Method and system for positioning mobile computer

[Technical field]

【0001】

The present invention relates generally to locating using radio signals, and more specifically to locating mobile computers using radio signals.

[Background technology]

【0002】

Many organizations today manage their own internal computer networks. Wireless communication is becoming an important part of such networks. The advantage of wireless communication is that it allows the user to move, for example, from room to room, and from room to room, while maintaining connectivity to the organization's network. It means that it will be possible to carry from building to building. Mobile user computers typically communicate with the network through a set of wireless access points distributed throughout an organization's facilities.

[Disclosure of ideas]

[Problems to be Solved by the Invention]

【0003】

There are many applications that are effective in locating mobile users. For example, if an employee of a large company needs to print out a document, but the employee himself is not familiar with the building, he will have to walk around to find the nearest printer, and once the printer. Once found, you will have to determine the printer's network name and select it on the screen. Employees can easily send documents to the "closest printer", have a network to identify the closest printer, automatically send documents to it, and even to the printer It would be very useful if we could give instructions to the user on how to get there.

[Means for solving problems]

【0004】

The present invention generally describes a method and system for locating a mobile computer in which the mobile computer establishes a wireless communication session with a wireless access point in a computer network. According to various embodiments of the invention, the location of each radio access point is known and available either from a database on the network or from the access point itself. The strength of the radio signal passing between the mobile computer and multiple wireless access points on the network, including the access point with which the mobile computer has established a session, is measured at multiple time intervals. The measurement may be performed on the mobile computer itself or on a wireless access point. The measured intensity values are then weighted according to factors such as whether the mobile computer has already established a communication session with the access point from which the sample was obtained, and how old the sample is. For each position, sum the weighted intensity values obtained for the access point at that position. The position with the highest total value is considered to be the position of the mobile computer.

【0005】

In various embodiments of the present invention, the location of each wireless access point and the resulting location of the mobile computer may be represented in various ways. For example, the location of a mobile computer may be calculated and represented as a physical location associated with a reference point, or as part of a grid system established by a system administrator.

【0006】

Additional features and advantages of the present invention will become apparent from the following detailed description of the illustrated embodiments, which proceed with reference to the accompanying figures.

[Best mode for carrying out the invention]

【0007】

Although the claims detail the features of the invention, the invention, along with its purpose and advantages, can best be understood from the following detailed description in connection with the accompanying drawings.

【0008】

The present invention generally determines the position of a mobile computer, either by the client computer itself or by a wireless access point, where the signal strength passing between the mobile computer and multiple wireless access points in a computer network is measured. Oriented to methods and systems for. According to various embodiments of the present invention, the measurements obtained for signal strength are classified according to the location of the wireless access point. The measured signal strength value is then weighted according to factors such as whether the mobile computer has established a connection with the wireless access point or how old the measurement is.

【0009】

Next, a description of the computer and network environment in which the present invention can be implemented is provided prior to proceeding with the description of various embodiments of the invention. Although not required, the present invention may be implemented by a program module executed by a computer. In general, program modules include routines, objects, components, data structures, and those that perform specific tasks or implement specific abstract data types. The term "program" as used herein can mean a single program module, or multiple program modules that are emphasized and operating. The present invention can be applied to various types of computers, including personal computers (PCs), handheld devices, multiprocessor systems, microprocessor-based programmable home appliances, network PCs, minicomputers, mainframe computers, and the like. It may be carried out at. The term "mobile" used herein may apply to any of these types of computers.

【0010】

Moreover, the term "client computer" does not mean that it is restricted to computers in a static client-server relationship. Those skilled in the art recognize that computers can act as both clients and servers at various times, and can be more useful as both at the same time in so-called "Peer" networks. The present invention may also be used in a distributed computing environment where tasks are performed by remote processing devices linked through a communication network. In a distributed computing environment, modules may be installed on both local and remote memory storage devices.

【0011】

An example of a networked environment that can be used in the present invention will then be described with respect to FIG. Examples of networks include several computers 100 communicating with each other over network 102, depicted as clouds. The network 102 may include many well-known components such as routers, gateways, hubs, etc., and may also allow the computer 100 to communicate via wired and / or wireless media.

【0012】

With reference to FIG. 2, an example of a basic configuration for a computer in which at least a portion of the invention described herein can be performed is shown. In its most basic configuration, the computer 100 generally includes at least one processor 112 and memory 114. Depending on the exact placement and type of computer 100, memory 114 can be volatile (like RAM), non-volatile (like ROM or flash memory), or a combination of the two. good. This most basic configuration is illustrated in FIG. 2 by the dashed line 106. Moreover, the computer also has additional features / functionality. For example, computer 100 may also include additional storage devices (removable and / or non-removable), not limited to magnetic or optical discs, or tapes. Computer storage media are volatile and non-volatile, removable and non-volatile, performed in any way, or in science and technology, for the storage of information such as computer-readable instructions, data structures, program modules, or other data. Includes removable media. Computer storage media are not limited to, but are limited to RAM, ROM, ERPROM, flash memory, or other memory science and technology, CD-ROMs, digital versatile disks (DVDs), or other optical storage. Includes devices, magnetic cassettes, magnetic tapes, magnetic disk storage devices, or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible by the computer 100. Any such computer storage media can be part of the computer 100.

【0013】

The computer 100 can also include a communication connection that allows the device to communicate with other devices. Communication connection is an example of a communication medium. Communication media typically embodies computer-readable instructions, data structures, program modules or other data in modulated data signals such as carrier waves, or other transport mechanisms, and includes any information delivery media. .. As an example, and without limitation, communication media includes wired media such as wired networks, or direct wired connections, and wireless media such as acoustic, radio frequency, infrared and other wireless media. Including. The term computer-readable instructions, as used herein, includes both storage and communication media.

【0014】

The computer 100 can also have input devices such as keyboards, mice, pens, voice input devices, touch input devices and the like. Output devices such as displays 118, speakers, printers and the like may also be included. All of these devices are technically well known and need not be discussed in detail here.

【0015】

An example of a scenario in which the present invention can be carried out will be described below with reference to FIG. And in FIG. 3, the corporate network 150 is communicatively linked to the Internet 152 and also includes a first client computer 166 and wireless access points 154, 156, 158, 160, and 162. The first client computer is used by the first user 168. Wireless access points 154, 156, 158, 160, and 162, AP₁, AP₂, AP₃, AP₄, And AP_n, Is expressed. AP₄And AP_nAs indicated by the dashed line between and, there can be any number of wireless access points in the corporate network 150. The second client computer 164 is recognized by the corporate network 150, but is not constantly communicating with the corporate network 150. The second client computer 164 is mobile and is with the second user 170 wherever the second user 170 goes. The second client computer will often be referred to as "mobile client computer 164" below. To establish communication with the corporate network 150, the mobile client computer 164 establishes a wireless session with one of the wireless access points. Radio sessions can be established for any type of radio medium, including radio frequency (RF), or ultrasound. The embodiments described herein are known to be suitable for IEEE 802.11b RF communication.

【0016】

Each wireless access point is installed at a location associated with a location identifier. There are many ways to implement that location identifier, and the way to implement it depends on how the location is shown in the network. For example, if the building where the network is installed is divided into 10x10 grids, its location identifier for the wireless access point should then be provided in the grid square where the wireless access point is in columns 5 and 3. It may be something like "0503" indicating. According to embodiments of the present invention, the location identifier is a string, including its building number, floor number, and surface of the building (depending on the compass direction) in which the wireless access point is installed. For example, the location identifier "Building 2, Floor 3 NW" means that the access point is located on the 3rd floor of Building 2 in the northwest corner. In another embodiment, the position identifier is a schema composed of a plurality of character strings, as in the following example. Country: Canada: BC City: Victoria Street: Broad Street Number: 11102 Floors: 2 Rooms: 115 Two or more wireless access points depend on how their location is indicated to their network. They may have the same position identifier indicating that they are considered to be in the same position.

【0017】

The location identifier for each wireless access point can be maintained at various locations. For example, database 172 on corporate network 150 may contain entries for each wireless access point in corporate network 150. The entry identifies the wireless access point (eg by IP address, MAC address and / or machine name) and its location identifier. By customizing the content and format of the location identifiers in database 172, system administrators can set the granularity of the data that indicates the location of wireless access points on network 150. Therefore, the location of each wireless access point can be expressed in general terms such as on which floor of the building it was located, or more specific, such as which 2 meter grid square it occupies. Can be expressed in terms. In this way, the chunks of data that locate the mobile computer can also be customized. In some embodiments of the invention, the database 172 is populated with MICROSOFT ACTIVE. Implement as DIRECTORY. Each wireless access point may also know its own location identifier. For example, the mobile client computer 164 may obtain location identifiers for one or more of the wireless access points, made by requesting them from the corporate network 150 itself. Alternatively, wireless access points may constantly broadcast their own location identifiers, thus eliminating the need for mobile client 164 to request that information.

【0018】

Various embodiments of the present invention allow the location of the mobile client computer 164 to be determined, whereby, for example, the first user 168 can refer to the location of the second user 170 to the corporate network (first client computer). It will be possible to ask (via 166) and respond to receive the location of the mobile client computer 164.

【0019】

An example of a procedure that can be used to determine the location of a client computer in an embodiment of the invention will then be described with respect to the flowchart of FIG. 4 and the scenario illustrated in FIG. In this example, the AP that mobile computer 164 can communicate with computer network 150₁It is assumed that you will engage in a communication session with. Mobile client computer 164 (Figure 3) is a wireless access point AP₁, AP₂, AP₃, And AP₄Receive signals from and measure the strength of the signals received from each wireless access point. Enter the signal strength value for the wireless access point into the procedure (block 178, Figure 4). The mobile client computer 164 records the calculated intensity value for each radio access point, along with the location identifier for each radio access point (block 180, FIG. 4). The mobile client 164 then weights the strength value of the wireless access point that connects it (block 182, Figure 4). Weighting this value is generally based on the premise that mobile client computers are more likely to establish communication sessions with wireless access points in close proximity to them. In this example, AP₁Weight the signal strength value for.

【0020】

The mobile client computer 164 then appropriately weights its intensity value based on how long it has been obtained, with the most recently obtained value receiving the most weight. Also, the value received when it is not the most recent receives the least weight (block 184, Figure 4). Weighting the intensity values in a way that is inversely proportional to those times compensates for the possibility of altered conditions, such as the user moving the mobile client computer. The mobile client computer 164 then sums the weighted intensity values (block 186, Figure 4). The sum is performed by location and multiple access points are averaged. For example, AP₁And AP₂If are in the same position (ie, they have the same position identifier), average their respective weighted intensity values. Consider the location identifier that gives the maximum total value as the location of the client computer (block 188, Figure 4). For example, this position may be represented as a physical position, a relative position, or depending on the grid type system. For example, one way to indicate location within a corporate facility would be to divide the facility by building, by floor, and by four divisions of each floor. AP₁And AP₂Are both on the 1st, 1st floor, north side of the building, AP₃Is on the 1st floor, south side, AP₄Is on the ground floor, on the southeast corner. 1st floor, north side (AP₁And AP₂The sum weighted against (averaged sum for) is the south side (AP)₃) And AP in the southeast corner₄If it is higher than the weighted total of, consider the mobile client computer 164 to be on the north side of the ground floor. The mobile client computer 164 is represented by blocks 178-186 of FIG. 4 until it shuts down (block 190, FIG. 4) and after a preset delay period (block 192, FIG. 4). Repeat the steps.

【0021】

According to some embodiments of the invention , the mobile client computer 164 maintains a moving window for signal strength measurement. For example, it can discard the oldest measurement after each iteration by obtaining a number of preset measurements from each wireless access point. For example, if the preset number of measurements is 10, the mobile client computer 164 will discard the oldest measurement on and at each iteration following the 10th measurement.

【0022】

The procedure in FIG. 4 is described as being performed by the mobile computer 164, but those skilled in the art may perform all or part of this procedure on any of any wireless access points 154-162, or mobile. You will recognize that it can be done alternatives on the wireless network interface card combined with the client computer 164.

【0023】

An example of how the general procedure described in conjunction with FIG. 4 is performed by embodiments of the present invention is described below. Seeing Figure 3, the mobile wireless client computer 164 is already a wireless access point AP.₁Assuming you have established a communication session with, and wireless access point AP₁It communicates with the corporate network 150 through. To calculate its own location, the mobile client computer 164 identifies each wireless access point within scope. There are various ways this can be done. In one practice, the wireless access points broadcast their IP and / or MAC addresses on a periodic basis, respectively, and detect their IP and / or MAC address by their mobile client computer 164. The mobile client computer 164 then queries the corporate network 150 for its location identifiers that correspond to these IP and / or MAC addresses. The corporate network 150 then retrieves its location identifier from database 172, and the wireless access point AP.₁Send them to that mobile client computer 164 via. In other implementations, the mobile client computer 164 obtains its location identifiers directly from those wireless access points, which broadcast them periodically or respond to inquiries from the mobile client computer 164. And broadcast them.

【0024】

Next, the mobile client computer 164 is a wireless access point AP.₁, AP₂, AP₃, And AP₄Get a sample of those signals received from. Here we will introduce the four constants used in this embodiment.

【0025】

[table 1]<img file="JP2004040775A_D0001.tif" /> 【0026】

The mobile client computer 164 first measures the strength of the signal received from each wireless access point in dBM (decibels per milliwatt) and records the measured value. To aid in exemplifying this practice, sample values for a group are shown in Table 1. Here, t = 4, min = -30, and k = 2.

【0027】

[Table 2]<img file="JP2004040775A_D0002.tif" /> 【0028】

The mobile client computer 164 then effectively ignores all measurements less than min by setting such a measurement equal to min. Then, the absolute value of the difference between min and the measured signal strength, that is, | min-measured signal strength |, changes the measured strength value for each sample. The changed values are shown in Table 2.

【0029】

[Table 3]<img file="JP2004040775A_D0003.tif" /> 【0030】

Wireless access point associated with mobile client computer 164, AP in this example₁For the sample obtained from, the value obtained is weighted by k. The results are shown in Table 3.

【0031】

[Table 4]<img file="JP2004040775A_D0004.tif" /> 【0032】

Each sample value is then weighted by factors related to sample timing. The general form for this weight is [0033]

[Formula 1]<img file="JP2004040775A_D0005.tif" /> 【0034】

In this example, t = 4, so the denominator is calculated as 1 + 2 + 3 + 4 = 10. The weighted values are shown in Table 4.

【0035】

[Table 5]<img file="JP2004040775A_D0006.tif" /> 【0036】

If the mobile client computer 164 is still unable to observe the sampling period t, the time-based weights should be based on the number of observations received so far. As more samples are recorded, their weights change for each sampling period until t samples are received.

【0037】

The mobile client computer 164 then sums the intensity values of the sample obtained from the wireless access points having the same location identifier. In this example, each radio access point has a different location identifier, the summed and weighted values of which are shown in Table 5.

【0038】

[Table 6]<img file="JP2004040775A_D0007.tif" /> 【0039】

The mobile client computer 164 then determines which of the total values is the highest, and considers itself to be located in the position with the highest total value. In this example, its highest total value is -16.7, AP₂Is consistent with. AP₂Has a location identifier of "1st floor NE". Therefore, the mobile client computer 164 is considered to be located in the northwestern part of the first floor. The mobile client computer 164 returns this information to the corporate network 150, which can provide the information to the users of the network.

【0040】

In various embodiments of the invention, information about the network's wireless access points is entered into the network's central database when the wireless access points are set up. With reference to Figure 5, we will now describe an example of an interface that network administrators can use to enter that information during setup. The interface has several entry fields, including a name field, a location field, a comment field, a MAC address field, and an IP address field. The administrator can fill in these fields with the following data. Name: Name for this access point Location: Location of the access point used by the location algorithm Comments: Administrator comments MAC address: Access point's assigned hardware address IP address: Access point's assigned IP address. Input control works similarly for IP address input in the TCP / IP Network Properties dialog.

【0041】

Once you enter the name, location, comment, and at least one of the MAC or IP addresses, you should enable the Create button. After pressing the Create button, the value is added to the database and clears the contents of the form.

【0042】

If the administrator types something in the dialog and then presses Close, he should ask the user if he wants to discard the changes. A Yes reply closes the dialog, while a No reply returns the user to the dialog.

【0043】

The Import button displays a standard Windows® file open dialog to help you enable masking of imported file types, such as "comma-separated text files (* .txt)". After selecting the file, the database imports the information into the file and automatically closes the Add Access Point dialog box.

【0044】

In yet another practice, the methods and systems described herein further determine how far the mobile client computer is from the wireless access point. This is achieved by obtaining one of the sample signal strength values, and by applying Power Law to obtain the radial distance from the wireless access point.

【0045】

Power low can be expressed as follows.

【0046】

[Formula 2]<img file="JP2004040775A_D0008.tif" /> 【0047】

Where P_signalIs the energy of the signal received by the mobile client computer from the wireless access point, P_knownpointIs the energy of the signal generated by that wireless access point, d_knownpointIs the distance to the access point and d is the distance to the mobile user. The term r is a constant, and its value is generally considered to be four (4) for indoor communications and two (2) for outdoor communications.

【0048】

Therefore, it can be understood that it provides a new and useful method for the positioning of mobile computers. In addition to many of the features of the various embodiments described herein, the present invention eliminates the need to use expensive methods such as satellite positioning systems such as the (whole) Global Positioning System (GPS). To do.

【0049】

In view of many possible embodiments to which the principles of the invention may be applied, the embodiments described herein with respect to the drawings are meant to be merely exemplary, limiting the scope of the invention. It should be recognized that it should not be captured. For example, one of ordinary skill in the art may implement the elements of the illustrated embodiment shown in the software in hardware and vice versa, or the illustrated embodiment. You will recognize that you can make changes in placement and detail without departing from the spirit of invention. Therefore, the invention described herein anticipates all embodiments that may fall within the claims and their equivalents.

[Simple explanation of drawings]

【0050】

FIG. 1 is a diagram showing an example of a computer network in which the present invention can be implemented.

FIG. 2 is a diagram illustrating an example of a computer in which at least some parts of the invention can be run.

FIG. 3 is a diagram illustrating an example of a viable corporate network.

FIG. 4 illustrates an overall procedure that may follow embodiments of the present invention.

FIG. 5 illustrates an example of a user interface that allows a network administrator to enter information about wireless access points in a network.

[Explanation of symbols]

【0051】

100 Computer 102 Network 112 Processing Equipment 118 Display 150 Corporate Network 152 Internet 164 Mobile Client Computer 166 Client Computer 168, 170 User 172 Database