Test system and maximum Doppler frequency calculation method

Abstract

To provide a test system and a maximum Doppler frequency calculation method with which it is possible to estimate a maximum Doppler frequency by taking into account an impact of a mobile body, etc. in an actual propagation path environment.SOLUTION: A test system 1 includes: an actual propagation path estimate characteristic calculation unit 21 for calculating an estimate characteristic of a propagation path characteristic at a plurality of pieces of analysis object timing of an analysis object channel among one or more channels constituting an actual propagation path; and a parameter calculation unit 22 for calculating the maximum Doppler frequency of an analysis object channel as a parameter that characterizes a statistical nature of the estimate characteristic of the propagation path characteristic. The parameter calculation unit 22 includes a maximum Doppler frequency estimation unit 22c for estimating, as a maximum Doppler frequency, a maximum frequency greater than or equal to defined power among the frequency components of a quasi-Doppler spectrum of the analysis object channel.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a test system and a method for calculating the maximum Doppler frequency, which is a parameter of a channel model. [Background technology]

[0002] When testing a mobile phone terminal, the demodulation performance in a fading environment is evaluated by passing the downlink signal output from a base station simulator through a propagation path simulator and supplying the signal to the mobile radio terminal. The channel model used in the propagation path simulator is often one defined specifically for testing. However, there is also a demand for evaluating the demodulation performance of a mobile phone terminal using a channel model with propagation path characteristics closer to the actual propagation path environment.

[0003] As described in Table B.2.2-1 of Annex B.2.2 of 3GPP (registered trademark) TS38.521-4 in Non-Patent Document 1, the conformance test standard for mobile phone terminals specifies the maximum Doppler frequency f d is supposed to use a predetermined value.

[0004] In a development test environment, the user may define the channel model parameters themselves to configure a propagation path model. In a general channel model, the maximum Doppler frequency f d Let v be the moving speed of the mobile phone terminal and f be the carrier frequency of the signal received by the mobile phone terminal. c The value calculated by (f d =vf c / c) is used (c is the speed of light). According to this calculation, when the moving speed v is zero, the maximum Doppler frequency f d also becomes zero. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP TS38.521-4 V16.12.0, June 2022 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when observing the propagation path characteristics in an actual propagation environment, even if the moving speed v of the mobile phone terminal is zero, the maximum Doppler frequency f d is not zero. This is because in an actual propagation environment, even if the mobile phone terminal is stationary, there are many moving objects around, and the mobile phone terminal receives reflected waves from these objects. In other words, the maximum Doppler frequency f d as vf c When using / c, there was a problem that it was not possible to estimate a realistic maximum Doppler frequency when the influence of moving objects in the surrounding environment could not be ignored.

[0007] The present invention has been made to solve the above-mentioned problems in the related art, and has as its object to provide a test system and a method for calculating the maximum Doppler frequency that can estimate the maximum Doppler frequency in a manner that takes into account the influence of moving objects and the like in an actual propagation path environment. [Means for solving the problem]

[0008] In order to solve the above problem, a test system according to the present invention uses IQ data of a downlink signal transmitted from a transmission / reception device (100) on the network side and output from an antenna device (10) that receives the downlink signal in an environment of a real propagation path (110), and calculates estimated characteristics H^ at multiple analysis target timings of the propagation path characteristics of a target channel among one or more channels that make up the real propagation path. n ij (k), and an actual propagation path estimation characteristic calculation unit (21) for calculating the estimated characteristic H^ n ijand a parameter calculation unit (22) that calculates the maximum Doppler frequency of the analysis target channel as a parameter that characterizes the statistical properties of (k), wherein the parameter calculation unit calculates the estimated characteristic Ĥ n ij (k) is converted from the time domain characteristic showing the time change for each subcarrier to the frequency domain characteristic G k ij (f), and a domain transformation unit (22a) for transforming the frequency domain characteristic G k ij The configuration includes a quasi-Doppler spectrum calculation unit (22b) that calculates the quasi-Doppler spectrum of the analysis target channel by adding up the power spectrum for each subcarrier of (f) for K of the subcarriers, and a maximum Doppler frequency estimation unit (22c) that estimates, as the maximum Doppler frequency, the maximum frequency that is equal to or greater than a specified power among the frequency components of the quasi-Doppler spectrum of the analysis target channel.

[0009] With this configuration, the test system according to the present invention can estimate the maximum Doppler frequency of the analysis target channel while taking into account the influence of moving objects and the like in the actual propagation path environment.

[0010] In addition, the test system according to the present invention uses IQ data of a downlink signal output from an antenna device (10) that receives a downlink signal transmitted from a transmission / reception device (100) on the network side in an environment of a real propagation path (110), and calculates estimated characteristics H^ at a plurality of timings to be analyzed of the propagation path characteristics of a channel to be analyzed among one or more channels that constitute the real propagation path. n ij (k) and an actual propagation path estimation characteristic calculation unit (21) for calculating the analysis target timing t n (n is an integer between 0 and N-1) n ij (k) from the analysis target timing t n The impulse response g of the analyzed channel in n ij(m), and an impulse response calculation unit (23) for calculating the estimated characteristic H^ n ij As a parameter characterizing the statistical properties of (k), the impulse response g n ij and a parameter calculation unit (24) for calculating the maximum Doppler frequency of the analysis target channel from (m), wherein the parameter calculation unit is configured to calculate a delay tap τ m (m is an integer between 0 and M-1) n ij (m) is converted from the time domain characteristic showing the time change for each delay tap into the frequency domain characteristic F m ij (f), and a domain transformation unit (24a) for transforming the frequency domain characteristic F m ij The configuration includes a Doppler spectrum calculation unit (24b) that calculates the Doppler spectrum of the analysis target channel by adding up the power spectrum for each delay tap of (f) for M delay taps, and a maximum Doppler frequency estimation unit (24c) that estimates, as the maximum Doppler frequency, the maximum frequency that is equal to or greater than a specified power among the frequency components of the Doppler spectrum of the analysis target channel.

[0011] With this configuration, the test system according to the present invention can estimate the maximum Doppler frequency of the analysis target channel while taking into account the influence of moving objects and the like in the actual propagation path environment.

[0012] Furthermore, the test system according to the present invention may be configured such that, when the antenna device receives the downlink signal, the moving speed of the antenna device relative to the transmitting / receiving device on the network side is zero.

[0013] With this configuration, the test system according to the present invention can appropriately estimate the maximum Doppler frequency of the analysis target channel when the moving speed of the antenna device relative to the network-side transmitting / receiving device is zero or very slow.

[0014] Furthermore, the test system according to the present invention may be configured such that, when all of the one or more channels are the analysis target channels, the maximum Doppler frequency estimation unit determines the maximum value of all of the maximum Doppler frequencies of the one or more analysis target channels as the maximum Doppler frequency of the entire actual propagation path.

[0015] With this configuration, the test system according to the present invention can estimate an appropriate maximum Doppler frequency when the device under test performs communication using the MIMO (Multiple Input Multiple Output) method.

[0016] In addition, a test method according to the present invention uses IQ data of a downlink signal transmitted from a transmission / reception device (100) on the network side and output from an antenna device (10) that receives the downlink signal in an environment of a real propagation path (110), and calculates estimated characteristics H^ at a plurality of timings to be analyzed of the propagation path characteristics of a channel to be analyzed among one or more channels that constitute the real propagation path. n ij (k) and the actual propagation path estimation characteristic calculation step (S3) for calculating the estimated characteristic H^ n ij and a parameter calculation step (S4 to S10) of calculating the maximum Doppler frequency of the analysis target channel as a parameter characterizing the statistical properties of (k), wherein the parameter calculation step is performed by calculating the estimated characteristic Ĥ n ij (k) is converted from the time domain characteristic showing the time change for each subcarrier to the frequency domain characteristic G k ij (f) and a domain transformation step (S4) for transforming the frequency domain characteristic G k ijThe method includes a quasi-Doppler spectrum calculation step (S5 to S9) of calculating the quasi-Doppler spectrum of the analysis target channel by adding up the power spectrum for each subcarrier of (f) for K of the subcarriers, and a maximum Doppler frequency estimation step (S10) of estimating, as the maximum Doppler frequency, the maximum frequency that is equal to or greater than a specified power among the frequency components of the quasi-Doppler spectrum of the analysis target channel.

[0017] In addition, a test method according to the present invention uses IQ data of a downlink signal transmitted from a transmission / reception device (100) on the network side and output from an antenna device (10) that receives the downlink signal in an environment of a real propagation path (110), and calculates estimated characteristics H^ at a plurality of timings to be analyzed of the propagation path characteristics of a channel to be analyzed among one or more channels that constitute the real propagation path. n ij (k) is calculated in the actual propagation path estimation characteristic calculation step (S23), and the analysis target timing t n (n is an integer between 0 and N-1) n ij (k) from the analysis target timing t n The impulse response g of the analyzed channel in n ij (m) is calculated, and the estimated characteristic H^ is calculated. n ij As a parameter characterizing the statistical properties of (k), the impulse response g n ij and a parameter calculation step (S25 to S30) of calculating the maximum Doppler frequency of the analysis target channel from (m), wherein the parameter calculation step is performed by using delay tap τ m (m is an integer between 0 and M-1) n ij (m) is converted from the time domain characteristic showing the time change for each delay tap into the frequency domain characteristic F m ij (f), and a domain transformation step (S25) for transforming the frequency domain characteristic Fm ij The method includes a Doppler spectrum calculation step (S26 to S29) of calculating the Doppler spectrum of the channel to be analyzed by adding up the power spectrum for each delay tap of (f) for M delay taps, and a maximum Doppler frequency estimation step (S30) of estimating the maximum frequency that is equal to or greater than a specified power among the frequency components of the Doppler spectrum of the channel to be analyzed as the maximum Doppler frequency. [Effects of the Invention]

[0018] The present invention provides a test system and a method for calculating the maximum Doppler frequency that can estimate the maximum Doppler frequency in a manner that takes into account the influence of moving objects and the like in an actual propagation path environment. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a diagram schematically illustrating an environment of an actual propagation path between a base station and an antenna device. [Figure 2] 1 is a block diagram showing a configuration of a test system according to a first embodiment of the present invention. [Figure 3] 10A and 10B are diagrams for explaining the frequency domain of the estimated characteristic and the time domain characteristic showing the change over time. [Figure 4] 1 is a graph showing an example of a quasi-Doppler spectrum or a Doppler spectrum and its maximum Doppler frequency. [Figure 5] 4 is a flowchart illustrating the processing of a maximum Doppler frequency calculation method using a test system according to the first embodiment of the present invention. [Figure 6] FIG. 10 is a block diagram showing the configuration of a test system according to a second embodiment of the present invention. [Figure 7] 10A and 10B are diagrams illustrating characteristics of an impulse response in the delay axis direction and in the time axis direction showing its change over time. [Figure 8]10 is a flowchart illustrating the processing of a maximum Doppler frequency calculation method using a test system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a test system and a maximum Doppler frequency calculation method according to the present invention will be described with reference to the accompanying drawings.

[0021] (First embodiment) Fig. 1 is a diagram schematically illustrating the environment of an actual propagation path 110 between a base station 100, which is an example of a network-side transmitting / receiving device, and an antenna device 10. In Fig. 1, data communication between the base station 100 and the antenna device 10 is performed using multiple subcarriers using an OFDM (Orthogonal Frequency Division Multiplexing) modulation method. The present invention assumes a situation in which, when the antenna device 10 receives a downlink signal from the base station 100, the moving speed of the antenna device 10 relative to the base station 100 is zero or a very slow speed.

[0022] The antenna device 10 receives downlink signals transmitted from T antennas Tx1 to TxT of the base station 100 in an environment of an actual propagation path 110 consisting of one or more channels. For example, the antenna device 10 is an air monitor or a mobile phone terminal. The antenna device 10 has R antennas Rx1 to RxR that receive the downlink signals transmitted from the antennas Tx1 to TxT of the base station 100 as received signals, and an IQ data output unit 11.

[0023] Here, the number T of antennas Tx1 to TxT of the base station 100 and the number R of antennas Rx1 to RxR of the antenna device 10 are each an integer of 1 or more, and the value of T×R is the number of channels of the actual propagation path 110.

[0024] The IQ data output unit 11 performs reception processing such as amplification, frequency conversion, and analog-to-digital conversion on the R reception signals received by the antennas Rx1 to RxR. Furthermore, the IQ data output unit 11 demodulates the R reception signals that have been subjected to reception processing to generate R sets of I-component baseband signals and Q-component baseband signals that are orthogonal to each other. In this specification, the I-component baseband signals and Q-component baseband signals are collectively referred to simply as "IQ data."

[0025] H in Figure 1 n 11 (k),H n 21 (k),···,H n R1 (k),H n 12 (k),H n 22 (k),···,H n R2 (k),···,H n 1T (k),H n 2T (k),···,H n RT (k) is an element of a channel matrix H(k,n) shown in equation (1) described later.

[0026] As shown in FIG. 2, the test system 1 of this embodiment includes a test device 15, a signal processing unit 20, a pseudo-path characteristics generating unit 30, and a display unit 41.

[0027] The test equipment 15 has the function of a pseudo base station device that generates downlink signals required for testing a device under test (DUT) 120, transmits the signals to the DUT 120 via a pseudo propagation path, receives uplink signals transmitted from the DUT 120, and performs processing required for the test. The test equipment 15 is configured to test, for example, the demodulation performance of the DUT 120. The pseudo propagation path between the test equipment 15 and the DUT 120 is formed by a pseudo propagation path characteristics generator 30, which will be described later. The DUT 120 is, for example, a mobile phone terminal capable of communication using a MIMO (Multiple Input Multiple Output) method.

[0028] The signal processing unit 20 includes an actual propagation path estimation characteristics calculation unit 21 and a parameter calculation unit 22 .

[0029] The actual propagation path estimation characteristic calculation unit 21 uses the IQ data output from the IQ data output unit 11 of the antenna device 10 to calculate the propagation path characteristic H of the channel to be analyzed among one or more channels that make up the actual propagation path 110. n ij (k) Multiple analysis target timing t n Estimated characteristics H^ n ij (k) is calculated. Here, H n ij (k) represents each element of the channel matrix H(k,n) of the actual propagation path 110 in the following equation (1). i is the index of the R antennas Rx1 to RxR of the antenna device 10, and j is the index of the T antennas Tx1 to TxT of the base station 100.

[0030] That is, R=1 and T=1 represents the SISO (Single Input Single Output) method, R≧2 and T=1 represents the SIMO (Single Input Multiple Output) method, R=1 and T≧2 represents the MISO (Multiple Input Single Output) method, and R≧2 and T≧2 represents the MIMO method.

[0031]

number

[0032] In equation (1), k is an index in the frequency direction, for example, an index of the subcarrier number. Here, if Δf is the frequency interval of the subcarriers, then the frequency f of each subcarrier is k is k × Δf. Also, n is the number of the above multiple analysis target timings t n is an index in the time direction corresponding to, for example, an index of an OFDM symbol number, where k is an integer from 0 to K-1, and n is an integer from 0 to N-1.

[0033] Reference signals (RS) are included in the R sets of IQ data output from the IQ data output unit 11 of the antenna device 10. For example, in the 5G NR standard, reference signals such as CSI-RS (Channel State Information Reference Signal), DM-RS (Demodulation Reference Signal), TRS (Tracking Reference Signal), and PT-RS (Phase Tracking Reference Signal) are provided.

[0034] The actual propagation path estimation characteristic calculation unit 21 calculates the propagation path characteristic H from the known RS included in the downlink signals transmitted from the T antennas Tx1 to TxT of the base station 100 and the RS of each channel included in the R sets of IQ data output from the IQ data output unit 11. n ij (k) Estimated characteristic H^ n ij (k) is calculated. n ij(k) includes information on the amplitude fluctuation amount and phase fluctuation amount of the RS of the IQ data obtained from the received signal received by the i-th antenna Rxi for the known RS transmitted by the j-th antenna Txj. For example, in the 5G NR standard, the actual propagation path estimation characteristic calculation unit 21 calculates the estimated characteristic Ĥ n ij Used to calculate (k). Here, H^ n ij (k) represents each element of the matrix H^(k,n) of the estimated values ​​of the channel matrix H(k,n) of the actual channel 110 in equation (1), and is expressed as in equation (2).

[0035]

number

[0036] For example, as shown in Figure 3, n ij For (k), a certain n (a certain analysis target timing t) on the time axis t n ), the series of data obtained by shifting k in the direction of the frequency axis f by the amount of the signal bandwidth to be analyzed is H^ n ij The graph at the bottom of Figure 3 shows the frequency domain characteristics of H^(k). n ij (k) is a vector representation of the real and imaginary parts of the frequency domain characteristics.

[0037] On the other hand, a certain H^ n ij (k) on the frequency axis f (one frequency f k ), where n is the analysis target timing t n The series of data swept along the time axis t for each n ij The graph on the right side of Figure 3 shows the time domain characteristics of H^(k) along the time axis. n ij (k) shows the real and imaginary parts of the time domain characteristics that show the time change.

[0038] Here, according to the Nyquist theorem, the estimated characteristic H^ is n ij In order to capture the change of (k) in the time axis t direction, the analysis target timing t n The maximum value Tc of the interval is Tc<1 / (2×f d ) must be satisfied, where f d is the maximum Doppler frequency calculated by the parameter calculation unit 22, which will be described later.

[0039] The parameter calculation unit 22 calculates the estimated characteristic H^ calculated by the actual propagation path estimation characteristic calculation unit 21. n ij That is, the parameter calculation unit 22 calculates a parameter that characterizes the statistical properties of the actual propagation path estimation characteristic Ĥ (k). n ij Among (k), the estimated characteristic H^ during the period in which the statistical properties can be considered unchanged n ij The parameters are calculated using (k). The parameters calculated by the parameter calculation unit 22 are input to the pseudo channel characteristics generation unit 30.

[0040] The pseudo channel characteristic generating unit 30 includes a known channel model such as a TDL model (Tapped Delay Line model) or a CDL model (Clustered Delay Line model), etc. The pseudo channel characteristic generating unit 30 generates a plurality of pseudo channel characteristics according to the parameters calculated by the parameter calculating unit 22.

[0041] Furthermore, the pseudo-path characteristic generating unit 30 functions as a propagation path simulator that forms a pseudo-path having the generated pseudo-path characteristic between the test equipment 15 and the DUT 120 .

[0042] For example, the parameter calculation unit 22 calculates the "K factor," "PDP (Power Delay Profile)," "antenna correlation matrix," and "maximum Doppler frequency" as parameters of the TDL model.

[0043] The configuration of the parameter calculation unit 22 for calculating the "maximum Doppler frequency" among the parameters of the TDL model will be described below.

[0044] As shown in FIG. 2, the parameter calculation unit 22 includes a domain conversion unit 22a, a quasi-Doppler spectrum calculation unit 22b, and a maximum Doppler frequency estimation unit 22c, and calculates the estimated characteristic H^ calculated by the actual propagation path estimation characteristic calculation unit 21. n ij From (k), the maximum Doppler frequency f of the analyzed channel d The following formula is calculated:

[0045] The domain conversion unit 22a calculates the estimated characteristic Ĥ for a certain subcarrier k as shown in the following equation (3). n ij (k) is converted from the time domain characteristics showing the time change for each subcarrier k to the frequency domain characteristics G k ij It is converted to (f).

[0046]

number

[0047] The quasi-Doppler spectrum calculation unit 22b calculates the frequency domain characteristic G converted by the domain conversion unit 22a as shown in the following equation (4). k ij (f) Power spectrum S for each subcarrier k ij By adding (f) for K subcarriers, the quasi-Doppler spectrum S of the analyzed channel is obtained. ij (f) is calculated.

[0048]

number

[0049] The maximum Doppler frequency estimation unit 22c estimates the quasi-Doppler spectrum S of the analysis target channel calculated by the quasi-Doppler spectrum calculation unit 22b. ij Among the frequency components of (f), the maximum frequency that is greater than the specified power is called the maximum Doppler frequency f d Here, the specified power may be, for example, equal to or greater than the upper limit of the power of the noise component. FIG. 4 shows the quasi-Doppler spectrum S calculated by the quasi-Doppler spectrum calculation unit 22b. ij (f) and its maximum Doppler frequency f d 1 is a graph showing an example of the above.

[0050] When all of the one or more channels constituting the actual propagation path 110 are to be analyzed, the maximum Doppler frequency estimation unit 22c calculates the maximum Doppler frequency f d Furthermore, the maximum Doppler frequency estimation unit 22c estimates all the estimated maximum Doppler frequencies f d The maximum value of the Doppler frequency f dMAX The determination may be made as follows.

[0051] The display unit 41 is configured with a display device such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays a setting screen for setting the test contents of the test system 1, test results, and the maximum Doppler frequency f d The display unit 41 may have an operation function such as soft keys on the display screen.

[0052] The signal processing unit 20 is configured by a control device such as a computer including, for example, a central processing unit (CPU), a graphics processing unit (GPU), a field programmable gate array (FPGA), a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), etc. Furthermore, the signal processing unit 20 can configure at least a part of an actual channel estimation characteristics calculation unit 21, a parameter calculation unit 22, an impulse response calculation unit 23 (described later), and a parameter calculation unit 24 (described later) in software form by executing a predetermined program by the CPU or the GPU.

[0053] The above program may be stored in advance in a ROM or HDD. Alternatively, the program may be provided or distributed in an installable or executable format recorded on a computer-readable recording medium such as a compact disc or DVD. Alternatively, the program may be stored in a computer connected to a network such as the Internet and provided or distributed by downloading via the network.

[0054] An example of the maximum Doppler frequency calculation method using the test system 1 of this embodiment will be described below with reference to the flowchart in Fig. 5. Note that descriptions that overlap with the description of the configuration of the test system 1 described above will be omitted as appropriate.

[0055] First, the IQ data of the downlink signal is input from the IQ data output unit 11 of the antenna device 10 to the signal processing unit 20 (step S1).

[0056] Next, the signal processing unit 20 calculates the initial value of the subcarrier index k and the array S' ij The initial values ​​of (f) are set to 0 (step S2).

[0057] Next, the actual propagation path estimation characteristic calculation unit 21 uses the IQ data input in step S1 to calculate the propagation path characteristic H of the channel to be analyzed among one or more channels that make up the actual propagation path 110. n ij (k) Multiple analysis target timing t n Estimated characteristics H^ n ij (k) is calculated (actual propagation path estimation characteristic calculation step S3).

[0058] Next, the domain conversion unit 22a calculates the estimated characteristic Ĥ n ij (k) is converted from the time domain characteristics showing the time change for each subcarrier k to the frequency domain characteristics G k ij (f) (domain transformation step S4).

[0059] Next, the quasi-Doppler spectrum calculation unit 22b calculates the frequency domain characteristic G k ij (f) Power spectrum S k ij (f) is calculated (quasi-Doppler spectrum calculation step S5).

[0060] Next, the quasi-Doppler spectrum calculation unit 22b calculates the power spectrum S calculated in step S5. k ij (f) is the current array S' ij Add to (f) to get new S' ij (f) (quasi-Doppler spectrum calculation step S6).

[0061] Next, the signal processing unit 20 determines whether the index k has reached K-1. If the index k has not reached K-1 (quasi-Doppler spectrum calculation step S7: NO), the signal processing unit 20 executes the processes from step S8 onwards. If the index k has reached K-1 (quasi-Doppler spectrum calculation step S7: YES), the signal processing unit 20 executes the processes from step S9 onwards.

[0062] In step S8, the signal processing unit 20 adds 1 to the current index k (quasi-Doppler spectrum calculation step S8).Then, the signal processing unit 20 executes the processes from step S3 onwards again.

[0063] In step S9, the signal processing unit 20 calculates the current array S' ij (f) is the quasi-Doppler spectrum S of the analyzed channel. ij (f) (quasi-Doppler spectrum calculation step S9).

[0064] Next, the maximum Doppler frequency estimation unit 22c calculates the quasi-Doppler spectrum S calculated in the quasi-Doppler spectrum calculation step S9. ij Among the frequency components of (f), the maximum frequency that is greater than the specified power is called the maximum Doppler frequency f d (maximum Doppler frequency estimation step S10).

[0065] Next, the signal processing unit 20 calculates the maximum Doppler frequency f d It is determined whether the maximum Doppler frequency f of all the T×R analysis target channels has been estimated in the maximum Doppler frequency estimation step S10. d If the maximum Doppler frequency f is estimated in the maximum Doppler frequency estimation step S10 (step S11: YES), the signal processing unit 20 executes the processes in step S12 and onward. d If the maximum Doppler frequency f has not been estimated by the maximum Doppler frequency estimation step S10 (step S11: NO), the signal processing unit 20 does not yet estimate the maximum Doppler frequency f d The processes from step S2 onwards are executed again for the analysis target channels for which the values ​​have not been estimated.

[0066] Next, the maximum Doppler frequency estimation unit 22c calculates all the maximum Doppler frequencies f estimated in the maximum Doppler frequency estimation step S10. d The maximum value of the Doppler frequency f dMAX(step S12).

[0067] Next, the signal processing unit 20 calculates the maximum Doppler frequency f of each channel estimated in the maximum Doppler frequency estimation step S10. d and the maximum Doppler frequency f determined in step S12. d The maximum value f dMAX is displayed on the display unit 41 (step S13).

[0068] Steps S4 to S10 are performed using the estimated characteristic H^ n ij The maximum Doppler frequency f of the analyzed channel is used as a parameter to characterize the statistical properties of (k). d A parameter calculation step is configured to calculate:

[0069] As described above, the test system 1 according to this embodiment is capable of measuring the estimated characteristic Ĥ obtained in the environment of the actual propagation path 110. n ij The maximum Doppler frequency f of the analyzed channel is used as a parameter to characterize the statistical properties of (k). d As a result, the test system 1 according to this embodiment calculates the maximum Doppler frequency f of the analysis target channel, taking into account the influence of moving objects and the like in the actual propagation path environment. d can be estimated.

[0070] In particular, the test system 1 according to this embodiment detects the maximum Doppler frequency f of the analysis target channel when the antenna device 10 receives a downlink signal from the base station 100 and the moving speed of the antenna device 10 relative to the base station 100 is zero or a very low speed. d can be appropriately estimated.

[0071] Furthermore, the test system 1 according to this embodiment has the above maximum Doppler frequency f dThe pseudo channel characteristic generator 30, which functions as a channel simulator, generates pseudo channel characteristics of the channel model using the pseudo channel characteristic generator 30. Furthermore, the test system 1 according to this embodiment can test the DUT 120 by reproducing the statistical channel characteristics of the actual channel 110 using the pseudo channel characteristics generated by the pseudo channel characteristic generator 30.

[0072] Furthermore, the test system 1 according to this embodiment detects all the maximum Doppler frequencies f d The maximum value of the Doppler frequency f dMAX As a result, the test system 1 according to this embodiment can estimate an appropriate maximum Doppler frequency when the DUT 120 performs communication using the MIMO system.

[0073] (Second embodiment) Next, a test system and a maximum Doppler frequency calculation method according to a second embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted where appropriate. Also, descriptions of operations similar to those in the first embodiment will be omitted where appropriate. This embodiment also assumes a situation in which, when the antenna device 10 receives a downlink signal from the base station 100, the moving speed of the antenna device 10 relative to the base station 100 is zero or a very slow speed.

[0074] As shown in FIG. 6, the signal processing unit 20 included in the test system 2 of this embodiment includes an actual propagation path estimation characteristics calculation unit 21, an impulse response calculation unit 23, and a parameter calculation unit 24.

[0075] The impulse response calculation unit 23 calculates the analysis target timing t n Estimated characteristics H^ n ij From (k), the analysis target timing t n The impulse response of the analyzed channel in g n ij(m) is calculated. Here, as shown in the following equation (5), the estimated characteristic H^ n ij (k) is a number of delay taps τ corresponding to the number of paths. m The impulse response g consists of n ij (m), where m is the delay tap τ m where M is the number of delay taps.

[0076]

number

[0077] Equation (5) can be rewritten as equation (6) below.

[0078]

number

[0079] Furthermore, equation (6) can be transformed into the following equation (7). Here, the generalized inverse matrix of the matrix A is represented as A+. That is, the impulse response calculation unit 23 calculates the impulse response g n ij Matrix A is a kind of Fourier transform matrix that can calculate a column vector whose elements are frequency characteristics by multiplying it by a column vector whose elements are time domain impulse responses.

[0080]

number

[0081] Impulse response g n ij Multiple delay taps τ in (m) m are arranged along the delay axis τ. The impulse response g n ij (m) is the timing to be analyzed nSince it changes depending on the delay axis τ and the time axis t, it can be shown as a two-dimensional function of the delay axis τ and the time axis t as shown in Figure 7.

[0082] The graph at the bottom of Figure 7 shows the time axis t for a certain n (a certain analysis target timing t n ) along n ij (m) is a vector representation of the real and imaginary parts of the series of data.

[0083] On the other hand, some g n ij (m), a certain m (a certain delay tap τ m ), where n is the analysis target timing t n The series of data swung along the time axis t for each n ij The graph on the right side of Figure 7 shows the time domain characteristics of the g n ij This shows the real and imaginary parts of the time domain characteristics that show the time variation of (m).

[0084] The parameter calculation unit 24 calculates the estimated characteristic H^ calculated by the actual propagation path estimation characteristic calculation unit 21 in the same manner as the parameter calculation unit 22 of the first embodiment. n ij (k). That is, the parameter calculation unit 24 calculates a parameter that characterizes the statistical properties of the estimated characteristic Ĥ calculated by the actual propagation path estimation characteristic calculation unit 21. n ij Among (k), the estimated characteristic H^ during the period in which the statistical properties can be considered unchanged n ij The parameters are calculated using (k). The parameters calculated by the parameter calculation unit 24 are input to the pseudo channel characteristics generation unit 30.

[0085] For example, the parameter calculation unit 24 calculates the "K factor," "PDP," "antenna correlation matrix," and "maximum Doppler frequency" as parameters of the TDL model.

[0086] The configuration of the parameter calculation unit 24 for calculating the "maximum Doppler frequency" among the parameters of the TDL model will be described below.

[0087] As shown in FIG. 6, the parameter calculation unit 24 includes a domain conversion unit 24a, a Doppler spectrum calculation unit 24b, and a maximum Doppler frequency estimation unit 24c, and calculates the impulse response g calculated by the impulse response calculation unit 23. n ij From (m), the maximum Doppler frequency f of the analyzed channel d The following formula is calculated:

[0088] The domain conversion unit 24a converts a certain delay tap τ m Impulse response g n ij (m) is the delay tap τ m From the time domain characteristics showing the time change of each m ij (f), where m is an integer between 0 and M-1.

[0089]

number

[0090] The Doppler spectrum calculation unit 24b calculates the frequency domain characteristic F converted by the domain conversion unit 24a as shown in the following equation (9). m ij (f) delay tap τ m The power spectrum for each M delay taps τ m By adding up the Doppler spectrum Ds of the analysis target channel, ij (f) is calculated.

[0091]

number

[0092] The maximum Doppler frequency estimation unit 24c estimates the Doppler spectrum Ds of the analysis target channel calculated by the Doppler spectrum calculation unit 24b. ij Among the frequency components of (f), the maximum frequency that is greater than the specified power is called the maximum Doppler frequency f d FIG. 4 shows the Doppler spectrum Ds calculated by the Doppler spectrum calculation unit 24b. ij (f) and its maximum Doppler frequency f d 1 is a graph showing an example of the above.

[0093] Here, the quasi-Doppler spectrum S in equation (4) explained in the first embodiment ij (f) can be transformed into the following equation (10).

[0094]

number

[0095] Thus, the quasi-Doppler spectrum S in Eq. (4) ij (f) is the Doppler spectrum Ds in equation (9) ij (f) are superimposed. In other words, the Doppler spectrum Ds ij The frequency axis spread of (f) is the quasi-Doppler spectrum S ij (f) is the same as the frequency axis spread, and the Doppler spectrum Ds ij (f) and the quasi-Doppler spectrum S ij (f) from the common maximum Doppler frequency f d It can be seen that

[0096] When all of the one or more channels constituting the actual propagation path 110 are to be analyzed, the maximum Doppler frequency estimation unit 24c calculates the maximum Doppler frequency f d Furthermore, the maximum Doppler frequency estimation unit 24c estimates all the estimated maximum Doppler frequencies f dThe maximum value of the Doppler frequency f dMAX The determination may be made as follows.

[0097] An example of the maximum Doppler frequency calculation method using the test system 2 of this embodiment will be described below with reference to the flowchart in Fig. 8. Note that descriptions that overlap with the description of the configuration of the test system 2 described above will be omitted as appropriate.

[0098] First, the IQ data of the downlink signal is input from the IQ data output unit 11 of the antenna device 10 to the signal processing unit 20 (step S21).

[0099] Next, the signal processing unit 20 calculates the delay tap τ m The initial value of the index m of the ij The initial values ​​of (f) are set to 0 (step S22).

[0100] Next, the actual propagation path estimation characteristic calculation unit 21 uses the IQ data input in step S21 to calculate the propagation path characteristic H of the channel to be analyzed among one or more channels that make up the actual propagation path 110. n ij (k) Multiple analysis target timing t n Estimated characteristics H^ n ij (k) is calculated (actual propagation path estimation characteristic calculation step S23).

[0101] Next, the impulse response calculation unit 23 calculates the analysis target timing t n Estimated characteristics H^ n ij From (k), the analysis target timing t n Impulse response g n ij (m) is calculated (impulse response calculation step S24).

[0102] Next, the domain conversion unit 24a converts the delay tap τ m Impulse response g n ij(m) is the delay tap τ m From the time domain characteristics showing the time change of each m ij (f) (domain transformation step S25).

[0103] Next, the Doppler spectrum calculation unit 24b calculates the frequency domain characteristic F m ij (f) Power spectrum of the current array Ds' ij Add to (f) to get new Ds' ij (f) (Doppler spectrum calculation step S26).

[0104] Next, the signal processing unit 20 determines whether the index m has reached M-1. If the index m has not reached M-1 (Doppler spectrum calculation step S27: NO), the signal processing unit 20 executes the processes of step S28 and subsequent steps. If the index m has reached M-1 (Doppler spectrum calculation step S27: YES), the signal processing unit 20 executes the processes of step S29 and subsequent steps.

[0105] In step S28, the signal processing unit 20 adds 1 to the current index m (Doppler spectrum calculation step S28).Then, the signal processing unit 20 executes the processes from step S23 onwards again.

[0106] In step S29, the signal processing unit 20 calculates the current array Ds' ij (f) is the Doppler spectrum Ds of the channel being analyzed. ij (f) (Doppler spectrum calculation step S29).

[0107] Next, the maximum Doppler frequency estimation unit 24c calculates the Doppler spectrum Ds calculated in the Doppler spectrum calculation step S29. ij Among the frequency components of (f), the maximum frequency that is greater than the specified power is called the maximum Doppler frequency f d(maximum Doppler frequency estimation step S30).

[0108] Next, the signal processing unit 20 calculates the maximum Doppler frequency f d It is determined whether the maximum Doppler frequency f of all the T×R analysis target channels has been estimated in the maximum Doppler frequency estimation step S30. d If the maximum Doppler frequency f is estimated in the maximum Doppler frequency estimation step S30 (step S31: YES), the signal processing unit 20 executes the processes in and after step S32. d If the maximum Doppler frequency f has not been estimated by the maximum Doppler frequency estimation step S30 (step S31: NO), the signal processing unit 20 does not yet estimate the maximum Doppler frequency f d The process from step S22 onwards is executed again for the analysis target channel for which the value of the parameter has not been estimated.

[0109] Next, the maximum Doppler frequency estimation unit 24c calculates all the maximum Doppler frequencies f estimated in the maximum Doppler frequency estimation step S30. d The maximum value of the Doppler frequency f dMAX (step S32).

[0110] Next, the signal processing unit 20 calculates the maximum Doppler frequency f of each channel estimated in the maximum Doppler frequency estimation step S30. d and the maximum Doppler frequency f determined in step S32. d The maximum value f dMAX is displayed on the display unit 41 (step S33).

[0111] Steps S25 to S30 are performed using the estimated characteristic H^ n ij The impulse response g is a parameter that characterizes the statistical properties of (k). n ij From (m), the maximum Doppler frequency f of the analyzed channel d A parameter calculation step is configured to calculate:

[0112] The following describes the "estimated characteristic H^" of the first embodiment. n ij From the time domain characteristics showing the time variation of (k), the maximum Doppler frequency f d (hereinafter referred to as "Method 1")" and the "Method of estimating impulse response g n ij From the time domain characteristics showing the time variation of (m), the maximum Doppler frequency f d The following summarizes the features of the method for estimating the

[0113] Method 1 is to estimate the characteristic H^ calculated from the actual propagation path environment. n ij (k) is used as it is, so impulse response g n ij The maximum Doppler frequency f d For example, the impulse response g n ij The error in calculating (m) is thought to be due to the fact that it is calculated from only the estimated characteristics of the part of the propagation path characteristics to which the signal to be analyzed on the frequency axis is assigned.

[0114] However, in Method 1, the delay tap τ m Characteristics of each F m ij Since (f) is added in amplitude dimension, it may be affected by interference between delay taps.

[0115] On the other hand, in Method 2, as shown in Equation (9), the delay tap τ m The power spectrum of each signal is added in the power dimension, so the maximum Doppler frequency f is calculated independently of the degree of interference due to the phase difference between delay taps. d can be estimated.

[0116] However, Method 2 uses delay taps τ in the delay axis τ. mThe impulse response g n ij When calculating the time change of (m), it may be difficult to distinguish between the same delay taps.

[0117] As described above, the test system 2 according to this embodiment is capable of measuring the estimated characteristic Ĥ obtained in the environment of the actual propagation path 110. n ij The maximum Doppler frequency f of the analyzed channel is used as a parameter to characterize the statistical properties of (k). d As a result, the test system 2 according to this embodiment calculates the maximum Doppler frequency f of the analysis target channel, taking into account the influence of moving objects and the like in the actual propagation path environment. d can be estimated.

[0118] In particular, the test system 2 according to this embodiment detects the maximum Doppler frequency f of the analysis target channel when the moving speed of the antenna device 10 relative to the base station 100 is zero or a very low speed when the antenna device 10 receives a downlink signal from the base station 100. d can be appropriately estimated.

[0119] Furthermore, the test system 2 according to this embodiment has the above maximum Doppler frequency f d The pseudo-channel characteristic generator 30, which functions as a channel simulator, generates pseudo-channel characteristics of the channel model using the pseudo-channel characteristic generator 30. Furthermore, the test system 2 according to this embodiment can test the DUT 120 by reproducing the statistical channel characteristics of the actual channel 110 using the pseudo-channel characteristics generated by the pseudo-channel characteristic generator 30.

[0120] Furthermore, the test system 2 according to this embodiment detects all the maximum Doppler frequencies f d The maximum value of the Doppler frequency f dMAXAs a result, the test system 1 according to this embodiment can estimate an appropriate maximum Doppler frequency when the DUT 120 performs communication using the MIMO system.

[0121] In the present embodiment described above, the base station 100 is the network-side transceiver that transmits the downlink signal toward the actual propagation path 110. However, instead of a base station, the network-side transceiver may be, for example, a Wi-Fi (registered trademark) access point. [Explanation of symbols]

[0122] 1,2 Test system 10 Antenna device 11 IQ data output section 15 Test equipment 20 Signal Processing Section 21 Actual propagation path estimation characteristic calculation unit 22,24 Parameter calculation section 22a, 24a Domain conversion section 22b Quasi-Doppler spectrum calculation section 22c, 24c Maximum Doppler frequency estimation section 23 Impulse response calculation section 24b Doppler spectrum calculation section 30 Pseudo propagation path characteristic generator 41 Display section 100 Base station (network side transmitting / receiving device) 110 Actual propagation path 120 DUT Rx1~RxR antenna Tx1~TxT antenna

Claims

1. Using IQ data of the downlink signal output from an antenna device (10) that receives a downlink signal transmitted from a network-side transmitting / receiving device (100) in an environment of a real propagation path (110), an estimated characteristic H^ of the propagation path characteristic of an analysis target channel among one or more channels that constitute the real propagation path at a plurality of analysis target timings is calculated. ｎ ｉｊ an actual propagation path estimation characteristic calculation unit (21) that calculates (k); The estimated characteristic H^ ｎ ｉｊ a parameter calculation unit (22) that calculates the maximum Doppler frequency of the analysis target channel as a parameter that characterizes the statistical properties of (k), The parameter calculation unit The estimated characteristic H^ in subcarrier k (k is an integer from 0 to K-1) ｎ ｉｊ (k) is obtained by converting the time domain characteristic G ｋ ｉｊ a domain conversion unit (22a) for converting the image into The frequency domain characteristic G ｋ ｉｊ a quasi-Doppler spectrum calculation unit (22b) that calculates a quasi-Doppler spectrum of the analysis target channel by adding up the power spectrum for each subcarrier of (f) for K subcarriers; a maximum Doppler frequency estimation unit (22c) that estimates, as the maximum Doppler frequency, the maximum frequency that is equal to or greater than a specified power among the frequency components of the quasi-Doppler spectrum of the channel to be analyzed.

2. Using IQ data of the downlink signal output from an antenna device (10) that receives a downlink signal transmitted from a network-side transmitting / receiving device (100) in an environment of a real propagation path (110), an estimated characteristic H^ of the propagation path characteristic of an analysis target channel among one or more channels that constitute the real propagation path at a plurality of analysis target timings is calculated. ｎ ｉｊ an actual propagation path estimation characteristic calculation unit (21) that calculates (k); Analysis target timing t ｎ (n is an integer from 0 to N-1) ｎ ｉｊ (k) from the analysis target timing t ｎ The impulse response g of the channel to be analyzed ｎ ｉｊ an impulse response calculation unit (23) that calculates (m); The estimated characteristic H^ ｎ ｉｊ As a parameter characterizing the statistical properties of (k), the impulse response g ｎ ｉｊ a parameter calculation unit (24) that calculates the maximum Doppler frequency of the analysis target channel from (m), The parameter calculation unit Delay Tap τ ｍ (m is an integer from 0 to M-1) ｎ ｉｊ (m) is obtained by converting the time domain characteristic F ｍ ｉｊ a domain conversion unit (24a) for converting the image into (f); The frequency domain characteristic F ｍ ｉｊ a Doppler spectrum calculation unit (24b) that calculates a Doppler spectrum of the analysis target channel by adding the power spectrum for each delay tap of (f) for M delay taps; a maximum Doppler frequency estimation unit (24c) that estimates, as the maximum Doppler frequency, the maximum frequency that is equal to or greater than a specified power among the frequency components of the Doppler spectrum of the channel to be analyzed.

3. 3. The test system according to claim 1, wherein when the antenna device receives the downlink signal, the moving speed of the antenna device relative to the network-side transmitting / receiving device is zero.

4. When all of the one or more channels are the analysis target channels, 3. The test system according to claim 1, wherein the maximum Doppler frequency estimation unit determines the maximum value of all the maximum Doppler frequencies of the one or more analysis target channels as the maximum Doppler frequency of the entire actual propagation path.

5. Using IQ data of the downlink signal output from an antenna device (10) that receives a downlink signal transmitted from a network-side transmitting / receiving device (100) in an environment of a real propagation path (110), an estimated characteristic H^ of the propagation path characteristic of an analysis target channel among one or more channels that constitute the real propagation path at a plurality of analysis target timings is calculated. ｎ ｉｊ an actual propagation path estimation characteristic calculation step (S3) for calculating (k); The estimated characteristic H^ ｎ ｉｊ a parameter calculation step (S4 to S10) of calculating a maximum Doppler frequency of the analysis target channel as a parameter characterizing the statistical properties of (k); The parameter calculation step The estimated characteristic H^ in subcarrier k (k is an integer from 0 to K-1) ｎ ｉｊ (k) is obtained by converting the time domain characteristic G ｋ ｉｊ a domain transformation step (S4) for transforming the image into (f); The frequency domain characteristic G ｋ ｉｊ a quasi-Doppler spectrum calculation step (S5 to S9) of calculating a quasi-Doppler spectrum of the analysis target channel by adding up the power spectrum for each subcarrier of (f) for K subcarriers; and a maximum Doppler frequency estimation step (S10) of estimating, as the maximum Doppler frequency, the maximum frequency that is equal to or greater than a specified power among the frequency components of the quasi-Doppler spectrum of the channel to be analyzed.

6. Using IQ data of the downlink signal output from an antenna device (10) that receives a downlink signal transmitted from a network-side transmitting / receiving device (100) in an environment of a real propagation path (110), an estimated characteristic H^ of the propagation path characteristic of an analysis target channel among one or more channels that constitute the real propagation path at a plurality of analysis target timings is calculated. ｎ ｉｊ an actual propagation path estimation characteristic calculation step (S23) for calculating (k); Analysis target timing t ｎ (n is an integer from 0 to N-1) ｎ ｉｊ (k) from the analysis target timing t ｎ The impulse response g of the channel to be analyzed ｎ ｉｊ an impulse response calculation step (S24) for calculating (m); The estimated characteristic H^ ｎ ｉｊ As a parameter characterizing the statistical properties of (k), the impulse response g ｎ ｉｊ and a parameter calculation step (S25 to S30) of calculating the maximum Doppler frequency of the analysis target channel from (m), The parameter calculation step Delay Tap τ ｍ (m is an integer from 0 to M-1) ｎ ｉｊ (m) is obtained by converting the time domain characteristic F ｍ ｉｊ a domain conversion step (S25) for converting the image into (f); The frequency domain characteristic F ｍ ｉｊ a Doppler spectrum calculation step (S26 to S29) of calculating a Doppler spectrum of the analysis target channel by adding up the power spectrum for each delay tap of (f) for M delay taps; and a maximum Doppler frequency estimation step (S30) of estimating, as the maximum Doppler frequency, the maximum frequency that is equal to or greater than a specified power among the frequency components of the Doppler spectrum of the channel to be analyzed.

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