(12) United States Patent
`Alberth, Jr. et al.
`
`USOO6438381B1
`(10) Patent No.:
`US 6,438,381 B1
`(45) Date of Patent:
`Aug. 20, 2002
`
`(54) METHOD AND APPARATUS FOR LOCATION
`DETERMINATION OF A CELLULAR
`TELEPHONE
`
`(75) Inventors: William P. Alberth, Jr., Crystal Lake,
`Michael Kotzin, Buffalo Grove, both of
`IL (US
`(US)
`(73) Assignee: Motorola, Inc., Schaumburg, IL (US)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/590,215
`22) Filled:
`8, 2000
`(22) File
`Jun. 8,
`(51) Int. Cl." .................................................. H04Q 7/20
`(52) U.S. Cl. ....................... 455/456; 455/343; 455/552;
`342/357.06
`(58) Field of Search ................................. 455/343, 456,
`455/552, 553, 574, 12.1, 427, 67.1, 226.1,
`226.2; 342/357.01, 357,06,357.09; 370/311,
`320,335
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`5,448,773 A * 9/1995 McBurney et al. ......... 455/343
`5.535,432 A
`7/1996 Dent ......................... 455/12.1
`
`5,604,765 A * 2/1997 Bruno et al................. 455/343
`5,949,812 A * 9/1999 Turney et al. .............. 455/574
`6,021,330 A 2/2000 Vannucci .................... 455/456
`6,028,887 A * 2/2000 Harrison et al.
`... 342/357.06
`6,133,871 A * 10/2000 Krasner ................. 342/357.06
`FOREIGN PATENT DOCUMENTS
`WO OO/13034
`3/2000
`WO
`* cited by examiner
`Primary Examiner Nay Maung
`Assistant Examiner-Quochien B. Vuong
`(74) Attorney, Agent, or Firm-Paul J. Bartusiak, Randall
`S. Vaas
`ABSTRACT
`(57)
`Amethod of making a geographic location determination via
`a cellular telephone in Signal communication with a base
`Station. The mobile Station first attempts to detect a position
`location Signal. Upon determining that the position location
`signal is insufficient to use in a position location calculation,
`the mobile Station deactivates at least a portion of a receiver.
`The mobile Station receives a cellular communication Signal
`and measures a Signal quality of the cellular communication
`Signal. Responsive to the Signal quality improving by a
`predetermined amount, the mobile Station reactivates the
`receiver portion and re-attempts to detect the position loca
`tion Signal.
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`23 Claims, 2 Drawing Sheets
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`SYNTHESIZER
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`SEARCHER
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`U.S. Patent
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`Sheet 1 of 2
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`U.S. Patent
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`Aug. 20, 2002
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`US 6,438,381 B1
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`1
`METHOD AND APPARATUS FOR LOCATION
`DETERMINATION OF A CELLULAR
`TELEPHONE
`
`FIELD OF THE INVENTION
`This invention generally relates to geographic location
`determination. More Specifically, this invention relates to
`geographic location determination via a cellular telephone.
`BACKGROUND OF THE INVENTION
`In the near future cellular telephones will have the capa
`bility to make a geographic location determination. Many
`methods have been proposed to implement the location
`determination feature in a cellular telephone. One method is
`to integrate a Global Positioning System (GPS) receiver in
`the cellular telephone. The GPS receiver periodically
`receives timing Signals from GPS Satellites and processes
`the timing Signals to make a location determination.
`Under various conditions, GPS receivers have significant
`trouble receiving the necessary Satellite timing Signals. For
`example, if a user is inside a building, the GPS Signals may
`not be strong enough for the user's GPS receiver to detect
`the Signals. The GPS signals may become even weaker (e.g.
`more difficult to detect) as the cellular telephone is deeper
`within a building and away from any windows. In this
`situation, the cellular telephone GPS receiver would con
`tinually check for the GPS signals, and this continuous
`“checking can Significantly drain the cellular telephone
`battery. The same problem may be encountered if other
`position location technology (e.g. triangulation) is
`employed. Therefore, there is a need for a method and
`apparatus for making location measurements via a cellular
`telephone without unnecessarily draining the battery power
`of the cellular telephone.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a System diagram incorporating a cellular
`communication network and a global positioning System
`(GPS) satellite for position location determination; and
`FIG. 2 shows a block diagram of an exemplary embodi
`ment of a mobile Station.
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`and incorporated by reference. Additionally, the communi
`cation network 2 can comprise a plurality of communication
`technologies, such as both CDMA and TDMA.
`Location determination technology is employed to allow
`for the calculation of the geographic location of the mobile
`station 4. Moreover, the hardware configuration of the
`mobile Station 4 depends upon the type of location deter
`mination System deployed.
`In the illustrated embodiment, the mobile station 4
`employs a global positioning System (GPS) receiver for
`communication with the GPS satellites 18. The mobile
`Station 4 employs a first antenna 6 for communication with
`the cellular communication network 2 and a Second antenna
`8 for communication with the GPS satellites 18.
`Alternatively, the mobile Station 4 may utilize a single
`antenna for detecting both position location Signals and
`cellular communication Signals.
`For what is commonly referred to as autonomous GPS
`position location, the mobile Station 4 acquires and measures
`GPS satellite signals without the aid of the cellular commu
`nication network 2. In an alternate embodiment, the cellular
`communication network 2 employs network assisted GPS,
`wherein the cellular communication network 2 provides
`information to the mobile Station 4 to aid in acquiring the
`GPS satellite signals as is known in the art.
`In another alternate embodiment, the mobile station 4 is
`equipped to receive and process downlink Signals from the
`plurality of base Stations to aid in location determination of
`the mobile station 4; this is commonly known as forward
`link triangulation. Thus, the mobile Station 4 processes
`multiple communication signals from multiple base Stations
`and determines the arrival times for each of the communi
`cation signals as part of the position determination as is
`known in the art.
`FIG. 2 shows a block diagram of an exemplary embodi
`ment of the mobile station 4. The mobile station 4 is
`configured to receive and transmit spread Spectrum commu
`nication signals to communicate with a plurality of base
`stations. The base stations (FIG. 1) transmit various spread
`Spectrum Signals, Such as an information Signal on a traffic
`channel, to the mobile station 4. In addition to traffic
`channels, the base Stations broadcast other communication
`Signals. Such as a spread Spectrum pilot signal Over a pilot
`channel, a Synchronization signal over a Synchronization
`channel, and a paging Signal Over a paging channel. The
`pilot channel is commonly received by all mobile Stations
`within range and is used by the mobile station 4 for
`identifying the presence of a CDMA System, initial System
`acquisition, idle mode hand-off, identification of initial and
`delayed rays of communicating and interfering base Stations,
`and for coherent demodulation of the Synchronization,
`paging, and traffic channels. The Synchronization channel is
`used for Synchronizing mobile Station timing to base Station
`timing. The paging channel is used for Sending paging
`information from the first base station 10 to mobile stations
`including mobile Station 4. Signals transmitted by the base
`Stations are spread using a pseudorandom noise (PN)
`Sequence as is known in the art.
`In alternate embodiments, the pilot Signals comprise
`multiple pilot Signals transmitted over a plurality of chan
`nels. Some of the pilot Signals can be used, for example, for
`initial acquisition and Signal Strength determination. Other
`of the pilot Signals can be used for Storing group
`information, Such as a group of base Station identities.
`The mobile Station 4 comprises a first antenna 6, a
`conventional transmitter 30, cellular receiver 31, a synthe
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`FIG. 1 shows a System diagram of a cellular communi
`cation network 2 incorporating global positioning System
`(GPS) satellites, here represented by GPS satellite 18, for
`position location determination. The cellular communication
`network 2 includes a plurality of base Stations, including first
`base Station 10, Second base Station 12, and third base Station
`14. A base station controller 16 is coupled to the plurality of
`base Stations generally for controlling operation of the
`cellular communication network 2 as is known in the art.
`Mobile Station 4 communicates to another destination via at
`least one of the plurality of base Stations.
`The cellular communication network 2 can operate using
`any of Several kinds of communication protocols, Such as
`code division multiple access (CDMA) technology, time
`division multiple access (TDMA) technology, or frequency
`division multiple access (FDMA) technology as is known in
`the art. In the illustrated embodiment, the cellular commu
`nication network 2 operates via CDMA air interface Stan
`dard as outlined in TIA/EIA Interim Standard IS-95 entitled
`“Mobile Station-Base Station Compatibility Standard for
`Dual-Mode Wideband Spread Spectrum Cellular System”
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`sizer 38, and a controller 40. Conventional duplexer 7 allows
`for Simultaneous transmission and reception as is known in
`the art. The controller 40 comprises a microprocessor to
`control operation of the mobile station 4. The controller may
`alternatively, or in addition, comprise any of logic circuitry,
`timing and clock circuitry, a digital Signal processor, and
`microprocessor as is known in the art. This additional
`circuitry interconnection to other blocks of the mobile
`Station 4, as well as the user interface (microphone, speaker,
`etc.) are not shown in FIG. 2 So as to not unduly complicate
`the drawing figure.
`The cellular receiver 31 comprises an analog front end 32,
`a Searcher receiver 34, and a rake receiver 36. The antenna
`6 detects RF signals from the first base station 10 and from
`other base stations in the vicinity. Some of the received RF
`Signals are direct line of Sight rays transmitted by the base
`station. Other received RF signals are reflected or multi-path
`rays and are therefore delayed in time relative to the line of
`Sight rayS. Received RF signals are converted to electrical
`Signals by the antenna 6 and provided to the analog front end
`32. The analog front end 32 performs functions such as
`filtering, automatic gain control, and conversion of Signals to
`baseband Signals as is known in the art. The analog baseband
`Signals are converted to Streams of digital data for further
`processing.
`Generally, the Searcher receiver 34 detects pilot Signals
`from the streams of digital data. The searcher receiver 34
`despreads the pilot Signals using a correlator and PN codes
`generated in the mobile Station 4 as is known in the art. After
`this despreading, the Signal values for each chip period are
`accumulated over a pre-Selected interval of time, and the
`correlation energy is compared against a threshold level.
`Correlation energies exceeding the threshold level generally
`indicate a Suitable pilot Signal ray that can be used for pilot
`Signal timing Synchronization.
`Once a Suitable ray is identified and timing Synchroniza
`tion is accomplished, a demodulation branch of the RAKE
`receiver 36 is assigned to that signal path. The mobile Station
`4 can then demodulate information signals as is known in the
`art.
`In the illustrated embodiment the mobile station 4 utilizes
`GPS Signaling for geographic location analysis and thus
`employs a conventional GPS receiver 42. The second
`antenna 8 detects location information signals from the GPS
`satellites 18 (FIG. 1), and the GPS signals are processed by
`the conventional GPS receiver 42 as is known in the art and
`then forwarded to the controller 40. The GPS receiver 42 and
`the cellular receiver 31 may alternatively share at least Some
`circuitry to reduce the Size and cost of the mobile Station 4.
`The combined GPS receiver and cellular receiver may then
`be generally referred to as a mobile Station receiver.
`In operation, the controller 40 periodically activates the
`GPS receiver 42 to detect and process location signaling
`transmitted by the GPS satellites 18 (FIG. 1). For example,
`the GPS receiver can periodically activate at a rate of
`Substantially every five Seconds, thirty Seconds or minute.
`This periodic activation rate is referred to as a first rate, and
`other frequencies of activation may be chosen for the first
`rate as necessary. The more frequently the activation, the
`more up-to-date the position location information will be.
`The tradeoff for higher frequencies for the first rate of
`activation is battery drain.
`After detecting the position location signals, the GPS
`receiver process the Signals by performing conventional
`GPS receiver functions Such as frequency conversion,
`filtering, and demodulation. One particular analysis in which
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`the GPS receiver is involved is the determination as to
`whether the position location Signals are even Sufficient for
`a position location calculation. For example, the GPS
`receiver 42 will determine the Signal Strength of the received
`position location Signals, and if the Signals are below a
`predetermined threshold, then the position location signals
`are too weak to process. In the illustrated embodiment, the
`GPS receiver 42 sensitivity is -155 dBm. The GPS receiver
`42 can perform the received signal Strength measurement, or
`alternatively the GPS receiver 42 can forward a signal to
`another portion of the mobile station 4 (such as the cellular
`receiver 31 and/or the controller 40) for the received signal
`Strength determination.
`Further, the Signal Strength of the position location signals
`can be determined in any number of conventional methods.
`For example, and intermediate analog signal can be utilized
`for the calculation, or a digitized version of the baseband
`Signal can be utilized. Other means for determining the
`quality of the link between the GPS receiver 42 and the GPS
`satellites 18 (FIG. 1) can alternatively be employed. For
`example, the bit error rate or frame erasure rate resulting
`from processing the position location signals can be used as
`a criteria for determining whether the received position
`location signals are Suitable for processing.
`If the position location signals are Suitable for processing,
`normal operation continues and the position Signals are used
`for geographic location as is known in the art. The GPS
`receiver 42 continues to periodically activate at the first
`predetermined rate to detect and process new position loca
`tion Signaling.
`If the position location Signals are not Suitable for pro
`cessing (e.g. too weak), the controller 40 decreases the
`frequency at which the GPS receiver 42 periodically activate
`to detect position location signaling. This is done to Save
`battery power. The position location signals may be too
`weak based upon the position of the mobile station. For
`example, if the user is within a building, the Satellite signals
`may not Suitably penetrate the building for detection. If the
`user is deep within a building away from any windows, the
`Satellite Signals may be even weaker.
`Thus, the controller 40 will decrease the frequency of
`GPS receiver 42 activation to a second, predetermined rate.
`This Second predetermined rate can be on the order of every
`five minutes, ten minutes, twenty minutes, or more. In the
`illustrated embodiment, the rate of activation is reduced to
`once every twenty minutes. Once again, the rate of activa
`tion is a design tradeoff between how current the geographic
`location information is and battery conservation.
`During each twenty minute period, at least a portion of the
`receiver, here GPS receiver 42, is deactivated to conserve
`power. However, the quality of the communication link
`between the mobile station 4 and the cellular base stations
`(FIG. 1) is constantly monitored. The controller 40 then
`reactivates the GPS receiver 42 responsive to the quality of
`the cellular communication link improving by a predeter
`mined amount. The GPS receiver then attempts to detect
`position location signaling.
`In determining whether the quality of the communication
`link has improved by a predetermined amount, the mobile
`Station can use received signal Strength of the received
`cellular Signal. Alternatively, the mobile Station can use bit
`error rate or frame erasure rate as the criteria.
`For example, in its determination of the quality of the
`communication link, the mobile Station makes Several Signal
`measurements. If received signal Strength is used as the
`determination factor, the mobile Station 4 makes a first
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`received Signal Strength measurement of the cellular com
`munication Signal over a first predetermined period of time
`to form a long term Signal Strength. In the illustrated
`embodiment, the first predetermined period of time is one
`minute. This long term Signal Strength measurement is
`performed after the controller 40 causes the GPS receiver 42
`to decrease its frequency of activation. The long term Signal
`Strength actually comprises an average of twenty signal
`Strength measurements made within the first predetermined
`period of time. Each of the twenty signal Strength measure
`ments is over a hundred msec time period.
`After the mobile Station 4 makes the first nineteen Signal
`Strength measurements for the long term Signal Strength, the
`last one hundred msec measurement is made, and the long
`term Signal Strength comprises the average of the twenty
`measurements. In addition, the mobile Station makes a
`Second received signal Strength measurement over a Second
`predetermined period of time to determine a short term
`Signal Strength. The Second predetermined period of time is
`shorter than the first predetermined period of time. In the
`illustrated embodiment, the Short term Signal Strength com
`prises the twentieth Signal Strength measurement that was
`made for the long term Signal Strength. The short term Signal
`Strength is then compared to the long term Signal Strength.
`Thus, if the frequency of activation of the GPS receiver 42
`is decreased to once every twenty minutes, the short term
`Signal Strength can be calculated and compared to the long
`term Signal Strength once every minute. It will be obvious to
`those skilled in the art that other time periods may be chosen
`for the Short and long term Signal Strength measurements,
`and other methods can be used to calculate the short and
`long term Signal Strengths without deviating from the Spirit
`of the invention.
`If the short term Signal Strength improves in comparison
`to the long term Signal Strength by Some predetermined
`amount (e.g. 20 dB), the controller 40 activates the GPS
`receiver 42 to attempt to detect the position location signal
`ing. If the position Signals are of Sufficient Strength, the
`controller 40 increases the frequency of activating the GPS
`receiver 42 back to the first predetermined rate and normal
`operation continues. If the short term Signal Strength is still
`too weak for processing, the GPS receiver 42 deactivates
`and operation in the low power mode continues- the con
`troller continues to activate the GPS receiver 42 at the
`decreased frequency.
`The controller can update the long term Signal Strength
`measurement to indicate a new baseline value in a variety of
`ways. For example, a new long term Signal Strength can be
`calculated for each one minute period. Alternatively, the
`long term Signal Strength value can be a long term moving
`average value in which measurements from different one
`minute periods (or other time periods) are considered.
`The long term and short term Signal Strength measure
`ments are based upon an analog version of the received
`Signal produced by the receiver analog front end at port as
`is known in the art. Alternatively, a digitized version of the
`baseband Signal appearing at port 44 may be utilized for
`Signal Strength calculation. Still further, the Signal Strength
`determination can be made after despreading the received
`Signal. Thus, a received pilot Signal can be despread by the
`Searcher receiver 34 as is known in the art, and Signal
`Strengths can then be determined.
`In alternate embodiments, other means are employed to
`determine a quality of the communication link between the
`mobile station 4 and at least one cellular base station (FIG.
`1). For example, after the Searcher receiver 34 despreads a
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`received pilot Signal, a long term bit error rate or frame
`erasure rate can be established as a baseline. The short term
`bit error rate (or frame erasure rate) is then periodically
`measured at a rate discussed above to determine whether the
`quality of the cellular communication link has Sufficiently
`improved to activate the GPS receiver 42 prior to the next
`prescribed wakeup time.
`The use of a separate GPS receiver 42 provides the mobile
`station with what may be referred to as autonomous GPS,
`wherein the mobile Station interacts principally with the
`GPS satellites 18 (FIG. 1) for location determination.
`Alternatively, the base Stations of the cellular communica
`tion network 2 (FIG.1) may participate in the mobile station
`location determination using GPS as is known in the art, and
`this is referred to as network assisted GPS. Still further,
`forward link triangulation may be employed to determine
`the latitude and longitude information of the mobile Station
`as is known in the art. The position location receiver portion
`would then be periodically activated to detect the base
`Station triangulation Signals. The cellular base Stations may
`transmit the triangulation Signals differently than the regular
`cellular communication Signals So that the Spirit of this
`invention may still be faithfully employed. For example,
`The triangulation signals may be transmitted at a higher
`power than the cellular communication Signals. The initial
`decision as to whether to decrease the rate of activation of
`the GPS receiver is thus based upon analysis of the quality
`of the triangulation signals. Measurement of the long term
`and Short term Signal quality is then based upon the cellular
`communication signals.
`Decreasing the rate of GPS receiver activation upon
`determining that the position location Signals are not Suffi
`cient for location determination calculation conserves
`mobile station battery power. In addition, changing the rate
`of activation of the GPS receiver based upon the actual
`position location signaling rather than, Say, the Strength of
`the cellular communication Signals provides for a more
`reliable determination criteria. This is because the cellular
`communication Signals are largely uncorrelated with GPS
`signals transmitted by GPS satellites. Thus, a user can be
`deep within a building and away from a window so that GPS
`Signals are weak or virtually undetectable. There may be,
`however, a picocell cellular base Station transmitter deep
`within the building. Basing the initial decision as to whether
`to decrease the rate of activation of the GPS receiver on the
`quality of the cellular communication link could thus result
`in erroneous decisions.
`The previous description of the preferred embodiments
`are provided to enable any perSon Skilled in the art to
`practice the preferred embodiments. Various modifications
`to these embodiments will be readily apparent to those
`skilled in the art, and the generic principles defined herein
`may be applied to other embodiments without the use of the
`inventive faculty.
`We claim:
`1. A method of making a geographic location determina
`tion via a cellular telephone in Signal communication with a
`base Station, the method comprising:
`attempting to detect a position location signal;
`determining that a signal Strength of the position location
`Signal is too weak to use in a position location calcu
`lation;
`deactivating at least a portion of a global positioning
`System (GPS) receiver responsive to determining;
`receiving a cellular communication signal;
`measuring a signal Strength of a cellular communication
`Signal;
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`reactivating the at least a portion of the GPS receiver
`responsive to the Signal Strength of the cellular com
`munication signal increasing by a predetermined
`amount; and
`re-attempting to detect the position location signal respon
`Sive to reactivating.
`2. The method of claim 1, wherein the Step of measuring
`comprises:
`making a first received Signal Strength measurement of the
`cellular communication Signal over a first predeter
`mined period of time to form a long term Signal
`Strength; and
`making a Second received signal Strength measurement
`over a Second predetermined period of time to deter
`mine a short term Signal Strength, the Second predeter
`mined period of time shorter than the first predeter
`mined period of time.
`3. The method of claim 2 wherein the step of reactivating
`responsive to the Signal Strength increasing by the predeter
`mined amount includes determining whether the short term
`Signal Strength is greater than the log term Signal Strength by
`a predetermined amount.
`4. The method of claim 3 further comprising calculating
`the geographic location of the cellular telephone using the
`position location signal.
`5. An apparatus for initiating a location determination via
`a cellular telephone,
`the apparatus comprising:
`a receiver for processing cellular communication Sig
`nals and global positioning System (GPS) signals;
`and
`a controller coupled to the receiver, the controller for
`causing at least a portion of the receiver to deactivate
`upon determining that received GPS Signals are too
`weak to process, the controller causing the at least a
`portion of the receiver to reactivate and attempt to
`receive GPS Signals upon determining that a strength
`of the cellular communication Signals have increased
`by a predetermined amount.
`6. The apparatus as in claim 5 wherein:
`the receiver makes a first received Signal Strength mea
`Surement using the cellular communication signals
`over a first predetermined period of time to determine
`a long term Signal Strength, and
`responsive to the at least a portion of the receiver
`deactivating, the receiver periodically makes a Second
`received signal Strength measurement based on the
`cellular communication signals and over a Second
`predetermined period of time to determine a short term
`Signal Strength for each of the Second received signal
`Strength measurements, the Second predetermined
`period of time less than the first predetermined period
`of time, the controller causing the at least a portion of
`the receiver to re-activate and attempt to receive a GPS
`Signal when the Short term Signal Strength is greater
`than the long term Signal Strength by a predetermined
`amount.
`7. The apparatus as in claim 6, wherein if after a prede
`termined amount of time elapses and the short term Signal
`Strength is not greater than the long term Signal Strength, the
`controller causes the at least a portion of the receiver to
`re-activate and attempt to receive a GPS Signal.
`8. The apparatus as in claim 5 wherein the at least a
`portion of the receiver comprises GPS receiver circuitry.
`9. The apparatus as in claim 5 wherein the receiver
`comprises a GPS receiver and a cellular communication
`receiver.
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`10. The apparatus as in claim 9 wherein the GPS receiver
`shares at least a portion of the cellular communication
`receiver.
`11. A method of determining when to activate a receiver
`in a cellular telephone to
`attempt to receive Signals useful for a geographic location
`determination, the method comprising:
`monitoring, over a first period of time and over a
`Second period of time, a quality of a communication
`link between the cellular telephone and at least one
`base Station, the first period of time greater in dura
`tion than the Second period of time, and
`attempting to receive position location Signaling when
`the quality of the communication link over the
`Second period of time improves over the quality of
`the communication link over the first period of time
`by a predetermined amount.
`12. The method of claim 11 wherein the quality of the
`communication link is indicated by any of bit error rate,
`frame erasure rate, and received signal Strength.
`13. In a code division multiple access (CDMA) cellular
`telephone in Signal communication with at least one base
`Station, an apparatus for geographic location analysis, the
`apparatus comprising:
`a Searcher receiver for measuring Signal Strength of a
`received pilot Signal;
`a global positioning System (GPS) receiver for periodi
`cally activating at a first predetermined rate to attempt
`to receive position location Signaling at; and
`a controller coupled to the searcher receiver and the GPS
`receiver, the controller for causing the first predeter
`mined rate to decrease in frequency to a Second pre
`determined rate responsive to the GPS receiver failing
`in an attempt to receive position location Signaling,
`wherein the controller causes the Searcher receiver to
`measure, over a first predetermined period of time and
`a Second predetermined period of time, a quality of a
`communication link between the CDMA cellular tele
`phone and the at least one base Station, the first prede
`termined period of time greater in duration than the
`Second predetermined period of time, the controller for
`causing the GPS receiver to attempt to receive the
`position location signaling when the quality of the
`communication link over the Second predetermined
`period of time improves compared to the quality of the
`communication link Over the first predetermined period
`of time by a predetermined amount.
`14. The apparatus as in claim 13 wherein the quality of the
`communication link comprises the Signal Strength of the
`received pilot Signal.
`15. The apparatus as in claim 14 wherein the controller
`causes the GPS receiver to Switch from the second prede
`termined rate to the first predetermined rate responsive to the
`GPS receiver receiving position location Signaling of Suffi
`cient Signal Strength.
`16. A method of making a geographic location determi
`nation via a cellular telephone in Signal communication with
`a base Station, the method comprising:
`attempting to detect a position location signal;
`determining that the position location signal is insufficient
`for a position location calculation;
`deactivating at least a portion of a global positioning
`System (GPS) receiver responsive to determining;
`receiving a cellular communication signal;
`measuring a signal Strength of the cellular communication
`Signal;
`
`IPR2020-01192
`Apple EX1076 Page 7
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`US 6,438,381 B1
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`reactivating the at least a portion of the GPS receiver
`responsive to the Signal Strength of the cellular com
`munication signal increasing by a predetermined
`amount; and
`re-attempting to detect the position location signal respon
`Sive to reactivating.
`17. The method as in claim 16 wherein the step of
`reactivating includes detecting that a bit error rate exceeded
`a predetermined level.
`18. A method of making a geographic location determi
`nation via a cellular telephone in Signal communication with
`a base Station, the method comprising:
`attempting to detect a position location signaling,
`determining that the position location Signaling is insuf
`ficient for a position location calculation;
`Suspending the Step of attempting responsiv