JP5483709B2 - Communication device and signal power measurement method - Google Patents

Description

  The present invention relates to a communication apparatus and a signal power measurement method for performing communication using an OFDMA (Orthogonal Frequency Division Multiple Access) method.

  In wireless communication, a received signal received by a communication device serving as a base station includes a signal from a desired terminal device and an interference signal from other terminal devices. In such a case, it is necessary to optimize the directivity of the antenna in order to eliminate the influence of the interference signal. Conventionally, the signal-to-noise power ratio (SNR) is measured, and the SNR is substantially maximized. The method of performing adaptive control is adopted.

  FIG. 10 is a block diagram showing a configuration of a conventional array antenna control apparatus disclosed in Patent Document 1. In FIG. As shown in FIG. 10, the array antenna control apparatus includes an array antenna apparatus 100 including one excitation element A0, six non-excitation elements A1 to A6, a radio receiver 10, and an adaptive control type controller. 20.

  Here, the transmitted radio signal is M-phase PSK modulated (M is an integer of 2 or more), and the adaptive control type controller 20 is configured by a digital computer such as a computer, for example, and is received by the excitation element A0 of the array antenna apparatus 100. Based on the received signal y (t), a first time average value for a predetermined time period is calculated for the M power of the conjugate complex number product of two received signals that are temporally adjacent to each other. The second time average value for the time period is calculated for the square of the M power of two received signals, and the calculated first time average value is divided by the calculated second time average value. A quotient that is a second moment functional value is calculated, and based on the calculated quotient, the SNR of the received signal is calculated using an expression that indicates the relationship between the higher order moment functional and the SNR.

  Then, the adaptive control type controller 20 adaptively controls the signal processing means, for example, the waveform equalizers 6-1 and 6-2 in FIG. 1, so that the calculated SNR is substantially maximized.

  An array antenna apparatus 100 shown in FIG. 10 includes an excitation element A0 and non-excitation elements A1 to A6 provided on a ground conductor 11, and the excitation elements A0 are provided on six circumferences having a radius r. It arrange | positions so that it may be enclosed by the non-excitation elements A1-A6.

  The feeding point of the excitation element A0 is connected to the low noise amplifier (LNA) 1 via the coaxial cable 8, and the non-excitation elements A1 to A6 are connected to the variable reactance elements 12-1 to 12-6, respectively. The reactance values of the reactance elements 12-1 to 12-6 are set by reactance value signals from the adaptive control type controller 20.

  In the array antenna control apparatus of FIG. 10, the excitation element A0 of the array antenna apparatus 100 receives the radio signal y (t), and the received signal y (t), which is the received radio signal, passes through the coaxial cable 8. Input to the radio receiver 10, the radio receiver 10 performs PSK demodulation processing on the received signal y (t) to obtain two digital baseband signals from the PSK demodulated received signals that are orthogonal to each other. . That is, in the radio receiver 10, the received signal y (t) is first subjected to high frequency amplification by the low noise amplifier (LNA) 1 and then divided into two, and one of the two divided received signals y (t) is mixed by the mixer 2-2. After being mixed with the local oscillation signal from the local oscillator 3 by 1, the I signal after direct conversion is input to the waveform equalizer 6-1.

  The I signal subjected to waveform equalization by the waveform equalizer 6-1 is A / D converted by the A / D converter 5-1, thereby obtaining a digital baseband I signal. On the other hand, the other received signal y (t) divided into two is mixed by the mixer 2-2 with the local oscillation signal phase shifted by 90 degrees from the local oscillation signal by the 90 degree phase shifter 4 and then directly. The Q signal after the conversion is input to the A / D converter 5-2 via the waveform equalizer 6-2 that performs the same operation as the waveform equalizer 6-1. Next, the waveform-equalized Q signal is A / D converted by the A / D converter 5-2 to obtain a digital baseband Q signal. These two digital baseband signals are output as data signals and also output to the adaptive control type controller 20.

JP 2004-254003 A

  In the array antenna apparatus described above, it is understood that the SNR is estimated from the error in the amplitude of the received signal, but this method has the following problems.

  That is, in a communication system using OFDMA such as XGP (Extended Global Platform), the amplitude of two received signals that are temporally adjacent to each other fluctuates greatly, so that it is difficult to estimate the SNR by the conventional method described above.

  In XGP, it is necessary to calculate the power of a desired wave for each terminal device and perform transmission power control. For each PRU (Physical Resource Unit: bandwidth 900 kHz) that is a channel allocation unit to the terminal device, It is necessary to estimate an interference power ratio (CIR). For this reason, since a signal in the frequency domain after FFT (Fast Fourier Transform) has to be used, a conventional method using a signal in the time domain cannot be used.

  The present invention has been made to solve the above-described problems. In a communication system using OFDMA such as XGP, reception including signal power from a desired terminal apparatus and interference power from an interference terminal is provided. It is an object of the present invention to provide a communication device and a signal power measurement method capable of detecting signal power from which interference power is eliminated from a signal.

  A communication device that performs communication using an OFDMA (Orthogonal Frequency Division Multiple Access) method, a wireless unit that outputs a reception signal received by an antenna, a baseband processing unit connected to the wireless unit, and the baseband processing unit And a power measurement processing unit that calculates a signal power obtained by eliminating interference power from the received signal, and the baseband processing unit is provided corresponding to the antenna and performs a Fourier transform on the received signal. A Fourier transform unit to be applied; a subchannel received power measuring unit that is connected to the radio unit and calculates and outputs a subchannel received power that is an absolute value of received power per subchannel; and a Fourier transform in the Fourier transform unit A correlation calculation unit that calculates a correlation value between a subsequent received signal and a reference signal in units of subchannels; and the correlation value calculated by the correlation calculation unit And a CIR estimation unit that estimates a CIR (signal power to interference power ratio) value, and the CIR estimation unit includes CIR information including a CIR value with respect to a correlation value in advance, and the CIR information The power measurement processing unit calculates the CIR value corresponding to the correlation value input using the CIR value and the subchannel received power output from the subchannel received power measuring unit. Based on this, the signal power is calculated.

  The signal power measurement method according to the present invention is a signal power measurement method in the case of performing communication by OFDMA (Orthogonal Frequency Division Multiple Access) method, the step (a) of performing a Fourier transform on the received signal received by the antenna, (B) calculating a correlation value between the received signal after Fourier transform and the reference signal in units of subchannels, and estimating a CIR (signal power to interference power ratio) value based on the calculated correlation value (c), calculating a subchannel received power that is an absolute value of received power per subchannel of the received signal, based on the CIR value and the subchannel received power, And (e) calculating a signal power obtained by removing interference power from the received signal, wherein the step (c) includes a CIR including a CIR value with respect to a correlation value prepared in advance. Calculating a value of the CIR corresponding to the correlation value using information.

  The communication device according to the present invention can detect signal power from a desired terminal device. Further, even if there is an amplitude variation in the subchannel due to frequency selective fading, the influence can be reduced. Also, CIR can be estimated for each subchannel.

  According to the signal power measurement method according to the present invention, it is possible to detect signal power from a desired terminal device. Further, even if there is an amplitude variation in the subchannel due to frequency selective fading, the influence can be reduced. Also, CIR can be estimated for each subchannel.

It is a figure which shows the flame | frame structure of XGP. It is a figure which shows the format of EXCH. It is a block diagram which shows the structure of the communication apparatus of embodiment which concerns on this invention. It is a figure explaining the measurement point of slot reception power in 1 slot. It is a flowchart explaining the signal power measuring method of embodiment which concerns on this invention. It is a flowchart which shows the algorithm of correlation value calculation. It is a figure which shows a correlation value-CIR conversion table. It is a figure which shows the characteristic curve of the correlation value with respect to the value of CIR calculated | required experimentally. It is a flowchart explaining the modification of the signal power measuring method of embodiment which concerns on this invention. It is a block diagram which shows the structure of the control apparatus of the conventional array antenna.

<Embodiment>
<Frame structure of XGP>
In XGP, in the same period as the current PHS, in the period of 5 msec per frame, the uplink (UL) and the downlink (DL) are time-divided by 2.5 msec each, and UL and DL are each divided into four times. Time-divided into slots.

  Here, FIG. 1 shows a frame configuration when each time slot is composed of nine subchannels.

  That is, as shown in FIG. 1, the uplink (UL) is time-divided into four slots 1 to 4, and the downlink (DL) is time-divided into four slots 5 to 8. The slot is composed of nine subchannels of subchannel 1 to subchannel 9. Here, one subchannel in one slot is called a PRU (Physical Resource Unit).

  As shown in FIG. 1, in the uplink, subchannel 1 in slot 1 is referred to as PRU1, subchannel 1 in slot 2 is referred to as PRU2, and thereafter the unit number is incremented by one. And subchannel 2 is assigned from PRU5 to PRU8. Hereinafter, unit numbers are assigned to slots 1 to 4 according to the same rule, and an uplink frame is composed of 36 PRUs from PRU1 to PRU36. A unit number is assigned to the downlink in the same manner, but is not shown.

  Each PRU is composed of 24 subcarriers and 19 OFDM symbols, and FIG. 2 shows a data channel format called EXCH (Extra Channel) as an example.

  In FIG. 2, subcarriers indicated by F1 to F24 in the vertical direction and OFDM symbols indicated by S1 to S19 in the horizontal direction are shown, and symbols S1 to S19 in F1 and F13 among the subcarriers are null symbols. Yes, used as a DC carrier or guard carrier, symbols S5, S9, S13 and S17 in subcarriers F3, F7, F11, F15, F19 and F24, respectively, are used as pilot symbols, and subcarriers F2 to F12, F14 to Symbol S1 in F24 is used as a training symbol, and symbols other than these are used as data symbols.

<Configuration of communication device>
FIG. 3 is a block diagram showing the configuration of the communication apparatus 1000 according to the present invention. As illustrated in FIG. 3, the communication apparatus 1000 includes an array antenna AT, a radio unit RF, a baseband processing unit BB, a demodulation processing unit 31, and a power measurement processing unit 32. In FIG. 3, only the reception unit is shown, and the illustration and description of the transmission unit are omitted.

  In communication apparatus 1000, a received signal received by array antenna AT is input to radio section RF, and radio section RF measures received power at received signal RXIF and a plurality of specific measurement points in one slot of the received signal. In this configuration, the received signal strength indication (RSSI) is given to the baseband processing unit BB.

  The baseband processing unit BB receives the reception signal RXIF that is an analog signal, converts the digital signal into a digital signal, and outputs the digital reception signal output from the ADC 21. The filter 22, the GI removal unit 23 that removes the guard interval (GI) from the filtered reception signal output from the filter 22, the FFT unit 24 that performs fast Fourier transform (FFT) on the reception signal after removing the GI, and FFT A sub-channel received power measuring unit 25 that measures a sub-channel received power that is an absolute value of received power per sub-channel based on the processed received signal and the slot received power not subjected to FFT processing; and FFT processing A correlation calculation unit 26 for receiving a later received signal and calculating a correlation value; And ADC20 give the sub-channel received power measuring unit 25 into a digital signal under the force has to correspond to the individual antennas constituting an array antenna AT. Note that FIG. 2 shows a configuration for two antennas.

  The FFT-processed received signal output from the FFT unit 24 is given to the demodulation processing unit 31 and subjected to predetermined demodulation processing, and converted into a signal that can be viewed by the user of the communication apparatus 1000. The absolute value of the received power measured by the subchannel received power measuring unit 25 is given to the power measurement processing unit 32 and used to calculate the received signal power from the desired terminal device, and the received signal that is the measurement target Is used for transmission power control of the terminal device that has transmitted.

  In the correlation calculation unit 26, the received signal received by each antenna is converted into a frequency domain signal through the ADC 21, the filter 22, the GI removal unit 23, the GI and FFT unit 24, and a training symbol portion (see FIG. ) And a reference signal prepared in advance and stored in the memory 30 is calculated and given to the selection unit 27.

  The selection unit 27 selects a value indicating the maximum value (maximum correlation value) from the correlation values obtained for each antenna and supplies the selected value to the CIR estimation unit 28. The CIR estimating unit 28 performs conversion from the correlation value to the CIR by using a conversion table indicating the CIR value with respect to the correlation value prepared in advance and stored in the memory 29. The CIR value obtained by the CIR estimating unit 28 is given to the power measurement processing unit 32, and the received signal from the desired terminal is calculated by the arithmetic processing with the subchannel received power output from each subchannel received power measuring unit 25. Used for power calculation.

  The FFT unit 24 shifts the amplitude value to be as large as possible within a range that does not exceed a certain threshold value in order to reduce the quantization error. Therefore, the absolute value of the received power is measured from the received signal after the FFT processing. Can not do it.

  However, in communication apparatus 1000, it is possible to measure the absolute value of the received power by giving the slot received power to subchannel received power measurement unit 25 without performing FFT processing. Hereinafter, the operation of the subchannel received power measuring unit 25 will be described.

<Subchannel received power measurement>
Since it is possible to perform processing for each subchannel by FFT processing, first, the subchannel received power measurement unit 25 calculates the relative received power value of each subchannel from the received signal after the FFT processing.

  That is, as shown in FIG. 2, each subchannel constituting one slot includes 24 pilot symbols, 6 in each of symbols S5, S9, S13, and S17. The sum of the squares of the I component (in-phase component) and Q component (quadrature phase component) is calculated and the total is calculated as the relative received power value rxpower (n) of the nth subchannel in one slot.

  This is calculated for each of the nine subchannels constituting one slot, and the sum of them is calculated as the sum Σrxpower of the relative received power values of all subchannels in one slot.

  Next, by dividing the relative received power value rxpower (n) of the subchannel by the addition value Σrxpower of the relative received power values of all the subchannels, one subchannel relative to the relative received power value of all the subchannels in one slot is obtained. The ratio of the relative received power value, that is, the relative power ratio is obtained.

  Next, an average value of the slot received power (RSSI) is obtained. Here, the slot received power is measured with respect to four symbol positions, and the measurement points of the slot received power in one slot are described with reference to FIG. To do.

  In FIG. 4, nine subchannels of subchannel 1 to subchannel 9 are shown in the vertical direction, and OFDM symbols S1 to S19 are shown in the horizontal direction, at the positions of symbols S1, S5, S9, S13, and S17. Are referred to as slot RSSI (1), slot RSSI (2), slot RSSI (3), slot RSSI (4) and slot RSSI (5), respectively. To do.

  In the radio unit RF, slot RSSI (1) to slot RSSI (5) are measured and given to the subchannel received power measuring unit 25 as slot received power.

The slot received power is given to the subchannel received power measuring unit 25 as an absolute value without passing through the FFT process, and the subchannel received power measuring unit 25 selects the slot RSSI from the slot RSSI (1) to the slot RSSI (5). Addition is performed for (2) to slot RSSI (5) to calculate an added value ΣRSSI _slot of the slot received power. Then, the average value (absolute value) of the slot received power is obtained by dividing the added value ΣRSSI _slot by the number of measurement points 4. By multiplying the average value of the slot received power by the previously obtained relative power ratio, the received power (absolute value) RSSI _PRU (n) of the nth subchannel in one slot can be obtained. RSSI _PRU (n) is the combined power of the desired wave and the interference wave.

Formula (1) for calculating the received power (absolute value) RSSI _PRU (n) of the nth subchannel in one slot as described above is shown below.

  In the above formula, each parameter is defined as follows.

RSSI _PRU (n): received power of the nth subchannel (PRU) in the _slot ΣRSSI _slot : added value of slot received power rxpower (n): relative received power value of the nth PRU in the slot Σrxpower: Addition value of relative received power value of all subchannels in one slot For example, by giving the relative received power value of the first subchannel to the above formula (1), the absolute value of the received power of the first subchannel is obtained. Can be sought.

  In addition, since the numerical formula (1) described above is expressed in decibels (dB), the logarithm is expressed so as to be multiplied by ten. When the numerical formula (1) is modified, the following numerical formula (2) is expressed. be able to.

  Thus, in communication apparatus 1000, the slot received power is given to subchannel received power measuring section 25 without performing FFT processing, and the relative received power of all subchannels in one slot calculated from the received signal after FFT processing. Since the absolute value of the received power of the subchannel can be obtained by multiplying the relative received power value ratio (relative power ratio) of one subchannel with respect to the value, the transmission power of the mobile terminal can be obtained based on the absolute value. Control is possible.

In the above example, the absolute value of the sub-channel received power is obtained from the slot received power. However, the absolute value is not limited to the slot received power. In short, the power of the interference wave and the power of the desired wave are The absolute value of the combined power may be obtained, and the absolute value of the combined power may be obtained by a well-known method and may be set as RSSI _PRU (n).

  In addition, since the relative power ratio is calculated using the received signal after the FFT processing, there is no influence even if the shift processing is performed so that the magnitude of the output signal becomes a certain value in the FFT unit 24. The increase in quantization error due to the absence of the shift process does not occur, and the communication apparatus 1000 can maintain high performance.

<Method for measuring signal power from desired terminal>
Next, the signal power measurement method according to the embodiment will be described with reference to FIG. 3 and the flowchart shown in FIG.

  When calculation of received signal power is started in FIG. 5, first, in step ST1, the received signal is converted into a frequency domain signal.

  Next, based on the received signal converted into the frequency domain signal, the correlation calculation unit 26 calculates a correlation value with the reference signal (step ST2).

  Here, a correlation value calculation algorithm for 1 PRU will be described with reference to the flowchart shown in FIG.

  When correlation value calculation is started in FIG. 6, various variables represented by A, B, and C are initialized to 0 (step ST11). Here, variable A is a complex number, and variables B and C are real numbers.

  Next, in step ST12, the number “i” of the subcarrier to be processed is set.

  Next, in step ST13, variables A, B, C, and D are calculated for subcarrier i. Here, the signal R (i) of the subcarrier “i” in the training symbol portion of the reference signal is added to the signal S (i) of the subcarrier i in the training symbol portion of the received signal (referred to as the received signal S (i)). ) (This is referred to as a reference signal R (i)) multiplied by a conjugate complex number conjR (i) is defined as a variable D, and the variable A is represented by A = A + D as an integrated value of the variable D.

  The variable B is an integrated value of the sum of the square of the real part of the received signal S (i) and the square of the imaginary part of the received signal S (i), and B = B + Re [S (i)] · Re [S (I)] + Im [S (i)] · Im [S (i)].

  The variable C is an integrated value of the sum of the square of the real part of the conjugate complex number conjR (i) of the reference signal R (i) and the square of the imaginary part of the conjugate complex number conjR (i) of the reference signal R (i). And C = C + Re [conjR (i)] · Re [conjR (i)] + Im [conjR (i)] · Im [conjR (i)].

  Note that the variables B and C are variables used to normalize the variable A represented by a complex number.

  When the calculation of the variables A to D described above for the subcarrier i is completed, it is confirmed whether or not the subcarriers to be processed remain in the PRU (step ST14), and when the subcarriers to be processed remain. Then, the process from step ST12 is repeated. On the other hand, if all the subcarriers to be processed have been processed, the process proceeds to step 5.

  In step ST15, a correlation value is calculated, where E = Re [A] · Re [A] + Im [, where E is the square of the real part of variable A, the square of the imaginary part of variable A, and the added value. A] · Im [A].

  Then, the correlation value corr is calculated by dividing the square root of the addition value E by the respective square roots of the variables B and C, and the correlation value calculation is terminated.

  Returning to the description of the flowchart of FIG. The correlation value calculation in step ST2 is executed for the reception signals received by the individual antennas constituting the array antenna AT, and in step ST3, it is confirmed whether the correlation values are calculated for the reception signals of all the antennas. . If there is an antenna for which the correlation value has not been calculated, the correlation value calculation in step ST2 is executed. If the correlation value is calculated for the reception signals of all antennas, the process proceeds to step ST4. move on.

  The correlation value calculated by each correlation calculation unit 26 is given to the selection unit 27, and the correlation value (maximum correlation value) indicating the maximum value is selected (step ST4).

  The maximum correlation value selected by the selection unit 27 is given to the CIR estimation unit 28, and the CIR estimation unit 28 prepares a conversion table (correlation value − The correlation value is converted into a CIR value using the CIR conversion table) (step ST5).

  FIG. 7 shows an example of the correlation value-CIR conversion table. In FIG. 7, CIR values are shown at intervals of 5 dB from −30 dB to 30 dB, and correlation values corresponding to the respective CIR values are shown. By using this correlation value-CIR conversion table, for example, if the correlation value selected by the selection unit 27 is 0.7594, for example, it can be seen that the CIR value is 0 dB. In the example of FIG. 7, the CIR values are shown at intervals of 5 dB. However, the present invention is not limited to this, and a table may be created according to the resolution of CIR estimation.

  The correlation value-CIR conversion table may be created based on the characteristic curve (characteristic data) of the correlation value with respect to the CIR value obtained experimentally. An example of this characteristic curve is shown in FIG.

  In FIG. 8, the horizontal axis indicates the CIR value (dB), and the vertical axis indicates the correlation value. The CIR value is changed by changing the signal power or the power of the interference wave, and the correlation value of the received signal at that time. It is obtained by calculating. FIG. 8 shows only a characteristic curve for one PRU, but in actual measurement, a characteristic curve is acquired for each PRU. In addition, all the characteristic curves are substantially the same, and they are expressed as an approximate expression by the following formula (3).

  In the above formula (3), y is a CIR value and x is a correlation value. However, the approximate expression is an expression applied in the range of 0.3 ≦ x ≦ 0.9, and x When x is greater than 0.9 (x> 0.9), approximation is performed with y = 10, and when x is smaller than 0.3 (x <0.3), approximation is performed with y = −20.

  Instead of the correlation value-CIR conversion table of FIG. 7, such an approximate expression may be used to convert the correlation value into a CIR value.

  Note that the above-described correlation value-CIR conversion table and its approximate expression are merely examples, and the present invention is not limited to these, and may be appropriately prepared according to the configuration of the communication apparatus.

Returning to the description of the flowchart of FIG. 5 again, after the correlation value is converted into the CIR value, the acquired CIR value and the absolute value RSSI of the received power for each subchannel calculated by the subchannel received power measuring unit 25. _{Using the PRU} , the received signal power PW is calculated based on the following equation (4) (step ST6).

In the above formula (4), when the CIR value is 0, the value of the first term on the right side is about −3 dB, and the received signal power PW is obtained by the sum of the RSSI _PRU value.

<Effect>
As described above, according to communication apparatus 1000 according to the embodiment, the correlation value with the reference signal is determined for each antenna for the training symbol part of the received signal converted into the frequency domain signal after the FFT processing. The CIR is estimated by converting the maximum correlation value among the acquired correlation values into a CIR value using a conversion table or an approximate expression indicating the CIR value for the correlation value prepared in advance, Since the received signal power PW is calculated using the obtained CIR value, it is possible to detect the power of the signal from a desired terminal device.

  In addition, since the CIR is estimated based on the correlation calculation with the reference signal, even if there is an amplitude fluctuation in the PRU due to frequency selective fading, the influence is small. Moreover, since the received signal after FFT processing is used, CIR can be estimated for every PRU.

<Modification>
In communication apparatus 1000 according to the embodiment described above, correlation values are calculated for all antennas, and the maximum correlation value among them is based on the characteristic curve of the correlation value with respect to the CIR value shown in FIG. In this example, the correlation value-CIR conversion table (FIG. 7) or the approximate expression of the characteristic curve is used to convert the values into CIR values. However, the calculation of correlation values for all antennas has a large processing load. The signal power measurement method may be modified as follows.

  FIG. 9 is a flowchart for explaining a modification of the signal power measuring method according to the present invention. The apparatus configuration is the same as that of the communication apparatus 1000 shown in FIG. 3, and will be described with reference to FIG.

When the calculation of the received signal power is started, first, in step ST21, the reception level at each antenna of the array antenna AT is calculated. The reception level value may be the average value of the slot reception power described above or the absolute value RSSI _PRU of the reception power for each subchannel.

  Next, in step ST22, the obtained reception levels of the individual antennas are compared, and the antenna having the maximum reception level is selected.

Next, in step ST23, the received signal at each antenna is converted into a signal in the frequency domain. In this process, when the absolute value RSSI _PRU of the received power for each subchannel is used as the value of the reception level in step ST21, a frequency domain signal is used for calculating the RSSI _PRU. Keep going.

  Next, a correlation value with the reference signal is calculated by the correlation calculation unit 26 based on the reception signal obtained by the antenna having the maximum reception level selected in step ST22 among the reception signals converted into frequency domain signals. (Step ST24).

  The above-described calculation of the reception level, selection of the antenna with the maximum reception level, and processing for selecting only the reception signal obtained with the antenna with the maximum reception level are the subchannels provided for each antenna. The reception power measurement unit 25 may perform this.

Next, it is determined whether or not the correlation value calculated in step ST24 is a value within a predetermined range set in advance. This determination may be performed, for example, in the selection unit 27. When there is only one correlation value given from the correlation calculation unit 26, the selection unit 27 does not select a correlation value but gives a given correlation. The function is switched so as to determine whether or not the value is within a predetermined range. If the given correlation value is a value within a predetermined range, the process proceeds to step ST25, where the correlation value is given to the CIR estimation unit 28, and a correlation value-CIR conversion table prepared in advance or an approximation is provided. The value is converted into a CIR value using the equation (step ST26). After the correlation value is converted into the CIR value, the mathematical expression described above is used by using the acquired CIR value and the absolute value RSSI _PRU of the received power for each subchannel calculated by the subchannel received power measuring unit 25. Based on (4), received signal power PW is calculated (step ST27).

  Here, the predetermined range of the correlation value used in step ST25 is set, for example, as 0.3 to 0.9 (0.3 or more and 0.9 or less). This range is set for the following reason.

  That is, if the characteristic curve shown in FIG. 8 is taken as an example, the change of the characteristic is gradual in the region where the correlation value is smaller than 0.3 and the region where the correlation value is larger than 0.9. The influence of the error on the CIR value is large. On the other hand, in the region where the correlation value is 0.3 to 0.9, the characteristics change suddenly, and the influence of the correlation value error on the CIR value is small. Therefore, when the correlation value takes a value within this region, it is assumed that the error of the correlation value does not become a problem even if the CIR estimation is performed only with the correlation value for one antenna having the maximum reception level, and the correlation value is calculated. Reduce processing load by reducing the number of antennas.

  Whether the change in characteristics is gradual or abrupt is determined when the characteristic change is gradual when the characteristic curve shows a characteristic whose slope is ½ or less of the maximum tangent. Then, the number of antennas for calculating the correlation value may be determined depending on whether or not the calculated correlation value is within the region indicating the characteristic. Note that the above threshold value of 1/2 or less is merely an example, and the present invention is not limited to this.

  On the other hand, when the correlation value calculated in step ST24 is a value outside the predetermined range, for example, when the correlation value is smaller than 0.3 or when the correlation value is larger than 0.9, the error of the correlation value is CIR. As a result, the process proceeds to step ST28, a correlation value is calculated for signals received by other antennas, and the process proceeds to step ST29. In step ST29, confirmation is made as to whether correlation values have been calculated for the received signals from all antennas. If there is an antenna for which the correlation value has not been calculated, the correlation value calculation of step ST28 is executed. If the correlation value is calculated for the reception signals of all antennas, the process proceeds to step ST30. move on.

In step ST30, an average value of correlation values obtained with respect to reception signals from all antennas is calculated, and the average value is converted into a CIR value (step ST26). Next, the acquired CIR value, Using the absolute value RSSI _PRU of the received power for each subchannel calculated by the subchannel received power measuring unit 25, the received signal power PW is calculated based on the equation (4) described above (step ST27). Note that the process of calculating the average correlation value in step ST30 may be performed in the selection unit 27.

  In this way, the reception level at each antenna of the array antenna AT is calculated, the antenna with the maximum reception level is selected, and the reception value at the antenna is converted into a frequency domain signal to calculate the correlation value. Thus, when the influence of the calculated correlation value on the CIR value is small, the number of antennas for calculating the correlation value is reduced by performing CIR estimation using only the correlation value for one antenna. Processing load can be reduced.

  In the above description, calculation of received signal power using an array antenna has been described. However, the present invention is also effective in calculating received signal power using a single antenna.

23 power measurement processing unit 24 Fourier transform unit 25 subchannel received power measurement unit 26 correlation calculation unit 28 CIR estimation unit RF radio unit BB baseband processing unit

Claims (2)

A communication device that performs communication using an OFDMA (Orthogonal Frequency Division Multiple Access) method, a wireless unit that outputs a received signal received by an antenna;
A baseband processing unit connected to the radio unit;
A power measurement processing unit that is connected to the baseband processing unit and calculates signal power obtained by eliminating interference power from the received signal, and
The baseband processing unit
A Fourier transform unit that is provided corresponding to the antenna and performs a Fourier transform on the received signal, and calculates and outputs subchannel received power that is connected to the radio unit and is an absolute value of received power per subchannel. A sub-channel received power measuring unit, a correlation calculating unit for calculating a correlation value between the received signal after the Fourier transform in the Fourier transform unit and the reference signal, in sub-channel units,
A CIR estimating unit that estimates a value of CIR (signal power to interference power ratio) based on the correlation value calculated by the correlation calculating unit,
The CIR estimation unit includes:
CIR information including a CIR value with respect to a correlation value is prepared in advance, and the CIR value corresponding to the correlation value input using the CIR information is calculated.
The communication apparatus, wherein the power measurement processing unit calculates the signal power based on the CIR value and the subchannel received power output from the subchannel received power measuring unit. A signal power measurement method in the case of performing communication by OFDMA (Orthogonal Frequency Division Multiple Access) method,
(a) performing a Fourier transform on the received signal received by the antenna;
(b) calculating a correlation value between the received signal after the Fourier transform and the reference signal in units of subchannels;
(c) estimating a value of CIR (signal power to interference power ratio) based on the calculated correlation value;
(d) calculating subchannel received power that is an absolute value of received power per subchannel of the received signal;
(e) calculating a signal power obtained by eliminating interference power from the received signal based on the CIR value and the subchannel received power; and
The step (c)
A method for measuring signal power, comprising: calculating the CIR value corresponding to the correlation value using CIR information including a CIR value for a correlation value prepared in advance.

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