WO2000050919A2 - Utilisation d'une table derivee de donnees concernant l'intensite de signal pour localiser et pister un utilisateur dans un reseau sans fil - Google Patents

Utilisation d'une table derivee de donnees concernant l'intensite de signal pour localiser et pister un utilisateur dans un reseau sans fil Download PDF

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Publication number
WO2000050919A2
WO2000050919A2 PCT/US2000/004902 US0004902W WO0050919A2 WO 2000050919 A2 WO2000050919 A2 WO 2000050919A2 US 0004902 W US0004902 W US 0004902W WO 0050919 A2 WO0050919 A2 WO 0050919A2
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WIPO (PCT)
Prior art keywords
wireless signal
signal strength
base station
mobile unit
known location
Prior art date
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PCT/US2000/004902
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English (en)
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WO2000050919A3 (fr
Inventor
Paramvir Bahl
Venkata N. Padmanabhan
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Microsoft Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Microsoft Corporation filed Critical Microsoft Corporation
Priority to AU35031/00A priority Critical patent/AU3503100A/en
Publication of WO2000050919A2 publication Critical patent/WO2000050919A2/fr
Publication of WO2000050919A3 publication Critical patent/WO2000050919A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0252—Radio frequency fingerprinting
    • G01S5/02521—Radio frequency fingerprinting using a radio-map
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
    • G01S11/02—Systems for determining distance or velocity not using reflection or reradiation using radio waves
    • G01S11/06—Systems for determining distance or velocity not using reflection or reradiation using radio waves using intensity measurements

Definitions

  • This invention relates generally to determining the location of an object and tracking the object and, more particularly, relates to locating and tracking a user of a wireless network.
  • GPS Global Positioning System
  • the GPS system relies on the timing of signals from GPS satellites received by individual GPS units on the ground. Thus, an unobstructed view to the satellites is necessary to receive the signal. In an indoor environment, such an unobstructed view is,
  • tags placed on the items that are to be tracked.
  • the tags can be either active or passive.
  • An active tag contains power circuitry, which can communicate with base stations.
  • a passive tag contains no internal power, rather it is charged either inductively or electromagnetically as it passes within the range of a base station. Using this derived power, the passive tag communicates with the station.
  • the base stations are physically linked together through a wired or wireless network. Each tag transmits a code uniquely identifying itself. Thus, the location of the tag is determined to be in the vicinity of the base station with which the tag last communicated.
  • tag-based tracking and location systems while being useful in an in-building environment, require a significant installation of specialized base stations.
  • a tag-based system can only determine the location of the tags as being "near" a particular base station, consequently, to achieve a sufficiently high resolution a large number of base stations must be installed.
  • Obtrusive tags have to be placed on every item that is to be
  • the present invention is generally directed to a system for locating and tracking a user in a building without a specialized infrastructure and with the ability to track without a line-of-sight between the user and a base station.
  • the present invention is also generally directed to a system for locating and tracking a user in a building using the existing Radio-Frequency (RF) Wireless Local Area Network (WLAN) infrastructure.
  • RF Radio-Frequency
  • WLAN Wireless Local Area Network
  • a Wireless Local Area Network consists of base stations connected to a wired network, and mobile devices which are "connected" to the WLAN through wireless communication with the base stations.
  • the present invention uses the signal sensing ability of both the base station and the mobile device to determine the location of the mobile device, and thus the location of the user of the mobile device.
  • the strength of the received signal from several base stations is measured by the mobile device.
  • the mobile device compares the signal strength from each of the base stations to a pre-computed table containing the base stations' signal strength at various known locations of the mobile device. From this comparison, the mobile device determines its location.
  • the signal strength from the mobile device can be measured at a number of
  • This signal strength is then compared by a central computer to a pre- computed table containing the mobile computer's signal strength at the base stations for various known locations of the mobile computer. From this table, the central computer
  • Figure 1 is a block diagram generally illustrating an exemplary computer system on which the present invention resides;
  • Figure 2 is a diagram generally illustrating a wireless network according to the present invention
  • Figure 3 is a diagram generally illustrating a wireless network on one floor of an
  • Figure 4 is a diagram generally illustrating the locations of empirical determinations of signal strength according to the present invention.
  • Figure 5 is a diagram generally illustrating the operation of a line-clipping
  • Figure 6 is a flow chart generally illustrating the operation of a mathematical derivation of a signal strength table according to the present invention.
  • an exemplary system for implementing the invention includes a general purpose computing device in the form of a conventional mobile personal computer 20, including a processing unit 21, a system memory 22, and a system bus 23 that couples various system components including the system memory to the
  • the system bus 23 may be any of several types of bus structures
  • the system memory includes read only memory (ROM)
  • the mobile personal computer 20 further includes a hard disk drive 27 for reading from and writing to a hard disk 60, a magnetic disk drive 28 for reading from or writing to a removable magnetic disk 29, and an optical disk drive 30 for reading from or writing to a removable optical disk 31 such as a CD ROM or other optical media.
  • a hard disk drive 27 for reading from and writing to a hard disk 60
  • a magnetic disk drive 28 for reading from or writing to a removable magnetic disk 29
  • an optical disk drive 30 for reading from or writing to a removable optical disk 31 such as a CD ROM or other optical media.
  • the hard disk drive 27, magnetic disk drive 28, and optical disk drive 30 are connected to the system bus 23 by a hard disk drive interface 32, a magnetic disk drive interface 33, and an optical disk drive interface 34, respectively.
  • the drives and their associated computer-readable media provide nonvolatile storage of computer readable instructions, data structures, program modules and other data for the mobile personal computer 20.
  • a hard disk 60, a removable magnetic disk 29, and a removable optical disk 31 it will be appreciated by those skilled in the art that other types of computer readable media which can store data that is accessible by a computer, such as magnetic cassettes, flash memory cards, digital video disks, Bernoulli cartridges, random access memories, read only memories, and the like may also be used in the exemplary operating environment.
  • a number of program modules may be stored on the hard disk 60, magnetic disk
  • ROM 24 or RAM 25 including an operating system 35, one or more application programs 36, other program modules 37, and program data 38.
  • a user may enter commands and information into the mobile personal computer 20 through input
  • keyboard 40 such as a keyboard 40 and a pointing device 42.
  • Other input devices may include a microphone, joystick, game pad, satellite dish, scanner, or the like.
  • serial port interface 46 that is coupled to the system bus, but may be connected by other interfaces, such as a parallel port, game port or a universal serial bus (USB).
  • a monitor 47 or other type of display device is also connected to the system bus 23 via an interface, such as a video adapter 48.
  • personal computers typically include other peripheral output devices, not shown, such as speakers and printers.
  • the mobile personal computer 20 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 49.
  • the remote computer 49 may be another personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the mobile personal computer 20, although only a memory storage device 50 has been illustrated in Figure 1.
  • the logical connections depicted in Figure 1 include a Wireless Local Area Network (WLAN) 51 and a wide area network (WAN) 52.
  • WLAN Wireless Local Area Network
  • WAN wide area network
  • the wireless interface 53 transmits wireless packets to a base station 61.
  • the base station 61 The base station
  • the personal computer 49 can then retransmit the packets, either through a wired or wireless network to the remote computer 49.
  • the personal computer 49 When used in a WAN networking environment, the personal
  • the computer 20 typically includes a modem 54 or other means for establishing communications over the WAN 52.
  • the modem 54 which may be internal or external, is
  • program modules depicted relative to the mobile personal computer 20, or portions thereof, may be stored in the remote memory storage device. It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used.
  • base stations 72, 74, and 76 are the same as base station 61 in Figure 1, however, for clarity, each base station has been separately numbered so that each can be referred to individually.
  • mobile personal computers 78, 80, and 82 are all of the same
  • the mobile computer 78 can communicate, via wireless communication, with either base
  • the mobile computer 78 can select the base station which provides the highest signal strength, measured by the signal- to-noise ratio (SNR).
  • SNR signal- to-noise ratio
  • the base stations 72, 74, and 76 can be connected by connection 70, which can be either a wired or wireless network. Therefore, to link two computers together, the WLAN passes messages through the base stations.
  • mobile computer 78 can contact either base station 72 or base station 74. These base stations will then relay the message, through connection 70, to base station 76, which is the base station with which mobile computer 80 may currently be communicating. Base station 76 will then transmit the message to mobile computer 80, completing the wireless connection between mobile computers 78 and 80.
  • the WLAN defines a mechanism by which communication between the mobile computers and the WLAN is transferred from one base station to another.
  • the mobile computers 78, 80, and 82 monitor the signal strength of the base stations 72, 74, and 76. In some embodiments the mobile computers continuously monitor the signal strength, and in others, the mobile computers only monitor the signal strength when the SNR of the base station with which the mobile computer is currently communicating falls below an acceptable level.
  • the base stations 72, 74, and 76 monitor the signal strength from the mobile computers 78, 80, and 82. A more detailed description of how the mobile computers are
  • the present invention uses this monitoring of signal strength by both the base stations and the mobile computers, to locate and track a mobile computer and its user.
  • An exemplary building layout is shown in Figure 3.
  • the building includes hallway 90; offices 92, 93, 94, 95, 96, 97, and 98; and conference rooms 100 and 102.
  • Base stations 72, 74, and 76 have been placed at various locations in the building.
  • the mobile personal computers 78, 80, and 82 are also in the building, although they can move freely throughout the building.
  • the mobile personal computer 78 can monitor the strength of the signal from base stations 72, 74, and 76.
  • the signals of a WLAN are attenuated as they propagate and as they pass through walls. Therefore, as monitored by mobile computer 78, the signal from base station 72 is stronger than the signals from base stations 74 and 76. This is because the signals from base stations 72 and 74 must travel a greater distance and must pass through more walls.
  • the signal strength from base stations 72, 74, and 76 will vary as the mobile computer 78 is moved around the building. For example, if the user of mobile computer
  • FIG 4 a method for creating the location versus signal strength table is shown.
  • diamonds with letters in them indicate locations where empirical measurements of the signal strength of the base stations 72, 74, and 76 have been taken. These measurements can then be compiled into a table, such as Table 1, shown below.
  • location B has a higher SNR for base station 72 than location A because, while both are approximately equidistant from base station 72, location A is separated from the base station by the wall of office 92.
  • the observation that distance and intervening walls decrease the signal strength, and thus decrease the SNR, is true for the rest of the entries in the table as well.
  • the strength of the radio frequency signals measured by the base station 76 or the mobile computer 20 can vary as a function of the orientation of the mobile computer 20 when performing the measurements. More particularly, the orientation of the computer is related to the position of the user, and it is the user's body that can create a significant difference in the detected signal strength. It is therefore necessary that the table used in determining the location of the mobile computer take this effect into account and be able to determine the location regardless of the orientation of the user with respect to the mobile computer.
  • One method for taking this effect into account is to consider multiple orientations of the user's body to minimize the effects of signal attenuation due to the user's body.
  • the present invention also contemplates multiple measurements at each location to remove the effect of the random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference, that can affect signal quality. Because these events are often short lived, multiple random variables, such as air currents and radio interference
  • the mobile computer 20 can determine its location by finding the row of the table which most closely corresponds to the signal strengths detected by the mobile computer. For example, mobile computer 78 might detect a SNR of 38 dB from base station 72, 23 dB from base station 74, and 24 dB from base station 76. By comparing these values to Table 1, the mobile computer 78 determines that it is located at physical position C. This determination can be done in signal space.
  • the signal space is an multi-dimensional space where the number of dimensions is equivalent to the number of base stations' signals which the mobile computer uses to determine its location. In Table 1 above, three base stations' signal strengths are determined at each physical location, so the signal space is a three-dimensional space. As will be known by those skilled in the art, unlike physical space, the signal space is not limited to three dimensions.
  • Each set of three measured signal strengths from the three base stations can define a point in the signal space.
  • the Euclidean distance between the point defined by the measured signal strengths and the points defined by the empirically derived signal strengths in Table 1 can be calculated. As is known by those
  • the Euclidean distance is the square root of the sum, over all the dimensions, of the difference between two points in each dimension, squared.
  • the physical location of the mobile computer 20 is determined to be the same as the location whose corresponding empirically derived signal strengths in the table are the closest (as defined above) to the measured signal strengths.
  • the location of mobile computer 78 would be determined to be location C. This is because the Euclidean distance in signal space between (38,23,24), which are the measured values, and
  • the stored values at point C which were determined empirically during system set-up, is less than the Euclidean distance between (38,23,24) and any other point in the table.
  • the mobile computer 20 therefore concludes that it is located at location C.
  • the location of a mobile computer 20 can thus be determined through sensing the signal strength from each of a number of base stations.
  • the Euclidean distance is just one possible distance metric. Other distance metrics such as sum of absolute value differences, or weighted Euclidean are also possible.
  • the present invention also contemplates finding several rows of the table, each of which contains values similar to those observed. Such a multiple nearest neighbor approach,
  • a variation of the multiple nearest neighbor approach using weighting is also contemplated by the present invention. If one set of signal strength values are very similar to the values detected by the mobile computer 20, it may be that the position corresponding to those values is more accurate than any other position at which an empirical measurement was taken. That does not mean, however, that the multiple nearest neighbor approach cannot improve the accuracy of that position determination. However, because there exists a position which appears to be near the actual position of the mobile computer, only minor changes to that position should be caused as a result of the multiple nearest neighbor approach. In such a case, a weighted multiple nearest neighbor approach may be appropriate. A weighted multiple nearest neighbor approach multiplies the coordinates of each "neighbor" location by a weighting factor prior to averaging them. If a position appears to be a particularly good match, then the
  • the present invention also contemplates locating a mobile device by measuring
  • a computer 84 can also be connected to the base stations 72, 74, and 76, through the network 70.
  • Computer 84 can monitor the signal strength from a particular mobile computer 20 as received by the base stations near that mobile computer. Because it is connected to all of the base stations, the computer 84 can also generate the table which relates the position of the mobile computer 20 to the strength of the signal from the mobile computer as received by each of the base stations.
  • empirical data can be gathered by sampling the signal strength from the mobile computer, as it is moved throughout the building.
  • the table generated by computer 84 as a result of the sampling will contain the signal strength of the signal from the mobile computer as detected at each base station, instead of the signal strength of the signal from each base station as detected at the mobile computer.
  • the computer 84 can collect the signal strength information as received by each base station and create a table such as Table 2 below.
  • the tables are similar with respect to the relationship between the signal strengths in any one row. Even though the signal strength measured at the mobile computer 20 and the base station 76 are similar in value, there is no requirement that they be so. The two signals travel the same path and encounter the same obstacles which degrade the signal. The only difference can be the power of the transmitting devices themselves: the base station, since it does not need to conserve power, may be tr.ansmitting at a higher power than the wireless network interface 53 on the mobile computer 20.
  • the Federal Communications Commission (FCC) allows wireless networks to use up to 1 Watt of transmitting power, which can be easily met by the base station.
  • the wireless network interface 53 typically transmits in the 50-100 mW range so as to conserve the battery power of the mobile computer 20.
  • the signal from base station 72 is stronger than the signals from base stations 74 and 76 because of the distance and the obstacles between location A and base stations 74 and 76. This is the same reason that in Table 2, at location A, the signal from the mobile computer at location A is stronger when detected by base station 72 than when detected by base stations 74 and 76. Because the mobile computer does not transmit its signals with as much power, the SNR is lower in Table 2 than in Table 1.
  • multiple measurements taken at several different orientations of the mobile computer 20 can be used to eliminate the effect of the user's body on the signal strength when creating a table such as Table 2. Additionally, as described above, taking multiple measurements at each location can improve the accuracy of the values in the table, as it minimizes the effects of random interference and noise.
  • the multiple nearest neighbor method described in detail above can also be used with the data in Table 2.
  • the computer 84 can determine that the strength of the signal from mobile computer 78, as shown in Figure 4, is 28 dB as detected by base station 72, 13 dB as detected by base station 74, and 14 dB as detected by base station 76. Comparing these values to Table 3, we find locations A, B, and C as the nearest "neighbors" to the values obtained. The nearest neighbors are then spatially averaged to
  • An alternative method to empirically deriving Tables 1 or 2 above, contemplated by the present invention, requires mathematically estimating the attenuation in the signal as due to the distance between the transmitter and the receiver, and the intervening walls.
  • the transmissions in a wireless network conform to general radio propagation theories. Most notably the signal strength of the transmissions becomes weaker as the distance from the transmitting source increases, and the signal strength of the transmissions decreases when the signals must pass through walls.
  • Research into the field of electromagnetic waves has yielded a number of useful mathematical formulas. For example, it is known that signal strength decreases with distance. It is also known that walls attenuate signals by a determinable factor, known as the Wall Attenuation Factor (WAF).
  • WAF Wall Attenuation Factor
  • the WAF is dependent on the thickness of the wall, and the materials used in the construction of the wall.
  • the WAF can be determined empirically by placing a receiver on one side of a wall and a transmitter on the other, and detecting the attenuation of the signal through the wall.
  • One method for determining a WAF can be found in the article entitled "914 MHz Path Loss Prediction Models for Indoor Wireless Communications in Multifloored Buildings" by Scott Y. Seidel and Theorodre S. Rappaport, which appeared in LEEE Transactions On Antennas and
  • the signal strength at a particular location can, therefore, be defined as the signal
  • the first term is the signal strength at a reference distance d o .
  • the reference distance can be any distance d o .
  • the second term in the equation provides the attenuation in the signal strength due to the distance between the point at which the signal strength is sought to be calculated, and the reference point at which the signal strength is known.
  • the variable n is the path loss component which indicates the rate at which the signal strength decreases with distance. The second term is subtracted from the first term, and thus, reduces the reference signal strength if the desired point is further from the transmitter than the reference point.
  • the third term in the equation quantifies the attenuation due to the number of walls the signal must pass through.
  • nW represents the number of walls and the WAF can be determined empirically, as described above.
  • the product of the two yields the attenuation due to all of the walls.
  • the WAF is a negative number, resulting in a reduction to the calculated signal strength.
  • the signal becomes so weak that further degradation is not mathematically significant.
  • This practical limit is C walls, where C can be selected by the user to satisfy that user's accuracy requirements. After C number of walls, therefore, the attenuation factor can
  • the number of walls between a signal source and the location for which the signal strength is to be calculated can be determined by automated means. For example, in one
  • the building is divided into non-overlapping but connected
  • Line clipping is the deletion of a part of a line segment which lies outside a clip area. Once the line clipping is performed, the remaining line segment lies completely within a clip area.
  • the algorithm divides the region outside of the clipping area into areas with "outcodes". Each digit of the binary outcode represents whether the particular region lies above, below, or to the left or right of a clipping area. As is shown in Figure 5, a four binary digit outcode can be used.
  • the first digit indicates whether the region is above the clipping region 104.
  • regions 118, 120, and 106 are all above region 104, as indicated by the dashed lines, and those regions all have a binary 1 as the value of the first digit.
  • the second digit indicates whether the region is below the clipping region 104.
  • regions 114, 112, and 110 all have a binary 1 as the value of the second digit since they are below the clipping region 104.
  • Regions 108 and 116 are adjacent to the clipping region and therefore both the first and second binary digits are 0, since adjacent regions are neither above nor below the clipping region.
  • the third binary digit indicates whether the region is to the right of the clipping region 104
  • the fourth binary digit indicates whether the region is to the left of the clipping
  • the clipping region 104 itself has an outcode of 0000 because, by definition, it is nether above, nor below, and neither to the left nor to the right of itself. Once this subdivision occurs, all lines through the clipping region, such as lines
  • outcodes A key feature of the outcodes is that the binary digits which have a value of 1 correspond to boundaries between the regions, which are crossed.
  • line 122 has two endpoints: one in region 0000 and another in region 1001.
  • the significance of outcode 1001 is that the line must intersect the top and left boundaries because the first digit indicates it is above the clipping region and the last digit indicates it is to the left of the clipping region, as described above. Whenever a point on the line changes its outcode value, by definition the line has crossed a boundary. It is possible that this line intersects a number of rectangular regions.
  • step 140 the floor schematic is entered into a computer as an input to the Cohen-Sutherland Line Clipping Algorithm. Similarly, at step 142 the locations of the base stations are entered, and at step 144 the locations at which the signal strength is to be calculated are entered.
  • step 146 will then determine, as described above, the number of walls between each of the base stations and the locations at which the signal strength is to be calculated. This number is then used in the signal strength equation, given above, at step 148.
  • the WAF empirically derived as described above, is entered at step 150.
  • the limiting factor C is selected by the user.
  • variable n the rate at which signal strength decreases with distance.
  • step 158 The signal strength equation given above can then, at step 148, calculate the signal strength at each of the locations entered in step 144.
  • the output of the signal strength equation is entered into a table, such as Table 1 or Table 2, above, at step 160.
  • the mathematical estimation can be used to derive both a table containing the values of the signal strength from various base stations as detected by a mobile computer 20 and the values of the signal strength from a mobile computer 20 as detected by various base stations.
  • the variables in the signal strength equation would be different depending on which method was used. For example, to calculate the signal strength from a base station, as detected by a mobile computer at a particular location, the reference distance should be set close to the base station, or even at one meter from the base station, as described above, and the term n would be the rate at which the signal strength of the base station decreased with distance.
  • the reference distance should be set close to the mobile computer, such as one meter away, and the term n would be the rate at which the signal strength of the mobile computer 20 decreased with distance.
  • the present invention also contemplates providing for environmental factors by
  • the base stations are all located at known locations, as shown in Figures 3 and 4. One base station could send out a signal to be received by the other base stations, in the same way that the base stations would receive a
  • base station 72 For example, with reference to Figure 3, base station 72
  • the computer 84 could receive the signal of base station 72, as detected by base stations 74 and 76, and determine the location of base station 72. This would be done in the same manner that computer 84 would determine the location of a mobile computer 20 from its signal strength as detected at the base stations, as described above.
  • the computer 84 can then compare the calculated location to the known location of base station 72. If there is a difference between the two, the inputs to the variables in the signal strength equation, given above for estimating the signal strength at a particular location, can be varied. For example, the n value, or the WAF, could be changed, and a new table recalculated. This new table would then be used by computer 84 to calculate again the position of base station 72. The computer 84 could then again compare the new calculated location of base station 72 to the known location and determine the difference. The above iteration can be performed multiple times.
  • the computer 84 could determine which values of the variables in the signal strength equation yielded the most accurate results, and then use those values to generate the table, which would, in turn, be used to calculate the position of the mobile computers.
  • the values of the variables could also be passed to the mobile computer 20 along with a map of the building, so that it can generate a table within itself, and determine its location based on the strength of the
  • the system can be programmed to profile and tune itself, as described above, multiple times.
  • An alternative environmental profiling mechanism can be implemented by empirically deriving more than once the table relating the position of the mobile computer to the signal strength.
  • a table relating the position of the mobile computer to the signal strength such as Tables 1 or 3, can be derived empirically. Such empirical derivations can be performed numerous times, under different environmental conditions, and at different times of the day. Environmental conditions can be impacted by the temperature, the number of people in the building, the amount of human traffic in the building, and whether it is day or night.
  • the base stations could test the system by attempting to use the tables to determine the location of a given base station and then comparing the calculated location to the true location. The table that results in the greatest accuracy would then be used. In this way, the system could avoid the complexity of calculating the signal strength.
  • the system could be programmed to environmentally profile itself periodically.
  • the present invention can also be implemented by a dedicated system providing base stations and receiver/transmitters on the mobile computer. Similarly, the
  • present invention can operate on any wireless mechanism, which does not require a line-
  • RF radio frequency
  • the present invention is equally applicable to a wireless system that interconnects other mobile units, in addition to mobile personal computer 20, such as cordless phones, CB radios, two-way radios, or the

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  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

Cette invention concerne un procédé pour localiser un utilisateur dans un réseau sans fil. Un ordinateur mobile cherchant à déterminer son emplacement à l'intérieur d'un bâtiment détecte l'intensité du signal d'une ou plusieurs stations de base sans fil placées dans tout le bâtiment, à des emplacements connus. Cet ordinateur mobile utilise cette intensité de signal mesurée pour déterminer son emplacement en recherchant dans une table « intensité de signal-emplacement ». Une table des emplacements connus à l'intérieur du bâtiment et de l'intensité de signal de la station de base à ces emplacements est recherchée pour trouver l'intensité de signal enregistrée la plus proche de l'intensité de signal détectée. L'emplacement correspondant à l'intensité de signal enregistrée la plus proche est déterminé comme étant l'actuel emplacement de l'ordinateur mobile. Selon une variante, plusieurs intensités de signal de la table peuvent être utilisées et une moyenne spatiale des emplacements correspondants peut être établie, de façon à déterminer l'emplacement de l'ordinateur mobile. La table peut être dérivée empiriquement, en plaçant un ordinateur mobile aux emplacements connus et en détectant l'intensité de signal des stations de base sans fil à ces emplacements, ou peut être dérivée mathématiquement, en considérant une intensité de signal de référence, la distance entre le point de référence et l'emplacement connu et le nombre de murs entre le point de référence et l'emplacement connu. Selon une autre variante, les stations de base peuvent détecter l'intensité de signal de l'ordinateur mobile. Dans ce cas, la table établit une relation entre une position connue de l'ordinateur mobile et l'intensité de signal de l'ordinateur mobile à l'emplacement détecté par la ou les stations de base.
PCT/US2000/004902 1999-02-25 2000-02-25 Utilisation d'une table derivee de donnees concernant l'intensite de signal pour localiser et pister un utilisateur dans un reseau sans fil WO2000050919A2 (fr)

Priority Applications (1)

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AU35031/00A AU3503100A (en) 1999-02-25 2000-02-25 Using a derived table of signal strength data to locate and track a user in a wireless network

Applications Claiming Priority (2)

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US12161299P 1999-02-25 1999-02-25
US60/121,612 1999-02-25

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WO2000050919A2 true WO2000050919A2 (fr) 2000-08-31
WO2000050919A3 WO2000050919A3 (fr) 2000-12-07

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PCT/US2000/004902 WO2000050919A2 (fr) 1999-02-25 2000-02-25 Utilisation d'une table derivee de donnees concernant l'intensite de signal pour localiser et pister un utilisateur dans un reseau sans fil
PCT/US2000/004773 WO2000050918A2 (fr) 1999-02-25 2000-02-25 Procede de localisation et de recherche d'un utilisateur dans un reseau radio a l'aide de donnees de profils d'environnement

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WO2014137868A1 (fr) * 2013-03-06 2014-09-12 Qualcomm Incorporated Données d'assistance adaptative pour un service et une efficacité à plusieurs niveaux lors d'un positionnement en intérieur
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AU3706500A (en) 2000-09-14
WO2000050918A3 (fr) 2001-05-31
WO2000050919A3 (fr) 2000-12-07
WO2000050918A2 (fr) 2000-08-31
AU3503100A (en) 2000-09-14

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