JPWO2014192732A1 - Radio station, radio signal measuring method, and computer program - Google Patents

Abstract

Correlation suppression unit (104), which is a radio station including a plurality of antennas (101) each receiving a desired wave and an undesired wave, and suppresses the correlation of undesired waves between signal sequences received by each antenna. And an in-phase synthesis unit (106) for synthesizing the signal sequence in phase with the desired wave included in the signal sequence after correlation suppression, and power estimation for estimating the received power of the desired wave using the signal sequence after in-phase synthesis Part (107).

Description

  The present invention relates to a radio station, a radio signal measurement method, and a computer program that can be used to implement the method.

  Cognitive radio that recognizes the surrounding radio environment and optimizes communication parameters according to the radio environment is known. As an example of cognitive radio, for example, a secondary system (interfering system) can share a frequency band assigned to a primary system (interfered system).

  For example, IEEE (Institute of Electrical and Electronic Engineers) 802.22 uses a frequency band (TV channel) assigned to a TV broadcast system as a primary system, and a wireless regional area network (WRAN) system as a secondary system. Standard specifications for sharing are defined.

  The WRAN system uses a spectrum sensing technique that determines whether a frequency band is being used by a primary system. Here, spectrum sensing refers to reception processing in which a secondary system receives radio waves in a shared frequency band and recognizes whether a primary system signal (primary signal) exists. By performing spectrum sensing, it is possible to grasp the usage status of surrounding frequencies, and the secondary system can use frequencies that are not used by the primary system in the surroundings.

  Non-Patent Document 1 discloses a spectrum sensing method using a cognitive radio equipped with a plurality of antennas. This method is applied to a primary signal having cyclic stationarity. First, by calculating the frequency autocorrelation value (Spectral Auto-correlation) for the received signal of a single antenna and the frequency cross-correlation value (Spectral Cross-correlation) for the received signal of multiple antennas, the primary signal is compared. Estimates the phase difference of the transmission path when arriving at each antenna of the cognitive radio. Then, using the phase difference, the received signals of the respective antennas are subjected to equal gain combining (Equal Gain Combining), and then the primary signal is detected. The primary signal detection with improved signal-to-noise ratio (SNR) of the primary signal is performed by combining signals received by multiple antennas with equal gain.

  On the other hand, knowing how much interference (the amount of interference) is given to the receiving station (primary receiving station) of the primary system by transmitting from the transmitting station (secondary transmitting station) of the secondary system It is important in sharing the frequency. If the amount of interference given to the primary receiving station by the signal transmitted from the secondary transmitting station (secondary signal) can be grasped, the transmission power of the secondary system can be adjusted so that the influence of interference on the primary receiving station can be suppressed below a certain level. .

  In Non-Patent Document 2, in order to grasp the interference with the primary receiving station, a sensor station (described as a secondary system receiving station (secondary receiving station) in the vicinity of the primary receiving station) It shows a method of estimating the interference state of the primary receiving station by measuring the reception level of the secondary signal and the reception level of the primary signal.

  FIG. 6 is a schematic diagram of a system in which the interference state of the primary receiving station is estimated by the sensor station. In the figure, the primary receiving station 11 exists in the coverage 12 of the primary transmitting station 10. The secondary transmission station 20 performs transmission by sharing the same frequency at a distance from the coverage 12 of the primary transmission station 10, and has a coverage 21. The sensor station 30 is located around the primary receiving station 11. The sensor station 30 estimates the interference state of the primary receiving station 11 by measuring both the reception level of the secondary signal and the reception level of the primary signal.

  Normally, the secondary transmission station 20 transmits with adjusted transmission power in order to suppress interference with the primary reception station 11. Therefore, in the sensor station 30 located around the primary receiving station 11, the level of the secondary signal is relatively small compared to the level of the primary signal. Therefore, the sensor station 30 must measure the secondary signal while a relatively large primary signal exists in the same band. Therefore, focusing on the measurement of the secondary signal, the secondary signal is treated as a desired wave and the primary signal is treated as an undesired wave below.

FIG. 7 is a schematic diagram showing that a secondary signal (desired wave) transmitted from the secondary transmitting station 20 and a primary signal (undesired wave) transmitted from the primary transmitting station 10 arrive at each antenna of the sensor station 30. It is. The received signal x _m (n) of the m-th antenna of the sensor station 30 is expressed by the following equation using an equivalent low-frequency representation (Complex Equivalent form) of the baseband signal.

Here, n represents a sample number of the received signal, s (n) is a secondary signal that is a desired wave, z (n) is an undesired wave, and w _m (n) is a noise signal. The transmission path between the transmission antenna of the secondary transmission station 20 and the m-th antenna of the sensor station 30 is h _{S, m} , and the transmission path between the transmission antenna of the primary transmission station 10 and the m-th antenna of the sensor station 30 is h _{Z and m} are used. That is, the first term h _{S, m} s (n) of the equation [1] is the desired reception wave, and the second term h _{Z, m} z (n) is the undesired reception wave.

Xu Wenjun, He Zhiqiang Q., Tao Xiaofeng, “Spectral correlation-based multi-antenna spectrum sensing technique,” Proc. IEEE Wireless Communications and Networking Conference (WCNC), April 2008. Kazushi Muraoka, Hiroto Sugawara, Masayuki Ariyoshi, “Examination of White Space Secondary Use Cognitive Radio System (3) —Advanced Spectrum Control Based on Interference Monitoring”, IEICE Society Conference, B-17-2, 2010 September

  When the sensor station 30 measures the level of the secondary signal using the measurement technique described in Non-Patent Document 1, there are the following problems.

The same undesired wave z (n) is mixed in the received signal x _m (n) of the m-th antenna shown in the equation [Equation 1] in any antenna. For this reason, cross-correlation of reception undesired waves between antennas occurs. This is because the cross-correlation values R _{x1 and x2} of the received signals of the first antenna and the second antenna are expressed by the following equation, and the cross-correlation value h _{Z, 1} (h _{Z, 2} ) ^* Z of the reception undesired wave between the antennas. This can also be confirmed from the fact that

Here, N is the number of samples used to calculate the cross-correlation, * is the complex conjugate, S is the average received power of the desired wave signal, and Z is the average received power of the undesired wave signal. In this way, when the cross-correlation of the received undesired waves is generated between the antennas, when the received signals of a plurality of antennas are combined using the technique described in Non-Patent Document 1, the undesired wave component in the combined signal is May increase. That is, measurement of the desired reception wave is hindered.

  The present invention has been made to solve the above-described problem, and can provide a radio station, a radio signal measurement method, and a computer program capable of accurately measuring a reception level of a desired wave in an environment where an undesired wave exists. The purpose is to provide.

  The radio station of the present invention is a radio station that includes a plurality of antennas each receiving a desired wave and an undesired wave, and suppresses correlation of undesired waves between signal sequences received by each antenna. An in-phase synthesizing unit that synthesizes the signal sequence in phase with the desired wave included in the signal sequence after correlation suppression, and a power estimation unit that estimates received power of the desired wave using the signal sequence after in-phase synthesis .

The radio signal measurement method of the present invention is a radio signal measurement method used in a radio station provided with a plurality of antennas each receiving a desired wave and an undesired wave, and is a non-signal between signal sequences received by each antenna. A correlation suppression step for suppressing the correlation of the desired wave, an in-phase synthesis step for synthesizing the signal sequence with the desired wave included in the signal sequence after the correlation suppression, and a signal sequence after the in-phase synthesis using the signal sequence after the in-phase synthesis. And a power estimation step for estimating received power.

The program according to the present invention is a program for measuring a radio signal used in a radio station having a plurality of antennas each receiving a desired wave and an undesired wave. A correlation suppression function that suppresses the correlation of undesired waves, an in-phase synthesis function that combines the desired signal included in the signal sequence after correlation suppression with the signal sequence, and a desired signal using the signal sequence after in-phase synthesis And a power estimation function for estimating the received power.

  According to the present invention, it is possible to accurately measure the reception level of a desired wave in an environment where undesired waves exist.

It is a block diagram which shows the structural example of the sensor station in embodiment of this invention. It is a block diagram which shows another structural example of the sensor station in embodiment of this invention. It is a figure which shows the time arrangement | positioning of a transmission stop area. It is a figure which shows the measurement zone | band for the cross correlation production | generation of a reception undesired wave. It is a flowchart which shows operation | movement of the sensor station in embodiment of this invention. 2 is a schematic diagram of a system that estimates an interference state of a primary system at a sensor station 30. FIG. 4 is a schematic diagram showing that a desired wave and an undesired wave arrive at a plurality of antennas of a sensor station 30. FIG.

DESCRIPTION OF SYMBOLS 10 Primary transmitting station 11 Primary receiving station 12 Primary transmitting station coverage 20 Secondary transmitting station 21 Secondary transmitting station coverage 30 Sensor station 100 Sensor station 101, 101-1, 101-2 Receiving antenna 102, 102-1, 102-2 RF signal processing unit 103 Received undesired wave cross-correlation generating unit 104 Received undesired wave cross-correlation suppressing unit 105 Inter-sequence phase difference estimating unit 106 In-phase combining unit 107 Desired signal power estimating unit 108 Network communication unit

[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration example of a sensor station (hereinafter also referred to as a radio station) 100 according to the first embodiment of the present invention.

  The sensor station 100 according to the present invention is assumed to be a sensor that measures an interference situation and a signal arrival situation when the primary system and the secondary system share the frequency. Of course, the above is merely an example, and may be a wireless sensor for other purposes, one of the primary system radio stations (base station, relay station, terminal), the secondary system radio station (base station, It may be one of relay stations and terminals. The sensor station 100 measures the reception level of a desired wave (for example, a secondary signal) in an environment where undesired waves (for example, a primary signal) exist in the same frequency band.

  Moreover, although a TV broadcast system can be considered as an example of the primary system, and a cellular system, a wireless LAN, and the like can be considered as examples of the secondary system, the primary system and the secondary system are not limited to these systems.

  The sensor station 100 includes a reception antenna 101 (101-1, 101-2), an RF (Radio Frequency) signal processing unit 102 (102-1, 102-2), a reception undesired wave cross-correlation generation unit 103, a reception undesired A wave cross-correlation suppression unit 104, an inter-sequence phase difference estimation unit 105, an in-phase synthesis unit 106, a desired wave power estimation unit 107, and a network communication unit 108.

  As the receiving antenna 101, two antennas (101-1, 101-2) are illustrated in FIG. 1 as an example, but may be any M antennas. The sensor station 100 receives a reception signal including a desired wave and an undesired wave by each of the reception antennas 101-1 and 101-2.

  The RF signal processing unit 102 (102-1, 102-2) performs amplification processing using a low noise amplifier, band limiting processing using a band pass filter that limits transmission / reception of radio waves outside a desired frequency band, and RF received by the receiving antenna 101. A process of converting the frequency of the signal into a baseband signal and a process of A / D conversion (Analog to Digital conversion) of the baseband signal are performed. The generated digital baseband reception signal is output to reception undesired wave cross-correlation generation unit 103 and reception undesired wave cross-correlation suppression unit 104.

  The reception undesired wave cross-correlation generation unit 103 generates a cross-correlation value of reception undesired waves between the antennas using the digital baseband reception signals input from the RF signal processing units 102-1 and 102-2. To do.

  Next, a method for obtaining the cross-correlation value of the reception undesired wave between the antennas without being influenced by the desired wave will be described.

  First, FIG. 3 shows a configuration in the case where a secondary signal that is a desired wave includes a transmission stop period (Quiet Period). The configuration of the desired wave in FIG. 3 is a configuration in which short transmission stop intervals are periodically inserted. By providing a transmission stop section in advance in the secondary signal, it becomes an environment where only the primary signal and the thermal noise signal that are undesired waves are received within that section, which can be used to grasp the cross-correlation of the received undesired waves. .

  On the other hand, FIG. 4 exemplifies the power spectrum density when a narrow band desired wave is used in the secondary system compared to the bandwidth of the undesired wave. In the case of such a bandwidth configuration in advance, a band pass filter is set for measuring the cross-correlation of the received undesired wave at a frequency outside the desired wave band and within the undesired wave band. By receiving in this way, it becomes an environment where only the primary signal and the thermal noise signal which are undesired waves are received, which can be useful for grasping the cross-correlation of the received undesired waves.

  The cross-correlation of the received undesired waves can be grasped by using either the transmission stop period of FIG. 3 or the bandwidth configuration of FIG. However, when the transmission stop period of FIG. 3 is used, it is necessary to time-synchronize with the transmission stop period of the secondary signal. When the bandwidth configuration of FIG. 4 is used, it is outside the band of the desired wave and within the band of the undesired wave. It is necessary to be able to set a band pass filter in FIG. 1, but the configuration necessary for these is omitted in FIG. Below, the structure of the secondary signal with a transmission stop area as shown in FIG. 3 is assumed, and the cross-correlation value of the reception undesired wave is generated using this.

  Since the reception signal in the transmission stop period includes only the undesired wave and thermal noise, the cross-correlation value of the reception signal between the antennas can be calculated to obtain the cross-correlation of the reception undesired wave. However, in order to simplify subsequent processing, the reception undesired wave cross-correlation generation unit 103 generates a correlation matrix of reception undesired waves. Here, a vector summarizing the reception signals of all M antennas is defined by the following equation.

Here, ^T represents transposition. By using the formula of [Expression 3], the correlation matrix of the received non-desired wave can be expressed by the following equation R _u.

Here, N _QP is the number of samples in the transmission stop period, and ^H represents complex conjugate transposition. In the correlation matrix R _u of the received undesired wave, the non-diagonal component is the cross-correlation value of the received undesired wave. For example, the cross-correlation value between the received non-desired wave reception undesired wave of the first antenna and the second antenna is a first row and second column of elements R _u of R _{u (1,2).} On the other hand, the diagonal component is the reception power of each antenna in the transmission stop period, and corresponds to the sum of the power of the reception undesired wave and the thermal noise power. For example, the received power of the second antenna is a second row and second column of the element _R u of _{R u} (2,2). The reception undesired wave cross-correlation generation unit 103 also obtains reception power of each antenna in order to generate a correlation matrix. The reception undesired wave cross-correlation generation unit 103 outputs the correlation matrix of the reception undesired wave to the reception undesired wave cross-correlation suppression unit 104.

  The reception undesired wave cross-correlation suppression unit 104 uses the input reception undesired wave correlation matrix to convert the digital baseband reception signal sequence in the transmission section into a sequence in which the cross-correlation of reception undesired waves between antennas is suppressed. The signal sequence after the suppression processing is output to the inter-sequence phase difference estimation unit 105 and the in-phase synthesis unit 106.

First, the received undesired wave cross-correlation suppressing unit 104 performs eigenvalue decomposition on the correlation matrix R _u of the received undesired wave. If the eigenvalue matrix of R _u is Λ and the unitary matrix composed of eigenvectors is U, eigenvalue decomposition of R _u can be expressed by the following equation.

Next, the reception undesired wave cross-correlation suppressing unit 104 transmits the transmission period (N _QP ≦ n ≦ N _QP + N _ON −1 after the transmission stop period, where N _ON is the number of samples of the received signal sequence in the transmission period. ) Received signal sequence x (n) is converted by the following equation using unitary matrix U.

Here, x ′ (n) is an M × 1 vector representing the M sequences after the conversion process, and is represented by the following equation.

Note that x _m ′ (n) is the m-th signal sequence after the conversion process. When the received signal of each antenna is expressed as in [Expression 1], since the processing of [Expression 6] is linear transformation, x _m ′ (n) can be expressed in the form of the following expression. it can.

Here, h ′ _{S, m} is a coefficient related to a desired wave of the m-th signal sequence, h ′ _{Z, m} is a coefficient related to an undesired wave of the m-th signal sequence, and h ′ _{W, m} is related to a noise signal of the m-th signal sequence. It is a coefficient. The phase difference of a desired wave between series described later means a phase difference of h ′ _{S, m} between different series.

  By converting the received signal sequence with the eigenvector of the correlation matrix of the received undesired wave using the equation of [Equation 6], it is possible to prevent the received undesired wave components included between the new signal sequences from having a correlation. . That is, in the new signal sequence, the cross-correlation of the received undesired waves is suppressed. The signal sequence after the suppression process obtained in this way is output to the inter-sequence phase difference estimation unit 105 and the in-phase synthesis unit 106 after the suppression process.

  The inter-sequence phase difference estimation unit 105 estimates the phase difference of the desired wave between the signal sequences for the different signal sequences after the suppression process, and outputs the phase difference to the in-phase synthesis unit 105.

First, the inter-sequence phase difference estimation unit 105 uses the samples in the transmission interval for the first signal sequence and the m-th signal sequence after the suppression processing, as shown in the following equation, and the cross-correlation value R _{1, m} between the sequences. Is generated.

Since the cross-correlation of the reception undesired wave has already been suppressed, the equation of [Equation 9] is the cross-correlation of the reception desired wave component. For this reason, the phase component of the equation of [Equation 9] corresponds to the phase difference regarding the desired wave of the first signal sequence and the m-th signal sequence after the suppression process. The phase component e ^{jθ1, m in} the equation (9) can be obtained by the following equation.

  Here, | · | represents the absolute value of a complex number. The processing of the equations of [Equation 9] and [Equation 10] is performed for all sequences (2 ≦ m ≦ M) other than the first signal sequence, and the phase difference of each sequence with respect to the first signal sequence is the same phase. The data is output to the combining unit 106.

  The in-phase synthesizing unit 106 synthesizes the input signal sequence after the conversion process after converting it with the phase difference of each sequence with respect to the first signal sequence. That is, equal gain synthesis is performed as follows.

  Here, y (n) is a signal sequence obtained by in-phase synthesis. However, it is normalized by the number of antennas M at the time of in-phase synthesis. By performing in-phase synthesis, the received desired wave component is emphasized and the SNR of the received desired wave is improved. Further, in this process, since there is no correlation regarding the reception undesired wave between the signal sequences to be combined, the reception undesired wave component is not amplified after the combination. The combined signal sequence obtained in this way is output to desired wave power estimation section 107.

  The desired signal power estimation unit 107 estimates the received power of the desired signal using the input combined signal sequence, and outputs it to the network communication unit 108.

  There are various methods for estimating the received power of the desired wave in the desired wave power estimation unit 107. For example, a method using a pilot signal of a desired wave or a method using the periodic stationarity of a desired wave can be considered. Here, a method of the following equation using the received power of the combined signal sequence will be described.

Here, S ′ is an estimated value of desired wave power. In addition, the first term of the equation of [Equation 12] is the power of the combined signal sequence in the transmission section, in other words, the combined desired wave power, the combined undesired wave power, and the combined heat. This is equivalent to the sum of noise power. The second term is a value obtained by averaging the undesired wave power and the thermal noise power before the suppression processing with each antenna. Note that R _u (m, m) is an element of m rows and m columns of the correlation matrix of the received undesired wave in the equation [4], and is the total power of the undesired wave and thermal noise received by the mth antenna. It corresponds to.

  Here, since the cross-correlation suppression processing of the reception undesired wave of the equation [6] uses unitary conversion, power is stored before and after the conversion. Further, the in-phase synthesis of the equation [11] is also a process for preserving power because it is equal gain synthesis. That is, in both the unitary conversion and equal gain combining processes, the sum of the undesired wave power and thermal noise power before and after the process is stored. Therefore, the value of the second term is equal to the sum of the undesired wave power after synthesis and the thermal noise power after synthesis included in the breakdown of the first term.

  For the above reasons, by subtracting the second term from the first term, the undesired signal power and noise power can be removed from the power of the entire combined signal sequence, and the desired signal power after synthesis can be calculated easily. The desired wave power thus obtained is output to the network communication unit 108.

  The network communication unit 108 transmits the information on the desired wave power to an external device that requires information via a wired network or a wireless network. As an example of an external device that requires information on desired wave power, there is a spectrum manager (not shown) that manages frequency use of a secondary system. The spectrum manager adjusts the transmission power of the secondary transmission station and changes the frequency being used based on the desired wave power (that is, the secondary signal power) estimated by the sensor station 100. Of course, the spectrum manager may use the secondary signal power information for other purposes. The spectrum manager is sometimes called a geo-location database or a white space database. Of course, the use of the desired wave power information is not limited to the external device, and the sensor station 100 may use the desired wave power information.

  The received undesired wave cross-correlation suppressing unit 104 may include the function of the received undesired wave cross-correlation generating unit 103, and the in-phase combining unit 106 may include the function of the inter-sequence phase estimating unit 105. A configuration example in this case is shown in FIG. In FIG. 2, the RF signal processing unit 102 and the network communication unit 108 are not shown.

  FIG. 5 is a flowchart illustrating an operation example of the sensor station 100. In the sensor station 100, the RF signal received by the antenna is amplified by a low noise amplifier, the band is limited by a band-pass filter that limits radio waves outside the desired frequency band, and the RF signal is converted into a baseband signal. A / D conversion is performed after frequency conversion to a digital baseband signal (step S10).

  Next, the cross-correlation value of the reception undesired wave is generated using the reception signal in the section where the transmission of the desired wave is stopped (step S11). At this time, the correlation matrix of the reception undesired wave is generated by generating the reception undesired wave of each antenna and the power value of the thermal noise together. By using the correlation matrix of the received undesired waves, the received signal sequence of each antenna is converted into a signal sequence in which the cross-correlation of the received undesired waves between the sequences is suppressed (step S12).

  Next, the phase difference between the signal sequences after the suppression process is estimated (step S13). In-phase synthesis by equal gain synthesis is performed on each signal sequence after the suppression processing by performing phase rotation using the phase difference between the sequences and performing synthesis (step S14). Finally, the desired signal power is estimated using the in-phase combined signal sequence (step S15).

  According to the first embodiment described above, unlike the non-patent document 1 in which the received signals for each antenna are in-phase combined in a state where the cross-correlation of the received undesired waves is generated between the antennas, By generating and using correlation values in advance, a signal sequence that does not cause cross-correlation of received undesired waves between sequences is generated, and the phase difference of the desired wave is estimated between the sequences and combined in phase. Thus, in-phase synthesis can be performed without increasing undesired wave components. That is, the power of the desired reception wave can be estimated with high accuracy.

[Second Embodiment]
A feature of the second embodiment of the present invention is that a system different from the first embodiment is adopted for the inter-sequence phase difference estimation unit 105 of the sensor station 100. For the sake of clarity, the description of the same configuration as that of the second embodiment is omitted.

In the second embodiment, the inter-sequence phase difference estimation unit 105 estimates the phase difference related to the desired wave between sequences using the periodic steadiness of the desired wave. Here, the periodic stationarity is a property in which the autocorrelation function of the signal becomes a periodic function. Cyclic stationarity is seen in OFDM (Orthogonal Frequency Division Multiplexing) with cyclic prefix inserted, SC-FDMA (Single Carrier-Frequency Division Multiple Access), and signals in which pilot signals are inserted repeatedly or at regular intervals. Is the nature. When the desired wave s (n) is periodically stationary, a cyclic autocorrelation function (CAF) R ^α _s (τ) of the following equation shows a peak periodically.

Here, α represents the cyclic frequency, τ represents the sampling number corresponding to the delay time, Δt represents the sampling interval, and N represents the average number. For example, when s (n) is an OFDM signal, a peak occurs at a cyclic frequency of 1 / Ts (Ts is an OFDM symbol length obtained by combining a guard interval and an effective symbol length). In the OFDM signal, the peak of the periodic autocorrelation function is maximized when τ is equal to the effective symbol length.

Next, a method for estimating the phase difference between sequences using the periodic steadiness of the desired wave will be described. First, the periodic autocorrelation value R ^α _{X, m} (τ) for the m-th signal sequence x _m ′ (n) after the suppression processing of the equation of [Equation 6] is calculated by the following equation.

However, with sample number N _ON of the transmission period as the averaging number. Further, h ′ _{S, m} is a coefficient related to the desired wave of the m-th signal sequence in the equation [Equation 8]. Here, since the periodic autocorrelation value R ^α _{X, m} (τ) related to the signal sequence after the suppression processing includes the periodic autocorrelation value R ^α _s (τ) of the desired wave, the desired wave has the maximum peak. In the cyclic frequency α and the delay time τ shown, the formula [Equation 14] also shows a peak. For this reason, since the desired wave component becomes larger than other undesired wave components and noise components included in the signal sequence after the suppression processing, only the periodic autocorrelation value of the desired wave is obtained as shown in [Equation 14]. Can be approximated.

Subsequently, a periodic cross-correlation value R ^α _{X, 1, m} (τ) between the first signal sequence and the m-th signal sequence is calculated by the following equation.

Here, in the same way as the formula [14], the formula [15] also shows a peak at the cyclic frequency α and the delay time τ at which the desired wave has the maximum peak. Therefore, since the desired wave component becomes larger than other undesired wave components and noise components included in the signal sequence after the suppression processing, the equation of [Equation 15] is approximated only by the periodic autocorrelation value of the desired wave component. it can.

Therefore, if the equations of [Equation 14] and [Equation 15] are used, the phase difference relating to the desired wave of the first signal sequence and the m-th signal sequence, that is, between h ′ _{S, 1} and h ′ _{S, m.} The phase difference can be expressed by the following equation.

  In this way, the phase difference of the desired wave between sequences is estimated by using the periodic autocorrelation value and the periodic cross-correlation value. The above processing is performed for all sequences (2 ≦ m ≦ M) other than the first signal sequence, and the phase difference of each sequence with respect to the first signal sequence is calculated.

  In the second embodiment described above, the phase difference of the desired wave between sequences is estimated using the periodic stationarity of the desired wave. More specifically, the phase difference was estimated using the cyclic autocorrelation value for the signal sequence after the suppression processing and the periodic cross-correlation value between different signal sequences after the suppression processing. This phase estimation is effective when the cross-correlation of undesired received waves between different antennas cannot be completely suppressed. In such a case, if the phase difference is estimated using the cross-correlation value between different signal sequences after suppression processing as in the equation [9], the cross-correlation component of the received undesired wave that has not been completely suppressed is obtained. This is an error of phase difference estimation. On the other hand, in the inter-sequence phase difference estimation method of the present embodiment, phase difference estimation can be performed in a state where the undesired wave component is made smaller than the desired wave component by utilizing the periodic steadiness of different desired waves. Therefore, it is possible to reduce an estimation error due to the fact that the suppression of the cross correlation of the received undesired wave is not complete.

  In the first and second embodiments described above, it is also possible to add a process for adaptively determining whether or not to execute a cross-correlation suppression process for a reception undesired wave. For example, the absolute value of the off-diagonal component (that is, the cross-correlation value of the received undesired wave between antennas) represented by the equation [Equation 4] and the diagonal of the correlation matrix Compare the components (that is, the sum of the received undesired wave power and noise power for each antenna). If the former is much smaller than the latter, the cross-correlation suppression process is not applied and the conventional in-phase synthesis is applied. You may add the process of switching to. By incorporating such processing, cross-correlation suppression using a correlation matrix that includes errors when the received undesired wave is smaller than the noise power and the cross-correlation effect of the received undesired wave between antennas is small. It is possible to avoid an increase in error due to the processing.

  In the first and second embodiments described above, the primary system and the secondary system may be different RATs (Radio Access Technology) or the same RAT. Examples of different RATs include, for example, a combination of a TV broadcast system and a cellular system as described above. As an example of the same RAT, for example, the primary system may be a macro cell and the secondary system may be a femto cell installed therein.

  The first and second embodiments described above can also be embodied as predetermined hardware, for example, a circuit. For example, the above radio station can be realized by hardware, software, or a combination thereof. Further, the radio signal measurement method performed by the radio station can also be realized by hardware, software, or a combination thereof. Here, “realized by software” means realized by a computer reading and executing a program.

  The first and second embodiments described above can be controlled and operated by a computer circuit (for example, a CPU (Central Processing Unit)) (not shown) based on a control program. In this case, these control programs are stored in, for example, a storage medium (for example, a ROM (Read Only Memory) or a hard disk) in the apparatus or the system, or an external storage medium (for example, a removable medium or a removable disk). And read and executed by the computer circuit.

  The program may be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-ROMs. R, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  This application is based on Japanese Patent Application No. 2013-112108 (filed on May 28, 2013), and claims the priority of the Paris Convention based on Japanese Patent Application No. 2013-112108. The disclosure of Japanese Patent Application No. 2013-112108 is incorporated herein by reference to Japanese Patent Application No. 2013-112108.

  Although exemplary embodiments of the present invention have been described in detail, various changes, substitutions and alternatives may be made without departing from the spirit and scope of the invention as defined in the claims. It should be understood that this is done. Moreover, even if the claim is amended in the application procedure, the inventor intends that the equivalent scope of the claimed invention is maintained.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
A radio station having a plurality of antennas each receiving a desired wave and an undesired wave,
A correlation suppression unit that suppresses correlation of undesired waves between signal sequences received by each antenna;
An in-phase synthesizer for synthesizing the signal sequence with the desired wave included in the signal sequence after correlation suppression in phase;
A power estimator that estimates the received power of the desired wave using the signal sequence after in-phase synthesis;
A radio station comprising:

(Appendix 2)
The supplementary note 1 is characterized in that the correlation suppression unit converts a received signal sequence into a signal sequence in which the correlation of undesired waves between sequences is suppressed based on a cross-correlation value of undesired waves received by different antennas. The listed radio station.

(Appendix 3)
The radio station according to appendix 2, wherein the correlation suppression unit uses a correlation matrix of undesired waves received by each antenna as the cross-correlation value.

(Appendix 4)
The radio station according to appendix 3, wherein the correlation suppression unit converts a received signal sequence using an eigenvector of a correlation matrix of the undesired wave.

(Appendix 5)
5. The radio station according to appendix 4, wherein the correlation suppression unit unitarily transforms a received signal sequence using a unitary matrix composed of eigenvectors of the correlation matrix of the undesired wave.

(Appendix 6)
The cross-correlation value of undesired waves received by the different antennas is calculated using a received signal sequence received in a transmission stop period set for the desired wave. Radio stations.

(Appendix 7)
The cross-correlation value of the undesired wave received by the different antenna is calculated using the received signal that is outside the band of the desired wave and received through the band-pass filter set in the band of the undesired wave. The radio station according to any one of appendices 2 to 5, characterized in that:

(Appendix 8)
A phase difference estimator for estimating a phase difference of a desired wave between sequences for the signal sequence after correlation suppression, and the in-phase synthesis unit after correlation suppression using the phase difference estimated by the phase difference estimator; The radio station according to any one of appendices 1 to 7, wherein the signal sequence is synthesized in phase.

(Appendix 9)
9. The radio station according to appendix 8, wherein the phase difference estimation unit estimates an inter-sequence phase difference of a desired wave using cross-correlation values for different signal sequences after the correlation suppression.

(Appendix 10)
The phase difference estimation unit estimates a phase difference between sequences of a desired wave using a periodic autocorrelation value of the signal sequence after the correlation suppression and a periodic cross-correlation value of the signal sequence after the correlation suppression. The radio station according to appendix 8.

(Appendix 11)
The power estimation unit calculates the received power of the desired wave by subtracting the sum of the received power of the undesired waves of all antennas from the received power of the signal sequence after the in-phase synthesis. The radio station according to any one of 10.

(Appendix 12)
A radio signal measurement method used in a radio station having a plurality of antennas each receiving a desired wave and an undesired wave,
A correlation suppression step for suppressing correlation of undesired waves between signal sequences received by each antenna;
An in-phase synthesis step of synthesizing the signal sequence in phase with the desired wave included in the signal sequence after correlation suppression;
A power estimation step for estimating the received power of the desired wave using the signal sequence after in-phase synthesis;
A wireless signal measuring method comprising:

(Appendix 13)
Appendix 12 characterized in that, in the correlation suppression step, the received signal sequence is converted into a signal sequence in which the correlation of undesired waves between sequences is suppressed based on a cross-correlation value of undesired waves received by different antennas. The radio signal measuring method described.

(Appendix 14)
14. The radio signal measurement method according to appendix 13, wherein in the correlation suppression step, a correlation matrix of undesired waves received by each antenna is used as the cross-correlation value.

(Appendix 15)
15. The radio signal measurement method according to appendix 14, wherein in the correlation suppression step, a received signal sequence is converted using an eigenvector of the correlation matrix of the undesired wave.

(Appendix 16)
16. The radio signal measurement method according to appendix 15, wherein in the correlation suppression step, the received signal sequence is unitarily transformed using a unitary matrix composed of eigenvectors of the correlation matrix of the undesired wave.

(Appendix 17)
The cross-correlation value of undesired waves received by the different antennas is calculated using a received signal sequence received in a transmission stop period set for the desired wave. Wireless signal measurement method.

(Appendix 18)
The cross-correlation value of the undesired wave received by the different antenna is calculated using the received signal that is outside the band of the desired wave and received through the band-pass filter set in the band of the undesired wave. The wireless signal measurement method according to any one of supplementary notes 13 to 16, wherein

(Appendix 19)
A phase difference estimation step for estimating a phase difference of a desired wave between sequences with respect to the signal sequence after correlation suppression; and after the correlation suppression using the phase difference estimated in the phase difference estimation step in the in-phase synthesis step 19. The radio signal measurement method according to any one of appendices 12 to 18, wherein the signal series is in-phase synthesized.

(Appendix 20)
20. The radio signal measurement method according to appendix 19, wherein in the phase difference estimation step, the inter-sequence phase difference of the desired wave is estimated using cross-correlation values for different signal sequences after the correlation suppression.

(Appendix 21)
In the phase difference estimating step, a phase difference between sequences of a desired wave is estimated using a periodic autocorrelation value of the signal sequence after the correlation suppression and a periodic cross-correlation value of the signal sequence after the correlation suppression. The radio signal measuring method according to appendix 19.

(Appendix 22)
In the power estimation step, the received power of the desired wave is calculated by subtracting the sum of the received powers of the undesired waves of all the antennas from the received power of the signal sequence after the in-phase synthesis. 21. The radio signal measuring method according to any one of 21.

(Appendix 23)
A radio signal measurement program used in a radio station having a plurality of antennas each receiving a desired wave and an undesired wave,
On the computer,
A correlation suppression function for suppressing the correlation of undesired waves between signal sequences received by each antenna;
In-phase synthesis function for synthesizing the signal sequence with the desired wave included in the signal sequence after correlation suppression in phase,
A power estimation function that estimates the received power of the desired signal using the signal sequence after in-phase synthesis;
A program characterized by realizing.

(Appendix 24)
The supplementary note 23 is characterized in that the correlation suppression function converts a received signal sequence into a signal sequence in which a correlation of undesired waves between sequences is suppressed based on a cross-correlation value of undesired waves received by different antennas. The listed program.

(Appendix 25)
25. The program according to appendix 24, wherein the correlation suppression function uses a correlation matrix of undesired waves received by each antenna as the cross-correlation value.

(Appendix 26)
The program according to claim 25, wherein the correlation suppression function converts a received signal sequence using an eigenvector of a correlation matrix of the undesired wave.

(Appendix 27)
27. The program according to appendix 26, wherein the correlation suppression function unitarily transforms a received signal sequence using a unitary matrix composed of eigenvectors of the correlation matrix of the undesired wave.

(Appendix 28)
Any one of appendices 24 to 27, wherein the cross-correlation value of the undesired wave received by the different antenna is calculated using a received signal sequence received in the transmission stop period set to the desired wave. Program.

(Appendix 29)
The cross-correlation value of the undesired wave received by the different antenna is calculated using the received signal that is outside the band of the desired wave and received through the band-pass filter set in the band of the undesired wave. 28. The program according to any one of appendices 24 to 27, wherein

(Appendix 30)
The computer further realizes a phase difference estimation function for estimating a phase difference of a desired wave between sequences for a signal sequence after correlation suppression, and the in-phase synthesis function calculates a phase difference estimated by the phase difference estimation function. 30. The program according to any one of appendices 23 to 29, wherein the program is used for in-phase synthesis of the signal series after correlation suppression.

(Appendix 31)
The program according to appendix 30, wherein the phase difference estimation function estimates a phase difference between sequences of a desired wave using cross-correlation values for different signal sequences after the correlation suppression.

(Appendix 32)
The phase difference estimation function estimates an inter-sequence phase difference of a desired wave using a periodic autocorrelation value of the signal sequence after the correlation suppression and a periodic cross-correlation value of the signal sequence after the correlation suppression. The program according to Supplementary Note 30.

(Appendix 33)
The power estimation function calculates the received power of a desired wave by subtracting the sum of the received power of undesired waves of all antennas from the received power of the signal sequence after the in-phase synthesis. 32. The program according to any one of 32.

  The present invention can be used for measurement of a radio signal in a radio station such as a base station, a relay station, or a terminal, and can be used for, for example, cognitive radio.

Claims (33)

A radio station having a plurality of antennas each receiving a desired wave and an undesired wave,
A correlation suppression unit that suppresses correlation of undesired waves between signal sequences received by each antenna;
An in-phase synthesizer for synthesizing the signal sequence with the desired wave included in the signal sequence after correlation suppression in phase;
A power estimator that estimates the received power of the desired wave using the signal sequence after in-phase synthesis;
A radio station comprising:   2. The correlation suppression unit converts a received signal sequence into a signal sequence in which a correlation of undesired waves between sequences is suppressed based on a cross-correlation value of undesired waves received by different antennas. The radio station described in 1.   The radio station according to claim 2, wherein the correlation suppression unit uses a correlation matrix of undesired waves received by each antenna as the cross-correlation value.   The radio station according to claim 3, wherein the correlation suppression unit converts a received signal sequence using an eigenvector of a correlation matrix of the undesired wave.   5. The radio station according to claim 4, wherein the correlation suppression unit performs unitary transform on the received signal sequence using a unitary matrix composed of eigenvectors of the correlation matrix of the undesired wave.   6. The cross-correlation value of undesired waves received by the different antennas is calculated using a received signal sequence received in a transmission stop period set as a desired wave. The radio station described in 1.   The cross-correlation value of the undesired wave received by the different antenna is calculated using the received signal that is outside the band of the desired wave and received through the band-pass filter set in the band of the undesired wave. The radio station according to claim 2, wherein the radio station is a radio station.   A phase difference estimator for estimating a phase difference of a desired wave between the sequences for the signal sequence after the correlation suppression, wherein the in-phase synthesizer uses the phase difference estimated by the phase difference estimator to suppress correlation; The radio station according to any one of claims 1 to 7, wherein a later signal sequence is subjected to in-phase synthesis.   The radio station according to claim 8, wherein the phase difference estimation unit estimates an inter-sequence phase difference of a desired wave using cross-correlation values for different signal sequences after the correlation suppression.   The phase difference estimation unit estimates a phase difference between sequences of a desired wave using a periodic autocorrelation value of the signal sequence after the correlation suppression and a periodic cross-correlation value of the signal sequence after the correlation suppression. The radio station according to claim 8.   The said power estimation part calculates the received power of a desired wave by subtracting the sum total of the received power of the undesired wave of all the antennas from the received power of the signal sequence after the in-phase synthesis. The radio station according to any one of 1 to 10. A radio signal measurement method used in a radio station having a plurality of antennas each receiving a desired wave and an undesired wave,
A correlation suppression step for suppressing correlation of undesired waves between signal sequences received by each antenna;
An in-phase synthesis step of synthesizing the signal sequence in phase with the desired wave included in the signal sequence after correlation suppression;
A power estimation step for estimating the received power of the desired wave using the signal sequence after in-phase synthesis;
A wireless signal measuring method comprising:   13. The received signal sequence is converted into a signal sequence in which the correlation of undesired waves between sequences is suppressed based on a cross-correlation value of undesired waves received by different antennas in the correlation suppression step. The radio signal measuring method according to 1.   The radio signal measurement method according to claim 13, wherein in the correlation suppression step, a correlation matrix of undesired waves received by each antenna is used as the cross-correlation value.   15. The radio signal measurement method according to claim 14, wherein in the correlation suppression step, a received signal sequence is converted using an eigenvector of a correlation matrix of the undesired wave.   The radio signal measurement method according to claim 15, wherein in the correlation suppression step, the received signal sequence is unitarily transformed using a unitary matrix composed of eigenvectors of the correlation matrix of the undesired wave.   17. The cross-correlation value of undesired waves received by the different antennas is calculated using a received signal sequence received in a transmission stop period set as a desired wave. The radio signal measuring method according to 1.   The cross-correlation value of the undesired wave received by the different antenna is calculated using the received signal that is outside the band of the desired wave and received through the band-pass filter set in the band of the undesired wave. The wireless signal measurement method according to claim 13, wherein the wireless signal measurement method is a wireless signal measurement method.   A phase difference estimation step for estimating a phase difference of a desired wave between sequences with respect to the signal sequence after correlation suppression; and after the correlation suppression using the phase difference estimated in the phase difference estimation step in the in-phase synthesis step The radio signal measurement method according to claim 12, wherein in-phase synthesis of the signal series is performed.   The radio signal measurement method according to claim 19, wherein in the phase difference estimation step, a phase difference between sequences of a desired wave is estimated using cross-correlation values for different signal sequences after the correlation suppression.   In the phase difference estimating step, a phase difference between sequences of a desired wave is estimated using a periodic autocorrelation value of the signal sequence after the correlation suppression and a periodic cross-correlation value of the signal sequence after the correlation suppression. The radio signal measurement method according to claim 19.   13. The received power of a desired wave is calculated by subtracting the sum of the received power of undesired waves of all antennas from the received power of the signal sequence after the in-phase combining in the power estimation step. The radio signal measurement method according to any one of items 1 to 21. A radio signal measurement program used in a radio station having a plurality of antennas each receiving a desired wave and an undesired wave,
On the computer,
A correlation suppression function for suppressing the correlation of undesired waves between signal sequences received by each antenna;
In-phase synthesis function for synthesizing the signal sequence with the desired wave included in the signal sequence after correlation suppression in phase,
A power estimation function that estimates the received power of the desired signal using the signal sequence after in-phase synthesis;
A program characterized by realizing.   24. The correlation suppression function converts a received signal sequence into a signal sequence in which a correlation of undesired waves between sequences is suppressed based on a cross-correlation value of undesired waves received by different antennas. The program described in.   25. The program according to claim 24, wherein the correlation suppression function uses a correlation matrix of undesired waves received by each antenna as the cross-correlation value.   The program according to claim 25, wherein the correlation suppression function converts a received signal sequence using an eigenvector of a correlation matrix of the undesired wave.   27. The program according to claim 26, wherein the correlation suppression function unitarily transforms a received signal sequence using a unitary matrix composed of eigenvectors of the correlation matrix of the undesired wave.   28. The cross-correlation value of undesired waves received by the different antennas is calculated using a received signal sequence received in a transmission stop period set for the desired wave. The program described in.   The cross-correlation value of the undesired wave received by the different antenna is calculated using the received signal that is outside the band of the desired wave and received through the band-pass filter set in the band of the undesired wave. The program according to any one of claims 24 to 27, wherein:   The computer further realizes a phase difference estimation function for estimating a phase difference of a desired wave between sequences for a signal sequence after correlation suppression, and the in-phase synthesis function calculates a phase difference estimated by the phase difference estimation function. 30. The program according to any one of claims 23 to 29, wherein the program is used for in-phase synthesis of a signal sequence after correlation suppression.   The program according to claim 30, wherein the phase difference estimation function estimates an inter-sequence phase difference of a desired wave using cross-correlation values for different signal sequences after the correlation suppression.   The phase difference estimation function estimates an inter-sequence phase difference of a desired wave using a periodic autocorrelation value of the signal sequence after the correlation suppression and a periodic cross-correlation value of the signal sequence after the correlation suppression. The program according to claim 30.   The said power estimation function calculates the received power of a desired wave by subtracting the sum total of the received power of undesired waves of all antennas from the received power of the signal sequence after the in-phase synthesis. 33. The program according to any one of thru 32.