WO2001058195A1 - Systeme de positionnement sans fil base sur un reseau permettant de localiser des telephones cellulaires amps (amrf) - Google Patents

Systeme de positionnement sans fil base sur un reseau permettant de localiser des telephones cellulaires amps (amrf) Download PDF

Info

Publication number
WO2001058195A1
WO2001058195A1 PCT/CA2000/000103 CA0000103W WO0158195A1 WO 2001058195 A1 WO2001058195 A1 WO 2001058195A1 CA 0000103 W CA0000103 W CA 0000103W WO 0158195 A1 WO0158195 A1 WO 0158195A1
Authority
WO
WIPO (PCT)
Prior art keywords
mss
signal
location
estimation
squares
Prior art date
Application number
PCT/CA2000/000103
Other languages
English (en)
Inventor
Michel Fattouche
Richard Klukas
Andrew Borsodi
Mark Astridge
Lyle Pakula
James George
Original Assignee
Cell-Loc Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/130,637 external-priority patent/US6330452B1/en
Application filed by Cell-Loc Inc. filed Critical Cell-Loc Inc.
Priority to AU25277/00A priority Critical patent/AU2527700A/en
Publication of WO2001058195A1 publication Critical patent/WO2001058195A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/12—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
    • G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
    • G01S1/04—Details
    • G01S1/045—Receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
    • G01S11/02—Systems for determining distance or velocity not using reflection or reradiation using radio waves
    • G01S11/10—Systems for determining distance or velocity not using reflection or reradiation using radio waves using Doppler effect
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/04—Position of source determined by a plurality of spaced direction-finders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/06—Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements

Definitions

  • This invention relates to location finding and tracking of Advanced Mobile Phone System (AMPs) Frequency Division Multiple Access (FDMA) Cellular Telephones (CTs) using a network-based Wireless Location System (WLS).
  • AMPs Advanced Mobile Phone System
  • FDMA Frequency Division Multiple Access
  • CTs Cellular Telephones
  • WLS Wireless Location System
  • FDMA is a multiple access technique used in some standards worldwide such as in AMPs which is the North American standard for analog CTs. Other standards exist such as Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA).
  • TDMA Time Division Multiple Access
  • CDMA Code Division Multiple Access
  • a unique feature in FDMA (which the patent takes advantage of) is the continuous transmission of information over one frequency band (e.g. during "conversation" mode or during "waiting for answer” mode) as long as no hand-offs, call termination nor call drop take place.
  • a network- based WLS is important since it can be passive, and is able to locate existing CTs without modification to the CTs or to the cellular antenna infrastructure. The need for wireless location finding and tracking of CTs is ever increasing.
  • E911 enhanced 911
  • RMS Root Mean Square
  • the WLS it is important for the WLS to be passive. This is possible in a network-based WLS.
  • CT is forced to transmit radio signals for location purposes.
  • Yet another intention of an aspect of the invention is to use the diversity antennas, or the sectored antennas, or both to estimate the AOA of the CT to a MS.
  • Yet another intention of an aspect of the invention is to use the entire RECC message for locating the CT without having to transfer all the raw data back to the host.
  • Yet another intention of an aspect of the invention is to locate a powered-up AMPs-CT by using the signal transmitted by the CT over the RVC channel without incurring air time charges and while the CT remains in the "waiting for answer" mode.
  • Yet another intention of an aspect of the invention is to locate an AMPs-CT by estimating the Phase Of Arrival (POA) of existing or generated tones either over the RECC channel or over the RVC channel.
  • the phases can be extracted using SR algorithms in order to reduce the effect of multipath (MP i l ).
  • Yet another intention of an aspect of the invention is to use the estimated POA to estimate either the TOA of the signal r i k (t) or its AOA at the k lh antenna of the i th MS using Phase Difference Of Arrival (PDOA).
  • PDOA Phase Difference Of Arrival
  • Yet another intention of an aspect of the invention is to reduce the overall group delay variations through the receiver at each MS.
  • Yet another intention of an aspect of the invention is to reduce the effect of Local Oscillator (LO) drift ( ⁇ f ik ) and clock offsets. This is accomplished by using the Global Positioning System (GPS) as a source for a common reference.
  • GPS Global Positioning System
  • Yet another intention of an aspect of the invention is to estimate the Doppler shift ( ⁇ f i k ) at each MS in order to estimate the speed and Direction of Travel (DOT) of the CT using Frequency Difference Of Arrival (FDO A) .
  • Yet another intention of an aspect of the invention is to force the CT over several channels in order for the effective bandwidth, BW eff , to be increased thereby increasing the resolving power of the WLS.
  • Yet another intention of an aspect of the invention is to locate a 911 Cellular caller and to transfer its positional information to the appropriate PSAP during "unanswered conversation" mode.
  • Yet another intention of an aspect of the invention is to calibrate the wireless location system on a regular basis in an inexpensive fashion.
  • Yet another intention of an aspect of the invention is to minimize HDOP by allowing more MSs to tune to the same CT while at the same time reducing the effect of noise and multipath by solving for the position of the CT using Least Squares weighted by the individual RSSI.
  • Yet another intention of an aspect of the invention is to solve for the position of the CT using Least Squares where misclosures and standardized residuals are used to flag the observations that might have a blunder.
  • Yet another intention of an aspect of the invention is to use Chaffee's method or Location On the Conic Axis (LOCA) to detect solution bifurcation.
  • LOCA Location On the Conic Axis
  • Yet another intention of an aspect of the invention is to use LOCA and/or Plane Intersection to provide an initial position for Least Squares. • Yet another intention of an aspect of the invention is to use individually, or in combination, TDOA observations, hybrid TDOA observations and AOA observations to locate the CT.
  • Yet another intention of an aspect of the invention is to use the TDOA information from two MSs or the AOA from several antennas at the same MS to resolve the AOA ambiguity at such an MS. • Yet another intention of an aspect of the invention is to use the range information from two
  • Base Station is a transceiver that can service a number of CTs in a cell.
  • MS Monitoring Site
  • Host is a central processor to process all positional information that are received from the MSs and to transmit monitoring orders to all MSs.
  • the host can also be responsible for location services such as fleet management, location sensitive billing, etc.
  • the Host can also be responsible for software/firmware upgrades/re-configurations of the MSs.
  • Reverse Control Channel is the channel to be used by the CT to to transmit a control signal to the BS such as call originations, registrations, etc.
  • FCC Forward Control Channel
  • RVC Reverse Voice Channel
  • FVC Forward Voice Channel
  • Originations are defined as calls initiated by a CT.
  • Pages are initiated by a BS to a CT.
  • Unanswered conversation mode is defined as an origination that is in conversation mode that has not been answered yet by the called party.
  • Answered conversation mode is defined as an origination that is in conversation mode that has been answered by the called party.
  • SR Super-Resolution
  • SR algorithm transforms a frequency domain signal, S(f), to a time domain signal, s(t), with a higher resolution than the resolution offered by the inverse Fourier transform, i.e. s(t) has better resolution than the inverse Fourier transform F " ' ⁇ S(f) ⁇ ) of S(f)).
  • SR algorithms are well known in the literature and include:
  • an inverse SR algorithm can process a frequency domain signal in order to improve its frequency resolution over the conventional Rayleigh resolution.
  • a preferred embodiment of the inverse SR algorithm comprises
  • Diversity Antennas are cellular antennas that exist in almost every BS. Diversity can be accomplished either using horizontal separation, vertical separation, or both. In this patent, we use the horizontally separated diversity antennas as a mean to estimate the horizontal Angle Of Arrival (AOA) of the received radio signal at a MS. When the diversity antennas are vertically separated, either the elevation AOA is estimated or the received signals from all antennas at a given MS are combined using:
  • Sectored Antennas are cellular antennas that exist in some BS that service more than one sector. Each sector has a dedicated antenna (or set of antennas if diversity is applied).
  • Fourier Transform-Based Filters are filters that:
  • Effective Bandwidth is the bandwidth over which the received radio signal at a given MS has been observed during a given observation interval.
  • the inventors propose a variety of methods and apparatus to obtain the various objects set forth above.
  • a method of estimating the location of a powered-up CT comprising the steps of calling the CT; monitoring the paging of the CT over a FOCC channel using a MS; acquiring and processing the response s(t) of the CT to the page over the corresponding RECC channel by a number of MSs; and dropping the call.
  • a method of estimating the location of a CT that is initiating a call comprising the steps of monitoring the initiation of the call over a RECC channel using a MS; monitoring the RVC channel assignment over the corresponding FOCC channel using the same MS; and notifying a plurality of MSs to monitor and process the signal s(t) generated by the CT over the assigned RVC channel during an observation time T which coincides with the CT being in "unanswered conversation" mode.
  • a method of estimating the location of a powered-up CT by calling the CT monitoring the paging of the CT over a FOCC channel using a MS; monitoring the response of the CT to the page over the corresponding RECC channel using the same MS ; monitoring the RVC channel assignment over the corresponding FOCC channel using the same MS; notifying a plurality of MSs to monitor and process the signal s(t) generated by the CT over the assigned RVC channel during an observation time T; and dropping the call.
  • a method to estimate the location of a CT comprising the steps of: characterizing a relative group delay, ⁇ t, k - ⁇ t, m , between a k" 1 antenna of an i th MS and an m Ul antenna of a j"' MS prior to operation; and removing the relative group delay, ⁇ t ; k - ⁇ t j m , between the k Ul antenna of the i Ul MS and the m* antenna of the j* MS from the estimated Time Difference Of Arrival, ⁇ i ⁇ k - ⁇ j m , between the k* antenna of the i ft MS and the m Ul antenna of the j Ul MS.
  • a system to estimate the location of a CT comprising a plurality of MSs to receive the signal s(t) transmitted by the CT; each receiver including an IF-sampling Receiver comprising: a number of IF stages to convert the received RF signal r i k (t) to an IF signal of IF frequency f t ; a pre-aliasing filter; an Analog-to-Digital converter that converts the IF analog signal to an IF digital signal; and a means for processing the sampled signal.
  • a method to estimate the location of a CT comprising the steps of: receiving a received signal k (t); estimating a carrier offset (due to Doppler, ⁇ f i k , and due to LO offset, ⁇ f i k ) of the signal r ; k (t); and adjusting a number of LOs in the i lh MS during reception of r i k (t) based on the estimated carrier offset. Additional aspects of this invention are set forth in claims 35-42, 45-56 and 59-63 attached hereto, which are hereby incorporated in this summary by reference.
  • a method of estimating the location of a CT comprising the steps of: receiving a signal s(t) transmitted by the CT at a plurality of MSs; each MS using an IF-sampling Receiver; converting the received RF signal r i k (t) to an IF signal of IF frequency f,; filtering the IF signal with a pre-aliasing filter; converting the IF analog signal to an IF digital signal; and processing the sampled signal.
  • a system to estimate the location of a CT comprising the steps of: detecting RECC collisions and avoiding positioning when RECC collisions occur; and detecting blank-and-burst occurrences over the RVC channel and avoiding positioning on a tone selected from the group consisting of SAT tones, ST tones or pitch using Procedure VI.
  • a method of estimating the location of a CT comprising the steps of: processing location information from an MS; and weighting the location information from each MS based on the RSSI of the location information.
  • a method of estimating the location of a CT comprising the steps of: processing location information; and using misclosures and/or standardized residuals to flag observations that might contain a blunder.
  • a method of estimating the location of a CT comprising the steps of: processing location information; and using a method selected from the group consisting of Chaffee's method and LOCA to detect solution bifurcation.
  • a method of estimating the location of a CT comprising the steps of: processing location information; quantifying the effect of geometry on AOA positioning using the design matrix in equation (48); quantifying the effect of geometry on position estimation, with both AOA and TDOA observations, using the design matrix in equation (49); and quantifying the effect of geometry on speed and direction of travel estimation using the design matrix in equation (54).
  • a system to estimate the location of a CT comprising: a location information processor wherein location information from each MS is weighted based on its corresponding RSSI.
  • a system to estimate the location of a CT comprising: a location information processor wherein misclosures and/or standardized residuals are used to flag observations that might contain a blunder.
  • a system to estimate the location of a CT comprising: a location information processor which is adapted to use a method selected from the group consisting of Chaffee's method and LOCA to detect solution bifurcation.
  • a system which estimates the location of a CT, the system comprising: at least two MS; and a location information processor in which a combination of AOA and TDOA observations are used such that the CT can be located with as few as two MSs. Additional aspects of this invention are set forth in claims 103, 110-112 and 118 attached hereto, which are hereby incorporated in this summary by reference.
  • a system which estimates the location of a CT, the system comprising: at least one MS; and a location information processor in which a combination of AOA and TOA observations are used such that the CT can be located with as little as one MS.
  • a system which estimates the location of a CT, the system comprising: at least two MS; and a location information processor in which a combination of TOA observations are used such that the CT can be located with as little as two MSs.
  • a system which estimates the location of a CT, the system comprising: at least one host; a location information processor for producing position information; and means for transferring positional information from the Host over the internet to a user.
  • Figure 1 illustrates the transmission by the CT (101) of a signal s(t) (103).
  • the CT is AMPs-based, it transmits a signal either over the RECC channel or over the RVC channel. In either case, the transmission is intended for the Base Station (BS) (102) with the most suitable Received Signal Strength Indicator (RSSI) at any one of its antennas.
  • BS Base Station
  • RSSI Received Signal Strength Indicator
  • Figure 2 illustrates the transmission of the signal s(t) by the CT at Time ' ⁇ 0 ' and its reception by the k* antenna at the i* Monitoring Site (MS) (201) at Time of Arrival: ⁇ i, -
  • MS Monitoring Site
  • a minimum of three MSs (with a minimum of one antenna per MS) are required using TDOA positioning, or a minimum of two MSs (with a minimum of two horizontally spaced antennas per MS) using Angle Of Arrival (AOA) positioning.
  • AOA Angle Of Arrival
  • Figure 3 assumes without loss of generality, that each MS has two antennas. Figure 3 also assumes that the CT is far from each MS with respect to the baseline between the two antennas at each MS. The second assumption implies that the received wavefront is planar, i.e. where: • ⁇ u is the Angle Of Arrival (AOA), at the first antenna of the i ⁇ MS,
  • AOA Angle Of Arrival
  • Figure 5 illustrates the two-dimensional (horizontal) Line of Position (501) for TDOA2,l,k,m which is defined as
  • Figure 6 illustrates the two intersecting Trajectories for the two- dimensional coordinates (x,y) of the CT (603) based on TDOA2,l,k,m (601) and
  • Figure 7 illustrates the Second Stage of the Wireless location system where the 1 th MS down- loads its positional information to a central processor which we refer to as the Host (701).
  • the Host uses all the positional information to estimate the coordinates (x,y) of the CT and its speed v and DOT ⁇ . Without loss of generality, Figure 7 assumes that each MS has two antennas.
  • FIG 8 illustrates the description of Design I for the IF-sampling receiver.
  • the received RF signal r i>k (t) at the k ⁇ antenna of the i* MS is initially filtered by an RF Band Pass Filter (BPF) (802), amplified by an RF amplifier (803), down-converted by several Intermediate Frequency (IF) stages (810).
  • BPF Band Pass Filter
  • IF Intermediate Frequency
  • Each IF stage consists of a mixer (804) with an LO (808) generated using an RF synthesizer (809), an IF BPF (805) and an IF amplifier (806).
  • the resulting analog IF signal (807) of IF frequency f is filtered by a pre-aliasing filter (811), sampled by an AID (812) and filtered again using digital filters (813) in order to generate a digital IF signal (814) of frequency f 2 , where f 2 ⁇ f,.
  • An optional Direct Digital Converter (DDC) (815) is used to down-convert the digital IF signal (814) to Baseband.
  • DSP Digital Signal Processor
  • FOA Frequency Of Arrival
  • a function of the estimated FOA is fed-back to a Direct Digital Synthesizer (DOS) (819) which controls the RF synthesizer (809).
  • the DSP (817) also provides a reference signal (820) to the DDS (819).
  • a preferred source for the reference signal (820) is one that is common to all MSs such as a GPS signal.
  • Figures 9a, 9b, 9c and 9d illustrate a flow diagram for the positioning strategy.
  • the positioning strategy consists of a number of algorithms (Least Squares, Location On the Conic Axis (LOCA), Plane Intersection) and numerous decisions. Given a set of observations, there are 4 possible outcomes: two LS position solutions (908), two LOCA position solutions (909), one LS position solution (923, 936), and no position solution (927).
  • RF Transmission More specifically, the Low Pass (LP) equivalent transmitted signal, s (t) , can be modeled as
  • Gi ⁇ represents the gain (real) due to the tiansm tting and receiving antennas from the CT to the k ft antenna of the 1 th MS (a function of the two antenna patterns respectively), .
  • R ⁇ k represents the attenuation (real) due to the propagation channel, where
  • n is a real number (usually between 2 and 4) that depends on the channel and . is the range between the CT and the k ⁇ antenna of the i ⁇ MS,
  • . ⁇ f ⁇ is the frequency offset due to the Doppler shift over the propagation channel (a function of speed, v, and Direction Of Travel (DOT), ⁇ ).
  • . ⁇ i)k is the Time Of Arrival (TOA) of the signal n k (t) at the ⁇ 1 antenna of the i ⁇ MS (a function of the range ⁇ ), . ⁇ ti ,k is the overall group delay through the k ft antenna of the 1 th MS (usually a function of frequency), .
  • w i ,k (t) represents the Additive White Gaussian Noise (AWGN, complex) due to thermal noise at the k ⁇ antenna of the 1 th MS (a function of temperature and bandwidth), .
  • MPi .k (t) represents all multipath components (complex) at the k 0 antenna of the i ⁇ MS (a function of the environment and of the elevation of the antennas), and .
  • I; >k (t) represents interference (both in-band and out-of-band) at the k ⁇ antenna of the i ⁇ MS.
  • Baseband Reception Several IF stages down-convert the received RF signal, r, k (t), to an analog baseband signal, f, k (t) , which is equivalent to performing the following operation:
  • ⁇ fi ⁇ is the frequency error between the Local Oscillators (LOs) in the CT and the LOs in the k ft receiver at the I th MS.
  • LOs Local Oscillators
  • f ⁇ f c + ⁇ fj ⁇ + ⁇ fyc
  • ⁇ f f c is the phase error between the Local Oscillators (LOs) in the CT and the LOs in the k ⁇ receiver at the r* MS.
  • an Analog-to-Digital (A-to-D) Converter converts the baseband signal, ?j jk (t) , to a digital signal, rj k (m), which is equivalent to performing the following operation:
  • ⁇ Ti is the sampling interval in the k & receiver at the i ⁇ MS
  • • i ,k (m) is the quantization noise which depends on the number of bits in the A-to-D.
  • the first source, R, ⁇ k can be used to estimate R,- ⁇ .
  • R ⁇ k is unreliable due to the nature of the radio channel where RF shadowing and flat fading can deviate the value of "n" in "R ⁇ k " from 2 (for Line
  • ⁇ i, ⁇ -2 ⁇ ( £+ ⁇ f i)k ) ( ⁇ i ⁇ + ⁇ t ⁇ * ) + ⁇ i>k ⁇ mod 2 ⁇ (10)
  • the time of transmission, ⁇ 0 , in (11) is usually unknown to the MSs.
  • the amount of the ambiguity is a function of the baseline between the two receiving antennas, i.e. between
  • n is the integer ambiguity
  • the carrier frequency, f c can take values from 800MHz (with a wavelength ⁇ of 37.5cm) to 1.9GHz (with a wavelength ⁇ of 15.8cm).
  • Solution I When the baseline between the k ⁇ antenna at the i ⁇ MS and the m ⁇ antenna at the j ⁇ MS is small relative to the wavelength, ⁇ , we assume without loss of generality that the two antennas belong to the same MS (which can be achieved using cellular diversity antennas, cellular sectored antennas, or any other type of antennas, at the same BS, when the MS is collocated with a BS). In this case, it is possible to generate a solution using either TDOA or PDOA.
  • the TDOA solution between the two antennas is a hyperbola while the PDOA solution between the two antennas is a line. Both solutions approximate the exact solution and coincide asymptotically, i.e. the PDOA line and the TDOA hyperbola coincide at infinity.
  • M is the number of elements in the antenna array
  • d is the distance between antenna elements
  • f m is the frequency of the tone
  • c is the speed of light
  • the Cramer-Rao Lower Bound provides a lower bound on the effect of AWGN on the variance, var( ⁇ i k ) , of the estimate, ⁇ i k , of the phase ⁇ ; ⁇ for a tone of
  • var(R I -- ⁇ ) Tone is the variance of the estimate, ' R ; i ..K ,' of the range
  • ⁇ is tlie wavelength of the tone
  • Ai ⁇ k is the amplitude of the tone at the k ⁇ antenna of the i Ul MS
  • Ni is the number of samples (which is directly related to the observation interval T; ,k through where f s is the sampling frequency),
  • Phase offsets The phase of the tone f m is shifted by ⁇ i , . In other words, distorted.
  • the propagation delay % is affected by ⁇ ty k which represents the system delay through the antenna, cables, filters, amplifiers, etc. ⁇ ty c has to be estimated otherwise the propagation delay can be prolonged significantly.
  • multipath, MP ⁇ ft In TDOA, the multipath MPy ⁇ t) is equivalent to extra delay over the propagation channel and has to be either estimated and removed, or mitigated.
  • the effect of multipath is to shift the AOA of ry ⁇ t by some amount depending on the AOA of MPj. k O) and its magnitude.
  • both p(t - respectively i.e. they are both noisy.
  • a more efficient and less noisy method is to cross- correlate p(t - ⁇ yc - with p(f) at the i 01 MS, as mentioned above, then transfer the estimated value of ⁇ y c to the host.
  • p(t) has to be known at the i ⁇ and j ⁇ MSs which places a constraint on p(t).
  • the received wavefront is planar, i.e. Yi.i s ⁇ i, where
  • equation (22) is the fact that there are no ambiguities in equation (22) except for the ⁇ in the solution of ⁇ while equation (23) can have a number of ambiguities depending on the value of the integer k.
  • the noise affects the variance, var( ⁇ l k ) , of ⁇ l k more substantially than it affects the variance, var( ⁇ l k ) , of ⁇ l k
  • R e is 2553meters 2 or equivalently R.
  • i k has a standard deviation of 50.53meters.
  • Solution IV When ⁇ k is estimated indirectly based on the phases of tones in p(t - ti ,k - ⁇ ti c), an integer ambiguity can still exist in the solution unless the wavelength of the selected tones is large with respect to the range between the CT and the k ⁇ antenna at the i ⁇ .MS.
  • the selected tones are discussed below where a solution for the integer ambiguity is presented.
  • processing p(t - ⁇ , k - ⁇ t, ⁇ ) to estimate ⁇ , k we have the following sources of errors:
  • N 0 is the noise Power Spectral Density
  • Equation (26) demonstrates that the bandwidth of the signal plays an important role in the accuracy of the wireless location system.
  • the radio frequency (RF) channels are spaced by 30 KHz which is a relatively small BW compared to systems designed primarily for location such as Global Positioning Systems (GPS) with a BW of 1MHz over Standard Positioning Services (SPS) channels and ISM-based location systems with a typical bandwidth of 10MHz.
  • GPS Global Positioning Systems
  • SPS Standard Positioning Services
  • ISM-based location systems with a typical bandwidth of 10MHz.
  • the location system initially uses a conventional sliding correlator to obtain a set of pseudo-ranges (one pseudo-range per satellite) (see e.g. Spilker, J.J., "GPS Signal Structure and Performance Characteristics," Global Positioning System, Volume I, The Institute of Navigation, Washington D.C., 1980).
  • the pseudo-ranges are then used in multi-lateration to obtain a position fix of the GPS receiver.
  • a typical accuracy for a commercial one point (i.e. no differential reception) GPS receiver with SPS is around 30m RMS without Selective Availability (SA).
  • SA Selective Availability
  • an AMPs land-based location system which initially uses a conventional sliding correlator at each MS to obtain a TOA estimate of the transmitted radio signal followed by a hyperbolic (differential) multi-lateration of all the TOA estimates (processed at some central site) should offer a location accuracy of around an unacceptable 900m RMS assuming no multipath
  • the reason is that (l e correlation function from which a TOA may be estimated has a resolution which is limited to that of the Fourier transform.
  • T c The Observation interval, T c is directly related to the energy Eye in the received signal iy c (t) at the k ⁇ antenna of the I th MS since
  • I ⁇ ffl • interference, I ⁇ ffl: Depending on the level of interference, Ii ,k (f) can have a drastic effect on the accuracy of the estimated phase and may saturate the RF front end of the receiver. Its effects can be mitigated with both analog and digital hardware, as well as adequate software, whether it is in-band or out-of-band.
  • the multipath MPi ,k (t) is equivalent to an extra delay over the propagation channel and has to be either estimated and removed, or mitigated.
  • the estimated time delay, ⁇ c is used to solve for the TDOA between the received signal r ⁇ t) and the received signal r ⁇ Ct)
  • the difference in multipath, MPy c (f) - MP j ⁇ t) is the ⁇ storting factor which has to be mitigated.
  • the cellular frequency band is between 824 and 894 MHz and the propagation characteristics at these UHF frequencies will have a significant impact on positioning by multi-lateration as shown in Parsons D., "The Mobile Radio Propagation Channel, " John Wiley & Sons, New York, 1992. That the ranges measured correspond to Line Of Sight (LOS) distances is a major assumption made when estimating position by multilateration.
  • LOS Line Of Sight
  • the dominant transmission mode in this band is LOS, reflections from natural and man-made objects as well as diffraction around said objects are also possibilities. Multipath and diffraction allow the cellular signal to propagate in heavily built up areas as well as indoors.
  • the measured ranges are longer than the true LOS distance which introduces error into the multilateration process.
  • the propagation distance at UHF is relatively short. This allows frequency reuse in the cellular system but limits the number of observables in the multilateration process. For instance, in a dense urban environment with a delay spread of 3 microseconds (as shown in Hata, M., "Empirical Formula for Radio Propagation Loss in Land Mobile Radio Services," IEEE Transactions on Vehicular Technology, Vol. VT-29, No. 3, August 1980) multipath causes the location accuracy to degrade to more than 1400m RMS.
  • the reason for this is that the correlation function from which the multipath may be estimated has a resolution which is limited to that of the Fourier transform which implies that any multipath within such a resolution is unresolvable using traditional methods. Further processing using an inverse SR algorithm often yields a result with higher multipath resolution as shown by Dumont, L.R., et al., "Super-resolution of Multipath Channels in a Spread Spectrum Location System," IEE Electronic Letters, Vol. 30, No. 19, pp. 1583-1584, September 15, 1994 and as shown by Fattouche et al., U.S. Patent No. 5,570,305 issued Oct., 1996, and as shown by Ziskind, I.
  • the RECC carries data and can be easily monitored. It is used for registering the mobile subscriber with a specific BS, answering pages and for placing calls. It can be used in a TDOA as well as in an Angle-of- Arrival (AOA) and velocity estimation WLS. It consists of a precursor followed by several repeated words that contain information regarding the mobile subscriber and the called number if it is an origination. Therefore, a 911 call can be easily monitored on such a channel.
  • the precursor consists of a dotting sequence (30 bits), a barker code (1 1 bit word sync) and a color code (7 bits).
  • the transmission time for one registration signal is approximately 100 ms: e.g.
  • the RVC carries mainly analog voice, except when the mobile terminal is "audited" by the BS over the forward voice channel (FVC).
  • FVC forward voice channel
  • the mobile terminal is either in the "Waiting For Order” mode or in the "Waiting For Answer” mode and must confirm the order received on the FVC channel by replying with a "blank-and-burst" message.
  • the order can be one of the following:
  • the "blank-and-burst" message is primarily used for hand-offs and also for order confirmations requested by the BS.
  • the message stream consists of a dotting sequence (101 bits), a barker code (11 bits) and several repeated words which are interleaved by a smaller dotting sequence (37 bits) and a barker code. Since the data message is controlled by individual network requests, a non-network integrated wireless location system would have difficulty monitoring the RVC, identifying the mobile subscriber, and determining its location.
  • the Manchester-encoded dotting sequence in the Precursor consists of a one-zero sequence repeated a number of times (30 times). Such a sequence can therefore be approximated using Fourier series, or equivalently, a number of tones can be used to approximate the dotting sequence:
  • the dotting sequence can be expressed as (as shown in Haykin, S. "An Introduction To Analog And Digital Communications, “ John Wiley & Sons, New York 1989): s ( t - t « k
  • DoU ⁇ ng A c Re ⁇ exp[j2 ⁇ f e (t - x l l ) + j ⁇ Dott ⁇ ng(l - ⁇ I ] (29b)
  • ⁇ l k is the propagation delay at the k m antenna of the ⁇ ⁇ MS
  • the dotting sequence can be approximated using tones with phases that can contain location information.
  • the difference between an FM modulated dotting sequence versus an unmodulated dotting sequence is the frequency of the tones approximating the sequence.
  • the fundamental frequency is the carrier frequency, f ⁇ .
  • the fundamental frequency is 5KHz.
  • SAT Supervisory Audio Tone
  • c n is the complex Fourier Coefficient of the FM modulated SAT tone which has even symmetry m its real part and odd symmetry m its imaginary part
  • c n Ac J n ( ⁇ s A ⁇ )
  • J n ( ⁇ sA ⁇ ) is the n ⁇ order Bessel function of the first kind
  • ⁇ SA ⁇ ⁇ /3 and A ⁇ is the amplitude of the earner
  • the carrier frequency corresponds to the first term in (30b) with an amplitude of Ac. This is the term to use for estimating ⁇ in (10) for AOA positioning. It is more difficult to use ⁇ , ⁇ for TDOA positioning due to the fact that there can be a large number of ambiguities depending on the baseline between antennas relative to the wavelength of the carrier. In order to circumvent the large number of ambiguities, the last two terms in equation (30b) can be used together as follows:
  • the Signaling Tone exists over the RVC during either "waiting for answer” mode or "conversation” mode.
  • the ST tone can be expressed as:
  • C n is the complex Fourier Coefficient of the FM modulated ST tone which has even symmetry in its real part and odd symmetry in its imaginary part.
  • for the ST tone can be expressed as the following four terms Ps ⁇ A c -. "l ⁇ f ⁇ >k ) W) - L ' s lST ⁇ A s ( - t l k )
  • sT A c + l ⁇ exp(2 ⁇ f s ⁇ (t - ⁇ i L_ i exp(-2 ⁇ f s ⁇ (t - ⁇ i ⁇ ))
  • the carrier frequency corresponds to the first term in (32b) with an amplitude of A c - This is the term to use for estimating ⁇ i t in (10) for AOA positioning. It is more difficult to use ⁇ i. for TDOA positioning due to the fact that there can be a large number of ambiguities depending on the baseline between antennas relative to the wavelength of the carrier. In order to circumvent the large number of ambiguities, the last two tenns in equation (32b) can be used together as follows:
  • Any voiced speech signal consists of harmonics of a fundamental frequency referred to as the pitch of the speech signal.
  • An equation similar to (30b) or (32b) exists for the voiced speech signal.
  • an equation similar to (31) or (33) also exists for the voiced speech signal. Both equations can be used for positioning a CT.
  • the RECC signal is a cyclo-stationary signal. In other words, it generates a tone when a nonlinear operation is performed over it after FM demodulation. For example, if squared after FM demodulation, a 20KHz tone is generated.
  • the practical descnption of the patent will desc ⁇ be methods and apparatus to estimate ⁇ l k and to mitigate its sources of errors
  • ⁇ 3>n is the clockwise angle between Northing and the line formed by ( 3.nN3 >n ) and (x,y), and
  • f ⁇ ,m - f-,k v/ ⁇ cos( ⁇ - ⁇ ) - v/ ⁇ cos( ⁇ - ⁇ 2,k) (36a)
  • f2,k - f3,n v/ ⁇ cos( ⁇ - ⁇ 2, k ) - v/ ⁇ cos( ⁇ - ⁇ 3 , n ) (36b)
  • Solution V we refer to such a solution as Solution V. Note that in Solution V the position of the CT (x,y) must be known (or estimated) prior to estimated the speed and velocity of the CT, in order to be able to know ⁇ >m , 2 , and ⁇ 3>n in equations (36).
  • Tone frequency ⁇ fi of a tone Tone frequency ⁇ fi of a tone
  • a ⁇ is the amphtude of the tone at the k ⁇ antenna of the 1 th MS
  • Ni is the number of samples (which is directly related to the observation interval Ti jk )-
  • a 2-D (horizontal) location system it is possible to estimate the position of a CT from the range of the CT to at least two MSs.
  • the CT horizontal position estimate is simply the intersection of two horizontal circles with radii equal to the ranges and centered at the MSs. This method of positioning may therefore be called circular multilateration.
  • Ranges may be calculated by subtracting the known time of transmission ⁇ 0 of signal s(f) from the measured TOAs, ⁇ , of signal r ⁇ f).
  • TDOA we refer to the positioning technique as TDOA positioning (which is discussed in the following two sections).
  • Range positioning one way of dete ⁇ nining the time of transmission, ⁇ 0 , is to use the RTD between the BS transmission and the reception of the CT's response to the BS transmission, hi this case, a minimum of two independent equations is required to solve for the two unknowns x and y.
  • TOA positioning there are now three unknowns: x, y and ⁇ o . TOAs from three MSs are required and the equation for the k ⁇ antenna at the i ⁇ MS is
  • ⁇ i k is the Time Of Arrival of signal r i>k (t) at the k ⁇ antenna of the i ⁇ MS
  • std(position) DOP x std(R i k ) (39) where std(R i k ) is the standard deviation of the range estimate
  • DOP Dilution Of Precision which is a measure of geometry.
  • HDOP Horizontal DOP
  • EDOP is the East DOP and is defined as the square root of the element in the 1 st row and 1 st column of CT OA
  • NDOP is the North DOP and is defined as the square root of the element in the 2 nd row and 2 nd column of C TOA _ >
  • C TOA is an unsealed matrix defined as
  • C is the unsealed measurement covariance matrix (the identity matrix of appropriate dimension),
  • A is the design matrix for the model of equation (38) and is defined as
  • 'N.k l N.k and d l k is the best de ⁇ ved distance (range) between the CT and the k m antenna at the 1 th MS.
  • TOA observations thought to be more reliable may be weighted more heavily than those that are deemed less reliable. This is accomphshed through the observation covariance matrix.
  • the inverse of C, is the weight matrix.
  • the RSSI at a MS usually consists of received signal power + received noise power.
  • the noise in the receiver is mainly thermal noise which is a function of bandwidth and temperature.
  • the received noise power is approximately the same in both MSs.
  • a high RSSI imphes a high received signal power, which in turn imphes a high SNR. This is desirable.
  • Blunders are gross errors in the TOA observations. This can be caused by large signal level fluctuations due to either flat fading or sudden in-band interference. If unremoved, blunders cause large errors in the estimated position. It is possible to detect observations containing blunders by observing the misclosure of each observation during the iterative Least Squares process. Misclosure is defined as the value of the position model (38) given the best available position estimate (x,y) . Observations containing blunders will generally have much larger misclosures than observations not containing blunders. When an observation is detected as having a blunder it may be removed from the position estimation process.
  • This patent attempts to reduce the effect of geometry, i.e. reduce the value of HDOP in (40), by allowing a large number of MSs to monitor one CT
  • frequency reuse and flat fading are common occurrences. Therefore, increasing the number of monitoring MSs (which probably reduces HDOP) generally increases std(R i k ).
  • blunder detection is crucial as part of the method of minimizing positional error by maximizing the number of MSs (and hence reducing HDOP) without incurring a large penalty on std(R ; k ).
  • poor SNR at some MSs may cause the inclusion of measurements from those MSs to increase the std(range) more than they reduce HDOP.
  • the invention optimizes the number of MSs used to locate the CT such that std(position) in (39) is minimized.
  • Blunders may also be detected by a statistical analysis of the observation residuals computed from the Least Squares process as shown by Vanicek, P., Krakiwsky, E., "Geodesy: The Concepts " North-Holland Pubhshing Company, Amsterdam, 1982.
  • the residual of each TOA observation may be standardized by its own estimated standard deviation such that the entire set of residuals is assumed to belong to the normal distribution with zero mean and unit standard deviation. If this hypothesis is correct, the standardized residuals should fall within some specified confidence region for the standard normal distribution. An observation whose residual is flagged is suspected of containing a blunder.
  • the 2-D positioning model for hyperbolic multilateration is
  • ⁇ ij,km ⁇ - ⁇ j.m > i ⁇ J or k ⁇ m,and ⁇ ik is the Time Of Arrival of signal r ik (t) at the k ⁇ antenna ofthei* MS.
  • N in (43) is the number of MSs. Note that the TOA at the k ⁇ antenna of the first MS is subtracted from all other TOAs.
  • the unsealed observation covariance matrix is
  • Weighting of the TDOA observations is possible. However, because the TDOAs are a function of two TOAs, the method of assigning weights is no longer straightforward.
  • Blunder detection may also be performed in TDOA positioning.
  • misclosures and residuals correspond to TDOAs. Therefore, a failing misclosure or residual may be due to a blunder in either of the TOA observations from which the TDOA is derived. It is not always possible to isolate the offending MS.
  • Two hyperbola halves, formed from two independent TDOAs, may intersect twice. This results in two mathematically correct solutions. This is particularly true in the case of positioning CTs where short distances and poor geometry are commonplace.
  • Solution bifurcation (the existence of two solutions to the positioning equations) is most often a concern in the exactly determined case.
  • the existence of two solutions can be detected with the method given in Chaffee, J.W. et al., "Bifurcation of Pseudorange Equations," Proceedings of the 1993 National Technical Meeting, San Francisco, California, January 20-22, 1993, The Institute of Navigation.
  • this method is equally applicable to the case of CT positioning.
  • the probability of exact solution bifiircation is extremely small. It is, however, possible for bifurcation to exist for a subset of two TDOAs. In such a case, the second solution may affect the final solution obtained when using all available TDOAs.
  • the iterative Least Squares position estimation algorithm may converge to either of the solutions.
  • the solution converged to is a function of the initial starting position used to begin the iterative Least Squares process.
  • the initial position used to begin Least Squares must be relatively accurate.
  • a closed-form position estimation algorithm using the TOA or TDOA observations, is the only choice. A number of closed-form positioning algorithms have been developed.
  • Bancroft's method Bosset's method
  • Bancroft, S. "An algebraic solution of the GPS equations," IEEE Transactions on Aerospace and Electronic Systems, Vol. AES-21, No. 7, Jan. 1985, pp. 56-59
  • Chan and Ho Choan, Y.T., et al., "A Simple and Efficient Estimator for Hyperbolic Location,” IEEE Transactions on Signal Processing, Vol. 42, No. 8, Aug. 1994, pp. 1905-1915
  • LOCA Lication On the Conic Axis
  • LOCA is used in the preferred embodiment of the invention.
  • LOCA is the mathematical dual of hyperbohc trilateratiOn.
  • the fundamental theorem of LOCA states that TOA differences for three MSs of known location yield a straight line of position. This straight line is the major axis of a conic.
  • the three MSs he on the conic and the CT, the location of which is being estimated, hes at one of the foci of the conic.
  • LOCA is expanded into Plane Intersection as shown by Schmidt, R.O., "A New Approach to Geometry of Range Difference Location," IEEE Transactions on Aerospace and Electronic Systems, Vol. AES-8, No. 6, Nov. 1972, pp. 821-835.
  • Plane Intersection is equally applicable to the case of redundancy in 2-D positioning.
  • LOCA or Plane Intersection may give a very poor solution.
  • this poor solution may cause Least Squares to diverge, fn that case, the best available course of action may be to average the coordinates of the participating MSs and use that as the initial position for Least Squares.
  • Another alternative is to use the approximate coordinates of the MS with which the CT is communicating, as the initial position.
  • TDOAs In some cases it is desirable, or even necessary, to use TDOAs as opposed to TOAs. However, as explained above, it is not always possible to isolate blunders when using TDOAs. It is possible, however, to construct a positioning model that uses TDOAs but gives residuals and misclosures for individual TOAs.
  • R u is the range from the reference (first) antenna of MS j to the position of the CT.
  • the model of (45) has the same structure as that of circular multilateration (equation(38)) except that the third unknown is R u and not the time of transmission.
  • the model of (45) gives N observations, and therefore N residuals and misclosures, for N MSs.
  • the N observations are a 0 and N-l TDOAs.
  • the structure of the equations is that of TOA positioning whereas the observations are that of TDOA positioning. Hence, the name Hybrid TDOA Positioning.
  • the design matrix for hybrid TDOA positioning is
  • the unweighted and unsealed observation covariance matrix, C, is the same as that for TOA positioning, the identity matrix of dimension N.
  • DOPs may be calculated, as before, from JA ⁇ C I _1 Aj .
  • the observations are, strictly speaking, TDOAs, they may be treated as observations corresponding to the individual MSs. That is, the first observation, which is always zero, may be viewed as the observation of the reference (or first) MS.
  • the second observation consisting of the TOA of the reference MS subtracted from the TOA of the second MS, is treated as the observation of the second MS, and so on. Therefore, the N diagonal elements of C, may be weighted for the individual MSs.
  • N independent misclosures and residuals are available for analysis. Blunder detection may then be performed as in the case of TOA positioning and blunders in individual TOA observations may be detected.
  • Least Squares may be used to obtain a unique solution.
  • the unsealed and unweighted observation covariance matrix, C, is the identity matrix of dimension N.
  • the DOPs can again be found from A T C,- A] .
  • the individual AOA observations may be weighted through the observation covariance matrix C, . Those AOA observations deemed more reliable are assigned a smaller variance, or conversely, a heavier weight.
  • AOA observations may contain blunders.
  • statistical testing of the observation residuals and misclosures may be used to detect observations which contain blunders.
  • the estimated AOA is the elevation angle.
  • both diversity antennas since they are independent from each other, i.e. they offer independent observations.
  • the simplest method to use both observations is by combining them using: selection combining, maximal ratio combining, co-phasing combining, equal gain combining, or other methods of combining.
  • Least Squares allows for the combination of different types of observations. In particular, it is possible to estimate 2-D position using both AOA observations and TDOA observations within a single Least Squares adjustment.
  • a combination of the two different observation types is particularly useful in situations where only two MSs are available for estimating the 2-D position of a CT.
  • two antennas at a particular MS are used to estimate the mcoming signal AOA for that MS, numerous AOA ambiguities are possible as shown in equation (15). This is due both to the nature of AOA estimation with a 1-D linear array, and to the fact that the spacing between elements can be greater than one wavelength. Therefore, with two MSs and AOA observations only, many position solutions are possible and there is no way of determining which of the many solutions is correct.
  • TDOA can be calculated. This TDOA corresponds to a hyperbola side which, in the absence of error, will cross through the intersection point of two of the many bearing lines derived from the ambiguous AOAs.
  • each AOA combination is combined with the TDOA observation in Least Squares. That combination of AOAs which results in the smallest sum of squares of residuals is chosen as correct. The corresponding position solution is used as the CT position estimate.
  • both the model for AOA positioning (47) and the model for TDOA positioning (42) are used.
  • the design matrix A for two AOA observations (one at each of two MSs) and one TDOA observation (for the same two MSs) is
  • the first two rows correspond to the two AOA measurements whereas the third row corresponds to the TDOA measurement.
  • the two columns correspond to the two unknowns, x and y. Additional AOA and TDOA measurements may be included by adding appropriate rows to (49). Note that the 1/c factor seen in (43) is missing in the TDOA measurement row of (49).
  • the misclosure vector necessary for the Least Squares adjustment mechanism, merely consists of the misclosures of all observations.
  • the misclosure vector corresponding to the design matrix of (49) is
  • the unsealed observation covariance matrix is the identity matrix of appropriate dimension (number of AOA observations plus the number of TDOA observations).
  • DOP may again be used to quantify geometry.
  • the DOPs (HDOP, EDOP,
  • NDOP NDOP
  • the individual AOA and TDOA observations may be weighted through the observation covariance matrix C j . Those AOA and/or TDOA observations deemed more rehable are assigned a smaller variance, or conversely, a heavier weight.
  • Both the TDOA and AOA observations may contain blunders.
  • Statistical testing of the observation residuals and misclosures may be used to detect observations which contain blunders.
  • the range, R j from the CT to the 1 th MS is the observed parameter.
  • AOA and TOA positioning may also be combined in order to estimate the position of the CT with as little as two MSs.
  • the design matrix A for two AOA observations (one at each of two MSs) and two range observations (one for each of the same two MSs) is
  • the misclosure vector corresponding to this design matrix is
  • the unsealed observation covariance matrix is the identity matrix of appropriate dimension (number of AOA observations plus the number of range observations).
  • DOP may again be used to quantify geometry.
  • the DOPs (HDOP, EDOP,
  • NDOP NDOP
  • the individual AOA and range observations may be weighted through the observation covariance matrix C ⁇ . Those AOA and/or range observations deemed more rehable are assigned a smaller variance, or conversely, a heavier weight.
  • Both the AOA and range observations may contain blunders.
  • Statistical testing of the observation residuals and misclosures may be used to detect observations which contain blunders.
  • the 3-D or 2-D location of the moving CT must be estimated at various epochs of time.
  • the doppler shift of the signal arriving at each MS may be estimated as discussed earlier.
  • the equations relating the frequency (including Doppler shift) of the arriving signal at the MS to the CT speed, DOT and frequency offset are given in equations (35).
  • Geometry affects the estimation of speed and DOT as well. For instance, it is intuitively obvious that when the CT is traveling on a line perpendicular to the line connecting it and an MS, no information regarding the speed of the CT is available from observed data at that MS.
  • the DOPs can again be found from
  • the DOPs will be speed DOP, direction of travel DOP, and frequency offset DOP.
  • C j is the unsealed arid unweighted identity matrix of dimension N.
  • the invention When using the RECC channel, the invention consists of the following procedure.”
  • Procedure I 1. initiating a call to the designated CT by the Host;
  • Procedure I assumes no knowledge of the designated MS (or equivalently assumes no knowledge of either the FOCC channel or its corresponding RECC channel).
  • This has two shortcomings: i.
  • Each MS has to contain at least three RECC receivers, one for the RECC channel designated to that cellular Base Station (BS) and two for the neighboring BSs that can receive at an acceptable level, ii.
  • the procedure suffers from the fact that the probability of missing target is nonzero, i.e. a neighboring MS will occasionally fail to acquire r ijk (t).
  • Procedure II An alternative procedure, Procedure II, that attempts to locate a powered-up AMPs-CT, assumes knowledge of the designated MS.
  • the invention consists of the following procedure: Procedure II:
  • Each MS is required to contain only one tunable RECC receiver.
  • n The probability of missing target is somewhat reduced given that each MS has prior knowledge of the status of the CT and of its identity.
  • Procedure II is based on the assumption that the servicing BS is known a priori. This is possible using the following procedure: Procedure III:
  • Procedure II should ensure that the call is dropped by the Host prior to having an alert signal uttered, i.e. prior to having the CT audibly ring.
  • Procedures I, II and III should have the MSs co-located in the cellular BSs and the communications network based on the existing link between BSs and Mobile Telephone Switching Office (MTSO).
  • MTSO Mobile Telephone Switching Office
  • the patent does not require the MSs to be collocated in the cellular BSs.
  • the required processing consists of correlating the RECC signal with a clean version of itself and sending the information regarding the correlation peaks to the Host, instead of performing a cross-correlation between each pair of received RECC signals at the Host.
  • the required processing consists of correlating the RECC signal with several clean versions of the RECC signal at different frequencies and sending the information regarding the correlation peaks to the Host.
  • the correlation peaks between r,- k (t) and a clean version of itself can be super- resolved using SR algorithms. It is sometimes preferable to perform the SR algorithms at the Host rather than performing them at the MS since it requires a number of computationally intensive operations that are easier to develop at the Host than at the MS. This implies that the correlation peak needs to be transferred to the Host which does not represent a large amount of information and can be easily transferred to the Host.
  • diversity antennas or sectored antennas or both can be used for PDOA positioning.
  • Diversity signals can also be used to improve the SNR of the RECC signal by combining the two either through selection combining, Maximal Ratio Combining, or co-phasing combining.
  • DSP Digital Signal Processor
  • the tone can have a duration of up to 125msec. and a frequency of twice the symbol rate, i.e. a frequency of 20kHz; the phase of the tone is directly related to the TOA or the AOA of the signal.
  • the nonlinear operation can be either a quadratic operation (e.g. squaring the signal) or a delay product operation (i.e. multiplying the signal by a delayed version of itself).
  • Procedure IV can be used both for acquiring the RECC signal and for estimating its TOA. This is accomplished by stamping the time using a reliable clock at either the start of the generated tone or obtaining the time stamp at the end of the observation window (the latter is preferred).
  • Procedure IV can be improved by resolving the generated tone using SR gorithms. Moreover, the filtering required in step 1 of Procedure IV can be carried out in the digital domain in order to reduce the effect of temperature and aging on group delay variation.
  • Procedures I and II can be improved by repeating them a number of times and then averaging the location information (e.g. the TDOA, PDOA or FDOA between pairs of MSs).
  • location information e.g. the TDOA, PDOA or FDOA between pairs of MSs.
  • Procedures I and II can be increased by repeating the procedures a number of times until at least 3 MSs have an acceptable signal level. This does not have to occur simultaneously between 3 MSs.
  • the invention intends to select and combine only acceptable samples from each trial. This feature is unique to the invention.
  • a powered-iip CT can also be tracked by repeatedly following Procedures I or II. This feature is unique to the invention.
  • Procedure V When using the RVC channel, the invention consists of the following steps: Procedure V:
  • step 5 the notification can be performed by the Host and the observation interval, T ⁇ , can coincide with the "waiting for answer” mode.
  • Procedure V can be improved by taking several samples of the signal r_ k (t) during a number of observation intervals while the phone is in the "waiting for answer” mode; then, averaging the location estimate over all samples.
  • Procedure V can be improved by repeating it a number of times and then either averaging the location information or averaging the TDOA, PDOA or FDOA between pairs of MSs. This should be done while keeping in mind that the alert signal (i.e. audible ringing) is either avoided or mi ⁇ dmized.
  • a suitable manner to process the signal rj )k (t) generated by the phone over the assigned RVC channel in order to estimate the POA of the RVC signal (as stated in step 5 of Procedure V) is to use the following procedure:
  • the tones that are known to exist over the RVC channel are either the SAT tone or the ST tone.
  • the ST tone is preferable since it has a larger SNR than the SAT tone.
  • the ST tone is only available in some situations depending on the selected network options.
  • Procedure VI can be improved by resolving the selected tone using SR algorithms. Moreover, the filtering required in step 1 of Procedure VI can be carried out in the digital domain in order to reduce the effect of temperature and aging on group delay variation.
  • the invention intends to use narrowband digital filters of few hertzs of bandwidth (e.g. Fourier Transform-based filters, sliding Fourier Transform-based filters, IIR filters, FIR filters, etc.).
  • the Fourier Transform- based filter has a bandwidth which is a function of the observation duration
  • the IIR filter has a steady state response time which is a function of Ty c .
  • the observation duration, T ⁇ has to be selected in order to optimize the SNR (increase it) versus the bandwidth of the filter (decrease it) versus the response time of the wireless location system (minimize it).
  • the invention intends to resolve the different Doppler frequencies ⁇ fj ⁇ (which correspond to different TOAs and different AOAs) and to choose the frequency corresponding to the first arrival.
  • the method of resolvmg the different frequencies can be accomplished using SR algorithms. It is also possible to locate a CT during "conversation" mode, i.e. when there is voice activity over the RVC channel. This can be achieved by estimating the pitch of the voice signal and extracting its phase information using Procedure VI.
  • a CT during "conversation" mode, without having to process the voice signal itself. This can be done by waiting for quiet periods of time when the voice signal is not used, which happens approximately 60% of the time during a conversation.
  • the MS can follow hand-offs as the CT travels between cells which is a unique feature of the invention whereby a CT can be tracked over the duration of a conversation.
  • RECC channel or the RVC channel.
  • the invention consists of the following steps:
  • Procedure VII is a subset of Procedure I above and assumes no knowledge of the designated MS. This has several shortcomings.” i. Each MS has to contain at least three RECC receivers, &ne for the RECC channel designated to that BS and at least two for the neighboring BSs that can receive r; k (t) at an acceptable level. ii. The procedure suffers from the fact that the probability of missing target is nonzero, i.e. a neighboring MS will occasionally fail to acquire r ⁇ t) since the probability of acquisition is below 100%. iii. When a call is operator-assisted, it is difficult to identify the called party.
  • Procedure VHT When using the RVC channel, the invention consists of the following steps: Procedure VHT.
  • Procedure VIII can be improved by taking several samples of the signal ri k (t) at the k ⁇ antenna of the ifh MS over a number of observation intervals Ty c while the phone is in the "unanswered conversation" mode; then, averaging the location estimate over all samples.
  • Procedure VIII An important feature for an E911 wireless location system is the time it takes to locate a 911 caller. With Procedure VIII above, it is possible to obtain a location while the phone is in the "unanswered conversation" mode which imphes that the location information can be made available to the Public Safety Answering Point (PSAP) by the time the 911 call is answered. Another important feature in Procedure VIII is the fact that the probability of location is 100%., unlike Procedure VII which is below 100%.
  • PSAP Public Safety Answering Point
  • Procedure VIII Yet another important feature in Procedure VIII is the fact that the signal s(t) transmitted by the CT during the "unanswered conversation" mode is in fact a deterministic signal, i.e. a clean replica of the signal can always be available at each MS. More specifically, as mentioned above, s(t) partially consists of either a SAT tone or an ST tone during the "unanswered conversation" mode. In this case, TOA and AOA information are contained in the phase of the tone and can be extracted using Procedure VI while the FOA information are contained in the frequency of the tone and can be extracted using Procedure X.
  • the duration of observation can be increased substantially in order to accommodate different situations.
  • the SNR can be increased by increasing the duration of observation.
  • the geometry i.e. HDOP is large, e.g. highway
  • Ty ⁇ hence, increasing the number of MSs that receive the signal ry ⁇ t
  • increasing the number of MSs also leads to reducing the effect of multipath, particularly in urban centers.
  • Procedure VTII can be improved by resolving the tone using SR algorithms.
  • the filtering required in step 1 of Procedure VI can be carried out in the digital domain in order to reduce the effect of temperature and aging on group delay variation.
  • the invention intends to use narrowband digital filters of few hertzs bandwidth (e.g. Fourier Transform-based filters, sliding Fourier Transform-based filters, HR filters, FIR Filters, etc.).
  • the Fourier Transform- based filter has a bandwidth which is a function of the observation duration, Ti,k-
  • the HR filter has a steady state response time which is a function of Ti > .
  • the observation duration, T; (k ) has to be selected in order to optimize the SNR (increase it) versus the bandwidth of the filter (decrease it) versus the response time of the wireless location system (minimize it).
  • the MSs can follow the hand-offs of the CT by the BSs as the CT travels between cells in a kinematic location system, or alternatively, it can average the location information or the TDOA, PDOA or FDOA information in a static location system. This feature of tracking a CT over the duration of a conversation is unique to the invention.
  • the invention intends to resolve the different Doppler frequencies (which correspond to different TOAs and different AOAs) and choose the frequency corresponding to the first arrival.
  • the method of resolving the different frequencies can be accomphshed using SR algorithms.
  • the invention intends to use a linear IF-sampling receiver for the RVC channel and the RECC channel.
  • the IF-sampling receiver at the 1 th MS is designed to have high rejection, low group delay variation and good sensitivity.
  • the receiver is designed to have (see Figure 8): Design I:
  • Initial rejection is achieved at RF using an RF Band Pass Filter (BPF) (802), followed by an RF amplifier (803) for good sensitivity.
  • BPF Band Pass Filter
  • Subsequent rejections are achieved at each IF stage which consist of a mixer (804) followed by an Intermediate Frequency (IF) BPF filter (805) and an IF amplifier (806).
  • the sampling rate is intended to be below the Nyquist rate in order to force aliased copies of the IF signal (807) close to a lower digital IF, f 2 .
  • DDC Digital Down Converter
  • Procedure IX Since ⁇ t; >k is a function of frequency, it can vary significantly from one frequency to another. Furthermore, according to the AMPs standard, ⁇ fi ⁇ can be as large as 2kHz. For this reason, it is important to force the estimation of ⁇ t ⁇ in step 1 of Procedure IX to be independent of the carrier offset, ⁇ f;_ k + ⁇ fij ⁇ . This is accomphshed by estimating the carrier offset, ⁇ f ⁇ + ⁇ fi , , in step 2 of Procedure IX and removing it in step 3 of Procedure IX prior to processing it for location purposes.
  • steps 2 and 3 force the overall group delay, ⁇ t ⁇ , to remain similar to its original characterization in step 1 above, thereby reducing overall group delay variations due to frequency offsets.
  • step 1 in Procedure IX has to be performed on a regular basis.
  • step 1 can be performed as part of a calibration procedure described below in Procedure XI.
  • step 2 can be performed using a discrete Carrier Recovery Loop (CRL) described in Procedure X.
  • CTL Carrier Recovery Loop
  • step 3 can be performed using a Direct Digital Synthesiser (DDS) (809).
  • DDS Direct Digital Synthesiser
  • the discrete Carrier Recovery Loop consists of several steps that are repeated a number of times until a satisfactory level of performance is reached: Procedure X:
  • step 3 can be performed using a gradient-type search algorithm or any other suitable search algorithm.
  • step 4 can be performed using either a DDS (809) only or a DDS and a Digital Down-Converter (DDC) (815). If a DDS (815) only is used in step 4, then step 1 in Procedure X processes a new segment of the signal, ⁇ k (t), every iteration. If a DDS (809) and a DDC (809) are used is step 4, then step 1 in Procedure X processes the same stored segment of the signal, r ⁇ t), every iteration until the DDS (809) is used. It is preferred to use both the DDC and the DDS in order to reduce the effect of finite precision arithmetic on the estimation process.
  • DDC Digital Down-Converter
  • the DSP (817) in step 1 of Procedure X of the carrier recovery loop can consist of a digital notch filter centered at the desired IF frequency f 2 , whose power of response is to be minimized, i.e. f ⁇ - is the response of the digital notch filter.
  • the notch filter can consist of
  • the Band Pass filters can be implemented using ⁇ real) digital Biquadratic filters.
  • the DSP (817) in step 1 in Procedure X of the carrier recovery loop can consist of a digital Band Pass Filter centered at the desired IF frequency f 2 , whose power of response is to be maximized, i.e. fo bj is the response of the Band Pass Filter.
  • the BPF can be implemented as a (complex) 1 st order (or higher) digital ITR filter.
  • the signal to process is a baseband signal (816) and the digital BPF turns into a simple (complex) LPF.
  • a simple (complex) LPF is an averaging filter which adds all real samples together and all imaginary samples together over the observation interval.
  • the invention intends to use a common reference for all the LOs and for all the clocks.
  • a suitable common reference for the LOs and for the clocks can be derived from the GPS signal. Given that all LOs in the MSs have a common reference implies that
  • a wireless location system has to be cahbrated prior to operation (and occasionally during operation) in order to remove the effect of the overall Group Delay, t ⁇ , at each MS. Moreover, temperature and aging can cause the overall Group Delay to change with time. Therefore, it is necessary to calibrate the system on a regular basis.
  • a method to calibrate a wireless location system is as follows: Procedure XI:
  • Procedure XI can be repeated a number of times in order to average the relative group delay over time.
  • the invention intends to store a CT inside a number of MSs,. This allows for automatic calibration without a need for human intervention.
  • SAW filters As the BPF (803, 805, 811) in Figure 8. It is also recommended to place the SAW filters (803, 805, 811) in a metallic block to minimize flexing effects due to temperature variations.
  • the invention intends to either
  • a method to force the CT to use several channels consists of repeating Procedures I, II or V several times in the hope that the channel (either RECC or RVC) changes from time to time.
  • the RVC channel has a better chance to change from time to time than the RECC channel.
  • a unique feature of the patent is the fact that it has a 100% probabihty of acquisition.
  • the Host can order a large number of MSs to tune to the assigned RVC in Procedure V, thereby generating a large redundancy in the observations. This is not necessarily useful when an observation has a blunder in it.
  • a large number of observations imphes a small HDOP. Therefore, the Host is required to optimize the number of observations in order to m imize the positional error of the CT.
  • Figures 9 illustrate the preferred embodiment for adjusting the observed TOAs such that the sum of the squares of the residuals is a rninimum.
  • Other methods for adjusting the observed TOAs such that the sum of the squares of the residuals is a minimum are available including:
  • the positioning process begins with a set of TOA observations from a minimum of three MSs. If only three TOAs are available (901), solution bifurcation is tested for (902). In the event of solution bifurcation, the LOCA algorithm (903) is performed on the TOA observations yielding two solutions. These two solutions are each used as the initial position for Least Squares (904 and 905) resulting in two Least Squares solutions for the CT.
  • the Least Squares algorithm here, and in all other parts of Figure 9, is Hybrid TDOA positioning with received signal strength used to weight the individual MS observations. During every iteration of Least Squares, misclosures for each MS are calculated. If any misclosure exceeds some multiple of the RMS value of the entire set of misclosures, the corresponding MS, and its TOA, is no longer used within that particular execution of Least Squares.
  • both Least Squares solutions (904 and 905) converge (906) but are not equal (907)
  • both Least Squares solutions are reported as possible positions for the CT (908). If the either of the LS solutions diverge (906) or the convergent solutions are equal (907), the two LOCA solutions from (903) are reported as possible positions of the CT (909).
  • Plane Intersection (912) (or any other closed-form position estimation algorithm) is executed.
  • the resulting solution is used as the initial position for Least Squares (913).
  • a check is made as to whether Least Squares (913 or 911) converged (914). If Least Squares converges, another check for observational redundancy is made (915). If there is no redundancy, the Least Squares solution is reported as the position estimate of the CT (923). If there is redundancy, the normalized residuals are statistically tested for normality (916). The Least Squares solution is reported (923) should all residuals pass. If any residuals fail, the redundancy numbers of the failing observations are checked ( 17). The redundancy number of the 1 th observation is defined as
  • C ⁇ r is the covariance matrix of the residuals and is defined as
  • this threshold is 0.5
  • the Least Squares solution is reported as the CT position estimate (923).
  • Least Squares is executed again but with the average of participating MSs coordinates used as the initial position (918). If Least Squares now converges (919) but there is no observation redundancy (920), the newly convergent Least Squares solution is reported as the position estimate of the CT (923). If there is redundancy (920), the standardized residuals are tested for normality (921). Should all residuals pass, the newly convergent Least Squares solution is reported (923). If some of the residuals fail but none of the corresponding observations have redundancy numbers greater than some threshold (922), the newly convergent Least Squares solution is reported (923).
  • the communication between the Host and the customer can be achieved over it.
  • a CT calls 911 for emergency
  • a powered-on CT is to be located by a customer
  • its positional information can be relayed from the Host to the customer through the internet.
  • CT location information residing at the Host can be integrated with third-party information (i.e. a map database, or a database consisting of geo-coded business addresses such as restaurants, towing companies, etc.) residing in some other geographical location, perhaps even in another country.
  • third-party information i.e. a map database, or a database consisting of geo-coded business addresses such as restaurants, towing companies, etc.
  • the combination of this CT location information with the third party information can be transferred over the internet to allow customers to locate a particular CT wrt to either a map location (i.e.
  • the service provider will integrate together the various components including the CT location information derived from the wireless location system and the third-party information database.
  • the integration process of the different databases is transparent to the customer.
  • the customer will only know that the location- based service exists as such to bring all of the different components together to provide for a complete service which can be offered either on a regional, national or perhaps global basis.
  • these location-based services can now be offered on an economical basis to the customer. Examples of such services are fleet management, concierge services, roadside assistance, child find services, etc. Legality and security aspects are a concern on the internet and a dedicated link might be sometimes necessary.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

Cette invention porte sur la production d'un système de positionnement sans fil basé sur un réseau, dans lequel les téléphones cellulaires (CT) à accès multiple par répartition en fréquence (AMRF) répondant au système AMPS (Advanced Mobile Phone System : service téléphonique mobile perfectionné) peuvent être localisés de manière passive sans modification des téléphones cellulaires ou de l'infrastructure de l'antenne cellulaire. De manière plus spécifique, cette invention concerne des procédés et un dispositif permettant d'estimer la position et la vitesse d'un téléphone cellulaire à partir du temps d'arrivée (TOA) d'un signal émis par le téléphone (CT), de sa phase d'arrivée (POA), de sa fréquence d'arrivée (FOA) ou d'une combinaison de ces paramètres, mesurés dans plusieurs antennes et dans différents sites de surveillance (MS). Le détermination des coordonnées du téléphone cellulaire (CT) est réalisée soit par une multilatération hyperbolique fondée sur la différence des temps à l'arrivée, soit par une multiangulation linéaire fondée sur la différence de phase à l'arrivée, soir par ces deux approches combinées. La vitesse du téléphone cellulaire (CT) est déterminée à partir de la fréquence d'arrivée (FOA) définie en fonction de la différence de fréquence à l'arrivée. Un aspect important de cette invention réside dans la manière dont le téléphone cellulaire est forcé d'émettre des signaux radio à des fins de positionnement. Un autre aspect concerne l'application de techniques de super-résolution pour augmenter la résolution des paramètres temps d'arrivée, phase d'arrivée ou fréquence d'arrivée. Un troisième aspect concerne l'utilisation de procédés d'échantillonnage F.I. dans les récepteurs de chaque site de surveillance (MS) afin de réduire les effets des bruits et des interférences sur la précision du système de positionnement sans fil.
PCT/CA2000/000103 1998-08-06 2000-02-04 Systeme de positionnement sans fil base sur un reseau permettant de localiser des telephones cellulaires amps (amrf) WO2001058195A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU25277/00A AU2527700A (en) 2000-02-04 2000-02-04 A network-based wireless location system to positon amps (fdma) cellular telephones

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US13072498A 1998-08-06 1998-08-06
US13040298A 1998-08-06 1998-08-06
US13062398A 1998-08-06 1998-08-06
US09/130,637 US6330452B1 (en) 1998-08-06 1998-08-06 Network-based wireless location system to position AMPs (FDMA) cellular telephones, part I

Publications (1)

Publication Number Publication Date
WO2001058195A1 true WO2001058195A1 (fr) 2001-08-09

Family

ID=27494857

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA2000/000103 WO2001058195A1 (fr) 1998-08-06 2000-02-04 Systeme de positionnement sans fil base sur un reseau permettant de localiser des telephones cellulaires amps (amrf)

Country Status (2)

Country Link
DE (1) DE19936846A1 (fr)
WO (1) WO2001058195A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004008795A1 (fr) * 2002-07-10 2004-01-22 Ekahau Oy Technique de positionnement
US7706328B2 (en) 2006-01-04 2010-04-27 Qualcomm Incorporated Methods and apparatus for position location in a wireless network
US8165064B2 (en) 2008-01-28 2012-04-24 Qualcomm Incorporated Enhancements to the positioning pilot channel
US9609070B2 (en) 2007-12-20 2017-03-28 Corning Optical Communications Wireless Ltd Extending outdoor location based services and applications into enclosed areas
WO2020074070A1 (fr) * 2018-10-09 2020-04-16 Nokia Technologies Oy Système et procédé de positionnement
EP4145712A1 (fr) * 2021-09-03 2023-03-08 Rohde & Schwarz GmbH & Co. KG Système et procédé de balayage de fréquence radio pour le test de réseau mobile
US12003045B2 (en) 2021-10-20 2024-06-04 Samsung Electronics Co., Ltd. Wireless interconnect for high rate data transfer

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010014108A1 (de) * 2010-04-07 2011-10-13 Rohde & Schwarz Gmbh & Co. Kg Verfahren und System zur Ortbestimmung einer ein elektromagnetisches Signal aussendenden Vorichtung
WO2011160698A1 (fr) * 2010-06-25 2011-12-29 Innovationszentrum für Telekommunikationstechnik GmbH IZT Système et procédé de détermination d'une position
CN103634903B (zh) * 2013-11-22 2016-08-31 中国人民解放军理工大学 低功耗小型设备抗噪定位方法
EP3637126A1 (fr) * 2016-01-05 2020-04-15 Elta Systems Ltd. Procédé de localisation d'une source de transmission dans un environnement à trajets multiples et système correspondant

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5890068A (en) * 1996-10-03 1999-03-30 Cell-Loc Inc. Wireless location system
WO1999033287A2 (fr) * 1997-12-23 1999-07-01 Bellsouth Intellectual Property Corporation Procede et systeme de transmission d'informations a un telephone cellulaire

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5890068A (en) * 1996-10-03 1999-03-30 Cell-Loc Inc. Wireless location system
WO1999033287A2 (fr) * 1997-12-23 1999-07-01 Bellsouth Intellectual Property Corporation Procede et systeme de transmission d'informations a un telephone cellulaire

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
KRIZMAN K J ET AL: "WIRELESS POSITION LOCATION: FUNDAMENTALS, IMPLEMENTATION STRATEGIESAND SOURCES OF ERROR", IEEE VEHICULAR TECHNOLOGY CONFERENCE,US,NEW YORK, IEEE, vol. CONF. 47, 4 May 1997 (1997-05-04), pages 919 - 923, XP000736742, ISBN: 0-7803-3660-7 *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004008795A1 (fr) * 2002-07-10 2004-01-22 Ekahau Oy Technique de positionnement
US7299059B2 (en) 2002-07-10 2007-11-20 Ekahau Oy Positioning technique
US7706328B2 (en) 2006-01-04 2010-04-27 Qualcomm Incorporated Methods and apparatus for position location in a wireless network
US8489124B2 (en) 2006-01-04 2013-07-16 Qualcomm Incorporated Methods and apparatus for position location in a wireless network
US9008700B2 (en) 2006-01-04 2015-04-14 Qualcomm Incorporated Methods and apparatus for position location in a wireless network
US9609070B2 (en) 2007-12-20 2017-03-28 Corning Optical Communications Wireless Ltd Extending outdoor location based services and applications into enclosed areas
US8165064B2 (en) 2008-01-28 2012-04-24 Qualcomm Incorporated Enhancements to the positioning pilot channel
WO2020074070A1 (fr) * 2018-10-09 2020-04-16 Nokia Technologies Oy Système et procédé de positionnement
EP4145712A1 (fr) * 2021-09-03 2023-03-08 Rohde & Schwarz GmbH & Co. KG Système et procédé de balayage de fréquence radio pour le test de réseau mobile
US12003045B2 (en) 2021-10-20 2024-06-04 Samsung Electronics Co., Ltd. Wireless interconnect for high rate data transfer

Also Published As

Publication number Publication date
DE19936846A1 (de) 2000-04-06

Similar Documents

Publication Publication Date Title
US6330452B1 (en) Network-based wireless location system to position AMPs (FDMA) cellular telephones, part I
US6266014B1 (en) Methods and apparatus to position a mobile receiver using downlink signals part IV
US6204812B1 (en) Methods and apparatus to position a mobile receiver using downlink signals, part II
US6208297B1 (en) Methods and apparatus to position a mobile receiver using downlink signals, part I
US5890068A (en) Wireless location system
WO2000069198A1 (fr) Systeme de localisation sans fil
US6765531B2 (en) System and method for interference cancellation in a location calculation, for use in a wireless location system
US6891500B2 (en) Method and apparatus for geolocating a wireless communications device
Reed et al. An overview of the challenges and progress in meeting the E-911 requirement for location service
KR100881946B1 (ko) 무선 로케이션 시스템의 ｔｄｏａ 및 ｆｄｏａ를 추정하기 위한 향상된 방법
AU2003218341B2 (en) Automatic sequential tuning of narrowband receivers of a wireless location system for voice/traffic channel tracking
AU2004230702B2 (en) Multiple pass location processor
US6483460B2 (en) Baseline selection method for use in a wireless location system
WO2001065271A1 (fr) Procedes et dispositif de positionnement de recepteur mobile a l'aide de signaux de liaison descendante
US20040102196A1 (en) Location method and system
CA2360130C (fr) Synthese de largeur de bande, destinee a un systeme sans fil de localisation
Mizusawa Performance of hyperbolic position location techniques for code division multiple access
WO2001058195A1 (fr) Systeme de positionnement sans fil base sur un reseau permettant de localiser des telephones cellulaires amps (amrf)
Klukas Cellular telephone positioning using GPS time synchronization
US20050176443A1 (en) Cellular phone geolocation system
KR101855378B1 (ko) 이종망 이동통신을 이용한 무선 측위 방법
Reddy et al. Two base station method for finding location of mobile vehicles based on Doppler shifted signals
Buchanan et al. Location services
Krishnamurthy et al. Position location technologies for wireless systems
MXPA01006907A (en) Bandwidth synthesis for wireless location system

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AL AM AT AU AZ BA BB BG BR BY CA CH CN CR CU CZ DE DK DM EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG US US US US UZ VN YU ZA ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase