WO2017026798A1 - 비면허 대역에서 제어 채널 전송 방법, 장치 및 시스템 - Google Patents
비면허 대역에서 제어 채널 전송 방법, 장치 및 시스템 Download PDFInfo
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- WO2017026798A1 WO2017026798A1 PCT/KR2016/008800 KR2016008800W WO2017026798A1 WO 2017026798 A1 WO2017026798 A1 WO 2017026798A1 KR 2016008800 W KR2016008800 W KR 2016008800W WO 2017026798 A1 WO2017026798 A1 WO 2017026798A1
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- base station
- subframe
- control channel
- terminal
- transmission
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- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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Definitions
- the present invention relates to a wireless communication system.
- the present invention relates to a method, apparatus and system for transmitting a control channel in an unlicensed band.
- an unlicensed frequency spectrum or an LTE-Unlicensed frequency band eg, 2.4 GHz band, 5 GHz band, etc.
- an LTE-Unlicensed frequency band eg, 2.4 GHz band, 5 GHz band, etc.
- the unlicensed band unlike a licensed band in which a telecommunications carrier secures an exclusive frequency license through an auction process, in the unlicensed band, a plurality of communication facilities may be used simultaneously without restriction if only a certain level of adjacent band protection regulations are observed. As a result, when the unlicensed band is used for cellular communication service, it is difficult to guarantee the communication quality of the level provided in the licensed band, and an interference problem with a wireless communication device (for example, a WLAN device) that uses the unlicensed band may occur. Can be.
- a specific frequency band eg, an unlicensed band
- a base station of a wireless communication system includes a communication module; And a processor, wherein, when the processor transmits a radio frame divided into a plurality of subframes through the communication module and transmits a partial subframe having a duration shorter than the duration of the subframe, an OFDM including a reference signal (Orthogonal Frequency Divisional Multiplexing) At the time of transmitting a symbol, transmission of a control channel for scheduling data transmitted through the partial subframe is started.
- OFDM Orthogonal Frequency Divisional Multiplexing
- the processor may start transmission of the partial subframe at a time point not at the boundary of the subframe.
- the control channel may only schedule data transmitted later than the control channel.
- the processor may transmit the reference signal at a predetermined time point.
- the processor may start transmitting the control channel from a time point when half of the duration of the subframe elapses from the boundary of the subframe.
- the reference signal may be a signal for estimating a channel state of a cell in which the partial subframe is transmitted.
- the processor may transmit a signal for occupying a radio resource before starting transmission of the control channel.
- the signal for occupying the radio resource may indicate that transmission of the base station is started.
- a terminal of a wireless communication system includes a communication module; And a processor, wherein the processor includes a reference signal when receiving a radio frame divided into the plurality of subframes through the communication module and receiving a partial subframe having a duration shorter than a duration of the subframe.
- the processor includes a reference signal when receiving a radio frame divided into the plurality of subframes through the communication module and receiving a partial subframe having a duration shorter than a duration of the subframe.
- OFDM Orthogonal Frequency Divisional Multiplexing
- the processor may start receiving the partial subframe at a time point not at the boundary of the subframe.
- the control channel may only schedule data transmitted later than the control channel.
- the processor may receive the reference signal at a predetermined time point.
- the control channel may be received from a time point when half of the duration of the subframe elapses from the boundary of the subframe.
- the reference signal may be a signal for estimating a channel state of a cell in which the partial subframe is transmitted.
- the processor may ignore a signal received before the control channel.
- the control channel may schedule data transmitted in a cell other than the cell in which the control channel is transmitted.
- a method of operating a terminal of a wireless communication system includes the step of receiving a radio frame divided into a plurality of subframes, the step of receiving the radio frame has a duration shorter than the duration of the subframe Monitoring a reception of a control channel for scheduling data transmitted over the partial subframe at the time of receiving an Orthogonal Frequency Divisional Multiplexing (OFDM) symbol including a reference signal when receiving the partial subframe having the same; .
- OFDM Orthogonal Frequency Divisional Multiplexing
- Monitoring the reception of the control channel may include starting the reception of the partial subframe at a time point not at the boundary of the subframe.
- the control channel may only schedule data transmitted later than the control channel.
- Monitoring the reception of the control channel may include receiving the reference signal at a predetermined time point.
- the wireless communication system in particular the cellular wireless communication system, according to an embodiment of the present invention provides a method for efficiently transmitting a signal and an apparatus therefor.
- a wireless communication system according to an exemplary embodiment of the present invention provides a method and apparatus for efficiently transmitting a signal in a specific frequency band (eg, an unlicensed band).
- the wireless communication system according to an embodiment of the present invention provides a method and apparatus for transmitting a control channel efficiently in a specific frequency band (eg, unlicensed band).
- FIG. 1 is a diagram illustrating a physical channel used in a 3rd generation partnership project (3GPP) system and a general signal transmission method using the same.
- 3GPP 3rd generation partnership project
- FIG. 2 illustrates an example of a radio frame structure used in a wireless communication system.
- FIG. 3 illustrates an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system.
- FIG. 4 illustrates a structure of a downlink subframe.
- 5 illustrates a structure of an uplink subframe.
- 6 is a diagram for describing single carrier communication and multicarrier communication.
- FIG. 7 shows an example in which a cross carrier scheduling technique is applied.
- DRS discovery reference signal
- 9 to 11 illustrate the structure of a reference signal used as a DRS.
- LAA 12 illustrates a Licensed Assisted Access (LAA) service environment.
- FIG. 13 illustrates a deployment scenario of a terminal and a base station in a LAA service environment.
- FIG. 14 illustrates a conventional communication scheme operating in an unlicensed band.
- LBT List-Before-Talk
- FIG 17 illustrates a resource that a base station can use after an LBT procedure in an unlicensed band according to an embodiment of the present invention.
- FIG. 18 illustrates a method of transmitting a control channel for scheduling a partial subframe after an LBT procedure in an unlicensed band by a base station according to an embodiment of the present invention.
- 19 shows a method for a base station to transmit a control channel for scheduling an integrated subframe after an LBT procedure in an unlicensed band according to an embodiment of the present invention.
- 20 shows another method of transmitting a control channel for scheduling an integrated subframe after an LBT procedure in an unlicensed band by a base station according to an embodiment of the present invention.
- 21 shows a method of transmitting a control channel for scheduling a subframe having a boundary different from that of a PCell after the LBT procedure in the unlicensed band according to an embodiment of the present invention.
- FIG. 22 is a view illustrating another method of transmitting a control channel for scheduling an integrated subframe after an LBT procedure in an unlicensed band by a base station according to an embodiment of the present invention.
- FIG. 23 illustrates operations of a base station and a terminal according to an embodiment of the present invention.
- FIG. 24 shows a configuration of a terminal and a base station according to an embodiment of the present invention.
- CDMA code division multiple access
- FDMA frequency division multiple access
- TDMA time division multiple access
- OFDMA orthogonal frequency division multiple access
- SC-FDMA single carrier frequency division multiple access
- 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).
- GSM Global System for Mobile communications
- GPRS General Packet Radio Service
- EDGE Enhanced Data Rates for GSM Evolution
- 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).
- 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 E-UTRA and LTE-A (Advanced) is an evolved version of 3GPP LTE.
- 3GPP LTE / LTE-A the technical spirit of the present invention is not limited thereto.
- the terminal receives information through downlink (DL) from the base station, and the terminal transmits information through uplink (UL) to the base station.
- the information transmitted and received between the base station and the terminal includes data and various control channels, and various physical channels exist according to the type / use of the information transmitted and received.
- the terminal When the terminal is powered on or enters a new cell, the terminal performs an initial cell search operation such as synchronization with the base station (S101). To this end, the UE receives a Primary Synchronization Channel (P-SCH) and a Secondary Synchronization Channel (S-SCH) from the base station, synchronizes with the base station, and obtains information such as a cell ID. have. Thereafter, the terminal may receive a physical broadcast channel from the base station to obtain broadcast information in a cell. The UE may check a downlink channel state by receiving a downlink reference signal (DL RS) in an initial cell search step.
- P-SCH Primary Synchronization Channel
- S-SCH Secondary Synchronization Channel
- the terminal may receive a physical broadcast channel from the base station to obtain broadcast information in a cell.
- the UE may check a downlink channel state by receiving a downlink reference signal (DL RS) in an initial cell search step.
- DL RS downlink reference signal
- the UE Upon completion of initial cell search, the UE obtains more specific system information by receiving a physical downlink shared channel (PDSCH) according to a physical downlink control channel (PDCCH) and information on the PDCCH. It may be (S102).
- PDSCH physical downlink shared channel
- PDCCH physical downlink control channel
- the terminal may perform a random access procedure (RACH) for the base station (S103 ⁇ S106).
- RACH random access procedure
- the UE may transmit a preamble through a physical random access channel (PRACH) (S103) and receive a response message for the preamble through a PDCCH and a corresponding PDSCH (S104).
- PRACH physical random access channel
- S104 receives a response message for the preamble through a PDCCH and a corresponding PDSCH
- the terminal transmits data including its own identifier and the like to the base station by using the uplink grant (S105).
- the terminal waits for reception of the PDCCH as an instruction of the base station to resolve the collision.
- the terminal receives the PDCCH through its identifier (S106)
- the random access process is terminated.
- the UE may perform PDCCH / PDSCH reception (S107) and Physical Uplink Shared Channel (PUSCH) / Physical Uplink Control Channel (PUCCH) transmission (S108) as a general procedure.
- the terminal receives downlink control information (DCI) through a control channel (PDCCH or E-PDCCH).
- DCI downlink control information
- the DCI includes control information such as resource allocation information for the terminal and has a different format according to the purpose of use.
- Control information transmitted from the terminal to the base station is referred to as uplink control information (UCI).
- UCI uplink control information
- UCI includes Acknowledgment / Negative Acknowledgment (ACK / NACK), Channel Quality Indicator (CQI), Precoding Matrix Index (PMI), Rank Indicator (RI), and the like.
- ACK / NACK Acknowledgment / Negative Acknowledgment
- CQI Channel Quality Indicator
- PMI Precoding Matrix Index
- RI Rank Indicator
- UCI may be transmitted on PUSCH and / or PUCCH.
- FIG. 2 shows an example of a radio frame structure used in a wireless communication system.
- FIG. 2 (a) shows a frame structure for frequency division duplex (FDD)
- FIG. 2 (b) shows a frame structure for time division duplex (TDD).
- FDD frequency division duplex
- TDD time division duplex
- the radio frame has a length of 10 ms (307200 Ts) and may be configured of 10 subframes (SF).
- Each subframe has a length of 1 ms and may consist of two slots. Each slot is 0.5ms long. 20 slots in one radio frame may be sequentially numbered from 0 to 19. Each slot is 0.5ms long.
- the time for transmitting one subframe is defined as a transmission time interval (TTI).
- the time resource may be classified by a radio frame number / index, a subframe number / index (# 0 to # 9), and a slot number / index (# 0 to # 19).
- the radio frame may be configured differently according to the duplex mode.
- FDD mode downlink transmission and uplink transmission are divided by frequency, and a radio frame includes only one of a downlink subframe or an uplink subframe for a specific frequency band.
- TDD mode downlink transmission and uplink transmission are classified by time, and a radio frame includes both a downlink subframe and an uplink subframe for a specific frequency band.
- the TDD radio frame further includes a special subframe for downlink and uplink switching.
- the special subframe includes a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS).
- DwPTS downlink pilot time slot
- GP guard period
- UpPTS uplink pilot time slot
- 3 shows a structure of a downlink / uplink slot.
- a slot includes a plurality of Orthogonal Frequency Divisional Multiplexing (OFDM) symbols in the time domain and a plurality of Resource Blocks (RBs) in the frequency domain.
- An OFDM symbol may mean a symbol period.
- the OFDM symbol may be called an OFDMA symbol, a Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol, or the like according to a multiple access scheme.
- the number of OFDM symbols included in one slot may vary depending on the length of a cyclic prefix (CP). For example, in case of a normal CP, one slot includes 7 OFDM symbols, whereas in case of an extended CP, one slot includes 6 OFDM symbols.
- CP cyclic prefix
- RB is defined as N DL / UL symb (e.g. 7) consecutive OFDM symbols in the time domain and N RB sc (e.g. 12) consecutive subcarriers in the frequency domain.
- a resource composed of one OFDM symbol and one subcarrier is called a resource element (RE) or tone.
- One RB is composed of N DL / UL symb * N RB sc resource elements.
- the resource of the slot may be represented by a resource grid composed of N DL / UL RB * N RB sc subcarriers and N DL / UL symb OFDM symbols.
- Each RE in the resource grid is uniquely defined by an index pair (k, 1) per slot.
- k is an index given from 0 to N DL / UL RB * N RB sc ⁇ 1 in the frequency domain
- l is an index given from 0 to N DL / UL symb ⁇ 1 in the time domain.
- N DL RB represents the number of resource blocks (RBs) in the downlink slot
- N UL RB represents the number of RBs in the UL slot.
- N DL RB and N UL RB depend on DL transmission bandwidth and UL transmission bandwidth, respectively.
- N DL symb represents the number of symbols in the downlink slot
- N UL symb represents the number of symbols in the UL slot.
- N RB sc represents the number of subcarriers constituting one RB. There is one resource grid per antenna port.
- FIG. 4 illustrates a structure of a downlink subframe.
- a subframe may consist of 14 OFDM symbols.
- the first 1 to 3 (or 2 to 4) OFDM symbols are used as the control region, and the remaining 13 to 11 (or 12 to 10) OFDM symbols are used as the data region.
- R1 to R4 represent reference signals for antenna ports 0 to 3.
- Control channels allocated to the control region include a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a Physical Downlink Control Channel (PDCCH).
- the data channel allocated to the data region includes PDSCH.
- Enhanced PDCCH (EPDCCH) is set, PDSCH and EPDCCH are multiplexed by frequency division multiplexing (FDM) in the data region.
- FDM frequency division multiplexing
- the PDCCH is a physical downlink control channel and is allocated to the first n OFDM symbols of a subframe. n is indicated by the PCFICH as an integer equal to or greater than 1 (or 2).
- the PDCCH informs each UE or UE group of information related to resource allocation of a paging channel (PCH) and a downlink-shared channel (DL-SCH), uplink scheduling grant, HARQ information, and the like.
- Data of the PCH and DL-SCH ie, a transport block
- the base station and the terminal generally transmit and receive data through the PDSCH except for specific control information or specific service data.
- Data of the PDSCH is transmitted to which UE (one or a plurality of UEs), and information on how the UEs should receive and decode the PDSCH data is included in the PDCCH / EPDCCH and transmitted.
- a PDCCH / EPDCCH is CRC masked with a Radio Network Temporary Identity (RNTI) of "A”, a radio resource (eg, a frequency location) of "B” and a DCI format of "C”, that is, transmission
- RTI Radio Network Temporary Identity
- the UE in the cell monitors the PDCCH / EPDCCH using its own RNTI information, and if there is at least one UE having an “A” RNTI, the terminals receive the PDCCH / EPDCCH and receive the received PDCCH / The PDSCH indicated by "B" and "C" is received through the information of the EPDCCH.
- 5 illustrates a structure of an uplink subframe.
- a subframe may be divided into a control region and a data region in the frequency domain.
- PUCCH is allocated to the control region and carries the UCI.
- PUSCH is allocated to the data area and carries user data.
- PUCCH may be used to transmit the following control information.
- SR Service Request: Information used to request a UL-SCH resource. It is transmitted using OOK (On-Off Keying) method.
- HARQ-ACK A response to a PDCCH and / or a response to a downlink data packet (eg, codeword) on a PDSCH. Codewords are encoded forms of transport blocks.
- HARQ-ACK indicates whether a PDCCH or PDSCH is successfully received.
- HARQ-ACK response includes a positive ACK (simple, ACK), negative ACK (NACK), DTX (Discontinuous Transmission) or NACK / DTX.
- the DTX indicates a case where the UE misses a PDCCH (or semi-persistent scheduling (SPS) PDSCH), and NACK / DTX means NACK or DTX.
- HARQ-ACK is mixed with HARQ-ACK / NACK and ACK / NACK.
- CSI Channel State Information
- MIMO Multiple Input Multiple Output
- Table 1 shows the relationship between the PUCCH format and UCI.
- Carrier aggregation refers to a method in which a plurality of frequency blocks are used as one large logical frequency band in order for a wireless communication system to use a wider frequency band.
- a frequency band used for communication with each terminal is defined in component carrier (CC) units.
- 6 is a diagram for describing single carrier communication and multicarrier communication.
- 6 (a) shows a subframe structure of a single carrier
- FIG. 6 (b) shows a subframe structure of carrier aggregated multiple carriers.
- a base station and a terminal perform data communication through one DL band and one UL band corresponding thereto.
- the DL / UL band is divided into a plurality of orthogonal subcarriers, each frequency band operating on one carrier frequency.
- DL / UL bands operate on different carrier frequencies
- DL / UL bands operate on the same carrier frequency.
- Carrier frequency means the center frequency (center frequency) of the frequency band
- DL / UL communication is carried by putting a base frequency band divided into a plurality of subcarriers on one carrier frequency. It is distinguished from an OFDM system that performs the operation.
- three 20 MHz CCs may be gathered in the UL and the DL to support a 60 MHz bandwidth. CCs may be adjacent or non-adjacent to each other in the frequency domain.
- FIG. 6B illustrates a case in which the bandwidth of the UL CC and the bandwidth of the DL CC are the same and symmetrical, but the bandwidth of each CC may be determined independently.
- asymmetrical carrier aggregation in which the number of UL CCs and the number of DL CCs are different is possible.
- the DL / UL CC (s) are allocated / configured independently for each terminal, and the DL / UL CC (s) assigned / configured for the terminal are referred to as serving UL / DL CC (s) of the terminal. .
- the base station may activate some or all of the serving CCs of the terminal or may deactivate some CCs.
- the base station assigns the CC (s) to the terminal, at least one specific CC among the CC (s) configured for the terminal is not deactivated unless the CC allocation for the terminal is completely reconfigured or the terminal does not handover.
- a specific CC that is always activated is called a primary CC (PCC)
- PCC primary CC
- SCC secondary CC
- PCC and SCC may be classified based on control information. For example, specific control information may be configured to be transmitted and received only through a specific CC. Such a specific CC may be referred to as a PCC, and the remaining CC (s) may be referred to as an SCC (s).
- PUCCH is transmitted only on PCC.
- a cell is defined as a combination of DL resources and UL resources, that is, a combination of DL CCs and UL CCs.
- the cell may be configured with only DL resources or a combination of DL resources and UL resources.
- the linkage between the carrier frequency of the DL resource (or DL CC) and the carrier frequency of the UL resource (or UL CC) may be indicated by system information.
- SIB2 System Information Block Type 2
- the carrier frequency refers to the center frequency of each cell or CC.
- the cell corresponding to the PCC is referred to as a primary cell (PCell), and the cell corresponding to the SCC is referred to as a secondary cell (SCell).
- the carrier corresponding to the PCell in downlink is DL PCC
- the carrier corresponding to the PCell in uplink is UL PCC
- the carrier corresponding to the SCell in downlink is DL SCC
- the carrier corresponding to the SCell in uplink is UL SCC.
- the serving cell (s) may be configured with one PCell and zero or more SCells. In case of the UE that is in the RRC_CONNECTED state but the carrier aggregation is not set or does not support the carrier aggregation, there is only one serving cell configured only with the PCell.
- the control channel transmitted through the first CC may schedule a data channel transmitted through the first CC or the second CC using a carrier indicator field (CIF).
- CIF is included in DCI.
- a scheduling cell is configured, and the DL grant / UL grant transmitted in the PDCCH region of the scheduling cell schedules the PDSCH / PUSCH of the scheduled cell. That is, a search region for the plurality of component carriers exists in the PDCCH region of the scheduling cell.
- PCell is basically a scheduling cell, and a specific SCell may be designated as a scheduling cell by an upper layer.
- DL component carrier # 0 is DL PCC (or PCell)
- DL component carrier # 1 and DL component carrier # 2 are DL SCC (or SCell).
- the DL PCC is set to the PDCCH monitoring CC. If CIF is disabled, each DL CC can only transmit PDCCH scheduling its PDSCH without CIF according to LTE PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling).
- a specific CC (eg, DL PCC) uses a CIF to schedule the PDSCH of DL CC A
- PDCCH scheduling PDSCH of another CC may be transmitted (cross-carrier scheduling).
- PDCCH is not transmitted in another DL CC.
- FIGS. 8 to 11 illustrate a structure of a reference signal used as a DRS.
- the DRS in the licensed band is referred to as Rel-12 DRS.
- the DRS supports small cell on / off, and the SCell that is not activated for any UE may be turned off except for DRS periodic transmission.
- the UE may perform cell identification information acquisition, RRM (Radio Resource Management) measurement, downlink synchronization acquisition.
- RRM Radio Resource Management
- a discovery measurement timing configuration indicates a time window in which a terminal expects to receive a DRS.
- DMTC is fixed at 6ms.
- the DMTC period is a transmission period of the DMTC and may be 40ms, 80ms or 160ms.
- the location of the DMTC is specified by a DMTC transmission period and a DMTC offset (subframe unit), and these information are transmitted to the terminal through higher layer signaling (eg, RRC signaling).
- the DRS transmission occurs at the DRS opportunity in the DMTC.
- the DRS opportunity has a transmission period of 40 ms, 80 ms or 160 ms, and the UE may assume that there is one DRS opportunity for each DMTC period.
- the DRS opportunity consists of 1-5 contiguous subframes in an FDD radio frame and 2-5 contiguous subframes in a TDD radio frame.
- the length of the DRS opportunity is delivered to the terminal through higher layer signaling (eg, RRC signaling).
- the UE may assume the presence of the DRS in a downlink subframe within the DRS opportunity.
- the DRS opportunity may exist anywhere in the DMTC, but the UE expects the transmission interval of the DRSs transmitted from the cell to be fixed (that is, 40 ms, 80 ms or 160 ms). That is, the position of the DRS opportunity in the DMTC is fixed for each cell.
- the DRS consists of:
- Cell-specific Reference Signal (CRS) of antenna port 0 (see FIG. 9): present in all downlink subframes within the DRS opportunity and in the DwPTS of all special subframes.
- the CRS is transmitted in all bands of the subframe.
- PSS Primary Synchronization Signal
- SSS Secondary Synchronization Signal
- Non-zero-power Channel State Information (CSI) -RS (see FIG. 11): present in zero or more subframes within a DRS opportunity.
- the location of the non-zero-power CSI-RS is configured variously according to the number of CSI-RS ports and higher layer configuration information.
- FIG. 8 illustrates a case in which the DRS reception time is set to a separate DMTC for each frequency from the viewpoint of the terminal.
- a DRS opportunity of 2ms length is transmitted every 40ms
- a 3ms length DRS opportunity is transmitted every 80ms
- a DRS opportunity of 4ms length is transmitted every 80ms.
- the UE can know the starting position of the DRS opportunity in the DMTC from the subframe including the SSS.
- the frequencies F1 to F3 may be replaced with corresponding cells, respectively.
- LAA 12 illustrates a Licensed Assisted Access (LAA) service environment.
- a user may use a service environment in which an LTE technology 11 in an existing licensed band and LTE-Unlicensed (LTE-U) or LAA, which is an LTE technology 12 in an unlicensed band that is actively discussed recently, are combined. It may be provided to.
- LTE technology 11 in the licensed band and LTE technology 12 in the unlicensed band may be integrated using techniques such as carrier aggregation, which may contribute to network capacity expansion.
- the LAA may provide an LTE service optimized for various needs or environments.
- the LTE technology in the licensed band is referred to as LTE-Lcensed (LTE-L)
- LTE-U LTE-Unlicensed
- LAA LTE-Unlicensed
- the deployment scenario of the terminal and the base station in an environment in which the existing LTE-L service and the LAA service coexist may be an overlay model or a co-located model.
- the macro base station performs wireless communication with the X terminal and the X 'terminal in the macro region 32 by using a licensed band carrier, and may be connected to a plurality of Radio Remote Heads (RRHs) through X2 interfaces.
- RRHs Radio Remote Heads
- Each RRH may perform wireless communication with an X terminal or an X 'terminal in a predetermined region 31 using an unlicensed band carrier.
- the frequency bands of the macro base station and the RRH are different from each other, so there is no mutual interference.
- fast data exchange is performed between the macro base station and the RRH through the X2 interface. Should be done.
- the pico / femto base station may perform wireless communication with the Y terminal by using a licensed band carrier and an unlicensed band carrier at the same time.
- the pico / femto base station may be limited to downlink transmission using the LTE-L service and the LAA service together.
- the coverage 33 of the LTE-L service and the coverage 34 of the LAA service may be different according to frequency band, transmission power, and the like.
- existing devices eg, wireless LAN (Wi-Fi) equipment
- Wi-Fi wireless LAN
- existing devices may determine the LAA message or data as a kind of energy and perform an interference avoidance operation by an energy detection (or detection) technique. That is, when the energy corresponding to the LAA message or data is less than -62dBm or a specific ED (Energy Detection) threshold, the WLAN devices may ignore the corresponding message or data and communicate.
- the terminal that performs LTE communication in the unlicensed band may be frequently interrupted by the WLAN equipment.
- LBT List-Before-Talk
- CCA clear channel assessment
- a WLAN device eg, AP, STA performs carrier sensing before transmitting data to check whether a channel is busy.
- a wireless signal of a certain intensity or more is detected in a channel to which data is to be transmitted, the corresponding channel is determined to be in use, and the WLAN device delays access to the corresponding channel. This process is called clear channel evaluation, and the signal level that determines whether a signal is detected is called a CCA threshold.
- the channel is determined to be in an idle state if a wireless signal is not detected in the corresponding channel or if a wireless signal having a strength smaller than the CCA threshold is detected, the channel is determined to be in an idle state.
- the UE having data to be transmitted performs a backoff procedure after a defer period (eg, Arbitration InterFrame Space (AIFS), PIFS (PCF IFS, etc.)).
- a defer period eg, Arbitration InterFrame Space (AIFS), PIFS (PCF IFS, etc.
- the dipper period refers to the minimum time that the terminal waits after the channel becomes idle.
- the backoff procedure causes the terminal to wait further for a certain time after the dipper deadline. For example, the terminal waits while decreasing the slot time as long as the random number allocated to the terminal in the contention window (CW) while the channel is idle and exhausts the slot time. The terminal may attempt to access the channel.
- CW contention window
- the terminal can transmit data over the channel. If the data transfer is successful, the CW size CW is reset to the initial value CWmin. On the other hand, if data transfer fails, the CWS doubles. Accordingly, the terminal receives a new random number within a range twice the previous random number range and performs a backoff procedure in the next CW. In the WLAN, only ACK is defined as reception response information for data transmission. Therefore, the CWS is reset to an initial value when an ACK is received for data transmission, and the CWS is doubled when no feedback information is received for the data transmission.
- LTE since most communication in the unlicensed band is operated based on LBT, LTE also considers LBT in LAA for coexistence with existing devices.
- channel access methods on an unlicensed band in LTE may be classified into the following four categories according to whether LBT is present or applied.
- a time interval in which the channel should be sensed idle is determined before the Tx entity transmits on the channel. Random back-off is not performed.
- the Tx entity has a random number N in CW, and the CW size is defined by the minimum / maximum value of N. CW size is fixed. The random number N is used to determine the time interval in which the channel should be sensed idle before the Tx entity transmits on the channel.
- the Tx entity has a random number N in CW, and the CW size is defined by the minimum / maximum value of N.
- the Tx entity can change the CW size when generating a random number N.
- the random number N is used to determine the time interval in which the channel should be sensed idle before the Tx entity transmits on the channel.
- 15 to 16 illustrate a DL transmission process based on category 4 LBT.
- category 4 LBT can be used to ensure fair channel access with Wi-Fi.
- the LBT process includes an Initial CCA (ICCA) and an Extended CCA (ECCA).
- ICCA Initial CCA
- ECCA Extended CCA
- ICCA random back-off is not performed.
- ECCA random back-off is performed using a CW of a variable size.
- ICCA is applied when the channel is idle when signal transmission is required
- ECCA is applied when the channel is in use or immediately before DL transmission when signal transmission is required. That is, it is determined whether the channel is idle through the ICCA, and data transmission is performed after the ICCA period. If the interference signal is recognized and data transmission is not possible, the data transmission time point may be obtained through a defer period + backoff counter after setting the random backoff counter.
- a signal transmission process may be performed as follows.
- S202 The base station confirms that the channel is in an idle state.
- S204 The base station checks whether signal transmission is necessary. If no signal transmission is required, the process returns to S202, and if signal transmission is required, the process proceeds to S206.
- the base station checks whether the channel is idle during the ICCA dipper period B CCA .
- the ICCA dipper period is configurable. As an example embodiment, the ICCA dipper period may consist of a 16 ms interval and n consecutive CCA slots. Here, n is a positive integer, one CCA slot interval may be 9 kHz. The number of CCA slots may be set differently according to the QoS class.
- the ICCA dipper period may be set to an appropriate value in consideration of the dipper periods of the Wi-Fi (eg, DIFS and AIFS). For example, the ICCA dipper period may be 34us. If the channel is idle during the ICCA dipper period, the base station may perform a signal transmission process (S208). If the channel is determined to be in use during the ICCA dipper period, the process proceeds to S212 (ECCA).
- the base station may perform a signal transmission process. If there is no signal transmission proceeds to S202 (ICCA), if there is a signal transmission proceeds to S210. Even if the back-off counter N reaches 0 in S218 and S208 is performed, if there is no signal transmission, the process proceeds to S202 (ICCA), and if there is a signal transmission, the process proceeds to S210.
- S212 The base station generates a random number N in CW.
- N is used as a counter in the back-off process and is generated from [0, q-1].
- the CW is composed of q ECCA slots, and the ECCA slot size may be 9 ms or 10 ms.
- the CW size CWS is defined as q and may vary in S214. Thereafter, the base station proceeds to S216.
- the base station may update the CWS.
- CWS q can be updated to a value between X and Y.
- X and Y values are configurable parameters.
- CWS update / adjustment can be performed every time N generations (dynamic back-off) or semi-statically at regular time intervals (semi-static back-off).
- the CWS can be updated / adjusted based on exponential back-off or binary back-off. That is, the CWS may be updated / adjusted in the form of a power of two or a multiple of two.
- the CWS may be updated / adjusted based on a feedback / report (eg, HARQ ACK / NACK) of the UE, or may be updated / adjusted based on base station sensing.
- a feedback / report eg, HARQ ACK / NACK
- the base station checks whether the channel is idle during the ECCA dipper period (DeCCA).
- the ECCA dipper period can be set.
- the ECCA dipper period may consist of a 16 ms interval and n consecutive CCA slots.
- n is a positive integer
- one CCA slot interval may be 9 kHz.
- the number of CCA slots may be set differently according to the QoS class.
- the ECCA dipper period may be set to an appropriate value in consideration of the dipper periods of the Wi-Fi (eg, DIFS and AIFS). For example, the ECCA dipper period may be 34us. If the channel is idle during the ECCA dipper period, the base station proceeds to S218. If the channel is determined to be in use during the ECCA dipper period, the base station repeats S216.
- S220 The base station senses a channel during one ECCA slot period (T).
- the ECCA slot size is 9 ms or 10 ms and the actual sensing time may be at least 4 ms.
- S222 If it is determined that the channel is empty, the process proceeds to S224. If it is determined that the channel is in use, it returns to S216. That is, one ECCA dipper period is applied again after the channel is empty, and N is not counted down during the ECCA dipper period.
- FIG. 16 is substantially the same / similar to the transmission process of FIG. 15, and there is a difference in implementation manner. Therefore, the details of FIG. 15 may be referred to.
- S302 The base station checks whether signal transmission is necessary. If no signal transmission is required, S302 is repeated, and if signal transmission is required, the flow proceeds to S304.
- S304 The base station checks whether the slot is in an idle state. If the slot is idle, go to S306; if the slot is in use, go to S312 (ECCA). The slot may correspond to the CCA slot in FIG. 15.
- S306 The base station checks whether the channel is idle during the dipper period (D). D may correspond to the ICCA dipper period in FIG. 15. If the channel is idle during the dipper period, the base station may perform a signal transmission process (S308). If the channel is determined to be in use during the dipper period, the flow advances to S304.
- D may correspond to the ICCA dipper period in FIG. 15. If the channel is idle during the dipper period, the base station may perform a signal transmission process (S308). If the channel is determined to be in use during the dipper period, the flow advances to S304.
- the base station may perform a signal transmission process if necessary.
- S310 If there is no signal transmission proceeds to S302 (ICCA), if there is a signal transmission proceeds to S312 (ECCA). Even if the back-off counter N reaches 0 in S318 and S308 is performed, if there is no signal transmission, the process proceeds to S302 (ICCA), and if there is a signal transmission, the process proceeds to S312 (ECCA).
- S312 The base station generates a random number N in CW. N is used as a counter in the back-off process and is generated from [0, q-1].
- the CW size CWS is defined as q and may vary in S314. Thereafter, the base station proceeds to S316.
- the base station may update the CWS.
- CWS q can be updated to a value between X and Y.
- X and Y values are configurable parameters.
- CWS update / adjustment can be performed every time N generations (dynamic back-off) or semi-statically at regular time intervals (semi-static back-off).
- the CWS can be updated / adjusted based on exponential back-off or binary back-off. That is, the CWS may be updated / adjusted in the form of a power of two or a multiple of two.
- the CWS may be updated / adjusted based on a feedback / report (eg, HARQ ACK / NACK) of the UE, or may be updated / adjusted based on base station sensing.
- a feedback / report eg, HARQ ACK / NACK
- S316 The base station checks whether the channel is idle during the dipper period (D). D may correspond to the ECCA dipper period of FIG. 15. D in S306 and S316 may be the same. If the channel is idle during the dipper period, the base station proceeds to S318. If the channel is determined to be in use during the dipper period, the base station repeats S316.
- S320 The base station selects one of operations that decreases N by 1 (ECCA countdown) or does not decrease N (self-deferral). Self-differential operation may be performed depending on the implementation / selection of the base station. In self-differentiation, the base station does not perform sensing for energy detection and does not perform ECCA countdown.
- the base station may select one of an operation that does not perform sensing for energy detection and an energy detection operation. If sensing for energy detection is not performed, the flow proceeds to S324. When performing the energy detection operation, if the energy level is less than the energy detection threshold (that is, idle), the process proceeds to S324. If the energy level exceeds the energy detection threshold (ie busy), the flow returns to S316. That is, one dipper period is applied again after the channel is empty, and N does not count down during the dipper period.
- the base station and the terminal of the wireless communication system can also approach the unlicensed band through competition.
- the efficiency of wireless communication may be reduced. This will be described with reference to FIG. 17.
- FIG 17 illustrates a resource that a base station can use after an LBT procedure in an unlicensed band according to an embodiment of the present invention.
- radio resources may be allocated on a subframe basis.
- the base station and the terminal accesses a radio resource based on the subframe boundary.
- a competition procedure must be performed.
- the base station or the terminal may perform an LBT procedure or a channel sensing procedure to access an unlicensed band.
- the base station or the terminal may transmit a PCell in a frequency band (eg, a licensed band) that does not perform a contention procedure and transmit a SCell in an unlicensed band.
- the base station or the terminal may obtain a transmission opportunity through the LBT procedure in the SCell.
- the start of the transmission opportunity on the SCell obtained by the base station or the terminal may not match the boundary of the subframe as shown in FIG. If the base station or the terminal waits after the contention procedure to access a channel based on the subframe boundary, the base station or the terminal may lose the transmission opportunity obtained through the contention procedure to another wireless communication terminal.
- the base station or the terminal should schedule the transmission time of the data channel and the control channel through a method different from that used in the licensed band.
- the base station or the terminal may access a radio resource regardless of the subframe boundary in the unlicensed band.
- the base station or the terminal may start transmission and reception at any point in the subframe in the unlicensed band.
- the base station or the terminal transmits for a time interval smaller than one subframe, the corresponding time interval is referred to as a partial subframe.
- the base station or the terminal starts transmission from the SCell from the middle of the time interval corresponding to the n th subframe (Subframe n) of the PCell.
- the base station or the terminal may transmit a partial subframe at the end of the transmission.
- the base station or the terminal terminates transmission in the SCell in the middle of a time interval corresponding to the n + 4th subframe (Subframe n + 4) of the PCell.
- the base station or the terminal may transmit a signal for occupying radio resources before starting transmission.
- the signal for occupying the radio resource may be at least one of an initial signal indicating the start of transmission, a reservation signal including no information, a LAA preamble, and a DRS.
- the DRS may be a Rel-12 DRS, or may be a combination or a subset of the PSS, SSS, CRS, and CSI-RS.
- the signal for occupying the radio resource may be for matching the OFDM symbol granularity of the signal transmitted by the base station or the terminal.
- the base station on the specification may indicate at least one of a transmission point (TP), an access point (AP), and a radio remote host (RRH).
- TP transmission point
- AP access point
- RRH radio remote host
- FIG. 18 illustrates a method of transmitting a control channel for scheduling a partial subframe after an LBT procedure in an unlicensed band by a base station according to an embodiment of the present invention.
- FIG. 18 shows that the base station transmits one partial subframe at the start of transmission, transmits three general subframes, and then transmits one partial subframe again.
- the base station may transmit a control channel with each subframe for transmitting data.
- the base station may transmit a PDCCH and an EPDCCH together in each subframe that transmits the PDSCH.
- the control channel may schedule only data transmitted on the same carrier as the carrier on which the control channel is transmitted.
- the base station may transmit a control channel for self-carrier scheduling described above.
- the control channel may also schedule data transmitted on a carrier different from the carrier on which the control channel is transmitted.
- the base station may transmit a control channel for cross-carrier scheduling described above. When the base station transmits the data and the control channel scheduling data in this way, the base station transmits the control channel from the start of the subframe.
- the base station may transmit a partial subframe.
- a base station transmits data through a partial subframe, it is a problem how the base station transmits a control channel for scheduling data transmitted through the partial subframe.
- a base station may transmit a control channel for scheduling data transmitted through a partial subframe through the partial subframe.
- the base station may transmit a control channel for scheduling data transmitted through the partial subframe before data transmission through the partial subframe.
- the control channel may be at least one of PDCCH and EPDCCH.
- the base station may transmit the preamble in the partial subframe and transmit the PDCCH for scheduling the PDSCH, as shown in the embodiment of FIG. 18 (a), and then transmit the PDSCH.
- the base station may transmit the PDSCH after transmitting the PDCCH scheduling the PDSCH in the partial subframe as in the embodiment of FIG.
- the base station may transmit a preamble in a partial subframe and start transmission of the E-PDCCH and PDSCH scheduling the PDSCH as in the embodiment of FIG. 18 (b).
- the base station may simultaneously transmit the E-PDCCH and the PDSCH scheduling the PDSCH in the partial subframe as in the embodiment of FIG. 18 (b).
- the base station may transmit a control channel for scheduling data transmitted through the partial subframe through a subframe following or before the partial subframe.
- the control channel may be at least one of PDCCH and EPDCCH.
- the control channel may include an indicator indicating that data scheduled by the control channel is transmitted through a partial subframe.
- the DCI included in the PDCCH and the EPDCCH may include an indicator indicating that data scheduled by the PDCCH and the EPDCCH are transmitted through a partial subframe. For example, at the start of transmission, the base station transmits the preamble in the partial subframe and transmits the PDSCH as shown in the embodiment of FIG.
- the base station may transmit a PDSCH transmitted in the partial subframe and a PDCCH for scheduling the PDSCH transmitted through the corresponding subframe in the previous subframe of the partial subframe.
- the base station transmits the preamble in the partial subframe and transmits the PDSCH as in the embodiment of FIG. 18 (d), and then transmits the PDSCH and the corresponding subframe in the next subframe of the partial subframe.
- the E-PDCCH for scheduling the PDSCH transmitted through the subframe may be transmitted.
- the base station may transmit the PDSCH transmitted in the partial subframe and the E-PDCCH scheduling the PDSCH transmitted through the corresponding subframe in the previous subframe of the partial subframe as shown in the embodiment of FIG. have.
- the base station may transmit a reservation signal or an initial signal before partial subframe transmission.
- the base station treats the partial subframes as individual subframes.
- the base station may treat one subframe different from the partial subframe as one subframe having a TTI having a value larger than the TTI value of the general subframe.
- a subframe having a TTI having a value larger than the TTI value of a general subframe is referred to as a super subframe.
- a subframe having a general TTI value is referred to as a general subframe to distinguish it from an integrated subframe. A method of transmitting an integrated subframe by the base station will be described with reference to FIG. 19.
- FIG. 19 shows a method for a base station to transmit a control channel for scheduling an integrated subframe after an LBT procedure in an unlicensed band according to an embodiment of the present invention. Specifically, FIG. 19 shows that the base station transmits one unified subframe at the start of transmission, transmits one general subframe, and then transmits one unified subframe again.
- a base station may transmit a control channel for scheduling data transmitted through an integrated subframe through an integrated subframe.
- the base station may transmit a control channel for scheduling data transmitted through the integrated subframe before data transmission through the integrated subframe.
- the control channel may be at least one of PDCCH and EPDCCH.
- the base station may transmit a preamble in an integrated subframe and transmit a PDCCH for scheduling a PDSCH transmitted in the integrated subframe, as shown in the embodiment of FIG. 19 (a), and then transmit the PDSCH.
- the base station may transmit the PDSCH after transmitting the PDCCH scheduling the PDSCH in the integrated subframe as in the embodiment of FIG.
- the base station may transmit a preamble in an integrated subframe and start transmission of an E-PDCCH and a PDSCH for scheduling a PDSCH.
- the base station may simultaneously transmit the E-PDCCH and the PDSCH scheduling the PDSCH in the integrated subframe as in the embodiment of FIG. 19 (b).
- the size of the E-PDCCH may vary according to data scheduled by the E-PDCCH.
- the base station may transmit a control channel for scheduling data transmitted through the integrated subframe based on a boundary of a general subframe included in the integrated subframe.
- the base station may transmit a control channel for scheduling data transmitted through the integrated subframe at the start of a general subframe including the integrated subframe.
- the base station may transmit a preamble in an integrated subframe and start PDSCH transmission as shown in the embodiment of FIG. 19 (c).
- the base station may transmit a PDCCH for scheduling the PDSCH transmitted through the integrated subframe at the start time of the general subframe included in the integrated subframe.
- the base station may transmit the PDSCH after transmitting the PDCCH scheduling the PDSCH transmitted in the integrated subframe as in the embodiment of FIG. 19 (c).
- the base station may transmit the preamble in the integrated subframe and start transmitting the PDSCH as in the embodiment of FIG. 19 (d).
- the base station may transmit the E-PDCCH for scheduling the PDSCH transmitted through the integrated subframe from the start time of the general subframe included in the integrated subframe.
- the size of the E-PDCCH may vary according to data scheduled by the E-PDCCH.
- the base station may transmit the E-PDCCH and the PDSCH together to schedule the PDSCH transmitted in the integrated subframe.
- the control channel described above may include an indicator indicating whether data scheduled by the control channel is transmitted through an integrated subframe or a general subframe.
- the DCI included in the PDCCH or the E-PDCCH may include an indicator indicating whether data scheduled by the PDCCH or the E-PDCCH is transmitted through an integrated subframe or a general subframe.
- a base station transmits a control channel in an unlicensed band based on a boundary of a general subframe or a transmission start time.
- the base station may transmit the control channel at various points in the subframe.
- An embodiment in which a base station transmits a control channel at various points in a subframe will be described with reference to FIGS. 20 to 22.
- 20 shows another method of transmitting a control channel for scheduling an integrated subframe after an LBT procedure in an unlicensed band by a base station according to an embodiment of the present invention.
- the base station may transmit a control channel for scheduling data transmitted through the integrated subframe at the start of transmission of the integrated subframe.
- the base station may transmit the control channel at the start of transmission of the integrated subframe (2001, 2021), as shown in the first embodiment (2011, 2031) of Figs. 20 (a) and 20 (b).
- the terminal may receive the control channel first, and stop receiving data when the decoded control channel does not schedule data corresponding to the terminal.
- the terminal does not need to buffer data transmitted to another terminal in advance. Therefore, when the base station transmits the integrated subframe, the base station transmits a control channel for scheduling data transmitted through the integrated subframe to increase the operation efficiency of the terminal.
- the base station can access the radio resource regardless of the subframe boundary in the unlicensed band.
- the base station or the terminal may start transmission at any point in the subframe in the unlicensed band.
- the base station may first transmit a signal for occupying the aforementioned radio resource.
- the terminal may monitor a signal for occupying a radio resource.
- the terminal detects a signal for occupying a radio resource, it can be determined that the base station transmits data.
- the base station can prevent another radio communication terminal from accessing the radio communication resource before transmitting the control channel and data.
- the base station may inform the terminal that the base station starts data transmission.
- the base station may transmit a signal for occupying a radio resource to match the unit of the OFDM symbol.
- the base station may transmit a signal for occupying radio resources before transmitting the integrated subframe.
- the terminal should perform blind decoding of the control channel including control information for each OFDM symbol before receiving the control channel.
- the base station may transmit the control channel together from any one of the OFDM symbols predetermined to transmit the reference signal.
- the base station may first transmit a signal for occupying a radio resource and then transmit an integrated subframe.
- the base station may adjust the duration of a signal to occupy a radio resource so that the start of transmission of the integrated subframe corresponds to any one of the OFDM symbols predetermined to transmit the reference signal.
- the reference signal may be a cell specific reference signal (CRS).
- the reference signal may be CRS port 0 or CRS port 1.
- the index value of the OFDM symbol to which the CRS is transmitted may be at least one of 0, 4, 7, and 11.
- the terminal may receive the control information by monitoring the control channel reception from the OFDM symbol position previously designated to transmit the reference signal.
- the base station transmits an E at an OFDM symbol position that does not split downlink demodulation reference signal (DMRS) based on the OFDM symbol index of the PCell.
- DMRS downlink demodulation reference signal
- PDCCH can be transmitted.
- the base station may transmit the E-PDCCH to the OFDM symbol position 2022 that does not split the DMRS as in the second embodiment 2032 of FIG. 20 (b). This is because when the DMRS is separated by the E-PDCCH, the UE cannot use one DMRS port for decoding / demodulation of the E-PDCCH.
- the base station may transmit the E-PDCCH from the sixth OFDM symbol of the first slot of the subframe and the sixth OFDM symbol of the second slot based on the normal CP. That is, the base station uses E from one of the first OFDM symbol to the fifth OFDM symbol of the first slot of the subframe and the first to fifth OFDM symbol of the second slot based on the normal CP.
- PDCCH can be transmitted.
- the base station transmits a signal for occupying the radio resource before the integrated subframe transmission, and adjusts the duration of the signal for occupying the radio resource so that the downlink DMRS is not split.
- PDCCH may be transmitted.
- the UE may demodulate / decode a signal including the E-PDCCH for a period of time between the duration of the general subframe and then determine whether to receive the PDSCH.
- the base station can increase decoding / demodulation performance of a signal including the E-PDCCH of the terminal.
- the base station may transmit a control channel with a reference signal.
- the base station may transmit a reference signal together.
- a control channel may be transmitted from an OFDM symbol designated to transmit a reference signal.
- the terminal estimates the state of the control channel and the channel through which the data is transmitted using the reference signal, and receives and demodulates / decodes the control channel and the data using the estimated channel state. Therefore, when the base station transmits the control channel from the OFDM symbol designated to transmit the reference signal, the terminal can stably receive the control channel.
- the reference signal may be a CRS as described above.
- the index value of the OFDM symbol to which the reference signal is transmitted may be at least one of 0, 4, 7, and 11.
- the index value of the OFDM symbol in which the CRS is transmitted may be a predetermined value.
- the base station may transmit the control channel from the positions 2002 and 2003 of the OFDM symbol for transmitting the reference signal as shown in the second and third embodiments 2012 and 2013 of FIG. 20 (a).
- the base station may transmit a control channel in the OFDM symbol closest to the transmission start time of the plurality of OFDM symbol index to which the reference signal is transmitted.
- the base station may first transmit data scheduled by the control channel before transmitting the control channel.
- the base station may adjust the length of a signal occupying a radio resource, and transmit the control channel before data transmission scheduled by the control channel.
- the operation of the base station may be the same as the operation of the base station in the specific embodiment described with reference to the first embodiment (2011, 2031) of Figure 20 (a) and 20 (b).
- the base station may transmit a control channel based on the boundary of the subframe.
- the boundary of the subframe is not the integrated subframe but the boundary of the general subframe included in the integrated subframe.
- the base station may transmit a control channel at the start of a subframe.
- the base station can transmit control channels at the start time points 2004 and 2023 of the subframe. have.
- the base station may transmit data before transmitting the control channel for scheduling data. Therefore, the terminal may buffer data until the control channel is received.
- the control channel described with reference to FIG. 20 may be used for both the above-described self-carrier scheduling and cross-carrier scheduling according to a specific embodiment.
- the base station may transmit a PCell in a frequency band, for example, a licensed band, which can be accessed without a competition procedure.
- the boundary of the subframe of the SCell is aligned with the subframe boundary of the PCell.
- the base station had to transmit a partial subframe or an integrated subframe in the SCell of the unlicensed band.
- resources are allocated and transmitted in units of subframes having a certain length, for example, 1 ms. Therefore, when the base station and the terminal transmits a partial subframe or integrated subframe, the operation of the base station and the terminal may be complicated.
- the base station may set the start time of the subframe based on the start time of transmission in the SCell of the unlicensed band. In this way, the base station may transmit a general subframe at the start of the transmission. This will be described in detail with reference to FIG. 21.
- 21 illustrates a method of transmitting a control channel for scheduling a subframe having a boundary different from that of a PCell after the LBT procedure in the unlicensed band according to an embodiment of the present invention.
- the base station may set the transmission start time of the SCell transmitted in the unlicensed band to the start time of the subframe of the SCell.
- the time that the base station can occupy the radio resource may not be a multiple of the length of the subframe of the SCell.
- the base station may transmit a partial subframe at the end of the transmission.
- the base station may apply the embodiment described with reference to FIG. 20 based on the subframe boundary of the SCell.
- the base station may transmit a control channel for scheduling data transmitted through the subframe of the SCell.
- the base station may transmit a control channel (2101, 2121) at the start of transmission of a subframe of the SCell, as shown in the first embodiment (2111, 2131) of Figure 21 (a) and 21 (b).
- the terminal may receive the control channel first, and stop receiving data when the decoded control channel does not schedule data corresponding to the terminal.
- the terminal does not need to buffer data transmitted to another terminal in advance. Therefore, when the base station transmits the subframe of the SCell, the base station may transmit a control channel for scheduling data transmitted through the subframe of the SCell to increase the operation efficiency of the terminal.
- the base station may transmit a signal for occupying radio resources before transmitting the subframe of the SCell.
- the terminal should perform blind decoding of the control channel including control information for each OFDM symbol before receiving the control channel.
- the base station may transmit the control channel together from any one of the OFDM symbols predetermined to transmit the reference signal.
- the base station may first transmit a signal for occupying a radio resource and transmit a subframe of the SCell.
- the base station may adjust the duration of a signal for occupying a radio resource so that the start of subframe transmission of the SCell corresponds to any one of OFDM symbols predetermined to transmit a reference signal.
- the reference signal may be a CRS.
- the reference signal may be CRS port 0 or CRS port 1.
- the index value of the OFDM symbol to which the CRS is transmitted may be at least one of 0, 4, 7, and 11.
- the terminal may receive the control information by monitoring the reception of the control channel at a predetermined OFDM symbol position that the reference signal is to be transmitted.
- the base station may transmit the E-PDCCH to the OFDM symbol position that does not split downlink modulation reference signal (DMRS) based on the OFDM symbol index of the PCell. For example, the base station may transmit the E-PDCCH to the OFDM symbol position 2122 that does not split the DMRS as in the second embodiment 2132 of FIG. 21 (b). This is because when the DMRS is separated by the E-PDCCH, the UE cannot use one DMRS port for decoding / demodulation of the E-PDCCH.
- DMRS downlink modulation reference signal
- the base station may transmit the E-PDCCH from the sixth OFDM symbol of the first slot of the PCell subframe and the sixth OFDM symbol of the second slot based on the normal CP. That is, the base station determines from one of the first OFDM symbol to the fifth OFDM symbol of the first slot of the PCell subframe, the first OFDM symbol to the fifth OFDM symbol of the second slot based on the normal CP. E-PDCCH may be transmitted. Through this operation, the base station can increase decoding / demodulation performance of a signal including the E-PDCCH of the terminal.
- the base station may transmit a control channel with a reference signal.
- the base station may transmit a reference signal together.
- a control channel may be transmitted from an OFDM symbol location designated to transmit a reference signal.
- the terminal estimates the state of the control channel and the channel through which the data is transmitted using the reference signal, and demodulates / decodes the control channel and the data using the estimated channel state. Therefore, when the base station transmits the control channel from the OFDM symbol position where the reference signal is transmitted, the terminal can receive the control channel stably.
- the reference signal may be a CRS as described above.
- the index value of the OFDM symbol to which the reference signal is transmitted may be at least one of 0, 4, 7, and 11.
- the index value of the OFDM symbol in which the CRS is transmitted may be a predetermined value.
- the base station may transmit the control channel from the positions 2102 and 2103 of the OFDM symbol for transmitting the reference signal as shown in the second and third embodiments 2112 and 2113 of FIG.
- the base station may transmit a control channel in the OFDM symbol closest to the transmission start time point among the plurality of OFDM symbol indexes for transmitting the reference signal.
- the base station may first transmit data scheduled by the control channel before transmitting the control channel.
- the base station may adjust the length of a signal occupying a radio resource, and transmit the control channel before data transmission scheduled by the control channel.
- the operation of the base station may be the same as the operation of the base station in the specific embodiment described with reference to the first embodiment (2111, 2131) of Figure 21 (a) and 21 (b).
- the base station may transmit a control channel based on the boundary of the subframe of the PCell.
- the base station may transmit a control channel on the SCell at the start of the subframe of the PCell.
- the base station may transmit a control channel on the SCell at the start time points 2104 and 2123 of the subframe of the PCell as shown in the fourth (2014, 2033) embodiment of FIGS. 21 (a) and 21 (b).
- the base station may transmit data before transmitting the control channel for scheduling data. Therefore, the terminal may buffer data until the control channel is received.
- the control channel described with reference to FIG. 21 may be used for both the self-carrier scheduling and the cross-carrier scheduling described above according to a specific embodiment.
- the base station may transmit the PCell in a frequency band, for example, a licensed band, which can be accessed without a competition procedure.
- the base station may treat the partial subframes as individual subframes in the SCell transmitted in the unlicensed band.
- a method of transmitting a control channel by the base station will be described with reference to FIG. 22.
- FIG. 22 is a view illustrating another method of transmitting a control channel for scheduling a partial subframe after an LBT procedure in an unlicensed band by a base station according to an embodiment of the present invention.
- the base station may transmit a control channel for scheduling data transmitted through the partial subframe.
- the base station may transmit the control channel (2201, 2221) at the start of the transmission of the partial subframe, as shown in the first embodiment (2211, 2231) of Figure 22 (a) and 22 (b).
- the terminal may receive the control channel first, and stop receiving data when the decoded control channel does not schedule data corresponding to the terminal.
- the terminal does not need to buffer data transmitted to another terminal in advance. Therefore, when the base station transmits the partial subframe, the base station transmits a control channel for scheduling data transmitted through the partial subframe to increase the operation efficiency of the terminal.
- the base station may transmit a signal for occupying radio resources before transmitting the integrated subframe.
- the terminal should perform blind decoding of the control channel including control information for each OFDM symbol before receiving the control channel.
- the base station may transmit a control channel including the control information from any one of the OFDM symbol positions previously designated to transmit the reference signal.
- the base station may first transmit a signal for occupying radio resources and transmit a partial subframe as described above.
- the base station may adjust the duration of a signal to occupy a radio resource so that the start of transmission of the partial subframe corresponds to any one of OFDM symbol positions previously designated to transmit the reference signal.
- the reference signal may be a CRS.
- the reference signal may be CRS port 0 or CRS port 1.
- the index value of the OFDM symbol to which the CRS is transmitted may be at least one of 0, 4, 7, and 11.
- the terminal may receive the control information by monitoring the reception of the control channel from the OFDM symbol position previously designated to transmit the reference signal.
- the base station transmits an E at an OFDM symbol position that does not split downlink demodulation reference signal (DMRS) based on the OFDM symbol index of the PCell.
- DMRS downlink demodulation reference signal
- the base station may transmit the E-PDCCH to the OFDM symbol position 2222 that does not split the DMRS, as in the second embodiment 2232 of FIG. 22 (b). This is because when the DMRS is separated by the E-PDCCH, the UE cannot use one DMRS port for decoding / demodulation of the E-PDCCH.
- the base station may transmit the E-PDCCH from the sixth OFDM symbol of the first slot and the sixth OFDM symbol of the second slot of the subframe based on the normal CP. That is, the base station uses E from one of the first OFDM symbol to the fifth OFDM symbol of the first slot of the subframe and the first to fifth OFDM symbol of the second slot based on the normal CP. PDCCH can be transmitted. Through this, the base station can increase the decoding / demodulation performance of the signal including the E-PDCCH of the terminal.
- the base station may transmit a control channel with a reference signal.
- the base station may transmit a reference signal together.
- a control channel may be transmitted from an OFDM symbol designated to transmit a reference signal.
- the terminal estimates the state of the control channel and the channel through which the data is transmitted using the reference signal, and demodulates / decodes the control channel and the data using the estimated channel state. Therefore, when the base station transmits the control channel with the reference signal, the terminal can receive the control channel stably.
- the reference signal may be a CRS as described above.
- the index value of the OFDM symbol to which the reference signal is transmitted may be at least one of 0, 4, 7, and 11.
- the index value of the OFDM symbol in which the CRS is transmitted may be a predetermined value.
- the base station may transmit a control channel from positions 2202 and 2203 of an OFDM symbol for transmitting a reference signal.
- the base station may transmit a control channel from the OFDM symbol position closest to the transmission start time point among the plurality of OFDM symbol indexes on which the reference signal is transmitted.
- the base station may first transmit data scheduled by the control channel before transmitting the control channel.
- the base station may adjust the length of a signal occupying a radio resource, and transmit the control channel before data transmission scheduled by the control channel.
- the operation of the base station may be the same as the operation of the base station in the specific embodiment described with reference to the first embodiment (2211, 2231) of Figure 22 (a) and 22 (b).
- the base station may transmit a control channel based on the boundary of the subframe.
- the boundary of the subframe is not the partial subframe but the boundary of the general subframe.
- the base station may transmit a control channel at the start of a general subframe located after the partial subframe.
- the base station establishes a control channel at the start points 2204 and 2223 of the general subframe located after the partial subframe.
- the base station may transmit data before transmitting the control channel for scheduling data. Therefore, the terminal may buffer data until the control channel is received.
- the control channel described with reference to FIG. 22 may be used for both the self-carrier scheduling and the cross-carrier scheduling described above according to a specific embodiment.
- the base station may transmit a PCell in a frequency band that can be accessed without a contention procedure, for example, a licensed band.
- the base station may use a method of transmitting a control channel of a partial subframe when transmission starts and a method of transmitting a control channel of a partial subframe when transmission ends.
- the base station may apply the control channel transmission method described with reference to FIGS. 20 through 22 differently to a partial subframe transmitted at the start of transmission and a partial subframe transmitted at the end of transmission.
- FIG. 23 illustrates operations of a base station and a terminal according to an embodiment of the present invention.
- the base station 2301 transmits a control channel for scheduling data transmitted through a subframe and data transmitted through a partial subframe in an unlicensed band (S2301). Before transmitting the partial subframe, the base station 2301 may perform a contention procedure in the unlicensed band. In more detail, an LBT procedure or a channel sensing procedure may be performed to access an unlicensed band.
- the base station 2301 transmits an indicator indicating whether to allow the UE to receive partial subframes in the SCell to the UE through an upper layer as an RRC (Radio Resource Control) parameter. Can be.
- RRC Radio Resource Control
- the partial subframe is a partial subframe having a duration shorter than the duration of the subframe.
- the base station 2301 may transmit a control channel with a reference signal.
- the base station 2301 may start transmission of a control channel for scheduling data transmitted through the partial subframe from a time point of transmitting an OFDM symbol including a reference signal.
- the control channel may schedule only data transmitted later than the control channel.
- the reference signal may be transmitted at a predetermined time point.
- the base station 2301 may start transmission of the control channel from a time point when half of the duration of the subframe elapses from the boundary of the subframe.
- the base station 2301 may start transmission of a control channel when transmitting an OFDM symbol having an OFDM symbol index value of 7 in one subframe.
- the reference signal may be a signal for estimating a channel state of a cell transmitted in an unlicensed band.
- the reference signal may be the aforementioned CRS.
- the base station 2301 may transmit a signal for occupying radio resources of the unlicensed band before starting transmission of the control channel.
- the signal for occupying the radio resource may be at least one of the reservation signal, the initial signal, the LAA preamble, and the DRS.
- the base station 2301 may start transmitting the partial subframe at a time point not at the boundary of the subframe.
- the subframe boundary of the cell transmitted in the unlicensed band may be aligned with the subframe boundary of the cell of the licensed band.
- the base station 2301 may transmit a control channel according to various embodiments described with reference to FIGS. 17 to 22.
- the terminal 2303 receives data transmitted through the partial subframe based on the control channel (S2303). In more detail, the terminal decodes the control channel to receive data transmitted through the partial subframe.
- the terminal 2303 may monitor reception of a control channel for scheduling data transmitted through the partial subframe from a time point of receiving an OFDM symbol including a reference signal.
- the terminal may receive an indicator indicating whether to set up reception in the SCell from the base station as an RRC (Radio Resource Control) parameter from the upper layer.
- the terminal may monitor reception of a control channel for scheduling data transmitted through the partial subframe from the time point of receiving an OFDM symbol including a reference signal based on an indicator indicating whether reception is configured in the SCell.
- the terminal 2303 may receive the reference signal at a predetermined time point. In this case, the terminal 2303 may monitor the reception of the control channel from the time when half the duration of the subframe elapses from the boundary of the subframe. When a normal CP in LTE is applied, the terminal 2303 may monitor reception of a control channel when receiving an OFDM symbol having an OFDM symbol index of 7 within one subframe.
- the terminal 2303 may receive a control channel according to various embodiments described above with reference to FIGS. 17 to 22.
- the terminal 2303 may ignore the signal received before the control channel.
- the signal received before the control channel may be a signal for occupying the radio resource described above.
- the terminal 2303 may ignore a signal received before the control channel in one subframe.
- control channel may support cross carrier scheduling as well as self carrier scheduling.
- the control channel may be any one of the above-described PDCCH and E-PDCCH, and the data may be PDSCH.
- the terminal may be implemented as various types of wireless communication devices or computing devices that are guaranteed to be portable and mobile.
- the terminal may be referred to as a user equipment (UE), a station (STA), a mobile subscriber (MS), or the like.
- the base station can control and manage a cell (eg, macro cell, femto cell, pico cell, etc.) corresponding to the service area, and perform functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, and relay. have.
- the base station may be referred to as an evolved NodeB (eNB), an access point (AP), or the like.
- eNB evolved NodeB
- AP access point
- the terminal 100 may include a processor 110, a communication module 120, a memory 130, a user interface unit 140, and a display unit 150.
- the processor 110 may execute various commands or programs according to the present invention and process data in the terminal 100.
- the processor 100 may control an overall operation including each unit of the terminal 100 and may control data transmission and reception between the units.
- the processor 110 may receive / process a downlink signal according to the proposal of the present invention.
- the communication module 120 may be an integrated module that performs mobile communication using a mobile communication network and wireless LAN access using a wireless LAN.
- the communication module 120 may include a plurality of network interface cards such as the cellular communication interface cards 121 and 122 and the wireless LAN interface card 123 in an internal or external form.
- each network interface card may be independently arranged according to a circuit configuration or a purpose, unlike in FIG. 24.
- the cellular communication interface card 121 transmits and receives a radio signal with at least one of the base station 200, an external device, and a server using a mobile communication network, and performs a cellular communication service in a first frequency band based on a command of the processor 110. to provide.
- the cellular communication interface card 121 may include at least one NIC module using an LTE-Licensed frequency band.
- the cellular communication interface card 122 transmits and receives a wireless signal with at least one of the base station 200, an external device, and a server using a mobile communication network, and performs a cellular communication service in a second frequency band based on a command of the processor 110. to provide.
- the cellular communication interface card 122 may include at least one NIC module using an LTE-Unlicensed frequency band.
- the LTE-Unlicensed frequency band may be a band of 2.4 GHz or 5 GHz.
- the WLAN interface card 123 transmits / receives a wireless signal with at least one of the base station 200, an external device, and a server through a WLAN connection, and performs a WLAN service in a second frequency band based on a command of the processor 110. to provide.
- the WLAN interface card 123 may include at least one NIC module using a WLAN frequency band.
- the WLAN frequency band may be an Unlicensed radio band such as a band of 2.4 GHz or 5 GHz.
- the memory 130 stores a control program used in the terminal 100 and various data according thereto.
- the control program may include a program necessary for the terminal 100 to perform wireless communication with at least one of the base station 200, an external device, and a server.
- the user interface 140 includes various types of input / output means provided in the terminal 100.
- the display unit 150 outputs various images on the display screen.
- the base station 200 may include a processor 210, a communication module 220, and a memory 230.
- the processor 210 may execute various instructions or programs according to the present invention and process data in the base station 200.
- the processor 210 may control the overall operation including each unit of the base station 200 and control transmission and reception of data and control channels between the units.
- the processor 210 may transmit / process transmission of downlink data and a control channel according to the proposal of the present invention.
- data and control channels used according to the embodiments of FIGS. 17 to 23 may be transmitted.
- the communication module 220 may be an integrated module that performs mobile communication using a mobile communication network and wireless LAN access using a wireless LAN, such as the communication module 120 of the terminal 100.
- the communication module 120 may include a plurality of network interface cards such as the cellular communication interface cards 221 and 222 and the wireless LAN interface card 223 in an internal or external form.
- each network interface card may be independently arranged according to a circuit configuration or a purpose, unlike in FIG. 24.
- the cellular communication interface card 221 transmits and receives a radio signal with at least one of the terminal 100, an external device, and a server using a mobile communication network, and performs a cellular communication service in a first frequency band based on a command of the processor 210. to provide.
- the cellular communication interface card 221 may include at least one NIC module using an LTE-Licensed frequency band.
- the cellular communication interface card 222 transmits and receives a wireless signal with at least one of the terminal 100, an external device, and a server using a mobile communication network, and performs a cellular communication service in a second frequency band based on a command of the processor 210. to provide.
- the cellular communication interface card 222 may include at least one NIC module using an LTE-Unlicensed frequency band.
- the LTE-Unlicensed frequency band may be a band of 2.4 GHz or 5 GHz.
- the WLAN interface card 223 transmits and receives a wireless signal with at least one of the terminal 100, an external device, and a server through a WLAN connection, and performs a WLAN service in a second frequency band based on a command of the processor 210. to provide.
- the WLAN interface card 223 may include at least one NIC module using a WLAN frequency band.
- the WLAN frequency band may be an unlicensed radio band such as a band of 2.4 GHz or 5 GHz.
- blocks of a terminal and a base station logically distinguish elements of a device. Elements of the device may be mounted on one chip or on multiple chips, depending on the design of the device.
- some components of the terminal 100 such as the user interface 140 and the display unit 150, may be selectively provided in the terminal 100.
- some components of the base station 200 for example, the WLAN interface card 223 may be selectively provided in the base station 200.
- the user interface 140 and the display unit 150 may be additionally provided to the base station 200 as necessary.
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Abstract
Description
Claims (20)
- 무선 통신 시스템의 기지국에서,통신 모듈; 및프로세서를 포함하고,상기 프로세서는상기 통신 모듈을 통해 복수의 서브프레임으로 나뉜 무선 프레임을 전송하고,상기 서브프레임의 듀레이션보다 짧은 듀레이션을 갖는 부분 서브프레임을 전송하는 경우, 레퍼런스 신호를 포함하는 OFDM(Orthogonal Frequency Divisional Multiplexing) 심볼을 전송하는 시점에 상기 부분 서브프레임을 통해 전송되는 데이터를 스케줄링하는 제어 채널의 전송을 시작하는기지국.
- 제1항에서,상기 프로세서는상기 서브프레임의 경계가 아닌 시점에서 상기 부분 서브프레임의 전송을 시작하는기지국.
- 제2항에서,상기 제어 채널은상기 제어 채널보다 늦게 전송되는 데이터만을 스케줄링하는기지국.
- 제1항에서,상기 프로세서는상기 레퍼런스 신호를 미리 지정된 시점에 전송하는기지국.
- 제4항에서,상기 프로세서는상기 서브프레임의 경계로부터 상기 서브프레임의 듀레이션의 절반이 경과한 시점에서부터 상기 제어 채널의 전송을 시작하는기지국.
- 제1항에서,상기 레퍼런스 신호는상기 부분 서브프레임이 전송되는 셀의 채널 상태를 추정하기 위한 신호인기지국.
- 제1항에서,상기 프로세서는상기 제어 채널의 전송을 시작하기 전에 무선 자원을 점유하기 위한 신호를 전송하는기지국.
- 제7항에서,상기 무선 자원을 점유하기 위한 신호는 상기 기지국의 전송이 시작 됨을 나타내는기지국.
- 무선 통신 시스템의 단말에서,통신 모듈; 및프로세서를 포함하고,상기 프로세서는상기 통신 모듈을 통해 복수의 서브프레임으로 나뉜 무선 프레임을 수신하고,상기 서브프레임의 듀레이션보다 짧은 듀레이션을 갖는 부분 서브프레임을 수신하는 경우, 레퍼런스 신호를 포함하는 OFDM(Orthogonal Frequency Divisional Multiplexing) 심볼을 수신하는 시점에 상기 부분 서브프레임을 통해 전송되는 데이터를 스케줄링하는 제어 채널의 수신을 모니터링하는단말.
- 제9항에서,상기 프로세서는상기 서브프레임의 경계가 아닌 시점에서 상기 부분 서브프레임의 수신을 시작하는단말.
- 제10항에서,상기 제어 채널은상기 제어 채널보다 늦게 전송되는 데이터만을 스케줄링하는단말.
- 제9항에서,상기 프로세서는상기 레퍼런스 신호를 미리 지정된 시점에 수신하는단말.
- 제12항에서,상기 서브프레임의 경계로부터 상기 서브프레임의 듀레이션의 절반이 경과한 시점에서부터 상기 제어 채널을 수신하는단말.
- 제9항에서,상기 레퍼런스 신호는상기 부분 서브프레임이 전송되는 셀의 채널 상태를 추정하기 위한 신호인단말.
- 제9항에서,상기 프로세서는상기 부분 서브프레임을 수신하는 경우, 상기 제어 채널보다 먼저 수신된 신호를 무시하는단말.
- 제9항에서,상기 제어 채널은상기 제어 채널이 전송되는 셀이 아닌 다른 셀에서 전송되는 데이터를 스케줄링하는단말.
- 무선 통신 시스템의 단말의 동작 방법에서,복수의 서브프레임으로 나뉜 무선 프레임을 수신하는 단계를 포함하고,상기 무선 프레임을 수신하는 단계는상기 서브프레임의 듀레이션보다 짧은 듀레이션을 갖는 부분 서브프레임을 수신하는 경우, 레퍼런스 신호를 포함하는 OFDM (Orthogonal Frequency Divisional Multiplexing) 심볼을 수신하는 시점에 상기 부분 서브프레임을 통해 전송되는 데이터를 스케줄링하는 제어 채널의 수신을 모니터링하는 단계를 포함하는동작 방법.
- 제17항에서,상기 제어 채널의 수신을 모니터링하는 단계는상기 서브프레임의 경계가 아닌 시점에서 상기 부분 서브프레임의 수신을 시작하는 단계를 포함하는동작 방법.
- 제18항에서,상기 제어 채널은상기 제어 채널보다 늦게 전송되는 데이터만을 스케줄링하는동작 방법.
- 제17항에서,상기 제어 채널의 수신을 모니터링하는 단계는상기 레퍼런스 신호를 미리 지정된 시점에 수신하는 단계를 포함하는동작 방법.
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US15/893,553 US10616906B2 (en) | 2015-08-12 | 2018-02-09 | Method, apparatus, and system for transmitting control channel in unlicensed band |
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US20200178266A1 (en) | 2020-06-04 |
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