JP2010268136A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving device which reduces power consumption, according to signal reception condition. <P>SOLUTION: The receiving device for receiving a modulated symbol signal includes a synchronization acquisition section for detecting a start position of the symbol signal, with in a prescribed synchronization acquisition processing time; a demodulation section for demodulating the symbol signal detected by the synchronization acquisition section and calculating a modulation error rate of the symbol signal; and a control section for setting the synchronization acquisition processing time, according to the modulation error rate calculated by the demodulation section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a receiving apparatus that receives a signal.

  One of signal transmission / reception methods is time division multiplexing (TDM). The TDM scheme is a multiplexing scheme in which a plurality of channel signals are time-divided, the time-divided channel signals are arranged in a time-shifted manner, and the arranged signals are transmitted in a certain frequency band. The TDM system is used for DVB-H (Digital Video Broadcasting-Handheld) and MediaFLO (Media Forward Link Only), which are terrestrial digital broadcasting standards for mobile terminals.

  A receiving apparatus that receives a signal selects a signal of one channel among time-division multiplexed signals composed of a plurality of channels transmitted from the transmitting apparatus. The receiving device does not need to process the signal of another channel that has not been selected. However, even if the receiving signal is not being processed, the receiving device is in the idling state when the power is turned on. Consume. A receiving device used for a portable terminal is required to reduce power consumption in order to extend a standby time. In order to extend the standby time by suppressing power consumption in the receiving apparatus, the receiving apparatus is turned off in the standby state. Then, when it is time to receive the next time division signal of the selected channel, the receiving apparatus is turned on.

  The receiver must set up a demodulator that demodulates the received signal and an error corrector that corrects the error in the received signal before the receiver receives the next time-division signal from the power-off state. is there. There is a fixed value recommended as the time required for setup according to the broadcast standard, etc., for the start timing of the demodulation unit and error correction unit, and the receiving device determines whether the demodulation unit and error correction unit before receiving processing according to the fixed value. Start booting.

  If the signal reception conditions change, the fixed value set in the receiving apparatus may be too long. For example, when receiving a signal while the mobile terminal is stationary, or when the quality of the received signal is high because the distance between the transmitting device and the receiving device is short, the signal is received in a shorter time than the fixed value recommended by the broadcast standard. In some cases, the startup process before processing can be terminated. Even in such a case, starting up with a fixed value uniformly contributes to increasing the power consumption of the mobile terminal. The following patent documents disclose techniques related to a receiving apparatus that receives time division multiplexed signals.

JP 2006-229671 A Japanese Patent Application No. 2005-516321

  An object of an embodiment of the present invention is to provide a receiving apparatus that suppresses power consumption according to a signal reception state.

  In order to solve the above problems, a receiving apparatus that receives a modulated symbol signal includes a synchronization acquisition unit that detects a start position of the symbol signal at a predetermined synchronization acquisition processing time, and the symbol detected by the synchronization supplement unit. A demodulator that demodulates the signal and calculates a modulation error rate of the symbol signal; and a controller that sets the synchronization acquisition processing time according to the modulation error rate calculated by the demodulator.

  According to the embodiment, it is possible to provide a receiving device that suppresses power consumption according to a signal reception state.

It is a block diagram of a receiver. It is a table for calculating synchronous acquisition processing time from the value of MER. It is a flowchart figure showing operation | movement of a receiver. It is a timing chart figure showing starting timing of a receiving device. It is a block diagram of a receiver. It is a table for calculating synchronous acquisition processing time from the value of BER. It is a flowchart figure showing operation | movement of a receiver. It is a block diagram of a receiver. It is a flowchart figure showing operation | movement of a receiver. It is a block diagram of a receiver. It is a detailed block diagram of a processing time calculation unit. It is a table for calculating a BER prediction value from a CNR value. It is a table for calculating a correction amount from an error amount ratio. It is an operation | movement flowchart figure of a processing time calculation part. It is a block diagram of a receiver. It is a detailed block diagram of a gain adjustment part. It is a table for calculating amplification adjustment time from movement speed.

  Hereinafter, this embodiment will be described. The following embodiments can also be realized by processing a program by a processor. Combinations of configurations in the embodiments are also included in the embodiments of the present invention.

  FIG. 1 is a block diagram showing an example of the configuration of the receiving apparatus 1 according to the present embodiment. The receiving device 1 is activated when receiving the selected data among the time-division multiplexed data. The reception device 1 includes a reception antenna 5, an amplification unit 10, a synchronization acquisition unit 11, a gain adjustment unit 12, a demodulation unit 13, an error correction unit 15, an access control unit 16, and a control unit 2.

  The receiving antenna 5 amplifies the selected channel signal among the received signals received. The channel signal is a signal obtained by superimposing digital information on a modulated wave in the GHz band by a phase change or the like. The amplifier 10 converts the frequency of the received channel signal from the GHz band to the MHz band.

  The signal strength of the channel signal varies depending on the distance from the transmission device and the reception environment of the reception device 1. In order to prevent time fluctuation of the signal strength of the channel signal and perform stable demodulation processing, the amplification unit 10 amplifies the channel signal after frequency conversion so that the signal strength of the signal output to the synchronization acquisition unit 11 is constant. To do.

  One channel signal has a plurality of OFDM symbol signals having the same period. Here, OFDM (Orthogonal Frequency Division Multiplexing) is a method of transmitting data using modulated waves having a plurality of different frequencies that do not interfere with each other in order to send a plurality of information simultaneously. An OFDM symbol signal is a symbol signal that has been subjected to orthogonal wave frequency division multiplexing. The OFDM symbol signal is modulated by a QAM (Quadrature Amplitude Modulation) modulation method or the like.

  A signal of a certain length called a guard interval is inserted between the OFDM symbol signals. The guard interval is the same signal as the last part of the subsequent OFDM symbol signal.

  The synchronization acquisition unit 11 performs symbol timing synchronization acquisition processing of the OFDM symbol signal on the channel signal amplified by the amplification unit 10 based on the guard interval included in the OFDM symbol signal. The synchronization acquisition unit 11 executes a synchronization acquisition process for detecting a leading position of the OFDM symbol signal for a predetermined time. Details of the synchronization acquisition process by the synchronization acquisition unit 11 will be described below.

  The synchronization acquisition unit 11 performs an autocorrelation calculation process between an OFDM symbol signal and a guard interval corresponding to the OFDM symbol signal. The synchronization acquisition unit 11 selects a signal in a certain interval as the signal A. Further, the synchronization acquisition unit 11 selects a signal in a certain section as a signal B from a time delayed by one period of the OFDM symbol signal from that section. The synchronization acquisition unit 11 calculates the autocorrelation between the signal A and the signal B.

  In order to calculate the autocorrelation, the synchronization acquisition unit 11 samples the signal A and the signal B at regular intervals. The synchronization acquisition unit 11 integrates the amplitudes of the sampled signals A and B, and calculates the sum of the integrated values in the sampling range as an autocorrelation. An OFDM symbol signal is close to white noise that varies evenly in positive or negative. Therefore, since the integrated value of the guard interval and the other than the latter half of the OFDM symbol signal is a mixture of positive or negative values, the autocorrelation that is the sum is small. On the other hand, when the signal A is a guard interval and the signal B is the latter half of the FDM symbol signal corresponding to the guard interval, the integration of the signal A and the signal B is positive values or negative values, and the integration result is always Become positive. Therefore, the autocorrelation that is the sum of the integrated values is increased. The synchronization acquisition unit 11 calculates a moving average characteristic with the horizontal axis as the shift time and the vertical axis as the autocorrelation value while shifting the selected section as the signal A little by little in time. As a result, it is possible to obtain a moving average characteristic having an autocorrelation value peak at a certain point with respect to the shift time.

  The synchronization acquisition unit 11 can specify the phase shift amount of the OFDM symbol signal from the shift time when the autocorrelation value has a peak. By specifying the phase shift amount of the OFDM symbol signal, the synchronization acquisition unit 11 can detect the start position of the OFDM symbol signal and perform the synchronization acquisition process. A highly accurate demodulation process can be performed by performing the synchronous acquisition process on the OFDM symbol signal. The synchronization acquisition unit 11 transmits the OFDM symbol signal after the synchronization acquisition process to the demodulation unit 13.

  When the signal reception conditions are good, the synchronization acquisition unit 11 can accurately perform synchronization acquisition processing using one OFDM symbol signal as described above. However, when the signal reception conditions are poor and noise is superimposed on the received signal, the waveform shape of the latter half of the OFDM symbol signal corresponding to the guard interval and the guard interval is not the same, so the calculated autocorrelation value is small. Become. As a result, the peak value of the moving average characteristic in the time direction becomes so small that it cannot be detected. What is necessary is just to raise the SN ratio of a peak value in order to raise the detection accuracy of a peak value. By performing the above processing on a plurality of OFDM symbol signals, the SN ratio of the peak value can be increased.

  As the number of autocorrelation calculation processes for the OFDM symbol signal increases, the time required for the synchronization acquisition process in the synchronization acquisition unit 11 increases. Therefore, when the signal reception condition deteriorates, it is necessary to ensure a long processing time of the synchronization acquisition unit 11 accordingly.

  The gain adjustment unit 12 adjusts the voltage amplification gain of the amplification unit 10 based on the voltage amplitude of the channel signal input to the synchronization acquisition unit 11 so that the voltage amplitude of the channel signal output from the amplification unit 10 is constant. . The synchronization acquisition unit 11 outputs information on the voltage amplitude value to the gain adjustment unit 12. When the fluctuation of the voltage amplitude of the received signal is large due to the movement of the receiving device 1 or the like, an amplification processing time is required to keep the intensity of the channel signal input to the synchronization acquisition unit 11 constant. Further, in order to prevent the amplification unit 10 from oscillating due to abrupt gain adjustment, the gain adjustment unit 12 changes the gain of the amplification unit 10 with a constant time constant. Therefore, when the change in the signal reception condition is large, it is necessary to ensure a long processing time for the gain adjusting unit 12 and the amplifying unit 10 accordingly.

  The demodulator 13 demodulates the channel signal that has been subjected to synchronization correction by the synchronization acquisition unit. The demodulator 13 has a MER calculator 14. The MER calculation unit 14 calculates MER 20 that is an average value of a modulation error ratio (MER) at the time of demodulation of the received signal, and transmits the MER 20 to the processing time calculation unit 17. The MER is an average value of the amount of deviation between the constellation of data obtained by demodulating the OFDM symbol signal and the ideal constellation on the transmission side, and represents the magnitude of variation in received data. The constellation refers to a plot of signals of each frequency component on the XY coordinates with the in-phase component of the demodulated data as the X axis and the direct component as the Y axis. Details of the calculation of MER will be described later. A large variation means that the signal reception condition is bad. If the reception condition is deteriorated, the time required for synchronous acquisition becomes longer as described above. As a result, the processing time of the received signal in the synchronization acquisition unit 11 becomes long.

  The control unit 2 sets a time for executing the synchronization acquisition process by the synchronization acquisition unit 11 according to the MER 20 calculated by the MER calculation unit 14. The control unit 2 includes an activation control unit 18 and a processing time calculation unit 17. The processing time calculation unit 17 has a table 50. The processing time calculation unit 17 refers to the table 50 based on the received MER 20, and calculates the optimum synchronization acquisition processing time 26 for the synchronization acquisition unit 11 to process the channel signal. The processing time calculation unit 17 transmits the calculated synchronization acquisition processing time 26 to the activation control unit 18.

  The access control unit 16 transmits the digital signal after the error correction processing to a processing device (not shown) that processes the digital signal. The access control unit 16 also reads the reception time information 19 that is the scheduled reception time of the next channel signal from the channel signal being processed, and transmits it to the activation control unit 18.

  Based on the received reception time information 19 and the synchronization acquisition processing time 26, the activation control unit 18 sends activation control signals 21, 22, to the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15. 23, 24 and 25 are transmitted. The timing for transmitting the activation control signal varies depending on the synchronization acquisition processing time 26 received by the activation control unit 18. The activation start time of the synchronization acquisition unit 11 can be optimized by changing the activation start time of the synchronization acquisition unit 11 based on the MER 20.

  FIG. 2 is a table 50 for calculating the synchronization acquisition processing time 26 from the value of the MER 20. A column 55 is a value obtained by converting the value of the MER 20 input to the processing time calculation unit 17 into a carrier noise ratio (Carrier Noise Ratio: CNR). When the modulation method is determined, MER and CNR have a one-to-one correspondence. The conversion ratio between MER and CNR is calculated in advance and stored in the processing time calculation unit 17. The processing time calculation unit 17 converts the input MER20 value into a CNR. Here, the CNR is a ratio between the power of the carrier wave of the signal and the power of noise, and the signal quality is better as the CNR is larger.

  The required CNR value necessary for correctly receiving a signal is uniquely determined by the signal standard and the signal decoding method. For example, the required CNR in the DVB-H standard configured by Viterbi decoding and Reed-Solomon decoding is about 14 dB in 16 QAM (Quadrature Amplitude Modulation). Here, 16QAM is one of digital modulation schemes, and uses four types of phases and amplitudes respectively, and transmits / receives data by combining them. Assuming that the amount of noise is very large, 14.5 dB, which is a value obtained by adding 0.5 dB to the required CNR, is set, and the CNR determination value is increased in increments of 0.5 dB.

  Column 56 is the synchronization acquisition processing time corresponding to the converted CNR. The maximum value of the synchronization acquisition processing time is determined by the guidelines of each communication standard. In the row 52, when the CNR is smaller than 14.5 dB, the synchronization acquisition processing time is 50 ms. Here, 50 ms is the maximum value of the synchronization acquisition processing time of the synchronization acquisition unit 11 defined in the DVB-H standard implementation guidelines. Further, when the CNR is 15 dB or more in the row 54, it is determined that the amount of noise is very small, and 2 ms, which is a 2 OFDM symbol long time of the DVB-H standard, is set. Further, when the CNR is 14.5 dB or more and smaller than 15 dB in the row 53, the synchronization acquisition processing time is set to 25 ms which is an intermediate value between the maximum value 50 ms and the minimum value 2 ms.

  As described above, the activation start time of the synchronization acquisition unit 11 can be optimized by setting the synchronization acquisition processing time based on the value of the MER20. By optimizing the activation start time, the synchronization acquisition processing time can be shortened from 50 ms defined in the standard to 2 ms which is the minimum value depending on reception conditions. By shortening the synchronization acquisition processing time, the activation start time of the amplification unit 10, the gain adjustment unit 12, and the synchronization acquisition unit 11 is delayed, and the power consumption generated by the amplification processing, gain adjustment processing, and synchronization acquisition processing can be suppressed. I can do it.

  In this embodiment, the synchronization acquisition processing time is set using the CNR converted from the MER as an index. However, the MER may be used as it is, or the synchronization acquisition processing time may be set using another index.

  FIG. 3 is a flowchart showing the operation of the receiving device 1. The activation control unit 18 turns on the operations of the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15 of the receiving device 1 (S10). The receiving antenna 5 receives the channel signal (S11). The amplifying unit 10 converts the frequency band of the channel signal received by the receiving antenna 5 into the MHz band and amplifies it to a predetermined amplitude (S12). The synchronization acquisition unit 11 performs a synchronization acquisition process on the amplified channel signal (S13). The demodulator 13 demodulates the channel signal after the synchronization acquisition process (S14). The demodulator 13 acquires a constellation for each frequency component of the demodulated channel signal (S15). The demodulator 13 in FIG. 1 has a MER calculator 14. The MER calculation unit 14 calculates the difference on the XY coordinate between the acquired constellation of each frequency component and its ideal value (S16). The better the transmission quality, the closer the constellation of each frequency component is to the ideal value. Therefore, the transmission quality can be evaluated by evaluating the MER.

  The MER calculation unit 14 calculates a cumulative value of difference values on the XY coordinates between the acquired constellation of each frequency component and its ideal value (S17). The MER calculation unit 14 calculates an average value of the calculated cumulative values (S18). The error occurrence rate of the received signal calculated based on the average value of the calculated cumulative values is defined as MER20.

  When the activation control unit 18 does not perform the off control (S19, NO), the receiving device 1 repeats the processing from step S10. When the activation control unit 18 performs off control (S19, YES), the activation control unit 18 turns off the operations of the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15 ( S20).

  The access control unit 16 acquires reception time information 19 indicating when the time division signal of the selected channel is received from the currently received signal (S21). The processing time calculation unit 17 acquires MER20, which is an average value of MER, from the MER calculation unit 14 (S22). The processing time calculation unit 17 determines the synchronization acquisition processing time 26 corresponding to the acquired MER 20 by referring to the table 50 (S23). The activation control unit 18 calculates a reception start time that is the activation timing of the synchronization capturing unit 11 based on the reception time information 19 transmitted from the access control unit 16 and the synchronization acquisition processing time 26 transmitted from the processing time calculation unit 17. Set (S24). The activation control unit 18 starts measuring the elapsed time after the off control using a timer or the like (S25). When the measured elapsed time is smaller than the reception start time set in the activation control unit 18 (S26, NO), the activation control unit 18 continues to measure the elapsed time. When the measured elapsed time is equal to or greater than the reception start time (S26, YES), the activation control unit 18 turns on the operations of the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15. (S10), the process from step S11 is executed again.

  By executing the above steps and setting the synchronization acquisition processing time based on the value of MER20, the activation start time of the synchronization acquisition unit 11 can be optimized and the power consumption can be suppressed.

  FIG. 4 is a timing chart showing the activation timing of the receiving apparatus until the next signal is received. Each component of the receiving apparatus 1 is turned on in the order of the amplification unit 10, the gain adjustment unit 12, the synchronization acquisition unit 11, the demodulation unit 13, and the error correction unit 15. The time from when the amplifying unit 10 is turned on until the signal amplification processing is completed is defined as a signal amplification processing time 60. The time from when the gain adjustment unit 12 is turned on until the gain adjustment processing is completed is defined as gain adjustment processing time 61. The time from when the demodulator 13 is turned on until the demodulation process is completed is defined as a demodulation processing time 63. The time from when the error correction unit 15 is turned on until the error correction processing is completed is defined as an error correction processing time 64.

  In the present embodiment, the value of the synchronization acquisition processing time 26 is optimized by the value of the MER 20 output from the MER calculation unit 14 of the demodulation unit 13. By optimizing the synchronization acquisition processing time 26, it is possible to optimize the start-up time of the receiving device 1 before the start of signal reception and to suppress power consumption.

  FIG. 5 is a block diagram of a receiving device 1a according to another embodiment. The reception device 1a includes a reception antenna 5, an amplification unit 10, a synchronization acquisition unit 11, a gain adjustment unit 12, a demodulation unit 13, an error correction unit 15, an access control unit 16, and a control unit 2a. The same members as those of the receiving apparatus 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The demodulated OFDM symbol signal includes CRC (Cyclic Redundancy Check) data for detecting an error and ECC (Error Correcting Code) data for correcting the error. CRC is a test method in which data is divided by a specific mathematical expression in units of blocks, CRC data that is redundant bits is added so that the data can be divided, and at the time of inspection, the data is divided by a specific mathematical expression for checking. The error correction unit 15 can detect whether or not a bit error has occurred in units of blocks by CRC. ECC is error correction processing in which ECC data for correcting an error for each bit is added to data, and when a bit error is detected, the bit error is corrected. Examples of error correction methods include convolutional codes, Reed-Solomon codes, and turbo codes. The error correction unit 15 can detect and correct errors in units of bits by ECC.

  The error correction unit 15 has an error counter 71 for counting the number of detected bit errors. When an error is detected by CRC or ECC, the error counter 71 counts the number of errors per a certain number of bits or a certain number of packets included in the OFDM symbol signal demodulated by the demodulator 13. After counting the number of error occurrences per fixed data length such as a fixed number of bits or a fixed number of packets, the error correction unit 15 divides the number of errors counted by the error counter 71 by the number of bits or packets having a fixed data length. Then, an error rate such as a bit error rate (BER) or a packet error rate (PER) is calculated. Here, BER is the ratio of the number of error bits to the total number of bits of the OFDM symbol signal, and PER is the ratio of the number of error packets to the total number of packets of the OFDM symbol signal. An error rate calculated based on the number of bit errors generated by the demodulation process is called a demodulation error rate.

  The values of BER and PER change in the same manner as the MER described above depending on the reception conditions of the reception device 1a. The value of the MER increases as the phase and amplitude of the modulated wave in the OFDM symbol signal deviates from the ideal value. Inability to correctly demodulate means that the error rate BER or PER increases. That is, as MER increases, BER and PER increase as well. Therefore, it can be said that the phase and amplitude of the modulated wave in the OFDM symbol signal deviate from ideal values as BER and PER increase.

When the phase and amplitude of the modulated wave in the OFDM symbol signal deviate from the ideal values, as described above, the autocorrelation between the guard interval in the synchronization acquisition process and the latter half of the OFDM symbol signal becomes small. Therefore, the synchronization acquisition processing time 26 of the synchronization acquisition unit 11 can be optimized using BER and PER by the same technique as that used to optimize the synchronization acquisition processing time 26 of the synchronization acquisition unit 11 using MER.
The calculation of BER and PER may be performed by an arithmetic device provided outside the error correction unit 15. The error correction unit 15 transmits the calculated error rate information 70 such as BER and PER to the control unit 2a.

  The control unit 2a includes a processing time calculation unit 17a and an activation control unit 18. The processing time calculation unit 17 a calculates the synchronization acquisition processing time 26 of the synchronization acquisition unit 11 from the received error rate information 70 and transmits it to the activation control unit 18. Details of the method of calculating the synchronization acquisition processing time 26 will be described later.

  The activation control unit 18 transmits an activation control signal to the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15 based on the received reception time information 19 and the synchronization acquisition processing time 26. The timing for transmitting the activation control signal differs depending on the received synchronization acquisition processing time 26. By changing the activation start time of the synchronization acquisition unit 11 based on the error rate information 70, the activation start time of the synchronization acquisition unit 11 can be optimized, and the power consumption of the receiving device 1a can be optimized.

  FIG. 6 is a table 80 for calculating the synchronization acquisition processing time 26 from the BER value. The table 80 is stored in the processing time calculation unit 17a. Column 85 is the input BER value. The evaluation value of the received signal before the error correction by the error correction unit 15 is determined by the correction capability of the error correction method employed in the error correction unit 15. For example, in the DVB-H standard, the error correction unit 15 decodes a signal by connecting a Viterbi decoding method and a Reed-Solomon decoding method. If the BER after Viterbi decoding is smaller than 2 × 10E-4, it is determined that there is no error in the signal after Reed-Solomon decoding. The error correction unit 15 is configured to count the error amount of the signal after Viterbi decoding by the error counter 71 and output the calculated BER 70.

  In the table 80, 1.5 × 10E-4 obtained by subtracting 0.5 × 10E-4 from 2 × 10E-4 as a row 82 is set as a determination value when the amount of noise is very large. The judgment value is set to be small in increments of 1.0 × 10E-4.

  Column 86 is a synchronization acquisition processing time corresponding to the BER value in column 85. The maximum value of the synchronization acquisition processing time is defined by guidelines for each standard. In the row 82, when the BER is larger than 1.5 × 10E-4, the synchronization acquisition processing time is 50 ms. Here, 50 ms is the maximum value of the synchronization acquisition processing time of the synchronization acquisition unit 11 defined in the DVB-H standard implementation guidelines. If the BER is 0.5 × 10E−4 or less in the row 84, it is determined that the amount of noise is very small, and 2 ms, which is a 2 OFDM symbol long time of the DVB-H standard, is set. Further, when the BER is larger than 0.5 × 10E-4 and not more than 1.5 × 10E-4 in the row 83, an intermediate value 25 ms between the maximum value 50 ms and the minimum value 2 ms is set as the synchronization acquisition processing time.

  By setting the synchronization acquisition processing time based on the BER value, the activation start time of the synchronization acquisition unit 11 can be optimized.

  FIG. 7 is a flowchart showing the operation of the receiving apparatus 1a. Since the processing from step S30 to step S34 is the same as the processing from step S10 to step S14, the description thereof is omitted.

  The error correction unit 15 holds the received data before error correction in a memory or the like provided in the error correction unit 15 (S35). The error correction unit 15 executes error correction processing on the held data (S36). The error counter 71 provided in the error correction unit 15 acquires the difference between the data before error correction and the data after error correction (S37). The error counter 71 calculates the cumulative value of the difference values (S38). The error correction unit 15 calculates error rate information 70 such as BER and PER based on the calculated cumulative value (S39).

  When the activation control unit 18 does not perform off control (S40, NO), the receiving device 1a repeats the processing from step S30. When the activation control unit 18 performs off control (S40, YES), the activation control unit 18 turns off the operations of the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15 ( S41).

  The access control unit 16 acquires the reception time information 19 indicating when the time division signal of the selected channel is received from the currently received signal (S42). The processing time calculation unit 17a acquires the error rate information 70 from the error correction unit 15 (S43). The processing time calculation unit 17a refers to the table 80 to determine the synchronization acquisition processing time 26 corresponding to the acquired error rate information 70 (S44). The activation control unit 18 calculates a reception start time that is an activation timing of the synchronization capturing unit 11 based on the reception time information 19 transmitted from the access control unit 16 and the synchronization acquisition processing time 26 transmitted from the processing time calculation unit 17a. Set (S45). The activation control unit 18 starts measuring the elapsed time after the off control using a timer or the like (S46). When the measured elapsed time is smaller than the reception start time set in the activation control unit 18 (S47, NO), the activation control unit 18 continues to measure the elapsed time. When the measured elapsed time is equal to or greater than the reception start time (S47, YES), the activation control unit 18 turns on the operations of the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15. (S30), the process from step S31 is executed again.

  By executing the above steps and setting the synchronization acquisition processing time based on the value of BER, the activation start time of the synchronization acquisition unit 11 can be optimized.

  FIG. 8 is a block diagram of a receiving apparatus 1b according to another embodiment. The reception device 1b includes a reception antenna 5, an amplification unit 10, a synchronization acquisition unit 11, a gain adjustment unit 12, a demodulation unit 13, an error correction unit 15, an access control unit 16, and a control unit 2b. The same members as those of the receiving apparatus 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The access control unit 16 has an error counter 91. The error counter 91 counts the number of errors in a bit unit or a packet unit that cannot be corrected by the error correction unit 15 in the received signal. The access control unit 16 calculates a bit error ratio (BER) and a packet error ratio (PER) based on the number of errors counted by the error counter 91. BER represents an error rate per predetermined number of bits in the data. PER represents an error rate per predetermined amount of packets in data. The access control unit 16 transmits the calculated error rate information 90 such as BER and PER to the processing time calculation unit 17a.

  The control unit 2b includes a processing time calculation unit 17b and an activation control unit 18. The processing time calculation unit 17b has a table 80a. The processing time calculation unit 17 b refers to the table 80 a based on the received error rate information 90, calculates the synchronization acquisition processing time 26 of the synchronization acquisition unit 11, and transmits it to the activation control unit 18.

  Similar to the table 80, the table 80a has a BER range and synchronization acquisition processing time information corresponding to the range. Since the error of the received signal is corrected by the error correction unit 15, the BER of the received signal input to the access control unit 16 is basically much smaller than the BER of the received signal input to the error correction unit 15. Value. Therefore, the determination reference value for determining the magnitude of the BER in the table 80a is also smaller than the determination reference value for the BER in the table 80.

  For example, in the DVB-H standard, if the BER of the signal error-corrected by the error correction unit 15 is 1.0 × 10E-10 or less, it is determined that there is no error. Therefore, the table 80a rewrites the column 85 of the table 80 as follows. First, in row 82, when the BER is larger than 9.75 × 10E-11 obtained by subtracting 0.25 × 10E-11 from 1 × 10E-10, the synchronization acquisition processing time is rewritten so as to be 50 ms. The judgment value is set so as to decrease in increments of 0.25 × 10E-11. Further, when the BER is 9.5 × 10E-11 or less in the row 84, rewriting is performed so that the synchronization acquisition processing time becomes 2 ms. Further, when the BER in the row 83 is 9.5 × 10E-11 or more and smaller than 9.75 × 10E-11, the synchronization acquisition processing time is set to an intermediate value 25 ms between the maximum value 50 ms and the minimum value 2 ms. rewrite.

  The activation control unit 18 transmits an activation control signal to the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15 based on the received reception time information 19 and the synchronization acquisition processing time 26. The timing for transmitting the activation control signal differs depending on the received synchronization acquisition processing time 26. By changing the activation start time of the synchronization acquisition unit 11 based on the error rate information 90, the activation start time of the synchronization acquisition unit 11 can be optimized, and the power consumption of the receiving device 1b can be optimized.

  FIG. 9 is a flowchart showing the operation of the receiving apparatus 1b. Since the process from step S50 to step S54 is the same as the process from step S10 to step S14, the description thereof is omitted.

  The error correction unit 15 performs an error correction process on the demodulated data (S55). The access control unit 16 holds the data before error correction by the access control unit 16 in a memory or the like provided in the access control unit 16 (S56). The access control unit 16 executes error correction processing (S57). The error counter 91 provided in the access control unit 16 acquires the difference between the data before error correction and the data after error correction (S58). The error counter 91 calculates a cumulative difference value (S59). The access control unit 16 calculates error rate information 90 such as BER and PER based on the calculated cumulative value (S60).

  When the activation control unit 18 does not perform off control (S61, NO), the receiving device 1b repeats the processing from step S50. When the activation control unit 18 performs the off control (S61, YES), the activation control unit 18 turns off the operations of the amplification unit 10, the synchronization acquisition unit 11, the gain adjustment unit 12, the demodulation unit 13, and the error correction unit 15 ( S62). Since the process from step S63 to step S68 is the same as the process from step S41 to step S47, the description thereof is omitted.

  By executing the above steps and changing the activation start time of the synchronization acquisition unit 11 based on the error rate information 90, the activation start time of the synchronization acquisition unit 11 is optimized and the power consumption of the receiving device 1b is optimized. I can do it.

  FIG. 10 is a block diagram of a receiving device 1c according to another embodiment. The reception device 1c includes a reception antenna 5, an amplification unit 10, a synchronization acquisition unit 11, a gain adjustment unit 12, a demodulation unit 13, an error correction unit 15, an access control unit 16, and a control unit 2c. The demodulator 13 has a MER calculator 14, and calculates and outputs the MER 20. The error correction unit 15 includes an error counter 71, and calculates and outputs a BER 70 that is one of error rate information. In the receiving device 1c, the same members as those of the receiving device 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The causes of errors in the received signal include Gaussian noise that depends on the reception environment of the receiving apparatus and fading that occurs due to movement of the receiving apparatus. Gaussian noise is an average of factors such as atmospheric radiation that scatters electromagnetic radiation from space and atmospheric moisture, and various artificial noises generated by switching of electrical products in urban life. Fading means that radio waves emitted from a broadcast station are reflected by buildings, mountains, etc., and when the receiving device receives multiple radio waves with different path lengths due to these reflections, it is received due to interference between received waves with different path lengths. This is a phenomenon in which the level changes. When the receiving apparatus moves, a change in the path length of the reflected wave occurs with time, so that a change in the reception level due to interference also involves a change in time. Therefore, Gaussian noise is characterized by a small amount of change with time, and fading has a large amount of change with time. In the present embodiment, the control unit 2c predicts the BER value calculated by the error counter 71 based on the MER 20 output from the MER calculation unit 14, and performs synchronization acquisition processing based on the comparison result between the predicted value and the actual measurement value. The time 26 is corrected. As a result, the receiving device 1c can set the optimum starting time of the receiving device according to the amount of noise even when noise with a large temporal change occurs in the received signal. Details of a method for predicting the moving state of the receiving apparatus from the MER and BER values will be described later.

  The control unit 2 c controls the activation timing of the synchronization capturing unit 11 according to the error rate per specific data length calculated by the demodulation unit 13 and the error rate per specific data length calculated by the error correction unit 15. The control unit 2 c includes a processing time calculation unit 17 c and an activation control unit 18. The processing time calculation unit 17 c receives the MER 20 output from the demodulation unit 13. The processing time calculation unit 17 c receives the BER 70 output from the error correction unit 15. The processing time calculation unit 17c calculates a predicted BER value based on the received MER20. The processing time calculation unit 17c compares the calculated predicted BER value with the received BER 70 value. The processing time calculation unit 17c corrects the CNR value calculated from the MER 20 according to the comparison result. The processing time calculation unit 17 c calculates the synchronization acquisition processing time 26 based on the corrected CNR value and the table 50, and transmits it to the activation control unit 18.

  Even when noise having a large temporal change occurs in the received signal by the above operation, it is possible to set the optimal start-up time of the receiving apparatus according to the amount of noise.

  FIG. 11 is a block diagram of the processing time calculation unit 17c. The processing time calculation unit 17 c includes an error amount prediction unit 100, an error amount comparison unit 101, an error amount correction unit 102, and a processing time conversion unit 103. The error amount prediction unit 100 has a table 104. The error amount prediction unit 100 refers to the table 104, converts the MER 20 value transmitted from the MER calculation unit 14 into a BER prediction value, and outputs the BER prediction value 106 to the error amount comparison unit 101. The prediction of BER is performed on the assumption that the noise of the received signal is Gaussian noise. Details of the method of converting the value of MER20 into the predicted value of BER will be described later.

  The error amount comparison unit 101 receives the BER predicted value 106 and the BER 70 transmitted from the error correction unit 15 as inputs. The error amount comparison unit 101 transmits the result of dividing the BER 70 by the BER predicted value 106 to the error amount correction unit 102 as an error amount ratio 107. As described above, the BER prediction value 106 is calculated on the assumption that the noise of the received signal is Gaussian noise. When the noise of the received signal is only Gaussian noise, the BER 70 and the predicted BER value 106 are substantially equal. On the other hand, when fading or the like that is noise other than Gaussian noise is further superimposed on the received signal, the BER 70 is larger than the predicted BER value 106. As a result, the value of the error amount ratio 107 increases. Therefore, by correcting the CNR value according to the error amount ratio 107, the synchronization acquisition processing time 26 can be optimized more accurately.

  The error amount correction unit 102 receives the error amount ratio 107 as an input. The error amount correction unit 102 has a table 105. The error amount correction unit 102 refers to the table 105 based on the error amount ratio 107 and determines the correction amount of the CNR value calculated from the MER 20. The error amount correction unit 102 transmits the determined correction amount 108 to the processing time conversion unit 103. The correction amount 108 is set so that the larger the error amount ratio 107, the smaller the CNR value. Details of the method of setting the CNR correction value 108 from the error amount ratio 107 will be described later.

  The processing time conversion unit 103 receives the correction amount 108 and the MER 20 as inputs. The processing time conversion unit 103 has a table 50. The processing time conversion unit 103 calculates a CNR value from the input MER 20 and corrects the calculated CNR value based on the correction amount 108. The processing time conversion unit 103 refers to the table 50 based on the corrected CNR value and determines the synchronization acquisition processing time 26. The synchronization acquisition processing time 26 increases as the CNR value decreases. Therefore, by correcting the CNR value according to the predicted BER value and determining the synchronization acquisition processing time 26 based on the correction value, the synchronization acquisition processing time according to the type of noise of the received signal can be set.

  The processing time conversion unit 103 may receive a CNR value calculated from the MER 20 in order to refer to the table 104 in the error amount prediction unit 100 instead of the MER 20. Thereby, the calculation processing of the CNR value from the MER 20 for referring to the table 50 can be omitted, and the processing speed can be increased.

  Even when noise having a large temporal change occurs in the received signal due to the above operation, an optimal start-up time of the receiving apparatus corresponding to the amount of noise is obtained by appropriately correcting the CNR value calculated from the MER 20. Can be set.

  FIG. 12 is a table 104 for referring to the predicted BER value from the CNR value calculated from the MER 20. The table 104 is stored in the error amount prediction unit 100. A column 117 is a CNR value calculated from the MER20. The conversion rate between the MER 20 and the CNR is calculated in advance and stored in the error amount prediction unit 100. A column 118 is a value of the BER output from the error correction unit 15 predicted based on the calculated CNR value. The predicted BER value is predicted on the assumption that the received signal is received in a Gaussian noise environment. In the present embodiment, the MER is converted to the CNR because the noise amount is defined by the CNR in the communication standard such as DVB-H, and the association with the standard becomes easy. MER and BER may be directly associated without calculation.

  Lines 110 to 116 show the predicted BER values corresponding to the calculated CNR values. Since the value of CNR in 16QAM required in the DVB-H standard is 13.9 dB, the predicted BER corresponding to CNR = 13.9 dB is set to 2.0 × 10E-4 in the row 112, and the values before and after that Are defined as shown in lines 110 to 116.

  The error amount prediction unit 100 can output the BER predicted value 106 based on the input MER 20 by referring to the table 104 defined as described above. For example, when the CNR calculated from the MER 20 is 13 dB, the BER prediction value output from the error amount prediction unit 100 is 3.0 × 10E-4 from the row 110 of the table 104. In this embodiment, the modulation method is described as 16QAM. However, a plurality of tables corresponding to a plurality of modulation methods may be prepared, and the table may be switched according to the modulation method of the received signal.

  FIG. 13 shows a table 105 included in the error amount correction unit 102. The error amount ratio R in the column 130 is a value obtained by dividing the BER 70 output from the error correction unit by the predicted BER value 106 output from the error amount prediction unit 100. The larger the error amount ratio R, the larger the actual error amount. That is, it can be estimated that noise that causes an error is superimposed on the OFDM symbol signal due to influences other than Gaussian noise. The error amount ratio R is calculated by the error amount comparison unit 101 and output as the error amount ratio 107.

  A column 131 is a correction amount for correcting the CNR value calculated from the MER 20. The correction amount is set so that the CNR value decreases as the error amount ratio R increases. The step of the error amount ratio R in the column 130 and the correction amount in the column 131 have different values depending on the circuit configuration of the receiving device and the design conditions of the LSI in each standard.

  In this embodiment, as shown in line 120, when the error amount ratio R is smaller than 1.5, the correction value is set to 0 because the BER predicted value and the actually measured value are equivalent. Further, as shown in line 120 to line 129, every time the error amount ratio R increases from 1.5, the absolute value of the correction amount is increased by 0.1. By referring to the table 105, the error amount correction unit 102 outputs the correction amount 108 so that the CNR value decreases as the error amount ratio R increases. Accordingly, the processing time conversion unit 103 can set the synchronization acquisition processing time to be output longer as the error amount ratio 107 input to the error amount correction unit is larger.

  FIG. 14 is a processing flow of the processing time calculation unit 17b. The processing time calculation unit 17c acquires the MER 20 transmitted from the demodulation unit 13 (S70). The processing time calculation unit 17c acquires the BER 70 transmitted from the error correction unit 15 (S71). The processing time calculation unit 17c calculates a BER predicted value based on the acquired MER20 (S72). The processing time calculation unit 17c calculates the error amount ratio by dividing the acquired BER 70 by the calculated BER predicted value (S73). The processing time calculator 17c calculates a CNR correction amount based on the calculated error amount ratio (S74). The processing time calculation unit 17c corrects the CNR value by adding the CNR correction amount calculated from the error amount ratio to the CNR value calculated from the MER 20, and determines the synchronization acquisition processing time from the corrected CNR value (S75).

  By executing the above steps, the receiving device 1c having the processing time calculation unit 17c can predict the type of error based on MER and BER, and optimize the synchronization acquisition processing time according to the predicted type of error. I can do it. The error type can be predicted from two different error rates. Therefore, by using the MER output from the demodulator 13 and the BER output from the access controller 16, the type of error can be predicted as in the present embodiment. Also, by using the BER output from the error correction unit and the BER output from the access control unit 16, the type of error can be predicted as in the present embodiment.

  FIG. 15 is a block diagram of a receiving device 1d according to another embodiment. The reception device 1d includes a reception antenna 5, an amplification unit 10, a synchronization acquisition unit 11, a gain adjustment unit 12a, a demodulation unit 13a, an error correction unit 15, an access control unit 16, and a control unit 2c. The same members as those of the receiving apparatus 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The demodulator 13 a includes a MER calculator 14 and a moving speed calculator 140. In the above-described embodiment, the method for optimizing the activation start time of the synchronization capturing unit 11 from the MER output from the MER calculation unit 14 and the BER or PER value output from the error counter 71 has been described. In the present embodiment, a method for optimizing the startup time of the gain adjusting unit 12a based on the moving speed calculated by the moving speed calculating unit 140 will be described.

  The MER calculation unit 14 transmits the MER 20 to the processing time calculation unit 17. The moving speed calculation unit 140 calculates the moving speed of the receiving device 1d based on the amount of phase change in which the constellation of data obtained by demodulating the received OFDM symbol signal rotates around the origin of the XY coordinates with time. To do. The movement speed calculation unit 140 outputs the calculated movement speed 141 to the processing time calculation unit 142. In this embodiment, the moving speed calculation unit 140 is mounted on the demodulation unit 13a, but may be mounted on a portion other than the demodulation unit 13a.

  As described above, the control unit 2c sets the synchronization acquisition processing time of the synchronization acquisition unit 11 according to the error rate per specific data length calculated by the demodulation unit 13a and adjusts the gain according to the moving speed 141. The time for adjusting the voltage gain in the unit 12a is set. The control unit 2 c includes processing time calculation units 17 and 142 and an activation control unit 18. The processing time calculation unit 17 has a table 50. The processing time calculation unit 17 refers to the table 50 based on the received MER 20 and transmits the synchronization acquisition processing time 26 to the activation control unit 18. The processing time calculation unit 142 has a table 143. The processing time calculation unit 142 refers to the table 143 based on the received moving speed 141 and transmits the amplification degree adjustment time 144 to the activation control unit 18.

  Based on the received reception time information 19, synchronization acquisition processing time 26, and amplification degree adjustment time 144, the activation control unit 18 sends the amplification unit 10, synchronization acquisition unit 11, gain adjustment unit 12 a, demodulation unit 13 a, and error correction unit 15. The activation control signals 21, 22, 23, 24, and 25 are transmitted. The gain adjusting unit 12a adjusts the amplification degree of the OFDM symbol signal so that the voltage gain of the received OFDM symbol signal becomes constant. More specifically, the gain adjustment unit 12 a determines a gain to be set in the amplification unit 10 based on the setting signal 145 transmitted from the synchronization acquisition unit 11, and transmits the gain adjustment signal 146 to the amplification unit 10.

  The timing for transmitting the activation control signal differs depending on the received synchronization acquisition processing time 26 and amplification adjustment time 144. By changing the activation start times of the synchronization acquisition unit 11 and the gain adjustment unit 12a based on the MER 20 and the moving speed 141, the activation start times of the synchronization acquisition unit 11 and the gain adjustment unit 12a are optimized, and the power consumption of the receiving device 1d is reduced. Can be optimized.

  FIG. 16 is a detailed block diagram of the gain adjusting unit 12a. The gain adjusting unit 12a adjusts the amplification degree so that the voltage gain of the received OFDM symbol signal is constant. The gain adjustment unit 12a includes a gain processing unit 150 and a storage unit 151. The gain processing unit 150 determines the amplification degree set in the amplification unit 10 based on the received setting signal 145. The gain processing unit 150 transmits a gain adjustment signal 146 to the amplification unit 10 and transmits a setting value 152 for determining the amplification degree to the storage unit.

  The storage unit 151 stores the set value 152 of the amplification level set when receiving the OFDM symbol signal. When storage unit 151 receives activation control signal 23 for turning on gain adjustment unit 12a, storage unit 151 transmits gain setting value stored at the time of the previous OFDM symbol signal reception to gain processing unit 150 as setting value 153. The gain processing unit 150 starts adjusting the amplification degree using the set value 153 read from the storage unit 151 as an initial value.

  When the condition for receiving a signal by the receiving device 1d does not change greatly, the gain processing condition does not change greatly. Therefore, by storing the gain setting conditions in the storage unit 151 and reading the setting conditions at the next amplification level setting, the processing time required to adjust the amplification level can be shortened. The gain setting technique in the present embodiment can be applied to other embodiments.

  FIG. 17 is a table 143 included in the processing time calculation unit 142. The moving speed of the column 170 is the moving speed 141 output from the demodulator 13a. A column 171 is a time necessary for setting the amplification degree set in the amplification unit 10 by the gain adjustment unit 12a. It is set so that the amplification degree adjustment time becomes longer as the moving speed is higher.

  A row 160 indicates the amplification degree time when the receiving apparatus 1d is in a stopped state, that is, when the moving speed is 0 km / h. When the receiving device 1d is in a stopped state, there is no change in receiving conditions due to movement. Therefore, the gain adjustment unit 12a can use the set value set at the time of the previous signal reception and stored in the storage unit 151 as it is, and therefore the amplification adjustment time may be short.

  A row 162 shows the amplification adjustment time when the receiving apparatus 1d is moving at high speed, that is, when the moving speed is 30 km / h. When the receiving device 1d is moving at high speed, the signal receiving conditions are expected to change greatly. Therefore, even if the gain adjustment unit 12a uses the setting value set at the time of the previous signal reception and stored in the storage unit 151, the gain adjustment unit 12a assigns the maximum value defined in the communication standard guidelines as the amplification adjustment time. In the present embodiment, it is assumed that the maximum value defined by the guideline is 20 ms. Similarly, the maximum value is assigned when the moving speed is 30 km / h or more.

  A row 161 shows the amplification adjustment time when the receiving device 1d is moving at a walking speed, that is, when the moving speed is 3 km / h. When the receiving device 1d is moving at the walking speed, it is predicted that a time equal to the maximum value defined in the communication standard guidelines is not necessary as the gain setting time. Therefore, the amplification degree adjustment time when moving at walking speed is 10 ms, which is half of the maximum value defined in the guideline.

  By assigning the amplification adjustment time according to the moving speed as described above, the amplification adjustment time can be optimized according to the signal reception conditions.

1, 1a, 1b, 1c, 1d Receiver 2, 2a, 2b, 2c Control unit 5 Reception antenna 10 Amplification unit 11 Synchronization acquisition unit 12, 12a Gain adjustment unit 13, 13a Demodulation unit 14 MER calculation unit 15 Error correction unit 16 Access control unit 17, 17a, 17b, 17c Processing time calculation unit 18 Start control unit 50, 80, Table 71, 91 Error counter 100 Error amount prediction unit 101 Error amount comparison unit 102 Error amount correction unit 103 Processing time conversion unit 104, 105 Table 140 Movement speed calculation unit 142 Processing time calculation unit 150 Gain processing unit 151 Storage unit

Claims (5)

A receiving device for receiving a modulated symbol signal,
A synchronization acquisition unit for detecting a start position of the symbol signal in a predetermined synchronization acquisition processing time;
A demodulator that demodulates the symbol signal detected by the synchronization supplement unit and calculates a modulation error rate of the symbol signal;
A control unit configured to set the synchronization acquisition processing time according to the modulation error rate calculated by the demodulation unit. An error correction unit for calculating and correcting errors in a plurality of symbol signals demodulated in a predetermined time by the demodulation unit;
The reception unit according to claim 1, wherein the control unit sets the synchronization acquisition processing time according to the modulation error rate calculated by the demodulation unit and the demodulation error rate calculated by the error correction unit. apparatus.   The control unit estimates the demodulation error rate from the calculated modulation error rate, and sets the synchronization acquisition processing time according to a result of comparing the estimated demodulation error rate with the calculated demodulation error rate. The receiving apparatus according to claim 2, wherein the receiving apparatus is characterized. A gain adjusting unit that adjusts the amplification degree of the symbol signal so that the amplitude of the received symbol signal is constant, and a moving speed calculating unit that calculates the moving speed of the receiving device based on the phase change amount of the symbol signal And
The receiving apparatus according to claim 1, wherein the control unit sets a time for adjusting the amplification degree according to the moving speed.   The gain adjustment unit has a storage unit that stores the set value of the amplification degree set at the time of receiving the previous signal, and a gain processing unit that reads the stored set value from the storage unit at the time of activation, The receiving device according to claim 4.