WO2002098024A1 - Methods and apparatuses for using mobile gps stations to synchronize basestations - Google Patents
Methods and apparatuses for using mobile gps stations to synchronize basestations Download PDFInfo
- Publication number
- WO2002098024A1 WO2002098024A1 PCT/US2001/017113 US0117113W WO02098024A1 WO 2002098024 A1 WO2002098024 A1 WO 2002098024A1 US 0117113 W US0117113 W US 0117113W WO 02098024 A1 WO02098024 A1 WO 02098024A1
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- WIPO (PCT)
- Prior art keywords
- time
- basestation
- station
- mobile
- mobile cellular
- Prior art date
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2662—Arrangements for Wireless System Synchronisation
- H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
- H04B7/2678—Time synchronisation
- H04B7/2687—Inter base stations synchronisation
- H04B7/2693—Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
Definitions
- the present invention relates to the field of cellular communication systems, and particularly those systems where the location of a mobile cellular communication station (MS) is determined.
- MS mobile cellular communication station
- TDO A Time Difference of Arrival
- a location server which computes the position of the mobile.
- TDO A Time Difference of Arrival
- the times-of-day at the various basestations need to be coordinated to provide accurate location.
- the position of the basestations needs to be known accurately.
- Figure 1 shows an example of a TDOA system where the times of reception (TR1, TR2 and TR3) of the same signal from the mobile cellular telephone 22 are measured at cellular basestations 12, 14 and 16 by a location server 24.
- the location server 24 is coupled to receive data from the basestations through the mobile switching center 18.
- the mobile switching center 18 provides signals (e.g. voice communications) to and from the land-line Public Switched Telephone System (PSTS) so that signals may be conveyed to and from the mobile telephone to other telephones (e.g. land-line phones on the PSTS or other mobile telephones).
- PSTS Public Switched Telephone System
- the location server may also communicate with the mobile switching center via a cellular link.
- the location server may also monitor emissions from several of the basestations in an effort to determine the relative timing of these emissions.
- An alternative method measures at the mobile the times of arrival of signals transmitted from each of several basestations.
- Figure 1 applies to this case if the arrows of TR1, TR2 and TR3 are reversed.
- This timing data may then be used to compute the position of the mobile.
- Such computation may be done at the mobile itself or at a location server, if the timing information so obtained by the mobile is transmitted to this server via the link.
- the basestation times-of-day must be coordinated and their location accurately assessed.
- the locations of the basestations are determined by standard surveying methods and may be stored in the basestation or at the server in some type of computer memory.
- a third method of doing position location utilizes in the mobile a receiver for the Global Position Satellite System (GPS) or other satellite positioning system (SPS).
- GPS Global Position Satellite System
- SPS satellite positioning system
- Such a method may be completely autonomous or may utilize the cellular network to provide assistance data or share in the position calculation. Examples of such a method are described in U.S. Patents No. 5,841,396; No. 5,945,944; and No. 5,812,087. As a shorthand, we call these various methods "SPS.”
- a combination of either the EOTD and TDO A and an SPS system is called a "hybrid" system.
- time coordination between the various cellular basestations is necessary for accurate position calculation of the mobile.
- the required time-of-day accuracy at the basestations depends upon details of the positioning method utilized.
- the round trip delay (RTD) is found for signals that are sent from the basestation to the mobile and then are returned.
- the round trip delay is found for signals that are sent from the mobile to the basestation and then returned.
- Each of these round trip times are divided by two to determine an estimate of the oneway time delay.
- LMU Location Measurement Unit
- TMU Timing Measurement Unit
- LMU's or TMU's observe the timing signals, such as framing markers, present within the cellular communication signals that are transmitted from the basestations and attempt to time-tag these timing signals with the local time found via a GPS set or other time determination device. Messages may then be sent to the basestations (or other infrastructure components), which allow these entities to keep track of elapsed time. Then, upon command, or periodically, special messages may be sent over the cellular network to mobiles served by the network indicating the time- of-day associated with the framing structure of the signal. This is particularly easy for a system such as GSM in which the total framing structure lasts over a period exceeding 3 hours. It is noted that the location measurement units may serve other purposes, such as acting as the location servers —that is, the LMU's may actually perform the time-of-arrival measurements from the mobiles in order to determine the positions of the mobiles.
- the location measurement units may serve other purposes, such as acting as the location servers — that is, the LMU's may actually
- LMU or TMU approach require the construction of new special fixed equipment at each basestation or at other sites within communication range of several basestations. This can lead to very high costs for installation and maintenance.
- the present invention provides various methods and apparatuses for synchronizing cellular basestations in a cellular network.
- One exemplary method performs time synchronization between at least two basestations, a first basestation and a second basestation, of a cellular communication system.
- a first time-of-day and a first location of a first mobile cellular station (MS) are determined from a first satellite positioning system (SPS) receiver which is co- located with the first mobile station (MS), and the first time-of-day and first location are transmitted by the first MS to a first basestation which determines a time-of-day of the first basestation from the first time-of-day and first location and from a known location of the first basestation.
- SPS satellite positioning system
- a second time-of-day and a second location of a second MS are determined from a second SPS receiver which is co-located with the second MS, and the second time-of-day and the second location are transmitted to a second basestation which determines a time-of-day of the second basestation from the second time-of-day and the second location and a known location of the second basestation. Since these mobile stations may be used for normal communication operations and are not necessarily fixed to a building or structure, their use for timing a network avoids the high cost of real estate to maintain fixed timing equipment. Other methods and apparatuses are also described for synchronizing basestations in a cellular network.
- Figure 1 shows an example of a prior art cellular network which determines the position of a mobile cellular device.
- Figure 2 shows an example of a mobile cellular communication station which may be used with the present invention and which includes a GPS receiver and a cellular communication transceiver.
- Figure 3 shows an example of a cellular basestation which may be used in various embodiments of the present invention.
- Figure 4 is a flowchart which shows one embodiment of a method according to the present invention.
- Figure 5A and 5B are flowcharts which show another embodiment of a method according to the present invention.
- Figure 6A shows two signals which are processed according to one exemplary method of the present invention.
- Figure 6B shows a representation of a signal at a basestation which shows how the basestation updates its clock to synchronize to other basestations.
- Figure 7 shows an example of a location server which may be used with certain embodiments of the present invention.
- Figure 8 shows the framing structure of GSM cellular signals. ⁇ HT ⁇ ATT FD DESCRIF ⁇ ON
- mobile communication stations are utilized that contain (or are coupled to) GPS receivers which determine both time-of-day and position.
- Figure 2 shows an example of such a mobile communication station.
- This GPS processing may be done in an autonomous mode, if the received signal is large, or with the aid of equipment in the infrastructure (servers) if the received signal-to- noise ratio is low.
- server equipment e.g. a location server shown in Figure 7 and described further below
- server equipment may also contribute to time-of-day and position determination in situations where improved performance is required (e.g. see U.S. Patents No. 5,945,944; No. 5,841,396; and No. 5,812,087).
- the time-of-day information from the GPS receiver may be used to time-tag the framing structure of the received communication (e.g. GSM) signal.
- GSM received communication
- the start of a particular GSM frame boundary which occurs every 4.6 milliseconds, may be used (see Figure 8).
- BS basestation
- the only major error left in transferring time is the propagation time from the mobile station (MS) (e.g. the mobile cellular communication station of Figure 2) to the BS.
- MS mobile station
- some other residual errors may remain, such as multipath delays and transit delays through the MS hardware, and methods for accounting for these residual errors are described below.
- a variety of methods may be used to estimate the aforementioned MS-to-BS propagation delay.
- a first and highly accurate approach can be employed when the MS and/or server have accurately determined the MS position via the GPS unit, and the BS location is precisely known (e.g. predetermined knowledge via survey).
- the propagation time may be determined (typically at some network entity) by dividing BS-MS range by the speed of light. Then the BS may determine the timing of its transmitted frame marker by simply subtracting the computed propagation time from the frame marker timing provided by the MS. This method is described further below in conjunction with Figures 5A, 5B, 6k and 6B.
- timing advance information already available within the MS and BS.
- the originally intended purpose of such information concerns intra-cell traffic coordination.
- timing-advance metrics can be manipulated in a straightforward manner to yield these MS-to-BS delay estimates.
- the accuracy afforded by such time alignment parameters is primarily determined by the time resolution of the communication bit intervals involved.
- propagation delay estimates accurate to within a few or several tens of microseconds.
- the basestations need not be synchronized to microsecond type accuracy but only to millisecond or even second type. For these scenarios, it may not be productive to compensate for the MS-to-BS delays since these small delays, on the order or tens of microseconds, are insignificant relative to the required timing accuracy.
- coarse time-of-day gotten at the MS may simply be used "as is” to time tag a signal from the BS. This is sent to the BS without the need for precision BS-MS ranging data. This situation is advantageous since GPS receivers are able to perform coarse time tagging at much lower signal levels than is possible for precision time tagging (e.g. see U.S. Patent No.
- FIG. 4 shows one exemplary method according to an embodiment of the present invention.
- the mobile cellular system determines a representation of its time-of-day at the mobile cellular communication station.
- GPS time may be obtained at the MS by reading GPS time off the GPS signals from the GPS satellites.
- a technique for determining time as described in U.S. Patent 5,812,087 may be utilized.
- a sample of the GPS signals received at the mobile may be transmitted to a location server or to some other server where this record is processed to determine the time of receipt as described in U.S. Patent 5,812,087.
- the time-of-day in operation 151 may alternatively be computed using one of the various methods described in co-pending Application Serial No. 09/062,232 which was filed April 16, 1998.
- the method shown in Figure 4 continues in operation 153 in which the propagation delay between the mobile cellular communication station and a cellular basestation, such as the cellular basestation shown in Figure 3, is determined.
- this operation is optional where the time determined in operation 151 has more error associated with it than the propagation delay.
- this propagation delay may be determined by determining the position of the mobile (by means of processing the GPS signals) and determining the position of the cellular basestation. The distance between these two positions divided by the speed of light will determine the propagation delay in operation 153.
- the time at the cellular basestation is determined from the time-of-day at the mobile (which was transmitted from the mobile cellular communication system) and from the propagation delay determined in operation 153 if this optional operation is utilized.
- Each cellular basestation in a network may employ this procedure in order to synchronize all the basestations relative to one time standard, such as GPS time.
- one time standard such as GPS time.
- improved triangulation, or ranging based upon the use of timing information sent between each of several basestations and a mobile system, may be obtained.
- Timing information may be made. These include allowing more efficient "handoff ' of a mobile's communications from one basestation to the next basestation, and permitting unambiguous time to be transmitted throughout the network for various purposes.
- FIGS 5A, 5B, 6k and 6B will now be described as a further example of an embodiment according to the present invention.
- This method may be performed with a mobile cellular communication system such as system 50 shown in Figure 2 and a cellular basestation 101 shown in Figure 3.
- the mobile cellular communication station 50 shown in Figure 2 includes a GPS receiver 52 having a GPS antenna 51 and a cellular communication transceiver 54 which includes an antenna 53.
- GPS receiver 52 may be contained within another chassis (and not integrated within the chassis which holds the components of the mobile station 50 such as the cellular communication transceiver 54) but is coupled to the cellular communication transceiver 54 and is in proximity to the transceiver 54; in this situation, the station 50 does not include a GPS receiver nor does it require one as long as the GPS receiver is coupled to and is co-located with the station 50.
- the GPS receiver 52 may be a conventional, hardware correlator based GPS receiver, or it may be a matched filter based GPS receiver, or it may be a GPS receiver which uses a buffer to store digitized GPS signals which are processed with fast convolutions, or it may be a GPS receiver as described in U.S. Patent 6,002,363 in which components of the GPS receiver are shared with components of the cellular communication transceiver (e.g. see Figure 7B of U.S. Patent 6,002,363 which is hereby incorporated herein by reference).
- the cellular communication transceiver 54 may be a modem cellular telephone which operates with any one of the well-known cellular standards including the GSM cellular standard, or the PDC communication standard, or the PHS communication standard, or the AMPS analog communication standard, or the North American IS-136 communication standard, or an unsynchronized wide band spread spectrum CDMA standard.
- the GPS receiver 52 is coupled to the cellular communication transceiver 54 to provide GPS time and position in one embodiment to the cellular communication transceiver 54 (which then transmits this information to a basestation). Further, the cellular communication transceiver 54 may provide assistance data such as Doppler information or time information to the GPS receiver as described in U.S. Patents 5,841,396 or 5,945,944.
- the coupling between the GPS receiver 52 and the cellular communication transceiver 54 may also be utilized to transmit a record to or from a cellular basestation for the purpose of matching that record with another record in order to determine the time at the GPS receiver as described in U.S. Patent 5,812,087.
- a location server is used to provide assistance data to the mobile cellular communication station for the purpose of determining the position or time at the system 50, or a location server shares in the processing of information (e.g. the location server determines time or the final position calculation of the mobile system 50)
- a location server such as that shown in Figure 7 and described further below is connected to a cellular basestation through a communication link to assist in the processing of data.
- the position of the mobile station is normally not fixed and is normally not predetermined.
- FIG 3 shows an example of a cellular basestation which may be used with various embodiments of the present invention.
- the basestation 101 includes a cellular transceiver 102 which has at least one antenna 102a for communicating signals to and from the mobile cellular communication station which are present in the area served by the cellular basestation 101.
- a mobile cellular communication station 50 may be one of the mobile stations served by the cellular basestation 101 depending upon the range of the signals typically transmitted by the mobile system 50.
- the cellular transceiver 102 may be a conventional transceiver used to transmit and receive cellular signals, such as a GSM cellular signal or a CDMA cellular signal.
- Clock 103 may be a conventional system clock which maintains time-of-day at the cellular basestation.
- Cellular basestation 101 typically also includes a network interface which transfers data to and from the cellular transceiver 102 in order to couple the cellular transceiver to a mobile switching center, as is well known in the art.
- the cellular basestation 101 may also include a digital processing system 105 which may be either positioned remotely relative to the cellular basestation or may be at the same site as the cellular basestation itself.
- the digital processing system 105 is coupled to the clock 103 in order to adjust or recalibrate the time of the clock to thereby synchronize the clock to other clocks in other cellular basestations according to methods of the present invention.
- the clock is highly stable but freerunning and it would affect network operation to actually alter the time strokes of the clock. Instead the time associated with the clock epochs can be adjusted. This is what is meant by "recalibrating.”
- the digital processing system 105 is also coupled to the network interface 104 in order to receive data or communications from the mobile switching center and to receive data from the cellular transceiver 102, such as time tagged frame markers transmitted from the mobile systems for the purpose of synchronizing the clock 103 to other clocks in other cellular basestations.
- the method shown in Figures 5k and SB begins in operation 201 when a cellular basestation transmits a cellular signal to a mobile cellular communication station.
- this signal may include a request for synchronization information from the mobile system in order to allow the cellular basestation to synchronize itself to other cellular basestations.
- the cellular basestation provides time tags or markers in its signal which is being transmitted to the mobile system. This marker may be a marker that is an inherent part of the framing structure of the signal.
- basestation 1 transmits a signal with a framing structure which includes markers Ml, M2, M3, M4, M5, M6, M7, M8 and M9 as shown in the signal 301 of Figure 6k.
- the mobile system in operation 203 of Figure 5A receives the cellular signal with the markers. Contemporaneously with the receipt of this cellular signal, the mobile station also receives a GPS signal from a GPS satellite which includes GPS time, as is well known in the art. The mobile station may then time tag the marker in the cellular signal received from the basestation with GPS time, which represents, in GPS time, a time when the marker was received at the mobile system.
- This is further shown in Figure 6A by the signal 303 which represents the signal received by the mobile 1 from base 1 as delayed by the propagation delay 307.
- a time tag 305 has been applied to the marker Ml and this represents the GPS time associated with the time of receipt of this marker at the mobile system.
- the mobile station in operation 205 determines its position contemporaneously with the time tagging of the marker in the cellular signal.
- the GPS receiver in the mobile station may determine its position either autonomously (e.g. a conventional hardware correlator based GPS receiver may by itself determine its position by reading ephemeris data from GPS satellites) or it may determine its position with the assistance of a server, such as the location server shown in Figure 7 which is coupled to the cellular network.
- the mobile station transmits to the cellular basestation its position (or pseudoranges to allow a location server to determine its position) and the GPS time associated with the marker, which was time tagged by the mobile station.
- the cellular basestation computes its time-of-day by using the position of the mobile and its known predetermined position to determine the propagation delay between the mobile and the basestation. This propagation delay is subtracted from the GPS time associated with the marker to determine GPS time at its transmitted marker.
- the basestation 1 receives the time tag TR1 from the mobile system.
- This time tag TR1 represents a GPS time which is associated with the marker Ml.
- the propagation delay 307 is subtracted from the GPS time TR1 to derive the time Tl which is associated with the marker Ml. That is, the time Tl is a time tag 309 associated with the marker Ml at the basestation.
- the current time at the basestation may then be updated by associating the GPS time in the tag 309 with the current frame M9 to produce current time 311 as shown in Figure 6B. That is, there is a known time relationship given the framing structure of the signal 301 between the marker M9 and the marker Ml in the signal 301. The difference in time between these two markers given the known framing structure is added to the time Tl to produce the current time 311. Thus, current time at the cellular basestation is updated from the GPS time which was associated with a transmitted marker which has been time tagged by the mobile. This is shown as operation 211 in Figure 5B.
- the last time that the clock at the cellular basestation was synchronized is optionally saved in order to determine when it is appropriate to update the clock in order to synchronize the clock with other clocks in other cellular basestations.
- the cellular basestation or a remote entity which assists the cellular basestation may determine when to synchronize again. For example, a set time of several minutes may automatically trigger another synchronization process. Alternatively, other techniques may be utilized to determine when to again synchronize the clock at the basestation to other clocks of other cellular basestations.
- Figure 7 shows an example of a location server 350 which may be used with various embodiments of the present invention. For example, as described in U.S. Patent No.
- the server may provide assistance data such as Doppler or other satellite assistance data to the GPS receiver in the mobile station 50 or the location server may perform the final position calculation rather than the mobile station 50 (after receiving pseudoranges or other data from which pseudoranges can be determined from the mobile) and then may forward this position determination to the basestation so that the basestation may calculate the propagation delay.
- the location server typically includes a data processing unit such as a computer system 351, a modem or other interface 352, a modem or other interface 353, a modem or other interface 354, a mass storage device 355 (e.g. for storing software and data), and optionally a GPS receiver 356.
- This location server 350 may be coupled to three different networks shown as networks 360, 362, and 364.
- the network 360 may include the cellular switching center or multiple cellular switching centers and/or the land based phone system switches; alternatively, the modem 353 may be coupled directly to cell sites such as the cellular basestation 101. It will be appreciated that multiple cellular basestations are typically arranged to cover a geographical area with radio coverage and these different basestations are coupled to at least one mobile switching center as is well known in the prior art (e.g. see Figure 1). Thus multiple instances of basestation 101 would be geographically distributed but coupled together by a mobile switching center.
- the network 362 may be a network of reference GPS receivers which provide differential GPS information and may also provide GPS ephemeris data for use in calculating the position of mobile systems. This network is coupled through the modem or other communication interface 354 to the data processing unit 351.
- the network 364 includes other computers or network components such as the data processing system 105 shown in Figure 3 (through an optional interconnection not shown in Figure 3). Also, the network 364 may include computer systems operated by emergency operators, such as the Public Safety Answering Points which respond to 911 telephone calls.
- emergency operators such as the Public Safety Answering Points which respond to 911 telephone calls.
- Various examples of methods for using the location server 350 have been described in numerous U.S. patents and patent applications including U.S. Patents 5,841,396; 5,874,914; 5,812,087; and U.S. Patent Application Serial No. 09/062,232, filed April 16, 1998, all of which are hereby incorporated herein by reference.
- the foregoing methods cletermine the effective time of transmission at the face of the BS antennas.
- the use of a large number of MS's may tend to reduce errors via averaging procedures. This assumes that system biases may be eliminated.
- Concerns about sufficient MS activity to support the timing e.g. early morning hours) could be ameliorated by placing MS's at various locations and making calls periodically.
- Typical timing errors due to the GPS processing at a single MS might be on the order of 10-30 nanoseconds. Thus, other sources of error, such as multipath may dominate.
- the stability of the BS oscillator will affect how often timing measurements need to be made and disseminated. It is possible to model the drift vs. time of the BS oscillator and reduce such updates.
- the mobile determines its location av associate this time with a framing marker of a received cellular communication signal by simply measuring the time delay from the time of location determination (e.g. in GPS time) to that of the framing marker.
- the location determination may be made at a time equal to that of this framing marker.
- R Tm [(x m -x b) 2 +(y m -y b) 2 -r(z m -z b) 2 2] ⁇ l/2
- the GPS receiver may have a delay associated with its RF and digital signal processing, which we call b GPS .
- b GPS is caused by delays within GPS receiver 52, and b ⁇ mm s ca sed by delays within cellular communication transceiver 54.
- b mutt there may be an extra delay in propagation from the basestation to the communication receiver due to multipath, which we call b mutt . We assume that this dominates any multipath delay associated with the GPS measurement.
- a basestation simulator which transmits the cellular signal with its framing structure and which is directly connected to the antenna port of the mobile and measuring the time of reception of the frame marker at the mobile.
- the basestation simulator uses a GPS receiver to synchronize its transmissions to the GPS time provided by this GPS receiver. Since the transmission delay from the basestation to receiver is zero, this approach will determine b ⁇ -b ⁇ without error (except for a small amount of measurement noise).
- This calibration procedure may be completely automated and is easily incorporated into a receiver testing procedure during manufacture.
- the excess multipath delay, b ⁇ remains the dominant source of error in synchronizing the basestation.
- this delay has bias with mean zero.
- the mean is greater than zero (measured versus true direct path delay).
- the basestation will, in general, receive a number of estimates for the time associated with each frame marker from several mobile units and perhaps from each mobile unit as well. Call these time-of-day estimates D l5 D 2 , ... D ⁇ .
- the basestation has a highly stable clock, then one may use this clock to maintain time between updates from the remote mobile units.
- the clock may be used in the smoothing process to eliminate poor measurements from the mobiles due to multipath.
- the measurements from the mobile may be used to measure the long term stability of the basestation clock, due to aging, for example.
- a GSM hyperframe is around 3.48 hours and a superframe is 6.12 seconds. Accordingly, a hyperframe is around 12528 seconds.
- any Doppler related effects do not influence the timing measurements described above.
- the mobile measures time at one instance and is predicting the time-of-day associated with a cellular signal frame boundary occurring at a different instance, an error can result due to the mobile's motion. This is especially the case if the mobile is rapidly moving and/or the difference in these time instances is large.
- this data may be supplied to the basestation which can then compensate for errors due to the Doppler associated with the range rate between the mobile and the basestation.
- Pseudolites are ground based transmitters which broadcast a PN code (similar to a GPS signal) which may be modulated on an L-band carrier signal, generally synchronized with GPS time. Each transmitter may be assigned a unique PN code so as to permit identification by a remote receiver. Pseudolites are useful in situations where GPS signals from an orbiting satellite might be unavailable, such as tunnels, mines, buildings or other enclosed areas.
- PN code similar to a GPS signal
- GPS signals as used herein, is intended to include GPS-like signals from pseudolites or equivalents of pseudolites.
- GPS Global Positioning Satellite
- the Glonass system primarily differs from GPS system in that the emissions from different satellites are differentiated from one another by utilizing slightly different carrier frequencies, rather than utilizing different pseudorandom codes.
- GPS Global Positioning Satellite
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Priority Applications (8)
Application Number | Priority Date | Filing Date | Title |
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JP2003501096A JP4860901B2 (en) | 2001-05-26 | 2001-05-26 | Method and apparatus for synchronizing base stations using mobile GPS stations |
IL15885001A IL158850A0 (en) | 2001-05-26 | 2001-05-26 | Methods and apparatuses for using mobile gps stations to synchronize base stations |
PCT/US2001/017113 WO2002098024A1 (en) | 2001-05-26 | 2001-05-26 | Methods and apparatuses for using mobile gps stations to synchronize basestations |
KR1020037015407A KR100881869B1 (en) | 2001-05-26 | 2001-05-26 | Methods and apparatuses for using mobile gps stations to synchronize basestations |
CNB018232981A CN1294708C (en) | 2001-05-26 | 2001-05-26 | Methods and apparatuses for using mobile GPS station to synchronize basestations |
AU2001261816A AU2001261816B2 (en) | 2001-05-26 | 2001-05-26 | Methods and apparatuses for using mobile GPS stations to synchronize basestations |
CA002447914A CA2447914C (en) | 2001-05-26 | 2001-05-26 | Methods and apparatuses for using mobile gps stations to synchronize basestations |
HK04106511A HK1063889A1 (en) | 2001-05-26 | 2004-08-30 | Methods and apparatuses for using mobile gps stations to synchronize basestations |
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PCT/US2001/017113 WO2002098024A1 (en) | 2001-05-26 | 2001-05-26 | Methods and apparatuses for using mobile gps stations to synchronize basestations |
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AU (1) | AU2001261816B2 (en) |
CA (1) | CA2447914C (en) |
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2003090380A1 (en) * | 2002-04-15 | 2003-10-30 | Qualcomm Incorporated | Method and apparatus for measuring frequency of a basestation in cellular networks using mobile gps receivers |
WO2004093350A1 (en) * | 2003-04-10 | 2004-10-28 | Siemens Communications, Inc. | Base station synchronization in a wireless network |
US7277050B2 (en) | 2003-02-28 | 2007-10-02 | Seiko Epson Corporation | Positioning system |
JP2008530901A (en) * | 2005-02-11 | 2008-08-07 | トゥルーポジション・インコーポレーテッド | Transmission / reception base station (BTS) synchronization |
KR101099175B1 (en) | 2004-01-26 | 2011-12-27 | 캠브리지 포지셔닝 시스템스 리미티드 | Transfer of calibrated time information in a mobile terminal |
US8638774B2 (en) * | 2007-06-22 | 2014-01-28 | Ubiquisys Limited | Controlling timing of synchronization updates |
US8774230B2 (en) | 2009-04-08 | 2014-07-08 | Qualcomm Incorporated | Conveying synchronization stratum information |
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CN100421367C (en) * | 2004-07-26 | 2008-09-24 | 华为技术有限公司 | Method for implementing synchronous transmission for base station |
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WO2003090380A1 (en) * | 2002-04-15 | 2003-10-30 | Qualcomm Incorporated | Method and apparatus for measuring frequency of a basestation in cellular networks using mobile gps receivers |
US6937872B2 (en) | 2002-04-15 | 2005-08-30 | Qualcomm Incorporated | Methods and apparatuses for measuring frequencies of basestations in cellular networks using mobile GPS receivers |
US7277050B2 (en) | 2003-02-28 | 2007-10-02 | Seiko Epson Corporation | Positioning system |
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US7460066B2 (en) | 2003-02-28 | 2008-12-02 | Seiko Epson Corporation | Positioning system |
WO2004093350A1 (en) * | 2003-04-10 | 2004-10-28 | Siemens Communications, Inc. | Base station synchronization in a wireless network |
KR101099175B1 (en) | 2004-01-26 | 2011-12-27 | 캠브리지 포지셔닝 시스템스 리미티드 | Transfer of calibrated time information in a mobile terminal |
JP2008530901A (en) * | 2005-02-11 | 2008-08-07 | トゥルーポジション・インコーポレーテッド | Transmission / reception base station (BTS) synchronization |
JP4750138B2 (en) * | 2005-02-11 | 2011-08-17 | トゥルーポジション・インコーポレーテッド | Transmission / reception base station (BTS) synchronization |
US8638774B2 (en) * | 2007-06-22 | 2014-01-28 | Ubiquisys Limited | Controlling timing of synchronization updates |
US8774230B2 (en) | 2009-04-08 | 2014-07-08 | Qualcomm Incorporated | Conveying synchronization stratum information |
Also Published As
Publication number | Publication date |
---|---|
CA2447914C (en) | 2008-07-22 |
CN1507710A (en) | 2004-06-23 |
KR20040003013A (en) | 2004-01-07 |
IL158850A0 (en) | 2004-05-12 |
JP2004533177A (en) | 2004-10-28 |
CA2447914A1 (en) | 2002-12-05 |
JP4860901B2 (en) | 2012-01-25 |
HK1063889A1 (en) | 2005-01-14 |
AU2001261816B2 (en) | 2008-05-08 |
KR100881869B1 (en) | 2009-02-06 |
CN1294708C (en) | 2007-01-10 |
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