JP2009150819A - Receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving apparatus capable of estimating speech quality even when information regarding transmission bands and modulation methods are not known at a receiving end. <P>SOLUTION: A receiving apparatus according to the present invention includes: a frequency domain converting section 11 for converting a received signal into a frequency-domain signal; an averaging process section 12 for averaging the frequency-domain signal by frequency and time; a signal band calculating section 13 for determining the signal band of the received signal in accordance with a result of the averaging; a signal power calculating section 14 for calculating signal power in accordance with the value of power within the signal band; a noise power calculating section 15 for calculating noise power in accordance with the value of power within a predetermined range outside of the signal band; and an SNR calculating section 16 for estimating speech quality in accordance with the signal power and the noise power. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a receiving apparatus that estimates communication quality of a received radio signal.

  As conventional communication quality estimation methods, for example, methods described in Patent Document 1 and Patent Document 2 below have been proposed. In the following Patent Document 1 and Patent Document 2, assuming that the transmission rate (transmission band) and modulation method are known on the receiving side, SNR (signal power to noise power ratio) is estimated as communication quality. Specifically, in Patent Document 1 below, first, a receiving apparatus estimates an original signal based on a transmission frequency detected by sampling and quantizing a received FSK signal. Then, the noise component is analyzed from the difference between the received FSK signal and the original signal, and the SNR is estimated using the original signal level and the noise component level. Also, in Patent Document 2 below, the receiving apparatus obtains the value of the higher-order moment functional by a predetermined calculation based on the conjugate complex number of two M-phase PSK modulation reception signals that are temporally adjacent. Then, the SNR is estimated using a relational expression between the higher-order moment functional and the SNR.

Japanese Patent Laid-Open No. 07-162353 JP 2004-254003 A

  However, the above-described conventional technique has a problem that the SNR cannot be estimated when information on the transmission rate (transmission band) and the modulation method is not known. In particular, in a receiving apparatus compatible with a plurality of communication systems, it is necessary to select a communication system and receive a signal. Therefore, it is necessary to estimate communication quality even when there is no information.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a receiving apparatus capable of estimating communication quality even when information regarding a transmission band and a modulation scheme is not known.

  In order to solve the above-described problems and achieve the object, a receiving apparatus according to the present invention includes frequency domain conversion means for converting a received signal into a frequency domain signal, and averaging the frequency domain signal in frequency and time. Averaging means, signal band determining means for determining a signal band of a received signal based on the result of the averaging, signal power calculating means for calculating signal power based on a power value in the signal band, Noise power calculation means for calculating noise power based on a power value in a predetermined range outside the signal band, and communication quality estimation means for estimating communication quality based on the signal power and the noise power. To do.

  According to the present invention, there is an effect that the communication quality can be automatically estimated on the receiving device side even when the information such as the transmission band and the modulation method is unknown.

  Embodiments of a receiving apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a diagram illustrating a configuration example of a receiving apparatus according to the present invention. This receiving apparatus includes an antenna 1, a receiving unit 2, and an SNR estimating unit 3.

  The receiving unit 2 performs processing such as band limitation, down-conversion, analog / digital conversion, etc., on the analog signal received by the antenna 1 and outputs an intermediate frequency or baseband received signal converted into a digital signal. . It is not always necessary to downconvert to an accurate baseband. The SNR estimation unit 3 estimates the SNR of the reception signal output from the reception unit 2.

  FIG. 2 is a diagram illustrating a configuration example of the SNR estimation unit 3. The SNR estimation unit 3 includes a frequency domain conversion unit 11, an averaging processing unit 12, a signal band calculation unit 13, a signal power calculation unit 14, a noise power calculation unit 15, and an SNR calculation unit 16.

  The frequency domain transform unit 11 performs an operation such as discrete Fourier transform or fast Fourier transform on the received signal, and transforms the received signal into a frequency domain power spectrum. Note that the conversion to the frequency domain is performed by dividing the received signal into blocks at regular intervals, as shown in FIG. The longer the received signal block, the higher the frequency resolution, but conversely increases the processing amount. Therefore, the length of the block is set to a length (10 times or more) that can sufficiently secure the resolution of the signal having the slowest transmission rate among the modulation signals that may be received.

  As shown in FIG. 3, the averaging processing unit 12 averages the power spectrum output from the frequency domain conversion unit 11 for each power of the same frequency. Furthermore, as shown in FIG. 4, averaging is performed in a certain frequency range (moving average in the frequency direction). As a result, a highly accurate power spectrum can be calculated while suppressing variations due to noise and the like. FIG. 3 is a diagram illustrating how the frequency domain conversion unit 11 and the averaging processing unit 12 perform processing. FIG. 4 is a diagram illustrating how the averaging processing unit 12 performs moving average in the frequency direction.

  The signal band calculation unit 13 uses α times (for example, 1/2 times) the maximum power (Pmax) of the power spectrum smoothed by the averaging process as a threshold value, and sets a frequency band equal to or higher than the threshold value. Signal bandwidth. Then, the left and right frequencies FL and FR of the signal band are output to the signal power calculation unit 14 and the noise power calculation unit 15. FIG. 5 is a diagram illustrating an example of a power spectrum. Note that α is set to be about ½ of the maximum power having an appropriate signal bandwidth when the waveform is shaped by the Nyquist filter. However, it is also possible to set a value slightly shifted from ½, assuming the case of waveform shaping using a noise spread or other than a Nyquist filter.

  The signal power calculation unit 14 detects the maximum power value in the range of FL to FR in the signal band, and sets the value as the signal power (see FIG. 5).

  The noise power calculator 15 detects the minimum power (Pmin) in the range of FL−W × β to FL and FR to FR + W × β outside the signal band, and uses the value as noise power ( (See FIG. 5). Here, W is FR-FL. Also, β is set so as to include a band that is not affected by the spread of the signal component (for example, β = 1).

  The SNR calculator 16 calculates the ratio between the signal power output from the signal power calculator 14 and the noise power output from the noise power calculator 15, and outputs the calculation result as the SNR.

  As described above, in this embodiment, the receiving apparatus estimates the transmission band of the received signal and calculates the SNR based on the result. Thereby, even if information such as a transmission band and a modulation method is unknown, the SNR can be calculated as the communication quality. If the configuration of this embodiment is used, the SNR can be calculated without distinguishing not only the digital modulation method but also the analog modulation method.

  Further, in this embodiment, averaging processing is performed in the frequency domain to suppress spectrum distortion due to noise. Thereby, since an accurate spectrum can be calculated in a short time, highly accurate communication quality can be calculated in a short estimation time.

  The noise power calculation unit 15 can also calculate noise power by the following procedure. For example, the power of the frequency domain signal output from the averaging processing unit 12 is averaged on the frequency axis, and the signal component is excluded when θ times the average value is a threshold value (for example, θ = 0.1). Value). And the value which averaged the frequency component lower than this threshold value is made into noise power. As described above, the averaging accuracy can be further increased by using many samples.

  Further, the noise power calculation unit 15 averages the noise power calculated a plurality of times, so that the noise power calculation accuracy can be further improved. Note that the number of times of averaging needs to be such a number that fluctuations in noise power due to automatic gain control (AGC) of the receiver can be ignored.

  As described above, the receiving apparatus according to the present invention is useful when the transmission band and the modulation method are unknown on the receiving side, and is particularly suitable as a receiving apparatus compatible with a plurality of communication systems.

It is a figure which shows the structural example of the receiver concerning this invention. It is a figure which shows the structural example of a SNR estimation part. It is a figure which shows the mode of a process of a frequency domain conversion part and an averaging process part. It is a figure which shows the mode of the moving average of the frequency direction by an averaging process part. It is a figure which shows an example of a power spectrum.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Receiving part 3 SNR estimation part 11 Frequency domain conversion part 12 Averaging process part 13 Signal band calculation part 14 Signal power calculation part 15 Noise power calculation part 16 SNR calculation part

Claims (5)

A frequency domain converting means for converting a received signal into a frequency domain signal;
Averaging means for averaging the frequency domain signal in frequency and time;
Signal band determining means for determining a signal band of a received signal based on the result of the averaging;
Signal power calculating means for calculating signal power based on a power value in the signal band;
Noise power calculation means for calculating noise power based on a predetermined range of power values outside the signal band;
Communication quality estimation means for estimating communication quality based on the signal power and the noise power;
A receiving apparatus comprising:   The receiving apparatus according to claim 1, wherein the signal power calculation unit uses the maximum value of power in the signal band as signal power.   The receiving apparatus according to claim 1, wherein the predetermined range outside the signal band is a range that includes a band adjacent to the signal band and not affected by the spread of the signal component.   4. The receiving apparatus according to claim 1, wherein the noise power calculation means uses a minimum value of power in a predetermined range outside the signal band as noise power.   The noise power calculation means averages the averaged signal power on a frequency axis, obtains a threshold value indicating a power value not including a signal component based on the average value, and a frequency component lower than the threshold value The receiving apparatus according to claim 1, wherein an average value of the noise power is a noise power.

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