Source: http://www.google.nl/patents/US7212828
Timestamp: 2018-01-16 07:16:57
Document Index: 388840512

Matched Legal Cases: ['art 2004', 'art 2010', 'art 2014', 'art 2009', 'art 2014', 'art 2017', 'art 2003']

Patent US7212828 - Monitoring changeable locations of client devices in wireless networks - Google Patenten
Security of wireless networks is improved by rejecting traffic from a wireless device located outside a defined spatial boundary. The device's spatial position with respect to the boundary is determined using directional antenna arrays on a plurality of measurement points, and calculating where the vectors...http://www.google.nl/patents/US7212828?utm_source=gb-gplus-sharePatent US7212828 - Monitoring changeable locations of client devices in wireless networks
Publicatienummer US7212828 B2
Aanvraagnummer US 10/334,263
Publicatiedatum 1 mei 2007
Aanvraagdatum 31 dec 2002
Prioriteitsdatum 31 dec 2002
Ook gepubliceerd als CA2508077A1, CN1732709A, CN100450269C, DE60304905D1, DE60304905T2, EP1579722A1, EP1579722B1, US20040203908, WO2004060008A1
Publicatienummer 10334263, 334263, US 7212828 B2, US 7212828B2, US-B2-7212828, US7212828 B2, US7212828B2
Uitvinders John R. Hind, Marcia L. Stockton
Patentcitaties (14), Niet-patentcitaties (16), Verwijzingen naar dit patent (33), Classificaties (11), Juridische gebeurtenissen (5)
US 7212828 B2
1. A computer-implemented method of ensuring that client devices remain inside a defined spatial boundary, comprising steps of:
identifying a plurality of client devices that are to remain inside a defined spatial boundary, each of the client devices participating in a wireless local area network (“WLAN”) with which the defined spatial boundary is associated; and
monitoring whether each of the client devices remains inside the defined spatial boundary, wherein the monitoring step further comprises, for each of the client devices, the steps of:
receiving, at a first device on the WLAN, measurement data from a plurality of measurement points on the WLAN, wherein the measurement data for each measurement point comprises a reading indicating an angle of radio transmission observed upon a transmission by the client device, the angle observed by a plurality of antenna elements of the measurement point, the antenna elements being capable of determining an angle to a source of radio transmission;
computing, by the first device, a current location of the client device using the received measurement data;
comparing, by the first device, the computed location of the client device to the defined spatial boundary to determine whether the client device remains inside the defined spatial boundary; and
triggering, by the first device, an out-of-boundary action for the client device if the comparing step determines that the client device does not remain inside the defined spatial boundary;
wherein the defined spatial boundary is dynamically defined at set-up time, the dynamic defining further comprising steps of:
physically moving a training client device near selected ones of measurement points on the WLAN while the training client device repeatedly transmits to a set-up application in the first device and while the first device repeatedly receives boundary measurement data from the selected ones of the measurement points, wherein the boundary measurement data received from each selected measurement point comprises a boundary reading indicating the angle of radio transmission observed by the selected measurement point upon the transmission by the moving training client device as it transmits to the set-up application in the first device;
computing, by The first device, successive locations of the moving training client device using the received boundary measurement data; and
using, by the set-up application, the successive locations to dynamically define the spatial boundary.
2. The method according to claim 1, further comprising the step of allowing each of the client devices to access the WLAN only while the comparing step determines that the client device remains inside the defined spatial boundary.
3. The method according to claim 1, wherein the out-of-boundary action comprises deactivating at least one function of each client device for which the out-of-boundary action is triggered.
4. The method according to claim 1 wherein the first device periodically transmits a cryptographic key from the first device to each of the client devices, the cryptographic key being required to unlock at least one of the functions of each of the client devices, and wherein the out-of-boundary action further comprises the step of ceasing the transmission to each of the client devices for which the comparing step determines that the client device does not remain inside the defined spatial boundary, thereby preventing access to the at least one function of that client device for which the cryptographic key is required for unlocking.
5. The method according to claim 1, wherein the out-of-boundary action comprises activating an alarm.
6. A system for ensuring that client devices remain inside a defined spatial boundary, comprising:
a plurality of client devices that are to remain inside a defined spatial boundary, each of the client devices participating in a wireless local area network (“WLAN”) with which the defined spatial boundary is associated; and
means for monitoring whether each of the client devices remains inside the defined spatial boundary, wherein the means for monitoring, for each of the client devices, further comprises:
means for receiving, at a first device an the WLAN, measurement data from a plurality of measurement points on the WLAN, wherein the measurement data for each measurement point comprises a reading indicating an angle of radio transmission observed upon a transmission by the client device, the angle observed by a plurality of antenna elements of the measurement point, the antenna elements being capable of determining an angle to a source of radio transmission;
means for computing, by the first device, a current location of the client device using the received measurement data;
means for comparing, by the first device, the computed location of the client device to the defined spatial boundary to determine whether the client device remains inside the defined spatial boundary; and
means for triggering, by the first device, an out-of-boundary action for the client device if the means for comparing determines that the client device does not remain inside the defined spatial boundary;
wherein the defined spatial boundary is dynamically defined at set-up time, the dynamic defining further comprising:
physically moving a training client device near selected ones of the measurement points an the WLAN while the training client device repeatedly transmits to a set-up application in the first device and while the first device repeatedly receives boundary measurement data from the selected ones of the measurement points, wherein the boundary measurement data received from each selected measurement point comprises a boundary reading indicating the angle of radio transmission observed by the selected measurement point upon the transmission by the moving training client device as it transmits to the set-up application in the first device;
means for computing by the first device, successive locations of the moving training client device using the received boundary measurement data; and
means for using, by the set-up application, the successive locations to dynamically define the spatial boundary.
7. The system according to claim 6, further comprising means for allowing each of the client devices to access the WLAN only while the means for comparing determines that the client device remains inside the defined spatial boundary.
8. The system according to claim 6, wherein the out-of-boundary action comprises deactivating at least one function of each client device for which the out-of-boundary action is triggered.
9. The system according to claim 6, wherein the first device periodically transmits a cryptographic key from the first device to each of the client devices, the cryptographic key being required to unlock at least one of the functions of each of the client devices, and wherein the out-of-boundary action further comprises ceasing the transmission to each of the client devices for which the means for comparing determines that the client device does not remain inside the defined spatial boundary, thereby preventing access to the at least one function of that client device for which the cryptographic key is required for unlocking.
10. The system according to claim 6, wherein the out-of-boundary action comprises activating an alarm.
11. A computer program product for ensuring that client devices remain inside a defined spatial boundary, the computer program product embodied on one or more computer readable media readable by a computing system in a computing environment and comprising:
computer-readable program code for identifying a plurality of client devices that are to remain inside a defined spatial boundary, each of the client devices participating in a wireless local area network (“WLAN”) with which the defined spatial boundary is associated; and
computer-readable program code for monitoring whether each of the client devices remains inside the defined spatial boundary, wherein the computer-readable program code for monitoring, for each of the client devices, further comprises
computer-readable program code for receiving, at a first device on the WLAN, measurement data from a plurality of measurement points on the WLAN; wherein the measurement data for each measurement point comprises a reading indicating an angle of radio transmission observed upon a transmission by the client device, the angle observed by a plurality of antenna elements of the measurement point, the antenna elements being capable of determining an angle to a source of radio transmission;
computer-readable program code for computing, by the first device, a current location of the client device using the received measurement data;
computer-readable program code for comparing by the first device, the computed location of the client device to the defined spatial boundary to determine whether the client device remains inside the defined spatial boundary: and
computer-readable program code for triggering, by the first device, an out-of-boundary action for the client device if the computer-readable program code for comparing determines that the client device does not remain inside the defined spatial boundary;
wherein the defined spatial boundary defined at set-up time, the dynamic defining further comprising:
physically moving a training client device near selected ones of the measurement points on the WLAN while the training client device repeatedly transmits to a set-up application in the first device and while the first device repeatedly receives boundary measurement data from the selected ones of the measurement points, wherein the boundary measurement data received from each selected measurement point comprises a boundary reading indicating the angle of radio transmission observed by the selected measurement point upon the transmission by the moving training client device as it transmits to the set-up application in the first device;
12. The computer program product according to claim 11, further comprising computer-readable program code for allowing each of the client devices to access the WLAN only while the computer-readable program code for comparing determines that the client device remains inside the defined spatail boundary.
13. The computer program product according to claim 11, wherein the out-of-boundary action comprises deactivating at least one function of each client device for which the out-of-boundary action is triggered.
14. The computer program product according to claim 11, wherein the first device periodically transmits a cryptographic key from the first device to each of the client devices, the cryptographic key being required to unlock at least one of the functions of each of the client devices, and wherein the out-of-boundary action further comprises ceasing the transmission to each of the client devices for which the computer-readable program code for comparing determines that the client device does not remain inside the defined spatial boundary, thereby preventing access to the at least one function of that client device for which the cryptographic key is required for unlocking.
15. The computer program product according to claim 11, wherein the out-of-boundary action comprises activating an alarm.
16. A computer-implemented method of ensuring that client devices remain inside a defined spatial boundary, comprising steps of:
identifying a plurality of client devices that are to remain inside a defined spatial boundary, each of the client devices participating in a wireless local area network (“WLAN”) with which the defined spatial boundary is associated;
monitoring whether each of the client devices remains inside the defined spatial boundary, wherein the monitoring step, for each of the client devices, further comprises steps of;
receiving, at a first device on the WLAN, measurement data from a plurality of measurement points on the WLAN, wherein the measurement data for each measurement point comprises a reading indicating an angle of radio transmission observed upon a transmission by the client devices, the angle observed by a plurality of antenna elements of the measurement point, the antenna elements being capable of determining an angle to a source of radio transmission;
computing, by the first device, a current location of the client device using the received measurement data; and
determining, by the first device using the computed location of the client device, whether the client device remains inside the defined spatial boundary, the defined spatial boundary having been dynamically defined set-up time, the dynamic defining further comprising steps of:
using, by the set-up application, the successive locations to dynamically define the spatial boundary; and
if the monitoring step determines that any of the client devices does not remain inside the defined spatial boundary, performing at least one of (1) deactivating at least function of such devices and (2) activating an alarm; and
charging a fee for carrying out the monitoring step.
The present invention is related to commonly-assigned U.S. Pat. Ser. No. 10/335,148, filed concurrently herewith, which is entitled “Spatial Boundary Admission Control for Wireless Networks”, and which is hereby incorporated herein by reference.
The present invention relates to security of computer networks, and deals more particularly with methods, systems, computer program products, and methods of doing business whereby access to a wireless network is controlled based on a device's presence within a spatial boundary. The disclosed techniques may also be used for determining whether devices remain within a spatial boundary.
“WiFi” (for “wireless fidelity”) or “Wi-Fi”® is the label commonly applied to devices following the Institute of Electrical and Electronics Engineers (“IEEE”) 802.11b specification. This abbreviation is taken from the logo of an industry interoperability group (Wireless Ethernet Compatibility Alliance, Inc., or “WECA”, also known as the Wi-Fi Alliance) that certifies compliant products. (“Wi-Fi” is a registered trademark of Wireless Ethernet Compatibility Alliance, Inc.) WiFi technology allows a raw wireless data transmission rate of approximately 11 Mbps at indoor distances from several dozen to several hundred feet, and outdoor distances of several to tens of miles using an unlicensed portion of the 2.4 GHz band in 14 overlapped channels.
While two modes of operation are possible, namely peer-to-peer and network, most WiFi installations use the network form where an “access point” serves as a hub bridging client adapters to one another and to a wired network, often using Network Address Translation (“NAT”) technology. See FIG. 1, where this configuration is illustrated. When a client wants to join a network hosted by an access point, it must first synchronize with that network by performing the following synchronization protocol steps. First, to establish initial communications, it either listens for a “beacon” sent periodically by the access point or sends a “probe” and awaits a response. Next, the client undergoes an authentication process with the access point. If that is successful, the client proceeds to an association process which sets up a logical session over which higher-layer protocols and data may flow. At any point thereafter, either the access point or the client may terminate the association, shutting down further data communications. After the association is terminated, no further data communication can occur until the aforementioned synchronization protocol is repeated to join the network anew.
The world of WiFi is no longer confined to expensive-gadget-happy geeks, but is being embraced by everyday people who love the convenience of being mobile. Mass production has made access points and client adapters so inexpensive that WiFi is being widely used for networking in many places, including homes and small offices, replacing the high-cost special wiring of the past and allowing folks to easily move their computing workspace on a moment-to-moment whim. As the majority of users purchasing commodity-priced WiFi gear are non-technical, they have no insight to the underlying technology nor do they understand the side effects of its use.
Unfortunately, WiFi has also attracted the hacker fringe, who view its deployment as an invitation to steal access to the Internet and/or locally-available services. The poor security which has been identified in WiFi's standard protocols (see, for example, “Wireless networks wide open to hackers” by Robert Lemos, which may be found on the Internet at http://news.com.com/2100-1001-269853.html?tag=bplst ), coupled with cheap ways to intercept the radio signals miles outside the nominal 300 foot service radius (see “Antenna on the Cheap” by Rob Flickenger, located on the Internet at http://www.oreillynet.com/cs/weblog/view/wlg/448) has opened the barn door to even the lowly budget-strapped high school “script kiddy”. With this trend, new terms for wireless hacking have emerged, such as “War Driving” and “Warchalking”. War driving is the activity of locating WiFi networks that can easily be tapped from a laptop in a car. (See “WAR DRIVING” by Sandra Kay Miller, located on the Internet at http://www.infosecuritymag.com/articles/november01/technology_wardriving.shtml, for an article on this topic.). Warchalking is the practice of marking the presence of WiFi networks (for example, on the side of a building where a WiFi network is detected by a “war driver”, or on the sidewalk in front of the building) so they are easy to locate without a device such as the $6.45 “Pringles” can antenna (described in the above-mentioned “Antenna on the Cheap” article) used by the war drivers.
What is needed is a way of improving security in WiFi networks to prevent intrusion by unauthorized devices. The solution must be easy to set up, even in a home environment, and must not require changes to the WiFi standards or to existing client device adapters.
To achieve the foregoing objects, and in accordance with the purpose of the invention as broadly described herein, the present invention provides methods, systems, and computer program products for monitoring a changeable location of one or more client devices in a wireless network. In a preferred embodiment, this technique comprises: receiving, at a first device on the WLAN, measurement data from a plurality of measurement points on the WLAN, wherein the measurement data for each measurement point comprises a reading for a particular client device, the reading observed by a plurality of antenna elements of the measurement point, the antenna elements being capable of determining an angle to a source of radio transmission; computing, by the first device, a current location of the particular client device using the received measurement data; and determining, by the first device, whether the current location of the particular client device is within a predetermined spatial boundary.
The present invention may also be provided as methods of doing business, whereby a service is offered to clients for determining whether their wireless devices are within, or remain within, a particular spatial boundary. This service may be provided under various revenue models, such as pay-per-use billing, monthly or other periodic billing, and so forth.
FIG. 2 illustrates a plurality of remote wireless sensors and a base station, also referred to herein as “measurement points”, deployed in a wireless network for determining a client device's location according to preferred embodiments of the present invention;
FIG. 5 illustrates how angular measurements at two measurement points may suffice to narrow the spatial position of a transmission source to an intersection zone, according to preferred embodiments of the present invention; and
The present invention overcomes problems of the prior art using a modified WiFi access point (also called a “base station”) and at least two remote wireless sensors, all participating in the WiFi network to be protected, and preferably deployed in an equilateral triangle configuration. See FIG. 2. These devices are referred to herein as “measurement points”. Each measurement point is equipped with a directional antenna capable of determining the angle to the source of radio transmissions. By intersecting the directional vectors measured at each measurement point, the present invention determines the spatial position of devices attempting to access the network, and classifies them as being inside or outside a defined boundary. See FIG. 3. Devices inside the boundary are allowed to connect to the network (assuming, of course, that the previously-discussed synchronization protocol completes successfully), while devices outside the boundary are not.
Preferred embodiments of the present invention use an antenna array at each measurement point to determine the angular direction of the client's transmission. An “antenna array” is any prior-art arrangement of antenna elements capable of discerning the directionality of a radio signal. (That is, the measurement point's directional antenna may be a single antenna comprised of multiple antenna elements in an array, or a plurality of antennas that are individually not directional but which are directional when used together as an array.) in simple wireless networks such as a single-occupant house or an office building, two-element arrays at each measurement point may suffice to define a 2-dimensional boundary. For more complex arrangements where a 3-dimensional spatial boundary is needed, each measurement point can employ a multiple-element array to measure the angle of the received signals in 3 dimensions.
The base station, upon receiving angular readings from each measurement point for a given association (i.e., for a given client session with the base station), computes the client's position with respect to a defined boundary. If this position falls outside the defined boundary, the base station terminates the association, forcing the client to re-authenticate before it can receive or send layer three data. This process is described in more detail below, with reference to FIG. 6.
Each measurement point is equipped with an antenna array that intercepts radio transmissions from client devices. The processing of a client transmission at a measurement point is illustrated by logic in FIG. 4. Upon detecting a transmission (Block 400), the measurement point preferably measures the angular relationship between the signal source and the antenna array (Block 410), decodes the WiFi packet to extract the client association identifier (Block 420), locates an appropriate slot in a buffer corresponding to the association (Block 430), and saves the angular value in that slot (Block 440). The angular relationship may be determined using suitable prior art techniques such as phase angle, which may be implemented using a digital signal processor or other suitable hardware/software combination.
To prevent excessive communications overhead between the base station and the other measurement points and to reduce the base station's processing load, the measurement points preferably collect, sort, and reduce instantaneous readings over a short period, say a few seconds. For every unique association seen in client transmissions, the measurement point then reports a single, most-recent angle for this association to the base station. This reporting process is illustrated in FIG. 4, where Block 450 tests to see if the reporting is triggered. (For example, when a timer is used to measure the preferably-short reporting period, Block 450 comprises determining whether the timer has popped.) If so, then the measurement point transmits saved values for one or more associations to the base station (Block 460). Alternatively, the processing of Blocks 450 and 460 may be separated from the processing of Blocks 400-440. (For example, a separate thread may be used for implementing the reporting.) In this case, the reporting may occur independently of receiving a client transmission.
The diagram in FIG. 5 depicts how angular measurements at two measurement points may suffice to narrow the spatial position of a transmission source to an intersection zone. Depending on the type of antenna array employed, it may not be possible to know the precise angle. The phase angle method in preferred embodiments of the present invention can determine a vector (e.g., vector α), where the transmitter could be located at α degrees +/− some tolerance, with respect to an individual antenna array. (Depending on the antenna array in use, the phase angle method might only be able to determine that the transmitter is either at α degrees, plus or minus some tolerance, or at α+180 degrees, plus or minus the same tolerance.) The intersection of these vectors from the two measurement points forms an “intersection zone”, where this intersection zone indicates the transmitter's approximate position in a 2-dimensional space.
To define a 2-dimensional planar boundary, e.g., using 3 measurement points, ideally the measurement points are positioned in an equilateral triangle with vertices near the defined boundary. FIGS. 2 and 3 illustrate a circular boundary using dotted line. In this example, the cell phone 115 and laptop 120 devices would be prevented from accessing the network, since they are outside the spatial boundary, but the pager 110 device would be allowed access. Preferably, each measurement point's antenna array is oriented approximately 60 degrees from the other two measurement point's antenna arrays.
On receiving measurement data from a remote measurement point (Block 600), the base station stores this data in a table or similar data structure (Block 610). Recall that, in preferred embodiments, the base station itself hosts an additional measurement point, and thus locally-received input (which may be processed by the base station, in its role as a measurement point, using logic in FIG. 4) is also stored in this table. (Alternatively, an additional remote measurement point might replace the base station in its role of observing and reporting device locations, without deviating from the scope of the present invention.) Preferably, the rows of the table correspond to client associations observed during a measurement interval. The first column contains the association identifier. Additional columns correspond to each measurement point. See FIG. 7, where a sample table is illustrated. In this sample table 700, the association identifier is stored in column 705, the data observed by the base station itself is stored in column 710, and data reported by two remote measurement points (“MP1” and “MP2”) is stored in columns 715 and 720, respectively. Additional columns may be added for implementations using more than three measurement points.
In one aspect, the test in Block 620 is timer-driven. For example, a collection interval may be defined, and the table entries that have been collected during this interval are then processed when the collection interval expires. One way in which this aspect may be implemented is illustrated by logic in FIG. 8. Upon receipt of data from a measurement point, a time stamp is preferably associated with the data as it is recorded in an augmented version of the table of FIG. 7 (Block 610′). This time stamp may be the arrival time at the base station, or in alternative implementations it may be a time stamp reported by the measurement point. (In the latter case, a reliable clock-synchronizing algorithm is preferably used to synchronize the clocks of the various measurement points. Clock-synchronizing algorithms are known in the art, and do not form part of the inventive concepts of the present invention.)
Block 620′ comprises checking to see if more than one measurement point (including the base station) has reported data during the current collection interval. The collection interval is preferably a predefined constant (or a configurable parameter), and should be small enough so that if a client is mobile (e.g., in a car or being carried by a person), it cannot have travelled very far during the interval. The collection interval should also be greater than or equal to the reporting interval used by the measurement points, so that if the measurement points report at different times, data from multiple measurement points will be available within a single collection interval. Thus, if the test in Block 620′ has a negative result, control returns to Block 600 of FIG. 6 to await measurements from other measurement points within this collection interval. When data is available from multiple measurement points for this collection interval, on the other hand, Block 800 locates all such data (and may remove stale entries from the table, or may simply discard any measurements that fall outside the current interval), and this data is used in Block 630 of FIG. 6 when computing the client's position.
Preferably, the defined boundary is learned at set-up time by carrying a client device around the intended boundary while communicating with a set-up application in the base station. With the remote reporting interval having been set to a very small value, the base station learns the angular coordinates of the boundary with respect to the measurement points, but need not know the actual dimensions involved (since it does not know the scale of distance involved). Setting the reporting interval to a larger or smaller value (and/or altering the speed of movement of the client device) during this set-up process allows a base station to learn a boundary at a different level of granularity.
Prior art software approaches are known which attempt to use relative signal strength triangulation to locate wireless local area network (“WLAN”) clients. As one example, the Positioning Engine from Ekahau, Inc. is a commercially-available product that may be used for tracking device locations in a WLAN. While this product offers a number of advantages, because of signal attenuation and device transmission characteristics, extensive mapping of the entire area of coverage may be needed to produce highly-accurate results. (Accurate results require using client adapters whose relative characteristics to the device used in the mapping are known. That is, the transmitted power or effective radiated power from the attached or built-in antenna, at various angles, must be known, since this approach relies on signal strength.) This approach also needs multiple full-wired access points (at least three), and changing the content of the area monitored (for example, moving furniture around) requires a recalibration. For each interior mapped point, location coordinates are needed to pair with the signal strength readings.
The present invention uses a different approach, as described in detail above. It does not rely on signal strength and hence on client adapter/antenna characteristics. The present invention is not impacted by the content (e.g., furniture, walls, books, etc.) of the monitored area or changes to that content. The training process used in preferred embodiments comprises simply walking the boundary, without needing to tell the system where the moving device is at each measurement. The remote sensing device uses the WLAN to report readings, and therefore does not need multiple access points.
The present invention has been described with reference to its use in determining whether mobile devices are inside or outside a spatial boundary. However, this is for purposes of illustration and not of limitation. The inventive techniques described herein may be used for devices that are stationary devices as well (including a mobile device that has become stationary). The present invention may also be used to ensure that one or more devices remain within a defined spatial boundary. For example, a theft-prevention system may be implemented in an office setting, retail store, warehouse, etc. using techniques disclosed herein. Suppose that an electronics store wishes to prevent thefts of relatively-expensive wireless gadgets. The devices can be defined as participants in a WLAN. An enumerated list of these devices can be created, and a system using techniques disclosed herein can then test for the devices on this list remaining within the defined boundary (e.g., the showroom and/or stockroom). If a device that is supposed to be within the store moves outside the boundary, instead of rejecting its participation in the wireless network (as described above with reference to Blocks 640 and 650 of FIG. 6), the base station might activate an audible alarm or perhaps send a signal to the device to cause it to sound its own alarm, flash lights, etc. Similarly, the continued presence of wireless devices at a museum, trade show, hotel, office, or other business location can be monitored in the same manner. Guests can therefore use the devices while visiting the premises, but are effectively discouraged from removing the devices from that location.
Another application of the disclosed techniques is to disable the functionality of a wireless device if the device crosses a defined boundary. For example, a cryptographic key might be transmitted from the base station to a wireless device periodically, allowing the device to “unlock” its software and render that software usable. If the device moves outside the boundary, the base station ceases transmitting the key. The device may then continue to work from an electrical standpoint, but the absence of the key causes the software to just stop working.
The present invention may be provided as method(s) of doing business. For example, a business entity may provide a service that monitors the location of devices using techniques disclosed herein. This service may be provided under various revenue models, such as pay-per-use billing, monthly or other periodic billing, and so forth.
While preferred embodiments have been described with reference to radio-based wireless (i.e., WiFi or 802.11b) networks, this is for purposes of illustration but not of limitation; the disclosed techniques may be applied to other types of wireless networks as well.
As will be appreciated by one of skill in the art, embodiments of the present invention may be provided as methods, systems, or computer program products. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (augmented by the antennas and measurement point devices and adapters), or an embodiment combining software and hardware aspects, Furthermore, the present invention may be embodied in a computer program product which is embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein.
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Classificatie in de VS 455/456.1, 340/568.1, 340/573.4, 455/67.11, 455/411
Internationale classificatie G08B23/00, H04L12/28, G08B13/14, H04W64/00
10 maart 2003 AS Assignment
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HIND, JOHN R.;STOCKTON, MARCIA L.;REEL/FRAME:013826/0696;SIGNING DATES FROM 20030116 TO 20030127
1 mei 2015 LAPS Lapse for failure to pay maintenance fees
23 juni 2015 FP Expired due to failure to pay maintenance fee