JP2008271302A - Digital signal receiving device and method of controlling frequency of frame synchronization protection thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital signal receiving device capable of controlling the frequency of frame synchronization protection to the number suitable for a moving speed of the receiving device. <P>SOLUTION: The digital signal receiving device has a detection means of detecting a moving speed of the receiving device based on received signals, and a control means of controlling the frequency of frame synchronization protection based on the moving speed of the receiving device. The detection means used computes a phase fluctuation amount between information on propagation paths of two scattered pilots adjacent in the time direction in the same frequency position, and detects a moving speed of the receiving device based on the obtained phase fluctuation amount. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a digital signal receiver and a method for controlling the number of times of frame synchronization protection in a digital signal receiver.

  First, the signal configuration of terrestrial digital broadcasting will be briefly described. FIG. 1 shows a data structure in segment units when viewed from the frequency axis, and FIG. 2 shows a data structure in carrier units when viewed from the frequency side. FIG. 2 shows the frame structure. Further, FIG. 3 is a data structure showing FIG. 2 from another viewpoint.

  In terrestrial digital broadcasting, when considered on the frequency axis, the smaller unit is a carrier, segment, symbol, and frame. For example, in a terrestrial digital broadcasting service (mode 3) that is currently being serviced, there are 1 segment for 432 carriers, 1 symbol for 13 segments (1 symbol for 1 segment in one-segment broadcasting), and 1 frame for 204 symbols. .

  Next, a brief description will be given of backward protection used in determining whether or not frame synchronization has been established and forward protection used in determining whether or not frame synchronization has been lost. As an example, frame synchronization establishment using a synchronization word will be described. When frame synchronization is established by recognizing a synchronization word, frame synchronization is not performed immediately when the synchronization word is detected for the first time. Establish. This is called backward protection. This is to prevent frame synchronization from occurring at an incorrect position.

  Apart from this, after frame synchronization is established, even if the synchronization word cannot be detected at the next position, it is not considered that the frame synchronization has been lost immediately, but the synchronization word cannot be detected several times in succession. Is considered out of frame synchronization. This is called forward protection. This is because even if the synchronization word is not detected, a case where it cannot be detected by chance due to some influence (high-speed fading, pulse noise, etc.) is considered. FIG. 4 is a diagram illustrating frame synchronization establishment when the number of times of backward protection is 2 and the number of times of forward protection is 2. In frame synchronization establishment which is important in the operation of the entire system, frame synchronization establishment with backward and forward protection is usually used.

In general, a certain fixed value that is considered optimal is used as the number of backward and forward protections in frame synchronization. Japanese Patent Laid-Open No. 5-63692 discloses a method of switching the number of forward protections according to the detection state of the synchronization word.
JP 2000-295193 A JP-A-8-307406 JP-A-5-63692

  Establishing frame synchronization is a very important part of the entire receiving system. Depending on whether this synchronization is established, the operation of the receiving system is completely different. By the way, in high-speed mobile reception such as Shinkansen, it is difficult to always find frame synchronization stably under the influence of high-speed fading. In this case, firstly, a method of establishing frame synchronization by applying protection to the frame synchronization once found and utilizing the frame synchronization previously found and its periodicity even if the frame synchronization cannot always be found stably can be considered. The higher the speed, the harder it is to find frame synchronization, so it is a good idea to use a long forward protection count.

  However, in a normal reception environment, it is not a good idea to use a long forward protection count. This is executed when synchronization cannot be established due to a decrease in the reception level, etc., and when the establishment of synchronization cannot be established because the reception system cannot be normally received due to a delay or the reception system as a whole is not operating normally. This is because the reset of the entire system to be delayed is delayed.

  In general, use the fixed number of forward protections that seems to be optimal for all reception environments including high-speed reception, or switch the number of forward protections directly depending on the detection status of frame synchronization. Yes. In the former case, since it is a constant value, there is a high possibility that the optimum number of protection times is not suitable for the reception environment. In the latter case, the number of protections can be switched only after frame synchronization detection is performed directly, so there is a slight contradiction (switching is delayed, switching is not possible until after the actual reception state, etc.) ) Occurs.

  In view of this, the present application proposes a method of making the number of frame synchronization protections variable according to the moving speed (phase fluctuation amount) of the receiver. For example, a long forward protection count is used for high-speed mobile reception, and a shorter forward protection count is used in other environments. In this method, since the number of times of forward protection is switched according to the moving speed of the receiver, there is no contradiction as in the method of switching the number of times of forward protection directly after performing frame synchronization detection.

  It is proposed to detect the moving speed of the receiver by evaluating the magnitude of the phase fluctuation (Doppler frequency). In digital terrestrial broadcasting, a method of obtaining a phase fluctuation amount using channel state information (CSI) of two SPs (scattered pilots: amplitude and phase are known) adjacent in the time direction at the same frequency position is usually used. Conceivable. However, in this case, an accurate phase fluctuation amount cannot be estimated for fluctuations faster than the SP insertion interval. In terrestrial digital broadcasting, SP is inserted every four symbols at the same frequency position. To cope with this, the carrier at the intermediate position between two SPs adjacent in the time direction at the same frequency position is defined as a pseudo SP, and the CSI of the pseudo SP is obtained by diagonal interpolation or frequency direction interpolation. We also propose a method for accurately evaluating even a fast fluctuation by obtaining the phase fluctuation amount using the CSI of the SP and the pseudo SP adjacent to each other.

  An object of the present invention is to provide a digital signal receiver capable of controlling the number of times of frame synchronization protection to a number suitable for the moving speed of the receiver and a method of controlling the number of times of frame synchronization protection in the digital signal receiver.

  Further, the present invention provides a digital signal reception that can accurately detect the moving speed of the receiver even when a fast fluctuation is detected when the moving speed of the receiver is detected based on the propagation path information of the scattered pilot. The purpose is to provide a machine.

  According to the first aspect of the present invention, in the digital signal receiver, detection means for detecting the moving speed of the receiver based on the received signal, and control for controlling the number of times of frame synchronization protection based on the moving speed of the receiver. Means are provided.

  According to a second aspect of the present invention, in the digital signal receiver according to the first aspect, the detecting means calculates the phase fluctuation amount between the propagation path information of two scattered pilots adjacent in the time direction at the same frequency position. The moving speed of the receiver is detected based on the calculated and obtained phase fluctuation amount.

  According to a third aspect of the present invention, in the digital signal receiver according to the first aspect, the detection means detects the carrier at the center position between two scattered pilots adjacent in the time direction at the same frequency position. Defined as a scattered pilot, means for calculating propagation path information for a pseudo-scattered pilot by interpolation, and the phase between the pseudo-scattered pilot adjacent in the time direction at the same frequency position and the propagation information of the scattered pilot. Means is provided for calculating a fluctuation amount and detecting a moving speed of the receiver based on the obtained phase fluctuation amount.

  According to a fourth aspect of the present invention, in the digital signal receiver according to the first to third aspects, when the moving speed of the receiver is larger than a predetermined threshold, the control means sets the number of times of forward protection to a large value, When the moving speed of the receiver is less than a predetermined threshold, the number of times of forward protection is set to a small value.

  According to a fifth aspect of the present invention, in the digital signal receiver according to the first to third aspects, when the moving speed of the receiver is greater than a predetermined threshold, the control means sets the number of times of forward protection to a large value. The number of backward protection is set to a small value, and when the speed of the receiver is less than a predetermined threshold, the number of forward protection is set to a small value and the number of backward protection is set to a large value. .

  According to a sixth aspect of the present invention, in the method for controlling the number of times of frame synchronization protection in a digital signal receiver, the step of detecting the moving speed of the receiver based on the received signal and the frame synchronization based on the moving speed of the receiver A step of controlling the number of times of protection is provided.

  According to a seventh aspect of the present invention, in the digital signal receiver, the phase fluctuation amount calculating means for calculating the phase fluctuation amount between the propagation path information of two scattered pilots adjacent in the time direction at the same frequency position, and the phase Control means for controlling the number of frame synchronization protections based on the phase fluctuation amount calculated by the fluctuation amount calculation means is provided.

  According to the eighth aspect of the present invention, in the digital signal receiver, the carrier at the center position between two scattered pilots adjacent in the time direction at the same frequency position is defined as a pseudo scattered pilot, and the pseudo scattered pilot is defined. Propagation path information interpolating means for calculating propagation path information for the tard pilot by interpolation, and phase fluctuation for calculating the phase fluctuation amount between the pseudo scattered pilot adjacent to the time direction at the same frequency position and the scattered pilot information. And a control unit for controlling the number of times of frame synchronization protection based on the phase fluctuation amount calculated by the amount calculation unit and the phase fluctuation amount calculation unit.

  According to the present invention, the number of frame synchronization protection times can be controlled to a number suitable for the moving speed of the receiver.

  Further, according to the present invention, when the moving speed of the receiver is detected based on the propagation path information of the scattered pilot, the moving speed of the receiver can be accurately detected even for a fast fluctuation. become.

  Embodiments of the present invention will be described below with reference to the drawings.

[1] Configuration of Digital Terrestrial Broadcasting Reception System FIG. 5 shows the configuration of a digital terrestrial broadcast reception system.
An RF (Radio Frequency) signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method is input to the tuner unit 2 via the antenna 1. The RF signal input to the tuner unit 2 is subjected to processing such as amplification, filtering, and frequency conversion, and then output as a baseband (Low-IF) signal. The A / D converter 3 converts an analog signal into a digital signal.

  The Hilbert transform unit 4 generates a Q-axis signal that is 90 degrees out of phase from the input I-axis signal. The narrowband AFC unit 5 performs processing for symbol synchronization, clock synchronization, and frequency synchronization within the carrier interval, and the FFT unit 6 converts the signal on the time axis into a signal on the frequency axis. Then, the broadband AFC unit 7 performs processing for broadband frequency synchronization.

  Thereafter, the frame synchronization and TMCC decoding unit 8 detects the head of the frame, and subsequently performs TMCC (Transmission and Multiplexing Configuration Control) decoding, so what parameters are currently used for the broadcast service? Information (TMCC information) is acquired. The frame synchronization and TMCC decoding unit 8 determines whether or not frame synchronization is established using the frame synchronization protection count (forward protection count and backward protection count). In this embodiment, the number of forward protections is controlled by the equalization unit 9.

  The equalization unit 9 estimates the propagation path information CSI for each carrier based on the SP (Scattered Pilot) signal inserted in the arrangement shown by the black circle in FIG. 9, and based on the propagation path information. Perform equalization processing. That is, the amplitude and phase are detected for each carrier. The data after equalization processing is processed by the frequency deinterleaving unit 10 and the time deinterleaving unit 11 to restore the frequency interleaving and time interleaving performed to reduce the influence of multipath and fading on the transmission side. After being received, it is sent to the demapping unit 12. The equalization unit 9 includes a phase variation evaluation unit 210 (see FIG. 7). The phase fluctuation amount evaluation unit 210 evaluates the phase fluctuation amount (moving speed of the receiver) and controls the number of forward protections used in the frame synchronization and TMCC decoding unit 8.

  The demapping unit 12 obtains the closest reference point of the received data on the constellation and the distance and direction from the reference point. Thereafter, the bit deinterleaving unit 13 performs processing for returning the interleaving in bit units, and then the Viterbi decoding unit 14 performs Viterbi decoding. Next, after receiving a process of returning the interleaving performed in units of bytes by the byte deinterleaving unit 15, the energy spreading unit 16 performs the energy spreading process. Then, RS (Reed Solomon) decoding unit 17 performs RS decoding, which is one of error correction, and outputs it as TS (Transport Stream). Finally, the MPEG decoding unit 18 performs MPEG decoding and H.264 decoding. H.264 decoding is performed, and after being converted into an analog signal by the D / A unit 19, it is output as video or audio information.

[2] Frame synchronization and TMCC decoding unit 18
FIG. 6 shows the configuration of the frame synchronization and TMCC decoding unit 18.

  The DBPSK demodulation unit 101 decodes a TMCC signal that has been subjected to DBPSK (Differential Binary Phase Shift Keying) modulation. The TMCC signal including the synchronization word is DBPSK modulated, and “1” or “0” can be determined by looking at the phase change of the TMCC signal for each symbol at the same frequency position. That is, as shown in FIG. 8, when the difference between the phase of the TMCC signal detected this time and the phase of the TMCC signal of the previous symbol is close to 0 degrees, the TMCC signal detected this time is determined to be “0”. If the phase difference is close to 180 degrees, the TMCC signal detected this time is determined as “1”.

  The TMCC signal majority processing unit 102 determines the value of the TMCC signal for the symbol by taking the majority of the values of a plurality of TMCC signals obtained in the symbol for each symbol.

  Based on the frame synchronization protection frequency switching control signal from the equalization unit 9, the frame synchronization protection frequency setting unit 103 sets the forward protection frequency to either N1 or N2 (N2> N1). In this example, the number of times of backward protection is set to a predetermined constant value.

  The synchronization word detection & protection circuit 104 performs a synchronization word detection process based on the TMCC signal value given from the TMCC signal majority processing unit 102, detects the head position of the frame, and creates a frame pulse. Further, the synchronization word detection & protection circuit 104 uses the detection result of the synchronization word and the number of backward protections and the number of forward protections set in the frame synchronization protection number setting unit 103 to determine whether or not frame synchronization is established. And whether or not the frame synchronization is lost.

  That is, in a state where frame synchronization is not established, the number of times that a synchronization word is continuously detected (number of continuous detections) is counted by a back protection counter (not shown), and this count value is sent to the frame synchronization protection number setting unit 103. When the set number of backward protections is reached, it is determined that frame synchronization has been established. On the other hand, in the state in which frame synchronization is established, the number of times the synchronization word is not continuously detected (number of consecutive non-detections) is counted by a front protection counter (not shown), and this count value is used as the frame synchronization protection number setting unit. When the number of forward protections set to 103 is reached, it is determined that frame synchronization has been lost. A determination result as to whether or not frame synchronization is established is given to the main CPU 110. When the frame synchronization cannot be established over a predetermined period, the main CPU 110 notifies the user that normal reception cannot be performed, or resets the entire system. The determination result of whether or not the frame synchronization is established is that the operation of the predetermined block (for example, the MPEG decoding unit 18) in FIG. 5 is stopped for power saving when the frame synchronization is not established. It may be used for making things.

  A SDSC (Shortened Difference Set Cyclic Code) decoding unit (difference set cyclic decoding unit) 105 performs error correction of the TMCC signal. The SDSC decoding unit 105 performs the majority processing by the TMCC signal majority processing unit 102 when performing error correction of the TMCC signal using the value after the majority processing by the TMCC signal majority processing unit 102 (hard decision error correction). There are cases in which error correction of TMCC signals is performed using a value before being processed (soft decision error correction). The TMCC signal acquisition unit 106 acquires a TMCC signal (TMCC information). The timing adjustment unit 107 adjusts the timing of various pulses, TMCC signals, and data signals.

[3] Equalizer 9
FIG. 7 shows the configuration of the equalization unit 9.

  The SP extraction unit 201 extracts SP from the carrier group shown in FIG. The SP generation unit 202 generates a known SP amplitude and phase corresponding to the SP extracted by the SP extraction unit 201. The complex division unit 203 divides the SP extracted by the SP extraction unit 201 by the SP generated by the SP generation unit 201. Thereby, SP propagation path information CSI (Channel State Information) extracted by the SP extraction unit 201 is obtained.

  The time direction interpolation unit 205 estimates data carrier propagation path information in the time direction (symbol direction). Specifically, the time direction interpolation unit 205 estimates the propagation path information CSI of the data carrier existing between the SPs in the time direction using the propagation path information of the SP existing in every 4 carriers in the time direction. To do. As a result, CSI is obtained for every three carriers in the frequency direction.

  The frequency direction interpolation unit 206 estimates data propagation path information in the frequency direction (carrier direction). Specifically, the frequency direction interpolation unit 206 uses the propagation path information CSI calculated for every 3 carriers in the frequency direction to estimate the propagation path information CSI of the data carrier existing between those carriers. .

  The complex division unit 207 divides the reception data R by the propagation path information H corresponding to the reception data R estimated by the time direction interpolation unit 205 or the frequency direction interpolation unit 206, so that the influence of the propagation path information H can be reduced. The corrected data D is output.

  The phase fluctuation amount evaluation unit 210 outputs a frame synchronization protection frequency switching control signal for switching the number of forward protections based on the magnitude of the phase fluctuation. The operation of the phase variation evaluation unit 210 will be described.

  The phase fluctuation amount evaluation unit 210 uses SP propagation path information CSI of SPs at the same frequency position among SPs indicated by black circles in FIG. 9, that is, SP positions that exist every 4 symbols at the same frequency position. By using the propagation path information CSI, the amount of phase fluctuation (rotation) is evaluated. That is, as shown in FIG. 10, the phase difference between the CSIs of two SPs separated by 4 symbols in the time direction at the same frequency position is obtained.

  Specifically, for any one of two SPs separated by 4 symbols in the time direction at the same frequency position, the complex conjugate of CSI is taken, and the complex conjugate CSI and the CSI that did not take the complex conjugate of Perform complex multiplication between them. Thereby, the amount of phase fluctuation (phase difference) at the frequency position is obtained. The phase fluctuation (rotation) can be both clockwise and counterclockwise, but what is important here is not the rotation direction but the rotation amount.

  By integrating (averaging) the phase fluctuation amount in the symbol direction, it can be obtained more stably. If the integrated value (average value) of the obtained phase fluctuation amounts is less than a certain threshold value, it is determined that the reception environment is normal, and the first frame synchronization protection frequency switching control signal is output. If the integrated value (average value) of the obtained phase fluctuation amounts is equal to or greater than a certain threshold value, it is determined that the environment is a fast fading reception environment, and the second frame synchronization protection frequency switching control signal is output.

  The frame synchronization protection frequency setting unit 103 in FIG. 6 is configured when the frame synchronization protection frequency switching control signal is the first frame synchronization protection frequency switching control signal, that is, when the reception environment is a normal reception environment. The number of times of forward protection is set to a relatively small value N1. When the frame synchronization protection frequency switching control signal is the second frame synchronization protection frequency switching control signal, that is, when the reception environment is a high-speed fading reception environment, the forward protection frequency is set to a relatively large value N2. To do. A certain value is set for the number of times of backward protection.

  As another way of thinking, there can be a method of switching the number of times of backward protection as in the case of switching the number of times of forward protection depending on the reception environment. In this case, since it is difficult to detect a synchronization word in a high-speed fading reception environment, the number of times of backward protection is reduced, and in other reception environments, it is set larger. In other reception environments, it is determined that synchronization has been established when a synchronization word is detected several times periodically so that erroneous synchronization word detection does not occur. Of course, the number of forward protection is switched in the same manner as described above according to the reception environment.

[4] Modified Example of Equalizing Unit 9 The equalizing unit 9 in FIG. 7 obtains a phase variation amount using CSI at the SP position for every four symbols. For this reason, it is possible to accurately evaluate only up to ± 180 degrees of rotation every 4 symbols. Therefore, there is a possibility that accurate evaluation cannot be realized for a more severe phase fluctuation (phase rotation). Therefore, an equalization unit 19 that can evaluate more severe phase fluctuation (phase rotation) is proposed.

  FIG. 11 shows a modification of the equalization unit 9. In the equalization unit 19 of FIG. 11, a pseudo SP information generation unit 204 is provided between the complex division unit 203 and the time direction interpolation unit 205.

  As shown in FIG. 12, the pseudo SP information generation unit 204 sets a central data carrier (indicated by a double circle) between SPs adjacent in the time direction at the same frequency position as a pseudo SP, and propagation path information of the pseudo SP. The CSI is interpolated using the propagation path information CSI of two SPs sandwiching the pseudo SP in an oblique direction. For example, the propagation path information CSI of the G data carrier in FIG. 12 is obtained by interpolating (oblique interpolation) the propagation path information CSI of the B and E SPs. As a result, CSI is obtained for every two carriers in the time direction.

  The pseudo SP propagation path information CSI may be interpolated (frequency direction interpolation) using two SP propagation path information CSI sandwiching the pseudo SP in the frequency direction. For example, the propagation path information CSI of the G data carrier in FIG. 12 may be obtained by interpolating the propagation path information CSI of the A and F SPs.

  The time direction interpolation unit 205 uses the SP and pseudo SP propagation path information that exists for every two carriers in the time direction to obtain the propagation path information CSI of the data carrier that exists between the SP and the pseudo SP in the time direction. presume. As a result, CSI is obtained for every three carriers in the frequency direction.

  The frequency direction interpolation unit 206 estimates data propagation path information in the frequency direction (carrier direction). Specifically, the frequency direction interpolation unit 206 uses the propagation path information CSI calculated for every 3 carriers in the frequency direction to estimate the propagation path information CSI of the data carrier existing between those carriers. .

  The complex division unit 207 divides the reception data R by the propagation path information H corresponding to the reception data R estimated by the time direction interpolation unit 205 or the frequency direction interpolation unit 206, so that the influence of the propagation path information H can be reduced. The corrected data D is output.

  The phase variation evaluation unit 211 performs phase variation (rotation) between propagation path information CSI of SP (indicated by black circles in FIG. 12) and pseudo SP (indicated by double circles in FIG. 12) adjacent in the time direction at the same frequency position. ) Calculate the amount. For example, the amount of phase fluctuation between CSI of D and G in FIG. 12 and the amount of phase fluctuation between CSI of G and C are calculated. The calculated phase fluctuation amount is integrated (averaged) in the symbol direction. If the integrated value (average value) of the obtained phase fluctuation amounts is less than a certain threshold value, it is determined that the reception environment is normal, and the first frame synchronization protection frequency switching control signal is output. If the integrated value (average value) of the obtained phase fluctuation amounts is equal to or greater than a certain threshold value, it is determined that the environment is a fast fading reception environment, and the second frame synchronization protection frequency switching control signal is output.

  Since the equalization unit in FIG. 11 can accurately evaluate the rotation within ± 180 degrees for every two symbols, accurate estimation can be made even for faster phase fluctuation (rotation).

  In the equalization unit of FIG. 11, the time direction interpolation unit 205 uses the SP propagation path information and the pseudo SP propagation path information generated by the pseudo SP information generation unit 204 to perform time direction interpolation processing. However, similar to the time direction interpolation unit in FIG. 7, the time direction interpolation unit 205 uses only SP propagation path information existing in every 4 carriers in the time direction, and between the SPs in the time direction. You may make it estimate the propagation path information CSI of the existing data carrier.

It is a data structure of terrestrial digital broadcasting, Comprising: It is a schematic diagram which shows the data structure of the segment unit at the time of seeing from a frequency axis. It is a data structure of terrestrial digital broadcasting, Comprising: It is a schematic diagram which shows the data structure of the carrier unit at the time of seeing from a frequency axis. It is a data structure of terrestrial digital broadcasting, Comprising: It is a schematic diagram which shows the relationship between a carrier, a segment, a symbol, and a frame. It is a time chart which shows the mode of frame synchronization establishment in the case of the back protection frequency 2 times and the forward protection frequency 2 times. It is a block diagram which shows the structure of a terrestrial digital broadcast receiving system. 3 is a block diagram showing a configuration of frame synchronization and TMCC decoding unit 8. FIG. 3 is a block diagram showing a configuration of an equalization unit 9. FIG. 3 is a schematic diagram for explaining DBPSK demodulation performed by a DBPSK demodulation unit 101. FIG. It is a schematic diagram for demonstrating the equalization process performed by the equalization part 9 of FIG. FIG. 6 is a schematic diagram for explaining the operation of a phase variation evaluation unit 210. FIG. 10 is a block diagram showing a modification of the equalization unit 9. It is a schematic diagram for demonstrating the equalization process performed by the equalization part 9 of FIG.

Explanation of symbols

8 frame synchronization and TMCC decoding unit 9 equalization unit 201 SP extraction unit 202 SP generation unit 203 complex division unit 204 pseudo SP information generation unit 205 time direction interpolation unit 206 frequency direction interpolation unit 207 complex division unit 210, 211 phase fluctuation amount evaluation Part

Claims (8)

Detecting means for detecting the moving speed of the receiver based on the received signal; and control means for controlling the number of times of frame synchronization protection based on the moving speed of the receiver;
A digital signal receiver comprising: The detection means calculates a phase fluctuation amount between propagation path information of two scattered pilots adjacent in the time direction at the same frequency position, and detects a moving speed of the receiver based on the obtained phase fluctuation amount. The digital signal receiver according to claim 1, wherein: The detection means is
Means for calculating a carrier at a central position between two scattered pilots adjacent in the time direction at the same frequency position as a pseudo-scattered pilot, and calculating propagation path information for the pseudo-scattered pilot by interpolation, and the same Means for calculating the phase fluctuation amount between the propagation information of the pseudo-scattered pilot and the scattered pilot adjacent in the time direction at the frequency position, and detecting the moving speed of the receiver based on the obtained phase fluctuation amount;
The digital signal receiver according to claim 1, further comprising: The control means sets the forward protection count to a large value when the moving speed of the receiver is larger than a predetermined threshold, and sets the forward protection count to a small value when the moving speed of the receiver is less than the predetermined threshold. 4. The digital signal receiver according to claim 1, wherein the digital signal receiver is one. When the moving speed of the receiver is greater than a predetermined threshold, the control means sets the number of forward protections to a large value and the number of backward protections to a small value, and when the speed of the receiver is less than the predetermined threshold, 4. The digital signal receiver according to claim 1, wherein the number of forward protection is set to a small value and the number of backward protection is set to a large value. Detecting the moving speed of the receiver based on the received signal, and controlling the frame synchronization protection frequency based on the moving speed of the receiver;
A method for controlling the number of times of frame synchronization protection in a digital signal receiver. Based on the phase fluctuation amount calculating means for calculating the phase fluctuation amount between the propagation path information of two scattered pilots adjacent in the time direction at the same frequency position, and the phase fluctuation amount calculated by the phase fluctuation amount calculating means, Control means for controlling the number of times of frame synchronization protection;
A digital signal receiver comprising: A carrier at the center position between two scattered pilots adjacent in the time direction at the same frequency position is defined as a pseudo-scattered pilot, and propagation path information interpolation for calculating propagation path information for the pseudo-scattered pilot by interpolation means,
Phase fluctuation amount calculating means for calculating phase fluctuation amount between propagation information of pseudo scattered pilot and scattered pilot adjacent in time direction at the same frequency position, and phase fluctuation amount calculated by phase fluctuation amount calculating means Control means for controlling the number of times of frame synchronization protection based on
A digital signal receiver comprising:

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