WO2017048088A1 - 듀얼 모빌리티 환경에서 채널 추정 방법 및 사용자 장치 - Google Patents
듀얼 모빌리티 환경에서 채널 추정 방법 및 사용자 장치 Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0222—Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
- H04L5/0035—Resource allocation in a cooperative multipoint environment
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
- H04L5/005—Allocation of pilot signals, i.e. of signals known to the receiver of common pilots, i.e. pilots destined for multiple users or terminals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0212—Channel estimation of impulse response
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/022—Channel estimation of frequency response
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/024—Channel estimation channel estimation algorithms
- H04L25/0258—Channel estimation using zero-forcing criteria
Definitions
- the present invention relates to mobile communications.
- 3GPP LTE long term evolution
- UMTS Universal Mobile Telecommunications System
- 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink and single carrier-frequency division multiple access (SC-FDMA) in uplink.
- OFDMA orthogonal frequency division multiple access
- SC-FDMA single carrier-frequency division multiple access
- MIMO multiple input multiple output
- a physical channel is a downlink channel PDSCH (Physical Downlink Shared) Channel (PDCCH), Physical Downlink Control Channel (PDCCH), Physical Hybrid-ARQ Indicator Channel (PHICH), Physical Uplink Shared Channel (PUSCH) and PUCCH (Physical Uplink Control Channel).
- PDSCH Physical Downlink Shared
- PDCCH Physical Downlink Control Channel
- PHICH Physical Hybrid-ARQ Indicator Channel
- PUSCH Physical Uplink Shared Channel
- PUCCH Physical Uplink Control Channel
- LTE-A LTE-Advance
- one disclosure of the present disclosure aims to provide a method for effectively performing channel estimation in a dual mobility environment.
- Another object of the present disclosure is to provide a user device capable of performing channel estimation effectively in a dual mobility environment.
- one disclosure of the present specification provides a method for estimating a channel by a user equipment.
- the method includes receiving two or more Cell-specific Reference Signals (CRSs); Dividing the two or more CRSs into two groups based on an antenna port number; Performing doppler frequency tracking on each of the divided groups; And estimating a single frequency network (SFN) channel based on the Doppler frequency tracking result performed for each group.
- CRSs Cell-specific Reference Signals
- SFN single frequency network
- the two or more CRSs may be divided into an odd group and an even group, wherein the CRS having an odd antenna port number may be divided into an odd group, and the CRS having an even antenna port number may be divided into an even group.
- the CRSs divided into odd groups and even groups may be received through different remote radio heads (RRHs).
- RRHs remote radio heads
- the dividing into two groups may be performed by dividing the two or more CRSs into two groups only when an indicator for notifying communication using the SFN channel is received.
- the indicator may be extracted from a master information block (MIB) received through a physical broadcast channel (PBCH).
- MIB master information block
- PBCH physical broadcast channel
- the indicator can be transmitted on one bit replaced to transmit the indicator among the spare bits in the MIB.
- the method may further include performing automatic frequency control based on a weighted-averaged value of the SFN channel estimation result.
- the user device includes a radio frequency (RF) unit for transmitting and receiving a radio signal; And a processor controlling the RF unit.
- the processor controls the RF unit to receive two or more Cell-specific Reference Signals (CRSs); Divide the two or more CRSs into two groups based on the antenna port number; Perform Doppler frequency tracking for each of the separated groups; And estimating a single frequency network (SFN) channel based on the Doppler frequency tracking result performed for each group.
- CRSs Cell-specific Reference Signals
- SFN single frequency network
- effective dual frequency tracking may be performed in a dual mobility environment to prevent performance degradation of SFN channel estimation.
- 1 is an exemplary view showing a wireless communication system.
- FIG. 2 shows a structure of a radio frame according to FDD in 3GPP LTE.
- 3 is an exemplary diagram illustrating a resource grid for one uplink or downlink slot in 3GPP LTE.
- 5 shows a structure of an uplink subframe in 3GPP LTE.
- FIG. 6 through 8 illustrate some examples of a cell-specific reference signal (CRS) structure when using one or more antennas.
- CRS cell-specific reference signal
- DRS Dedicated RS
- DMRS DeModulation RS
- 13A to 13C show some simulation results showing channel characteristics of two Doppler frequencies.
- 14A and 14B are some simulation results showing the performance of channel estimation in a dual mobility environment.
- 16 shows an example of a structure of a conventional CRS channel estimator.
- FIG 17 shows an example of a structure of a CRS channel estimator according to the present specification.
- FIG. 18 is a flowchart illustrating a channel estimation method according to the present specification.
- FIG. 19 is a block diagram illustrating a wireless communication system in which the disclosures herein are implemented.
- first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.
- first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.
- LTE 3rd Generation Partnership Project
- LTE-A 3rd Generation Partnership Project LTE
- LTE-A 3rd Generation Partnership Project LTE
- LTE includes LTE and / or LTE-A.
- the user equipment used below may be fixed or mobile, and may include a terminal, a user equipment (UE), a wireless device, a mobile terminal (MT), a mobile equipment (ME), and an MS. (mobile station), user terminal (UT), subscriber station (SS), handheld device (Handheld Device), may be called in other terms, such as AT (Access Terminal).
- UE user equipment
- MT mobile terminal
- ME mobile equipment
- MS MS.
- UT user terminal
- SS subscriber station
- Handheld Device may be called in other terms, such as AT (Access Terminal).
- base station generally refers to a fixed station (fixed station) for communicating with user equipment, and includes an evolved-NodeB (eNB), a base transceiver system (BTS), and an access point Etc. may be called.
- eNB evolved-NodeB
- BTS base transceiver system
- Etc access point
- 1 is an exemplary view showing a wireless communication system.
- a wireless communication system includes at least one base station 10.
- Each base station 10 provides a communication service for a particular geographic area (generally called a cell) 10a, 10b, 10c.
- the user device 20 typically belongs to one cell, and the cell to which the user device 20 belongs is called a serving cell.
- a base station that provides a communication service for a serving cell is called a serving BS. Since the wireless communication system is a cellular system, there are other cells adjacent to the serving cell. Another cell adjacent to the serving cell is called a neighbor cell.
- a base station that provides communication service for a neighbor cell is called a neighbor BS. The serving cell and the neighbor cell are relatively determined based on the wireless device.
- downlink means communication from the base station 10 to the user device 20
- uplink means communication from the user device 20 to the base station 10.
- the transmitter may be part of the base station 10 and the receiver may be part of the user device 20.
- the transmitter may be part of the user device 20 and the receiver may be part of the base station 10.
- the radio frame shown in FIG. 2 is a 3rd Generation Partnership Project (3GPP) TS 36.211 V8.2.0 (2008-03) "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation (Release) 8) ".
- 3GPP 3rd Generation Partnership Project
- a radio frame consists of 10 subframes, and one subframe consists of two slots. Slots in a radio frame are numbered from 0 to 19 slots.
- the time taken for one subframe to be transmitted is called a transmission time interval (TTI).
- TTI may be referred to as a scheduling unit for data transmission.
- one radio frame may have a length of 10 ms
- one subframe may have a length of 1 ms
- one slot may have a length of 0.5 ms.
- the structure of the radio frame is merely an example, and the number of subframes included in the radio frame or the number of slots included in the subframe may be variously changed.
- one slot may include a plurality of OFDM symbols. How many OFDM symbols are included in one slot may vary depending on a cyclic prefix (CP).
- CP cyclic prefix
- 3 is 3GPP In LTE An example diagram illustrating a resource grid for one uplink or downlink slot.
- an uplink slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain, and includes NRB resource blocks (RBs) in a frequency domain. do.
- the number of resource blocks (RBs), that is, NRBs may be any one of 6 to 110.
- an example of one resource block includes 7 ⁇ 12 resource elements including 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain, but the number of subcarriers and the number of OFDM symbols in the resource block is equal to this. It is not limited.
- the number of OFDM symbols or the number of subcarriers included in the resource block may vary. That is, the number of OFDM symbols may be changed according to the length of the above-described CP.
- 3GPP LTE defines that 7 OFDM symbols are included in one slot in the case of a normal CP, and 6 OFDM symbols are included in one slot in the case of an extended CP.
- the OFDM symbol is used to represent one symbol period, and may be referred to as an SC-FDMA symbol, an OFDMA symbol, or a symbol period according to a system.
- the RB includes a plurality of subcarriers in the frequency domain in resource allocation units.
- the number NUL of resource blocks included in an uplink slot depends on an uplink transmission bandwidth set in a cell.
- Each element on the resource grid is called a resource element.
- the number of subcarriers in one OFDM symbol may be selected and used among 128, 256, 512, 1024, 1536, and 2048.
- a resource grid for one uplink slot may be applied to a resource grid for a downlink slot.
- E-UTRA Evolved Universal Terrestrial Radio Access
- Physical Channels and Modulation Release 10
- the radio frame includes 10 subframes indexed from 0 to 9.
- One subframe includes two consecutive slots.
- the radio frame includes 20 slots.
- the time it takes for one subframe to be transmitted is called a transmission time interval (TTI).
- TTI transmission time interval
- one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.
- One slot may include a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain.
- OFDM symbol is only for representing one symbol period in the time domain, since 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink (DL), multiple access scheme or name There is no limit on.
- OFDM symbol may be called another name such as a single carrier-frequency division multiple access (SC-FDMA) symbol, a symbol period, and the like.
- SC-FDMA single carrier-frequency division multiple access
- FIG. 4 it is illustrated that 7 OFDM symbols are included in one slot by assuming a normal CP.
- the number of OFDM symbols included in one slot may change according to the length of a cyclic prefix (CP). That is, as described above, according to 3GPP TS 36.211 V10.4.0, one slot includes 7 OFDM symbols in a normal CP, and one slot includes 6 OFDM symbols in an extended CP.
- CP cyclic prefix
- a resource block is a resource allocation unit and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain and the resource block includes 12 subcarriers in the frequency domain, one resource block includes 7 ⁇ 12 resource elements (REs). It may include.
- the DL (downlink) subframe is divided into a control region and a data region in the time domain.
- the control region includes up to three OFDM symbols preceding the first slot in the subframe, but the number of OFDM symbols included in the control region may be changed.
- a physical downlink control channel (PDCCH) and another control channel are allocated to the control region, and a PDSCH is allocated to the data region.
- PDCH physical downlink control channel
- a physical channel in 3GPP LTE is a physical downlink shared channel (PDSCH), a physical downlink shared channel (PUSCH), a physical downlink control channel (PDCCH), and a physical channel (PCFICH). It may be divided into a Control Format Indicator Channel (PHICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a Physical Uplink Control Channel (PUCCH).
- PDSCH physical downlink shared channel
- PUSCH physical downlink shared channel
- PDCCH physical downlink control channel
- PCFICH physical channel
- It may be divided into a Control Format Indicator Channel (PHICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a Physical Uplink Control Channel (PUCCH).
- PHICH Control Format Indicator Channel
- PHICH Physical Hybrid-ARQ Indicator Channel
- PUCCH Physical Uplink Control Channel
- the PCFICH transmitted in the first OFDM symbol of the subframe carries a control format indicator (CFI) regarding the number of OFDM symbols (that is, the size of the control region) used for transmission of control channels in the subframe.
- CFI control format indicator
- the user device first receives the CFI on the PCFICH and then monitors the PDCCH.
- the PCFICH does not use blind decoding and is transmitted on a fixed PCFICH resource of a subframe.
- the PHICH carries a positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for a UL hybrid automatic repeat request (HARQ).
- ACK positive-acknowledgement
- NACK negative-acknowledgement
- HARQ UL hybrid automatic repeat request
- An ACK / NACK signal for uplink (UL) data on the PUSCH transmitted by the user device is transmitted on the PHICH.
- the Physical Broadcast Channel (PBCH) is transmitted in the preceding four OFDM symbols of the second slot of the first subframe of the radio frame.
- the PBCH carries system information necessary for the user equipment to communicate with the base station, and the system information transmitted through the PBCH is called a master information block (MIB).
- MIB master information block
- SIB system information block
- the PDCCH includes resource allocation and transmission format of downlink-shared channel (DL-SCH), resource allocation information of uplink shared channel (UL-SCH), paging information on PCH, system information on DL-SCH, and random access transmitted on PDSCH. Resource allocation of higher layer control messages, such as responses, sets of transmit power control commands for individual user devices in any group of user devices, activation of voice over internet protocol (VoIP), and the like.
- a plurality of PDCCHs may be transmitted in the control region, and the user device may monitor the plurality of PDCCHs.
- the PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs).
- CCEs control channel elements
- CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel.
- the CCE corresponds to a plurality of resource element groups.
- the format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.
- DCI downlink control information
- PDSCH also called DL grant
- PUSCH resource allocation also called UL uplink grant
- VoIP Voice over Internet Protocol
- the base station determines the PDCCH format according to the DCI to be sent to the user equipment, and attaches a cyclic redundancy check (CRC) to the control information.
- CRC cyclic redundancy check
- RNTI a unique radio network temporary identifier
- the PDCCH is for a specific user device, a unique identifier of the user device, for example, a cell-RNTI (C-RNTI) may be masked to the CRC.
- C-RNTI cell-RNTI
- a paging indication identifier for example, p-RNTI (P-RNTI) may be masked to the CRC.
- SI-RNTI system information-RNTI
- RA-RNTI random access-RNTI
- blind decoding is used to detect the PDCCH.
- Blind decoding is a method of demasking a desired identifier in a cyclic redundancy check (CRC) of a received PDCCH (referred to as a candidate PDCCH) and checking a CRC error to determine whether the corresponding PDCCH is its control channel.
- the base station determines the PDCCH format according to the DCI to be sent to the user equipment, attaches the CRC to the DCI, and masks a unique identifier (referred to as Radio Network Temporary Identifier (RNTI)) to the CRC according to the owner or purpose of the PDCCH.
- RNTI Radio Network Temporary Identifier
- the uplink channel includes a PUSCH, a PUCCH, a sounding reference signal (SRS), and a physical random access channel (PRACH).
- PUSCH PUSCH
- PUCCH Physical Uplink Control Channel
- SRS sounding reference signal
- PRACH physical random access channel
- 5 shows a structure of an uplink subframe in 3GPP LTE.
- an uplink subframe may be divided into a control region and a data region in the frequency domain.
- a physical uplink control channel (PUCCH) for transmitting uplink control information is allocated to the control region.
- the data area is allocated a PUSCH (Physical Uplink Shared Channel) for transmitting data (in some cases, control information may also be transmitted).
- PUSCH Physical Uplink Shared Channel
- PUCCH for one user equipment is allocated as an RB pair in a subframe.
- Resource blocks belonging to a resource block pair occupy different subcarriers in each of a first slot and a second slot.
- the frequency occupied by RBs belonging to the RB pair allocated to the PUCCH is changed based on a slot boundary. This is called that the RB pair allocated to the PUCCH is frequency-hopped at the slot boundary.
- the user equipment may obtain frequency diversity gain by transmitting uplink control information through different subcarriers over time.
- m is a location index indicating a logical frequency domain location of a resource block pair allocated to a PUCCH in a subframe.
- the uplink control information transmitted on the PUCCH includes a hybrid automatic repeat request (HARQ) acknowledgment (ACK) / non-acknowledgement (NACK), a channel quality indicator (CQI) indicating a downlink channel state, and an uplink radio resource allocation request. (scheduling request).
- HARQ hybrid automatic repeat request
- ACK acknowledgment
- NACK non-acknowledgement
- CQI channel quality indicator
- the PUSCH is mapped to the UL-SCH, which is a transport channel.
- the uplink data transmitted on the PUSCH may be a transport block which is a data block for the UL-SCH transmitted during the TTI.
- the transport block may be user information.
- the uplink data may be multiplexed data.
- the multiplexed data may be a multiplexed transport block and control information for the UL-SCH.
- control information multiplexed with data may include a CQI, a precoding matrix indicator (PMI), a HARQ, a rank indicator (RI), and the like.
- the uplink data may consist of control information only.
- Reference signals are generally transmitted in sequence.
- the reference signal sequence may use a PSK-based computer generated sequence.
- PSKs include binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK).
- the reference signal sequence may use a constant amplitude zero auto-correlation (CAZAC) sequence.
- CAZAC sequences are ZC-based sequences, ZC sequences with cyclic extensions, ZC sequences with truncation, etc. There is this.
- the reference signal sequence may use a pseudo-random (PN) sequence.
- PN sequences include m-sequences, computer generated sequences, Gold sequences, and Kasami sequences.
- the reference signal sequence may use a cyclically shifted sequence.
- the reference signal may be classified into a cell-specific RS (CRS), an MBSFN reference signal, and a UE-specific RS.
- CRS is a reference signal transmitted to all terminals in a cell and used for channel estimation.
- MBSFN reference signal may be transmitted in a subframe allocated for MBSFN transmission.
- the UE-specific reference signal may be referred to as a reference signal received by a specific terminal or a specific terminal group in a cell (dedicated reference signal (DRS)).
- DRS dedicated reference signal
- a specific terminal or a specific terminal group is mainly used for data demodulation.
- FIG. 7 illustrates a CRS structure when the base station uses one antenna
- FIG. 8 illustrates a case where the base station uses two antennas
- FIG. 9 illustrates a case where the base station uses four antennas.
- the CRS structure may be used to support the features of the LTE-A system. For example, it may be used to support features such as Coordinated Multi-Point (CoMP) transmission and reception scheme or spatial multiplexing.
- CoMP Coordinated Multi-Point
- the CRS may be used for channel quality measurement, CP detection, time / frequency synchronization, and the like.
- 'R0' represents a reference signal for the first antenna
- 'R1' represents a reference signal for the second antenna
- 'R2' represents a reference signal for the third antenna
- 'R3' represents a reference signal for the fourth antenna.
- Positions in subframes of R0 to R3 do not overlap with each other.
- l is the position of the OFDM symbol in the slot l in the normal CP has a value between 0 and 6.
- a reference signal for each antenna is located at six subcarrier intervals.
- the number of R0 and the number of R1 in the subframe is the same, the number of R2 and the number of R3 is the same.
- the number of R2 and R3 in the subframe is less than the number of R0 and R1. Resource elements used for the reference signal of one antenna are not used for the reference signal of another antenna. This is to avoid interference between antennas.
- the CRS is always transmitted by the number of antennas regardless of the number of streams.
- the CRS has an independent reference signal for each antenna.
- the location of the frequency domain and the location of the time domain in the subframe of the CRS are determined regardless of the UE.
- the CRS sequence multiplied by the CRS is also generated regardless of the terminal. Therefore, all terminals in the cell can receive the CRS.
- the position and the CRS sequence in the subframe of the CRS may be determined according to the cell ID.
- the location in the time domain in the subframe of the CRS may be determined according to the number of antennas and the number of OFDM symbols in a resource block.
- the location of the frequency domain in the subframe of the CRS may be determined according to the number of the antenna, the cell ID, the OFDM symbol index l, the slot number in the radio frame, and the like.
- the CRS sequence may be applied in units of OFDM symbols in one subframe.
- the CRS sequence may vary according to a cell ID, a slot number in one radio frame, an OFDM symbol index in a slot, a type of CP, and the like.
- the number of reference signal subcarriers for each antenna on one OFDM symbol is two.
- the number of reference signal subcarriers for each antenna on one OFDM symbol is 2 ⁇ N RB . Therefore, the length of the CRS sequence is 2 ⁇ N RB .
- Equation 2 shows an example of the CRS sequence r (m).
- n is 0,1, ..., 2N RB max -1 .
- 2N RB max is the number of resource blocks corresponding to the maximum bandwidth.
- 2N RB max is 110 in 3GPP LTE system.
- c (i) is a pseudo random sequence in a PN sequence and may be defined by a Gold sequence of length-31. Equation 3 shows an example of the gold sequence c (n).
- x 1 (i) is the first m-sequence and x 2 (i) is the second m-sequence.
- the first m-sequence or the second m-sequence may be initialized for each OFDM symbol according to a cell ID, a slot number in one radio frame, an OFDM symbol index in a slot, a type of CP, and the like.
- only a portion of the 2 ⁇ N RB length may be selected and used in a reference signal sequence generated with a 2 ⁇ 2N RB max length.
- the CRS may be used for estimation of channel state information (CSI) in the LTE-A system.
- CSI channel state information
- a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and the like may be reported from the terminal when necessary through the estimation of the CSI.
- CQI channel quality indicator
- PMI precoding matrix indicator
- RI rank indicator
- FIG. 9 shows an example of a DRS structure in a normal CP.
- a subframe includes 14 OFDM symbols.
- 'R5' represents a reference signal of the antenna for transmitting the DRS.
- Reference subcarriers are positioned at four subcarrier intervals on one OFDM symbol including a reference symbol.
- 10 shows an example of a DRS structure in an extended CP.
- a subframe includes 12 OFDM symbols.
- Reference signal subcarriers on one OFDM symbol are located at three subcarrier intervals. This may be referred to Section 6.10.3 of 3GPP TS 36.211 V8.2.0 (2008-03).
- the location of the frequency domain and the time domain within the subframe of the DRS may be determined according to a resource block allocated for PDSCH transmission.
- the DRS sequence may be determined according to the terminal ID, and only a specific terminal corresponding to the terminal ID may receive the DRS.
- the DRS sequence may also be obtained by Equations 1 and 2 above. However, m in Equation 1 is determined by N RB PDSCH .
- N RB PDSCH is the number of resource blocks corresponding to a bandwidth corresponding to PDSCH transmission.
- the length of the DRS sequence may vary depending on the N RB PDSCH . That is, the length of the DRS sequence may vary according to the amount of data allocated to the terminal.
- the first m-sequence (x 1 (i)) or the second m-sequence (x 2 (i)) of Equation 1 is a cell ID, a position of a subframe in one radio frame, a terminal ID, etc. in every subframe Can be initialized accordingly.
- the DRS sequence may be generated for each subframe and applied in units of OFDM symbols.
- the number of reference signal subcarriers per resource block is 12 and the number of resource blocks is N RB PDSCH .
- the total number of reference signal subcarriers is 12 x N RB PDSCH . Therefore, the length of the DRS sequence is 12 ⁇ N RB PDSCH .
- m is 0, 1, ..., 12N RB PDSCH -1.
- DRS sequences are mapped to reference symbols in order. First, a DRS sequence is mapped to a reference symbol in ascending order of subcarrier indexes in one OFDM symbol and then to the next OFDM symbol.
- the DRS may be used as a demodulation reference signal (DMRS) for PDSCH demodulation. That is, the DMRS may be a concept in which the DRS of the LTE Rel-8 system used for beamforming is extended to a plurality of layers. PDSCH and DMRS may follow the same precoding operation. DMRS may be transmitted only in a resource block or a layer scheduled by a base station, and maintains orthogonality with each other.
- DMRS demodulation reference signal
- FIG. 11 shows an example of a DMRS structure.
- CSI-RS can use the CRS of the LTE Rel-8 system as it is.
- DMRS is transmitted in the last two OFDM symbols of each slot, that is, the sixth, seventh, thirteenth and fourteenth OFDM symbols.
- the DMRSs are mapped to the 1st, 2nd, 6th, 7th, 11th, and 12th subcarriers in the OFDM symbol in which the DMRS is transmitted.
- the CRS may be used simultaneously with the DRS.
- the receiver may reduce interference of a reference signal received from an adjacent cell, thereby improving performance of channel estimation.
- the predefined sequence may be any one of a PN sequence, an m-sequence, a Walsh hadamard sequence, a ZC sequence, a GCL sequence, a CAZAC sequence, and the like.
- the predefined sequence may be applied in units of OFDM symbols in one subframe, and another sequence may be applied according to a cell ID, a subframe number, an OFDM symbol position, a terminal ID, and the like.
- At least one Remote Radio Head (RRH) 30 is configured along a movement path (eg, a railway of a high speed rail) of the UE 10 to provide a service to the UE 10 in a dual mobility environment. Can be.
- One or more RRHs 30 provide a service to the UE 10 through a base band unit (BBU) 40.
- BBU base band unit
- UE 01 and RRH 40 then use the SFN channel.
- the RRH 30 is a device in which the radio frequency portion of the base station is separated.
- the BBU 40 is a device in which the baseband portion of the base station is separated.
- the UE 10 located in the means of transportation is connected to two RRHs RRH 1 and RRH 2 , respectively, by radio link.
- the RRH 2 present in the direction in which the UE 10 moves and the RRH 1 present in the direction in which the UE 10 has already passed are only opposite directions with respect to the UE 10, and the relative speeds are the same.
- the UE 10 receives a channel including a Doppler frequency from RRH 1 and RRH 2 , respectively. That is, the UE 10 receives a channel including two Doppler frequencies having different signs from RRH 1 and RRH 2 .
- Figure 13a To 10c shows some simulation results showing channel characteristics in two Doppler frequency situations.
- FIG. 13A illustrates a Doppler shift for a signal respectively received from a plurality of RRHs 30 connected to a moving UE 10.
- 13B shows the distance between the moving UE 10 and each RRH 30.
- FIG. 13C shows the strength of the signal received at the UE 10 moving from each RRH 30.
- the current LTE or LTE-A standard lacks a definition for a dual mobility environment.
- the current LTE or LTE-A standard does not specifically define the operation of a wireless terminal for two Doppler frequencies.
- a typical wireless terminal in a dual mobility environment performs frequency estimation by performing single frequency tracking.
- a channel estimator having a very high complexity is required for the wireless terminal to perform dual frequency tracking in a dual mobility environment.
- FIG. 14A shows the adaptive performance of a radio link in a dual mobility environment.
- FIG. 14B shows the performance of a fixed reference channel (FRC) for the adaptive performance of the radio link shown in FIG. 11A.
- FRC fixed reference channel
- Figs. 14A and 14B in the case of the existing wireless terminal performing a single frequency tracking, the performance of channel estimation is greatly degraded when the moving speed is increased.
- HUE high speed scenario enabled UE
- the performance of the channel estimation does not significantly decrease, but the complexity of the channel estimator is excessively increased, thereby increasing the amount of computation of the channel estimation. And disadvantages such as increased power consumption.
- embodiments according to the present specification proposes a method of performing dual frequency tracking to prevent performance degradation in the SFN channel and not increasing the complexity of channel estimation.
- the base station 20 needs to inform the UE 10 that the current situation is the SFN channel environment.
- the UE 10 recognizing that it is an SFN channel environment will perform the methods proposed herein.
- the base station 20 is described in the concept of including any one of the RRH 30 and the BBU 40, or both the RRH 30 and the BBU 40.
- the base station 20 may transmit a signal previously promised to the UE 10.
- a signal for letting the UE 10 know that the SFN channel environment is referred to as DualFreqTrack.
- the DualFreqTrack signal may be one bit of information. For example, when the value of DualFreqTrack is 1, it may indicate that it is an SFN channel environment. When the value of DualFreqTrack is 0, it may indicate that it is not an SFN channel environment.
- the base station 20 may transmit DualFreqTrack through the following method.
- the base station 20 may transmit DualFreqTrack using the SIB transmitted through the physical downlink shared channel (PDSCH).
- PDSCH physical downlink shared channel
- the UE 10 may not perform dual frequency tracking until the SIB is received through the PDSCH.
- the base station 20 may transmit DualFreqTrack using the MIB transmitted through the physical broadcast channel (PBCH).
- PBCH physical broadcast channel
- the MIB transmitted through the PBCH consists of a total of 40 bits. However, practically, the bits used to transmit MIB information are 30 bits, and the remaining 10 bits are configured as spares. DualFreqTrack can be transmitted by utilizing one of these 10 bits. In this case, the UE 10 may perform dual frequency tracking as soon as only the PBCH is received. In addition, the existing wireless terminal is designed to ignore the pre-configured 10-bit, it is backward compatible in terms of signaling.
- An example of the structure of the MIB including the DualFreqTrack may be as follows.
- the base station 20 may transmit the CRS as follows to reduce the complexity of the dual frequency tracking.
- the BBU 40 divides the CRS to be transmitted by the number of antennas into an odd group and an even group. For example, when four antennas are used, the BBU 40 may divide a CRS to be transmitted into a group consisting of CRS 0 and CRS 2 and a group consisting of CRS 1 and CRS 3.
- CRS 0 is a reference signal for the first antenna port
- CRS 1 is a reference signal for the second antenna port
- CRS 2 is a reference signal for the third antenna port
- CRS 3 is a reference signal for the fourth antenna port.
- the BBU 40 assigns the divided odd and even groups to different adjacent RRHs 30, respectively. For example, the BBU 40 may assign an odd group to RRH 1 and an even group to RRH 2 .
- the UE 10 performs channel estimation as follows.
- the UE 10 divides the received CRS into an odd group and an even group. For example, when using four antennas, the UE 10 divides the received CRS into a group consisting of CRT 0 and CRS 2 and a group consisting of CRS 1 and CRS 3.
- the UE 10 estimates the dual doppler frequency for each group that is divided. At this time, the Doppler estimation for each group may be performed in the same manner as the conventional method. In addition, it can be determined that the statistical characteristics of the odd group and the even group are the same.
- the UE 10 performs channel estimation using a channel estimation parameter preset for each group based on the double Doppler frequency estimated for each group.
- the channel estimation parameters may be different for each group.
- the UE 10 performs automatic frequency control (AFC) based on a weighted-averaged value of the channel power weights of the groups for the dual frequency tracking result estimated for each group. .
- AFC automatic frequency control
- 16 is a conventional CRS channel Estimator Shows an example of the structure .
- 17 shows an example of a structure of a CRS channel estimator according to the present specification.
- the CRS channel estimator according to the present specification can be implemented using only one additional Doppler frequency tracker and path masking. Exemplary structures of a conventional CRS channel estimator and a CRS channel estimator according to the present specification are as shown in FIGS. 16 and 17.
- channel estimation can be performed while minimizing an increase in the complexity of the channel estimator.
- port 7 and port 8 are allocated to one UE 10 and transmitted.
- substantially only single layer transmission is possible for the transmission for the resource element (RE). Since it is expected that there will be almost no situation in which multiple links exist in the SFN channel environment, per-port RRH allocation as described above will be possible.
- RE resource element
- the DMRS signal is orthogonal covering applied to the 3rd, 6th, 9th, and 12th OFDM symbols for the transmission mode (TM) 7 based on the time axis, and 6, 7, 12 for the TM 8/9/10.
- TM transmission mode
- TM 8/9/10 orthogonal covering
- the OFDM symbols 3 and 8 are grouped into one group
- the OFDM symbols 6 and 12 are grouped into another group and assigned to the RRHs 30 of different groups, thereby describing the CRS. May be applied.
- OFDM symbols 6 and 12 are grouped into one group
- OFDM symbols 7 and 12 are grouped into one group and assigned to RRHs 30 of different groups to orthogonality. Transmission is possible without damage.
- compensation of channel estimation may be performed by compensating through each Doppler frequency estimated from CRS ports corresponding to the same group.
- the operation of the base station for DMRS-based transmission may be performed in the same manner as the CRS-based transmission described above.
- FIG. 18 is a flowchart illustrating a channel estimation method according to the present specification.
- DualFreqTrack is an indicator for notifying that communication is performed using the SFN channel.
- DualFreqTrack can be extracted from the MIB received via the PBCH.
- DualFreqTrack may be transmitted through one bit replaced for DualFreqTrack transmission of the reserved bits in the MIB.
- the UE 10 receives two or more CRSs (S200).
- the UE 10 divides the received two or more CRSs into two groups based on the antenna port number (S300).
- the UE 10 may classify two or more CRSs into two groups only when a signal for DualFreqTrack is received.
- the UE 10 may divide two or more CRSs into an odd group and an even group.
- the UE 10 may be divided into an odd group of CRSs having an odd antenna port number, and an even group of CRSs having an even antenna port number.
- CRSs divided into odd groups and even groups may be received through different RRHs 30.
- the UE 10 performs Doppler frequency tracking on each of the divided groups (S400).
- the UE 10 estimates the SFN channel based on the Doppler frequency tracking result performed for each group (S500). Furthermore, the UE 10 may perform automatic frequency adjustment (AFC) based on a weighted average value for the SFN channel estimation result.
- AFC automatic frequency adjustment
- Embodiments of the invention may be implemented through various means.
- embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.
- the method according to embodiments of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs). Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.
- ASICs application specific integrated circuits
- DSPs digital signal processors
- DSPDs digital signal processing devices
- PLDs programmable logic devices
- FPGAs Field programmable gate arrays
- processors controllers, microcontrollers, microprocessors, and the like.
- the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the functions or operations described above.
- the software code may be stored in a memory unit and driven by a processor.
- the memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means. Specifically, this will be described with reference to FIG. 21.
- Block diagram 19 illustrates a wireless communication system in which the disclosures herein are implemented. Block diagram .
- the base station 20 includes a processor 21, a memory 22, and an RF unit 23.
- the memory 202 is connected to the processor 21 and stores various information for driving the processor 21.
- the RF unit 23 is connected to the processor 21 to transmit and / or receive a radio signal.
- the processor 21 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the base station may be implemented by the processor 21.
- the user device 10 includes a processor 11, a memory 12, and an RF unit 13.
- the memory 12 is connected to the processor 11 and stores various information for driving the processor 11.
- the RF unit 13 is connected to the processor 11 and transmits and / or receives a radio signal.
- the processor 11 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the user device may be implemented by the processor 11.
- the processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices.
- the memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device.
- the RF unit may include a baseband circuit for processing a radio signal.
- the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function.
- the module may be stored in memory and executed by a processor.
- the memory may be internal or external to the processor and may be coupled to the processor by various well known means.
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Abstract
Description
Claims (14)
- 사용자 장치(User Equipment)가 채널을 추정하는 방법으로서,둘 이상의 CRS(Cell-specific Reference Signal)를 수신하는 단계;상기 둘 이상의 CRS를 안테나 포트 번호를 기준으로, 두 개의 군으로 구분하는 단계;상기 구분된 각각의 군에 대하여, 도플러 주파수 추적(doppler frequency tracking)을 수행하는 단계; 및상기 각각의 군에 대하여 수행된 도플러 주파수 추적 결과를 기초로, SFN(Single Frequency Network) 채널을 추정하는 단계를 포함하는, 채널 추정 방법.
- 제1 항에 있어서, 상기 두 개의 군으로 구분하는 단계는상기 둘 이상의 CRS를 홀수 군과 짝수 군으로 구분하되, 상기 안테나 포트 번호가 홀수인 CRS는 홀수 군으로, 상기 안테나 포트 번호가 짝수인 CRS는 짝수 군으로 구분하는 것을 특징으로 하는, 채널 추정 방법.
- 제2 항에 있어서, 상기 홀수 군과 짝수 군으로 구분된 CRS는각각 서로 다른 RRH(Remote Radio Head)를 통해 수신되는 것을 특징으로 하는, 채널 추정 방법.
- 제1 항에 있어서, 상기 두 개의 군으로 구분하는 단계는상기 SFN 채널을 이용하여 통신을 수행함을 알리기 위한 지시자가 수신된 경우에 한하여, 상기 둘 이상의 CRS를 두 개의 군으로 구분하는 것을 특징으로 하는, 채널 추정 방법.
- 제4 항에 있어서, 상기 지시자는PBCH(Physical Broadcast Channel)을 통해 수신된 MIB(Master Information Block)로부터 추출되는 것을 특징으로 하는, 채널 추정 방법.
- 제5 항에 있어서, 상기 지시자는상기 MIB 내의 예비(spare) 비트 중 상기 지시자를 전송하기 위해 대체된 1비트를 통해 전송되는 것을 특징으로 하는, 채널 추정 방법.
- 제5 항에 있어서,상기 SFN 채널 추정 결과에 대한 가중 평균(weighted-averaged) 값을 기초로, 자동 주파수 조정(automatic frequency control)을 수행하는 단계를 더 포함하는 것을 특징으로 하는, 채널 추정 방법.
- 채널을 추정하는 사용자 장치(User Equipment)로서,무선 신호를 송수신하는 RF(Radio Frequency) 부; 및상기 RF부를 제어하는 프로세서(processor)를 포함하되, 상기 프로세서는상기 RF 부를 제어하여, 둘 이상의 CRS(Cell-specific Reference Signal)를 수신하고;상기 둘 이상의 CRS를 안테나 포트 번호를 기준으로, 두 개의 군으로 구분하고;상기 구분된 각각의 군에 대하여, 도플러 주파수 추적(doppler frequency tracking)을 수행하고; 및상기 각각의 군에 대하여 수행된 도플러 주파수 추적 결과를 기초로, SFN(Single Frequency Network) 채널을 추정하는 절차를 수행하는, 사용자 장치.
- 제8 항에 있어서, 상기 프로세서는상기 둘 이상의 CRS를 홀수 군과 짝수 군으로 구분하되, 상기 안테나 포트 번호가 홀수인 CRS는 홀수 군으로, 상기 안테나 포트 번호가 짝수인 CRS는 짝수 군으로 구분하는 것을 특징으로 하는, 사용자 장치.
- 제9 항에 있어서, 상기 홀수 군과 짝수 군으로 구분된 CRS는각각 서로 다른 RRH(Remote Radio Head)를 통해 수신되는 것을 특징으로 하는, 사용자 장치.
- 제8 항에 있어서, 상기 프로세서는상기 SFN 채널을 이용하여 통신을 수행함을 알리기 위한 지시자가 수신된 경우에 한하여, 상기 둘 이상의 CRS를 두 개의 군으로 구분하는 것을 특징으로 하는, 사용자 장치.
- 제11 항에 있어서, 상기 지시자는PBCH(Physical Broadcast Channel)을 통해 수신된 MIB(Master Information Block)로부터 추출되는 것을 특징으로 하는, 사용자 장치.
- 제12 항에 있어서, 상기 지시자는상기 MIB 내의 예비(spare) 비트 중 상기 지시자를 전송하기 위해 대체된 1비트를 통해 전송되는 것을 특징으로 하는, 사용자 장치.
- 제8 항에 있어서, 상기 프로세서는상기 SFN 채널 추정 결과에 대한 가중 평균(weighted-averaged) 값을 기초로, 자동 주파수 조정(automatic frequency control)을 수행하는 절차를 더 수행하는 것을 특징으로 하는, 사용자 장치.
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CN107635294B (zh) * | 2017-09-22 | 2021-06-29 | ***通信集团江苏有限公司 | 基站子***、信号传输方法、基站设备和存储介质 |
CN111149303A (zh) * | 2017-09-24 | 2020-05-12 | Lg电子株式会社 | 用于发送和接收反馈信息的方法及其车辆 |
CN111149303B (zh) * | 2017-09-24 | 2023-02-21 | Lg电子株式会社 | 用于发送和接收反馈信息的方法及其车辆 |
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