Title of Invention

"A METHOD FOR CALIBRATING AN ACCELERATION MEASUREMENT CIRCUIT"

Abstract

A method for determining a location of a mobile terminal (300, 400), the method comprising: determining a first location of the mobile terminal (300, 400) based on wireless communication signals received by the mobile terminal (300, 400); measuring acceleration of the mobile terminal (300, 400) to generate acceleration information; determining a distance that the mobile terminal (300, 400) has moved from the first location based on the acceleration information; combining the determined distance and the first location to determine a second location of the mobile terminal (300, 400); determining whether the mobile terminal (400) has moved at least a threshold distance from the first location; and responsive to determining that the mobile terminal (400) has moved at least the threshold distance from the first location determining a reference location of the mobile terminal (400) based on the wireless communication signals; and calibrating the acceleration information based on the second location and the reference location.

Full Text

MOBILE TERMINALS AND METHODS FOR DETERMINING A LOCATION BASED ON ACCELERATION INFORMATION BACKGROUND OF THE INVENTION The present invention relates to the field of communications in general and more particularly, to determining the geographic location of a mobile terminal. Wireless communication systems (networks) are commonly employed to provide voice and data communications to subscribers. For example, analog cellular radiotelephone systems, such as those designated AMPS, ETACS, NMT-450, and NMT-900, have long been deployed successfully throughout the world. Digital cellular radiotelephone systems such as those conforming to the North American standard IS-54 and the European standard GSM have been in service since the early 1990's. More recently, a wide variety of wireless digital services broadly labeled as PCS (Personal Communications Services) have been introduced, including advanced digital cellular systems conforming to standards such as IS-136 and IS-95, lower-power systems such as DECT (Digital Enhanced Cordless Telephone) and data communications services such as CDPD (Cellular Digital Packet Data). These and other systems are described in The Mobile Communications Handbook, edited by Gibson and published by CRC Press (1996). It is desirable, and in certain places mandated by law, that mobile telecommunication network providers be able to determine an approximate geographical location of a mobile terminal, such as, for example, an actively communicating cellular telephone. A variety of mobile terminal location techniques have been proposed. These location techniques include uplink signal location, downlink signal location, Global Positioning System (GPS) based approaches, assisted GPS approaches combining communication signals and GPS signals and approaches based on digital television signals. For "uplink signal" location techniques, the mobile telecommunications network is typically configured to determine where the mobile terminal is located based on ranging measurements associated with one or more uplink signals. These uplink signals are transmitted by the mobile terminal and received by a number of receivers having known locations, such as, for example, cellular telephone base stations (BSs). For the "downlink signal" location techniques, the mobile network. In a typically GPS application, the GPS receivers collect and analyze ranging measurements from signals transmitted by GPS satellites having known locations. As illustrated in Figure 2, GPS is a space-based triangulation system using satellites 42 and GPS control computers 48 to measure positions anywhere on the earth. GPS was first developed by the United States Department of Defense as a navigational system. The advantages of this navigational system over land-based systems are that it is not limited in its coverage, it provides continuous 24-hour coverage, which may be highly accurate regardless of weather conditions. In operation, a constellation of 24 satellites 42 orbiting the earth continually emit a GPS radio signal 44. A GPS receiver 46, e.g., a hand-held radio receiver with a GPS processor, receives the radio signals from the closest satellites and measures the time that the radio signal takes to travel from the GPS satellites to the GPS receiver antenna. By multiplying the travel time by the speed of light, the GPS receiver can calculate a range for each satellite in view. Ephemeris information provided in the satellite radio signal typically describes the satellite's orbit and velocity, thereby generally enabling the GPS processor to calculate the position of the GPS receiver 46 through a process of triangulation. It is known to include a GPS receiver 46 in a mobile terminal 22 to provide position location functionality to the mobile terminal 22. The process of monitoring GPS signals or base station signals may be significantly affected by environmental factors. For example, GPS signals or base station signals that may be easily acquired in the open typically become harder to acquire when a receiver is within a building, a vehicle, and/or under foliage. SUMMARY OF THE INVENTION In some embodiments of the invention, an acceleration measurement circuit is calibrated based on wireless communication signals that are received by a mobile terminal. A location of the mobile terminal is then determined using the calibrated acceleration measurement circuit. In some further embodiments of the invention, a timing circuit may be calibrated based on the wireless communication signals and used by the acceleration measurement circuit to measure a distance that the mobile terminal has traveled over BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic block diagram illustrating a conventional terrestrial wireless communication system; Figure 2 is a schematic block diagram illustrating a conventional GPS system; Figure 3 is a schematic block diagram illustrating a mobile terminal according to some embodiments of the invention; Figure 4 is a schematic block diagram illustrating a mobile terminal according to some other embodiments of the invention; Figure 5 is a schematic block diagram illustrating a wireless communication system according to some embodiments of the invention; Figure 6 is a flowchart illustrating operations for determining the location of a mobile terminal according to some embodiments of the invention; Figure 7 is a flowchart illustrating operations for determining the location of a mobile terminal according to some other embodiments of the invention; Figure 8 is a flowchart illustrating operations for determining the location of a mobile terminal according to some other embodiments of the invention; and Figure 9 is a flowchart illustrating operations for calibrating an acceleration measurement circuit according to some embodiments of the invention. DETAILED DESCRIPTION The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. However, this invention should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. As used herein the term "comprising" or "comprises" is open-ended, and includes one or more stated elements, steps and/or functions without precluding one or more unstated elements, steps and/or functions. As used herein the term "and/or" includes any and all combinations of one or more of the associated listed items. Embodiments according to the present invention are described with reference to block diagrams and/or operational illustrations of methods, mobile terminals, and mines, buildings or other enclosed areas. The term "satellite", as used herein, is intended to include pseudolites or equivalents of pseudolites, and the term GPS signals, as used herein, is intended to include GPS-like signals from pseudolites or equivalents of pseudolites. Also, while the following discussion references the United States GPS system, various embodiments herein can be applicable to similar satellite positioning systems, such as the GLONASS system or GALILEO system. The term "GPS", as used herein, includes such alternative satellite positioning systems, including the GLONASS system and the GALILEO system. Thus, the term "GPS signals" can include signals from such alternative satellite positioning systems. Figure 3 is a schematic block diagram of a mobile terminal 300 according to some embodiments of the invention. The mobile terminal includes a receiver 310, an acceleration measurement circuit 320 and a location determination circuit 330. The receiver 310 receives wireless communication signals, which may be from a satellite and/or one or more terrestrial transmitters. For example, the wireless communication signals may be GPS signals, cellular signals, Wide Area Network signals, and/or wireless local area network signals. The Wide Area Network signals may be, for example, digital TV signals from a plurality of broadcast towers whose locations are known to, or can be determined by, the mobile terminal 300. The acceleration measurement circuit 320 generates acceleration information that is based on acceleration of the mobile terminal 300. The location determination circuit 330 determines a location of the mobile terminal 300 based on acceleration information from the acceleration measurement circuit 320. A first location of the mobile terminal 300 may be defined in the location determination circuit 330, for example, by a user designating a present location of the mobile terminal 300 and/or the first location may be determined by the location determination circuit 330 based on the received wireless communication signals. The location determination circuit 330 then determines a distance that it has moved from the first location based on the acceleration information. The determined distance can indicate how far the mobile terminal 300 has moved in one or more directions (e.g., axes) relative to the first location. The mobile terminal 300 combines the determined distance with the first location to determine a second location, which may correspond to the present location of the mobile terminal 300. The mobile terminal 300 may thereby track its movement relative to a has moved at least a known threshold distance from a first location that has been defined and/or that is determined based on the received wireless communication signals. The known threshold distance may be based on the positioning accuracy that may be obtained using the received wireless communication signals. The location determination circuit 430 may determine that the mobile terminal 400 has moved at least the known threshold distance based on the received wireless communication signals and/or based on the acceleration information. The calibration circuit 430 may calibrate the acceleration measurement circuit 420 based on a temperature of the mobile terminal 400. A time for calibrating the acceleration measurement circuit 420 may be selected based on quality of location information from a received wireless signal, and which may be based a measurement of the strength of a received wireless signal. The calibration circuit 430 may calibrate the acceleration measurement circuit 420 by filtering (e.g., scaling, smoothing, and/or combining a known value / functional relationship with) the acceleration information to generate calibrated acceleration information from the acceleration information. Although the receiver 310, the acceleration measurement circuit 320, and the location determination circuit 330 are illustrated in Figure 3 as separate functional blocks, it is to be understood that, according to various other embodiments of the invention, two or more of them may be combined into a single device/circuit, and/or the functionality of one or more of them may be spread across more than one device/circuit. Similarly, the receiver 410, the acceleration measurement circuit 420, the location determination circuit 430, and/or the calibration circuit 440 shown in Figure 4 may be combined into a single device/circuit and/or may be spread across more than one device/circuit. Figure 5 is a schematic block diagram of a wireless communication system that includes a wireless terminal 500 that receives wireless communication signals from a cellular base station 502, GPS satellites 518 and/or a wireless local network 516. The cellular base station 502 is connected to a MTSO 506, which, in turn, is connected to a PSTN 512, and a network 514 (e.g., Internet). The mobile terminal 500 may communicate with the wireless local network 516 using a communication protocol that may include, but is not limited to, 802.1 la, 802.11b, 802.1 le, .802.11g, 802.11i, and/or other wireless local area network protocols. The wireless local network 516 may be connected to the network 514. division multiple access (CDMA), wideband-CDMA, CDMA2000, and Universal Mobile Telecommunications System (UMTS). Communication protocols as used herein may specify the information communicated, the timing, the frequency, the modulation, and/or the operations for setting-up and/or maintaining a communication connection. In some embodiments, the antennas 528 and 554 may be a single antenna. The acceleration measurement circuit 520 measures acceleration of the mobile terminal 500 and generates an acceleration signal that is indicative of the acceleration. Although only one acceleration measurement circuit 520 is shown, it is to be understood that the acceleration measurement circuit 520 may measure acceleration in one or more directions (e.g., axes) of movement, and/or that more than acceleration measurement circuit 520 may be used to measure acceleration. The processor 532 combines the acceleration signal with a time signal from the timing circuit 538 to determine the distance that the mobile terminal 500 has moved over an elapsed time. For example, the distance moved may be determined by integrating acceleration over an elapsed time. The acceleration information may be calibrated based on the wireless communication signals from the cellular base station 502, the GPS system 518 and/or the wireless local network 516. Calibration may include, for example, filtering (e.g., Kalman filtering) the acceleration information from the acceleration measurement circuit 520 by scaling and/or smoothing the acceleration information. The calibration may be based on, for example, a difference between a location of the mobile terminal that is determined based on wireless communication signals from the wireless location information system and a location that is determined based on the acceleration information. The accelerometer signals may be calibrated by, for example, using a clock to count time intervals (dt) and measure the average acceleration (vector A(i)) over the time intervals. The change in velocity (vector dV) in interval dt is A(i) times dt, which is dV. The change in position (vector dP) is then dV times dt or A(i) times dt and dt. Over time, the change in position P from position P1 to position P2 equals the sum of all dP(i) over the time used to move between PI and P2. If P2 does not match the observed positions P'2, obtained from the received wireless signal, then a 600). Location of the mobile terminal is then determined using the calibrated acceleration measurement circuit (Block 610). Figure 7 is a flowchart illustrating operations for determining a location of a mobile terminal according to some other embodiments of the invention. Acceleration of a mobile terminal is measured to generate acceleration information (Block 700). Location of the mobile terminal is then determined based on the acceleration information and based on wireless communication signals (Block 710). Further operations that may be used for determining location according to some embodiments of the present invention are illustrated by the flowchart shown in Figure 8. Referring to Figure 8, wireless communication signals are received (Block 800). A first location of the wireless terminal is determined from the received wireless communication signals and/or the first location is otherwise defined (Block 810). For example, the location determined could be a relative location with reference to an arbitrary first location. Acceleration information that is indicative of acceleration of the mobile terminal is measured using an acceleration measurement circuit (Block 820). The acceleration measurement circuit is adjusted based on temperature (Block 830). The acceleration measurement circuit may be adjusted, for example, to reduce or remove known temperature induced variation in its sensitivity. The distance that the mobile terminal has moved from the first location is determined based on the measured acceleration information and based on an elapsed time (Block 840). The determined distance is combined with (e.g., added to) the first location to determine a second location of the mobile terminal (Block 850). Figure 9 illustrates a flowchart of operations for calibrating an acceleration measurement circuit according to various embodiments of the invention. A first location of a wireless terminal is determined based on wireless communication signals and/or the first location is otherwise defined (Block 900). A distance that the mobile terminal has moved from the first location is determined based on acceleration information (Block 910). The determined distance is combined with the first location to determine a second location (Block 920). A decision is made as to whether the mobile terminal has moved at least a known threshold distance from the first location (Block 930). When the mobile terminal has moved at least the known threshold distance, a reference location of the mobile terminal is determined based on wireless communication signals (Block 940). A difference between the reference location and WE CLAIM: 1. A method for determining a location of a mobile terminal (300, 400), the method comprising: determining a first location of the mobile terminal (300, 400) based on wireless communication signals received by the mobile terminal (300,400); measuring acceleration of the mobile terminal (300, 400) to generate acceleration information; determining a distance that the mobile terminal (300, 400) has moved from the first location based on the acceleration information; combining the determined distance and the first location to determine a second location of the mobile terminal (300, 400); determining whether the mobile terminal (400) has moved at least a threshold distance from the first location; and responsive to determining that the mobile terminal (400) has moved at least the threshold distance from the first location determining a reference location of the mobile terminal (400) based on the wireless communication signals; and calibrating the acceleration information based on the second location and the reference location. 2. The method as claimed in claim 1, wherein the wireless communication signals comprise cellular signals. 3. The method as claimed in claim 1, wherein the wireless communication signals comprise Wide Area Network signals. 4. The method as claimed in claim 1, wherein determining a first location of the mobile terminal (300, 400) based on wireless communication signals comprises determining the first location without use of GPS signals. 5. The method as claimed in claim 2, wherein determining a first location of the mobile terminal (300, 400) based on wireless communication signals comprises determining the first location based by triangulation of cellular signals from a plurality of cellular transmitters. 6. The method as claimed in claim 3, wherein determining a first location of the mobile terminal (300, 400) based on wireless communication signals comprises triangulating the location of the mobile terminal (300, 400) based on Wide Area Network signals from a plurality of terrestrial wireless communication signal transmitters. 7. The method as claimed in claim 1, wherein determining a first location of the mobile terminal (300, 400) based on wireless communication signals comprises determining the first location based on wireless local network signals. 8. The method as claimed in claim 2, further comprising selecting a time for calibrating the acceleration information based on quality of the location information determined from the cellular signals. 9. The method as claimed in claim 1, further comprising: identifying a time indication in the cellular signals; calibrating a timing circuit (538) that is internal to the mobile terminal (500) based on the identified time indication; measuring an elapsed time based on the calibrated timing circuit (538); and determining the location of the mobile terminal (500) based on the acceleration information and based on the elapsed time. 10. The method as claimed in claim 1, further comprising compensating the acceleration information based on a temperature of the mobile terminal (300). 11. A mobile terminal (400) comprising: a receiver (410) that is adapted to receive wireless communication signals; an acceleration measurement circuit (420) that is adapted to generate acceleration information that is based on acceleration of the mobile terminal (400); a.location determination circuit (430) that is adapted to determine a first location of the mobile terminal (400) based on the wireless communication signals, is adapted to determine a distance that the mobile terminal (400) has moved from the first location based on the acceleration information, is adapted to combine the determined distance and the first location to determine a second location of the mobile terminal (400), is adapted to determine whether the mobile terminal (400) has moved at least a threshold distance from the first location and is adapted to determine a reference location of the mobile terminal (400) based on the wireless communication signals in response to a determination that the mobile terminal (400) has moved at least the threshold distance from the first location; and a calibration circuit (440) that is adapted to calibrate the acceleration measurement circuit (420) based on the second location and the reference location in response to the determination that the mobile terminal (400) has moved at least the threshold distance from the first location. 12. The mobile terminal (400) as claimed in claim 11, wherein the location determination circuit (430) is adapted to determine the first location of the mobile terminal (400) without use of GPS signals. 13. The mobile terminal (400) as claimed in claim 11 wherein the location determination circuit (430) is adapted to determine the first location of the mobile terminal (400) based on triangulation of cellular signals from a plurality of cellular transmitters. 14. The mobile terminal (400) as claimed in claim 11, wherein the location determination circuit (430) is adapted to determine the first location of the mobile terminal (400) based on triangulation of Wide Area network signals from a plurality of terrestrial wireless communication signal transmitters. 15. The mobile terminal (400) as claimed in claim 11, wherein the wireless communication signals comprise cellular signals and wherein the calibration circuit (440) is adapted to select a time for calibrating the acceleration measurement circuit (420) based on quality of the location information determined from the cellular signals. 16. The mobile terminal (400) as claimed in claim 11, wherein the calibration circuit (440) is adapted to calibrate the acceleration measurement circuit (420) based on a temperature of the mobile terminal (400).

Documents:

4404-DELNP-2006-Abstract -(07-03-2012).pdf

4404-delnp-2006-abstract.pdf

4404-delnp-2006-assignment.pdf

4404-DELNP-2006-Claims-(07-03-2012).pdf

4404-delnp-2006-claims.pdf

4404-DELNP-2006-Correspondence Others-(05-12-2011).pdf

4404-DELNP-2006-Correspondence Others-(07-03-2012).pdf

4404-delnp-2006-correspondence-others-1.pdf

4404-delnp-2006-correspondence-others.pdf

4404-delnp-2006-description(complete).pdf

4404-DELNP-2006-Drawings-(07-03-2012).pdf

4404-delnp-2006-drawings.pdf

4404-DELNP-2006-Form-1-(07-03-2012).pdf

4404-delnp-2006-form-1.pdf

4404-delnp-2006-form-18.pdf

4404-DELNP-2006-Form-2-(07-03-2012).pdf

4404-delnp-2006-form-2.pdf

4404-DELNP-2006-Form-3-(05-12-2011).pdf

4404-delnp-2006-form-3.pdf

4404-delnp-2006-form-5.pdf

4404-DELNP-2006-GPA-(07-03-2012).pdf

4404-delnp-2006-gpa.pdf

4404-delnp-2006-pct-101.pdf

4404-delnp-2006-pct-210.pdf

4404-delnp-2006-pct-220.pdf

4404-delnp-2006-pct-237.pdf

4404-delnp-2006-pct-401.pdf

4404-delnp-2006-pct-409.pdf

4404-delnp-2006-pct-416.pdf

4404-DELNP-2006-Petition-(07-03-2012).pdf

4404-DELNP-2006-Petition-137-(05-12-2011).pdf