WO2017010751A1 - 무선 통신 시스템에서 단말의 하향링크 수신 방법 및 장치 - Google Patents
무선 통신 시스템에서 단말의 하향링크 수신 방법 및 장치 Download PDFInfo
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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
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0023—Interference mitigation or co-ordination
- H04J11/0066—Interference mitigation or co-ordination of narrowband interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0069—Cell search, i.e. determining cell identity [cell-ID]
- H04J11/0079—Acquisition of downlink reference signals, e.g. detection of cell-ID
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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
- H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
- H04L25/061—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset
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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
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/261—Details of reference signals
- H04L27/2613—Structure of the reference signals
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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
- H04L5/0058—Allocation criteria
- H04L5/0064—Rate requirement of the data, e.g. scalable bandwidth, data priority
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/70—Services for machine-to-machine communication [M2M] or machine type communication [MTC]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
- H04B1/30—Circuits for homodyne or synchrodyne receivers
- H04B2001/305—Circuits for homodyne or synchrodyne receivers using dc offset compensation techniques
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J2211/00—Orthogonal indexing scheme relating to orthogonal multiplex systems
- H04J2211/003—Orthogonal indexing scheme relating to orthogonal multiplex systems within particular systems or standards
- H04J2211/005—Long term evolution [LTE]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/20—Modulator circuits; Transmitter circuits
- H04L27/2032—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner
- H04L27/2053—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner using more than one carrier, e.g. carriers with different phases
- H04L27/206—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner using more than one carrier, e.g. carriers with different phases using a pair of orthogonal carriers, e.g. quadrature carriers
- H04L27/2067—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner using more than one carrier, e.g. carriers with different phases using a pair of orthogonal carriers, e.g. quadrature carriers with more than two phase states
- H04L27/2089—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner using more than one carrier, e.g. carriers with different phases using a pair of orthogonal carriers, e.g. quadrature carriers with more than two phase states with unbalanced quadrature channels
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
- H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
- H04L27/3863—Compensation for quadrature error in the received signal
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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
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0014—Three-dimensional division
- H04L5/0023—Time-frequency-space
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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
Definitions
- the present invention relates to a method and apparatus for downlink reception of a terminal in a wireless communication system.
- the present invention also relates to a method and apparatus for downlink reception of a terminal for a low cost mechanical terminal in a wireless communication system.
- a 5G communication system or a pre-5G communication system is called a system after a 4G network (Beyond 4G Network) or a system after an LTE system (Post LTE).
- 5G communication systems are being considered for implementation in the ultra-high frequency (mmWave) band (eg, such as the 60 Gigabit (60 GHz) band).
- FD-MIMO massive array multiple input / output
- FD-MIMO massive array multiple input / output
- FD-MIMO massive array multiple input / output
- FD-MIMO massive array multiple input / output
- FD-MIMO massive array multiple input / output
- Array antenna, analog beam-forming, and large scale antenna techniques are discussed.
- 5G communication systems have advanced small cells, advanced small cells, cloud radio access network (cloud RAN), ultra-dense network (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation
- cloud RAN cloud radio access network
- D2D Device to Device communication
- D2D Device to Device communication
- CoMP Coordinated Multi-Points
- Hybrid FSK and QAM Modulation FQAM
- SWSC Slide Window Superposition Coding
- ACM Advanced Coding Modulation
- FBMC Fan Bank Multi Carrier
- NOMA non orthogonal multiple access
- SCMA sparse code multiple access
- IoT Internet of Things
- IoE Internet of Everything
- M2M machine to machine
- MTC Machine Type Communication
- IT intelligent Internet technology services can be provided that collect and analyze data generated from connected objects to create new value in human life.
- IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliances, advanced medical services, etc. through convergence and complex of existing information technology (IT) technology and various industries. It can be applied to.
- the wireless communication system has moved away from providing voice-oriented services in the early days, and high speed packet access (HSPA) of 3GPP, long term evolution (LTE) or evolved universal terrestrial radio access (E-UTRA), and high rate packet (HRPD) of 3GPP2.
- HSPA high speed packet access
- LTE long term evolution
- E-UTRA evolved universal terrestrial radio access
- HRPD high rate packet
- It is evolving into a broadband wireless communication system that provides high-speed, high-quality packet data services, such as communication standards such as Data, UMB (Ultra Mobile Broadband), and IEEE 802.16e.
- an LTE system adopts an orthogonal frequency division multiple access (OFDMA) scheme in downlink, and a single carrier frequency division multiple access (SC-FDMA) scheme in uplink. It is adopted.
- OFDMA orthogonal frequency division multiple access
- SC-FDMA single carrier frequency division multiple access
- data or control information of each user is classified by assigning and operating such that time-frequency resources for carrying data or control information for each user do not overlap each other, that is, orthogonality is established. do.
- the LTE system employs a hybrid automatic repeat request (HARQ) scheme in which the data is retransmitted in the physical layer when a decoding failure occurs in the initial transmission.
- HARQ hybrid automatic repeat request
- the receiver when the receiver does not correctly decode the data, the receiver transmits NACK (Negative Acknowledgement) indicating the decoding failure to the transmitter so that the transmitter can retransmit the corresponding data in the physical layer.
- NACK Negative Acknowledgement
- the receiver combines the data retransmitted by the transmitter with the previously decoded data to improve the data reception performance.
- the transmitter may transmit an acknowledgment (ACK) indicating the decoding success to the transmitter so that the transmitter may transmit new data.
- ACK acknowledgment
- the LTE system adopts a method of allocating resources to terminals according to channel conditions in order to improve downlink reception performance.
- the base station transmits a channel state information reference signal (CSI-RS) in downlink to allocate resources according to the channel state of the terminal.
- the terminal measures channel quality information (CQI) based on the CSI-RS and transmits it to the base station.
- the base station may allocate an optimal frequency resource to the terminal based on the CQI.
- An object of the present invention is to provide a method and apparatus for receiving a downlink of a terminal in a wireless communication system.
- the present invention also relates to a method and apparatus for downlink reception of a terminal for a low cost mechanical terminal in a wireless communication system.
- a narrowband DC (direct carrier) of one subcarrier among narrow band frequency resources allocated to the terminal is allocated. current) setting to a subcarrier, receiving a signal for the narrowband frequency resource from a base station, and decoding the received signal based on the set narrowband DC subcarrier.
- a transceiver for transmitting and receiving signals and a narrow band frequency allocated to the terminal Set a subcarrier of one of the resources to a narrowband direct current (DC) subcarrier, receive a signal for the narrowband frequency resource from a base station, and decode the received signal based on the set narrowband DC subcarrier
- a terminal including a controlling unit may be provided.
- a method and apparatus for downlink reception of a terminal in a wireless communication system may be provided.
- a method and apparatus for downlink reception of a terminal for a low-cost mechanical terminal in a wireless communication system may be provided.
- the downlink reception bandwidth of the terminal in order to realize low cost and low complexity of a terminal (for example, a low-cost MTC terminal), the downlink reception bandwidth of the terminal has a narrow bandwidth regardless of the system transmission bandwidth of the base station.
- a method for receiving a downlink signal of a terminal for minimizing the influence of a direct current (DC) offset due to an incomplete radio frequency (RF) characteristic of a low-cost MTC terminal may be provided.
- the low-cost MTC terminal receives a D.C. Minimizing the influence of the offset and at the same time does not use a subcarrier for transmitting the reference signal in the narrow band for downlink reception, channel estimation and channel equalization is impossible in the subcarrier, so The case where the reception performance is degraded can be prevented.
- FIG. 1 is a diagram illustrating a structure of a time-frequency domain, which is a radio resource region in which data or a control channel is transmitted in downlink in an LTE system according to an embodiment of the present invention.
- FIG. 2 is a diagram illustrating mapping of OFDMA subcarriers for data, control channel and signal transmission within a downlink system transmission bandwidth to generate a downlink OFDMA signal in an LTE or LTE-A system according to an embodiment of the present invention. to be.
- FIG. 3 is a block diagram of a resource block and a system D.C. in a system transmission bandwidth when a downlink system transmission bandwidth of an LTE or LTE-A system is 1.4 MHz, 10 MHz, or 20 MHz according to an embodiment of the present invention. It is a figure which shows the relationship of a subcarrier.
- FIG. 4 is a view illustrating a resource block and a system D.C. in a system transmission bandwidth when a downlink system transmission bandwidth of an LTE or LTE-A system is 3 MHz, 5 MHz, or 15 MHz according to an embodiment of the present invention. It is a figure which shows the relationship with a subcarrier.
- FIG. 5 is a diagram illustrating a narrowband structure for communication of a low-cost MTC terminal within a downlink system transmission bandwidth of an LTE or LTE-A system according to an embodiment of the present invention.
- FIG. 6 is a diagram illustrating a case in which a low-cost MTC terminal uses CRS for downlink signal demodulation in a first embodiment of the present invention. Narrowband D.C. to prevent subcarriers from matching It is a figure which shows the method of selecting a subcarrier.
- FIG. 7 illustrates a DMRS structure and narrowband D.C. for M-PDCCH in an LTE or LTE-A system according to a second embodiment of the present invention. It is a figure which shows the method of selecting a subcarrier.
- FIG. 8 shows a narrowband D.C. in a third embodiment of the present invention. It is a figure which shows the method of selecting a subcarrier.
- FIG. 9 is a diagram illustrating a receiving apparatus of a low-cost MTC terminal according to an exemplary embodiment of the present invention.
- FIG. 10 is a block diagram illustrating a detailed block constituting the RF converter 902 among blocks constituting a receiving device of a low-cost MTC terminal according to an exemplary embodiment of the present invention.
- FIG. 11 is a block diagram illustrating a detailed block constituting an OFDM receiver 903 among blocks constituting a receiving apparatus of a low-cost MTC terminal according to an embodiment of the present invention.
- the base station is a subject performing resource allocation of the terminal, and may be at least one of an eNode B, a Node B, a base station (BS), a wireless access unit, a base station controller, or a node on a network.
- the terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing a communication function.
- DL downlink
- UL uplink of a signal transmitted from a terminal to a base station.
- An embodiment of the present invention is a low-cost mechanical communication terminal (low-cost MTC terminal) limited to narrowband communication with the base station for low cost and low complexity in LTE and LTE-Advanced (LTE-A) system
- the low-cost mechanical communication terminal is composed of an RF module and a baseband module that can transmit and receive only in a narrow band at all times regardless of the system transmission bandwidth of the LTE system, thereby reducing the complexity and cost of the terminal.
- the narrowband transceiver terminal performs transmission and reception by moving to a narrowband set by a base station or a narrowband according to a rule or a pattern among a plurality of narrowbands existing within a system transmission bandwidth.
- the terminal receiving the downlink is D.C.
- the base station In order to minimize the effect of the offset and to reduce the complexity of the terminal, the base station is a D.C. No signal is sent to the subcarrier.
- D.C. in narrowband for inexpensive mechanical communication terminals. Subcarriers corresponding to subcarriers should be used as subcarriers for data and reference signals. Therefore, the low cost mechanical communication terminal is D.C. If the offset is significant, the subcarrier corresponding to the narrow band D.C. shall not be used to minimize the effects of the D.C offset.
- An embodiment of the present invention provides a D.C.
- the present invention proposes a method and apparatus for receiving a terminal capable of receiving a base station downlink signal while minimizing an influence of an offset.
- a narrowband reception bandwidth used by a terminal for example, a low-cost MTC terminal for receiving a downlink signal is smaller than a system transmission bandwidth used by a base station for transmission of a downlink signal, thereby transmitting the system.
- DC if there are multiple narrowbands within the bandwidth
- D.C A method of selecting a subcarrier and a method and apparatus for receiving control information and data using the same are provided.
- an embodiment of the present invention provides a method and apparatus for receiving a terminal for minimizing the influence on data and reference signal reception when a low-cost MTC terminal receives a narrowband downlink signal.
- the low-cost MTC terminal is a D.C.
- D.C To minimize performance degradation due to offsets, D.C.
- a method and apparatus for changing a center frequency of a low-cost MTC terminal to select a subcarrier are provided.
- FIG. 1 is a diagram illustrating a structure of a time-frequency domain, which is a radio resource region in which the data or control channel is transmitted in downlink in an LTE system.
- the horizontal axis represents the time domain and the vertical axis represents the frequency domain.
- the minimum transmission unit in the time domain is an OFDMA symbol, in which Nsymb (102) OFDMA symbols are gathered to form one slot 106, and two slots are gathered to constitute one subframe 105.
- the length of the slot is 0.5ms and the length of the subframe is 1.0ms.
- the radio frame 114 is a time domain unit consisting of 10 subframes.
- the minimum transmission unit in the frequency domain is a subcarrier, and the bandwidth of the entire downlink system transmission bandwidth is composed of a total of N BW 104 subcarriers.
- the basic unit of resource in the time-frequency domain may be represented by an OFDMA symbol index and a subcarrier index as a resource element (RE).
- the resource block 108 (Resource Block; RB or Physical Resource Block; PRB) is N symb (102) consecutive OFDMA symbols in the time domain and in the frequency domain. It is defined as (110) consecutive subcarriers. Thus, one RB 108 It consists of two REs (112).
- the minimum transmission unit of data is the above RB unit.
- the data rate increases in proportion to the number of RBs scheduled to the UE.
- LTE system six transmission bandwidths are defined and operated.
- the downlink transmission bandwidth and the uplink transmission bandwidth may be different.
- the channel bandwidth represents an RF bandwidth corresponding to the system transmission bandwidth.
- Table 1 shows the correspondence between the system transmission bandwidth and the channel bandwidth defined in the LTE system. For example, an LTE system with a 10 MHz channel bandwidth consists of 50 RBs of system transmission bandwidth.
- Quadrature Phase Shift Keying QPSK
- Quadrature Amplitude Modulation (16QAM) Quadrature Amplitude Modulation
- 64QAM Quadrature Amplitude Modulation
- each modulation order (Qm) corresponds to 2, 4, and 6. 2 bits per symbol for QPSK modulation, 4 bits per symbol for 16QAM modulation, and 6 bits per symbol for 64QAM modulation.
- low-cost / low-complexity UE may be supported through some function limitations of the terminal.
- Low-cost terminals are expected to be suitable for machine-type communication (MTC) or machine-to-machine (M2M) services, which are primarily aimed at remote meter reading, security, and logistics.
- MTC machine-type communication
- M2M machine-to-machine
- low-cost MTC UE is expected as a means to realize a cellular-based Internet of Things (IoT).
- the low-cost MTC terminal For the low cost and low complexity required by the low-cost MTC UE, by limiting the receiving antenna of the terminal to one, the cost of the RF element of the terminal is reduced or the transport block size that the low-cost MTC terminal can process It is possible to reduce the data reception buffer cost of the terminal by defining an upper limit.
- the general LTE terminal has a wideband signal transmission / reception function for a minimum 20 MHz band regardless of the bandwidth of the system transmission band, whereas the low-cost MTC terminal limits the maximum bandwidth for transmission and reception to less than 20 MHz, thereby providing additional low cost and Low complexity can be realized. For example, in an LTE system having a 20 MHz channel bandwidth, an operation of a low-cost MTC terminal supporting only a 1.4 MHz channel bandwidth may be defined.
- the low-cost MTC terminal having a narrowband smaller than the bandwidth of the system transmission band may include a plurality of defined channels within the system transmission bandwidth.
- the base station may communicate with the base station in one of the narrow bands.
- One narrowband for a low-cost MTC terminal is composed of six consecutive RBs, and a plurality of narrowbands are defined so as not to overlap each other within a system transmission bandwidth used by one base station.
- the low-cost MTC terminal transmits and receives a signal in a narrow band set by the base station to the terminal within the system transmission bandwidth, or transmits and receives a signal in a specific narrow band at a specific time according to a pattern determined for narrow band frequency hopping. can do.
- a subcarrier located in the middle of a downlink system transmission bandwidth does not map a signal.
- This subcarrier is referred to as D.C. Subcarrier (Direct Current subcarrier: D.C. subcarrier), and in the present invention, the system D.C. It is called a subcarrier.
- DC subcarriers have more noise than other subcarriers within the system transmission bandwidth due to imperfect characteristics of terminal radio frequency (eg, direct current offset (DC offset) and local oscillator leakage (LO leakage).
- the probability of data error is greater than that of other subcarriers.
- the base station does not transmit data to the system DC subcarrier located in the middle of the system transmission bandwidth.
- the base station transmits the system transmission bandwidth for downlink transmission and the system transmission bandwidth assumed by the terminal for downlink reception is the same. Therefore, the terminal should be set equal to the downlink reception bandwidth used in the RF and the baseband of the terminal in accordance with the downlink transmission bandwidth used in the base station (RF) and baseband (baseband). For the above reason, the system D.C. corresponding to D.C. in the downlink system transmission bandwidth.
- the subcarrier is the same at the terminal and the base station.
- the transmission bandwidth of the narrowband for receiving the downlink signal by the low-cost MTC terminal is different from the system transmission bandwidth for the downlink signal transmission by the base station.
- the low-cost MTC terminal always has a narrow bandwidth reception bandwidth of 1.4 MHz separately from the system transmission bandwidth. D.C. described above. Since the offset is more severe in the receiver of the terminal than the transmitter of the base station, D.C. per narrowband defined for the low-cost MTC terminal.
- data reception performance may be degraded and data error probability may increase.
- the narrowband for the low-cost MTC terminal uses the same resource block definition for the existing terminal, the subband that does not transmit data and reference signals like the system DC subcarrier in the resource block constituting the narrowband. It is difficult to assign a carrier. Therefore, in the embodiment of the present invention, when the base station transmits the downlink signal, the D.C. A signal is transmitted without considering the subcarrier, and the terminal (low-cost MTC terminal) is a D.C.
- FIG. 2 is a diagram illustrating mapping of OFDMA subcarriers for data, control channel, and signal transmission within a downlink system transmission bandwidth to generate a downlink OFDMA signal in a current LTE or LTE-A system.
- the frequency axis 201 for generating a downlink OFDMA signal includes an OFDM subcarrier spacing ( A plurality of subcarriers 202 are positioned in units of 203. A plurality of subcarriers 202 present within the system transmission bandwidth are sent to the subcarrier 202 for transmitting data, control information, reference signals, etc., and to the system DC subcarrier 204 for transmitting no signals. It is composed. As shown in FIG. 2, the system DC subcarrier 204 is located in the middle of the system transmission bandwidth. The system DC subcarrier 204 does not transmit any signal to prevent performance degradation due to DC offset as described above.
- Subcarrier 202 for transmitting data, control information and reference signals is all Subcarriers, the system DC subcarrier is located in the middle of the N BW subcarriers.
- Equation 1 is a formula representing a method for generating a downlink OFDMA time domain signal in an LTE or LTE-A system according to the subcarrier mapping shown in FIG. 2.
- a downlink time domain OFDMA signal corresponding to the antenna port p and the OFDM symbol l in the time domain may be generated as shown in Equation 1. here, ego, , to be. Also, Denotes a QPSK or QAM symbol corresponding to data transmitted from an antenna port p, a subcarrier k, and an OFDM symbol l, control information, or a reference signal. In addition, N CP , l is the number of samples of the cyclic prefix of the OFDM symbol l, Denotes a period of an OFDM symbol.
- Equation 1 for generating a downlink OFDMA time domain signal as shown in FIG. Can be seen that the system DC subcarrier is not used for data transmission.
- FIG. 3 is a diagram illustrating a resource block and a system D.C. within a system transmission bandwidth when a downlink system transmission bandwidth of an LTE or LTE-A system is 1.4 MHz, 10 MHz, or 20 MHz. It is a figure which shows the relationship of a subcarrier.
- the number of resource blocks 302 is even in the system transmission bandwidth. In other words, Is even.
- the resource block 302 is located on both sides of the system DC subcarrier 301.
- the system DC subcarrier 301 is located in the middle of the system transmission bandwidth.
- the system DC subcarrier 301 is not included in any resource block 302 located within the system transmission bandwidth. Since the base station uses a resource block 302 as a basic unit for transmitting data to the existing terminal and the low-cost MTC terminal in the downlink, as shown in FIG. It is always transmitted to the terminal regardless of the DC subcarrier.
- FIG. 4 is a diagram illustrating a resource block and a system D.C. within a system transmission bandwidth when a downlink system transmission bandwidth of an LTE or LTE-A system is 3 MHz, 5 MHz, or 15 MHz. It is a figure which shows the relationship with a subcarrier.
- one resource block 402 is positioned to consist of six subcarriers on both sides with the system DC subcarrier 401 in the middle, and the remaining resource block 403 is a resource block, 402) on both sides
- the subcarrier 401 is located in the middle of the resource block 402, but is not included in the resource block 402 and is recognized as a separate subcarrier.
- the resource block 402 located in the middle of the system transmission bandwidth is composed of 13 OFDM subcarriers differently from other resource blocks 403, but the other resource block 403 System DC located in the center of the resource block (403) using only 12 subcarriers for data and control information transmission
- the subcarrier 401 is not used. Since the base station uses resource blocks 402 and 403 as basic units to transmit data to the existing terminal and the low-cost MTC terminal in downlink, as shown in FIG. 4, data, control information, and reference signals are shown. Dc system It is always transmitted to the terminal regardless of the subcarrier.
- the low-cost MTC terminal performs transmission and reception with a base station in a narrow band smaller than the bandwidth of the system transmission band for low cost and low complexity. That is, the low-cost MTC terminal performs communication only in a narrow band smaller than the system transmission bandwidth of the base station.
- a low-cost MTC terminal has a narrowband transmission and reception capability of 1.4 MHz, which is the smallest system transmission bandwidth supported by LTE and LTE-A, and always communicates with a base station only at 1.4 MHz.
- the base station may have a plurality of narrowbands in the system transmission bandwidth, and may be configured to communicate with the low-cost MTC terminal in a specific narrowband. Also, the base station may set the low-cost MTC terminal to communicate in a specific narrowband at a specific time according to a specific hopping pattern.
- a narrowband for a low-cost MTC terminal is composed of six consecutive resource blocks, and a plurality of narrowbands are defined so as not to overlap each other within a system transmission bandwidth used by one base station.
- a resource block for a low-cost MTC terminal since a resource block for a low-cost MTC terminal must be aligned with a resource block used by an existing terminal within a system transmission bandwidth, a resource block for a low-cost MTC terminal. (resource block) is the same as the resource block (resource block) of the existing terminal.
- the base station does not use data transmission in narrowband. Difficult to place subcarrier Therefore, the low-cost MTC terminal is caused by D.C. If the influence of the offset is large, the terminal appropriately D.C.
- a subcarrier must be set to puncturing a signal transmitted on the corresponding subcarrier. That is, the terminal is a system D.C. It is required to set a D.C subcarrier in a narrow band different from the subcarrier to process a signal transmitted on the corresponding subcarrier.
- FIG. 5 is a diagram illustrating a narrowband structure for communication of a low-cost MTC terminal within a downlink system transmission bandwidth of an LTE or LTE-A system.
- a plurality of narrowbands 501 for low-cost MTC terminals exist within a system transmission bandwidth.
- the narrow band is a 1.4 MHz band.
- Each narrowband 501 is composed of six consecutive resource blocks 502, as described above, and resource blocks 502 do not overlap each other.
- any narrowband 501 is defined by the system D.C.
- the system D.C Although illustrated as an example of not overlapping with the subcarrier 507, embodiments of the present invention are not limited thereto, and the system D.C. It is also possible to include the subcarrier 507. However, even in this case, the system block D.C. Subcarrier 507 is not included.
- Each narrowband 501 may be defined in succession from any one end of the system transmission bandwidth, or may be defined in succession from both ends. Alternatively, narrowband 501 may be defined continuously from the middle of the system transmission bandwidth to both ends. However, it is possible to explain what the present invention proposes, regardless of how narrowband 501 is defined within the system transmission bandwidth.
- the low-cost MTC terminal may receive a downlink signal from the base station in a specific narrowband 501 according to the configuration of the base station or according to a predetermined rule.
- each resource block 502 constituting the narrow band 501 is a cell transmitted for channel estimation and equalization in addition to the resource elements RE and 508 for data and control information transmission. It consists of a Cell-specific reference signal (CRS) 509 and a null subcarrier 510 for CRS transmitted on a different antenna port.
- CRS Cell-specific reference signal
- DMRS demodulation reference signal
- the subcarrier may be set to the 12th subcarrier 504 of the RB # 2 503 or the first subcarrier 506 of the RB # 3 505 corresponding to the middle of 6 resource blocks.
- the terminal is D.C. If the offset is large, the signal received in the subcarrier may not be used for downlink signal demodulation. However, the low-cost MTC terminal sets the first subcarrier 506 of the RB # 3 505 as a narrowband DC subcarrier for receiving a downlink signal, and within a subframe corresponding to the corresponding subcarrier 506. Consider not receiving data and CRS in all REs.
- the UE punctures the data and the CRS transmitted in the corresponding subcarrier.
- the downlink reception performance is less affected by using an Forward Error Correction (FEC) code.
- FEC Forward Error Correction
- the UE punctures the CRS channel estimation performance may be degraded because channel estimation is impossible at the corresponding frequency, which causes degradation of data reception performance of the low-cost MTC terminal. Accordingly, a narrowband D.C. subband suitable for receiving a downlink signal in any narrowband by a low-cost MTC terminal. Criteria for selecting subcarriers are needed.
- the problem with the collision with the subcarrier may occur not only in the CRS but also when the corresponding UE uses a downlink demodulation reference signal (DMRS) for channel estimation and equalization.
- the downlink DMRS performs channel estimation and equalization when transmitting an MTC-Physical downlink control channel (MTC-PDCCH) and an MTC-PDSCH (MTC-Physical downlink shared channel) for transmitting control information of a low-cost MTC terminal. May be transmitted to the same terminal.
- MTC-PDCCH is a physical channel for transmitting control information to the low-cost MTC terminal
- MTC-PDSCH is a physical channel for transmitting data to the low-cost MTC terminal.
- a low-cost MTC terminal receives a downlink signal in a specific narrow band, and the terminal transmits the MTC-PDCCH or MTC-PDSCH.
- the terminal proposes to select a subcarrier corresponding to the DC according to the cell number (Cell ID) of the base station.
- the UE may select or set a subcarrier to which the CRS is not mapped as a subcarrier corresponding to D.C.
- the subcarrier k and the OFDM symbol index l of the RE through which the CRS is transmitted in the subframe may be determined through Equation 2.
- Is the slot index Is the number of resource blocks according to the downlink system transmission bandwidth
- Is the number of resource blocks in the maximum downlink system transmission bandwidth used in LTE Denotes the number of OFDM symbols in the downlink subframe, respectively.
- Equation 2 Denotes the cell number of the cell to which the terminal is currently connected. According to Equation 2, it can be seen that the location of the RE for transmitting the CRS depends on the cell number (Cell ID).
- the terminal is narrowband D.C. according to the cell number of the base station.
- narrowband D.C narrowband D.C.
- the problem of not receiving the CRS by the subcarrier can be solved. That is, the CRS mapping position in the cell may be identified based on the cell number, and the UE may select a narrowband D.C. Can be selected by subcarrier. The UE selects a subcarrier in which the CRS is not mapped (or allocated) among the subcarriers closest to the center frequency of the narrowband allocated to the narrowband D.C. Can be set to a subcarrier.
- FIG. 6 is a diagram illustrating a case in which a low-cost MTC terminal uses CRS for downlink signal demodulation, according to a first embodiment of the present invention.
- Narrowband D.C. to prevent subcarriers from matching It is a figure which shows the method of selecting a subcarrier.
- the narrowband 601 through which the physical channel to be demodulated based on CRS is transmitted includes an RE 603 for data transmission and an RE 602 allocated for CRS transmitted by an arbitrary antenna port. And an RE that does not transmit a signal to avoid interference with the CRS transmitted by another antenna port.
- FIG. 6 a case in which four antenna ports are set will be described. However, even if the antenna ports are 1 or 2, the descriptions of the present invention can be applied without change.
- the low-cost MTC terminal is a narrowband D.C. N. corresponding to the narrowband to facilitate the RF and baseband implementation of the terminal. It is appropriate to set the subcarrier in the middle of the narrow band. However, in the embodiment of FIG. 6, the low-cost MTC terminal uses the narrowband D.C. C. according to the position of the subcarrier through which the CRS is transmitted to use the CRS for demodulation of the downlink signal according to the first embodiment of the present invention. It is proposed to set a subcarrier.
- the cell number estimated by the low-cost MTC terminal according to the first embodiment of the present invention is If 604 is satisfied, the terminal proposes to set the DC subcarrier in the corresponding narrow band to the 12th subcarrier 605 of RB # 2 to avoid collision with the CRS on the frequency. That is, the 12th subcarrier 605 of RB # 2 and the 12th subcarrier 605 of RB # 2 to which the CRS is not mapped are selected as the narrowband DC subcarriers.
- the cell number estimated by the low-cost MTC terminal is If 606 is satisfied, the UE proposes to set the DC subcarrier in the corresponding narrow band as the first subcarrier 607 of RB # 3 to avoid collision with the CRS on the frequency. That is, the 12th subcarrier 605 of RB # 2 and the 12th subcarrier 605 of RB # 2 to which the CRS is not mapped among the first subcarriers of RB # 3 are set as narrowband DC subcarriers.
- the cell number estimated by the low-cost MTC terminal is If 608 is satisfied, the CRS is not located in two subcarriers corresponding to the middle of the narrowband.
- the low-cost MTC terminal sets a narrowband DC subcarrier currently received by the terminal to any one of the 12th subcarrier 609 of RB # 2 or the 1st subcarrier 610 of RB # 3 in frequency. It is okay.
- the terminal When the low-cost MTC terminal configures a narrowband DC subcarrier according to the first embodiment of the present invention, the terminal does not use the QPSK / QAM symbol transmitted on the selected subcarrier for downlink signal demodulation, and instead the corresponding sub
- the UE demodulates the downlink signal using randomly generated QPSK / QAM symbols or random QPSK / QAM symbols for the carrier.
- a low-cost MTC terminal When the low-cost MTC terminal receives an MTC downlink control channel (MT-PDCCH) in an arbitrary narrow band for receiving downlink control information, the terminal receives a DMRS (DMRS) for M-PDCCH demodulation. Demodulation Reference Signal). Therefore, the terminal is D.C. Narrowband D.C. not used for downlink reception to minimize the impact of offsets If the subcarrier is the same as the subcarrier for DMRS transmission, channel estimation and equalization cannot be performed in the corresponding RE, resulting in deterioration in reception performance of the M-PDCCH.
- a low-cost MTC terminal proposes a method of minimizing performance degradation of the M-PDCCH in receiving an M-PDCCH.
- the M-PDCCH for the low-cost MTC terminal is based on an Enhanced Physical Downlink Control Channel (EPDCCH). Therefore, the DMRS of the M-PDCCH is the same as the DMRS used in the EPDCCH.
- the subcarrier k and the OFDM symbol index l of the RE through which the DMRS of the EPDCCH is transmitted may be determined through Equation 3.
- FIG. 7 illustrates a DMRS structure and narrowband D.C. for M-PDCCH in LTE or LTE-A system. It is a figure which shows a subcarrier.
- one resource block 701 includes an RE 702 for transmitting M-PDCCH control information, an RE 703 for transmitting CRS on an arbitrary antenna port, and a CRS transmitted on another antenna port. In order to minimize the interference, it is composed of an RE 704 which is not used for signal transmission and an RE 705 and 706 for DMRS transmission.
- the DMRS for RE and M-PDCCH demodulation is divided into an RE 705 for DMRS transmission corresponding to antenna ports 107 and 108 and an RE 706 for DMRS transmission corresponding to antenna ports 109 and 110 according to Equation 3 below.
- the M-PDCCH uses precoder cycling to improve coverage, so the low-cost MTC terminal uses an antenna port in a resource block 701 in which the M-PDCCH is transmitted for M-PDCCH demodulation. All DMRSs corresponding to 107, 108, 109, and 110 must always be received. Accordingly, when the M-PDCCH for the low-cost MTC terminal is located in a resource block corresponding to the middle of the narrow band (for example, RB # 2 or RB # 3 in FIG.
- the terminal is M-
- the low-cost MTC terminal uses a narrowband DC in consideration of the DMRS.
- the subcarrier must be selected.
- the UE selects a narrowband D.C. subcarrier in which the DMRS is not mapped (or assigned) among the subcarriers closest to the center frequency of the narrowband allocated to the terminal. Can be set to a subcarrier.
- the low-cost MTC terminal is a D.C.
- D.C In order to minimize performance degradation of M-PDCCH due to offset, D.C. It is proposed to select a subcarrier as a subcarrier for which DMRS is not transmitted.
- the M-PDCCH for the low-cost MTC terminal is located in a resource block corresponding to the middle of a narrow band (for example, RB # 2 or RB # 3 in FIG. 7), the terminal uses a DMRS channel For estimation, the 11th subcarrier 710 and 12th subcarrier 709 of RB # 2 and the 1st subcarrier 708 and 2nd subcarrier 707 of RB # 3 should always be received.
- the low-cost MTC terminal selects a subcarrier corresponding to a narrowband DC as the 10th subcarrier 711 of RB # 2 or the 3rd subcarrier 712 of RB # 3 for M-PDCCH reception. Suggest.
- the low-cost MTC terminal may select a subcarrier corresponding to a narrowband DC from any one of a tenth subcarrier 711 of RB # 2 or a third subcarrier 712 of RB # 3.
- another subcarrier may be selected. That is, when the CRS is transmitted in the 10th subcarrier 711 of RB # 2, the low-cost MTC terminal selects the 3rd subcarrier 712 of the RB # 3 in the narrowband D.C. If the CRS is transmitted in the third subcarrier 712 of RB # 3, the 10th subcarrier 711 of RB # 2 is selected as the narrowband D.C. Can be selected by subcarrier.
- the terminal selects a narrowband D.C. subcarrier in which the CRS and the DMRS are not mapped (or assigned) among the subcarriers closest to the center frequency of the narrowband allocated to the terminal. Can be set to a subcarrier.
- the low-cost MTC terminal is a narrowband D.C.
- the present invention proposes a low-cost MTC terminal reception method for minimizing M-PDCCH reception performance degradation when one subcarrier is selected among subcarriers through which DMRS for M-PDCCH demodulation is transmitted.
- the low-cost MTC terminal uses the narrowband D.C. N. subcarrier 709 of RB # 2 or the first subcarrier 708 of RB # 3 as a subcarrier corresponding to the middle of the narrowband. In case of selecting a subcarrier, the terminal selects a narrowband D.C.
- the low-cost MTC terminal is a narrowband D.C. It is proposed that the channel estimate value in the DMRS corresponding to the subcarrier is replaced with the channel estimate value in another DMRS.
- the channel estimation value used instead is narrowband D.C.
- the same antenna port as the DMRS corresponding to the subcarrier is used and the value estimated from the nearest DMRS is used.
- the low-cost MTC terminal is a narrowband D.C.
- the terminal cannot receive DMRSs corresponding to antenna ports 107 and 108 in the corresponding subcarrier.
- the channel estimates for the antenna ports 107 and 108 in the subcarrier 709 may be replaced from the channel estimates for the antenna ports 107 and 108 in the subcarrier 707.
- the low-cost MTC terminal selects the first subcarrier 708 of RB # 3 in the narrowband D.C.
- the terminal cannot receive DMRSs corresponding to antenna ports 109 and 110 in the corresponding subcarrier.
- the channel estimates for antenna ports 109 and 110 in the corresponding subcarrier 708 may be replaced by the channel estimates for antenna ports 109 and 110 in the subcarrier 710.
- the position of the RE where the DMRS is transmitted may be changed for each antenna port according to a transmission mode set by the base station for each terminal.
- the MTC-PDSCH should be received in the transmission mode set according to the configuration of the base station, and the DMRS should be received and channel estimation performed at the location of the RE determined according to the transmission mode. Therefore, the low-cost MTC terminal receiving the MTC-PDSCH is also D.C.
- the subcarrier to which DMRSs are transmitted is narrowband D.C. Narrowband D.C. to match subcarriers It is proposed to change the subcarrier.
- the low-cost MTC terminal is a narrowband D.C.
- the terminal does not use the QPSK / QAM symbol transmitted on the selected subcarrier for M-PDCCH demodulation, but instead the QPSK / QAM symbol generated randomly by the terminal for the corresponding subcarrier or random. Demodulate the downlink signal using the QPSK / QAM symbol.
- FIG. 8 shows a narrowband D.C. in a third embodiment of the present invention. It is a figure which shows the method of selecting a subcarrier.
- the base station In the base station to transmit the MTC-PDCCH and MTC-PDSCH to the low-cost MTC terminal, depending on the TBS (Transport block size) to be transmitted or the coverage enhancement value required for the terminal to receive the corresponding downlink signal without error,
- the entire resource block constituting the band may be used or only some resource blocks constituting the narrow band may be used. If the base station uses only some of the resource blocks 801 constituting the narrow band as shown in Figure 8 to transmit the downlink signal to the corresponding low-cost MTC terminal, the remaining resource block 803 is another low-cost MTC It can be used to transmit a downlink signal to a terminal or a general LTE terminal.
- the base station uses the entire resource block constituting the narrow band in transmitting the MTC-PDCCH and the MTC-PDSCH to the low-cost MTC terminal, D.C. Narrowband D.C. according to the first or second embodiment described above in order to minimize the effect of the offset.
- the subcarrier must be selected.
- the low-cost MTC terminal is a D.C.
- the narrowband D.C It is proposed to select a subcarrier.
- the base station transmits the MTC-PDCCH and the MTC-PDSCH to the low-cost MTC UEs.
- Some of the resource blocks constituting the narrow band (for example, RB # k + 2, RB # k + 3, If only RB # k + 4 is configured as a combination of all or some of the resource blocks) 801, the low-cost MTC terminal is a narrow-band DC out of the subcarriers of the unallocated resource block 803 Restrict setting a subcarrier.
- the narrowband DC subcarrier is effective to set the subcarrier adjacent to the resource block used for MTC-PDCCH and MTC-PDSCH received by the low-cost MTC terminal as the narrowband DC subcarrier 805, the present invention is effective. Does not limit this, and depending on the implementation, DC to any subcarrier of the resource block 803
- the subcarrier may be set. Since the base station presets the narrowband for receiving the MTC-PDCCH and the location of the resource block used in the narrowband to the terminal in advance, the terminal can receive the D.C. Subcarrier setting is possible. In addition, since the UE can know the location of the narrowband for MTC-PDSCH reception and the location of the resource block used in the narrowband by using downlink control information (DCI) transmitted by the base station, D.C. Subcarrier setting is possible.
- DCI downlink control information
- a low-cost MTC terminal is a subcarrier in a resource block belonging to another narrow band instead of a narrow band in which a base station transmits an MTC-PDCCH and an MTC-PDSCH to the terminal.
- Narrowband DC The method of selecting subcarriers. In this case, the method may be used regardless of whether the base station uses the entire resource block configuring the narrow band in transmitting the MTC-PDCCH and the MTC-PDSCH to the low-cost MTC terminal.
- the low-cost MTC terminal is narrowband #k.
- the subcarrier can be set.
- the terminal In order to realize another method of configuring the third embodiment of the present invention, the terminal always needs a wider RF and baseband bandwidth than the narrow bandwidth transmission bandwidth.
- the UE may narrow the data symbols as well as the reference signal in the allocated resource block for receiving the downlink signal. There is an advantage that all can be received without loss by the subcarrier.
- FIG. 9 is a diagram illustrating a receiving apparatus of a low-cost MTC terminal according to an exemplary embodiment of the present invention.
- a reception apparatus of a low-cost MTC terminal includes an antenna 901, an RF converter 902, an OFDM receiver 903, a decoder 904, and a controller 905 capable of narrowband reception. It is composed.
- the configuration of the terminal is not limited to this.
- the terminal may be configured as a transceiver for transmitting and receiving signals and a controller for controlling the overall operation of the terminal.
- the antenna 901 of the low-cost MTC terminal converts a downlink passband signal transmitted from the base station into an electrical signal and transmits the converted signal to the RF converter 902.
- the RF converter 902 down-converts the signal transmitted from the antenna 901 to the baseband and filters the narrowband that the terminal should receive.
- a low-cost MTC terminal is determined according to the first, second, and third embodiments of the present invention. Narrowband DC According to the subcarrier, the center frequency used by the UE for downconversion is changed. This will be described in detail with reference to FIG. 10.
- the downlink signal converted to the baseband by the RF converter 902 is transferred to the OFDM receiver 903 to perform OFDM demodulation.
- the OFDM receiver 903 includes a cyclic prefix remover, a Fast Fourier Transmform (FFT) processor, a remapper, and the like, and converts an OFDM signal into a QPSK / QAM signal.
- FFT Fast Fourier Transmform
- the narrowband D.C. selected by the low-cost MTC terminal according to the first, second and third embodiments of the present invention.
- the UE does not use for demodulation.
- the UE may replace the subcarrier with a randomly generated QPSK / QAM symbol or a fixed specific QPSK / QAM symbol.
- the QPSK / QAM symbol generated in the OFDM receiver extracts a bit level signal transmitted from the base station from the QPSK / QAM symbol in the decoder 904 and between the base station transmitter and the terminal receiver according to the error correction code for the received bit.
- the error that may occur in the controller is corrected and transmitted to the controller 905.
- the controller 905 controls the operation of the terminal according to the type of information received from the base station, or serves to deliver the received information to the upper layer.
- the control unit of the terminal sets a subcarrier of one of narrowband frequency resources allocated to the terminal as a narrowband direct current (DC) subcarrier, and sets the narrowband from the base station. Receives a signal for a frequency resource, and may be controlled to decode the received signal based on the set narrowband DC subcarrier.
- the narrowband DC subcarrier may be one subcarrier selected from among subcarriers constituting a resource block included in the narrowband.
- control unit may control to select a subcarrier at a close distance from the center frequency of the narrowband among subcarriers other than the subcarrier to which the reference signal is mapped in the narrowband.
- the control unit based on the cell ID (cell ID), the narrowband DC to the subcarrier other than the subcarrier mapped to the cell-specific reference signal (CRS, cell-specific reference signal) It can be controlled to select by subcarrier.
- the controller may control to select a subcarrier except a subcarrier to which a demodulation reference signal (DMRS) is mapped as a narrowband DC subcarrier.
- the control unit may control to select the narrowband DC subcarrier in a band other than the partial frequency band allocated to the terminal among the narrowband frequency resources when a portion of the narrowband is allocated to the terminal. have.
- the control unit may further control the narrowband D.C. at a frequency resource allocated to a narrowband other than the narrowband. It may be controlled to select a subcarrier.
- At least one information of a reference signal or a data signal for the terminal may be transmitted through the narrowband DC subcarrier. That is, since the terminal does not set the narrow-band DC subcarrier arbitrarily set, the base station is a reference signal or data signal in a frequency resource corresponding to the narrow-band DC subcarrier irrespective of the narrow-band DC subcarrier set by the terminal Can be transmitted.
- the controller may control to downconvert the received signal to baseband based on the set narrowband DC subcarrier.
- the control unit does not use a modulation symbol corresponding to the narrowband DC subcarrier to demodulate the received signal, and uses any modulation symbol or a predetermined modulation symbol as a modulation symbol corresponding to the narrowband DC subcarrier. Can be controlled.
- the controller may control to remap to correct a fast fourier transform (FFT) output index of the received signal based on the narrowband DC subcarrier.
- FFT fast fourier transform
- FIG. 10 is a block diagram illustrating a detailed block constituting the RF converter 902 among blocks constituting a receiving device of a low-cost MTC terminal according to an embodiment of the present invention.
- the RF converter 902 included in the low-cost MTC terminal includes a filter 1001, a down converter 1002, a center frequency generator 1003, and an LNA 104.
- the filter 1001 constituting the RF converter 902 performs a function of passing only a desired band (generally wider than a narrow band) among signals transmitted through downlink.
- the signal filtered by the filter 1001 is transferred to the downconverter 1002 and downconverted from the passband to the baseband.
- the down converter 1002 receives a continuous wave (CW) signal corresponding to the center frequency from the center frequency generator 1003 to convert the passband downlink signal to the baseband.
- CW continuous wave
- the down-converter of the low-cost MTC terminal should be down-converted according to the center frequency corresponding to the narrow band for downlink reception by the current terminal, not the center frequency of the system transmission band.
- the low-cost MTC terminal is narrowband D.C. according to the first, second and third embodiments according to the present invention.
- the center frequency also changes depending on the subcarrier selection. Therefore, the center frequency generator 1003 of the low-cost MTC terminal according to the first, second and third embodiments of the present invention proposes to select the center frequency through Equation 4.
- Equation (4) Means frequencies corresponding to the middle of the narrowband that the low-cost MTC terminal should receive, Means a center frequency that the low-cost MTC terminal should use when the low-cost MTC terminal selects the narrow-band DC subcarrier according to the first, second and third embodiments.
- k is a value representing the distance from the narrowband middle to the selected narrowband DC subcarrier in the unit of subcarrier frequency space, and is included in the narrow block of the narrowband from the middle of the narrowband. K has a negative value when the band DC subcarrier is selected, and k has a positive value when the narrowband DC subcarrier included in the high index resource block is selected from the middle of the narrow band. .
- the 12th subcarrier 605 of RB # 2 is replaced with a narrowband D.C.
- k -1
- the first subcarrier 605 of RB # 3 is narrowed to D.C.
- the downlink signal downconverted by the downconverter 1002 is amplified to a size suitable for processing by an OFDM receiver in a low-noise amplifier (LNA) 1004 and is transmitted to an OFDM receiver.
- LNA low-noise amplifier
- FIG. 11 is a block diagram illustrating a detailed block constituting an OFDM receiver 903 among blocks constituting a receiving device of a low-cost MTC terminal according to an embodiment of the present invention.
- the OFDM receiver 903 included in the low-cost MTC terminal includes a cyclic prefix remover 1101, a serial / parallel converter 1102, an FFT processor 1103, a remapping unit 1104, and parallel / serial. It consists of a transducer 1105.
- the cyclic prefix remover 1101 constituting the OFDM receiver 903 is a block for removing the cyclic prefix transmitted before the OFDM symbol transmission in order to prevent performance degradation due to the multipath delay.
- the serial / parallel converter 1102 then stores the downlink baseband signal, which is serially input, in the memory as long as the OFDM symbol length and then delivers the downlink baseband signal to the FFT processor 1103 in parallel.
- the FFT processor performs the FFT according to the FFT size corresponding to the narrowband of the low-cost MTC terminal and then transfers the output QPSK / QAM symbol to the remapping unit 1104.
- the remapping unit 1104 is a narrowband D.C. terminal of the low-cost MTC terminal according to the first, second and third embodiments of the present invention. A block for correcting the change of the index of the FFT output according to the subcarrier selection.
- the remapping unit 1104 remaps the QPSK / QAM symbols transmitted from the FFT processor 1103 to the l-th subcarrier to the m-th subcarrier according to Equation 5.
- k is a narrow band D.C.
- a narrowband D.C. narrow-band value representing a distance to a subcarrier in subcarrier frequency space units and included in a resource block of a low index from the middle of the narrowband.
- k has a negative value
- the narrowband D.C subcarrier included in the resource block of the high index from the middle of the narrow band is selected, k has a positive value.
- the 12th subcarrier 605 of RB # 2 is replaced with a narrowband D.C.
- the first subcarrier 605 of RB # 3 is narrowed to D.C.
- the signal having been remapped by the remapping unit 1104 is input to the parallel / serial converter 1105 after channel estimation and channel equalization and transmitted to the decoder in series.
- FIG. 12 is a diagram illustrating an operation of a terminal according to an embodiment of the present invention.
- the UE may acquire a cell ID and / or narrowband information allocated to the UE.
- the cell number and narrowband information may be obtained through different processes.
- the UE may configure a narrowband D.C subcarrier.
- the subcarrier setting method may use at least one of the methods described in the first, second and third embodiments of the present invention.
- the subcarrier is the system D.C. of the base station communicating with the terminal. It may be a subcarrier different from the subcarrier.
- the narrowband D.C. As a subcarrier, one subcarrier (subcarrier string) of 12 subcarriers of one resource block among a plurality of resource blocks allocated to the terminal may be selected or set.
- the terminal receives a signal for the terminal from the base station.
- the UE may RF convert the received signal.
- the terminal may down-convert the signal received from the antenna to the baseband and filter the narrow band that the terminal should receive. In down-conversion, the terminal is the narrowband D.C.
- the frequency of the subcarrier can be used. For details of the RF conversion, refer to the description of FIGS. 9 and 10.
- the UE performs OFDM demodulation.
- the UE may perform CP removal, FFT, remapping, channel estimation, and equalization.
- the QPSK / QAM symbol corresponding to the sub-to-carrier is not used for demodulation of the terminal.
- the terminal may replace a randomly generated QPSK / QAM symbol or a fixed specific QPSK / QAM symbol with a symbol corresponding to the narrowband D.C subcarrier.
- FIGS. 9 and 11 For details of OFDM demodulation, see FIGS. 9 and 11.
- the UE may decode the QPSK / QAM symbol.
- the QPSK / QAM symbol generated in the OFDM receiver extracts a bit level signal transmitted from the base station from the QPSK / QAM symbol in the decoder and is generated between the base station transmitter and the terminal receiver according to the error correction code for the received bit.
- the error may be corrected and transmitted to the controller of the terminal.
- the controller may control the operation of the terminal based on the extracted signal or transmit the received information to an upper layer of the terminal.
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Abstract
Description
Claims (15)
- 협대역(narrow band) 통신을 이용하여 하향링크를 수신하는 단말에 있어서,신호를 송신 및 수신하는 송수신부; 및상기 단말에 할당된 협대역(narrow band) 주파수 자원 중 하나의 서브캐리어를 협대역 DC(direct current) 서브캐리어로 설정하고, 기지국으로부터 상기 협대역 주파수 자원에 대한 신호를 수신하며, 상기 설정된 협대역 DC 서브캐리어에 기반하여 상기 수신 신호를 디코딩하도록 제어하는 제어부를 포함하는 단말.
- 제1항에 있어서, 상기 협대역 DC 서브캐리어는 상기 협대역에 포함된 자원 블록(resource block)을 구성하는 서브캐리어 중 선택된 하나의 서브캐리어인 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 제어부는,상기 협대역에서 기준 신호가 매핑된 서브캐리어를 제외한 서브캐리어 중 상기 협대역의 중심 주파수로부터 가까운 거리에 있는 서브캐리어를 선택하도록 제어하는 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 제어부는,셀 식별정보(cell ID)에 기반하여 셀 특정 기준 신호(CRS, cell-specific reference signal)가 매핑된 서브캐리어를 제외한 서브캐리어를 협대역 DC 서브캐리어로 선택하도록 제어하는 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 제어부는,복조 기준 신호(DMRS, demodulation reference signal)가 매핑된 서브캐리어를 제외한 서브캐리어를 협대역 DC 서브캐리어로 선택하도록 제어하는 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 제어부는,상기 협대역 중 일부 주파수 대역이 상기 단말에 할당된 경우, 상기 협대역 주파수 자원 중 상기 단말에 할당된 일부 주파수 대역을 제외한 대역에서 상기 협대역 DC 서브캐리어를 선택하도록 제어하는 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 협대역 DC 서브캐리어를 통해 상기 단말에 대한 기준 신호 또는 데이터 신호 중 적어도 하나의 정보가 전송되는 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 제어부는,상기 설정된 협대역 DC 서브캐리어에 기반하여 상기 수신 신호를 기저대역으로 하향 변환하도록 제어하는 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 제어부는,상기 협대역 DC 서브캐리어에 대응하는 변조 심볼을 상기 수신 신호의 복조에 사용하지 않고, 임의의 변조 심볼 또는 기 설정된 변조 심볼을 상기 협대역 DC 서브캐리어에 대응하는 변조 심볼로 사용하도록 제어하는 것을 특징으로 하는 단말.
- 제1항에 있어서, 상기 제어부는,상기 협대역 DC 서브캐리어에 기반하여 상기 수신 신호의 FFT(fast fourier transform) 출력 인덱스를 보정하기 위해 재 매핑하도록 제어하는 것을 특징으로 하는 단말.
- 협대역(narrow band) 통신을 이용하는 단말의 하향링크 수신 방법에 있어서,상기 단말에 할당된 협대역(narrow band) 주파수 자원 중 하나의 서브캐리어를 협대역 DC(direct current) 서브캐리어로 설정하는 단계;기지국으로부터 상기 협대역 주파수 자원에 대한 신호를 수신하는 단계; 및상기 설정된 협대역 DC 서브캐리어에 기반하여 상기 수신 신호를 디코딩하는 단계를 포함하는 방법.
- 제11항에 있어서, 상기 협대역 DC 서브캐리어는 상기 협대역에 포함된 자원 블록(resource block)을 구성하는 서브캐리어 중 선택된 하나의 서브캐리어인 것을 특징으로 하는 방법.
- 제11항에 있어서, 상기 협대역 DC 서브캐리어를 설정하는 단계는,상기 협대역에서 기준 신호가 매핑된 서브캐리어를 제외한 서브캐리어 중 상기 협대역의 중심 주파수로부터 가까운 거리에 있는 서브캐리어를 선택하는 것을 특징으로 하는 방법.
- 제11항에 있어서, 상기 협대역 DC 서브캐리어를 설정하는 단계는,셀 식별정보(cell ID)에 기반하여 셀 특정 기준 신호(CRS, cell-specific reference signal)가 매핑된 서브캐리어를 제외한 서브캐리어를 협대역 DC 서브캐리어로 선택하는 것을 특징으로 하는 방법.
- 제11항에 있어서, 상기 협대역 DC 서브캐리어를 설정하는 단계는,복조 기준 신호(DMRS, demodulation reference signal)가 매핑된 서브캐리어를 제외한 서브캐리어를 협대역 DC 서브캐리어로 선택하는 것을 특징으로 하는 방법.
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US10469294B2 (en) | 2019-11-05 |
AU2016294269B2 (en) | 2020-02-27 |
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CN107852307A (zh) | 2018-03-27 |
KR20170009225A (ko) | 2017-01-25 |
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