JP2008244843A - Receiver and method for estimating reception environment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver deciding as to whether or not the receiver is placed at the midway of a movement by estimating a reception environment by the state of a receiving signal and a method for estimating the reception environment. <P>SOLUTION: A pilot symbol extracted by a base band signal is imparted to a section 16 for estimating the reception environment by an equalizing processing section 13. In the section 16 for estimating the reception environment, the quantity of the received power varied in the pilot symbol is computed, and whether or not the receiver is placed at the midway of the movement is estimated on the basis of the quantity of the variation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a receiving apparatus that performs mobile communication, and a receiving environment estimation method that estimates a receiving environment thereof, and in particular, a receiving apparatus that performs diversity reception of digital broadcasting and a receiving environment that estimates the receiving environment. It relates to an estimation method.

  In recent years, with the development of digital compression coding technology and high-speed communication technology, digitization in satellite and terrestrial broadcast communication and digitization in mobile communication such as mobile phones has been realized. In addition, with the realization of digitization in broadcast signals and mobile communications, in-vehicle televisions and mobile phones that receive and reproduce digital television broadcasts are also provided. In such mobile communication, since the reception state becomes unstable depending on the position of the antenna while the receiving apparatus is moving, a plurality of antennas having different spatial positions are provided and spatial diversity reception is performed.

In this receiver using spatial diversity reception, the signals received by multiple antennas are demodulated, and then the propagation characteristics (multipath) analysis of each signal is performed. Based on the analysis results, signal synthesis is performed by weighted addition. (RAKE combining) is performed to improve the reception characteristics (see Patent Document 1). In Patent Document 1, a plurality of signals received by such spatial diversity reception are RAKE-combined to stabilize the reception state. And when it is not moving, it is assumed that it is in a stable reception environment, one of the plurality of antennas is operated, power supply to the other antennas is stopped, and power consumption is reduced Is realized.
JP 2002-101029 A

  However, in the receiving device of Patent Document 1, it is detected whether or not the vehicle is moving based on a running detection signal obtained by a running monitor of a vehicle equipped with the receiving device. That is, the operating state of the mounted vehicle is confirmed by a travel detection signal (for example, a vehicle speed pulse) from the outside of the receiving device. Therefore, it is necessary to mount the vehicle on the vehicle so that a driving detection signal is input from the outside, and the mounting operation of the receiving device becomes complicated.

  It has also been proposed to detect that the mounted vehicle is moving by detecting vibration applied to the receiving device itself. However, when it is determined whether or not the mounted vehicle is moving based on the presence or absence of vibration in this way, not only a mechanical sensor for vibration detection is required, but the mounted vehicle is actually moving, such as during idling. There is a risk of false detection of detecting vibration even when it is not in the middle.

  In view of such a problem, an object of the present invention is to provide a reception apparatus and a reception environment estimation method for determining whether or not the user is moving by estimating a reception environment based on a state of a received signal. To do.

  In order to achieve the above object, a receiving apparatus according to the present invention includes an antenna that receives a communication signal including a reference signal that serves as a reference when performing demodulation while reducing the influence of a transmission path, and the antenna that is received by the antenna. A demodulator that demodulates the communication signal; and a decoder that decodes the communication signal demodulated by the demodulator; and a receiver that is mounted on a mobile unit, the communication signal demodulated by the demodulator And a reception environment estimation unit that estimates whether the moving body is in a moving state or a stopped state based on a temporal variation amount of the reference signal.

  Then, by providing a plurality of antennas and demodulation units, respectively, a plurality of reception systems are configured, and when diversity reception is performed to operate the plurality of reception systems simultaneously, the plurality of demodulation units are demodulated. A signal synthesizer that synthesizes the communication signal and outputs to the decoder, and the reception environment estimator estimates that the amount of temporal variation of the reference signal is large and the moving body is in a moving state In addition, diversity reception by the plurality of reception systems is performed.

  At this time, based on a temporal variation amount of the reference signal provided in the communication signal demodulated by the demodulator, a moving state estimation for estimating whether the moving body is in a moving state or a stopped state And a reception situation estimation unit that estimates a reception situation by the antenna based on an error rate of the signal decoded by the decoder, and the movement situation estimation unit has a temporal variation amount of the reference signal. When it is small and when it is estimated that the moving body is in a stopped state, the reception status estimation unit has a small error rate of the signal decoded by the decoder, and the reception status by the antenna is good It is also possible to select one reception system that provides the best reception status when it is estimated, and perform a reception operation using the one reception system.

  The power supply control unit further supplies power to the plurality of reception systems, and the power supply control unit supplies power to all the reception systems when performing the diversity reception, and the plurality of reception systems. When the reception operation by one of the reception systems selected from among them is performed, the power supply to the reception systems other than the selected reception system is stopped.

  The communication signal is configured by multiplexing a plurality of digitally modulated signals arranged at regular frequency intervals, and the reference signal is predetermined in each of the time axis direction and the frequency axis direction. Are arranged at intervals of At this time, the communication signal may be an orthogonal frequency division multiplex transmission system signal, and the reference signal may be a pilot symbol.

  Then, the fluctuation amount of the reference signal is calculated from the difference in received power between the reference signals that are arranged on the same frequency and are adjacent on the time axis. The fluctuation amount of the reference signal may be calculated by the sum or average of the differences in received power of a plurality of adjacent reference signals.

  The reception environment estimation method of the present invention is a reception environment estimation method for estimating a reception environment in a reception device that receives a communication signal having a reference signal that serves as a reference when performing demodulation while reducing the influence of a transmission path. A first step of calculating a temporal variation amount of the reference signal provided in the communication signal demodulated by a unit, and a temporal variation amount of the reference signal calculated in the first step, And a second step of estimating whether the moving body on which the receiving device is mounted is in a moving state or a stopped state.

  At this time, a reception environment estimation method for estimating a reception environment in the reception apparatus having a plurality of reception systems, the third step of calculating an error rate of the decoded communication signal, and the calculation in the third step And a fourth step of estimating the reception status of the receiving device based on the error rate, wherein in the second step, the amount of temporal variation of the reference signal is small, and the moving body is stopped. And when it is estimated that the communication signal error rate is small and the reception status by the antenna is good in the fourth step, One receiving system that provides the best reception status may be selected.

  The communication signal is configured by multiplexing a plurality of digitally modulated signals arranged at regular frequency intervals, and the reference signal is predetermined in each of the time axis direction and the frequency axis direction. Are arranged at intervals of At this time, the communication signal may be an orthogonal frequency division multiplex transmission system signal, and the reference signal may be a pilot symbol.

  Then, the fluctuation amount of the reference signal is calculated from the difference in received power between the reference signals that are arranged on the same frequency and are adjacent on the time axis. The fluctuation amount of the reference signal may be calculated by the sum or average of the differences in received power of a plurality of adjacent reference signals.

  According to the present invention, it is possible to check the movement status of a mobile body on which a receiving device is mounted based on the amount of time variation of an existing reference signal such as a pilot symbol. It is not necessary to input a signal indicating the operation, and it is not necessary to install a mechanical sensor for sensing vibration of the moving body. In addition, since it is only necessary to provide a calculator or a calculation program for calculating the fluctuation amount of the existing reference signal, there is no need to add a mechanical structure for detecting the moving state of the moving body. It is possible to prevent the apparatus from becoming large.

  First, the basic configuration of a receiving apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an internal configuration of a receiving apparatus having the basic configuration. In the following description, an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) terrestrial digital television broadcast receiving device will be described as an example, but it is used for synchronization and distortion correction of pilot symbols and the like. Any other communication system may be used as long as it is a receiving apparatus for a digital communication system having a reference signal transmitted at regular intervals.

  1 includes an antenna 10 that receives a digital broadcast signal, an RF (Radio Frequency) signal processing unit 11 that selects a digital broadcast signal in a desired band from the antenna 10 and converts it into a baseband signal, An FFT unit 12 that performs fast Fourier transform (FFT) on a baseband signal obtained by selecting a channel in the RF signal processing unit 11, and an FFT process performed by the FFT unit 12 to convert a time axis signal into a frequency axis An equalization processing unit 13 that performs equalization processing on the baseband signal converted into a signal, and a baseband signal from which multipath distortion received during propagation by the equalization processing unit 13 is removed is based on a digital modulation method. Digital demodulation unit 15 that demodulates the received signal and reception environment estimation that estimates the reception environment based on pilot symbols (to be described later) extracted from the baseband signal by equalization processing unit 13. And a MPEG decoder 17 for decoding an MPEG (Moving Picture Experts Group) encoded signal obtained by demodulation by the digital demodulator 15 based on the MPEG compression method. The FFT unit 12 and the equalization processing unit 13 constitute a demodulation unit 14 that performs demodulation processing based on an orthogonal frequency division multiplex (OFDM) transmission scheme.

  This receiving apparatus for receiving a digital broadcast signal receives a digital broadcast by the OFDM transmission method from an antenna 10. The OFDM scheme is a scheme for multiplexing and transmitting a large number of subcarriers orthogonal to each other within one channel band. At this time, the RF signal processing unit 11 selects an OFDM signal (digital broadcast signal) that is a high-frequency signal of a desired channel, and converts the selected OFDM signal to a baseband signal that is an IF (Intermediate Frequency) signal. (Down-convert). When the obtained baseband signal is given to the FFT unit 12, the baseband signal that is a time axis signal is converted into a baseband signal that is a frequency axis signal by FFT processing.

  When the FFT unit 12 performs FFT processing, symbol synchronization, carrier frequency synchronization, and sampling frequency synchronization are established. That is, the offset of the symbol length (time length of each symbol), the carrier frequency, and the sampling frequency (frequency of the subcarrier interval) generated by a transmission path such as multipath is corrected. At this time, symbol synchronization and carrier frequency synchronization are established by using a guard interval provided for each symbol and comprising the same signal as the latter half of the symbol. Also, sampling frequency synchronization is established by estimating the frequency offset using pilot symbols described later. The carrier frequency synchronization may be established by estimating a frequency offset using a pilot symbol.

  As shown in FIG. 2, the baseband signal FFT-processed by the FFT unit 12 is composed of data symbols and pilot symbols arranged in the frequency direction and the time direction, and these are collectively called an OFDM symbol sequence. In the ISDB-T system, a scattered pilot symbol (hereinafter referred to as “SP symbol”) is used as a pilot symbol. The frequency direction and the time direction are also called a carrier direction and a symbol direction, respectively. In FIG. 2, the time number (symbol number) corresponding to the time direction is represented by t (integer of t ≧ 0), and the carrier number corresponding to the frequency direction is represented by l (0 ≦ l ≦ (L−1)). , L: total number of subcarriers). Further, t represents time when the symbol length of the OFDM signal is used as a unit. Further, a position in the OFDM symbol string that is uniquely determined by uniquely defining t and l is called a carrier position, and this carrier position is represented by (t, l).

  The SP symbol is arranged at a carrier position satisfying l = 3 × (t mod 4) + 12p. Note that mod represents a remainder operation, and p is an integer. That is, as shown in FIG. 2, when attention is paid to a signal at a certain time t, SP symbols are arranged every 12 subcarriers 12 on the frequency axis. Each time the time t advances by one symbol, the SP signal is shifted in the frequency direction by three subcarriers. In other words, when attention is paid to a signal of a certain subcarrier l, SP symbols are arranged every four symbols on the time axis. Thus, for example, at time t = 0, SP symbols are arranged at carrier positions (0, 0), (0, 12), (0, 24), (0, 36),. Then, SP symbols are arranged at carrier positions (1, 3), (1, 15), (1, 27), (1, 39),. Further, data symbols are arranged at carrier positions other than the carrier position where the SP symbols are arranged.

  When the baseband signal from the FFT unit 12 is supplied to the equalization processing unit 13, the SP symbols arranged in the frequency axis direction and the time axis direction as shown in FIG. The transmission path characteristics for each position are estimated, and equalization processing is performed based on the established transmission path characteristics. At this time, first, transmission path characteristics with respect to the carrier position of each SP symbol are estimated by each SP symbol. In other words, the SP symbol obtained from the received signal is complex-divided by the SP symbol generated in the equalization processing unit 13 to estimate the transmission path characteristic with respect to the carrier position of the SP symbol.

  Then, for each subcarrier, interpolation in the time axis direction is performed using transmission path characteristics with respect to the carrier position of each SP symbol arranged every four symbols on the same subcarrier. As a result, the channel characteristics are estimated for the carrier positions of all the subcarriers having the SP symbol every four symbols. That is, by performing interpolation processing on the data symbols arranged between the SP symbols arranged in the time axis direction, the transmission path characteristics in each data symbol are estimated. When the transmission path characteristics in the time axis direction are interpolated, an averaging process of the transmission path characteristics estimated from the SP symbols is performed by an IIR (Infinite Impulse Response) type low-pass filter.

  Further, interpolation in the frequency axis direction is performed for each symbol based on the channel characteristics estimated for the carrier position of the SP symbol and the channel characteristics estimated by performing interpolation in the time axis direction. As a result, the transmission path characteristics of all the subcarriers where no SP symbol is arranged are determined by the transmission path estimated from the SP symbol directly or every three subcarriers by time axis interpolation. Is estimated. That is, for subcarriers arranged between subcarriers having SP symbols in the frequency axis direction, transmission path characteristics in the data symbols are estimated. When performing the interpolation of the channel characteristics in the frequency axis direction, for example, the channel characteristics estimated for the subcarrier having the SP symbol are input to a FIR (Finite Impulse Response) type low-pass filter. Thus, the transmission path characteristics of subcarriers where no SP symbol is arranged are estimated.

  Thus, when the transmission path characteristics of all data symbols are estimated based on the SP symbols, the estimated transmission path characteristics are obtained for each data symbol obtained from the signal on the frequency axis from the FFT unit 12. By performing complex division, equalization processing is performed, and distortions in amplitude and phase due to multipath effects and the like are removed. As this equalization processing, for example, a zero focusing equalization method that directly divides the estimated transmission path characteristic is used. Since this zero-focusing equalization process has a problem of noise enhancement, there is a Minimum Mean Square Error (MMSE) equalization method for reducing the noise enhancement problem. In the case of this MMSE equalization method, it is also necessary to estimate the average power value of noise (additional noise) added on the transmission line.

  In this way, the baseband signal that has been equalized for each symbol is demodulated by the digital demodulation unit 15 using the digital modulation scheme set for each subcarrier. Examples of the digital modulation method include QAM (Quadrature Amplitude Modulation), QPSK (Quadrature Phase Shift Keying), and DQPSK (Differential Quadrature Phase Shift Keying). Then, when the MPEG encoded signal obtained by demodulating by the digital demodulator 15 is given to the MPEG decoder 17, it is decoded based on the MPEG compression method to obtain a video signal. This video signal is further applied to a display device (not shown) such as a display, so that the video is reproduced.

  When the received digital broadcast is demodulated and decoded, the reception environment estimation unit 16 estimates the reception environment of the reception device based on the SP symbols extracted by the equalization processing unit 13. Is done. The reception environment estimation operation in the reception environment estimation unit 16 will be described below.

  FIG. 3 shows a change in one time direction of the subcarrier in which the SP symbol is arranged. In FIG. 3, SP symbols SP1, SP2, and SP3 of symbol numbers t-4, t, and t + 4 arranged on the subcarrier having carrier number l, that is, the carrier positions are (t-4, l), (t , L), received power (amplitude) of SP symbols SP1, SP2 and SP3 corresponding to (t + 4, l). The received power of the SP symbols SP1, SP2, and SP3 varies as shown in FIG. 3A due to the influence of the Doppler shift due to the moving speed and the change in the reception environment when the receiving apparatus is moving. In addition, when the receiving apparatus is not moving, not only Doppler shift does not occur, but also the change in the reception environment is small. Therefore, fluctuations in the received power of the SP symbols SP1, SP2 and SP3 are as shown in FIG. So small.

  As shown in FIG. 3, the amount of fluctuation in received power of SP symbols of the same subcarrier changes depending on the moving state of the receiving apparatus. Therefore, the reception environment estimation unit 16 detects whether the receiving apparatus is moving by calculating the sum or average of the received power differences of adjacent SP symbols on the same subcarrier and monitoring the calculated value. Is done. That is, when the reception power of three adjacent SP symbols SP1 to SP3 becomes P1 to P3, respectively, as shown in FIG. 3, the reception environment estimation unit 16 monitors the total sum of the reception power of the three SP symbols. Assuming that there is a fluctuation amount, D = | P2-P1 | + | P3-P2 | is calculated. When the received power fluctuation amount D becomes equal to or greater than the threshold value Dth, it is determined that the receiving apparatus is moving.

  In the example of FIG. 3, the sum of the differences in received power between three adjacent SP symbols on the same subcarrier is defined as a variation amount D, and the reception device is moving by monitoring the variation amount D. However, it is possible to more accurately determine the movement state by setting the total sum of received power differences of a plurality of SP symbols adjacent to each other in the same subcarrier as the variation amount D. It can be performed. Alternatively, the average value may be calculated as the fluctuation amount D instead of the sum of the differences in received power of the SP symbols, and the movement state may be determined based on the fluctuation amount D based on the average value.

  Furthermore, not only one subcarrier but also a plurality of subcarriers may be used to obtain a variation amount D that is the sum or average of received power differences between adjacent SP symbols. At this time, for example, when SP symbols are arranged as shown in FIG. 2, in the subcarriers having carrier numbers 0, 3, 6, 9, 12, and 15, the difference in received power difference between a plurality of adjacent SP symbols. It is assumed that the sum or average is obtained and the variation amounts are D0, D3, D6, D9, D12, and D15, respectively.

  Then, the average value of the variation amount in each subcarrier (in the case of FIG. 2, (D0 + D3 + D6 + D9 + D12 + D15) / 6) is defined as the variation amount D, and it is determined whether or not the receiving apparatus is moving based on the comparison result with the threshold value Dth. It does n’t matter. Note that the threshold value Dth is preferably slightly larger than 0 because the fluctuation amount D is close to 0 when the receiving apparatus is not moving. Further, the maximum value and the minimum value of the fluctuation amount in each subcarrier are omitted, and the average value of the remaining fluctuation amounts (in the case of FIG. 2, the average value of the fluctuation amounts of the four subcarriers excluding the maximum value and the minimum value). The fluctuation amount D may be used. Furthermore, the maximum amount of variation in each subcarrier may be the variation amount D.

<Embodiment>
An embodiment having the above-described basic configuration will be described with reference to the drawings. FIG. 4 is a block diagram showing an internal configuration of the receiving apparatus according to this embodiment. In the present embodiment, for the sake of simplicity, a receiving apparatus that performs diversity reception using two antennas is illustrated. However, the present invention can also be applied to a receiving apparatus that performs diversity reception using three or more antennas. . That is, only the number of antennas is different, and when the reception environment is good, power is supplied only to the antenna with the best reception condition, and when the reception environment is bad, spatial diversity reception is performed with multiple antennas. is there.

  4 includes antennas 10a and 10b, RF signal processing units 11a and 11b, and FFT that have the same configuration as the antenna 10, RF signal processing unit 11, FFT unit 12, and equalization processing unit 13 of the receiving device of FIG. And an MRC combining unit 41 that combines the baseband signals equalized by the equalization processing units 13a and 13b with MRC (Maximum Ratio Combining). A digital demodulator 15 that demodulates the baseband signal synthesized by the synthesizer 41 based on the digital modulation method, and an MPEG encoded signal obtained by demodulating the digital demodulator 15 based on the MPEG compression method. An MPEG decoder 17, a digital demodulator 15x that demodulates the baseband signal that has been equalized by the equalization processor 13b, A reception environment estimation unit 42 that estimates a reception environment such as a state and a moving state; a power supply control unit 43 that controls power supply of the RF signal processing units 11a and 11b according to the reception environment estimated by the reception environment estimation unit 42; Is provided. The demodulation unit 14a is configured by the FFT unit 12a and the equalization processing unit 13a, and the demodulation unit 14b is configured by the FFT unit 12b and the equalization processing unit 13b.

  When the receiver configured as shown in FIG. 4 selects a digital broadcast signal of a desired band by the RF signal processing unit 11a via the antenna 10a, it converts it to a baseband signal by down-conversion, and then performs an FFT unit. 12a. Then, the FFT unit 12a converts the baseband signal from the RF signal processing unit 11a from the time axis signal to the frequency axis signal, and the equalization processing unit 13a converts each data based on the SP symbol in the baseband signal. The symbol is equalized and sent to the MRC synthesis unit 41.

  Similarly, when a digital broadcast signal of a desired band is selected by the RF signal processing unit 11b via the antenna 10b, it is converted into a baseband signal by down-conversion and given to the FFT unit 12b. Then, the FFT unit 12b converts the baseband signal from the RF signal processing unit 11b from a time axis signal to a frequency axis signal, and the equalization processing unit 13b converts each data based on the SP symbol in the baseband signal. Equalize the symbol. Note that the baseband signal equalized by the equalization processing unit 13b is given to the MRC synthesis unit 41 and the digital demodulation unit 15x.

  Therefore, when power is supplied to each of the RF signal processing units 11a and 11b by the power supply control unit 43 in order to perform diversity reception, the baseband signal by the digital broadcast signal received by each of the antennas 11a and 11b is Are provided to the MRC synthesis unit 41 from the respective processing units 13a and 13b. The MRC synthesis unit 41 adjusts the gains of the baseband signals whose phase and amplitude distortion are corrected by the equalization processing units 13a and 13b to optimum values, and then weights the two baseband signals with the optimum gains. The result of the addition is a single baseband signal.

  The baseband signal is given to the digital demodulator 15 so that it is converted into an MPEG encoded signal and then decoded by the MPEG decoder 17. At this time, the baseband signal from the equalization processing unit 13b is supplied to the digital demodulation unit 15x and demodulated. Then, the MPEG encoded signals obtained by the digital demodulation units 15 and 15x are given to the reception environment estimation unit 42, and the reception status is determined based on the error state of the demodulated MPEG encoded signals.

  The reception environment estimation unit 42 is provided with a movement state estimation unit 42x that receives the SP symbols extracted by the equalization processing units 13a and 13b and estimates the movement state of the reception device, and the MPEG from the digital demodulation units 15 and 15x. A reception status estimation unit 42y that receives the encoded signal and estimates the reception status of the reception device. At this time, in the case of diversity reception, the movement state estimation unit 42x confirms the movement state by the sum or average of the fluctuation amounts D obtained from the SP symbols extracted by the equalization processing units 13a and 13b. Alternatively, the movement state may be confirmed by one of the fluctuation amounts D obtained from the SP symbols extracted by the equalization processing units 13a and 13b.

  In the case of diversity reception, the reception status estimation unit 42y may determine the reception status from both or one of the MPEG encoded signals from the digital demodulation units 15 and 15x. That is, when judging based on the bit error rate of the MPEG encoded signal, the reception status may be judged based on the sum or average of the bit error rates of the MPEG encoded signals from the digital demodulation units 15 and 15x. The reception status may be determined based on the lower bit error rate of the MPEG encoded signals from the demodulation units 15 and 15x. Further, the reception status may be determined based on the bit error rate of the MPEG encoded signal from the digital demodulator 15 that acquires the MPEG encoded signal from the combined baseband signal.

  Further, when the reception operation is switched from diversity reception to reception by one antenna, the reception status estimation unit 42y compares the states of the MPEG encoded signals from the digital demodulation units 15 and 15x to determine the reception status. Determine which antenna is good. That is, when judging the reception status based on the bit error rate of the MPEG encoded signal, when the bit error rate of the digital demodulator 15x is high, it is determined that the reception status by the antenna 10a is good, and the power supply control unit The power supply from 43 to the RF signal processing unit 11b is stopped. On the other hand, when the bit error rate of the digital demodulator 15x is low, it is determined that the reception status by the antenna 10b is good, and the power supply from the power supply controller 43 to the RF signal processor 11a is stopped. .

The reception status estimation unit 42y determines the reception status based on the bit error rate. At this time, if the bit error rate after Viterbi decoding of the MPEG encoded signal is 2 × 10 ⁻⁴ or less. It can be assumed that there is no pseudo error after Reed-Solomon decoding. Therefore, if the bit error rate threshold is 2 × 10 ⁻⁴ and the bit error rate is less than or equal to this threshold, it may be determined that the reception status is good. The reception status may be determined based on not only the bit error rate but also the demodulation error rate and the number of packet errors, or a combination thereof.

  The switching control of the reception operation by the reception environment estimation operation in this reception apparatus will be described with reference to the flowchart of FIG. FIG. 5 is a flowchart showing a setting operation for adopting / not adopting the diversity receiving operation during the receiving operation.

  As shown in FIG. 5, when reception of a digital broadcast is instructed and a reception operation is started (STEP 1), the power supply control unit 43 supplies power to both the RF signal processing units 11a and 11b. Diversity reception is performed (STEP 2). Then, it is confirmed whether or not the end of the receiving operation has been instructed. If the end of the receiving operation has not been instructed (No in STEP 3), the movement status estimating unit 42x in the receiving environment estimating unit 42 as described above. Then, the fluctuation amount D obtained from the difference value of the received power of the plurality of SP symbols is obtained (STEP 4).

  Further, as described above, the movement state estimation unit 42x compares the calculated fluctuation amount D with the threshold value Dth to estimate the movement state of the receiving device (STEP 5). At this time, when the fluctuation amount D is greater than or equal to the threshold value Dth, it is estimated that the receiving device is in a moving state, and when the amount of movement D is lower than the threshold value Dth, it is estimated that the receiving device is in a stopped state. Then, when it is estimated that the movement is based on the calculated fluctuation amount D (Yes in STEP 5), the process proceeds to STEP 2 where the power supply control unit 43 supplies power to both the RF signal processing units 11a and 11b. The operation after STEP3 is performed.

  Further, when it is estimated from the calculated fluctuation amount D that it is stopped (NO in STEP 5), the reception status estimation unit 42y in the reception environment estimation unit 42 demodulates the MPEG encoded signal as described above. Error rate E (corresponding to the bit error rate described above) is obtained (STEP 6). Further, as described above, the reception status estimation unit 42y compares the calculated error occurrence rate E with the threshold Eth to estimate the reception status of the reception device (STEP 7). At this time, if the error occurrence rate E is equal to or higher than the threshold Eth, it is estimated that the reception status of the receiving device is bad. If the error occurrence rate E is lower than the threshold Eth, the reception status of the receiving device is good. Estimated.

  When it is estimated that the reception status is worse than the calculated error occurrence rate E (No in STEP 7), the process proceeds to STEP 2, and the power supply control unit 43 supplies power to both the RF signal processing units 11a and 11b. The supply is kept as it is, and the operation after STEP3 is performed. In addition, when it is estimated that the reception status is good from the calculated error occurrence rate E (No in STEP 7), the diversity reception operation in which power is supplied to both the RF signal processing units 11a and 11b is being performed. It is confirmed whether or not there is (STEP 8).

  At this time, if the power supply control unit 43 confirms that the diversity reception operation is in progress (Yes in STEP 8), the reception status estimation unit 42y generates an error in the MPEG encoded signal from each of the digital demodulation units 15 and 15x. By comparing the rates, it is determined which of the reception systems of the antennas 10a and 10b is in good condition (STEP 9). Then, the power supply control unit 43 stops the power supply to the RF reception processing unit for the reception system determined to have good reception status in STEP 9 (STEP 10). That is, for example, when it is determined in STEP 9 that the reception status of the receiving system of the antenna 10a is good, power supply from the power supply control unit 43 to the RF reception processing unit 11b is stopped in STEP 10.

  In STEP 8, when the power supply from the power supply control unit 43 is only one RF reception processing unit and the reception operation by one system has already been performed (No), or in STEP 10, the power supply control unit When the power supply from 43 is switched to only one RF reception processing unit, a reception operation is performed by the reception system including the RF reception processing unit supplied with power from the power supply control unit 43 (STEP 11). As described above, when a reception operation by one reception system is performed in STEP 11, the process proceeds to STEP 3 and it is confirmed whether or not the end of the reception operation is instructed. Furthermore, when the end of the reception operation is instructed in STEP 3 (No), the power supply from the power supply control unit 43 to both the RF reception processing units 11a and 11b is stopped, and the reception operation ends.

  As described above, according to the present embodiment, when it is confirmed that the movement state estimation unit 42x is moving, a diversity reception operation is performed. Further, when it is confirmed that the movement status estimation unit 42x is stopped, the reception status estimation unit 42y further confirms whether or not the reception status is good. Stop the reception operation and switch to the reception operation by one system. In addition, when the reception operation by one system is being performed, if the movement state estimation unit 42x is moving or if the reception state estimation unit 42y confirms that the reception state has deteriorated, the operation returns to the diversity reception operation. can do.

  In the present embodiment, two types of diversity reception can be performed. However, as described above, three or more types of diversity reception may be performed. In addition, the Japanese ISDB-T system digital broadcasting has been described as an example, but another system such as the European DVB-T (Digital Video Broadcasting-Terrestrial) system may be used. Moreover, although the SP symbol is taken as an example of the pilot symbol, it can be realized by other pilot symbols such as a CP (Continual Pilot) symbol. Furthermore, not only in digital broadcasting but also in other digital communications, the above-described estimation of the reception environment can be realized by using a reference signal transmitted at regular intervals corresponding to pilot symbols.

  The present invention can be applied to a digital broadcast receiving apparatus that receives various digital broadcasts including terrestrial digital television, and in particular, a mobile terminal including a vehicle-mounted digital broadcast receiving apparatus and a mobile phone having a digital broadcast receiving function. It can be applied to devices.

These are block diagrams which show the internal structure of the receiver which becomes the basic composition of this invention. FIG. 4 is a diagram showing a relationship between pilot symbols and data symbols in an OFDM symbol sequence. These are figures which show transition of the reception power of SP symbol by the movement condition of a receiver. These are block diagrams which show the internal structure of the receiver in embodiment of this invention. These are the flowcharts which show the switching control of the receiving operation in the receiving apparatus of FIG.

Explanation of symbols

10, 10a, 10b Antenna 11, 11a, 11b RF signal processing unit 12, 12a, 12b FFT unit 13, 13a, 13b Equalization processing unit 14, 14a, 14b Demodulation unit 15, 15x Digital demodulation unit 16, 42 Reception environment estimation Unit 17 MPEG decoder 41 MRC synthesis unit 42 reception environment estimation unit 42x movement status estimation unit 42y reception status estimation unit 43 power supply control unit

Claims (8)

An antenna that receives a communication signal having a reference signal that serves as a reference when demodulating by reducing the influence of the transmission path, a demodulator that demodulates the communication signal received by the antenna, and a demodulator that demodulates the communication signal And a decoder for decoding the communication signal, and a receiver mounted on a mobile unit,
A reception environment estimation unit configured to estimate whether the moving body is in a moving state or a stopped state based on a temporal variation amount of the reference signal provided in the communication signal demodulated by the demodulation unit; A receiving apparatus. By configuring a plurality of receiving systems by providing a plurality of antennas and demodulation units, respectively,
When diversity reception for simultaneously operating the plurality of reception systems is performed, a communication signal demodulated by the plurality of demodulation units is combined, and a signal combining unit that outputs to the decoder is provided.
The diversity reception by the plurality of reception systems is performed when the reception environment estimation unit estimates that the amount of temporal variation of the reference signal is large and the moving body is in a moving state. Item 4. The receiving device according to Item 1. The reception environment estimation unit
A movement state estimation unit that estimates whether the moving body is in a moving state or a stopped state based on a temporal variation amount of the reference signal provided in the communication signal demodulated by the demodulation unit;
A reception situation estimation unit that estimates a reception situation by the antenna based on an error rate of a signal decoded by the decoder,
When the movement state estimation unit estimates that the amount of temporal fluctuation of the reference signal is small and the moving body is in a stopped state, the reception state estimation unit is further decoded by the decoder. When it is estimated that the signal error rate is small and the reception status by the antenna is good, the reception system that selects the best reception status is selected and the reception operation is performed by the one reception system. The receiving device according to claim 2. A power supply control unit for supplying power to the plurality of receiving systems;
The power supply controller is
When performing the diversity reception, supply power to all the reception systems,
The power supply to a receiving system other than the selected receiving system is stopped when performing a receiving operation by one receiving system selected from the plurality of receiving systems. The receiving device according to claim 3. The communication signal is configured by multiplexing a plurality of digitally modulated signals arranged at fixed frequency intervals,
The receiving apparatus according to any one of claims 1 to 4, wherein the reference signals are arranged at predetermined intervals in each of a time axis direction and a frequency axis direction.   The receiving apparatus according to claim 5, wherein the fluctuation amount of the reference signal is calculated based on a difference in received power between the reference signals arranged on the same frequency and adjacent on the time axis. In a reception environment estimation method for estimating a reception environment in a reception device that receives a communication signal including a reference signal that becomes a reference when demodulating by reducing the influence of a transmission path
A first step of calculating a temporal variation amount of the reference signal provided in the communication signal demodulated by the demodulator;
A second step of estimating whether the moving body on which the receiving device is mounted is in a moving state or a stopped state based on a temporal variation amount of the reference signal calculated in the first step;
A reception environment estimation method characterized by comprising: A reception environment estimation method for estimating a reception environment in the reception device including a plurality of reception systems,
A third step of calculating an error rate of the decoded communication signal;
A fourth step of estimating the reception status of the receiving device based on the error rate calculated in the third step;
Further comprising
In the second step, when it is estimated that the amount of temporal fluctuation of the reference signal is small and the moving body is in a stopped state, and in the fourth step, the error rate of the communication signal is 8. The reception environment according to claim 7, wherein when the reception condition by the antenna is estimated to be small, the reception apparatus selects one reception system with the best reception condition. Estimation method.

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