WO2005025249A1 - Method for minimizing the maximum system time uncertainty for a mobile station - Google Patents
Method for minimizing the maximum system time uncertainty for a mobile station Download PDFInfo
- Publication number
- WO2005025249A1 WO2005025249A1 PCT/US2004/014979 US2004014979W WO2005025249A1 WO 2005025249 A1 WO2005025249 A1 WO 2005025249A1 US 2004014979 W US2004014979 W US 2004014979W WO 2005025249 A1 WO2005025249 A1 WO 2005025249A1
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- WIPO (PCT)
- Prior art keywords
- mobile station
- maximum
- abs
- sbs
- time
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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
- This application claims priority from copending United States provisional patent application serial number 60/500,432, filed September 5, 2003.
- This invention relates generally to improvements in wireless communications systems. More particularly, the invention relates to improvements in methods and apparatus for position location of a mobile station in a wireless communication system.
- Wireless communication systems typically include a plurality of mobile stations operating in a wireless network that includes a number of base stations through which the mobile stations communicate.
- Mobile station is the term used to describe a mobile communication device, such as a cellular telephone, PDA, pager, mobile computer, or the like.
- a base station typically includes a base station controller and one or more associated base transceiver station. The base station provides the functionality that enables a mobile station to access network services over the air interface.
- FCC Federal Communications Commission
- a common method of locating a mobile station is to determine the amount of time it takes for signals transmitted by known sources to reach the receiver of the mobile station to be located.
- One such source of transmitted signals is the Global Positioning Satellite (GPS) system.
- GPS Global Positioning Satellite
- the GPS system has a constellation of 24 satellites (plus other spare satellites) circling the earth every 12 hours at an altitude of 20,200 km. Each GPS satellite transmits a unique message that identifies its position at a particular time. Multiple GPS signals at any particular time enable reference points to be developed from which the location of a GPS receiver can be determined.
- the GPS receiver can calculate its position anywhere on the earth. The distances can be determined by measuring the time delays required for the GPS signals to travel from the GPS satellites to the receiver.
- the position of the mobile station is unknown, both within the GPS system and with respect to the base station network in which the mobile system operates. All base stations are synchronized to the same network system time (i.e., all base station clocks are adjusted precisely to the same reference time, which is typically based on GPS time). When a signal is transmitted by a base station and received by the mobile station, there is an associated unknown propagation delay. [0009] Thus, GPS signal acquisition duration is proportional to both the system time uncertainty and the position uncertainty of the mobile station. However, in some applications, time uncertainty is the dominant parameter.
- the mobile station To acquire the GPS signal, the mobile station must turn on its GPS circuitry for a time period proportional to the maximum propagation delay between a base station in a known location and the mobile station, plus a time period proportional to the position uncertainty of the mobile station. Without further information, the maximum propagation delay is based on the worst case distance between a base station and the mobile station within its cell coverage (i.e., the maximum cell size).
- the GPS circuitry should only be activated during a minimal search time window, for example, using methods for minimizing the search time window for the mobile station to acquire the GPS signals.
- a method for minimizing maximum system time uncertainty uses a neighbor search window size (NSWS) parameter.
- the NSWS parameter is received in a message transmitted from a base station and a conversion table is used to match the NSWS parameter with a corresponding maximum antenna range (MAR).
- MAR maximum antenna range
- the maximum propagation delay is calculated based on the MAR and propagation speed.
- the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- a method for minimizing maximum system time uncertainty uses neighbor pilot measurements (NPM).
- a serving base station (SBS) is determined, and SBS multipath signals are received from SBS pilots transmitted by the serving base station.
- An earliest SBS multipath signal is selected from the SBS multipath signals, and N alternate base stations (ABSs) are determined.
- N sets of ABS multipath signals are received from N sets of ABS pilots transmitted by the N ABSs, and N earliest ABS multipath signals are selected from the N sets of ABS multipath signals.
- N time delays are determined with each of the N time delays being a time delay between each of the N earliest ABS multipath signals and the earliest SBS multipath signal.
- a maximum antenna range (MAR) is estimated, based on the N time delays. In one embodiment, the maximum propagation delay is calculated based on the MAR and propagation speed. Then, the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- a method for minimizing a maximum system time uncertainty uses a last successful position determination fix (LSPDF).
- the last successful position determination fix is determined, and a new fix is determined as the position of the mobile station at a current time.
- the time difference, t d is calculated from the last successful position determination fix to the new fix.
- the speed of the mobile station is determined, and the maximum distance d max that the mobile station has moved since the last successful position determination fix based on the time difference, t d , and the speed of the mobile station is determined.
- the maximum antenna range is set to equal the sum of the maximum distance d ma x and the serving base station distance d sbS -
- the maximum propagation delay is calculated based on the MAR and propagation speed.
- the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- a NSWS parameter is received in a message transmitted from a base station.
- MARNSWS is determined by using a conversion table to match the NSWS parameter, and the SBS is determined.
- SBS multipath signals are received from SBS pilots transmitted by the serving base station, and an earliest SBS multipath signal is selected from the SBS multipath signals.
- N ABSs are determined, and N sets of ABS multipath signals are received from N sets of ABS pilots transmitted by the N alternate base stations (ABS).
- N earliest ABS multipath signals are selected from the N sets of ABS multipath signals, and N time delays are determined with each of the N time delays being a time delay between each of the N earliest ABS multipath signals and the earliest SBS multipath signal.
- MARNPM is estimated, based on the N time delays, and the last successful position determination fix is determined.
- a new fix is defined as the position of the mobile station at the current time, and a time difference, t d , from the last successful position determination fix to the new fix is determined.
- the speed of the mobile station is determined, and a MARLSPDF based on the time difference, t d , and the speed of the mobile station is estimated.
- MAR is calculated, based on a weighted combination of MARNSWS, MARNPM and MARLSPDF.
- the maximum propagation delay is calculated based on the MAR and propagation speed.
- the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- Figure 1 is simplified diagram of a wireless communication system.
- Figure 2 is a flow diagram illustrating a method using neighbor search window size (NSWS).
- NSWS neighbor search window size
- Figure 3 is a flow diagram illustrating a method using neighbor pilot measurements.
- FIG. 1 is a simplified diagram of a wireless communication system in which mobile station 10, such as wireless telephones 10A or wireless PCs 10B, are located within the cell coverage of base stations 12.
- the base stations 12 are coupled to base station controllers (BSC) 14 which are coupled to a public switched telephone network (PSTN) 16.
- BSC base station controllers
- PSTN public switched telephone network
- some mobile stations 10 may be exchanging data with the base stations 12, while other mobile stations 10 may be on standby mode.
- messages communicated from the base station 12 contain "aiding information" that allows the mobile stations 10 to speed up their acquisition of the GPS signal for a position determination fix.
- the aiding information may include, for example, neighbor search window size (NSWS) parameters, neighboring pilot measurements (NPM) from various base stations 12, or the like.
- the mobile stations 10 use the aiding information to narrow the search time window (i.e., minimize the maximum system time uncertainty/maximum propagation delay), compensate for Doppler effects, and tune to the GPS frequency to begin correlating the received GPS signal. Upon receipt of the GPS signal, the mobile stations 10 can then determine their respective position locations using various known techniques.
- the position of the mobile station is unknown. If power consumption were not a concern, the time to acquire a GPS signal would not be critical, and the GPS circuitry could be left on operational mode indefinitely. However, as mentioned, mobile stations 10 have limited battery capacity and must conserve power consumption. Thus, to conserve power, the GPS circuitry should only be activated during a minimal search time window.
- One method of minimizing the search window for acquiring the GPS signals is to include a highly accurate clock in the mobile station 10 that is synchronized to GPS time so that an appropriate time can be determined to search for the GPS signal.
- a highly accurate clock in each mobile station 10 that can establish and maintain synchronization with GPS time may not be cost effective. Also, accommodating the volume and power requirements of such highly accurate clock within a mobile station 10 may be difficult.
- all base stations are synchronized to the same network system time. That is, all base station clocks are adjusted precisely to the same reference time, which is typically based on GPS time. By including a highly accurate clock synchronized to GPS time, clock information of the base stations 12 can be transmitted to the mobile station 10 to minimize the search window for the GPS signals for position location.
- the mobile station 10 and the base station 12 are typically not at the same location, there is a propagation delay in the clock information received by the mobile station 10 from the base station 12. Without auxiliary information, the maximum propagation delay in a wireless communication system is based on the worst case distance between a base station 12 and the mobile station 10 within its cell coverage. This is the largest possible cell size. This establishes the maximum system time uncertainty, and hence, the maximum search time window for the mobile station 10. If the maximum propagation delay can be refined to a value less than the worst case propagation delay, then the search time window, and hence, mobile station power consumption, are minimized. With the search time window minimized, the mobile station 10 can turn on its GPS circuitry to receive the GPS signal during the appropriate time window.
- FIG. 2 is a flow diagram illustrating a method using neighbor search window size (NSWS) for minimizing the maximum system time uncertainty (i.e., maximum propagation delay) for improving duration and accuracy of a position determination fix using GPS.
- the mobile station 10 receives the NSWS parameter in a message transmitted from the base station 12.
- the (NSWS) parameter may be used to estimate maximum propagation delay due to the cell size of the serving base station.
- the NSWS parameter is deployed in such a way to be as large as possible to allow a successful handoff to a neighboring base station.
- the NSWS should be as small as possible to reduce the neighboring pilot search time (this reduces power consumption and probability of neighbor base station pilot detection false alarm).
- a conversion table listing NSWS parameters and their corresponding maximum antenna range is embedded in the memory of the mobile station 10.
- MAR is equal to the maximum propagation delay (which is equal to the maximum system time uncertainty) times the propagation speed c (i.e., speed of light).
- the mobile station 10 looks up the corresponding MAR from the conversion table in step 210.
- the corresponding MAR using this method is denoted by MARNSWS.
- step 220 the maximum propagation delay is determined.
- Maximum propagation delay equals MAR (i.e., MARNSWS) divided by propagation speed c (i.e., speed of light).
- the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- FIG. 3 is a flow diagram illustrating a method using neighbor pilot measurements (NPM) for minimizing the maximum system time uncertainty for improving duration and accuracy of a position determination fix using GPS.
- NPM neighbor pilot measurements
- the mobile station 10 determines the SBS based on known techniques. Once the serving base station is determined, the mobile station 10 can receive valid SBS multipath signals from all usable SBS pilots transmitted by the serving base station in step 310. [0030] From the received valid SBS multipath signals, in step 320, the mobile station 10 selects the earliest SBS multipath signal received from the serving base station. In step 330, the mobile station 10 receives valid ABS multipath signals from all usable ABS pilots transmitted by alternate base stations (ABS) other than the serving base station.
- ABS alternate base stations
- the alternate base stations are base stations (other than the serving base station) within the mobile communications network that are closest to the mobile station 10.
- the number of alternate base stations N is a design choice, the number of alternate base stations N may conveniently be three.
- the mobile station 10 selects the earliest ABS multipath signal from the received valid ABS multipath signals. Thus, for each alternate base station, there is a corresponding earliest ABS multipath signal.
- the mobile station 10 estimates the MAR based on delays between the earliest ABS multipath signals from the alternate base stations and the earliest SBS multipath signal from the serving base station.
- the mobile station 10 determines the time delay associated with each of the earliest ABS multipath signals from the alternate base stations relative to the earliest SBS multipath signal from the serving base station. The mobile station 10 selects the earliest ABS multipath signal from the alternate base stations with the largest time delay ( ⁇ max ). Similarly, it selects the earliest ABS multipath signal from the alternate base stations with the smallest time delay (x mm ).
- the estimated MAR should be approximately be between 0.7 times propagation speed c times (X maX - ⁇ mm ) and 1.6 times propagation speed c times ( ⁇ max - Tr mn )-
- MARNPM 2 x c x ( ⁇ ⁇ ax - ⁇ ⁇ n ) (1) where c is the propagation speed
- MARNPM 2 x c x ( ⁇ ⁇ ax - ⁇ ⁇ n ) (1) where c is the propagation speed
- MARNPM An alternative way of describing the above is to select the largest time delay T max from N time delays corresponding to the N alternate base stations, and to select the smallest time delay ⁇ m ⁇ n from the same N time delays.
- estimate MAR to be a constant K times propagation speed c times the difference between T max and ⁇ m ⁇ n .
- the constant K is approximately between 0.7 and 1.6.
- a conservative estimate for K is 2.
- step 360 the maximum propagation delay is determined.
- Maximum propagation delay equals MAR (i.e., MARNPM) divided by propagation speed c (i.e., speed of light).
- the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- FIG 4 is a flow diagram illustrating a method using last successful position determination fix (LSPDF) for minimizing the maximum system time uncertainty for improving duration and accuracy of a position determination fix using GPS.
- LSPDF last successful position determination fix
- the current serving base station must be the same as the serving base station that determined the last successful position determination fix.
- the mobile station 10 calculates the time difference t between the last successful position determination fix and the new fix (i.e., the current time).
- the mobile station 10 estimates the maximum distance d max that the mobile station 10 has moved since the last successful position determination fix.
- the maximum distance d max is based on a predetermined maximum speed V max of the mobile station 10 which may be recorded in the memory of the mobile station 10.
- the predetermined maximum speed V max of the mobile station 10 may be entered by the user of the mobile station 10. In yet another embodiment, the predetermined maximum speed V max of the mobile station 10 may be dynamically determined based on sensor measurements or the last successful GPS measurements. The maximum distance d max is based on the predetermined maximum speed V max of the mobile station 10 and the time difference t d . In step 420, MAR is set to equal the sum of the maximum distance d max and the serving base station distance d srjs . The serving base station distance d sbs is the distance between the serving base station (during the last successful position determination fix) and the last successful position determination fix.
- step 430 the maximum propagation delay between the last successful position determination fix and the new fix is determined.
- Maximum propagation delay equals maximum distance d ma x (i.e., MAR) divided by propagation speed c (i.e., speed of light).
- the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- the MAR using this method is denoted by MARLSPDF.
- the MAR can be estimated based on a weighted combination of MARNSWS, MARNPM and MARLSPDF.
- the MAR is the minimum of MARNSWS, MARNPM and MARLSPDF.
- the MAR can be used to calculate maximum propagation delay, since the maximum propagation delay is equal to MAR divided by the propagation speed c. Then, the search time window is set proportionally to the sum of the maximum propagation delay and a compensation for the position uncertainty of the mobile station.
- Coupled means "connected to” and such connection can either be direct or, where appropriate in the context, can be indirect, e.g., through intervening or intermediary devices or other means.
Abstract
Description
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Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
BRPI0414097-4A BRPI0414097A (en) | 2003-09-05 | 2004-05-11 | method to minimize maximum system time uncertainty for a mobile station |
KR1020067004570A KR101088844B1 (en) | 2003-09-05 | 2004-05-12 | Method for minimizing the maximum system time uncertainty for a mobile station |
IL173983A IL173983A0 (en) | 2003-09-05 | 2006-02-27 | Method for minimizing the maximum system time uncertainty for a mobile station |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US50043203P | 2003-09-05 | 2003-09-05 | |
US60/500,432 | 2003-09-05 |
Publications (2)
Publication Number | Publication Date |
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WO2005025249A1 true WO2005025249A1 (en) | 2005-03-17 |
WO2005025249A8 WO2005025249A8 (en) | 2005-12-15 |
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Application Number | Title | Priority Date | Filing Date |
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PCT/US2004/014979 WO2005025249A1 (en) | 2003-09-05 | 2004-05-11 | Method for minimizing the maximum system time uncertainty for a mobile station |
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KR (1) | KR101088844B1 (en) |
BR (1) | BRPI0414097A (en) |
IL (1) | IL173983A0 (en) |
WO (1) | WO2005025249A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011100865A1 (en) * | 2010-02-19 | 2011-08-25 | Telefonaktiebolaget L M Ericsson (Publ) | Method and arrangement of determining timing uncertainty |
CN102783227A (en) * | 2010-02-19 | 2012-11-14 | 爱立信(中国)通信有限公司 | Method and arrangement of determining timing uncertainty |
CN103686810A (en) * | 2013-12-10 | 2014-03-26 | 航天恒星科技有限公司 | Satellite network neighbor detection method |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR102263608B1 (en) * | 2019-07-11 | 2021-06-14 | 한국외국어대학교 연구산학협력단 | System for guiding multi road and method thereof |
Citations (2)
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US6526039B1 (en) * | 1998-02-12 | 2003-02-25 | Telefonaktiebolaget Lm Ericsson | Method and system for facilitating timing of base stations in an asynchronous CDMA mobile communications system |
US6542743B1 (en) * | 1999-08-31 | 2003-04-01 | Qualcomm, Incorporated | Method and apparatus for reducing pilot search times utilizing mobile station location information |
-
2004
- 2004-05-11 BR BRPI0414097-4A patent/BRPI0414097A/en not_active IP Right Cessation
- 2004-05-11 WO PCT/US2004/014979 patent/WO2005025249A1/en active Application Filing
- 2004-05-12 KR KR1020067004570A patent/KR101088844B1/en not_active IP Right Cessation
-
2006
- 2006-02-27 IL IL173983A patent/IL173983A0/en unknown
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US6526039B1 (en) * | 1998-02-12 | 2003-02-25 | Telefonaktiebolaget Lm Ericsson | Method and system for facilitating timing of base stations in an asynchronous CDMA mobile communications system |
US6542743B1 (en) * | 1999-08-31 | 2003-04-01 | Qualcomm, Incorporated | Method and apparatus for reducing pilot search times utilizing mobile station location information |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011100865A1 (en) * | 2010-02-19 | 2011-08-25 | Telefonaktiebolaget L M Ericsson (Publ) | Method and arrangement of determining timing uncertainty |
CN102783227A (en) * | 2010-02-19 | 2012-11-14 | 爱立信(中国)通信有限公司 | Method and arrangement of determining timing uncertainty |
EP2537382A1 (en) * | 2010-02-19 | 2012-12-26 | Telefonaktiebolaget LM Ericsson (publ) | Method and arrangement of determining timing uncertainty |
US8692715B2 (en) | 2010-02-19 | 2014-04-08 | Telefonaktiebolaget L M Ericsson (Publ) | Method and arrangement of determining timing uncertainty |
EP2537382A4 (en) * | 2010-02-19 | 2014-07-30 | Ericsson Telefon Ab L M | Method and arrangement of determining timing uncertainty |
US8983452B2 (en) | 2010-02-19 | 2015-03-17 | Telefonaktiebolaget L M Ericsson (Publ) | Methods and arrangements for maintaining timing characteristics |
US9684057B2 (en) | 2010-02-19 | 2017-06-20 | Unwired Planet, Llc | Method and arrangement of determining timing uncertainty |
CN103686810A (en) * | 2013-12-10 | 2014-03-26 | 航天恒星科技有限公司 | Satellite network neighbor detection method |
CN103686810B (en) * | 2013-12-10 | 2017-02-15 | 航天恒星科技有限公司 | Satellite network neighbor detection method |
Also Published As
Publication number | Publication date |
---|---|
WO2005025249A8 (en) | 2005-12-15 |
KR101088844B1 (en) | 2011-12-06 |
KR20060088535A (en) | 2006-08-04 |
IL173983A0 (en) | 2006-07-05 |
BRPI0414097A (en) | 2006-11-14 |
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