JP2019129501A - Radio communication device and program - Google Patents

Abstract

To achieve to estimate the head timing of reception signals more accurately.SOLUTION: A radio communication device includes: a communication part having a plurality of antennas for receiving radio signals from the other radio terminal; and a control part having the steps of performing signal processing to estimate impulse response of a propagation path on each of the radio signals received by the plurality of antennas, calculating the ratio of direct wave electric power to the delayed wave electric power based on the signal processing results, and selecting the antenna with the maximum ratio as the antenna used to estimate the head timing of the radio signal.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wireless communication apparatus and program.

  In recent years, a technique has been developed for estimating the position of a terminal as a signal transmission source based on a received signal received by each of a plurality of antennas. As a specific estimation method, there is a method in which the position estimation terminal estimates the position of the packet transmission source terminal based on the leading timing of the received signal. There is also a method in which a position estimation terminal estimates the position of a terminal as a signal transmission source based on received signal power or received signal strength indicator (RSSI). There is also a method in which the position estimation terminal estimates the position of the source terminal of the packet based on the reception time of the packet (or the round trip time of the packet) between the communication terminals whose packets are synchronized.

  In relation to the above-described method, for example, in Patent Document 1 below, the distance measuring device estimates a delay profile based on the leading timing of the received signal received by each of the plurality of receiving antennas, and a direct wave is generated based on the delay profile. The power of is calculated. And the method by which a distance measuring device estimates the transmission distance between transmission / reception of a signal based on the said electric power is disclosed.

  For reference, in Patent Document 2 below, a receiving apparatus including a plurality of receiving antennas estimates the delay profile of each antenna. The receiver switches antennas so that the maximum delay time in the estimated delay profile does not exceed the guard interval time length of the MB-OFDM signal (Multi Band Orthogonal Frequency Division Multiplexing). Thus, a method for improving the decoding characteristics of a received packet by switching the antenna of the receiving apparatus is disclosed.

  Further, in Patent Document 3 below, a plurality of receiving antennas installed at half-wavelength intervals are prepared, and the arrival direction of radio waves is estimated, and simultaneously, the DUR (Desired to Undesired power Ratio) with delay waves and the delay time are simultaneously achieved. An estimation method is disclosed.

JP 2010-066235 A JP, 2009-302610, A Special Table 2007-281991

  However, the technique of Patent Document 1 can reduce the error between the estimated power of the leading timing of the received signal and the power assumed in the case of free space propagation by using a plurality of antennas. An improvement in the estimation accuracy of is not expected. Therefore, there is a possibility that the position of the wireless terminal estimated based on the head timing does not satisfy the expected accuracy.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved wireless communication apparatus capable of estimating the leading timing of a received signal with higher accuracy. And providing a program.

  To solve the above problems, according to one aspect of the present invention, a communication unit having a plurality of antennas for receiving a wireless signal from another wireless terminal, and each of the wireless signals received by the plurality of antennas The signal processing for estimating the impulse response of the propagation path is performed, the ratio of the direct wave power to the delay wave power is calculated based on the result of the signal processing, and the antenna having the maximum ratio is set to the head of the radio signal. And a control unit that selects the antenna used for timing estimation.

  The control unit may calculate the power of the head portion of the impulse response as the power of the direct wave and calculate the power sum of the impulse response other than the head portion as the power of the delayed wave.

  The control unit may perform cross correlation processing on the wireless signal using a known signal, and estimate the impulse response based on a result of the cross correlation processing.

  The control unit may perform the cross-correlation process on the preamble part of the radio signal using the known signal.

  The preamble unit may be known between the wireless communication device and the other wireless terminal.

  The control unit may estimate the start timing of the wireless signal using the preamble portion of the wireless signal received by the antenna at which the ratio is maximum.

  The control unit may set a weight according to the passage of time, and apply the weight to the power of the direct wave and the power of the delay wave.

  In order to solve the above problems, according to another aspect of the present invention, a computer is provided with a communication unit having a plurality of antennas for receiving a wireless signal from another wireless terminal, and the plurality of antennas received An antenna that performs signal processing for estimating an impulse response of a propagation path for each of the wireless signals, calculates a ratio of direct wave power to delayed wave power based on the result of the signal processing, and maximizes the ratio Is provided as a control unit that selects an antenna to be used for estimation of the leading timing of the radio signal.

  As described above, according to the present invention, it is possible to estimate the leading timing of the received signal with higher accuracy.

It is an explanatory view showing an outline of a radio communications system concerning this embodiment. It is an explanatory view showing an example of composition of a packet concerning the embodiment. It is a block diagram which shows the structural example of the radio | wireless communication apparatus concerning the embodiment. It is an explanatory view showing an example of an impulse response concerning the embodiment. It is a flowchart which shows the operation example of the radio | wireless communication apparatus concerning the embodiment. It is the block diagram which showed the example of hardware constitutions of the radio | wireless communication apparatus which concerns on the embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

  Further, in the present specification and the drawings, a plurality of components having substantially the same functional configuration or logical meaning may be distinguished by appending different alphabets after the same symbol. However, when it is not necessary to distinguish each of a plurality of components having substantially the same functional configuration or logical meaning, each of the plurality of components is only given the same reference numeral.

<< 1. Overview of this embodiment >>
<1-1. Overview of Wireless Communication System>
The present embodiment relates to a wireless communication system in which, in a wireless station equipped with a plurality of antennas, an antenna capable of estimating the head timing of a received signal with higher accuracy. Hereinafter, an overview of a wireless communication system according to an embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is an explanatory view showing an overview of a wireless communication system according to an embodiment of the present invention. As shown in FIG. 1, the wireless communication system of the present embodiment is a wireless LAN system (for example, a wireless LAN system compliant with IEEE 802.11), and includes a plurality of wireless stations 10 and wireless terminals 20.

  In the wireless communication system illustrated in FIG. 1, the wireless station 10 transmits and receives packets to and from the wireless terminal 20. The wireless communication system relates to a system in which the position of the wireless terminal 20 is estimated based on a received signal received by the wireless station 10 from the wireless terminal 20. In the embodiment of the present invention, in particular, the radio station 10 selects an antenna that has received a signal that can estimate information used for position estimation of the radio terminal 20 with high accuracy from a plurality of antennas included in the radio station 10 About.

  The radio station 10A, the radio station 10B, the radio station 10C, and the radio station 10D illustrated in FIG. 1 are fixed stations. The wireless terminal 20 is a mobile terminal. Each of the wireless stations 10A to 10D receives a packet broadcasted from the wireless terminal 20 when the wireless terminal 20 passes around the wireless stations 10A to 10D. When the wireless station 10 is within the packet transmission range 30 indicating the range to which the packet transmitted from the wireless terminal 20 reaches, the wireless station 10 can receive the packet.

  When the radio station 10 receives a packet from the radio terminal 20, the radio station 10 estimates the leading timing of the received signal. More specifically, first, the radio station 10 performs signal processing on each of the radio signals received by the plurality of antennas, and estimates an impulse response. In the present embodiment, the radio station 10 estimates an impulse response for each propagation path, and the estimation result is also referred to as a channel impulse response (CIR: Channel Impulse Response). Next, the radio station 10 calculates a ratio DUR (Desired to Undesired power Ratio) of the power of the direct wave to the power of the delayed wave based on the result of the signal processing. Finally, the radio station 10 selects the antenna having the maximum ratio DUR as the antenna used for estimating the start timing of the radio signal.

  Here, the direct wave is a radio wave directly propagating from the antenna of the radio signal transmission source to the reception source antenna. The direct wave is also hereinafter referred to as the head of the CIR. Also, the delayed wave is a radio wave that is reflected from the antenna of the transmission source of the wireless signal to the ground, a wall, etc. and then propagated to the antenna of the reception source. In the following, the delayed wave is also referred to as other than the head portion of the CIR.

  Then, the radio station 10 estimates the head timing of the radio signal received by the selected antenna, and the position of the radio terminal 20 is estimated based on the time information of the head timing. In addition, as a method of estimating the position of the wireless terminal 20, for example, it is possible to estimate the position based on the time difference of arrival (TDOA) method in which the transmission time is unnecessary and the position can be estimated based on only the reception time. And the TOA (Time of Arrival) method.

  The overview of the wireless communication system according to the embodiment of the present invention has been described above with reference to FIG. Subsequently, a configuration example of a packet according to the embodiment of the present invention will be described.

<1-2. Example of packet configuration>
Hereinafter, a configuration example of a packet according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is an explanatory diagram showing a configuration example of a packet according to the embodiment of the present invention.

  As shown in FIG. 2, the packet transmitted / received to / from the wireless terminal 20 by the wireless station 10 is composed of a preamble unit 50, a signal unit 52, and a payload unit 54.

  The preamble part 50 is a symbol sequence used to detect the symbol timing of a packet. The time length of the preamble part 50 is 16 μs. The preamble unit 50 is known between the radio station 10 and the radio terminal 20. Therefore, the radio station 10 can perform the cross-correlation process on the preamble unit 50 of the received radio signal using the known signal.

  The signal unit 52 is a symbol including control information including the modulation method, transmission rate, packet length, and the like of the payload unit 54. Moreover, the time length of the signal part 52 is 4 microseconds.

  The payload portion 54 is a symbol series including application data, and is composed of a plurality of symbols. Also, the time length per one of the plurality of symbols constituting the payload portion 54 is 4 μs, and the entire time length of the payload portion 54 is the total of the time lengths of the plurality of symbols. The time length of the payload part is a signal waveform longer than that of the preamble part.

  The configuration example of the packet according to the embodiment of the present invention has been described above with reference to FIG. Then, the structural example of the radio | wireless communications system which concerns on embodiment of this invention is demonstrated.

<1-3. Configuration example of wireless communication system>
Below, the structural example of the radio | wireless communications system which concerns on this embodiment is demonstrated. As described above, the wireless communication system of the present embodiment is configured of the wireless station 10 and the wireless terminal 20.

(1) Radio station 10
The radio station 10 is a radio communication device that communicates with the radio terminal 20. For example, the wireless station 10 is connected to and communicates with the wireless terminal 20 by an arbitrary communication method. More specifically, the wireless station 10 communicates with the wireless terminal 20 by being connected to an external network.

  The communication scheme of the wireless station 10 is not particularly limited. For example, the wireless station 10 is connected to the wireless terminal 20 by wireless communication.

  Further, the radio station 10 calculates the leading timing of the packet based on information when the packet is transmitted / received to / from the radio terminal 20. For example, the wireless station 10 receives a packet from the wireless terminal 20 and estimates the leading timing of the packet using the preamble part 50 of the packet.

(2) Wireless terminal 20
The wireless terminal 20 is a wireless terminal that communicates with the wireless station 10. For example, the wireless terminal 20 transmits and receives packets to and from the wireless station 10. Also, the wireless terminal 20 in the present embodiment is a target of position estimation. For example, the wireless terminal 20 transmits and receives a packet to and from the wireless station 10 in order to obtain information used for position estimation.

  The wireless terminal 20 also has a function of generating data in the payload portion 54 of the packet based on the packet received from the wireless station 10. For example, the wireless terminal 20 payloads a symbol sequence known between the wireless terminal 20 and the wireless station 10 based on application data and information bit sequence known in advance with the wireless station 10 that transmits and receives packets. Generated in part 54. Hereinafter, the known symbol sequence in the payload portion 54 is also referred to as a payload portion preamble.

  The configuration example of the wireless communication system according to the present embodiment has been described above. Subsequently, a configuration example of a wireless communication apparatus according to an embodiment of the present invention will be described.

<< 2. Configuration example of wireless communication device >>
Hereinafter, with reference to FIGS. 3 and 4, an exemplary configuration of a wireless communication apparatus according to an embodiment of the present invention will be described. FIG. 3 is a block diagram showing a configuration example of the wireless station 10 which is a wireless communication apparatus according to the embodiment of the present invention. As shown in FIG. 3, the wireless station 10 according to the present embodiment includes a communication unit 100 and a control unit 130.

(1) Communication unit 100
The communication unit 100 includes a plurality of communication units, and has a function of receiving a radio signal in each communication unit. For example, the communication unit 100 transmits / receives a packet to / from the wireless terminal 20 with an antenna provided in each of the plurality of communication units. More specifically, as shown in FIG. 3, the communication unit 100 according to the present embodiment includes a first communication unit 110 and a second communication unit 120. The first communication unit 110 includes an antenna 112, a demodulator 114, and an ADC (Analog to Digital Converter) 116. The second communication unit 120 is configured of an antenna 122, a demodulator 124, and an ADC 126. Note that, in the present embodiment, the communication unit 100 includes at least two sets of communication units each including the above-described antenna, demodulator, and ADC.

(First communication unit 110)
・ Antenna 112
The antenna 112 has a single or a plurality of antenna elements, and has a function of transmitting and receiving a radio signal to and from an antenna of another communication device. For example, the antenna 112 receives a radio signal transmitted from the antenna of the radio terminal 20. Then, the antenna 112 outputs the received radio signal to the demodulator 114 as a received signal.

・ Demodulator 114
The demodulator 114 has a function of demodulating the received signal. For example, the demodulator 114 converts the received signal input from the antenna 112 into an analog baseband received signal. The demodulator 114 then outputs the analog baseband reception signal to the ADC 116.

・ ADC 116
The ADC 116 is an analog-digital conversion circuit (A / D conversion circuit) and has a function of converting an analog signal into a digital signal. For example, the ADC 116 converts an analog baseband reception signal received from the demodulator 114 into a digital baseband reception signal, and the ADC 116 outputs the digital baseband reception signal to the control unit 130.

(Second communication unit 120)
・ Antenna 122
The antenna 122 has the same function as the above-described antenna 112, and the description thereof is omitted to avoid the redundant description. However, the difference is that a radio signal received by the antenna 122 is output to the demodulator 124 as a received signal.

・ Demodulator 124
The demodulator 124 has the same function as the demodulator 114 described above, and the description thereof is omitted to avoid redundant description. However, the difference is that the demodulator 124 outputs an analog baseband received signal to the ADC 126.

・ ADC 126
The ADC 126 has the same function as the above-described ADC 116, and the description thereof will be omitted to avoid redundant description.

(2) Control unit 130
The control unit 130 has a function of controlling processing related to the radio signal received by the communication unit 100. For example, the control unit 130 has a function of estimating the start timing of the received signal received from the wireless terminal 20.

  In order to realize the above-described function, the control unit 130 according to the present embodiment includes an FPGA (Field Programmable Gate Array) 132 and a storage unit 134 as shown in FIG. 3.

(FPGA132)
The FPGA 132 has a function of performing digital signal processing, and estimates the start timing of the received signal described above. Here, the FPGA is an integrated circuit whose configuration can be rewritten by the user after manufacture. For example, the FPGA 132 performs digital signal processing on the received signal and estimates an impulse response. Then, the FPGA 132 estimates the leading timing of the received signal based on the impulse response. Note that the FPGA 132 of the present embodiment performs cross-correlation processing as digital signal processing, but the digital signal processing related to head timing estimation is not limited to cross-correlation processing, and may be arbitrary processing.

  First, in calculating the head timing of the packet, the FPGA 132 performs signal processing for estimating the impulse response of the propagation path on each of the wireless signals (received signals) received by the plurality of antennas of the communication unit 100. More specifically, the FPGA 132 performs cross-correlation processing on each of the reception signal received by the first communication unit 110 and the reception signal received by the second communication unit 120 using a known signal. At this time, the FPGA 132 performs a cross-correlation process using a known signal with respect to the preamble part 50 of each received signal. Then, the FPGA 132 estimates the channel impulse response of the reception signal of the first communication unit 110 as CIR1 and estimates the channel impulse response of the reception signal of the second communication unit 120 as CIR2 based on the result of the cross correlation process. .

  Here, an example of a channel impulse response will be described with reference to FIG. FIG. 4 is an explanatory diagram illustrating an example of a channel impulse response according to the embodiment of the present invention. The graph shown in FIG. 4 shows the channel impulse response CIR based on the cross-correlation value calculated by the FPGA 132 through the cross-correlation process. The vertical axis indicates the cross correlation value, and the horizontal axis indicates time.

  FIG. 4 shows the channel impulse response CIR1 of the received signal received by the antenna 112 of the first communication unit 110 and the channel impulse response CIR2 of the received signal received by the antenna 122 of the second communication unit 120. ing. Since the installation positions of the antenna 112 and the antenna 122 are different, the radio propagation paths are different, and CIR1 and CIR2 estimated by the FPGA 132 have different shapes. For example, as shown in FIG. 4, the cross-correlation value of CIR1 has a high amplitude level of the cross-correlation value 70 at the head part, and the amplitude level of the cross-correlation value 72 other than the head part and the amplitude of the cross-correlation value 70 at the head part. The difference with the level is large. Further, the cross-correlation value of CIR2 has a high amplitude level of the cross-correlation value 80 at the head part, and the difference between the amplitude level of the cross-correlation value 82 other than the head part and the amplitude level of the cross-correlation value 80 of the head part is CIR1 It is small compared to the case of, and gradually decreases with time.

  As described above, the difference between the amplitude level of the cross-correlation value 80 at the top of the CIR 2 and the amplitude level of the cross-correlation value 82 other than the top is small. Therefore, for the reason described later, the leading timing estimated based on CIR2 is likely to have an estimation error as compared with the leading timing estimated based on CIR1.

  Therefore, in the present embodiment, the FPGA 132 calculates the ratio DUR of the power of the direct wave to the power of the delayed wave based on the result of the signal processing, and selects the head timing with higher estimation accuracy based on the ratio DUR of the power. . For example, the FPGA 132 calculates the power of the leading part (direct wave) of the CIR as the power of the direct wave, and calculates the power sum of the powers other than the leading part of the CIR (delayed wave) as the power of the delayed wave. More specifically, in CIR1 shown in FIG. 4, assuming that the time length of CIR1 is T_N, the time length of the head of CIR1 is T_H, the power of the direct wave is α1, and the power sum of the delay waves is β1, The ratio DUR1 of the direct wave power α1 to the sum β1 is calculated by the following mathematical formula 1. In the case of CIR1 shown in FIG. 4, the time length of CIR1 is T_N = 6, and the time length of the head part is T_H = 1.

  Similarly, in CIR2 shown in FIG. 4, assuming that the time length of CIR2 is T_N, the time length of the head of CIR2 is T_H, the power of the direct wave is α2, and the power sum of the delay waves is β2, the power sum of the delay waves β2 The ratio DUR2 of the direct wave power α2 with respect to is calculated by the following formula 2. In the case of CIR2 shown in FIG. 4, the time length of CIR2 is T_N = 6, and the time length of the head portion of CIR2 is T_H = 1.

  Note that the direct-wave powers α1 and α2 are not limited to instantaneous power at a certain time. For example, when there are a plurality of times that can be regarded as the head of the CIR, the powers α1 and α2 of the direct waves are calculated by adding the powers at a plurality of times as in the sums β1 and β2 of the delayed waves. Also good.

  Then, the FPGA 132 selects the antenna having the maximum calculated ratio DUR as the antenna used for estimation of the start timing of the radio signal. For example, when DUR1 ≧ DUR2, it is determined that the estimation accuracy of the head timing estimated from the reception signal of the antenna 112 of the first communication unit 110 is high. Thus, the FPGA 132 selects the antenna 112. When DUR1 <DUR2, it is determined that the estimation accuracy of the head timing estimated from the reception signal of the antenna 122 of the second communication unit 120 is high. Thus, the FPGA 132 selects the antenna 122.

  Finally, the FPGA 132 estimates the start timing of the wireless signal using the preamble unit 50 of the wireless signal received by the antenna with the highest ratio DUR. For example, when the FPGA 132 selects the antenna 112 of the first communication unit 110 as the antenna with which the ratio DUR is maximized, the FPGA 132 estimates the head timing T_EST1 of the received signal of the antenna 112. In addition, when the FPGA 132 selects the antenna 122 of the second communication unit 120 as the antenna with which the ratio DUR is maximum, the FPGA 132 estimates the head timing T_EST2 of the received signal of the antenna 122.

  Note that the FPGA 132 may estimate the head timing in advance before selecting the antenna, instead of estimating the head timing of the received signal after selecting the antenna having the maximum ratio DUR. For example, when the FPGA 132 estimates the CIR 1, the FPGA 132 also estimates the head timing T_EST 1 of the received signal of the antenna 112 and stores the estimated timing T_EST 1 in the storage unit 134. When the FPGA 132 estimates the CIR 2, the FPGA 132 also estimates the start timing T_EST 2 of the received signal of the antenna 122 and stores the estimated timing T_EST 2 in the storage unit 134. Then, after the antenna 132 is selected based on the channel impulse response, the FPGA 132 may acquire the head timing corresponding to the received signal of the selected antenna from the storage unit 134 and use it.

  In general, equalization processing is performed before packet signal processing on a received signal that has passed through a multipath propagation path in wide area wireless communication. The equalization process coherently combines the components of the multipath. Therefore, when an antenna is selected in order to reduce the packet error rate during channel decoding, it is generally effective to select the antenna based on the multipath power sum criterion instead of the DUR criterion.

  For example, in a communication unit having two antennas, assuming that the sum of power in one antenna is SUM1 and the sum of power in another antenna is SUM2, SUM1 and SUM2 are calculated by the following Equation 3.

  Then, by comparing SUM1 and SUM2 and selecting the larger antenna, it is possible to reduce the packet error rate in the signal processing of the equalized received signal. Table 1 below shows examples of antenna selection criteria that are advantageous in the above-described packet decoding. In the case of the above-described power sum reference, as shown in Table 1, if SUM1 is larger than SUM2, the antenna 112 is selected regardless of the magnitude of DUR. If SUM2 is larger than SUM1, antenna 122 is selected.

  On the other hand, in the present embodiment, components other than the head portion of the CIR are assumed to be error factors when estimating the head timing of the received signal. In that case, even if SUM1 <SUM2, if DUR1 ≧ DUR2, the antenna with the worse packet error rate is selected, and the reception signal of the antenna is positively used to make the head timing of the reception signal more accurate. Can be estimated well. In addition, since the accuracy of estimating the start timing is improved, the accuracy of position estimation of the wireless terminal 20 based on the time information of the start timing is also improved.

  Table 2 below shows an example of an antenna selection criterion that is advantageous in the above-described head timing estimation. In the case of the DUR standard described above, as shown in Table 2, if DUR1 is larger than DUR2, the antenna 112 is selected regardless of the magnitude of SUM. If DUR2 is larger than DUR1, antenna 122 is selected.

(Storage unit 134)
The storage unit 134 is a device for storing information related to the wireless station 10. For example, the storage unit 134 stores data output in the process of the FPGA 132 and data such as various applications.

  The configuration example of the wireless communication apparatus according to the embodiment of the present invention has been described above with reference to FIGS. Subsequently, an operation example of the wireless communication apparatus according to the embodiment of the present invention will be described.

<< 3. Operation example >>
Hereinafter, an operation example of the wireless communication apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 5 is a sequence showing an operation example of the wireless station 10 which is the wireless communication apparatus according to the embodiment of the present invention.

  As shown in FIG. 5, first, the communication unit 100 of the wireless station 10, that is, the first communication unit 110 and the second communication unit 120, receive a wireless signal from the wireless terminal 20 (step S1000). After step S1000, the processes of steps S1004 to 1016 and the processes of steps S1020 to S1032 can be performed in parallel.

  As the first parallel processing, first, the control unit 130 performs cross-correlation processing on the preamble unit 50 of the radio signal received by the first communication unit 110 (step S1004). The controller 130 estimates the channel impulse response CIR1 by cross-correlation processing (step S1008). The control unit 130 calculates the power α1 at the head of CIR1 and the power sum β1 other than the head (step S1012). The control unit 130 calculates a power ratio DUR1 based on the calculated power α1 and power sum β1 (step S1016).

  As the second parallel processing, first, the control unit 130 performs cross-correlation processing on the preamble unit 50 of the wireless signal received by the second communication unit 120 (step S1020). The controller 130 estimates the channel impulse response CIR2 by cross-correlation processing (step S1024). The control unit 130 calculates the power α2 at the head of CIR2 and the power sum β2 other than the head (step S1028). The control unit 130 calculates a power ratio DUR2 based on the calculated power α2 and power sum β2 (step S1032). Thus, the control unit 130 ends the parallel processing.

  After completing the parallel processing, the control unit 130 compares the sizes of DUR1 and DUR2 (step S1036). When DUR1 is larger than DUR2 (step S1036 / YES), control unit 130 determines to use the radio signal received by first communication unit 110 for head timing estimation (step S1040). When DUR1 is smaller than DUR2 (step S1036 / NO), control unit 130 determines to use the radio signal received by second communication unit 120 for head timing estimation (step S1044).

  The operation example of the wireless communication apparatus according to the embodiment of the present invention has been described above with reference to FIG.

  The embodiments of the present invention have been described above with reference to FIGS. Then, the modification concerning an embodiment of the present invention is explained.

<< 4. Modified example >>
Hereinafter, some modifications of the embodiment of the present invention will be described. In addition, each modification described below may be independently applied to the embodiment of the present invention, or may be applied to the embodiment of the present invention in combination. Each modification may be applied instead of the configuration described in the embodiment of the present invention, or may be additionally applied to the configuration described in the embodiment of the present invention.

(First modification)
In the above-described embodiment, the example in which the FPGA 132 calculates the power ratio DUR using the power of the direct wave and the power of the delayed wave as they are, but the FPGA 132 weights each of the power of the direct wave and the delayed wave. The power ratio DUR may be calculated after application. For example, the FPGA 132 sets a weight according to the passage of time, and multiplies the power of the direct wave and the power of the delay wave by the weight. More specifically, the FPGA 132 sets the weight for the direct wave power to 1 and sets the weight for the delayed wave power to be 0.75, 0.50, and 0.25 as time passes. When the weight is WEI (k), the ratio DUR1 of the direct wave power α1 to the delayed wave power sum β1 and the ratio DUR2 of the direct wave power α2 to the delayed wave power sum β2 are expressed by the following Equation 4. It is calculated.

  If the time length for calculating the power of the delay wave is set to be long, the number of powers to be added when calculating the power sum of the delay wave is increased. In that case, low-importance power is also included in the power sum, which affects the calculation accuracy of the power ratio DUR. Therefore, as described above, the FPGA 132 multiplies the power of the direct wave and the delayed wave by a weight corresponding to the elapsed time. Even when the time length is set to be long, the influence degree can be reduced by setting the weight of the low importance power to be small. Therefore, the FPGA 132 can select the antenna more appropriately by setting the weight.

(Second modification)
Although the above-mentioned embodiment explained an example which control part 130 chooses one antenna, control part 130 does not need to choose one antenna. More specifically, in the above-described embodiment, the control unit 130 selects one antenna based on the power ratio DUR calculated by each of the plurality of antennas, and sets the head timing based on the radio signal received by the antenna. Calculated. In the second modification, the control unit 130 sets the ratio DUR of the power calculated by each of the plurality of antennas as a weight indicating the reliability. Then, the control unit 130 may calculate the start timing by applying the weight to the start timing estimated based on the wireless signal received by each antenna.

  For example, the control unit 130 sets the power ratio in the first communication unit 110 as DUR1 and the start timing as T_EST1. Further, the control unit 130 sets the power ratio in the second communication unit 120 as DUR2 and the head timing as T_EST2. The start timing T_EST_COM to which the weight indicating the reliability is applied is calculated by the following formula 5.

  As described above, the control unit 130 applies a weight based on the ratio DUR to the head timing calculated for each of a plurality of antennas without selecting one antenna, thereby achieving higher reliability. The start timing can be calculated. Furthermore, the position of the wireless terminal 20 is estimated more accurately by using the time information of the head timing with higher reliability calculated by the control unit 130.

(Third modification)
In the above-described embodiment, an example in which the control unit 130 performs signal processing on one wireless packet has been described. However, the control unit 130 may perform signal processing on a plurality of wireless packets. For example, the control unit 130 performs signal processing on N_STA packets included in a time interval in which the time variation of the propagation path can be regarded as quasi-static as the wireless terminal 20 moves. More specifically, the control unit 130 calculates CIR1 (k) and CIR2 (k) of each of N_STA packets, and calculates CIR1_AVE (k) and CIR2_AVE (k) averaged by N_STA packets. Based on the calculated CIR1_AVE (k) and CIR2_AVE (k), the control unit 130 further calculates DUR1_AVE and DUR2_AVE. Then, the control unit 130 compares DUR1_AVE with DUR2_AVE, and selects the larger antenna.

  As described above, the control unit 130 selects an antenna based on a result of performing signal processing on a plurality of radio packets, thereby reducing an antenna selection error caused by thermal noise included in the received radio signal. be able to. By reducing the antenna selection error, the control unit 130 can estimate the head timing more accurately. Furthermore, the position of the wireless terminal 20 is estimated more accurately in the TDOA method, the TOA method, or the like by using the time information of the head timing that is accurately estimated by the control unit 130.

  Hereinabove, the modification according to the embodiment of the present invention has been described. Subsequently, the hardware configuration of the radio station 10 according to the embodiment of the present invention will be described.

<< 5. Hardware configuration >>
Finally, the hardware configuration of the wireless communication apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing an example of a hardware configuration of the wireless station 10 which is a wireless communication apparatus according to an embodiment of the present invention. Information processing by the wireless station 10 according to the embodiment of the present invention is realized by cooperation of software and hardware described below.

  The wireless station 10 includes a central processing unit (CPU) 101, a read only memory (ROM) 103, and a random access memory (RAM) 105. The wireless station 10 further includes a storage device 107 and a network interface 109.

  The CPU 101 functions as an arithmetic processing device and a control device, and controls the overall operation within the radio station 10 according to various programs. Also, the CPU 101 may be a microprocessor. The ROM 103 stores programs used by the CPU 101, calculation parameters, and the like. The RAM 105 temporarily stores programs used in the execution of the CPU 101, parameters that change as appropriate during the execution, and the like. These are mutually connected by a host bus configured of a CPU bus and the like. CPU101, ROM103, and RAM105 can implement | achieve the function of the control part 130 demonstrated with reference to FIG. 3, for example.

  The storage device 107 is a device for storing data. The storage device 107 may include a storage medium, a recording device that records data in the storage medium, a reading device that reads data from the storage medium, and a deletion device that deletes data recorded in the storage medium. The storage device 107 is configured of, for example, a hard disk drive (HDD) or a solid storage drive (SSD), a memory having an equivalent function, or the like. The storage device 107 drives the storage and stores programs executed by the CPU 101 and various data. For example, the storage apparatus 107 can realize the function of the storage unit 134 described with reference to FIG.

  The network interface 109 is a communication interface configured with, for example, a communication device for connecting to a network. Such a communication interface may be, for example, a short distance wireless communication interface such as Bluetooth (registered trademark) or ZigBee (registered trademark), a wireless local area network (LAN), Wi-Fi (registered trademark), or a mobile communication network (LTE, 3G). The network interface 109 may also be a wired communication device that performs wired communication. For example, the network interface 109 can realize the function of the communication unit 100 described with reference to FIG.

  The hardware configuration example of the wireless communication apparatus has been described above with reference to FIG.

<< 6. End >>
As described above, in the wireless communication apparatus according to the embodiment of the present invention, first, each of the plurality of antennas of the communication unit 100 receives a wireless signal from another wireless terminal 20. The control unit 130 performs signal processing for estimating the impulse response of the propagation path for the radio signal. Based on the result of the signal processing, the control unit 130 calculates the ratio of the direct wave power to the delayed wave. And the control part 130 can select the antenna from which the said ratio becomes the maximum.

  As a result, the control unit 130 can calculate the leading timing of the radio signal more accurately based on the radio signal received by the selected antenna.

  Therefore, it is possible to provide a new and improved wireless communication apparatus and program capable of estimating the head timing of the received signal with higher accuracy.

<< 7. Supplement >>
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

  Note that each step in the processing of the wireless communication system of the present specification does not necessarily have to be processed in time series in the order described as the flowchart. For example, each step in the processing of the wireless communication system may be processed in an order different from the order described as the flowchart, or may be processed in parallel. Further, additional processing steps may be employed, and some processing steps may be omitted.

  In addition, hardware, such as a mobile terminal such as a smartphone and a tablet, and a CPU, a ROM, and a RAM incorporated in the wireless terminal 20 according to the present embodiment, exhibit functions equivalent to those of the above-described configuration of the wireless station 10. Computer programs can also be created. A storage medium storing the computer program is also provided.

DESCRIPTION OF SYMBOLS 10 Radio station 20 Wireless terminal 100 Communication part 110 1st communication part 112 Antenna 114 Demodulator 116 ADC
120 Second communication unit 122 Antenna 124 Demodulator 126 ADC
130 control unit 132 FPGA
134 storage unit

Claims (8)

A communication unit having a plurality of antennas for receiving radio signals from other radio terminals;
Performing signal processing for estimating an impulse response of a propagation path for each of the radio signals received by the plurality of antennas, and calculating a ratio of direct wave power to delayed wave power based on the result of the signal processing; A control unit that selects the antenna having the maximum ratio as an antenna to be used for estimation of the start timing of the radio signal;
A wireless communication device comprising:   The controller according to claim 1, wherein the control unit calculates the power of the head portion of the impulse response as the power of the direct wave, and calculates the sum of powers of the impulse response other than the head portion as the power of the delay wave. Wireless communication device.   The wireless communication apparatus according to claim 1, wherein the control unit performs cross correlation processing on the wireless signal using a known signal, and estimates the impulse response based on a result of the cross correlation processing.   The wireless communication apparatus according to claim 3, wherein the control unit performs the cross-correlation process on a preamble unit of the wireless signal using the known signal.   The wireless communication apparatus according to claim 4, wherein the preamble unit is known between the wireless communication apparatus and the other wireless terminal.   The radio communication apparatus according to claim 4, wherein the control unit estimates the start timing of the radio signal using the preamble part of the radio signal received by the antenna having the maximum ratio.   The wireless communication apparatus according to claim 1, wherein the control unit sets a weight according to an elapsed time, and applies the weight to the power of the direct wave and the power of the delayed wave. Computer,
A communication unit having a plurality of antennas for receiving radio signals from other radio terminals;
Performing signal processing for estimating an impulse response of a propagation path for each of the radio signals received by the plurality of antennas, and calculating a ratio of direct wave power to delayed wave power based on the result of the signal processing; A control unit that selects the antenna having the maximum ratio as an antenna to be used for estimation of the start timing of the radio signal;
Program to function as

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