JP2019128313A - Wireless communication device, wireless communication system, and program - Google Patents

Abstract

To realize a more precise estimation of the position of a wireless terminal.SOLUTION: The wireless communication device includes: a communication unit for receiving a packet from another wireless terminal; and a controller for calculating a first top timing of a packet, using a preamble part of the packet, and calculating a second top timing based on the result obtained by performing mutual correlation processing by the symbol of the payload part of the packet and a known symbol, using the first top timing.SELECTED DRAWING: Figure 3

Description

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

  In recent years, a technique for estimating the position of a terminal that is a transmission source of a packet based on information about a received packet has been developed. As a specific estimation method, there is a method in which the position estimation terminal estimates the position of the terminal of the packet transmission source based on the reception timing of the received packet. There is also a method in which the position estimation terminal estimates the position of the terminal that is the transmission source of the packet based on the received signal power of the packet or the 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, first, the reception timing of a packet is estimated by an STF (Short Training Field) placed at the beginning of the packet. Then, a technique is disclosed in which the reception timing of the packet estimated in STF is corrected by LTF (Long Training Field) located behind STF. Since the LTF is composed of LTF1 and LTF2, if the accuracy of the result corrected by the LTF1 is insufficient, it can be corrected again by the LTF2.

  Further, for reference, there is also a method of using information on a packet by the method of Patent Document 2 below or measuring a distance by the methods of Patent Documents 3 and 4 below. For example, Patent Document 2 below discloses a technique for calculating a delay time of a network by transmitting a packet storing specific data in a payload portion and detecting the data by a terminal that has received the packet. .

  Further, Patent Document 3 below discloses a technique for measuring the distance between a distance measurement device and a measurement object based on the result of correlation calculation between a signal received from the measurement object and a known reference signal. ing.

  Further, Patent Document 4 below discloses a technique for estimating the position of a user apparatus based on the result of calculating the arrival time of a packet using a preamble of the packet and the like.

International Publication No. 2012/042875 JP 2010-252198 A JP 2010-066235 A Special table 2011-510265 gazette

  However, in the technique of Patent Document 1, when the accuracy of the reception timing corrected again using LTF 2 is lower than the expected accuracy, the reception timing can not be further corrected. Therefore, the position of the wireless terminal estimated based on the reception timing may 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 position of a wireless terminal with higher accuracy. To provide a wireless communication system and a program.

  In order to solve the above problem, according to one aspect of the present invention, a first head timing of the packet is calculated using a communication unit that receives the packet from another wireless terminal, and a preamble unit of the packet. A wireless communication apparatus, comprising: a control unit that calculates a second head timing based on a result of performing cross correlation processing using a symbol of a payload portion of the packet and a known symbol using the first head timing. Is done.

  The control section divides the payload section into a plurality of areas, performs the cross-correlation processing on each of one or more of the symbols constituting each section to obtain a plurality of cross-correlation waveforms, and The second start timing may be calculated on the basis of the correlation peak position of the averaged cross-correlation waveform.

  The control unit performs a process of acquiring the averaged cross-correlation waveform for each of the plurality of packets acquired by the communication unit repeating reception of the packet a plurality of times, and acquiring the plurality of acquired The second head timing may be calculated based on a cross correlation waveform obtained by further averaging the averaged cross correlation waveform.

  The control unit may perform cross-correlation processing a number of times according to the number of symbols in the payload portion.

  The symbol of the payload section is known to be known between the other wireless terminal and the wireless communication device, or information of the symbol as it becomes known between the other wireless terminal and the wireless communication device Exchanges may be made.

  The communication unit may receive a notification indicating the number of times the packet is received from a server that estimates the position of the other wireless terminal.

  The control unit may calculate the reception time of the packet based on the second head timing.

  The control unit may obtain a transmission time of the packet included in the packet.

  The communication unit may transmit the reception time to the server.

  The communication unit may transmit the transmission time to the server.

  Further, to solve the above problems, according to another aspect of the present invention, a wireless terminal that is a target of position estimation and transmits a packet used for the position estimation, and receives the packet from the wireless terminal, The first head timing of the packet is calculated using the preamble portion of the packet, and based on the result of performing the cross correlation process using the symbol of the payload portion of the packet and the known symbol using the first head timing, A wireless communication device that calculates a second head timing of the packet; and the position estimation of the wireless terminal based on a reception time at which the wireless terminal transmits the packet and the wireless communication device receives the packet A wireless communication system having an information processing device is provided.

  The information processing apparatus may perform the position estimation using a transmission time when the wireless terminal transmits the packet and a reception time when the wireless communication apparatus receives the packet.

  Also, in order to solve the above problems, according to another aspect of the present invention, a computer, a communication unit for receiving a packet from another wireless terminal, and a preamble unit of the packet are used to perform the first processing of the packet. A control unit that calculates a head timing and calculates a second head timing based on a result of performing cross correlation processing using a symbol of a payload portion of the packet and a known symbol using the first head timing. A program is provided to make it happen.

  As described above, according to the present invention, it is possible to estimate the position of the wireless terminal more accurately.

It is explanatory drawing which shows the outline | summary of the radio | wireless communications system which concerns on embodiment of this invention. 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 a cross correlation waveform concerning the embodiment. It is a sequence diagram which shows the operation example of the radio | wireless communications system concerning the embodiment. 5 is a flowchart showing an operation example of the wireless terminal according to the embodiment. It is a flowchart which shows the operation example of the base station which concerns on the embodiment. It is a flowchart which shows the operation example of the base station which concerns on the embodiment. It is the block diagram which showed the hardware structural example of the base station which concerns on the same 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 Wireless Communication System>
Embodiments of the present invention relate to a wireless communication system that uses multiple base stations to estimate the position of a wireless terminal. Below, the outline | summary of the radio | wireless communications system which concerns on embodiment of this invention is demonstrated, referring 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 according to the present embodiment is a wireless local area network (LAN) system (for example, a wireless LAN system conforming to IEEE 802.11), and includes a plurality of base stations 10 and wireless terminals 20. And a server 30.

  The wireless communication system relates to the calculation of the leading timing of the received signal used for position estimation based on the packet transmission and reception time. For example, in the wireless communication system, a plurality of base stations 10 whose time synchronization is established perform packet transmission / reception with the wireless terminal 20. Then, the server 30 detects the time when the wireless terminal 20 transmits a packet to each base station 10 (hereinafter also referred to as transmission time) and the time when each base station 10 receives a packet (hereinafter, reception time). Position of the wireless terminal 20 is estimated.

  As a method for the server 30 to estimate the position of the wireless terminal 20 based on the transmission time and the reception time described above, for example, TDOA (Time Difference of Arrival) that can estimate the position based only on the reception time without the transmission time is used. And a TOA (Time of Arrival) method capable of estimating the position based on the transmission time and the reception time.

  Here, 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 radio terminal 20 by the base 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 signal unit 52 is a symbol that includes control information including the transmission rate of the payload unit 54 and the packet length. 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 portion 54 is a signal waveform longer than that of the preamble portion 50.

  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) Base station 10
The base station 10 is a wireless communication device that communicates with the wireless terminal 20 and the server 30. For example, the base station 10 is connected to the wireless terminal 20 and the server 30 by an arbitrary communication method and performs communication. More specifically, the base station 10 communicates with the wireless terminal 20 by being connected to an external network. The base station 10 communicates with the server 30 by being connected to an external network.

  The communication method of the base station 10 is not particularly limited. For example, the base station 10 may be connected to the wireless terminal 20 by wireless communication. Further, the base station 10 may be connected to the server 30 by wired communication instead of wireless communication. The base station 10 may be configured to communicate directly with the server 30 or may be configured to communicate via a network (or other device).

  Further, the wireless communication system of the present embodiment uses a plurality of base stations such as the base station 10A, the base station 10B, the base station 10C, the base station 10D, and the base station 10E shown in FIG. The plurality of base stations 10 are collectively referred to as a base station group 100. And each base station 10 of the base station group 100 is classified according to its use. For example, the base station 10 </ b> A is classified as a reference station 102 that is a representative base station used for position estimation of the wireless terminal 20. Further, the base station 10B, the base station 10C, and the base station 10D are classified as a base station group 104 that is used for position estimation of the wireless terminal 20 other than the reference station 102. The base station 10E is classified as a base station group 106 that is not used for position estimation of the wireless terminal 20. Although only the base station 10E is shown as the base station group 106 in FIG. 1, the number of the base station group 106 is not limited to one.

  Further, the base station 10 calculates the leading timing of the packet based on information when the packet is transmitted / received to / from the wireless terminal 20. For example, the base station 10 receives a packet from the wireless terminal 20 and calculates the leading timing of the packet as an initial value using the preamble part 50 of the packet. In the following, the head timing calculated as the initial value is referred to as a first head timing.

  Then, the base station 10 calculates the start timing of the packet as the final value based on the result of performing the cross correlation process using the symbol of the payload section 54 of the packet and the known symbol using the first start timing. In the following, the head timing calculated as the final value is referred to as a second head timing. In addition, known symbols used for the cross-correlation processing are known in advance between the base station 10 and the radio terminal 20. Also, even if the symbol is not known in advance between the base station 10 and the wireless terminal 20, the symbol may be made a known symbol by exchanging information regarding the symbol between the base station 10 and the wireless terminal 20. .

(2) Wireless terminal 20
The wireless terminal 20 is a wireless terminal that communicates with the base station 10. For example, the wireless terminal 20 transmits and receives packets to and from the base 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 used for position estimation to and from the base station 10.

  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 base station 10. For example, the wireless terminal 20 payloads a symbol sequence known between the wireless terminal 20 and the base station 10 based on application data and information bit sequences known in advance with the base station 10 transmitting and receiving a packet. It generates in section 54. Hereinafter, the known symbol sequence in the payload portion 54 is also referred to as a payload portion preamble.

  Here, it is assumed that the wireless terminal 20 can obtain the information on the setting of the number of symbols N_DS included in the payload portion preamble by decoding the packet received from the reference station 102.

(3) Server 30
The server 30 is an information processing apparatus that communicates with the base station group 100 and controls the operation of the base station group 100. For example, the server 30 classifies the base station group 100. More specifically, the server 30 selects the reference station 102 from the plurality of base stations 10 included in the base station group 100. After selecting the reference station 102, the server 30 classifies the base station 10 (base station group 104) used for position estimation of the wireless terminal 20 and the base station 10 (base station group 106) not used.

  As a method for the server 30 to classify the base station group 100, for example, based on the received signal strength (RSSI) when each base station 10 of the base station group 100 receives the position estimation request packet from the wireless terminal 20, the server 30 30 can be classified. More specifically, when the base station 10 receives the position estimation request packet from the wireless terminal 20, the base station 10 transmits the packet to the server 30 after giving RSSI information to the packet. The server 30 having received the position estimation request packet generates a list of position estimation base stations in descending order of the RSSI value of the RSSI information included in the packet. Then, the server 30 sets the base station 10 with the highest RSSI value in the list as the reference station 102, the base stations 10 except the reference station 102 whose RSSI value exceeds the predetermined threshold, the base station group 104, and the RSSI value with the predetermined threshold A base station 10 not exceeding N will be referred to as a base station group 106.

  The server 30 is an information processing apparatus having a function of estimating the position of the wireless terminal 20. For example, the server 30 estimates the position of the wireless terminal 20 based on at least one of the transmission time when the wireless terminal 20 transmits a packet and the reception time when the base station 10 receives the packet. More specifically, the server 30 determines the transmission time when the wireless terminal 20 transmits a packet from the base station 10 of the base station group 104 and the base station 10 of the base station group 100 and the base station 10 transmits the packet. Receive the received time. And the server 30 estimates the position of the radio | wireless terminal 20 by methods, such as the TOA system mentioned above based on the TDOA system mentioned above based on the said reception time, or the said transmission time and the said reception time.

  The server 30 also has a function of determining the number of times that the reference station 102 and the base station group 104 transmit / receive a position estimation packet to / from the wireless terminal 20. For example, the server 30 determines the number of times based on an SN ratio (Signal to Noise power Ratio). More specifically, the server 30 calculates the SN ratio based on the RSSI information included in the position estimation request packet received from the base station 10. Then, the server 30 determines the number of times that the reference station 102 and the base station group 104 transmit / receive the position estimation packet to / from the wireless terminal 20 in accordance with the base station 10 having a small SN ratio.

  The outline of the wireless communication system according to the embodiment of the present invention has been described above with reference to FIGS. Subsequently, a configuration example of the base station 10 according to the embodiment of the present invention will be described.

<2. Example of base station configuration>
Hereinafter, a configuration example of the base station 10 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a block diagram showing a configuration example of the base station 10 according to the embodiment of the present invention. As illustrated in FIG. 3, the base station according to the present embodiment includes a communication unit 110, a control unit 120, and a storage unit 130.

(1) Communication unit 110
The communication unit 110 has a function of transmitting and receiving packets. For example, the communication unit 110 transmits and receives packets with the wireless terminal 20. More specifically, the communication unit 110 transmits the position estimation packet and the position information estimated by the server 30 to the wireless terminal 20. The communication unit 110 also receives a position estimation request packet and a position estimation packet from the wireless terminal 20.

  The communication unit 110 also transmits and receives packets to and from the server 30. More specifically, the communication unit 110 receives a notification indicating the number of times the above-described position estimation packet is transmitted / received to / from the wireless terminal 20 from the server 30. In addition, the communication unit 110 transmits at least one of a transmission time and a reception time when transmitted / received to / from the wireless terminal 20 to the server 30.

(2) Control unit 120
The control unit 120 has a function of calculating the leading timing of the packet. In calculating the start timing of the packet, first, the control unit 120 calculates the first start timing. More specifically, the control unit 120 uses the packet preamble unit 50 to calculate the first head timing of the packet. The control unit 120 can determine the reception time of the packet by calculating the first head timing of the packet.

  Next, the control unit 120 calculates a second leading timing. More specifically, the control unit 120 performs cross-correlation processing using the symbol of the payload section 54 of the packet and the known symbol, using the calculated first head timing. At this time, the control unit 120 basically performs cross-correlation processing a number of times corresponding to the number of symbols in the payload unit 54. For example, when the number of symbols in the payload portion 54 is N_DS, the control unit 120 performs the cross-correlation process N_DS times.

  However, the control unit 120 has a function of dividing the payload unit 54 into a plurality of regions, and the number of symbols constituting each division is not necessarily one. For example, one segment may include two or more symbols. In that case, the control unit 120 performs the cross-correlation process for one section, not for one symbol. Therefore, the number of symbols included in the payload portion 54 may not match the number of times that the control unit 120 performs cross-correlation processing.

  Then, as a result of the cross-correlation process for the plurality of symbols, the control unit 120 acquires N_DS cross-correlation waveforms. Here, the cross correlation waveform will be described with reference to FIG. FIG. 4 is an explanatory view showing an example of a cross correlation waveform according to the embodiment of the present invention. The graph shown in FIG. 4 shows the cross correlation waveform after averaging the N_DS cross correlation waveforms calculated by the control unit 120 by the cross correlation process. The vertical axis represents the cross-correlation value after averaging the N_DS cross-correlation waveforms, and the horizontal axis represents the time difference. Note that the period of the cross-correlation waveform with respect to the time waveform of one symbol is twice the symbol time length T_SYM.

  The control unit 120 calculates the graph shown in FIG. 4 by performing an averaging process on the N_DS cross-correlation waveforms acquired by the cross-correlation process. The control unit 120 performs the averaging process on the N_DS cross-correlation waveforms acquired by the cross-correlation process, so that the difference between the peak 60 and the sub-peak 62 of the cross-correlation waveform is compared with the cross-correlation waveform before the averaging. And grow. Then, the control unit 120 calculates the second head timing based on the position of the peak 60 of the averaged cross-correlation waveform.

  In addition, when the communication unit 110 repeatedly receives packets a plurality of times, the control unit 120 performs cross correlation processing and the above-described averaging processing on each of the plurality of packets acquired by repeating reception of the packets. And get multiple cross-correlation waveforms. Then, the control unit 120 calculates the second leading timing based on the position of the peak 60 of the cross correlation waveform obtained by further averaging the plurality of averaged cross correlation waveforms obtained.

  Also, the control unit 120 has a function of acquiring the transmission / reception time of the packet. For example, the control unit 120 acquires a transmission time when the wireless terminal 20 transmits a packet to the base station 10 and a time when the base station 10 receives the packet. More specifically, since the transmission time at which the radio terminal 20 transmits the position estimation packet is included in the position estimation packet, the control unit 120 demodulates the packet when receiving the position estimation packet. Get the send time. Further, the control unit 120 calculates the reception time based on the second head timing.

  The control unit 120 calculates the second start timing by correcting the first start timing calculated by the preamble unit 50 using the start timing calculated based on the peak position of the cross-correlation waveform. May be The method of correcting the first head timing is not particularly limited. For example, the control unit 120 may combine the start timing calculated based on the position of the peak of the cross correlation waveform and the first start timing, or at the start timing calculated based on the position of the peak of the cross correlation waveform. The position of the first timing may be corrected. In addition, the control unit 120 may use the start timing calculated based on the peak position of the cross-correlation waveform as the second start timing as it is.

  Note that in an environment with a low signal-to-noise ratio where the noise included in the received signal is large, the timing that should be detected as the position of the sub-peak 62 may be erroneously detected as the position of the peak 60 due to the influence of noise. . However, as described above, the difference between the peak 60 and the sub-peak 62 is increased, so that the false detection rate at the position of the peak 60 is reduced, and the base station 10 receives a packet with higher accuracy based on the peak 60. The time can be calculated. Furthermore, the server 30 can reduce the degradation of the position estimation accuracy caused by the estimation error of the reception time by performing the position estimation of the wireless terminal 20 using the reception time.

(3) Storage unit 130
The storage unit 130 is a device for storing information on the base station 10. For example, the storage unit 130 stores data output in the processing of the control unit 120 and data such as various applications.

  The configuration example of the base station 10 according to the embodiment of the present invention has been described above with reference to FIGS. Subsequently, an operation example of the wireless communication system according to the embodiment of the present invention will be described.

<3. Operation example>
Below, the operation example of the radio | wireless communications system which concerns on embodiment of this invention is demonstrated, referring FIGS. FIG. 5 is a sequence showing an operation example of the wireless communication system according to the embodiment of the present invention.

  As shown in FIG. 5, first, the radio terminal 20 transmits a position estimation request packet by broadcasting (step S1000). Among the base stations 10 of the base station group 100, the base station 10 that has received the position estimation request packet from the wireless terminal 20 transmits the position estimation request packet to the server 30 (step S1004). The server 30 that has received the position estimation request packet from the base station of the base station group 100 is based on the information received from each base station 10 and the base station used for position estimation of the wireless terminal 20 other than the reference station 102 and the reference station 102. The station group 104 is selected (step S1008). After selecting the reference station 102, the server 30 notifies the base station 10A selected as the reference station 102 that the reference station 102 has been selected (step S1012). In addition, after selecting the base station group 104, the server 30 notifies the base station 10B, the base station 10C, and the base station 10D selected as the base station group 104 that the base station group 104 has been selected. (Step S1016).

  The reference station 102 transmits a position estimation packet to the base station group 104 and the wireless terminal 20 (step S1020). The wireless terminal 20 that has received the position estimation packet transmits the position estimation packet to the reference station 102 and the base station group 104 (step S1024). Then, the reference station 102 repeats step S1020 and the wireless terminal 20 repeats step S1024 N_P times.

  Here, an operation example of the wireless terminal 20 in step S1020 will be described with reference to FIG. FIG. 6 is a flowchart showing an operation example of the wireless terminal 20 according to the embodiment of the present invention. As shown in FIG. 6, first, the wireless terminal 20 receives the position estimation packet transmitted from the reference station 102 in step S1020 of FIG. 5 (step S2000). The wireless terminal 20 generates N_DS symbols (payload portion preamble) in the payload portion 54 of the packet based on the received packet, the application data known to the reference station 102, and the information bit sequence (step S2004). . Then, the wireless terminal 20 broadcasts a packet including the generated N_DS symbols as a position estimation packet (step S2008).

  In addition, an operation example of each of the base station 10A, the base station 10B, the base station 10C, and the base station 10D in step S1024 will be described with reference to FIG. In addition, since operation | movement of base station 10A, base station 10B, base station 10C, and base station 10D in step S1024 is respectively the same, it demonstrates as the base station 10 below. FIG. 7 is a flowchart showing an operation example of the base station 10 according to the embodiment of the present invention. As shown in FIG. 7, first, the base station 10 receives the position estimation packet transmitted from the wireless terminal 20 in step S1024 of FIG. 5 (step S3000). The base station 10 calculates the first head timing of the packet using the preamble part 50 of the received packet (step S3004). The base station 10 extracts waveforms of N_DS symbols included in the payload part preamble (step S3008). The base station 10 performs a cross-correlation process with a known symbol waveform for each extracted symbol waveform (step S3012). After performing the cross correlation process, the base station 10 averages the N_DS cross correlation waveforms calculated by the cross correlation process to obtain a first cross correlation waveform C_AVE (τ) (step S3016). The base station 10 calculates a first sampling timing from the peak position of the first cross correlation waveform C_AVE (τ) (step S3020). The base station 10 corrects the first head timing of the packet using the calculated first sampling timing, and calculates the second head timing (step S3024).

  As described above, the base station 10 corrects the first head timing of the packet calculated using the preamble unit 50 using the first sampling timing to obtain the second head timing of the packet with higher accuracy. Can be calculated. Then, the base station 10 can estimate the packet reception time with higher accuracy based on the second head timing.

  A process for the base station 10 to calculate a more accurate sampling timing will be described with reference to FIG. FIG. 8 is a flowchart showing an operation example of the base station 10 according to the embodiment of the present invention. First, the base station 10 repeats N_P first cross-correlation waveforms C_AVE (τ by the base station 102 repeating packet transmission / reception with the radio terminal 20 and each base station 10 averaging the cross-correlation waveforms N_P times). Get). Then, as shown in FIG. 8, the base station 10 further averages the N_P first cross correlation waveforms C_AVE (τ) to obtain a second cross correlation waveform C_AVE (τ) (step S4000). The base station 10 calculates the second sampling timing from the peak position of the second cross-correlation waveform C_AVE (τ) (step S4004). The base station 10 corrects the first head timing of the packet using the calculated second sampling timing, and calculates the final second head timing (step S4008).

  As described above, the base station 10 corrects the first head timing of the packet calculated using the first sampling timing using the second sampling timing to obtain the second packet with higher accuracy. The head timing of can be calculated. Then, the base station 10 can estimate the packet reception time with higher accuracy based on the second head timing.

  Each base station 10 transmits to the server 30 the transmission time when the reference station 102 transmitted the packet and the reception time of the packet calculated based on the second head timing as described above (step S1028). The server 30 estimates the position of the wireless terminal 20 based on the transmission / reception time of the received packet (step S1032), and transmits the estimated position information to the reference station 102 (step S1036). Then, the reference station 102 transmits the received position information to the wireless terminal 20 (step S1040).

  In the above example, the operation example of the wireless communication system in which the reference station 102 performs broadcast transmission of the position estimation packet (step S1020 in FIG. 5) has been described. On the other hand, the wireless communication system may be configured as a wireless communication system triggered by the wireless terminal 20 transmitting a position estimation request packet by broadcast transmission (step S1000 in FIG. 5). In that case, the wireless terminal 20 generates a position estimation request packet including a payload portion preamble that becomes known between the wireless terminal 20 and the base station group 100 in step S1000 of FIG. Broadcast request packet. Then, each base station 10 that has received the position estimation request packet performs a cross-correlation process with the waveform of the known symbol for each waveform of the symbol in the payload portion, and based on the result of the cross-correlation process, the reception time of the packet Calculate

  After calculating the packet reception time, the base station 10 transmits to the server 30 the reception time, the RSSI information, and the transmission time at which the wireless terminal 20 acquired when demodulating the position estimation packet transmits the packet. The server 30 performs three-dimensional position estimation of the wireless terminal 20 based on a position estimation method mainly using time information, using the reception time and transmission time of the base station having a high RSSI value included in the RSSI information. . Then, the server 30 transmits the position information to the base station 10 with the highest RSSI value, and the base station 10 transmits the position information to the radio terminal 20.

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

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

<4. Modified example>
Hereinafter, modifications of the embodiment of the present invention will be described. In addition, the modification demonstrated below may be applied independently to embodiment of this invention, and may be applied to embodiment of this invention in combination. The modification may be applied in place 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.

  In the above-described embodiment, the application data that is the base of the payload part preamble has been described in advance between the wireless terminal 20 and the base station 10. However, the application data is the wireless terminal 20 and the base station 10. And may not be known in advance. For example, the wireless terminal 20 demodulates the position estimation packet received from the reference station 102 in step S1020 of FIG. 5 and retransmits the packet reproduced as the same time waveform to the reference station 102 and the base station group 104. It is also good.

  As described above, by using the method in which the wireless terminal 20 retransmits the position estimation packet received from the reference station, the wireless terminal 20 and the base station 10 do not share application data in advance. It can transmit and receive.

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

<5. Hardware configuration>
Finally, the hardware configuration of the base station 10 according to the embodiment of the present invention will be described with reference to FIG. FIG. 9 is a block diagram illustrating an example of a hardware configuration of the base station 10 according to the embodiment of the present invention. Information processing by the base station 10 according to the embodiment of the present invention is realized by cooperation of software and hardware described below.

  The base station 10 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 103, and a RAM (Random Access Memory) 105. Further, the base station 10 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 base 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 120 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 130 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 is, for example, a short-range wireless communication interface such as Bluetooth (registered trademark) or ZigBee (registered trademark), a communication such as a wireless LAN, Wi-Fi (registered trademark), or a mobile communication network (LTE, 3G). It is an interface. The network interface 109 may also be a wired communication device that performs wired communication.

  The example of the hardware configuration of the base station 10 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, the communication unit 110 receives a packet from another wireless terminal 20. Using the preamble part 50 of the packet, the control unit 120 calculates the first head timing of the packet. Using the first head timing, the control unit 120 performs cross-correlation processing using the symbols in the payload portion 54 of the packet and the known symbols. Then, based on the result of the cross correlation process, the control unit 120 can calculate the second head timing.

  As a result, the control unit 120 can calculate the second head timing with higher accuracy than the first head timing. Furthermore, when the control unit 120 calculates the reception time of the packet using the second head timing with higher accuracy, the server 30 can estimate the position of the wireless terminal 20 more accurately.

  Therefore, it is possible to provide a new and improved wireless communication apparatus, wireless communication system, and program capable of estimating the position of the wireless terminal 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.

  Further, it is possible to create a computer program for causing hardware such as a CPU, a ROM, and a RAM built in a mobile terminal such as a smartphone or a tablet to perform the same functions as the components of the base station 10 described above. A storage medium storing the computer program is also provided.

10 base station 20 wireless terminal 30 server 110 communication unit 120 control unit 130 storage unit

Claims (13)

A communication unit that receives packets from other wireless terminals;
The first head timing of the packet is calculated using the preamble portion of the packet, and based on the result of performing the cross correlation process using the symbol of the payload portion of the packet and the known symbol using the first head timing, A control unit for calculating the second head timing;
A wireless communication device comprising:   The control unit divides the payload portion into a plurality of regions, performs the cross-correlation processing for each of one or more of the symbols constituting each division, acquires a plurality of cross-correlation waveforms, The wireless communication apparatus according to claim 1, wherein the cross correlation waveform is averaged, and the second head timing is calculated based on a correlation peak position of the averaged cross correlation waveform.   The control unit performs a process of acquiring the averaged cross-correlation waveform for each of the plurality of packets acquired by the communication unit repeating reception of the packet a plurality of times, and acquiring the plurality of acquired The radio communication apparatus according to claim 2, wherein the second head timing is calculated based on a cross-correlation waveform obtained by further averaging the averaged cross-correlation waveform.   The wireless communication apparatus according to claim 2, wherein the control unit performs cross-correlation processing a number of times corresponding to the number of symbols in the payload portion.   The symbol information of the payload part is known between the other wireless terminal and the wireless communication device, or known between the other wireless terminal and the wireless communication device. The wireless communication device of claim 1, wherein exchange is performed.   The wireless communication apparatus according to claim 1, wherein the communication unit receives, from a server that estimates the position of the other wireless terminal, a notification indicating the number of times the packet is received.   The wireless communication apparatus according to claim 6, wherein the control unit calculates a reception time of the packet based on the second head timing.   The wireless communication apparatus according to claim 6, wherein the control unit acquires a transmission time of the packet included in the packet.   The wireless communication device according to claim 7, wherein the communication unit transmits the reception time to the server.   The wireless communication apparatus according to claim 8, wherein the communication unit transmits the transmission time to the server. A wireless terminal that is a target of position estimation and transmits a packet used for the position estimation;
The packet is received from the wireless terminal, and a preamble portion of the packet is used to calculate a first head timing of the packet, and a cross correlation process using a symbol of the payload portion of the packet and a known symbol is performed at the first head A wireless communication device that calculates a second head timing of the packet based on a result obtained using the timing;
An information processing apparatus that estimates the position of the wireless terminal based on a reception time at which the wireless terminal transmits the packet and the wireless communication apparatus receives the packet;
Wireless communication system.   The wireless communication system according to claim 11, wherein the information processing apparatus performs the position estimation using a transmission time at which the wireless terminal transmits the packet and a reception time at which the wireless communication apparatus receives the packet. Computer,
A communication unit that receives packets from other wireless terminals;
The first head timing of the packet is calculated using the preamble portion of the packet, and based on the result of performing the cross correlation process using the symbol of the payload portion of the packet and the known symbol using the first head timing, A control unit for calculating the second head timing;
Program to function as

Images