WO2017142259A1 - Procédé de transmission de signal de synchronisation utilisant un livre de codes dans un système de communication sans fil - Google Patents

Procédé de transmission de signal de synchronisation utilisant un livre de codes dans un système de communication sans fil Download PDF

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Publication number
WO2017142259A1
WO2017142259A1 PCT/KR2017/001483 KR2017001483W WO2017142259A1 WO 2017142259 A1 WO2017142259 A1 WO 2017142259A1 KR 2017001483 W KR2017001483 W KR 2017001483W WO 2017142259 A1 WO2017142259 A1 WO 2017142259A1
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Prior art keywords
synchronization signal
synchronization
sequence
sss
base station
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PCT/KR2017/001483
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English (en)
Korean (ko)
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이길봄
김규석
안민기
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엘지전자 주식회사
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • 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
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2692—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver
    • 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
    • H04L27/26132—Structure of the reference signals using repetition
    • 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
    • H04L27/26136—Pilot sequence conveying additional information

Definitions

  • the following description relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting a synchronization signal in a WLAN system.
  • Ultra-high frequency wireless communication systems using millimeter wave are configured such that the center frequency operates at a few GHz to several tens of GHz. Due to the characteristics of the center frequency, path loss may be prominent in the shadow area in the mmWave communication system. Considering that the synchronization signal should be stably transmitted to all terminals located within the coverage of the base station, the mmWave communication system designs and transmits the synchronization signal in consideration of the potential deep-null phenomenon that may occur due to the characteristics of the ultra-high frequency band described above. Should be.
  • the present invention has been made to solve the above problems, an object of the present invention to improve the synchronization process between the base station and the terminal in a wireless communication system to improve the transmission efficiency of the synchronization signal.
  • a synchronization signal transmission method Generating a scrambling sequence to be applied to the SSS, generating an SSS to be transmitted for a sector using the scrambling sequence, and repeatedly transmitting a PSS and the SSS selected in the PSS sequence set over a plurality of time intervals.
  • a value corresponding to some information of the physical layer ID or the physical layer ID of the base station may be applied.
  • the SSS is allocated to a resource region adjacent to the resource region allocated to the PSS on a frequency axis, and the position of the resource region to which the SSS is allocated may be determined based on the synchronization parameter.
  • SSSs of two physically adjacent sectors may be allocated to adjacent resource regions in different directions on the frequency axis, respectively, to the resource region allocated to the PSS.
  • the synchronization parameter may be defined by a combination of any one PSS sequence selected from the PSS sequence set and one OCC corresponding to the number of times a synchronization signal is repeatedly transmitted.
  • SSSs transmitted to two physically adjacent sectors are applied with different OCCs, and an OCC applied to each SSS may be determined based on the synchronization prime.
  • the base station for solving the above technical problem includes a transmitter, a receiver, and a processor operating in connection with the transmitter and the receiver, the processor comprising: a PSS sequence set defined for the sector (sector) to which the synchronization signal is to be transmitted; Determining a synchronization parameter using an orthogonal cover code (OCC), generating a scrambling sequence to be applied to the SSS using the synchronization parameter, generating an SSS to be transmitted for a sector using the scrambling sequence, and a PSS selected from the PSS sequence set And SSS is repeatedly transmitted over a plurality of time intervals.
  • OCC orthogonal cover code
  • the synchronization process between the base station and the terminal in the wireless communication system is improved to enable efficient transmission and reception of the synchronization signal between the base station and the terminal.
  • 1 is a diagram illustrating a Doppler spectrum.
  • FIG. 2 is a diagram illustrating narrow beamforming according to the invention.
  • 3 is a diagram illustrating Doppler spectra when narrow beamforming is performed.
  • FIG. 4 is a diagram illustrating an example of a synchronization signal service zone of a base station.
  • 5 is an example of a frame structure proposed in a communication environment using mmWave.
  • OVSF Orthogonal Variable Spreading Factor
  • FIG. 7 is a diagram illustrating an example of an arrangement of terminals.
  • FIG. 8 is a diagram illustrating a synchronization signal transmission structure according to one embodiment.
  • FIG 9 illustrates a synchronization signal repeatedly transmitted according to an embodiment.
  • FIG. 10 illustrates a process of estimating sequence and timing by a terminal receiving a synchronization signal.
  • FIG. 11 illustrates another embodiment of a process in which a terminal synchronizes timing by using a synchronization signal.
  • FIG. 12 is a flowchart illustrating a synchronization signal transmission and reception method according to an embodiment.
  • FIG. 13 is a view illustrating another embodiment related to a synchronization signal transmission / reception method.
  • 14 to 17 are diagrams illustrating a synchronization signal transmission structure according to another embodiment.
  • FIGS. 14 to 17 are flowchart illustrating a synchronization signal transmission and reception method according to FIGS. 14 to 17.
  • 19 and 20 illustrate a structure of transmitting a synchronization signal and a beam scanning signal for explaining another proposed embodiment.
  • 21 to 23 illustrate a structure of transmitting a synchronization signal and a beam scanning signal according to a proposed embodiment.
  • 24 is a flowchart illustrating a synchronization process and a beam scanning process according to another embodiment of the present disclosure.
  • 25 is a diagram for explaining a beam extension technique.
  • AAS active antenna system
  • 27 to 31 are diagrams illustrating a synchronization process and a beam scanning process using a sub-arrangement concept according to an exemplary embodiment.
  • 32 to 34 are diagrams illustrating a synchronization process and a beam scanning process using a subarray concept according to another embodiment.
  • 35 and 36 are diagrams illustrating a synchronization process and a beam scanning process according to another exemplary embodiment.
  • FIG. 37 is a flowchart illustrating a synchronization process and a beam scanning process according to an embodiment of the present disclosure.
  • FIG. 38 illustrates a process of repeatedly transmitting a Primary Synchronization Signal (PSS) / Secondary Synchronization Signal (SSS) according to a proposed embodiment.
  • PSS Primary Synchronization Signal
  • SSS Secondary Synchronization Signal
  • 39 is a view illustrating a PSS / SSS configuration method related to a proposed embodiment.
  • 40 is a view for explaining another PSS / SSS configuration method related to the proposed embodiment.
  • 41 is a diagram illustrating a configuration of a terminal and a base station according to the proposed embodiment.
  • each component or feature may be considered to be optional unless otherwise stated.
  • Each component or feature may be embodied in a form that is not combined with other components or features.
  • some of the components and / or features may be combined to form an embodiment of the present invention.
  • the order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment, or may be replaced with corresponding components or features of another embodiment.
  • the base station is meant as a terminal node of a network that directly communicates with a mobile station.
  • the specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases.
  • various operations performed for communication with a mobile station in a network consisting of a plurality of network nodes including a base station may be performed by the base station or network nodes other than the base station.
  • the 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an advanced base station (ABS), or an access point.
  • a 'mobile station (MS)' may be a user equipment (UE), a subscriber station (SS), a mobile subscriber station (MSS), a mobile terminal, an advanced mobile station (AMS), a terminal. (Terminal) or a station (STAtion, STA) and the like can be replaced.
  • UE user equipment
  • SS subscriber station
  • MSS mobile subscriber station
  • AMS advanced mobile station
  • Terminal or a station (STAtion, STA) and the like can be replaced.
  • the transmitting end refers to a fixed and / or mobile node that provides a data service or a voice service
  • the receiving end refers to a fixed and / or mobile node that receives a data service or a voice service. Therefore, in uplink, a mobile station may be a transmitting end and a base station may be a receiving end. Similarly, in downlink, a mobile station may be a receiving end and a base station may be a transmitting end.
  • the description that the device communicates with the 'cell' may mean that the device transmits and receives a signal with the base station of the cell. That is, a substantial target for the device to transmit and receive a signal may be a specific base station, but for convenience of description, it may be described as transmitting and receiving a signal with a cell formed by a specific base station.
  • the description of 'macro cell' and / or 'small cell' may not only mean specific coverage, but also 'macro base station supporting macro cell' and / or 'small cell supporting small cell', respectively. It may mean 'base station'.
  • Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802.xx system, 3GPP system, 3GPP LTE system and 3GPP2 system. That is, obvious steps or parts which are not described among the embodiments of the present invention may be described with reference to the above documents.
  • the error value of the oscillator of the terminal and the base station is defined as a requirement, and is described as follows.
  • the UE modulated carrier frequency shall be accurate to within ⁇ 0.1 PPM observed over a period of one time slot (0.5 ms) compared to the carrier frequency received from the E-UTRA Node B
  • Frequency error is the measure of the difference between the actual BS transmit frequency and the assigned frequency.
  • the maximum difference of the oscillator between the base station and the terminal is ⁇ 0.1ppm, and when an error occurs in one direction, a maximum offset value of 0.2 ppm may occur.
  • This offset value is multiplied by the center frequency and converted into Hz units for each center frequency.
  • the CFO value is differently represented by subcarrier spacing, and in general, even when a large CFO value is large, the effect of the OFDM system with a sufficiently large subcarrier spacing is relatively small. Therefore, the actual CFO value (absolute value) needs to be expressed as a relative value affecting the OFDM system, which is called a normalized CFO.
  • the normalized CFO is expressed by dividing the CFO value by the subcarrier spacing. Table 2 below shows the CFO and normalized CFO for each center frequency and oscillator error value.
  • Center frequency (subcarrier spacing) Oscillator offset ⁇ 0.05 ppm ⁇ 0.1 ppm ⁇ 10 ppm ⁇ 20 ppm 2 GHz (15 kHz) ⁇ 100 Hz ( ⁇ 0.0067) ⁇ 200 Hz ( ⁇ 0.0133) ⁇ 20 kHz ( ⁇ 1.3) ⁇ 40 kHz ( ⁇ 2.7) 30 GHz (104.25 kHz) ⁇ 1.5 kHz ( ⁇ 0.014) ⁇ 3 kHz ( ⁇ 0.029) ⁇ 300 kHz ( ⁇ 2.9) ⁇ 600 kHz ( ⁇ 5.8) 60 GHz (104.25 kHz) ⁇ 3 kHz ( ⁇ 0.029) ⁇ 6 kHz ( ⁇ 0.058) ⁇ 600 kHz ( ⁇ 5.8) ⁇ 1.2 MHz ( ⁇ 11.5)
  • a subcarrier spacing (15 kHz) is assumed for a center frequency of 2 GHz (for example, LTE Rel-8 / 9/10), and a subcarrier spacing of 104.25 kHz for a center frequency of 30 GHz or 60 GHz. This prevents performance degradation considering the Doppler effect for each center frequency.
  • Table 2 above is a simple example and it is apparent that other subcarrier spacings may be used for the center frequency.
  • Doppler dispersion causes dispersion in the frequency domain, resulting in distortion of the received signal at the receiver's point of view.
  • Doppler dispersion It can be expressed as.
  • v is the moving speed of the terminal
  • ⁇ means the wavelength of the center frequency of the transmitted radio waves.
  • ⁇ means the angle between the received radio wave and the moving direction of the terminal. In the following description, it is assumed that 0 is 0.
  • the coherence time is in inverse proportion to the Doppler variance. If the coherence time is defined as a time interval in which the correlation value of the channel response in the time domain is 50% or more, It is expressed as In a wireless communication system, Equation 1 below, which represents a geometric mean between a formula for Doppler variance and a formula for coherence time, is mainly used.
  • 1 is a diagram illustrating a Doppler spectrum.
  • the Doppler spectrum or Doppler power spectrum density, which represents a change in the Doppler value according to the frequency change, may have various shapes according to a communication environment.
  • a communication environment such as downtown
  • the Doppler spectrum appears in the U-shape as shown in FIG. 1 shows the center frequency
  • the maximum Doppler variance U-shaped Doppler spectra are shown.
  • FIG. 2 is a diagram showing narrow beamforming according to the present invention
  • FIG. 3 is a diagram showing Doppler spectrum when narrow beamforming is performed.
  • an antenna array including a plurality of antennas may be installed in a small space with a small antenna. This feature enables pin-point beamforming, pencil beamforming, narrow beamforming, or thin beamforming using tens to hundreds of antennas. This narrow beamforming means that the received signal is received only at a certain angle, not in the same direction.
  • FIG. 2A illustrates a case where the Doppler spectrum is U-shaped according to a signal received in an equal direction
  • FIG. 2B illustrates a case where narrow beamforming using a plurality of antennas is performed.
  • the Doppler spectrum also appears narrower than the U-shape due to the reduced angular spread.
  • FIG. 3 it can be seen that Doppler variance appears only in a certain band when the narrow beamforming is performed.
  • the center frequency operates in the band of several GHz to several tens of GHz. This characteristic of the center frequency makes the influence of the CFO due to the Doppler effect or the oscillator difference between the transmitter / receiver caused by the movement of the terminal more serious.
  • FIG. 4 is a diagram illustrating an example of a synchronization signal service zone of a base station.
  • the terminal performs synchronization with the base station by using a downlink (DL) synchronization signal transmitted by the base station.
  • DL downlink
  • timing and frequency are synchronized between the base station and the terminal.
  • the base station transmits the synchronization signal by configuring the beam width as wide as possible so that terminals in a specific cell can receive and use the synchronization signal.
  • path loss is greater than that of a low frequency band in synchronizing signal transmission. That is, in the case of a system using a high frequency band, a cell radius that can be supported compared to a conventional cellular system (for example, LTE / LTE-A) using a relatively low frequency band (for example, 6 GHz or less). This is greatly toned.
  • a conventional cellular system for example, LTE / LTE-A
  • a relatively low frequency band for example, 6 GHz or less
  • a synchronization signal transmission method using beamforming may be used.
  • the cell radius is increased, but the beam width is reduced. Equation 2 below shows the change in the received signal SINR according to the beam width.
  • Equation 2 is the beam width according to the beamforming If received decreases, the received SINR is Fold improvement.
  • Another method for solving the reduction of the cell radius may be considered to repeatedly transmit the same sync signal. This method requires additional resource allocation on the time axis, but has the advantage of increasing the cell radius without reducing the beam width.
  • the base station allocates resources to each terminal by scheduling frequency resources and time resources located in a specific area.
  • this specific zone is defined as a sector.
  • A1, A2, A3, and A4 represent sectors having a radius of 0 to 200 m and widths of 0 to 15 ', 15 to 30', 30 to 45 ', and 45 to 60', respectively.
  • B1, B2, B3, and B4 represent sectors having a radius of 200 to 500 m and widths of 0 to 15 ', 15 to 30', 30 to 45 ', and 45 to 60', respectively.
  • sector 1 is defined as ⁇ A1, A2, A3, A4 ⁇
  • sector 2 is defined as ⁇ A1, A2, A3, A4, B1, B2, B3, B4 ⁇ .
  • the synchronization signal service area of the current base station is sector 1, it is assumed that an additional power of 6 dB or more is required for transmission of the synchronization signal in order for the base station to service the synchronization signal in sector 2.
  • the base station can obtain an additional gain of 6 dB using the beamforming technique to serve sector 2.
  • the service radius can be increased from A1 to B1.
  • A2, A3, and A4 cannot be serviced at the same time. Therefore, when beamforming is performed, a synchronization signal should be separately transmitted to the A2 to B2, A3 to B3, and A4 to B4 sectors. In other words, the base station must transmit a synchronization signal four times beamforming to serve sector 2.
  • the base station can transmit the synchronization signal to all sectors 2, but must transmit the synchronization signal four times on the time axis.
  • the resources required to service sector 2 are the same for both beamforming and iterative transmission.
  • the beam width is narrow, it is difficult for a terminal moving at a high speed or a terminal at the boundary of a sector to stably receive a synchronization signal. Instead, if the ID of the beam in which the terminal is located can be distinguished, there is an advantage that the terminal can determine its own position through a synchronization signal.
  • the repetitive transmission scheme since the beam width is wide, it is very unlikely that the terminal misses the synchronization signal. Instead, the terminal cannot determine its location.
  • 5 is an example of a frame structure proposed in a communication environment using mmWave.
  • one frame consists of Q subframes and one subframe consists of P slots.
  • One slot consists of T OFDM symbols.
  • the first subframe in the frame uses the 0 th slot (slot indicated by 'S') for synchronization purposes.
  • the 0 th slot is composed of A OFDM symbols for timing and frequency synchronization, B OFDM symbols for beam scanning, and C OFDM symbols for informing the UE of system information. The remaining D OFDM symbols are used for data transmission to each terminal.
  • Q, P, T, S, A, B, C, and D may each be arbitrary values and may be values set by a user or automatically set on a system.
  • Equation (3) Denotes the length of an OFDM symbol, the length of a cyclic prefix (CP), and the index of an OFDM symbol, respectively. Denotes a vector of the received signal at the receiver. At this time, Cold reception signal vector of From the first Vector defined by the first element.
  • the algorithm of Equation 3 operates under the condition that two adjacent OFDM received signals in time are the same.
  • Such an algorithm can use a sliding window method, which can be implemented with low complexity, and has a strong characteristic of frequency offset.
  • Equation 4 represents an algorithm for performing timing synchronization by using a correlation between a received signal and a signal transmitted by a base station.
  • Equation 4 denotes a signal transmitted by the base station and is a signal vector previously promised between the terminal and the base station. Equation 4 may produce better performance than Equation 3, but may not be implemented as a sliding window method, and thus requires high complexity. It also has a feature that is vulnerable to frequency offset.
  • Beam scanning refers to the operation of the transmitter and / or receiver to find the direction of the beam that maximizes the receiver's received SINR.
  • the base station determines the direction of the beam through beam scanning before transmitting data to the terminal.
  • FIG. 4 illustrates a sector served by one base station divided into eight regions.
  • the base station transmits beams in the areas (A1 + B1), (A2 + B2), (A3 + B3), and (A4 + B4), respectively, and the terminal can distinguish beams transmitted by the base station.
  • the beam scanning process can be embodied in four processes. First, i) the base station transmits a beam in four areas in sequence. ii) The terminal determines the beam that is determined to be the most suitable among the beams in view of the received SINR. iii) The terminal feeds back information on the selected beam to the base station. iv) The base station transmits data using the beam having the feedback direction. Through the above beam scanning process, the UE can receive downlink data through the beam with optimized reception SINR.
  • the Zadoff-Chu sequence is called a chu sequence or ZC sequence and is defined by Equation 5 below.
  • N is the length of the sequence
  • r is the root value
  • a characteristic of the ZC sequence is that all elements have the same size (constant amplitude).
  • the DFT results of the ZC sequence also appear the same for all elements.
  • Equation 6 the ZC sequence and the cyclic shifted version of the ZC sequence have a correlation as shown in Equation 6.
  • the ZC sequence also has a zero auto-correlation property, it is also expressed as having a constant Amplitude Zero Auto Correlation (CAZAC).
  • Hadamard matrix is defined as Equation 8 below.
  • Equation (8) Denotes the size of the matrix.
  • Equation 9 It can be seen from Equation 9 that the columns are orthogonal to each other.
  • the OVSF code is generated based on the Hadamard matrix and has a specific rule.
  • the first code when branching to the right side of the OVSF code (lower branch), the first code repeats the upper code on the left side twice (mother code), and the second code repeats the high code code once and inverts it once. Is generated. 6 shows a tree structure of the OVSF code.
  • All of these OVSF codes are orthogonal except for the relationship between adjacent higher and lower codes on the code tree.
  • the code [1 -1 1 -1] is orthogonal to [1 1], [1 1 1 1], and [1 1 -1 -1].
  • the OVSF code has the same length as the code length. That is, in FIG. 6, it can be seen that the length of a specific code is equal to the total number of branches to which the corresponding code belongs.
  • RACH random access channel
  • the base station defines a parameter called 'preambleInitialReceivedTargetPower', and broadcasts the parameter to all terminals in the cell through SIB (System Information Block) 2.
  • SIB System Information Block
  • the UE calculates a path loss using a reference signal, and determines the transmission power of the RACH signal by using the calculated path loss and the 'preambleInitialReceivedTargetPower' parameter as shown in Equation 10 below.
  • P_PRACH_Initial, P_CMAX, and PL represent the transmission power of the RACH signal, the maximum transmission power of the terminal, and the path loss, respectively.
  • Equation 10 it is assumed that the maximum transmit power of the terminal is 23 dBm and the RACH reception power of the base station is -104 dBm. In addition, it is assumed that the terminal is arranged as shown in FIG.
  • the terminal calculates a path loss using the received synchronization signal and the beam scanning signal, and determines the transmission power based on this.
  • Table 3 shows the path loss of the terminal and its transmission power.
  • the RACH signal must be transmitted with a very small power (-44 dBm) to match the RACH reception power.
  • the path loss is large, but the required transmission power is 6 dBm.
  • the base station defines a new precoder consisting of a weighted sum of two or more basic precoders applied to a repeatedly transmitted synchronization signal.
  • the base station also defines a plurality of new precoders generated by changing the weighted sum as a codebook.
  • FIG. 8 a case where the number of repetitive transmissions of the synchronization signal is 2 is illustrated, and a repetitive transmission structure of the synchronization signal for obtaining diversity is illustrated.
  • the number of antennas, the length of an OFDM symbol, and the length of a CP of a base station transmitting a synchronization signal , , It is called.
  • You can also use the default precoder We define a new precoder It is defined as In the basic precoder and the new precoder, '0' and '1' represent an order in which a synchronization signal is transmitted, that is, an OFDM symbol.
  • the basic precoder and the new precoder are vector matrices, the size of which is equal to the number of antenna ports of the base station. That is, in FIG. And The size of is 4x1 vector.
  • the codebook defined by the base station is Expressed as a codebook May be understood as Equation 11 below.
  • Precoder in Equation 11 Is the default precoder Precoder Is the default precoder It consists of a difference.
  • the precoder corresponding to the upper subsector is ,
  • the precoder for the lower subsector Are each defined as At this time, the base station is a new precoder defined by the weighted sum [+1 +1] in the first OFDM symbol
  • the new signal is defined as another weighted sum [+1 -1] in the second OFDM symbol. Apply the signal to transmit the synchronization signal. Accordingly, even if the terminal is located at the subsector boundary, it is possible to obtain diversity for the two precoders, thereby accurately distinguishing the synchronization signal.
  • the precoder codebook of the synchronization signal is generalized and defined as in Equation 12 below.
  • Vector from Equation 12 Denotes a precoder applied to the synchronization signal repeatedly transmitted t-th.
  • the sync signal codebook A matrix, defined as, that represents a channel Is the size Is an arbitrary matrix
  • the base station selects any one of the codebooks consisting of a weighted sum of basic precoders and a plurality of different new precoders and applies them to the synchronization signal at each repetition. do.
  • the number of new precoders included in the codebook may be equal to the number of repetitive transmissions of synchronization signals of the base station.
  • the base station in the process of repeatedly transmitting the synchronization signal by the base station, selects a precoder that has not been selected in the codebook and transmits the synchronization signal every repetition. That is, in order to maximize the transmission diversity of the synchronization signal, the base station performs a codebook every repetition of the synchronization signal. Contained in Select a precoder that has not been selected among the two precoders.
  • Equation 11 having a repetition number of 2
  • the codebook When the base station transmits a synchronization signal in the first OFDM symbol Is selected, and the precoder is used to transmit a synchronization signal in the subsequent second OFDM symbol. Select.
  • This process is shown in the structure in which the switch of the RF module is changed on the left side of FIG.
  • Sync signals transmitted through the k th antenna among the 4 transmit antennas are the i th sequence And precoder
  • Equation 13 is generated as follows.
  • Equation (13) Represents an Inverse Discrete Fourier Transform (IDFT) matrix
  • Is Represents the k th element of the precoder.
  • FIG. 9 illustrates a process in which a synchronization signal in the k-th antenna described in Equation 13 is repeatedly transmitted twice.
  • 10 illustrates a process of estimating sequence and timing by a terminal receiving a synchronization signal. 10 illustrates an operation of a terminal side when a base station repeatedly transmits a synchronization signal according to the embodiment described above.
  • Equation 14 an algorithm for synchronizing timing and estimating a sequence from a received synchronization signal may be expressed by Equation 14 below.
  • Equation (14) are trial numbers used in estimating timing and sequence, respectively. Denotes a trial number when the value of Equation 14 is maximized, and denotes an index of a timing and a sequence estimated from a synchronization signal received by the terminal.
  • Equation 14 may be represented as shown in FIG. Four different timings in Figure 10 Is shown, and the magnitude of the correlation between the received signal and the sequence at each time point is shown. Also, in FIG. 10 Is Represents the received signal vector received at the time point, and the length to be. Silver Means the signal after the DFT processing.
  • each timing And sequence index Equation 14 is calculated by applying as a trial number.
  • the terminal calculates the result of equation (14). Since the correlation value calculated by is the largest, the terminal Is determined as the timing of the synchronization signal, and it is determined that the i th sequence is transmitted.
  • Equation 15 the magnitude of the peak value calculated by the UE by Equation 14 is expressed by Equation 15 below.
  • Equation (15) Denotes a channel between the transmitter and the receiver.
  • the received SNR of the UE from Equation 15 is calculated as in Equation 16 below.
  • Equation (16) Denotes the received SNR when the synchronization signal is simply transmitted repeatedly. Shows a received SNR when a precoder is configured to transmit diversity according to the proposed embodiment to transmit a synchronization signal. The former doubles the receive power of the sync signal, while the latter receives two channels. And It is expressed as if And Are independent of each other, The diversity gain of becomes 2. In contrast, Receive power is one channel Since it is expressed only as, the diversity gain is one.
  • the synchronization signal since the synchronization signal must be detectable by all terminals in the cell, the most important factor in the synchronization signal is the stability of the communication link. Considering that the higher the diversity gain, the higher the stability of the communication link, the proposed embodiment can obtain an improved effect compared to the conventional synchronization signal transmission method.
  • FIG. 11 illustrates another embodiment of a process in which a terminal synchronizes timing by using a synchronization signal.
  • the terminal Obtained in the process of calculating the peak value at the time point Store the values on the stack, The stored value can be used to calculate the peak value at the time point.
  • the UE can reduce the computational complexity by avoiding duplicate calculations by utilizing the memory.
  • FIG. 11 Is The terminal is currently obtained in the process of calculating the peak value
  • a process of storing a value on the stack (S1120) is defined as a 'push' operation, and a process of loading and using a pre-stored value from the stack (S1110) is defined as a 'pop up' operation.
  • a process of loading and using a pre-stored value from the stack (S1110) is defined as a 'pop up' operation.
  • the total size of the stack is always Is maintained.
  • the number of random repetition is defined as in Equation 17 below and the size is Becomes That is, the UE stores the calculated values in the stack for the time interval of the length of the OFDM symbol plus the length of the CP, and recalls the stored values when the time interval corresponding to the length of the OFDM symbol and the length of the CP is over. And new calculations.
  • FIG. 12 is a flowchart illustrating a proposed synchronization signal transmission and reception method.
  • the previously proposed and described embodiments are illustrated and described according to a time series flow. Therefore, the above descriptions may be applied to the same or similarly, although not explicitly described in FIG. 12.
  • a precoder set (ie, codebook) for repeatedly transmitting a synchronization signal is shared between a base station and a terminal (S1210).
  • This codebook consists of a plurality of new precoders composed of weighted sums of basic precoders, and the weighted sum is applied differently to each new precoder. Meanwhile, the codebook may be generated by the base station and transmitted to the terminal, or the terminal may directly generate the codebook.
  • the base station selects any one of the precoders constituting the precoder set (codebook) and transmits a synchronization signal (S1220).
  • a synchronization signal As the precoder applied to the synchronization signal, any one of the precoders included in the precoder set may be arbitrarily selected.
  • the base station selects another precoder from the precoder set (codebook) in the next OFDM symbol and repeatedly transmits a synchronization signal (S1230).
  • S1230 any one of the precoders other than the precoder selected in S1220 is selected among the precoder sets. In FIG. 12, it is assumed that the number of repetitive transmissions of the synchronization signal is 2, but when the number of repetitions is higher, the process of S1230 may be repeatedly performed.
  • the terminal performs synchronization with the base station by using the synchronization signal repeatedly received (S1240).
  • a process may be understood as a process of estimating an optimal value by calculating a correlation between a timing and a sequence of a received synchronization signal, and storing and loading intermediate values on a stack in the process of calculating the correlation. Embodiments may be applied.
  • a synchronization signal may be stably transmitted to a terminal.
  • Equation 13 illustrates a synchronization signal transmission structure according to FIGS. 8 to 12.
  • the reception SNR described in Equation 16 may be expressed as Equation 18 below in consideration of path attenuation.
  • the received SNR for the b terminal may be approximated as shown in Equation 19 below.
  • Equation 19 means that the diversity gain for the terminal b can be obtained as two.
  • Equation 20 means that the diversity gain obtained by terminal a is 1 rather than 2.
  • c terminal is reversed Located far from, similar to terminal a, only one diversity gain can be obtained. In other words, according to the embodiments described with reference to FIGS. 8 to 12, sufficient diversity gain can be obtained in the case of terminal b, but not in the case of terminals a and c.
  • the terminal must receive the synchronization signal with a certain quality or higher regardless of the position in the cell. Therefore, hereinafter, an embodiment for improving the point that the UEs obtain different diversity gains according to the position in the cell as described above is proposed.
  • the 'secondary precoder' is the basic precoder described above. Means.
  • the secondary precoder may include two or more 'primary precoders ( Is composed of weighted summation 8 and 12, the plurality of primary precoders ( By the weighted sum of ) Is defined and a new precoder (hereinafter referred to as tertiary precoder) by weighted sum of a plurality of secondary precoders Is defined.
  • Equation 21 the relationship between two precoders is expressed according to Equation 21 below.
  • Equation 21 Denotes the weights of the primary precoders constituting the i-th secondary precoder as a complex number, that is, how the primary precoders are weighted. Denotes the number of primary precoders constituting the i th secondary precoder, Denotes the index of the secondary precoders constituting the i-th secondary precoder.
  • Equation 22 shows an example in which the secondary precoders are composed of a weighted sum of two primary precoders.
  • the secondary precoder may be implemented in a form in which a specific primary precoder is multiplied by a j or -j value that changes a phase.
  • the primary precoders may be designed to equally divide the area where the synchronization signal is transmitted.
  • the primary precoders are designed such that each beam is formed by 30 'to equally divide 120' which is a synchronization signal transmission region.
  • the primary precoders may be designed such that a minimum chordal distance between each other is maximized.
  • the minimum codal distance means the spacing between beams by the precoder
  • the maximum codal distance means the maximum spacing between the beams formed by the precoders, that is, the correlation between the beams is minimized.
  • the primary precoder may be designed to maximize the minimum codal distance using the DFT codebook.
  • 15 to 17 are diagrams illustrating a synchronization signal transmission structure according to another embodiment.
  • embodiments of designing a second precoder using a first precoder in addition to the above descriptions will be described.
  • the secondary precoder is composed of a weighted sum of the primary precoders and may be designed in a comb structure.
  • the comb structure means that the regions in the subsectors of the primary precoders constituting the secondary precoder are not neighboring as shown in FIG. 14, and the minimum distances of the regions in the subsectors of the primary precoders are the same.
  • the secondary precoder in Fig. 15 (a) Primary precoder to construct Wow The regions of do not neighbor each other, and the secondary precoder in FIG. Primary precoder to construct Wow The areas of do not neighbor each other. Furthermore, the second precoder Primary Precoders Composing Wow The minimum distance of the region in the subsector of 30 'is the second precoder Primary Precoders Composing Wow The minimum distance of the region in the subsector of is also equal to 30 '. 2nd precoder Beam area of the secondary precoder It may be understood that the beam area of P is shifted by 30 '.
  • Equation 23 when the secondary precoder is configured using the primary precoder according to the above-described embodiment, the third precoders of Equation 11 may be expressed as Equation 23 below.
  • FIG. 16 illustrates a case where a secondary precoder is designed according to an exemplary embodiment.
  • the phase of is reversed.
  • the phase change of the beam for each time interval is described for each of the regions 1610, 1620, and 1630 shown, the phase of the beam is changed over the first time interval and the second time interval for the region 1610.
  • the beam phase is changed over a total of two time intervals For the area 1630 To change.
  • the terminal a of the embodiment of FIG. 16 is adjacent to the beam over two time intervals. Undergoes a phase change. Accordingly, the terminal a may obtain a diversity gain of 2 for the synchronization signal. Similarly, terminal b is a beam Undergoes a phase shift of By undergoing a phase change of, all terminals in the subsector can obtain the same diversity gain.
  • FIG. 17 illustrates an embodiment of narrower design of an area within a subsector corresponding to primary precoders.
  • four primary precoders are assumed, while in FIG. 17, a secondary precoder is designed through eight primary precoders.
  • the terminal receiving the synchronization signal may obtain a more uniform diversity gain than in the embodiment of FIGS. 14 to 16.
  • FIG. 18 is a flowchart illustrating a synchronization signal transmission and reception method according to another embodiment.
  • FIG. 18 the previously proposed and described embodiments are illustrated and described according to a time series flow. Therefore, the above descriptions may be applied to the same or similarly, although not explicitly described in FIG. 18.
  • a precoder set (ie, a codebook) for repeatedly transmitting a synchronization signal is shared between a base station and a terminal (S1810).
  • a codebook may consist of tertiary precoders composed of weighted sums of secondary precoders, and the weighted sum is applied differently to each secondary precoder.
  • the secondary precoders are composed of weighted sums of other primary precoders, and the secondary precoders do not have neighboring regions in the subsectors of the primary precoders constituting each secondary precoder, and the primary The minimum distances of the regions in the subsectors of the precoders may be designed in the same comb structure.
  • the codebook may be generated by the base station and transmitted to the terminal, and the terminal may directly generate the codebook as described above with reference to FIG. 12.
  • the base station selects any one of the third precoders constituting the precoder set (codebook) and transmits a synchronization signal (S1820).
  • the third precoder applied to the synchronization signal any one of the third precoders included in the precoder set may be arbitrarily selected.
  • the base station selects another third-order precoder of the precoder set (codebook) in the next OFDM symbol and repeatedly transmits a synchronization signal (S1830).
  • S1830 any one of the precoder sets, except for the precoder selected in S1820, is selected. In FIG. 18, it is assumed that the number of repetitive transmissions of the synchronization signal is 2, but when the number of repetitions is higher, the process of S1830 may be repeatedly performed.
  • the terminal performs synchronization with the base station using the repeatedly received synchronization signal (S1840).
  • This process may be understood as a process of estimating an optimal value by calculating a correlation between the timing and the sequence of the received synchronization signal.
  • an embodiment in which the terminal stores and retrieves intermediate values in a stack may be applied in the process of calculating correlation.
  • the stability of the communication link is secured.
  • the synchronization signal may be transmitted to the terminals in the cell with a constant diversity gain without additional signaling overhead.
  • 19 and 20 illustrate a structure of transmitting a synchronization signal and a beam scanning signal for explaining another proposed embodiment. 19 and 20 will be described a synchronization process and a beam scanning process according to the above-described synchronization signal transmission and reception method.
  • FIG. 19 illustrates a process of a base station switching four beams during four time slots and transmitting a synchronization signal.
  • the terminal performs a synchronization process using the received synchronization signals, and simultaneously performs a beam scanning process.
  • the terminal 1900 performs synchronization through the second beam (FIG. 19 (b)) in which the reception power is sensed the largest, and the base station can determine that the beam selected by the terminal can be distinguished from other beams. Map beams in different sequences.
  • the terminal 1900 has a sequence of beams selected by itself. It can be seen that the beam scanning process is performed by feeding back the selected beam to the base station.
  • the signal transmitted by the base station is designed based on the Zadoff-Chu (ZC) sequence.
  • the cell ID of the base station may be used as a root value of the ZC sequence, and the beam ID may be used as a cyclic shift value of the ZC sequence.
  • a sequence The root value in And the cyclic shift value is Defined as
  • Is a system parameter value and is generally set to be greater than the channel's delay spread maximum. Terminal sequence Using three cells and four beams of each cell can be distinguished, and this process is expressed by Equation 24 below.
  • the terminal simultaneously performs timing synchronization, cell ID estimation, and beam ID estimation through Equation 24, and this process is represented in FIG.
  • the terminal is configured to include a total of 12 correlators in order to simultaneously distinguish three cells and four beams, and 12 correlators operate together in every time slot.
  • the terminal since only the cell needs to be distinguished, the terminal is configured to include a total of three correlators.
  • the mmWave communication system includes a beam scanning process, requiring four times the processing power of LTE. As a result, according to the scheme proposed above, the computational complexity required for the synchronization process of the terminal is increased four times.
  • 21 to 23 illustrate a structure of transmitting a synchronization signal and a beam scanning signal according to a proposed embodiment.
  • the beam ID is defined as weights applied to the weighted sum of the aforementioned basic precoder (or the secondary precoder).
  • Equation 25 shows a synchronization signal codebook when the number of repetitions is two.
  • Equation 25 uses the codebook described in Equation 11 as a weighting matrix ( ).
  • First column in equation (25) Each element of Is the primary precoder (secondary precoder) Represents the weight over time. Similarly, the second column Each element of the second precoder Represents the weight over time.
  • the base station and the terminal Each Beam ID and Is determined by the beam ID.
  • each column constituting a codebook (that is, a weight matrix) applied to the transmission of the synchronization signal is used as a beam ID for distinguishing each beam in the beam scanning process.
  • Equation 26 the case where the number of repetition of the synchronization signal is 4 will be described using Equation 26 as an example.
  • Equation (26) is a representation of the codebook when the number of repetitions of the synchronization signal is 4 by a weight matrix. Similar to the equation (25), the first, second, third and fourth columns of the weight matrix Are defined as beam IDs.
  • each beam is transmitted as shown in FIG. 21 during four timeslots.
  • FIG. 21 unlike FIG. 19, four beams are simultaneously transmitted in each timeslot, and the sign of the transmitted sequence varies according to the timeslot.
  • beams transmitted to respective regions within a sector are directed from the top to the bottom. Corresponds to each. That is, the beam transmitted to the uppermost region And the beam transmitted in the lowest region Corresponds to.
  • the terminal when the synchronization signal is transmitted, the terminal performs synchronization according to Equation 27 below to estimate timing synchronization and a sequence (cell ID) of the synchronization signal.
  • Equation 27 the beam scanning process for estimating the beam ID is not performed simultaneously with the synchronization process.
  • the number of correlators of the terminal is reduced to 4 as compared to 12 of FIG. 20 as shown in FIG.
  • the computational complexity of the terminal is greatly reduced, which may solve the above-described problem.
  • the following describes a process of performing beam scanning after the terminal performs synchronization to estimate timing synchronization and sequence.
  • Equation 29 The terminal performs a beam scanning process based on Equation 28. First, by multiplying both sides of Equation 28 by the inverse of the weight matrix, Equation 29 may be obtained.
  • Equation 29 the result calculated through the matrix operation is represented by Equation 30 below.
  • the terminal compares four power values obtained according to Equation 30, and selects the largest value. For example, the element of the first row If the value appears to be the largest, the terminal end , It can be understood as larger. That is, the terminal in FIG. It can be seen that the beam of the first region generated by is received more strongly than the beams of the other regions. In other words, the terminal may know that it is located in the first area within the sector. That is, the terminal Value is the first column of the weight matrix This is because it knows that the value is calculated using, and as the codebook is shared between the base station and the terminal end This is because the UE knows in advance that it is mapped to.
  • an element in Equation 30 If the value of appears to be the largest, the terminal You can see that the value is the largest. That is, the terminal in FIG. It can be seen that the beam of the last region generated by is received more strongly than the beam of the other region. Accordingly, the terminal has a position in its sector It can be seen that the last region corresponding to.
  • the terminal may distinguish the beams by using the weight matrix of the synchronization signal repeatedly received (that is, the beam scanning process may be May be performed).
  • the terminal may distinguish the beams. Accordingly, the number of sequences to be found by the terminal in timing estimation is reduced by the number of cell IDs, and the synchronization complexity of the terminal is greatly reduced.
  • the columns of the weight matrix may be configured to be orthogonal to each other.
  • Equations 25 and 26 represent weight matrices when the number of repetitions is 2 or 4, respectively.
  • a process of applying an inverse of the weight matrix in Equation 28 may be simplified.
  • the columns of the weighting matrix are configured to be orthogonal to each other, such that the vector representing the weighted sum applied to the primary (secondary) precoder in a particular time slot is orthogonal to the vector representing the weighted sum applied to another time slot. it means.
  • the sync signal codebook Each vector comprising It may be understood that codebooks are designed to allow each other to work together. Such a vector may be understood as an orthogonal cover code (OCC) in that codes are orthogonal to each other.
  • OCC orthogonal cover code
  • the codebook may be designed using a Hadamard matrix described in Equation 8, or may be designed using a DFT matrix.
  • the Hadamard matrix can be simply generated for any number of iterations, and the implementation complexity is very low because the values of each element are defined by addition and subtraction only.
  • the DFT matrix can also be simply generated for any number of iterations, where the values of each element , (N is the number of repetitions). For example, the DFT matrix when the number of repetitions is 4 may be generated as in Equation 31 below.
  • the DFT matrix In the case of the DFT matrix, if the number of repetitions is 2, the complexity is the same as that of the Hadamard matrix. If the number of repetitions is 4 or less, the DFT matrix can be generated simply by changing the phase. The rise can be minimized.
  • the beam ID may be defined by both a weight and a sequence applied to the basic precoder.
  • the embodiments described with reference to FIGS. 21 and 22 when the channel changes rapidly while the synchronization signal is repeatedly transmitted, the performance of beam scanning may be degraded.
  • the embodiment illustrated in FIG. 23 proposes a method of generating a beam ID by considering not only a weight matrix but also a sequence.
  • the base station performs two consecutive timeslots. Are transmitted simultaneously, and in FIG. 23 (c) and FIG. 23 (d), the base station Send simultaneously.
  • the base station is transmitted in the first two timeslots Transmitted in the two timeslots
  • the first two timeslots contain a sequence ((A) and (b)), and in the following two timeslots, the sequence , 23 (c) and 23 (d).
  • the number of correlators of the terminal increases by that amount.
  • the section in which the channel should not be changed is reduced to two timeslots, thereby making it more robust to sudden changes in the channel.
  • FIG. 24 is a flowchart illustrating a synchronization process and a beam scanning process according to another embodiment of the present disclosure.
  • FIG. 24 the previously proposed and described embodiments are illustrated and described according to a time series flow. Therefore, although not explicitly described with reference to FIG. 24, the contents described above with reference to FIGS. 19 to 23 may be identically or similarly applied.
  • a precoder set (ie, a codebook) for repeatedly transmitting a synchronization signal is shared between a base station and a terminal (S2410).
  • a codebook may consist of tertiary precoders composed of weighted sums of secondary precoders, and the weighted sum is applied differently to each secondary precoder.
  • each of the weighting vectors (ie, OCCs) used for generation of the third order precoders constituting the precoder set may be configured to be orthogonal to each other.
  • the codebook may be generated by the base station and transmitted to the terminal, and the terminal may directly generate the codebook as described above with reference to FIG. 12.
  • the base station selects any one of the third precoders constituting the precoder set (codebook) and transmits a synchronization signal (S2420).
  • the third precoder applied to the synchronization signal any one of the third precoders included in the precoder set may be arbitrarily selected.
  • the base station selects another third-order precoder of the precoder set (codebook) in the next OFDM symbol and repeatedly transmits a synchronization signal (S2430).
  • S2430 any one of the precoder sets, except for the precoder selected in S2420, is selected. In FIG. 24, it is assumed that the number of repetitive transmissions of the synchronization signal is 2, but if the number of repetitions is higher, the process of S2430 may be repeatedly performed.
  • the terminal performs synchronization with the base station by using the synchronization signal repeatedly received (S2440).
  • This process may be understood as a process of estimating an optimal value by calculating a correlation between the timing and the sequence of the received synchronization signal.
  • an embodiment in which the terminal stores and retrieves intermediate values in a stack may be applied in the process of calculating correlation.
  • the terminal When the synchronization is completed by estimating the timing and the sequence for each timeslot in S2440, the terminal performs the beam scanning process using the synchronization signals received in S2420 and S2430 (S2450). That is, the terminal performs the process described in Equation 28 to Equation 30 with respect to the correlation values obtained while performing synchronization for each time slot, and accordingly, the UE can distinguish the most strongly received beam from among the plurality of beams. have. Through this beam scanning process, the terminal can distinguish its own position (ie, subsector) in the sector.
  • the base station introduces OCC into the codebook, thereby allowing the terminal to perform beam scanning without allocating an additional sequence for beam scanning. Accordingly, the terminal can minimize the increase in complexity for implementing the beam scanning process.
  • the beam broadening technique will be described before explaining the proposed embodiment.
  • the size of a linear antenna array If, the beamforming gain is Although proportional to, the beam width or half power beam width (HPBW) Inversely proportional to Therefore, the larger the size of the linear antenna array, the better beamforming gain can be obtained, while the beam width becomes narrower.
  • a broadcast channel or a control channel requires a wide beam width while requiring a low SNR, a relatively high beamforming gain is not required.
  • a large antenna arrangement requires a new beamforming design to satisfy the above-described characteristics.
  • the beamforming design described below is called a beam extension technique.
  • FIG. 25A beamwidths of eight antenna arrays are shown.
  • the width of the beam generated by the antenna array including eight antennas is 15 ', Is a vector representing the coefficients of the linear antenna array.
  • FIG. 25 (b) shows the result of applying the beam extension technique to the antenna arrangement of FIG. 25 (a).
  • FIG. 25 (b) shows the beamwidth when only two of the eight antennas are on (on) and the remaining antennas are off (off).
  • Figure 25 (b) Represents the first column of the DFT matrix of size 2, Is in a relationship.
  • the number of antennas involved in beamforming is reduced to one quarter, while the beam width is expanded four times from 15 'to 60' and the beamforming gain is reduced by 6.6227 dB.
  • This method not only has a beamforming loss but also has a low efficiency due to power loss when assuming an active antenna system (AAS) to be described later.
  • AAS active antenna system
  • FIG. 25 (c) shows the result of applying another beam extension technique.
  • eight antennas are divided into two subarrays (or subarrays), and each subarray is defined as four consecutive antennas.
  • the first subarray and the second subarray are coefficients of the second and fourth columns of the DFT matrix of size 4, respectively. Has, Satisfies the relationship.
  • each sub-array is composed of four antennas and has a beam width of 30 ', and the beamforming gain is reduced by 4.8165 dB.
  • the total beam width satisfies 60 '.
  • the beam extension technique of FIG. 25 (c) does not cause power loss since all antennas are operating.
  • the size of all antenna coefficients is equal to 1 while two multiple beams are transmitted.
  • the size of a linear antenna array ego, When applying the beam extension technique using two subarrays, the ratio of the expanded beamwidth becomes As a result, the beam extension technique incorporating the sub-array concept of FIG. 25 (c) is a method that can extend the beam width while using all antennas.
  • the precoder applied to the synchronization signal is a weighted sum of basic precoders (or secondary precoders) as described in Equation 12.
  • the size of each element of the sync signal precoder is different at this time.
  • the default precoder Are different columns of a DFT matrix having a size of 4, and consider a case defined as Eq.
  • Equation 33 the synchronization signal codebook described with reference to FIG. 21 is defined as in Equation 33.
  • each element has a different size from the basic precoder.
  • an AAS having a phase shifter and a power amplifier for each antenna is considered.
  • the phase and magnitude of each element of the sync signal precoder are implemented by a phase shifter and a power amplifier of an individual antenna corresponding to the element.
  • a signal In order to minimize power loss under such an AAS antenna structure, a signal must be transmitted by changing a phase for each antenna while the outputs of all power amplifiers are the same. This process assumes that the coefficients of the precoder are the same. However, as described above, the precoder coefficient of the synchronization signal may vary depending on the configuration of the antenna, and thus may not satisfy this condition, resulting in power loss.
  • the beam extension technique is a technique for transmitting a beam by controlling all subarrays independently by grouping all antennas. In this case, it is possible to control the beam direction by adjusting only the phase in a state where the power amplifier outputs of all the antennas are fixed in the same manner.
  • FIG. 27 shows an example of an antenna arrangement with 32 antennas and four subarrays. In this case, each sub-array is configured to include eight antennas and generates a beam having a width of 15 '. Each sub-array may individually control the direction of the generated beam, so that the beam structure of FIG. 27 may be comprehensively implemented.
  • each precoder corresponding to each sub-array is shown.
  • the coefficient size of each precoder is the same and only the phase is different.
  • the synchronization signal precoder used in the synchronization process is defined as a stack of two or more basic precoders (or the above-described secondary precoders).
  • the respective sync signal precoders are defined by different weights of the respective basic precoders. Equation 34 further illustrates the concept that the synchronization signal precoder is defined as a stack of basic precoders.
  • each precoder included in the sync signal codebook includes four basic precoders ( ) Is designed to be concatenated in the column direction. In this case, the weights of the respective basic precoders to be concatenated are defined differently for each tertiary precoder.
  • Equation (35) Is the size Phosphorus vector Is a diagonal matrix with. vector May be defined as a matrix as in Equation 36 below, and the matrix of Equation 36 is the weight matrix described above. The size of the weight matrix is to be.
  • the third order precoders defined by Equations 34 to 36 are composed of a plurality of concatenated basic precoders, and each basic precoder performs beamforming by independently controlling antenna subarrays.
  • Equation 37 the received signal of the terminal may be expressed as Equation 37 below.
  • Equation 38 Received signal in equation 37 And sequence Correlation values between Equation 37 is expressed as Equation 38.
  • Equation 38 is the same as Equation 28.
  • the beam scanning process to which the sub-array concept and the beam extension technique are applied can be performed in the same manner as the above-described embodiment. That is, although the base station does not separately generate or allocate a beam ID for the beam scanning process, the terminal distinguishes beams by using a weight matrix of synchronization signals repeatedly received according to the embodiments described in Equations 28 to 30. (I.e., the beam scanning process is performed). In the beam scanning process, the UE may estimate the reception power of each of the beams, and select the beam having the best reception power based on this.
  • the synchronization signal codebook is defined as third-order precoders generated by concatenating basic precoders by utilizing the fact that the coefficient sizes of the synchronization signal codebooks are the same. Accordingly, the beam scanning process can be designed in the same manner as previously proposed while minimizing the power loss during the synchronization process.
  • FIG. 28 shows another embodiment of the proposed method.
  • a sequence input to each radio frequency chain is changed every time slot.
  • the third precoder is designed differently for each time slot while inputting the same sync sequence in all time slots, in FIG. 28, the sync sequence is input differently for each time slot with the third precoder kept the same. That's the way.
  • the RF chains are connected one by one.
  • Sync sequence through each RF chain Is input, and different synchronization sequences may be transmitted and input for each RF chain.
  • all time slots Send it.
  • sequences are generated during four time slots (TS). Are entered in order.
  • the sync signal precoder (third precoder) Is defined as in Equation 39, and has the same value for four time slots.
  • the rightmost side of (40) is the same as the rightmost side of (37).
  • the same result can be obtained by changing the input synchronization sequence in accordance with the time slot, instead of the scheme of FIG. 27 in which the synchronization signal precoder is changed in accordance with the time slot.
  • the terminal may perform the same synchronization process and beam scanning process described above with reference to FIG. 28.
  • the third precoders constituting the codebook are defined as a plurality of concatenated basic precoders (secondary precoders).
  • the basic precoders may be defined by concatenating two or more primary precoders.
  • the beam of the secondary precoder will comprise beams of contiguous primary precoders.
  • Secondary precoder in FIG. 29 Is the first precoder as Are defined by concatenating them.
  • the superscript of each precoder indicates the size of the corresponding precoder, and the subscript indicates the precoder index.
  • Beam in Figure 29 Silver two beams It is designed to include. That is, according to the embodiment of FIG. 29, the primary (secondary) precoder having the wide beam 30 ′ is defined by concatenating the primary precoders having the narrow beam 15 ′. Furthermore, the sync signal codebook defined by concatenating the basic precoder may be expressed as in Equation 42.
  • the terminal has a wide beam. Can be distinguished, while having a narrow beam Cannot be distinguished. That is, compared to FIG. 21, according to the embodiment of FIG. 30, the time slot required for sequence transmission is reduced by half, but the beam resolution is also reduced by half.
  • FIG. 31 is a flowchart illustrating a synchronization method according to a proposed embodiment.
  • the embodiments proposed and described with reference to FIGS. 25 to 30 are illustrated and described according to a time series flow, and the above descriptions may be identically or similarly applied, even if not explicitly described with reference to FIG. 31.
  • a precoder set for repeatedly transmitting a synchronization signal is shared between a base station and a terminal (S3110).
  • a codebook may consist of tertiary precoders generated by concatenating secondary precoders.
  • the weights applied to the respective secondary precoders to configure the tertiary precoder may be defined differently for each of the plurality of tertiary precoders constituting the precoder set.
  • the weights applied to the secondary precoders are the same in magnitude and differ only in phase.
  • each of the secondary precoders corresponds to an antenna sub-array of some antennas constituting the antenna array of the base station.
  • the codebook may be generated by the base station and transmitted to the terminal, or the terminal may directly generate the codebook.
  • the base station selects any one of the third precoders constituting the precoder set (codebook) and transmits a synchronization signal (S3120).
  • the third precoder applied to the synchronization signal any one of the third precoders included in the precoder set may be arbitrarily selected.
  • the base station selects another third-order precoder of the precoder set (codebook) in the next OFDM symbol and repeatedly transmits a synchronization signal. In each iteration, the base station selects one of the third precoders except for the precoder which is already selected, and transmits a synchronization signal.
  • the base station controls the antenna sub-arrays through each of the plurality of concatenated secondary precoders constituting the tertiary precoder. Since each of the secondary precoders corresponds to an antenna subarray, the base station can achieve the beam extension technique by controlling the plurality of antenna subarrays through the tertiary precoder applied in one time slot.
  • the terminal performs synchronization with the base station by using the synchronization signal repeatedly received (S3130).
  • This process may be understood as a process of estimating an optimal value by calculating a correlation between the timing and the sequence of the received synchronization signal.
  • an embodiment of storing and recalling intermediate values on a stack may be applied in the process of calculating correlation.
  • the terminal may repeatedly perform a beam scanning process using the received synchronization signals. That is, the terminal performs the process described in Equation 28 to Equation 30 with respect to the correlation values obtained while performing synchronization for each time slot, and accordingly, the UE can distinguish the most strongly received beam from among the plurality of beams. have. Through this beam scanning process, the UE can distinguish its own position (ie, subsector) in the sector, and the beam scanning process may be similarly applied to the process described with reference to FIG. 24.
  • each of the secondary precoders constituting the tertiary precoder may be defined by concatenating a plurality of primary precoders.
  • hybrid beamforming the analog beamforming is fixed while the digital beamforming process is reduced to reduce the feedback burden of the terminal.
  • the analog beamforming is defined differently for each antenna sub-array so that the beam extension technique is applied.
  • Hybrid beamforming is not suitable for synchronous signal transmission because the envelope of the beamforming is fixed.
  • the beamforming is widely extended and thus the synchronous signal transmission is more efficient.
  • FIGS. 32 to 34 describe embodiments of the contents described above with reference to FIG. 28.
  • the third precoder which is applied to both subarrays, is fixed similarly to that of FIG. 28.
  • the third precoder at this time is defined as described in Equation 39, and is fixed for four time slots.
  • the reference sequence with antenna subarrays over the RF chain over four time slots. May be input, and the reference sequence may be multiplied by a predetermined weight for each time slot.
  • a sequence obtained by multiplying a reference sequence by a weight is called a synchronization sequence.
  • This weight may be understood as the aforementioned Orthogonal Cover Code (OCC) and may be determined differently for each antenna sub-array (or RF chain).
  • OCC Orthogonal Cover Code
  • a series of matrices in which the reference sequence is multiplied by a weight over a predetermined time slot is defined as a signature. That is, the signature is a concept corresponding to a synchronization sequence defined for one antenna sub-array, and since the signatures are independent of each other, the receiving terminal can distinguish each signature.
  • FIG. 32 The example shown in FIG. 32 is demonstrated.
  • the horizontal axis represents time slots and the vertical axis represents antenna subarrays.
  • Reference sequence for four time slots for the 0th antenna subarray The synchronization sequence generated by multiplying by the weight [1 1 1 1] is input to the RF chain.
  • a weighted sequence [1 1 -1 -1] is multiplied by the reference sequence for four time slots to generate a synchronization sequence
  • the weight for the second antenna subarray [1 -1 1- 1] is multiplied to generate a sync sequence
  • a weight sequence [1 -1 -1 1] is multiplied for the third antenna sub-array to generate a sync sequence.
  • the reference sequence is fixed in every time slot ( ) May be multiplied by different weights to generate a sync sequence.
  • the signatures are generated by multiplying weight values that are orthogonal to each other even if the reference sequences are the same, and thus, the receiving terminal may distinguish the signatures during the synchronization process and the beam scanning process.
  • FIG. 33 illustrates another embodiment.
  • the reference sequences used to generate the synchronization sequence may be different for each time slot, and in this case, the same reference sequence may be applied to all antenna sub-arrays for each time slot.
  • the synchronization sequence applied to the zeroth antenna subarray is to be.
  • the synchronization sequence applied to all antenna subarrays in the first time slot is to be.
  • the same reference sequence is used for generating a synchronization sequence for every antenna sub-array in each time slot, although different for each time slot.
  • the reference sequence may be multiplied by a predetermined weight to generate the synchronization sequence.
  • the weights are orthogonal to each other even if the reference sequences vary in the same manner over a plurality of time slots, similarly to FIG. Can be.
  • each signature may correspond to specific information related to a synchronization process and / or a beam scanning process.
  • each signature may represent a cell ID or other system information related to the cell ID, or may simultaneously indicate information about the frequency band of the cell together with the cell ID.
  • the maximum number of possible sequence combinations is to be.
  • the maximum number of signatures defined differently also , With the signatures defined Information corresponding to four bits can be represented.
  • Equation 43 a set of criteria sequences When defined as, a sequence combination that can be generated over two time slots is given by Equation 43 below.
  • Equation 43 since the number of sequences is two and the number of time slots is two, the number of sequence combinations is four.
  • Four sequence combinations according to Equation 43 mean four different signatures, and each signature may be mapped to specific information (cell ID) according to Equation 44 below.
  • a sequence combination of may be generated. Accordingly, a total of 81 signatures can be defined.
  • FIGS. 32 and 33 illustrates a synchronization process of a terminal when a base station transmits a synchronization signal according to the embodiments described with reference to FIGS. 32 and 33.
  • Equation 45 shows an example in which the base station transmits a synchronization sequence during two time slots through two antenna sub-arrays, and an example of generating a synchronization sequence through different reference sequences for each time slot according to FIG. 33. Indicates.
  • Equation 45 since the reference sequence may be changed every time slot, the synchronization process of the terminal described above in Equation 24 is changed as in Equation 46 below.
  • Equation 46 The number of sequences to be found in From dog The dog will grow. Also, the number of time slots If increasing to, the total number of sequences to find becomes
  • FIG. 34 The receiver structure of FIG. 34 is an extension of the receiver structure of FIG. 11, and two synchronization sequences during two time slots according to Equation 45 Will be described as an example.
  • the proposed receiver includes two correlators to calculate the correlation between the received signal and the synchronization sequence.
  • the correlator is shown in FIG. 'Is displayed. Similar to the case of FIG. 11, the receiver of FIG. 34 stores a value calculated in one correlator on a stack (or a memory), and then adds or subtracts a value calculated at another time in the same correlator ( Calculate the correlation value.
  • values calculated in a particular correlator and stored in the stack are indicated by solid lines when used in the same correlator, and dotted lines when values stored in the stack are used in other correlators. That is, the correlation value calculated by the correlator at one point may be stored on the stack and used again by two different correlators at different points in time.
  • the receiver of FIG. 34 may calculate four correlation values using two correlators.
  • the complexity of the receiver varies greatly depending on the number of correlators, the difference between the complexity of the receiver of FIG. 34 and the complexity of the receiver of FIG. 11 is insignificant.
  • the receiver of FIG. Correlations can be calculated while increasing complexity.
  • the synchronization process performed according to the embodiment proposed in FIGS. 32 to 34 may be operated similarly to the process described with reference to FIG. 31. That is, in FIG. 32 to FIG. 34, the synchronization sequence is inputted differently for each time slot while one third precoder is fixed in the synchronization signal repetitive transmission process.
  • the base station may change the reference sequence input to the RF chain corresponding to each antenna sub-array for each time slot.
  • the base station may generate the synchronization sequence by changing the weight multiplied by the reference sequence while fixing the reference sequence over the time slot.
  • the method of connecting the secondary precoders in the process of configuring a fixed third precoder may be similarly applied to those described with reference to FIG. 31 and the corresponding exemplary embodiments.
  • the terminal may not only perform synchronization by using the repeatedly received synchronization signal but also acquire additional information (ie, signature) indicated by the combination of synchronization sequences. That is, the combination of reference sequences selected and used in the synchronization signal transmission process may represent additional information of the base station to be used in the synchronization / beam scanning process (eg, cell ID information, frequency band information, or other system information). . Therefore, the terminal may check the combination of the synchronization sequence from the received synchronization signal, thereby obtaining additional information corresponding to the identified combination, and may be used in a later synchronization / beam scanning process.
  • additional information ie, signature
  • the AAS antenna structure having a total of 16 antennas includes a total of 4 antenna subarrays each having 4 antennas.
  • the antenna sub-arrays can transmit beams in independent directions as described above.
  • the precoder corresponding to each antenna subarray is In this case, the coefficient size of each precoder is the same and only the phase is different.
  • the proposed new embodiment differs from the above-described embodiments in that different reference sequences are used for all sync beams transmitted in the same sector.
  • FIG. 28 illustrates a method in which a precoder is fixed and an OCC applied to a sequence varies for each time slot
  • the input sequence itself may be changed every time slot in the proposed embodiment.
  • the OCCs applied to the sequences are different for each sector, and sectors are separated from each other through the OCC. That is, in the proposed embodiment, sectors are identified through OCC, and sync beams in sectors are identified through a sequence.
  • the OCC applied to the sequence may be composed of a set of orthogonal vectors, or may be composed of a set of quasi-orthogonal vectors.
  • sectors I to VI represent different sectors, and sectors I to VI are physically adjacent to each other in the order shown.
  • sector II is adjacent up and down sector I and sector III
  • sector I is adjacent up and down sector II and sector VI. Therefore, a total of six sectors are sequentially arranged adjacent to each other to constitute the overall coverage of the base station.
  • 'Sequence' and 'OCC' mean reference sequences repeatedly input to each sector and OCC applied to the reference sequence.
  • four reference sequences are defined over a total of four time slots for one sector, and each reference sequence corresponds to a different narrow beam.
  • the terminal and the base station may share each other in advance about the relationship between the sequence and the OCC shown in FIG. 35, and the information about the relationship may be shared between the terminal and the base station in the process of sharing a precoder set for repeated transmission of synchronization signals. Can be shared.
  • OCC may be commonly applied to sequences for any one sector in FIG. 35
  • different OCCs may be applied to each sequence.
  • a common OCC is applied to sequences for sectors I, II, III, and IV, but a different OCC is applied to two sequences for sectors V and VI.
  • Sequence of sector V OCC ⁇ ++++ ⁇ applies for, but For this, OCC ⁇ ++- ⁇ applies.
  • FIG. 36 shows four narrow beams defined within each sector, and reference sequences and OCCs corresponding to the narrow beams. 36 shows an example implementation of sectors I, II, III, V, VI.
  • each reference sequence Corresponds to four narrow beams in the sector, respectively.
  • the OCC ⁇ +-+- ⁇ shown in FIG. 35 is applied to four OFDM symbols (that is, time slots) for the reference sequence. That is, in the first and third OFDM symbols, all reference sequences are multiplied by one, and in the second and fourth OFDM symbols, all reference sequences are multiplied by -1 and a synchronization sequence is transmitted.
  • narrow beams located at the end of the up / down direction of sector II in FIG. 36 are adjacent to the narrow beam located at the downward end of sector I and the narrow beam located at the upper end of sector III, respectively.
  • the reference sequence input to the beam at the upstream end of sector II The reference sequence input to the beam at the downward end of sector I Is different.
  • the reference sequence input to the beam at the downward end of sector II Is the reference sequence input to the beam at the upstream end of sector III. Is different.
  • the OCC applied to sector II is also different from that of sector I and sector III.
  • the same reference sequence may be input to an area corresponding to the two narrow beams. That is, the sector I of FIG. ⁇ ++++ ⁇ is applied as OCC in the area corresponding to. Meanwhile, sector II, which is a narrow beam region adjacent to the corresponding region, Since ⁇ +-+- ⁇ is applied to the corresponding region of as the OCC, even if the same reference sequence is input to the regions corresponding to the two narrow beams, the terminal can distinguish the two. In this case, the same reference sequence can be used despite being an adjacent narrow beam region.
  • the synchronization process and the beam scanning process according to the above-described embodiments may operate according to the process described with reference to FIG. 31 and the process described with reference to FIGS. 32 to 34. That is, the precoder set (ie, codebook) for repetitive transmission of the synchronization signal is shared between the base station and the terminal in advance (S3710).
  • the precoder set ie, codebook
  • a sequence for synchronization (the aforementioned reference sequence) is input differently for each time slot and operates (S3720).
  • different sequences are repeatedly input over a plurality of time slots for each antenna sub-array corresponding to each narrow beam in the sector.
  • different OCCs may be applied to a sequence for each sector, so that synchronization sequences between sectors may be distinguished from each other.
  • the method of connecting the secondary precoders in the process of configuring a fixed third precoder may be similarly applied.
  • the terminal may perform a synchronization and beam scanning process using a sequence of synchronization signals repeatedly received and an OCC. Specifically, the terminal first estimates the timing synchronization by receiving the synchronization signal, and selects the OCC having the largest value of the correlation calculation. The sector is distinguished through the OCC has been described above. Subsequently, the terminal checks both the synchronization sequence and the OCC used to generate the received synchronization signal by estimating the sequence of the synchronization signal. Since the synchronization sequence corresponds to a specific area corresponding to the narrow beam in the sector, the terminal that has confirmed the synchronization sequence can know its position in the sector corresponding to the sequence, thereby completing the beam scanning process. For example, the sequence estimated by the terminal If the OCC is ⁇ +-+- ⁇ , the UE can determine the region corresponding to the sector VI and the second narrow beam with reference to the relationship between the sequence-OCC previously obtained in S3710 (S3730).
  • the additional information may also be delivered to the terminal as described with reference to FIGS. 32 to 34 (ie, a signature).
  • the combination of the reference sequence and the OCC selected and used in the synchronization signal transmission process may represent additional information of the base station to be used in the synchronization / beam scanning process (eg, cell ID information, Frequency band information, or other system information).
  • the terminal may check the synchronization sequence and the OCC from the received synchronization signal, thereby obtaining additional information corresponding to the identified combination and use the same in subsequent synchronization / beam scanning processes.
  • the above-described embodiment is similar to the above-described embodiment except that the schemes for specifying the sector and the narrow beam are different from those described above with reference to FIGS. 32 to 34, and thus the complexity of the terminal is the same in both schemes. Meanwhile, in the present embodiment, since different reference sequences are used for each narrow beam region in the same sector, the occurrence of a nulling phenomenon due to the interference between beams can be minimized.
  • FIG. 38 illustrates a process of repeatedly transmitting a Primary Synchronization Signal (PSS) / Secondary Synchronization Signal (SSS) according to a proposed embodiment.
  • PSS Primary Synchronization Signal
  • SSS Secondary Synchronization Signal
  • FIG. 38 shows one sector consisting of four subsectors.
  • analog beamforming is used to form a thin RF beam.
  • path loss occurs largely due to the characteristics of the mmWave communication environment, a method of transmitting PSS and SSS for each subsector is considered for stable synchronization.
  • 39 is a view illustrating a PSS / SSS configuration method related to a proposed embodiment.
  • an embodiment proposes a method of repeatedly transmitting the PSS and the SSS for each subsector in a sector.
  • the proposed embodiment describes a method of performing synchronization while controlling interference between SSSs through a total of three methods, i) scramble method, ii) FDM method, and iii) OCC method.
  • 39 (a) and 39 (b) show an example of PSS / SSS implementation of two different sectors. In FIG. 39, it is assumed that sectors I and II are physically adjacent to each other. As shown in Figs. 39A and 39B, the PSS and SSS occupy N RBs and M RBs on the frequency axis, respectively. 39 (a) and 39 (b) show that the PSS / SSS is repeatedly transmitted over four OFDM symbols on the time axis, and the PSS and SSS are multiplexed by the FDM scheme and transmitted together for each OFDM symbol. do.
  • the physical layer ID which is one of the synchronization parameters used in the synchronization process, is defined by the PSS sequence set and the OCC of a specific sector.
  • the scrambling code to be applied to the SSS is determined using a physical layer ID defined by the PCC sequence set and the OCC.
  • the generation of the scrambling code in the OCC of the sector can be used to minimize the occurrence of the interference of the SSS as described above.
  • the synchronization parameter may correspond to some information of the physical layer ID of a specific base station.
  • the PSS sequence set is composed of one PSS sequence.
  • the PSS sequence set is composed of two or more PSS sequences.
  • the OCC defined for one sector may be the same or different for each sector, as described above.
  • the sector I of FIG. 39A and the sector II of FIG. 39B transmit SSS through the same frequency band, interference occurs between the two sectors.
  • the PSS sequence index is used at the scrambling code generation.
  • Equation 47 shows a process of using a physical layer ID in a sequence generation process according to the related art, and a physical layer ID generated using a PSS sequence index. Two scrambling sequences And You can see that it is used in the creation process.
  • the OSC is used together with the PSS sequence set in the generation of the scrambling sequence. That is, the scrambling code is generated using a combination of the PSS sequence set and the OCC.
  • Table 4 shows the physical layer IDs defined using both OCC and PSS sequence sets defined for a particular sector. Indicates. Since the scrambling code applied to the SSS is generated using the physical layer ID, the physical layer ID is defined using both the OCC and the PSS sequence set.
  • Table 4 describes the case where the number of repetitions of the synchronization signal is 2 as an example, that is, the case where the OCC is [1 1] or [1 -1].
  • Table 4 six sector indices of 0 to 5 are defined.
  • the PSS sequence set itself is composed of three sequences, two OCCs can be applied to each PSS sequence. Because number occurs.
  • FIGS. 39A and 39B if the synchronization signal is transmitted four times, a total of 12 sector indexes may be generated.
  • Equation 47 When the physical layer ID is defined as shown in Table 4, the sequence generation process described in Equation 47 may be changed as in Equation 48.
  • Equation 48 a process of generating a sequence using a physical layer ID defined according to Table 4 is represented.
  • Equation 48 since the sector index has increased to six in total, it may be confirmed that the value of "+3" in Equation 47 is changed to "+6" in the course of performing a modulo operation.
  • the base station checks the OCC and PSS sequence set defined for a particular sector and finds the sector index of the corresponding sector through a matching relationship as shown in FIG. 35. Then, the base station checks the physical layer ID value matching the sector index, as described in Table 4. Subsequently, the base station determines a scrambling code to be applied to the SSS of the corresponding sector by using the physical layer ID value, and generates the synchronization sequence by applying the determined scrambling code.
  • the UE may estimate the index (ie, PSS sequence set) and OCC of the PSS sequence used for generating the synchronization sequence from the repeatedly received signal. Subsequently, the terminal may determine the scrambling code applied to the SSS according to Table 4 using the estimated PSS sequence set and the OCC. In this process, it is natural that the terminal may classify sectors according to the embodiment described with reference to FIG. 35. The terminal can finally decode the SSS by checking the scrambling code applied to the SSS.
  • FIG. 40 is a view for explaining another PSS / SSS configuration method related to the proposed embodiment.
  • 'E' refers to an empty region in which PSS / SSS is not disposed, and is a resource region that is a blind detection target of a terminal by placing a PBCH (Physical Broadcast Channel) that is not a synchronization signal.
  • PBCH Physical Broadcast Channel
  • the SSS may be allocated on the same time axis and adjacent frequency axis as the resource region in which the PSS is disposed.
  • SSSs between physically adjacent sectors may be allocated to physically different frequency bands. That is, the SSS of sector I of FIG. 40 (a) may be allocated to an adjacent position above the resource region in which the PSS is disposed (for example, in a direction in which the subcarrier index increases), while in FIG. 40 (b) The SSS of sector II may be allocated to an adjacent position below the resource area in which the PSS is disposed (eg, the direction in which the subcarrier index decreases).
  • the PSS and the SSS are adjusted to form the FDM and the resource area, so that the SSS between adjacent sectors can be implemented without affecting each other.
  • the frequency position to which the SSS of each sector is allocated may be determined based on a synchronization parameter (eg, physical layer ID).
  • the embodiment described with reference to FIG. 39 and the embodiment described with reference to FIG. 40 may be combined. That is, when defining the scrambling code applied to the SSS, while using the OCC together with the PSS sequence set of the sector, the SSS of the adjacent sectors may be implemented to be adjacently allocated to different positions in the resource region of the PSS. By using these two methods in combination, the interference effect of the SSS can be more surely eliminated.
  • a configuration of defining different scrambling codes for SSSs of each sector is disclosed.
  • SSSs of two physically adjacent sectors are different from each other.
  • the same scrambling code may be defined in the SSSs of the two sectors when allocated to the frequency domain. This is because the SSSs of the two sectors are allocated to different frequency domains and do not interfere with each other.
  • the base station may apply the OCC to the SSS repeated over a plurality of OFDM symbols. For example, the base station may allocate [1 1 1 1] for sector I of FIG. 39 (a) and [1 1 -1 -1] for sector II of FIG. 39 (b). In this case, the UE can separate the SSS of the two sectors by applying the OCC to the received signal, and can estimate the cell ID group accordingly.
  • a synchronization parameter eg, physical cell ID
  • the base station may apply the OCC to the SSS repeated over a plurality of OFDM symbols. For example, the base station may allocate [1 1 1 1] for sector I of FIG. 39 (a) and [1 1 -1 -1] for sector II of FIG. 39 (b).
  • the UE can separate the SSS of the two sectors by applying the OCC to the received signal, and can estimate the cell ID group accordingly.
  • the scrambling code may be differently applied to the SSS even between adjacent sectors, thereby minimizing the interference between the SSSs.
  • a method of differently implementing an allocated resource region of an SSS or a method of applying an OCC differently to physically different sectors may also be applied.
  • the terminal 100 and the base station 200 may include radio frequency (RF) units 110 and 210, processors 120 and 220, and memories 130 and 230, respectively.
  • RF radio frequency
  • FIG. 41 only a 1: 1 communication environment between the terminal 100 and the base station 200 is illustrated, but a communication environment may be established between a plurality of terminals and a plurality of base stations.
  • the base station 200 illustrated in FIG. 41 may be applied to both the macro cell base station and the small cell base station.
  • Each RF unit 110, 210 may include a transmitter 112, 212 and a receiver 114, 214, respectively.
  • the transmitting unit 112 and the receiving unit 114 of the terminal 100 are configured to transmit and receive signals with the base station 200 and other terminals, and the processor 120 is functionally connected with the transmitting unit 112 and the receiving unit 114.
  • the transmitter 112 and the receiver 114 may be configured to control a process of transmitting and receiving signals with other devices.
  • the processor 120 performs various processes on the signal to be transmitted and transmits the signal to the transmitter 112, and performs the process on the signal received by the receiver 114.
  • the processor 120 may store information included in the exchanged message in the memory 130.
  • the terminal 100 can perform the method of various embodiments of the present invention described above.
  • the transmitter 212 and the receiver 214 of the base station 200 are configured to transmit and receive signals with other base stations and terminals, and the processor 220 is functionally connected to the transmitter 212 and the receiver 214 to transmit the signal. 212 and the receiver 214 may be configured to control the process of transmitting and receiving signals with other devices.
  • the processor 220 may perform various processing on the signal to be transmitted, transmit the signal to the transmitter 212, and may perform processing on the signal received by the receiver 214. If necessary, the processor 220 may store information included in the exchanged message in the memory 230. With such a structure, the base station 200 may perform the method of the various embodiments described above.
  • Processors 120 and 220 of the terminal 100 and the base station 200 respectively instruct (eg, control, coordinate, manage, etc.) the operation in the terminal 100 and the base station 200.
  • Respective processors 120 and 220 may be connected to memories 130 and 230 that store program codes and data.
  • the memories 130 and 230 are coupled to the processors 120 and 220 to store operating systems, applications, and general files.
  • the processor 120 or 220 of the present invention may also be referred to as a controller, a microcontroller, a microprocessor, a microcomputer, or the like.
  • the processors 120 and 220 may be implemented by hardware or firmware, software, or a combination thereof.
  • ASICs application specific integrated circuits
  • DSPs digital signal processors
  • DSPDs digital signal processing devices
  • PLDs programmable logic devices
  • FPGAs Field programmable gate arrays
  • the above-described method may be written as a program executable on a computer, and may be implemented in a general-purpose digital computer which operates the program using a computer readable medium.
  • the structure of the data used in the above-described method can be recorded on the computer-readable medium through various means.
  • Program storage devices that may be used to describe storage devices that include executable computer code for performing the various methods of the present invention should not be understood to include transient objects, such as carrier waves or signals. do.
  • the computer readable medium includes a storage medium such as a magnetic storage medium (eg, a ROM, a floppy disk, a hard disk, etc.), an optical reading medium (eg, a CD-ROM, a DVD, etc.).
  • the method of measuring synchronization parameters as described above may be applied to various wireless communication systems including not only 3GPP LTE and LTE-A systems, but also IEEE 802.16x and 802.11x systems. Furthermore, the proposed method can be applied to mmWave communication system using ultra high frequency band.

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Abstract

L'invention concerne un procédé de transmission de signal de synchronisation et une station de base, le procédé comprenant les étapes suivantes : déterminer un paramètre de synchronisation en utilisant un OCC et un ensemble de séquences de PSS défini pour un secteur, qui est une zone à laquelle un signal de synchronisation doit être transmis ; produire une séquence de brouillage à appliquer à un SSS, en utilisant le paramètre de synchronisation ; produire un SSS à transmettre pour le secteur, en utilisant la séquence de brouillage ; et transmettre répétitivement, sur une pluralité d'intervalles de temps, le SSS et le PSS sélectionnés dans l'ensemble de séquences de PSS.
PCT/KR2017/001483 2016-02-19 2017-02-10 Procédé de transmission de signal de synchronisation utilisant un livre de codes dans un système de communication sans fil WO2017142259A1 (fr)

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