WO2017030302A1 - Procédé de transmission/réception de signal de synchronisation au moyen d'un livre de codes dans un système de communications sans fil - Google Patents

Procédé de transmission/réception de signal de synchronisation au moyen d'un livre de codes dans un système de communications sans fil Download PDF

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WO2017030302A1
WO2017030302A1 PCT/KR2016/008365 KR2016008365W WO2017030302A1 WO 2017030302 A1 WO2017030302 A1 WO 2017030302A1 KR 2016008365 W KR2016008365 W KR 2016008365W WO 2017030302 A1 WO2017030302 A1 WO 2017030302A1
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synchronization signal
precoder
precoders
base station
terminal
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PCT/KR2016/008365
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English (en)
Korean (ko)
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이길봄
강지원
김기태
박경민
김희진
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엘지전자 주식회사
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes

Definitions

  • the following description relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting and receiving a sync signal using a codebook and a codebook applied to a sync 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, and an object of the present invention is to efficiently design a precoder applied to a synchronization signal transmitted by base stations in a wireless communication system.
  • Another object of the present invention is to ensure the diversity of the synchronization signal to enable stable transmission and reception of the synchronization signal.
  • Another object of the present invention is to uniformly ensure the diversity gain of the synchronization signal without additional signaling overhead.
  • a synchronization signal transmission method including: defining a codebook including a plurality of third precoders defined as a weighted sum of a plurality of second precoders; Transmitting a first synchronization signal to which the third precoder of the second precoder is applied to the terminal in the first time interval, and transmitting a second synchronization signal to which the other third precoder selected from the codebook is applied to the terminal in the second time interval.
  • a first synchronization signal is used in the synchronization process of the terminal together with the second synchronization signal, and each of the plurality of second precoders is defined as a weighted sum of the plurality of first precoders.
  • the first precoders constituting the two precoders are configured such that the corresponding beams do not neighbor each other and the minimum distance between the beams is the same.
  • the codebook is shared between the base station and the terminal, and the number of second precoders constituting the codebook may be equal to the number of repetitions of the base station transmitting a synchronization signal.
  • the weighted sum of the plurality of first precoders is obtained by multiplying each of the plurality of first precoders by any one of 1 * a1, -1 * a2, j * a3, and -j * a4, and a1, a2, a3 and a4 may be any constant.
  • the plurality of second precoders may be configured such that an area corresponding to one second precoder is shifted from an area corresponding to another second precoder.
  • the third precoder applied to the second synchronization signal may be any one selected from among a plurality of third precoders constituting the codebook except for the third precoder applied to the first synchronization signal.
  • Synchronization may be performed by the terminal synchronizing timing with the base station and estimating the sequence used for the first synchronization signal and the second synchronization signal.
  • the plurality of first precoders constituting any one second precoder may be configured to uniformly divide an area corresponding to any one second precoder.
  • the area of the first precoder constituting one second precoder is the first precoder constituting the other second precoder. It may not overlap with the area of the coder.
  • the base station for solving the technical problem includes a transmitter, a receiver, and a processor operating in connection with the transmitter and the receiver, the processor, a plurality of third precoder defined by the weighted sum of the plurality of second precoder Define a codebook consisting of the first, the first synchronization signal to which any one third precoder selected from the codebook is applied to the terminal in a first time interval, the second synchronization to which the other third precoder selected from the codebook is applied
  • the signal is transmitted to the terminal in a second time interval, and the first synchronization signal is used in the synchronization process of the terminal together with the second synchronization signal, and each of the plurality of second precoders is a weighted sum of the plurality of first precoders.
  • the first precoders constituting any one second precoder are defined such that the corresponding beams are not adjacent to each other and the minimum distance between the beams is the same. .
  • a process of transmitting and receiving a synchronization signal between a base station and a terminal is improved, thereby improving stability of a communication link.
  • 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.
  • FIG. 18 is a flowchart illustrating a synchronization signal transmission and reception method according to another embodiment.
  • 19 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 shown differently by subcarrier spacing, and in general, even if the 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 ⁇ 0.05ppm ⁇ 0.1ppm ⁇ 10 ppm ⁇ 20ppm 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. The following description is based on the assumption that ⁇ is zero.
  • 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 is mainly used which represents a geometric mean between the equation for Doppler variance and the equation for coherence time.
  • 1 is a diagram illustrating a Doppler spectrum.
  • the Doppler spectrum or Doppler power spectrum density, which represents a change in 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.
  • N g , i represent the length of an OFDM symbol, the length of a cyclic prefix (CP), and the index of an OFDM symbol, respectively.
  • 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.
  • each of the basic 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. Is 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 a reception SNR when simply transmitting a synchronization signal repeatedly, and SNR proposed represents a reception SNR when the synchronization signal is transmitted by configuring a precoder to obtain diversity according to the proposed embodiment.
  • the former doubles the receive power of the sync signal, while the latter receives two channels. And It is expressed as if And If is independent of each other, the diversity gain of the SNR proposed becomes 2.
  • 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 on 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.
  • Equation (23) Looking at the sign of, it can be seen that the phase of the synchronization signal is inverted with respect to some region in the subsector in the second time interval.
  • 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.
  • FIG. 19 is a diagram illustrating a configuration of a terminal and a base station according to an embodiment of the present invention.
  • 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.
  • FIG. 19 illustrates only a 1: 1 communication environment between the terminal 100 and the base station 200, a communication environment may also be established between a plurality of terminals and a plurality of base stations.
  • the base station 200 illustrated in FIG. 19 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 synchronization signal transmission / reception method 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 de transmission de signal de synchronisation selon l'invention comprend les étapes suivantes : un livre de code, contenant une pluralité de troisièmes précodeurs définis par les sommes pondérées d'une pluralité de deuxièmes précodeurs, est défini; un premier signal de synchronisation auquel est appliqué un troisième précodeur sélectionné dans le livre de codes, est transmis à un terminal durant un premier intervalle de temps; et un second signal de synchronisation auquel est appliqué un troisième précodeur différent sélectionné dans le livre de codes, est transmis au terminal durant un second intervalle de temps. Le premier signal de synchronisation et le second signal de synchronisation sont utilisés dans la synchronisation avec la station de base. Chacun de la pluralité de deuxièmes précodeurs est défini par les sommes pondérées d'une pluralité de premiers précodeurs. Et, dans les premiers précodeurs contenus dans l'un quelconque des deuxièmes précodeurs, des faisceaux correspondants ne sont pas adjacents les uns aux autres et les distances minimales entre les faisceaux sont égales.
PCT/KR2016/008365 2015-08-17 2016-07-29 Procédé de transmission/réception de signal de synchronisation au moyen d'un livre de codes dans un système de communications sans fil WO2017030302A1 (fr)

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WO2021223227A1 (fr) * 2020-05-08 2021-11-11 北京小米移动软件有限公司 Procédé et appareil de transmission de signal de synchronisation ainsi que dispositif et support d'informations lisible

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