

The reason why the CCE aggregation level is different for each UE is because the code rate and modulation sequence of the control information are different. For example, when the modulation sequence is 2, Binary Phase Shift Keying (BPSK) is used, and when the modulation sequence is 4, Quadrature Phase Shift Keying (QPSK) is used. If the modulation sequence is 6, 16 Quadrature Amplitude Modulation (QAM) is used. Alternatively, even if the modulation sequence of the control information is fixed for each terminal and only the code rate is different, the CCE aggregation level may be different for each terminal. That is, the reason why the CCE aggregation level is different for each UE is because the MCS level carried on the PDCCH is different.

For example, assume that the MCS level uses only one QPSK as the modulation sequence and uses 2/3, 1/3, 1/6, or 1/12 as the code rate. The PDCCH carrying control information whose MCS level uses a code rate of 2/3 has a CCE aggregation level of 1 in basic length units. The PDCCH carrying control information whose MCS level uses a code rate 1/3 is twice the length of a basic length unit. That is, the CCE aggregation level is two. The PDCCH carrying control information whose MCS level uses code rate 1/6 is four times the length of the basic length unit. That is, the CCE aggregation level is four. The PDCCH carrying control information whose MCS level uses a code rate of 1/12 is 8 times the length of the basic length unit. That is, the CCE aggregation level is eight.

The format of the PDCCH and the number of bits of the PDCCH are determined according to the CCE aggregation level. The PDCCH format may be determined by the MCS level. The following table shows an example of the format of the PDCCH according to the CCE aggregation level, and the number of bits of the PDCCH available.

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

11 is a flowchart showing the configuration of a PDCCH.

Referring to FIG. 11, the base station configures a PDCCH payload according to an information payload format to be sent to the terminal. The length of the PDCCH payload may vary depending on the information payload format. The information payload format may be a DCI format. The base station may select the MCS level and determine the PDCCH format, that is, the CCE aggregation level, according to the MCS level.

In step S110, a cyclic redundancy check (CRC) for error detection is added to each PDCCH payload. In the CRC, an identifier (referred to as a Radio Network Temporary Identifier (RNTI)) 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. That is, the CRC may be scrambled together with the unique identifier of the terminal. Alternatively, if the PDCCH is for a paging message transmitted through the PCH, a paging identifier, for example, P-RNTI (P-RNTI) may be masked to the CRC. If the PDCCH is for system information transmitted through the DL-SCH, a system information identifier, for example, a System Information-RNTI (SI-RNTI) may be masked to the CRC. If the PDCCH is for indicating a random access response that is a response to the transmission of the random access preamble of the UE, a random access-RNTI (RA-RNTI) may be masked to the CRC. The following table shows examples of identifiers masked on the PDCCH.

Type Identifier Description UE-specific C-RNTI used for a unique UE identification  Common P-RNTI used for paging message SI-RNTI used for system information RA-RNTI used for random access response

If C-RNTI is used, the PDCCH carries control information for a specific UE. If another RNTI is used, the PDCCH carries common control information received by all UEs in a cell.

In step S120, the coded control information is generated by performing channel coding on the control information added with the CRC. In this case, channel coding may be performed at a code rate according to the MCS level. In step S130, rate matching according to the CCE aggregation level allocated to the PDCCH format is performed.

In step S140, the coded data is modulated to generate modulation symbols. At this time, a modulation sequence according to the MCS level can be used. The modulation symbols constituting one PDCCH may have one of 1, 2, 4, and 8 CCE aggregation levels.

In step S150, modulation symbols are mapped to physical resource elements (CCE to RE mapping).

12 is a flowchart illustrating PDCCH processing.

Referring to FIG. 12, in step S210, the UE demaps a physical resource element to CCE. In step S220, the UE demodulates the CCE aggregation level that the payload corresponding to the reference DCI format may have according to its transmission mode because it does not know which CCE aggregation level it should receive the PDCCH. In step S230, the UE performs rate dematching of the demodulated data according to the payload and the CCE aggregation level. In step S240, channel decoding is performed on the coded data according to the code rate, and the CRC is checked to detect whether an error occurs. If no error occurs, the UE detects its own PDCCH. If an error occurs, the UE continuously performs blind decoding on another CCE aggregation level or another DCI format. In step S250, the UE, which has detected its own PDCCH, removes the CRC from the decoded data to obtain control information necessary for the UE.

A plurality of PDCCHs may be transmitted in one subframe. The terminal monitors the PDCCHs. Here, monitoring means that the terminal attempts to decode each of the PDCCHs according to the monitored DCI format. In the control region allocated in the subframe, the base station does not provide information on where the PDCCH corresponding to the UE is. The UE finds its own PDCCH by monitoring a set of PDCCH candidates in a subframe. This is called blind decoding. For example, if the CRC error is not detected by demasking its C-RNTI in the corresponding PDCCH, the UE detects it as its PDCCH.

In the active mode, the UE monitors the PDCCH of every subframe in order to receive data transmitted to the UE. In the DRX mode, the UE wakes up in the monitoring interval of every DRX cycle and monitors the PDCCH in a subframe corresponding to the monitoring interval. A subframe in which PDCCH monitoring is performed is called a non-DRX subframe.

As such, the terminal must perform blind decoding on all CCEs present in the control region of the non-DRX subframe in order to receive the PDCCH transmitted thereto. Since the UE does not know which PDCCH format is transmitted, it is necessary to decode all PDCCHs at the CCE aggregation level possible until blind decoding of the PDCCH is successful in every non-DRX subframe. Since the UE does not know how many CCEs the PDCCH uses for itself, the UE should attempt detection at all possible CCE aggregation levels until the blind decoding of the PDCCH succeeds.

13 is an exemplary view illustrating control channel monitoring.

Referring to FIG. 13, the total number of CCEs in a corresponding subframe is N _CCEs . CCEs are indexed from 0 to 'N _CCE -1'. CCE group level (L) is {1, 2, 4, 8}, and there are four types. If the CCE aggregation level is 1, the UE may perform blind decoding on all CCE indexes. Even when the CCE aggregation level is 2, 4, or 8, the UE may perform blind decoding on all CCE indexes. That is, the UE may perform blind decoding at every CCE index for each CCE aggregation level.

In addition, the UE attempts blind decoding for all four C-RNTI, P-RNTI, SI-RNTI, and RA-RNTI.

As such, if the UE attempts blind decoding on all possible CRN aggregation levels for all possible RNTIs, the number of detection attempts is excessively large, which increases the complexity of PDCCH monitoring and thus, the battery consumption of the UE. In addition, blind decoding may increase according to the PDCCH payload type according to the DCI format. This is because the UE does not exactly know the type of PDCCH payload that it should receive, and thus needs to perform rate de-matching for different payload types. Therefore, there is a need for an efficient control channel monitoring method for reducing battery consumption of a terminal by reducing the number of detection attempts due to blind decoding.

In order to reduce the number of detection attempts due to blind decoding, the base station may allocate the PDCCH carrying control information randomly to a specific set of PDCCH candidates on the CCE set, instead of randomly assigning the PDCCH. In this case, the UE needs to monitor only a specific set of PDCCH candidates to find a PDCCH. Therefore, the number of detection attempts due to blind decoding can be reduced. Hereinafter, a specific set of PDCCH candidates is defined as a monitoring set.

14 shows an example of a monitoring set when the number of CCEs is four.

Referring to FIG. 14, when the CCE aggregation level is 1, there are four candidate PDCCH candidates, the first candidate (Candidate 1) to the fourth candidate (Candidate 4). If the CCE population level is 2, there are two candidates, Candidate 5 and Candidate 6, and two PDCCH candidates. If the CCE aggregation level is 4, there is a Candidate 7 and one PDCCH candidate. As such, when the number of CCEs is four, there are a total of seven PDCCH candidates. In this case, the monitoring set may be configured as {first candidate, third candidate, fifth candidate, and seventh candidate}. The terminal does not perform blind decoding 7 times and performs blind decoding only on elements of the monitoring set. Therefore, the number of blind decoding attempts can be reduced.

However, the number of OFDM symbols included in the control region in the subframe varies for each subframe. As a result, the number of CCEs is changed for each subframe.

15 shows an example of a monitoring set when the number of CCEs is eight.

Referring to FIG. 15, when the CCE aggregation level is 1, there are eight candidate PDCCH candidates, the first candidate (Candidate 1) to the eighth candidate (Candidate 8). When the CCE population level is 2, there are four candidate PDCCH candidates, Candidate 9 to Candidate 12. If the CCE population level is 4, there are two candidate PDCCHs, Candidate 13 and Candidate 14. If the CCE aggregation level is 8, there is a Candidate 15 and one PDCCH candidate. As described above, when the number of CCEs is 8, there are 15 PDCCH candidates. Here, the monitoring set is composed of {first candidate, third candidate, fifth candidate, and seventh candidate} as in the case where the number of CCEs is four. However, the elements of the monitoring set are selected only when the CCE aggregation level is one. Since the UE performs blind decoding only on elements of the monitoring set, a problem arises that the blind decoding is fundamentally prevented for the CCE aggregation level other than the CCE aggregation level.

As such, if the monitoring set is not determined in consideration of the variable number of CCEs in every subframe, the monitoring set for each CCE aggregation level may be appropriately selected within any one subframe (see FIG. 14). In another subframe, a monitoring set for each CCE aggregation level may be inappropriately selected (see FIG. 15). If the monitoring set is inappropriately selected, the UE is likely to be unable to decode its PDCCH. This causes decoding latency and reduces cell throughput.

Therefore, the monitoring set should be determined in consideration of the number of CCEs that vary in every subframe. The number of elements of the monitoring set, that is, the number of PDCCH candidates belonging to the monitoring set may vary according to the total number of CCEs in the subframe. However, when the monitoring set is previously set between the base station and the terminal or when the base station instructs the terminal through RRC signaling or system information, the monitoring set suitable for the situation of every subframe cannot be informed.

Therefore, the monitoring set should be determined to satisfy the following.

(1) The monitoring set should be determined based on the total number of CCEs that vary in every subframe.

(2) The monitoring set shall be determined to enable blind decoding at every possible CCE aggregation level.

A hashing function can be implemented to determine the monitoring set. The hashing function outputs a set of monitoring.

16 shows an example of a hashing function.

Referring to FIG. 16, the hashing function outputs a monitoring set for each CCE aggregation level. The monitoring set can be output directly according to the behavior of the correct hashing function. For example, the monitoring set output by the hashing function may be configured as an index of the PDCCH candidate as shown in FIG. 14 or FIG. 15. In addition, the monitoring set may be an index of the starting point CCE at which the UE starts monitoring on the logical CCE column. Alternatively, the monitoring set may be a specific range on the CCE column. For example, the specific range may be defined as the index of the CCE that is the starting point on the CCE column and the number of blind decoding attempts from the starting point. Since the hashing function operates for each CCE aggregation level, the UE performs blind decoding on a CCE having a length corresponding to the corresponding CCE aggregation level for the monitoring set for each CCE aggregation level.

The input of the hashing function may use one or more of information through higher layer signaling. For example, input of a hashing function may include a terminal identifier (ID), an MCS level, a control channel format indicator (CCFI), a subframe number, a number of transmit antennas, and a system. It may be a bandwidth (system bandwidth), the number of blind decoding attempts.

(1) terminal ID

The terminal ID is a unique identifier of a specific terminal. For example, C-RNTI can be used. By using the terminal ID as an input of the hashing function, the hashing function can output a UE-specific monitoring set for each terminal. In addition, the terminal ID may be a terminal group ID which is an identifier of a terminal group of a plurality of terminals. By using the terminal group ID as an input of the hashing function, the hashing function may output the same monitoring set for a plurality of terminals belonging to the same group. Alternatively, by using the equation 'terminal group ID mod N' as the terminal ID, the hashing function may output a different monitoring set to each of N terminals (N is a natural number) in the terminal group.

(2) MCS level

The MCS level can be expressed in a variety of ways, including the CCE population level, code rate, modulation sequence, code rate, and combination of modulation sequences. When the MCS level is used for link adaptation for the PDCCH, signaling for informing this may be input to a hashing function. When the MCS level is defined for the PDCCH, the presence or absence of the MCS level in the corresponding subframe may be informed by using on / off of the MCS level. If the MCS level is not defined for the PDCCH, it may inform the MCS level used by the corresponding hashing function. There are a variety of ways to enter MCS levels into a hashing function. When the number of MCS levels is small, the MCS level may be directly input or an index of the MCS level may be input. When the combination of MCS levels is complicated or the number of MCS levels is large, the combination of MCS levels may be tabbed in order to input an index of a table.

(3) Control Channel Format Indicator (CCFI)

The control channel format indicator is information on the number of OFDM symbols used for transmission of PDCCHs in a subframe. The UE can know the control channel format indicator through the PCFICH. For example, in an LTE system, three or fewer OFDM symbols may be used for transmission of PDCCHs according to a control channel format indicator. By using the control channel format indicator as an input of the hashing function, the hashing function may output a monitoring set by reflecting the variable CCE number in every subframe.

(4) subframe number

The subframe number is information indicating which subframe is a corresponding subframe in the radio frame. For example, the radio frame has a length of 10 ms and the subframe has a length of 1 ms. However, this is merely an example, and the length of the radio frame or the length of the subframe may be set differently for each system. By using the subframe number as the input of the hashing function, the hashing function can output a monitoring set distributed randomly for each subframe.

(5) transmit antennas

The number of CCEs in a subframe may vary depending on the number of transmit antennas. This is because the amount of resources occupied by the downlink reference signal (RS) in a subframe varies according to the configuration of the number of transmit antennas. When the number of transmit antennas is set to 1 or 2, the resources occupied by the reference signals for the first transmit antenna and the second transmit antenna are excluded from the OFDM symbol in which the control channel is transmitted, and then the number of CCEs valid for the control channel transmission is extracted. do. When the number of transmit antennas is 4, the resources occupied by the reference signals for the first transmit antenna, the second transmit antenna, the third transmit antenna, and the fourth transmit antenna are excluded from the OFDM symbol in which the control channel is transmitted, and then the control channel. Extract the number of CCEs available for transmission. In addition, when the number of transmit antennas is 1, resource mapping of PHICH and PHICH group is changed. As such, the number of CCEs in a subframe may vary according to the setting of the number of transmit antennas.

Accordingly, by using the number of transmit antennas as an input of the hashing function, the hashing function may output the monitoring set by reflecting the number of CCEs that vary in every subframe.

(6) system bandwidth

Depending on the system bandwidth, the length of the resource allocation field may vary in control information such as downlink scheduling information or uplink scheduling grant. Due to the field varying according to the system bandwidth, the CCE size may vary for each system bandwidth or a specific system bandwidth, or the rate matching for the specific CCE size may vary. For example, in an LTE system, the CCE size at 5 MHz (Megahertz) may be 36 resource elements, and the CCE size at 10 MHz or 20 MHz may be 48 resource elements. As such, due to the CCE size varying according to the system bandwidth, the number of CCEs in the subframe may vary according to the system bandwidth. Therefore, by using the system bandwidth as an input of the hashing function, the hashing function can output the monitoring set by reflecting the number of CCEs varying according to the system bandwidth.

(7) Number of blind decoding attempts

The number of blind decoding attempts means the number of candidate PDCCHs that can be monitored for each CCE aggregation level or the number of scheduled PDCCHs for each CCE aggregation level. Information that can limit the number of blind decoding attempts can also be used as input to a hashing function. For example, the number of blind decoding attempts may be directly input to the hashing function to limit the number of blind decoding attempts that the terminal can perform in the monitoring set.

(8) other

In addition, an argument that can change the number of CCEs in every subframe can be used as an input of a hashing function. For example, information on the length of a cyclic prefix (CP) of an OFDM symbol, information on the amount of PHICH transmitted through a control channel, and the like may be used as an input of a hashing function. This is because the number of OFDM symbols in a subframe changes according to the CP length in the OFDM system and affects the number of resource elements of a control channel. Therefore, information about whether the CP length is normal or extended may be used as an input of a hashing function. The amount of PHICH may also vary the number of CCEs in every subframe. Accordingly, the amount of PHICH may be used as semi-static higher layer signaling or as input of a hashing function every subframe.

One or more of the above factors can be used as input to a hashing function. You can also use other arguments as input to the hashing function.

The base station and the terminal use these factors as inputs to the hashing function, thereby determining the monitoring set that the terminal should monitor in the subframe.

The hashing function may be applied like a search space or a specific frequency region. When signaling to allow the UE to perform blind decoding only for a specific frequency domain is transmitted, a monitoring set may be determined using a hashing function within a specific frequency domain.

The search space is a space for searching for the PDCCH configured by the CCE aggregation level or any method on the logical CCE column. A search space is a set of contiguous CCEs starting at a specific starting location within a CCE set according to the CCE aggregation level. Search spaces are defined for each CCE aggregation level.

The specific starting point within the set of CCEs that the search space begins can be found using a hashing function. For example, the starting point of the search space may be output using a hashing function, and the search space may be defined using the number of candidates of the PDCCH.

The search space may be divided into a common search space and a UE-specific search space. The common search space is a search space monitored by all terminals in a cell, and the terminal specific search space is a search space monitored by a specific terminal. The terminal monitors both the common search space and the terminal specific search space. The common search space and the terminal specific search space may overlap.

The following table is an example of the DCI format that the UE should monitor in the search space and the search space. The size of the CCE aggregation level (L), the number of candidates (M ^(L) ) of the PDCCH shown in the following table is for illustrative purposes, and not limitation.

Search space Number of PDCCH candidates M ^(L) DCI formats Type Aggregation Level L [CCEs] Size of Search Space [in CCEs] UE-specific One 6 6 0, 1, 1A, 1B, 2, 2A 2 12 6 4 8 2 8 16 2 Commmon 4 16 4 0, 1A, 1C, 3 / 3A 8 16 2

The UE-specific search space supports the CCE aggregation level L∈ {1,2,4,8}, and the common search space supports the CCE aggregation level L∈ {4,8}. The size of the search space is determined according to the size of the CCE aggregation level and the number of PDCCH candidates. That is, the size of the search space is an integer multiple of the size of the CCE aggregation level or the number of PDCCH candidates.

When the total number of CCEs in the kth subframe is N _{CCE , k} , CCE group level L? In {1,2,4,8}, the search space S ^(L) _k can be expressed as the following equation.

Where Z ^(L) _k is the starting point of the search space, i = 0, 1,... , M ^(L) · L-1, M ^(L) is the number of PDCCH candidates in a given search space. The starting point is the point where the first PDCCH candidate is located in the search space. The UE decodes the PDCCH candidates in units of CCE aggregation level starting from the starting point in the search space and determines whether the UE is a required PDCCH. Modulo operation means recursive search on a set of CCEs.

The starting point of the UE-specific search space may be different for each subframe, for each CCE aggregation level, or for each UE. The following equation is an example of a hashing function for obtaining a starting point Z ^(L) _k of a terminal-specific search space.

는 내림(floor) 함수로 a보다 작거나 같으면서 가장 큰 정수이다.Where Y ₋₁ = n _RNTI ≠ 0, A = 39827 and D = 65537,

Is the floor function, which is the largest integer less than or equal to a.

In the common search space, the starting point of the common search space is the same for all terminals in the cell. For example, Z _k ^(L) = 0 may be fixed for two CCE aggregation levels where L = 4 and L = 8 in the kth subframe.

17 is an exemplary view illustrating control channel monitoring according to a common search space. 18 is an exemplary view illustrating control channel monitoring according to a terminal specific search space.

17 and 18, the size of the CCE set, that is, the total number of CCEs constituting the control region in the k-th subframe, is N _{CCE , k} . CCEs are indexed from 0 to 'N _{CCE , k} -1'. The total number of CCEs is influenced by the number of OFDM symbols used for transmission of PDCCHs in a subframe or the number of antennas used in the corresponding subframe. The UE can know the number of the OFDM symbols through the PCFICH.

Here, the starting point of the common search space on a logical set of CCEs where the total number of _CCEs is N _{CCE , k} is the first of the CCEs, Z _k ^(L). Let it be 0. Assume that the starting point of the UE-specific search space output through the hashing function is Z _k ^(L) = 18 for all of the CCE aggregation levels 1, 2, 4, and 8. It can be seen that the UE-specific search space is different for each CCE aggregation level.

The terminal monitors one common search space at each of the CCE aggregation levels 4 and 8, and monitors one terminal specific search space at each of the CCE aggregation levels 1, 2, 4 and 8. In the common search space where the CCE aggregation level L = 4, the UE attempts blind decoding on four PDCCH candidates. In the common search space where the CCE aggregation level L = 8, the UE attempts blind decoding on two PDCCH candidates. In the UE specific search space S _k ⁽¹⁾ _{where the} CCE aggregation level L = 1, the UE attempts blind decoding on 6 PDCCH candidates. In the UE specific search space S _k ⁽²⁾ _{where the} CCE aggregation level L = 2, the UE attempts blind decoding on 6 PDCCH candidates. In the UE-specific search space S _k ⁽⁴⁾ _where CCE aggregation level L = 4, the UE attempts blind decoding on two PDCCH candidates. In the UE-specific search space S _k ⁽⁸⁾ _where CCE aggregation level L = 8, the UE attempts blind decoding on two PDCCH candidates.

By determining the monitoring set using the hashing function as described above, control channel monitoring can be efficiently performed by reducing the number of detection attempts due to the blind decoding.

However, in addition to obtaining a monitoring set for each CCE group level using a hashing function, another method for reducing the number of detection attempts due to blind decoding may be considered. First, there is a way to select the CCE group level. Second, there is a method of selecting a PDCCH payload length. These methods can be used independently or within a monitoring set determined using a hashing function.

(1) CCE group level selection

Select a CCE group level to monitor the selected CCE group level. By performing blind decoding only on the selected CCE aggregation level, it is possible to reduce the number of detection attempts due to the blind decoding.

The CCE aggregation level may be selected first considering the previous subframe or secondly, considering the transmission mode.

First, the CCE aggregation level is selected in consideration of the previous subframe. When the UE succeeds in detecting a PDCCH of a specific CCE aggregation level in a previous subframe, the UE preferentially selects the specific CCE aggregation level in a subsequent subframe and performs blind decoding. If the UE does not detect the PDCCH at a specific CCE aggregation level, blind decoding is performed by selecting a CCE aggregation level close to the specific CCE aggregation level. The specific selection order of the CCE aggregation level may be any arbitrary order considering the order application method.

Second, the CCE aggregation level is selected in consideration of the transmission mode. The terminal semi-statically sets the transmission mode through higher layer signaling. The transmission mode is determined according to channel conditions considering intra-path path attenuation or shadowing. The transmission mode using the multi-antenna may be set when the channel environment between the base station and the terminal is good. Therefore, in the transmission mode using the multi-antenna, it is assumed that the channel environment is good, and the UE may attempt blind decoding only for the CCE aggregation levels 1 and 2 having a low CCE aggregation level.

The method of selecting the CCE aggregation level according to the transmission mode may be preset between the base station and the terminal. Through this, even when the UE does not detect the PDCCH on the subframe during the preset period, the CCE aggregation level may be selected according to the transmission mode.

To select the CCE aggregation level, a hashing function may be used. For example, the hashing function may output only the monitoring set for the CCE aggregation level to be monitored first, instead of outputting the monitoring set for every CCE aggregation level. Alternatively, the hashing function may output the starting point of the UE-specific search space and the CCE aggregation level to be preferentially monitored.

(2) PDCCH payload selection

By selecting the PDCCH payload and performing blind decoding only on the selected PDCCH payload, the number of detection attempts due to the blind decoding can be reduced. This is because the control information carried on the PDCCH payload or the length of the PDCCH payload varies depending on the format of the PDCCH payload.

The control information on the PDCCH includes downlink scheduling assignment (DL scheduling assignment), uplink grant (UL grant), simple downlink scheduling assignment, and control channel (PCI) for PCH, which are control channels for downlink data transmission. Channel), control information for indicating a random access response (RACH response), and control information for a dedicated broadcast channel (DBCH). The length of the PDCCH payload according to the type of control information is from the long order downlink scheduling allocation, uplink grant, PICH. Simple downlink scheduling allocation has the same length as the uplink grant and the PDCCH payload, and control information for indicating a random access response and control information for the DBCH have the same PICH and PDCCH payload length. However, this does not consider multi-antenna transmission. In consideration of the multi-antenna transmission, the length of the PDCCH payload may be further varied to support the multi-antenna transmission.

The PDCCH payload may be first selected in consideration of a transmission mode or secondly, in consideration of a terminal state.

First, the PDCCH payload is selected in consideration of the transmission mode.

The UE first performs blind decoding on a PDCCH payload corresponding to a transmission mode known to the UE. For example, in the case of multi-antenna transmission, the UE does not perform blind decoding on the PDCCH payload corresponding to the single antenna transmission. In the case of multi-antenna transmission, blind decoding is performed on the PDCCH payload of the transmission mode, and when the PDCCH is not detected, the blind decoding is performed on the PDCCH payload of another transmission mode of the multi-antenna transmission.

If the transmission mode used by the terminal is SU-MIMO, the number of codewords used is determined from 1 or 2. This is information that can vary dynamically in every subframe. Therefore, when the transmission mode is SU-MIMO, blind decoding is performed on one or two codewords.

Second, the PDCCH payload is selected in consideration of the terminal state.

The UE selects a PDCCH payload type according to whether the UE state is an active state or an idle state, and performs blind decoding on the selected PDCCH payload.

For example, when the terminal is in the idle mode, only the PICH is decoded. In this case, the UE may detect whether the CRC error by demasking only the P-RNTI in the CRC. In addition, when the terminal is connected to the network via the random access channel before synchronization, only control information for indicating a random access response is decoded. In this case, the UE may detect whether the CRC error by demasking only the RA-RNTI in the CRC. In addition, when the terminal is in the active mode, blind decoding is performed only for downlink scheduling allocation, concise downlink scheduling allocation, and uplink grant.

Various methods for reducing the number of blind decoding attempts described so far may be used independently, or any combination of methods may be used for various purposes. Through such a method, the UE can efficiently monitor the PDCCH. Also, the base station can efficiently multiplex and transmit a plurality of PDCCHs carrying control information for a plurality of terminals. Through this, the number of detection attempts due to blind decoding for monitoring the PDCCH can be reduced. It reduces the overhead due to blind decoding and reduces the time it takes for the UE to find the PDCCH that it needs. The battery consumption of the terminal can be reduced, and the performance of the entire system can be expected.

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

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

1 is a block diagram illustrating a wireless communication system.

2 is a block diagram illustrating functional division between an E-UTRAN and an EPC.

3 is a block diagram illustrating elements of a terminal.

4 is a block diagram illustrating a radio protocol structure for a user plane.

5 is a block diagram illustrating a radio protocol structure for a control plane.

6 shows a mapping between a downlink logical channel and a downlink transport channel.

7 shows mapping between a downlink transport channel and a downlink physical channel.

8 shows the structure of a radio frame.

9 is an exemplary diagram illustrating a resource grid for one downlink slot.

10 shows the structure of a subframe.

11 is a flowchart showing the configuration of a PDCCH.

12 is a flowchart illustrating PDCCH processing.

13 is an exemplary view illustrating control channel monitoring.

14 shows an example of a monitoring set when the number of CCEs is four.

15 shows an example of a monitoring set when the number of CCEs is eight.

16 shows an example of a hashing function.

17 is an exemplary view illustrating control channel monitoring according to a common search space.

18 is an exemplary view illustrating control channel monitoring according to a terminal specific search space.

Claims (9)

In the PDCCH (Pysical Downlink Control Channel) search method in a wireless communication system, Setting a transmission mode used for receiving downlink data through a physical downlink shared channel (PDSCH) associated with downlink control information (DCI) signaled by a PDCCH; And The format of the DCI is dependent on the transmission mode, Retrieving the PDCCH in the search space by monitoring at least one PDCCH candidate in the search space, The PDCCH is transmitted through a group of one or several CCEs (Control Channel Element), the DCI is mapped to at least one CCE, the group level is a group of CCEs for one DCI, The search space composed of at least one PDCCH for monitoring is defined as a contiguous set of CCEs in a control region of a subframe, the control region is composed of N _CCE CCEs, and the search space is from a starting point in the control region. Let's start Wherein the starting point is a function of the aggregation level, N _CCE, and user equipment identity (UE ID). The method of claim 1, The function is

Wherein Z is the starting point, L is the aggregation level, and B is a parameter related to the UE ID. The method of claim 1, The search space is a PDCCH search method characterized in that the terminal specific search space monitored by at least one terminal in the cell. The method of claim 1, The transmission mode is set according to the number of transmit antennas PDCCH search method. The method of claim 1, The transmission mode is a PDCCH retrieval method, characterized in that configured via RRC (Radio Resource Control) signaling. The method of claim 1, The transmission mode is any one of a single antenna mode, transmit diversity, open loop spatial multiplexing, closed loop spatial multiplexing, multi-user-multiple input multiple output (MU-MIMO), and closed loop precoding. Way. The method of claim 1, The DCI is mapped to at least one CCE Adding a cyclic redundancy check (CRC) to the DCI; Generating encoded bits by performing channel encoding on the DCI to which the CRC is added; Generating rate matched bits by performing rate matching on the encoded bits; And And mapping the rate matched bits to at least one CCE. 8. The method of claim 7, wherein the CRC is scrambled with the UE ID. In the DCI transmission method in a wireless communication system, Setting a transmission mode used for receiving downlink data on a PDSCH associated with the DCI signaled by the PDCCH; And The format of the DCI is dependent on the transmission mode, Transmitting the DCI through the PDCCH; The PDCCH is transmitted through a group of one or several CCEs, the DCI is mapped to at least one CCE, the group level is a group of CCEs for one DCI.

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