JP2015064232A - Determination device, network node, determination method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an erroneous reference position from being specified when estimating the location of a mobile device in a fingerprint positioning system.SOLUTION: Provided is a determination device for determining the location of a mobile device by comparing an observed value in a mobile device of the quality of radio signals from a plurality of communication devices whose positions are fixed and a reference value for observed values in which the quality of radio signal from each of the plurality of communication devices is previously observed at each of a plurality of reference positions and stored in memory. The determination device generates a plurality of distributions with regard to the observed value in the mobile device of the quality of the radio signal from each of the plurality of communication devices, calculates a correlation value between the plurality of distributions, specifies, on the basis of the correlation value, a reference position to be compared in determining the location of the mobile device from among the plurality of reference positions, and determines the location of the mobile device using a reference value relating to the specified reference position and the observed value.

Description

  The present invention relates to a position estimation technique for a mobile device.

  There is a fingerprint positioning method as a method for specifying the position of a mobile communication device in a multipath environment or a non-line-of-sight environment (see Non-Patent Document 1). In this method, a parameter that can be a fingerprint is acquired in a device whose position is known in advance, and a database is constructed by storing the parameter in association with the position. Specifically, for example, the quality of radio signals from a plurality of fixed communication devices such as base stations is observed in advance at a number of known positions (reference positions) in a wide geographical area, and the observation is performed. Information regarding the value, the transmission source communication device, and the reference position is stored in the database. Here, the quality of the radio signal is, for example, radio wave propagation loss, received signal strength indication (RSSI), or the like.

  In the fingerprint positioning method, for example, an observation value of a radio signal in a mobile device is acquired via a base station, and pattern matching with information stored in a database is performed, so that the mobile communication device's The position is estimated. In this way, in the fingerprint positioning method, a value related to the quality of the wireless signal at the reference position is stored in advance as a fingerprint, and the stored fingerprint is compared with the quality of the observed wireless signal (the fingerprint to be judged). By doing so, the position of the mobile device to be determined is estimated.

  In Patent Document 1, in the fingerprint positioning method, a plurality of reference positions are clustered for each region, reference positions belonging to some clusters are specified, reference values corresponding to the reference positions, and a moving object A technique for comparing the observed values with the apparatus is described. As a result, only the reference values corresponding to some reference positions are compared with the observed values without comparing with the observed values for the reference values corresponding to all the reference positions stored in the database. The amount of calculation related to positioning can be greatly reduced.

Special table 2012-512404 gazette

T. T. et al. Wigren, “Adaptive Enhanced Cell-ID Fingerprinting Localization of Precipitation Position MeasurementEs.EE, Adaptive Clustering of Accurate Location Observations”. Vehicular Technical. , Vol. 56, no. 5, pp 3199-3209

  On the other hand, when the reference position is clustered, the observation data near the cluster boundary has a close value between adjacent clusters. For this reason, it may happen that an adjacent cluster is erroneously selected as a cluster to be compared with the observed value, not the cluster that should be originally selected. And there existed a problem that the position estimation precision of a mobile apparatus will deteriorate by selecting an incorrect cluster.

  The present invention has been made in view of the above problems, and an object of the present invention is to prevent an erroneous reference position from being specified in estimating the position of a mobile device in a fingerprint positioning method.

  In order to achieve the above object, the determination apparatus according to the present invention includes a plurality of communications at each of an observed value in a mobile device of radio signal quality from a plurality of communication devices whose positions are fixed and a plurality of reference positions. A determination device for determining a position of the mobile device by comparing a reference value of an observation value in which the quality of a radio signal from each of the devices is observed and stored in advance, in the mobile device, Based on the correlation value, a generation unit that generates a plurality of distributions for the observed value of the quality of the radio signal from each of the plurality of communication devices, a calculation unit that calculates a correlation value between the plurality of distributions, Among the plurality of reference positions, a specifying unit that specifies a reference position to be compared in the determination of the position of the mobile device, and the reference value and the observed value related to the specified reference position are used. Having a determination means for determining the position of the mobile device Te.

  According to the present invention, it is possible to prevent an erroneous reference position from being specified in estimating the position of the mobile device in the fingerprint positioning method.

1 is a diagram illustrating an example of a wireless communication system. The figure which shows the function structural example of a position determination apparatus. The figure which shows the relationship between the position of a mobile terminal and the correlation value between distribution. The figure which shows the hardware structural example of a position determination apparatus. The flowchart which shows the flow of the position determination process of the mobile body apparatus which a position determination apparatus performs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Wireless communication system)
FIG. 1 shows a wireless communication system according to this embodiment. The wireless communication system is a system based on a cellular network, for example, and includes a base station A, a base station B, and a mobile terminal. Moreover, in this radio | wireless communications system, the position determination apparatus connected to the base station A and the base station B via a network exists. In the following description, the position determination device is described as a network node independent of the base station A and the base station B. However, the position determination device may be provided in the base station. Further, in this example, a system including two base stations and one mobile terminal will be described for simplification of explanation, but there may be three or more base stations, and two or more base stations may be present. It is clear that a mobile terminal may be present.

  A mobile terminal is a wireless communication device that can move and has an indefinite position. The mobile terminal transmits or receives a radio signal to / from the base station A or the base station B. Base station A and base station B are fixed wireless communication devices, and communicate with mobile terminals within their communicable range (cell). In the present embodiment, the quality of the radio signal transmitted from the base station A and the base station B and observed at each position is used as a fingerprint, and the position of the mobile terminal is determined.

  FIG. 1 further shows a plurality of reference positions used for determining the position of the mobile terminal by the position determination device. In FIG. 1, the reference position is indicated by a black square and a black circle. In this embodiment, the quality of radio signals from a plurality of base stations is observed in advance at the reference position and stored in the database. Note that the quality of the radio signal includes, for example, radio wave propagation loss, received signal power (Reference Signal Received Power, RSRP), signal-to-interference and noise power ratio (SINR), and the like. Further, the database may exist in the position determination apparatus, may exist as a network node different from the position determination apparatus, or may exist in the base station. Here, the quality of the radio signal observed for each of the plurality of reference positions is stored as a distribution represented by a value indicating the quality and a frequency (ratio) at which the value occurs.

  In addition, the observation of the quality of the radio signal at the reference position is performed by, for example, a mobile terminal having a GPS positioning function or an A-GPS positioning function. In this case, the positioning result by the GPS positioning function or the A-GPS positioning function is used as a reference position, and the observed value of the quality of the radio signal at the reference position is stored in the database as the reference value of the observed value. In this case, the mobile terminal cannot always be observed at the same position. For this reason, for example, the geographical area may be divided into areas of 5 m square, for example, and the data observed in one area may be handled as being observed at the same place. That is, a distribution may be generated by collecting quality observed in a 5 m square area, and one point in the area may be used as a reference position, and the distribution may be stored in a database in association with the reference position.

  The mobile terminal observes the quality of the radio signal from each of the base station A and the base station B, and sends the quality information to the base station (eg, cell ID) of the radio signal source corresponding to the quality. In addition, the base station (for example, serving base station) with which the connection is established is notified. Note that the mobile terminal may observe the quality of the radio signal for a certain period, accumulate the quality information, and then notify the accumulated information to the base station. The base station notified of the information transfers this information to the position determination device.

  Then, the position determination device generates a distribution based on a value indicating the quality of the radio signal in the mobile terminal and a frequency (ratio) at which the value is generated based on the information notified from the mobile terminal, and the distribution And the distribution stored corresponding to the reference position. Then, for example, the position determination device estimates the position of the mobile terminal based on the reference position corresponding to the distribution having the highest correlation with the distribution of the radio signal quality in the mobile terminal. That is, for example, the position determination device determines that the mobile terminal exists at the reference position corresponding to the distribution having the highest correlation with the distribution of the quality of the radio signal in the mobile terminal.

  In such a positioning method, the accuracy of positioning can be improved because the reference position exists in a wide range. On the other hand, if the reference position is set finely in order to improve the positioning accuracy, the reference position to be compared in the determination of the position of the mobile terminal becomes enormous, the calculation amount becomes large, and the position can be specified. Takes a long time to complete. For this reason, the reference position is clustered (grouped) for each region, a cluster is selected according to the roughly estimated position of the mobile terminal, and the reference position included in the cluster is determined as the position of the mobile terminal. Can be specified as a comparison target in the determination. That is, for example, when the base station A is a serving base station, the mobile terminal is considered to exist in a cell that the base station A develops.

  Therefore, the reference position included in the cell area can be specified as the reference position to be compared in the estimation of the position of the mobile terminal. Thus, in this embodiment, the reference positions are clustered depending on which cell the reference position is included in. For example, as shown in FIG. 1, the reference position in the cell developed by the base station A is classified into cluster A, and the reference position in the cell developed by the base station B is classified into cluster B. Such clustering can reduce the amount of calculation or the processing time.

  However, for example, when the mobile terminal exists near the boundary between the cell deployed by the base station A and the cell deployed by the base station B, the quality of the radio signal is determined at a plurality of reference positions close to each other near the cell edge. There may be no significant difference in the distribution of. In such a case, when an adjacent cluster different from the cluster to be originally selected is selected, a distribution comparison is performed between the position where the mobile terminal is located and the reference position apart from the position. Positioning accuracy will deteriorate.

  For this reason, in this embodiment, the distribution of the quality of the radio signal from each of the plurality of base stations observed in the mobile terminal is generated, the correlation value between the distributions is calculated, and the correlation value is , Select and identify at least one cluster. For example, the position determination apparatus generates the distribution of the quality of the radio signal from the base station A and the distribution of the quality of the radio signal from the base station B, which are observed in the mobile terminal.

  Then, the position determination device calculates a correlation value between these distributions and determines whether the correlation value is equal to or greater than a first predetermined value. As a result, when the correlation value is smaller than the first predetermined value, it is considered that the mobile terminal is located at a position close to either the base station A or the base station B and far from the other. Therefore, in this case, the position determination apparatus uses the reference position included in the cell developed by the base station corresponding to the distribution with the larger average distribution as a reference for comparison in determining the position of the mobile terminal. Specify as location.

  On the other hand, when the calculated correlation value is greater than or equal to the first predetermined value, the mobile terminal is considered to be approximately the same distance from each of the base station A and the base station B. Therefore, in this case, the position determination apparatus determines the position of the mobile terminal using at least a part of the reference positions included in the two cells respectively deployed in the base station A and the base station B. To specify a reference position to be compared. Thereby, when the mobile terminal is considered to exist in the vicinity of the cell edge, the distribution of the radio signal quality at the reference position across the two clusters and the distribution of the observed value of the radio signal quality at the mobile terminal Based on this, the position of the mobile terminal is determined. Therefore, it is possible to prevent deterioration in position estimation accuracy due to selection of an incorrect cluster while limiting the reference position used for position determination.

  The position determination device may further determine whether the calculated correlation value is equal to or greater than a second predetermined value that is greater than the first predetermined value. If the calculated correlation value is greater than or equal to the second predetermined value, the mobile terminal is present near the cell edge as compared to the case where the correlation value is greater than or equal to the first predetermined value but smaller than the second predetermined value. It is considered that there is a high probability of Therefore, the position determination apparatus determines a part of the reference position specified when the correlation value is equal to or greater than the first predetermined value but smaller than the second predetermined value, and the calculated correlation value is equal to or greater than the second predetermined value. In the case of determining the position of the mobile terminal, it is specified as a reference position to be compared. Thereby, for example, for a mobile terminal having a high probability of being present near the cell edge, the position is determined using only a limited reference position located near the cell edge. Therefore, the calculation amount or processing time can be reduced.

  Next, the configuration and processing of the position determination device according to this embodiment will be described.

(Functional configuration of position determination device)
FIG. 2 is a block diagram illustrating a functional configuration example of the position determination device. The position determination apparatus includes, for example, an information acquisition unit 201, a reference position information database (DB) 202, a comparison target specifying unit 203, a position determination unit 204, and a position information output unit 205 as its functions.

  The information acquisition unit 201 acquires, from the base station, information on the observation value at the mobile terminal of the radio quality of the radio signal from the base station through the network. At this time, the observation value information is acquired together with information (for example, cell ID) indicating from which base station the radio signal is related. The information acquisition unit 201 may acquire information on the above-described observation values together with the GPS positioning result from a mobile terminal having a GPS positioning function, for example. In this case, the information acquisition unit 201 associates the GPS positioning result with the observed value of the quality of the radio signal, and stores it in the reference position information DB 202 as a reference value. On the other hand, observation value information obtained from a mobile terminal that is the target of the fingerprint positioning method without a GPS positioning result is passed to the comparison target specifying unit 203.

  The reference position information DB 202 stores in advance the reference position, the strength of the quality of the radio signal from each base station, and the frequency observed at the reference position, as a distribution reference value. At this time, the reference position information DB 202 stores, for example, RSRP as quality information. The reference position information DB 202 is, for example, a frequency distribution indicating which RSRP values observed at the reference position are included in a plurality of ranges of RSRP having a width of 1 dBm. The information is memorized. For example, when a plurality of ranges are represented by X [dBm] or more and less than X + 1 [dBm] (where X is an integer) and RSRP is −89.5 dBm, this RSRP is a range in which X is specified by −90. include. Therefore, the reference position information DB 202 updates the frequency distribution by increasing the frequency of X = −90 by 1. By repeating this, it is possible to specify what distribution the RSRP observed at a certain reference position will have, and the reference position information DB 202 holds information on this distribution as a reference value.

  As for the reference position, for example, the area can be divided into small areas of 5 m square, and the center point can be set as the reference position. In this case, the reference position information DB 202 considers that all the observed values of the quality of the radio signal input together with the GPS positioning result included in a certain small area are observed at the center point of the small area, and the distribution described above. Is generated and stored.

  When the reference position information DB 202 calculates the distribution of the quality of the radio signal received for each base station for each reference position, the reference position information is clustered based on the distribution. For example, the reference position information DB 202 specifies, for each reference position, the base station that is the source of the radio signal that is most easily received at the reference position based on the average value, median value, or mode value of the distribution. Then, the reference positions are clustered according to the specified base station. As a result, clustering is generally performed in units of cells developed by each base station.

  The comparison target specifying unit 203 receives, from the information acquisition unit 201, the observation value of the quality of the radio signal from each of the plurality of base stations at the mobile terminal whose position is unknown, and the reference position information DB 202 generates the same. Then, a distribution of quality observation values is generated for each source base station. Note that the comparison target specifying unit 203 acquires information on a predetermined number or more of observations enough to generate a distribution. And the comparison object specific | specification part 203 calculates the correlation value between distribution about the distribution produced | generated for every some base station. The correlation value between the distributions corresponds to the approximate position of the mobile terminal. This is shown in FIG.

  FIG. 3 is a diagram showing the relationship between the position of the mobile terminal and the correlation value between distributions. FIG. 3 shows three mobile terminals (mobile terminals A to C) and radio signal quality (RSRP) distribution in each of the mobile terminals. The mobile terminal A is a terminal that is located near the base station A and is far from the base station B. The mobile terminal B is a terminal that exists at a position where the distances between the base station A and the base station B are approximately equal. The mobile terminal C is a terminal that exists at a position where the distance to the base station B is shorter than the distance to the base station A, but the difference is not large.

  At this time, in mobile terminal A, the radio signal from base station A has a high probability of being received with high power, while the radio signal from base station B has a high probability of being received with low power. Therefore, the area where the radio signal quality distribution from the base station A overlaps with the radio signal quality distribution from the base station B is extremely small, and the correlation value between the distributions is low. At this time, the average value, median value, and mode value of the RSRP in the distribution are higher in the distribution related to the radio signal from the base station A, so that the mobile terminal A is closer to the base station A. It can be estimated that the base station B is located far from the base station B.

  In the mobile terminal B, the radio signal from the base station A and the radio signal from the base station B have a high probability of being received with the same level of power. Therefore, the quality distributions of the respective radio signals almost overlap. For this reason, the correlation value between distributions becomes large. In this case, it may be estimated that the position of the mobile terminal B is a position where the radio signal from the base station A and the radio signal from the base station B are received with the same strength, that is, near the cell boundary. it can.

  In the mobile terminal C, there is a high probability that the radio signal from the base station B is received with higher power than the radio signal from the base station A, but since the distance difference is not large, the difference between the distributions is not large. Therefore, the area to be overlapped between the distributions is a value that is neither large nor small, and the correlation value is an intermediate value between the correlation value at the mobile terminal B and the correlation value at the mobile terminal A. Therefore, in this case, it can be considered that the position of the mobile terminal C is closer to the base station B than the base station A, but the distance difference is small and close to the cell edge.

  Therefore, the comparison target specifying unit 203 can specify the approximate position of the mobile terminal based on the magnitude of the correlation value, and specify the reference position to be compared in fingerprint positioning based on the approximate position. can do. For example, when the correlation value between the distributions is low and smaller than the first predetermined value, such as the distribution of the quality of the radio signal in the mobile terminal A, the comparison target specifying unit 203 has an RSRP average value, median value, A base station corresponding to a distribution having a larger mode is specified. Then, the comparison target specifying unit 203 selects a cluster corresponding to a cell deployed by the base station, and specifies a reference position belonging to the cluster as a comparison target in fingerprint positioning.

  On the other hand, when the correlation value between the distributions is large to some extent, for example, the quality distribution of the radio signal in the mobile terminal C, the position is close to the boundary between the cell deployed by the base station A and the cell deployed by the base station B. It can be determined that there is a mobile terminal. Therefore, when the correlation value between the distributions is equal to or greater than the first predetermined value, the comparison target specifying unit 203 corresponds to a cell in which two or more base stations respectively corresponding to the two or more distributions are deployed. Select two or more clusters. Then, the comparison target specifying unit 203 specifies at least a part of the reference positions belonging to the two or more clusters as a comparison target in the fingerprint positioning.

  For example, in the example of FIG. 3, the comparison target specifying unit 203 moves all reference positions included in two clusters corresponding to both the cell deployed by the base station A and the cell deployed by the base station B to the mobile unit. It is specified as a reference position to be compared in the fingerprint positioning of the terminal C. Or, in the example of FIG. 3, in the distribution of the quality of the received signal at the mobile terminal C, the RSRP distribution of the radio signal from the base station B is more average, median, Mode is high. For this reason, the comparison target specifying unit 203 includes all of the reference positions belonging to the cluster corresponding to the cell developed by the base station B and part of the reference positions belonging to the cluster corresponding to the cell developed by the base station A. You may specify as a reference position made into the comparison object by fingerprint positioning. Note that some of the reference positions belonging to the cluster corresponding to the cell deployed by the base station A are the average value, median value, and distribution of the distribution of radio signals from the base station B observed among the reference positions belonging to the cluster, Some reference positions where the mode value or the like is equal to or greater than a predetermined value may be specified.

  Further, when the correlation value between the distributions is very high, for example, the quality distribution of the radio signal in the mobile terminal B, on the boundary between the cell deployed by the base station A and the cell deployed by the base station B or It can be determined that there is a mobile terminal in the immediate vicinity. Therefore, when the correlation value between the distributions is greater than or equal to the second predetermined value that is greater than the first predetermined value, the comparison target specifying unit 203 has a correlation value that is greater than the first predetermined value and the second predetermined value. A part of the reference position specified when it is smaller than the value is specified as a reference position to be compared. That is, for example, in the positioning of the mobile terminal C, when all reference positions in the cluster corresponding to the cell deployed by the base station B are to be compared, the comparison target specifying unit 203 determines the reference position. Only a part is specified as a comparison target in the positioning of the mobile terminal B. In addition, in the positioning of the mobile terminal C, the comparison target specifying unit 203 further selects one of the reference positions in the cluster corresponding to the cell deployed by the base station A. Only the part is specified as a comparison target in the positioning of the mobile terminal B. For example, in the positioning of the mobile terminal B, the comparison target specifying unit 203 specifies only a reference position located near the boundary between two cells as a reference position to be compared in the positioning. As a result, the reference position to be compared can be greatly reduced for mobile terminals whose correlation values between distributions are very high and are known to exist near the cell boundary, and positioning accuracy is improved. While maintaining high, the calculation amount or processing time for positioning can be greatly reduced.

のように計算する。ここで、Ｐは判定に用いる基地局の個数であり、上述の無線信号の品質の分布をＰ個分だけ考慮することを示す。Ｐは１以上の整数である。Ｊは、例えば、参照位置情報ＤＢ２０２に記憶される頻度分布における、ＲＳＲＰの範囲の個数である。例えば、頻度分布において、全体で３０ｄＢｍの幅を１ｄＢｍの幅で区切って度数をカウントした場合は、Ｊ＝３０となる。また、ρ_i,p,jは、ｉ番目の参照位置についての、Ｐ個の基地局のうちのｐ番目の基地局からの無線信号の品質に関する、ｊ番目のＲＳＲＰの区間における、頻度を示す。すなわち、ρ_i,p,jは、ｉ番目の参照位置で観測されたｐ番目の基地局からの無線信号の品質の全観測値のうち、ｊ番目のＲＳＲＰの区間に含まれる観測値が生じた確率である。また、ｒ_p,jは、測位対象の移動体端末における、ｐ番目の基地局からの無線信号の品質の観測値が、ｊ番目のＲＳＲＰの区間に含まれる確率を示している。 Returning to FIG. 2, the position determination unit 204 determines the quality distribution (reference value) of the received signal for the reference position specified by the comparison target specifying unit and the quality of the radio signal observed at the positioning target mobile terminal. The position of the mobile terminal is determined by comparing with the distribution. For example, when there are I reference positions, the position determination unit 204 calculates the following d _i (1 ≦ i ≦ I) for each reference position:

Calculate as follows. Here, P is the number of base stations used for the determination, and indicates that the above-described distribution of the quality of the radio signal is taken into consideration for P pieces. P is an integer of 1 or more. J is the number of RSRP ranges in the frequency distribution stored in the reference position information DB 202, for example. For example, in the frequency distribution, when the frequency is counted by dividing the entire width of 30 dBm by the width of 1 dBm, J = 30. Also, ρ _{i, p, j} represents the frequency in the j-th RSRP section regarding the quality of the radio signal from the p-th base station among the P base stations for the i-th reference position. . That is, ρ _{i, p, j} is an observed value included in the j-th RSRP section among all the observed values of the quality of the radio signal from the p-th base station observed at the i-th reference position. Is the probability. Also, r _{p, j} indicates the probability that the observed value of the quality of the radio signal from the p-th base station in the positioning target mobile terminal is included in the j-th RSRP section.

The distribution of the quality of the radio signal from each base station generated in advance with respect to the reference position by the calculation of d _i described above, and the distribution of the quality of the radio signal from each base station observed at the positioning target mobile terminal It can be determined how much is different. And the position determination part 204 determines the reference position corresponding to the distribution with the smallest difference from the distribution observed in the mobile terminal as the position where the mobile terminal exists. That is, the position determination unit 204 determines i ₀ having the smallest value among the calculated I d _i (1 ≦ i ≦ I), and determines that the mobile terminal exists at the i ₀ th reference position. To do.

  The location information output unit 205 notifies the determination result to each base station (for example, a serving base station of the mobile terminal) via the network. The determination result may be notified to the mobile terminal. Further, the mobile terminal may notify the user by displaying the determination result on a display (not shown). For example, the mobile terminal may display an index for specifying its own position on the map application.

(Hardware configuration of position determination device)
For example, the position determination apparatus has a hardware configuration as shown in FIG. 4, and includes, for example, a CPU 401, a ROM 402, a RAM 403, an external storage device 404, and an input / output device 405. In the position determination device, for example, the CPU 401 executes a program that realizes each of the functions described above, which is recorded in any of the ROM 402, the RAM 403, and the external storage device 404. Then, the position determination device uses the input / output device 405, for example, to acquire observation value information at the mobile terminal from the network and output the position determination result to the network.

  Note that the position determination device may include dedicated hardware for executing the above-described functions, or may be executed by a computer that executes a part of the hardware and executes the program. Further, all the functions described above may be executed by a computer and a program.

(Position determination processing in the position determination device)
FIG. 5 shows the flow of the position determination process of the mobile terminal executed by the position determination apparatus. Here, it is assumed that the generation of the distribution (reference value) related to the quality of the radio signal related to the reference position and the clustering of the reference position have already been completed. As described above, the cluster corresponds to a cell deployed by each base station.

  First, the position determination device acquires information on the observed value of the quality of the radio signal in the mobile terminal via the network and the base station (S501). Here, information (cell ID) related to the base station that is the transmission source of the wireless signal is acquired together with the observation value of the quality of the wireless signal. Note that the acquisition of information on the observed value may be executed a plurality of times over a predetermined period, or information on a plurality of observed values may be acquired collectively from the mobile terminal.

  Thereafter, the position determination device generates a radio signal quality distribution for each of the radio signals from the plurality of base stations based on the acquired observation values (S502). The distribution is a frequency distribution as described above, for example, as a result of dividing the number of times a certain range of radio quality values are observed for a radio signal from a certain base station by the total number of times the radio quality is observed. can get. Here, since a distribution is generated for each of a plurality of base stations, a plurality of distributions exist.

  Thereafter, the position determination device calculates a correlation value between the distributions for the plurality of generated distributions (S503). Note that a distribution in which a value such as an average value, a median value, or a mode value is greater than or equal to a predetermined value among a plurality of distributions may be selected, and only a correlation value between the selected distributions may be calculated. This is because, for example, if a correlation value is calculated including a distribution with a very small value such as an average value, if there are two cells corresponding to a distribution with a low average value, these cells are located far from these cells. Regardless, the correlation value between the distributions of these cells may be high. As a result, the mobile terminal may not be present at the cell edge but may be determined to exist near the boundary between these cells. On the other hand, by calculating a correlation value only for a distribution in which the average value or the like is a predetermined value or more, cells that are far from the mobile terminal are not taken into account. It is possible to prevent erroneous determination.

  After calculating the correlation value between the distributions, the position determination device specifies a reference position to be compared based on the correlation value (S504). For example, when the correlation value is smaller than the first predetermined value as in the mobile terminal A of FIG. 3, the position determination device, among the distributions of the objects for which the correlation value is calculated, the average value, the median value, the mode The base station corresponding to the distribution with the maximum value is identified. Then, the position determination device specifies a cluster corresponding to a cell deployed by the base station, and specifies a reference position included in the cluster as a reference position used for determining the position of the mobile terminal. On the other hand, when the correlation value is equal to or higher than the first predetermined value, as in the mobile terminal C in FIG. 3, the position determination device specifies a plurality of base stations respectively corresponding to the distribution of the target for which the correlation value is calculated. . Then, a plurality of clusters corresponding to cells deployed by each of the plurality of base stations are identified, and at least a part of the reference positions in the plurality of clusters are compared with reference positions to be compared in the positioning of the mobile terminal As specified. Further, the position determination device, when the correlation value is greater than or equal to the second predetermined value larger than the first predetermined value, as in the mobile terminal B in FIG. A part of the plurality of reference positions specified when the value is smaller than a predetermined value of 2 is set as a reference position to be compared. By doing in this way, the reference position for comparison can be specified according to the rough position of the mobile terminal.

  Subsequently, the position determination device determines the position of the mobile terminal based on the identified reference position (S505). Specifically, the position determination device compares the distribution of the radio signal quality from each base station stored in advance with respect to the reference position and the distribution of the radio signal quality from each base station observed by the mobile terminal. Then, the reference position corresponding to the distribution having the smallest difference is determined as the position of the mobile terminal.

  As described above, in the fingerprint positioning method, after roughly estimating the position of the mobile terminal by calculating the correlation value between the distributions of the received signal quality, the reference to be compared according to the result The position can be limited. At this time, in some cases, the reference position to be compared is specified across the clusters of the reference positions. As a result, it is possible to prevent degradation in position measurement quality due to a cluster selection error by selecting a reference position to be compared across clusters in accordance with the position of the mobile terminal. In addition, since the reference position to be compared is limited, it is possible to reduce the calculation amount or processing time related to positioning.

  In the above description, the position estimation device has been described as executing all processing, but the present invention is not limited to this. For example, the mobile terminal generates a distribution of the quality of radio signals from a plurality of base stations received by itself, calculates a correlation value between the distributions, and information on the observation value of the quality of the radio signal along with the result May be notified to the position estimation device. According to this, the mobile terminal can estimate its own rough position by calculating the correlation value. Then, the mobile terminal can know the detailed position as necessary by notifying the position estimation apparatus of the correlation value information and the observation value information via the base station.

Claims (10)

The quality of radio signals from a plurality of communication devices whose positions are fixed is observed in the mobile device and the quality of radio signals from each of the plurality of communication devices is observed in advance at each of a plurality of reference positions. A determination device that compares the reference value of the stored observation value to determine the position of the mobile device,
Generating means for generating a plurality of distributions of observed values of the quality of radio signals from each of the plurality of communication devices in the mobile device;
Calculating means for calculating a correlation value between the plurality of distributions;
Based on the correlation value, a specifying unit that specifies a reference position to be compared in determination of the position of the mobile device from the plurality of reference positions;
Determination means for determining a position of the mobile device using the reference value and the observed value relating to the identified reference position;
The determination apparatus characterized by having. The plurality of reference positions belong to one of a plurality of clusters according to the position,
The specifying means specifies at least one of the plurality of clusters based on the correlation value, and uses a reference position included in the specified cluster as a comparison target in determining the position of the mobile device. Identify,
The determination apparatus according to claim 1, wherein: The cluster is determined corresponding to each communicable range of the plurality of communication devices.
The determination apparatus according to claim 2, wherein: When the correlation value between two distributions relating to an observed value of the quality of a radio signal from two communication devices of the plurality of communication devices is smaller than a first predetermined value, the specifying means A reference position included in a cluster corresponding to a communicable range of a communication device corresponding to a distribution having a large average value of the distribution is specified as a comparison target in the determination of the position of the mobile device.
The determination apparatus according to claim 3. When the correlation value between the two distributions is greater than or equal to the first predetermined value, the specifying unit is configured to include at least reference positions included in two clusters corresponding to respective communicable ranges of the two communication devices. Identifying a portion as a comparison target in determining the position of the mobile device;
The determination apparatus according to claim 4. When the correlation value between the two distributions is greater than or equal to a second predetermined value that is greater than the first predetermined value, the specifying means determines that the correlation value is greater than or equal to the first predetermined value. A part of a reference position used for determining the position of the mobile device when the value is smaller than a predetermined value of 2 is specified as a comparison target in determining the position of the mobile device;
The determination apparatus according to claim 5. The mobile device further includes acquisition means for acquiring information identifying each of the plurality of communication devices and the observed value in the mobile device regarding the quality of a radio signal from each of the plurality of communication devices. ,
The determination apparatus according to claim 1, wherein:   A network node comprising the determination device according to claim 1. At each of the plurality of reference positions and the observed value of the quality of the radio signal from the plurality of communication devices whose positions in the mobile device are fixed, the quality of the radio signal from each of the plurality of communication devices is observed in advance. A determination method for a position in a determination apparatus that compares the reference value of the stored observation value and determines the position of the mobile device,
A generating step of generating a plurality of distributions of observation values in the mobile device of the quality of radio signals from each of the plurality of communication devices;
A calculating step of calculating a correlation value between the plurality of distributions;
A specifying step of specifying a reference position to be compared in determination of the position of the mobile device from the plurality of reference positions based on the correlation value;
A determination step of determining a position of the mobile device using the reference value and the observed value related to the identified reference position;
The determination method characterized by having. At each of the plurality of reference positions and the observed value of the quality of the radio signal from the plurality of communication devices whose positions in the mobile device are fixed, the quality of the radio signal from each of the plurality of communication devices is observed in advance. A computer provided in a determination device that compares the reference value of the stored observation value and determines the position of the mobile device,
Generating a plurality of distributions for the observed values in the mobile device of the quality of the radio signal from each of the plurality of communication devices;
A calculation step of calculating a correlation value between the plurality of distributions;
Based on the correlation value, a specifying step for specifying a reference position to be compared in determination of the position of the mobile device from the plurality of reference positions;
A determination step of determining the position of the mobile device using the reference value and the observed value relating to the identified reference position;
A program for running

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