WO2002004975A1 - Systeme de balises de zone locale destine a la determination de position - Google Patents

Systeme de balises de zone locale destine a la determination de position Download PDF

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Publication number
WO2002004975A1
WO2002004975A1 PCT/US2001/020066 US0120066W WO0204975A1 WO 2002004975 A1 WO2002004975 A1 WO 2002004975A1 US 0120066 W US0120066 W US 0120066W WO 0204975 A1 WO0204975 A1 WO 0204975A1
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WIPO (PCT)
Prior art keywords
beacon
receiver
code
beacon signal
time
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Application number
PCT/US2001/020066
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English (en)
Inventor
Keith J. Brodie
Original Assignee
Sirf Technology 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
Application filed by Sirf Technology Inc filed Critical Sirf Technology Inc
Priority to AU2001268703A priority Critical patent/AU2001268703A1/en
Publication of WO2002004975A1 publication Critical patent/WO2002004975A1/fr

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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
    • G01S5/10—Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements, e.g. omega or decca systems

Definitions

  • the invention relates generally to position determination of objects within a local area and more particularly to a system for and a method of determining the location of objects within a locally defined area using a beacon system.
  • Such local areas may be either indoor, outdoor or a combination of both.
  • ground service fleets comprising mobile vehicles, cargo trailers, stairs, mobile service elevators, etc. that are moving throughout the airport region.
  • Obj ects comprising the ground service fleet occasionally collide with each other and with aircraft moving to and from gates. Obviously, these are expensive and dangerous mishaps.
  • Another exemplary situation in which location information on moving objects is highly desirable is a burning building with a group of firefighters inside of it. If a firefighter is lost in the smoke and debris, he may be impossible to locate. If the scene commander has a picture of all of the firefighter's locations he can optimize their deployment to protect their lives and save victims and property.
  • An obvious solution to this problem is the use of the Global Positioning System
  • GPS Globalstar Navigation Satellite System
  • a location determination tool As a location determination tool, however, may be cost prohibitive in certain situations wherein hundreds of objects are within a local area. In other situations, such as the previously described indoor firefighting situation, the use of the GPS may precluded due to signal blockage. Hence, those concerned with knowing the location of objects within a local area have recognized a need for a cost effective location determination system that operates independent of the GPS. This invention fulfills those needs and other.
  • the present invention relates to a system for determining the location of a plurality of objects within a local area.
  • the system includes, for each object, a beacon carried by the object for transmitting a beacon signal at a random time.
  • the basic system further includes at least three receivers located within the local areas for receiving each beacon signal and recording the time of arrival of each beacon signal with a local clock.
  • the system also includes a base station for receiving data indicative of the time
  • each beacon transmits its beacon signal over the same carrier frequency.
  • multiple beacon signals are carried over the same carrier frequency through the use of at least one of time-division
  • each receiver separates the multiple beacon signals by at least one of time-division multiplexing and 5 code-division multiplexing.
  • the beacon signal comprises a beacon code burst comprising a family code and a beacon-identification code.
  • the family code is added to the beacon signal by phase shift keying.
  • each receiver correlates a replica of the family code with the family code 0 of the received beacon signal to detect the arrival of a beacon signal.
  • the invention relates to a method of determining the location of the plurality of obj ects within a local area. The method includes the steps of transmitting a beacon signal at a random time from each object within the local area.
  • the method also includes the step of receiving each beacon signal at at least three receivers located within the local areas 5 and at each receiver, recording the time of arrival of each beacon signal with a local clock.
  • the method further includes the step of processing the difference in the time of arrival of the beacon signal at each of the receivers to determine the location of the beacon within the local area.
  • each receiver comprises a GPS receiver and the 0 method further comprises the step of synchronizing the receiver local clocks by transferring
  • each receiver comprises a GPS receiver and the method further comprises the step of synchronizing the receiver local clocks using differential GPS processing with a common set of corrections.
  • the method further includes the step of synchronizing the receiver local clocks using send and reply correction messages from a master clock to observe and compute the delay time between the master clock and the receiver.
  • FIGURE 1 is a block diagram of a local area beacon system (LABS) for tracking objects within a local area;
  • LABS local area beacon system
  • FIG. 2 is a block diagram of a LABS as applied within a local area wherein the tracking of ground vehicles and aircraft is desired;
  • FIG. 3 is block diagram of an exemplary beacon for use in the LABS of FIGS. 1 and 2;
  • FIG. 4 is block diagram of an exemplary receiver for use in the LABS of FIGS. 1 and 2;
  • FIG. 5 is grid depicting the locations of five LABS receivers within a local area
  • FIG. 6 is a graph showing the horizontal dilution of precision (HDOP) of ground vehicles relative to the LABS receivers of FIG. 5;
  • HDOP horizontal dilution of precision
  • FIG. 7 is a graph showing the horizontal dilution of precision (HDOP) of aircraft relative to the LABS receivers of FIG. 5 and
  • FIG. 8 is a graph showing transmission collision probability of a LABS as a function of code rate.
  • a local area beacons system comprising a base station 10, three or more receivers 12 and one or more beacons 14, each mounted to a mobile object 18, the movement of which is to be tracked.
  • the base station 10 is connected to each receiver 12 with a data cable 16.
  • Each beacon 14 is a low cost, low power, transmit-only, radio- frequency device which supports precise determination of the location of the mobile object 18 on within a local area 22.
  • the local area 22 is approximately twenty-five square kilometers, but could possibly range from the size of a building or room up to a few hundred square kilometers or more.
  • Each beacon 14 transmits a beacon signal 20, the composition of which is described in detail below.
  • the beacon signals 20 are received by the set of receivers 12 in and around the local area 22.
  • Each receiver 12 records the time-of-arrival (TO A) of inbound beacon signals 20 with a precise local clock which is synclironized with each of the other local clocks.
  • the local clocks may be synclironized by several methods.
  • each receiver 12 contains a global positioning system (GPS) receiver which is used to transfer GPS time to the local clock.
  • GPS global positioning system
  • eachreceiver 12 uses differential GPS (DGPS) processing with a common set of corrections supplied over the data cable 16 from the base station 10.
  • DGPS differential GPS
  • a single master clock at the base station 10 synclironizes all of the receiver clocks using send-and-reply correction messages to observe and compute the delay time on each data cable 16 between the base station 14 and the receiver 12.
  • Position determination is carried out by processing the difference in time-of-arrival of the beacon signal 20 at each of the receivers 12.
  • This time difference of arrival (TDOA) processing removes any common clock uncertainty from the measurements.
  • the time of transmission of the beacon signal 20 is not known by the receivers 12 because the beacons 14 transmit at random times.
  • the TDOA between receivers 12 is independent of the time of beacon signal 20 transmission.
  • the TDOA depends on the relative location of the receivers 12 and the beacon 14.
  • the use of randomized transmission times and code-division multiplexing allows multiple beacons 14 to operate on a single carrier frequency in the local area 22. During typical LABS operation a multitude of beacons 14 transmit code bursts at random intervals.
  • code bursts include a unique beacon-identification (ID) codes which 5 identifies the item 18 from which the beacon 14 is transmitting.
  • ID unique beacon-identification
  • the code burst further includes a family code which, in a preferred embodiment, is shared by each beacon 14.
  • Each beacon's 14 unique ID code is combined with the family code in an exclusive-or operation.
  • the receivers 12 use multiple digital channels to correlate with the beacon family code, determine the time-of-arrival, and decode the unique beacon ID code to
  • the LABS operates within an airport 28, wherein the locations of both ground vehicles 24 and aircraft 26 are tracked.
  • five receivers 12 positioned around an airport 28 receive simultaneous transmissions from beacons 14 attached to ground vehicles 24 and aircraft
  • the output of the LABS is a set of vehicle ID's with current positions and speeds.
  • the beacon 14 positions and speeds are transmitted over a standard communications landline 32 from the LABS base station 10 to a ground traffic control station 30.
  • the base station 10 itself may contain an integral display or be attached to a display to see the beacon 14 locations.
  • the 20 10 is also connected by landlines 34 to the LABS receivers 12.
  • the messages from the receivers 12 to the base station 10 include the received signal ID, the received signal time- of-arrival referenced to the common clock, and signal quality indicators for beacon transmissions received.
  • the base station 10 includes a DGPS portion which provides
  • Each beacon 14 is a transmit-only device, and its operation is not synchronized with other beacons or the base station 10. As previously mentioned, each beacon 14 transmits a code burst at randomized intervals. The receivers 12 separate multiple transmissions by time-division and code-division multiplexing, through successive attempts to synchronize with the family code portion of the code burst. Destructive collisions occur when two beacons 14 transmit the family code within one chip period of each other.
  • the code rate and repetition interval can be varied to support any desired number of beacons 14 in the local area 28 with a specified probability of collision. In one implementation, a 3.6 MHz code rate supports 1000 beacons with one hertz transmissions with a probability of collision less than 10 "3 . The consequence of a collision is that a single position report is missed for each of the beacons 14 involved. Randomization of the transmission interval in each beacon 14 ensures that two beacons cannot "lock-up" and send repeated colliding transmissions.
  • the family code is a binary sequence that is added to the carrier in the beacon 14 with phase shift keying.
  • the simplest alternative is binary phase-shift keying (BPSK). More complicated phase shift keying alternatives are possible.
  • BPSK binary phase-shift keying
  • Any m-ary PSK signal can be used, where m is an arbitrary integer greater than one.
  • the m-ary PSK signal is the basis for the precise determination of the TO A of the beacon signal at each receiver 12.
  • Each receiver 12 has one or more digital channels that correlate a replica of the family code with received signals to detect the arrival of a beacon signal.
  • a vehicle equipped with a beacon 14 transmits a 10 millisecond BPSK spread spectrum code burst in the 915 MHz band approximately once a second. This code burst is received, time-tagged, and decoded for its unique ID number by each receiver 12. Each receivers 12 sends a message with this data to the base station 10.
  • the base station 10 matches up the ID's of signal messages from all the receivers 12. Reasonableness checks are performed on signal strength, angle of arrival and TDOA to eliminate multipath and strong interference.
  • the surviving measurements are processed to update the track of the beacon 14 and hence the track of the vehicle 24, 26 to which the beacon is attached.
  • the updated track information is passed along to the ground traffic controller 30.
  • the LABS can be extended such that aircraft 26 already equipped with DGPS receivers can utilize the LABS as an RF modem to transmit their position to the ground traffic controller 30.
  • the position information is combined with the family code as well as the beacon's unique ID code.
  • Aircraft that are not DGPS equipped can be equipped with a LABS beacon 14 at a much lower cost to provide their position to the ground traffic center 30.
  • Aircraft-mounted beacons 14 can be activated at preset altitude or by the gear down signal. Once activated, the aircraft are tracked and their positions integrated with those of the ground service fleet for display.
  • a different family code may be used for objects of different types.
  • aircraft 26 and ground vehicles 24 may have different family codes. Code-division multiplexing is used to separate the families in the receivers 12.
  • a LABS beacon 14 consists of a battery pack 38, a single chip microcontroller 40, a crystal oscillator 42, a frequency synthesizer 44, a mixer 52, a bandpass filer 53 , a BPSK modulator 46, an RF amplifier 48, and an antenna 50 mounted in a container of some sort.
  • a beacon 14 need be no larger than a pager.
  • the standard vehicle beacon 14 has an eight centimeter vertical antenna 50, a quarter- wave monopole for the 915 MHz band. Beacons 14 can be directly comiected to the vehicles power system, hi some applications a battery-powered beacon which is not vulnerable to shorts or spikes on the vehicle's power system is preferred. Vehicles which have lost power may be the most crucial to locate.
  • Each beacon 14 transmits a pseudorandom bit sequence, i. e. a code burst, and then goes to sleep for a variable delay, typically one second.
  • the bit sequence is BPSK modulated onto the carrier.
  • the delay between transmissions is randomized so two beacons cannot get synchronized and continuously jam each other out.
  • the baseline transmission time is ten milliseconds.
  • a 3.6 MHz spreading code is used to modulate the carrier throughout the transmission.
  • the beacon 14 uses 256 code bits per data bit and can transmit more than 100 bits of data over the link in a single code burst.
  • a beacon 14 does not have exclusive use of the frequency when it is transmitting. Multiple beacons 14 use code division multiplexing to share the channel.
  • the preferred embodiment is to use a single linear maximal sequence (LMS) for all the beacons 14 with the individual beacon's unique ID number encoded on the LMS sequence by an exclusive-or operation of the ID bits with a segment of the code.
  • LMS code provides the lowest cross-correlation possible for a given code length.
  • the LMS n-bit sequence has the lowest auto-correlation of any n-bit sequence with a phase shifted replica of itself assuming the correlation function is accumulated over the entire sequence length.
  • the receivers 12 can track the same LMS sequence from multiple beacons 14 because they are not starting the sequence at the same time. Thus the receiver 12 is continuously attempting to acquire and track a single LMS sequence with multiple digital channels.
  • a "low battery alarm" bit can be encoded with the ID for self-powered beacons.
  • data encoding can be more complex than direct exclusive- or of the ID bit with a code segment.
  • the data can be m-ary encoded on the spreading code.
  • M-ary encoding provides some advantage in bit error rate (BER) for a given energy/bit to noise density ration (E b /N 0 ) at the cost of receiver complexity. With m-ary encoding the receiver 12 must perform decision directed carrier recovery versus a simple Costas loop for exclusive-or encoding.
  • a typical RF link budget for the invention is shown below.
  • the budget in Table 1 shows a 10 dB margin for 100 milliwatt transmit power over a five kilometer link, sufficient for airports.
  • the beacons 14 can be directly wired into a vehicle power system, but the bulk of the beacons 14 are battery powered and can be used on any vehicle.
  • This embodiment of the invention supports one year of continuous operation off a single battery pack. This keeps the logistical burden down.
  • An estimate of the mission requirements is summarized in Table 2.
  • each receiver 12 includes one or more antennas 54. Associate with each antenna 54 is a RF hardware channel 56. In a preferred embodiment each receiver 12 includes a single omni-directional antenna 54, but multiple element antennas with beam-forming capability may be used.
  • the receiver 12 may be one of several different architectures, direct conversion, single conversion, double, or triple conversion.
  • the resultant filtered IF or RF signals are sampled and digitized by a bandpass filter 58, RF amp 60, mixer 62 and digitizer 64 prior to being presented to the multiple digital hardware channels 56. They may be directly down-converted in frequency or they may be sub-sampled to achieve down-conversion.
  • the digitized signals are then searched for correlation peaks and tracked in the fashion of a GPS receiver or direct sequence spread-spectrum modem.
  • the receivers 12 use precise clocks to time tag the inbound m-ary PSK messages from the beacons 14.
  • the act of successfully correlating the receiver's code replica with the inbound beacon signal determines the time of arrival of the beacon's signal in receiver clock time.
  • the fundamental accuracy limits are the code phase measurement error and the clock error.
  • the limiting factor for the code phase error is the effective bandwidth of the beacon signal.
  • the definition of the effective bandwidth and the computation of the range error limit for the sin(x)/x spectrum can be found in Skolnik, Introduction to Radar Systems. McGraw-Hill, 1980, pp. 405. Assuming the BPSK signal is filtered at the first null, the range error limit is
  • ⁇ R is the range error divided by the chip length
  • E is the energy per symbol divided by the noise density.
  • One embodiment of the invention uses 3.6 MHz chip rate BPSK.
  • the RF link budget shown earlier, gives the receiver front end input power at the five kilometer range as -87.02 dBm for a 915MHz 100 milliwatt transmitter.
  • the range error limit is a function of the symbol integration time, or the number of code bits per data bit. We can use this relationship to establish the minimum number of chips per symbol, where in this case a symbol is a single data bit.
  • the 3.6 MHz code rate of the LABS is capable of transmitting 14.4 kilobits per second or 144 bits in the nominal 10 millisecond transmission.
  • the integration time is increased beyond the symbol time through the use of decision-directed carrier recovery. This is a trade-off of increased receiver complexity and computational burden to obtain a better energy to noise density ratio and lower range error.
  • the near-far problem is common to mobile communications systems.
  • the beacon closest to the receiver 12 tends to overwhelm the signals from beacons further away from the receiver, effectively setting the receiver automatic gain control (AGC) and receiver A/D converter.
  • AGC automatic gain control
  • the LABS limits this problem through time division multiplexing.
  • the beacon 14 transmits randomized bursts, so that a beacon 14 very close to a receiver 12 cannot block out other beacon signals repeatedly. While collisions and missed bursts are expected from the beacons 14, continuously missed bursts from a individual beacon are not expected.
  • the next level of defense against the near-far problem is the selection of low cross- correlation codes. If code cross-correlations are kept below 33 dB, for example, then 30 dB power difference between the near and far beacons should not prevent the acquisition of the far beacon's signal. This does imply a wide dynamic range in the receiver A/D, at least 6 bits to support 30 dB of dynamic range with an ideal AGC. If the receivers 12 are positioned such that no beacon 14 can get closer than 100m, then 33 dB of isolation allow the acquisition of signals throughout a 100m to 3 km range without the receiver being swamped by the near beacon signal. In another embodiment of the invention multiple-element antennas are used at the receiver 12 and beam forming techniques are used to isolate signals along different lines- of-sight.
  • Multipath may be categorized into several regions based on the delay of the reflected ray relative to the primary ray.
  • hi “close multipath” multipath rays arrive at the receiver 12 within one code chip interval of the primary ray. This can be treated by increasing the chip rate and/or by increasing the front-end bandwidth to estimate the effects of multipath on the observed correlation peak. Typically an attempt is made to correlate two or more code replicas, to best fit the multipath distorted correlation peak.
  • disant multipath multipath rays arrive at the receiver 12 more than one code chip interval from the primary ray. This is generally screened off by the selection of a code with low autocorrelation. It is critical that the receiver 12 detect the first ray when measuring TOA, not the strongest ray, which may not be the direct ray.
  • multipath rays may be the only received signal if the direct ray is completely blocked. In this case no direct TOA measurement is formed. Instead, the multipath ray is detected so it can be thrown out of the measurement set.
  • the receiving antenna systems are sighted to minimize the amount of blockage from fixed features in the region of interest, but moving aircraft and ground service vehicles create a dynamic blockage environment.
  • the use of multiple receivers 12 to track the same signal is advantageous in this situation.
  • the time of arrival and angle of arrival at each receiver 12 as well as prior vehicle location information can be combined to develop a reasonableness test for the detection of multipath signals.
  • Each LABS receiver 12 collects digitized samples. For ten megahertz, ten bit sampling with five receivers 12 there is a total of 500 megabit per second of data collected. In one embodiment, optimal processing is conducted at the base station 10 by collecting all the data and matching the received code sequences from each receiver antenna. While this is possible, the preferred embodiment is to perform the correlations at each receiver 12. Each receiver 12 outputs a TOA, a C/N 0 estimate, and an ID for each beacon message 20 received. The TOA is determined by a digital correlator operating on the samples collected at that location. Multiple digital correlator channels operate off of the same sampled RF data stream. The base station 10 uses the differenced TO As, and C/N 0 to perform reasonableness checks and discard multipath rays. The remaining differenced TOAs are processed to update the beacon's 14 position.
  • the preferred embodiment of TOA processing in the base station 10 is to difference TOA ' s from the receivers 12 and present the TDOA measurements to an extended Kalman filter (EKF) to update the estimated beacon position and velocity.
  • EKF extended Kalman filter
  • the beacon states in the EKF may include the speed and heading, so the beacon's 14 position can be predicted for short intervals.
  • the predicted beacon may be used to preposition correlators in the receivers 12 to minimize acquisition time. Alternatively direct solution of the time- difference equations can be used. This places the location of the beacon on the intersection of two or more hyperbola branches. Each hyperbola branch is the set of points that result in a range difference between two receivers 12 sufficient to cause the observed TDOA.
  • This inverted Loran processing in the Loran chain the mobile element determines which hyperbolas it is on by observing the time differences of received pulses from the synchronized transmitters in the Loran chain.
  • the calculations are the same, however in LABS they are carried out at the base station 10, the beacon 14 has no knowledge of its own position.
  • FIG. 5 is a plot of the location of five receiver 12 for a hypothetical airport local area contained within a 3 kilometer square region. Four of the receiver sites 12 are 141 meters off the corners of the square while a fifth receiver 12 is on top of a control tower. Each receiver 12 location is indicated with a box and annotated with the elevation of the antenna in meters.
  • beacons 14 there are two classes of beacons 14, those affixed to ground vehicles 24 (FIG. 2) and those affixed to aircraft 26. Each beacon class utilizes separate spreading codes and the LABS receivers 12 and base station 10 know which type of beacon signal 20 they are receiving. The information is used to determine which type of solution to compute. For the ground vehicles, the elevation is known. The solution sought is therefore two- dimensional.
  • the horizontal dilution of precision (HDOP) for the ground vehicles can be computed as a function of their position within the three kilometer airport region. This is shown in FIG. 6. This can be mapped to expected position error by multiplying the HDOP by the expected TOA accuracy of 1.5 meter two sigma. The expected horizontal position error in meters is 1.5 times the HDOP value given in the contour. The entire airport region can be covered with two meter, two sigma, horizontal accuracy for ground vehicles.
  • HDOP horizontal dilution of precision
  • the airport's ground elevation data must be imported into the base station 10.
  • the height above ground for each vehicle that a beacon 14 is installed on should be entered as well.
  • the receiver 12 array has low observability of the vertical channel, and missing elevation data will not seriously degrade horizontal accuracy.
  • the system allows for the possibility that the aircraft is not yet taxiing, but is still in the air with the LABS beacon turned on. This additional unknown changes how well the horizontal position can be estimated.
  • FIG. 7 the HDOP map for the aircraft fleet is presented, which is somewhat deteriorated from FIG. 6.
  • the horizontal position can be predicted to within three meters two sigma throughout the airport region.
  • VDOP vertical dilution of precision
  • the LABS has a capacity to support one thousand beacons 14 operating simultaneously in the same band, maintain an average one second position update interval, and miss less than one in one thousand fix attempts.
  • the beacons 14 are transmitting at random times and the transmissions will collide.
  • FIG. 8 is the result of the simulation for varying code rates. Figure 8 shows that the collision rate can be kept below one in one thousand for a code rate of approximately 3.6 MHz, which serves as a baseline.
  • the defining conditions are the desire to locate objects in a fixed area of interest with low cost, low power beacons. In applications where there is significant blockage and foliage the LABS has an advantage over GPS based systems. LABS can be used indoors.
  • the LABS beacon may be pager sized and easily carried by personnel.
  • One or more bits can be added to the waveform to indicate additional information from the beacon, particularly an emergency of some kind.
  • Some applications of the invention are: locating skiers in a ski area, locating people and equipment in warehouses and factories, locating key personnel in an airport, locating customers or key personnel in an amusement park.
  • LABS Another class of applications for the LABS are situations applications where the assets or personnel to be tracked are going to be operating in a region for some period of time, but not permanently. In this case the area of interest is identified and portable receivers 12 are positioned around the perimeter. The receiver's self-survey using GPS or DGPS. The LABS transponders then work in the usual fashion. This system can support law enforcement agencies, fire departments, construction crews and other operations where personnel and equipment move through buildings and in an urban canyon environment where GPS coverage cannot be relied upon. For firefighters and law enforcement officers in particular, a timely picture of the location of all team members in a building can be crucial to saving lives.

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

Abstract

La présente invention concerne une pluralité de récepteurs (12) de signaux de balise qui sont positionnés de façon à définir une zone locale (22). Des objets (18) présents dans cette zone locale (22) sont équipés de balises (14) qui émettent des signaux (20) de balise de façon aléatoire, de préférence sur la même fréquence de porteuse. Le signal de balise (20) comprend une rafale de code de balise comprenant un code de famille et un code d'identification de balise. Le récepteur (12) reçoit les signaux (20) de balise, décode le code d'identification de balise et enregistre l'heure d'arrivée de chaque signal de balise à l'aide d'une horloge locale. Une station de base (10) reçoit des données indicatives du code d'identification de balise et de l'heure d'arrivée et traite la différence des heures d'arrivée de ce signal (20) de balise entre chacun des récepteurs (12) de façon à déterminer la localisation de cette balise (18) présente dans la zone locale (22) et l'identification de l'objet (18) à partir duquel cette balise à émis.
PCT/US2001/020066 2000-07-06 2001-06-21 Systeme de balises de zone locale destine a la determination de position WO2002004975A1 (fr)

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GB2390499A (en) * 2002-02-06 2004-01-07 Igt Reno Nev Means for locating a gaming machine within a building
GB2390499B (en) * 2002-02-06 2006-06-07 Igt Reno Nev Method and apparatus for machine location
US8267789B2 (en) 2002-02-06 2012-09-18 Igt Method and apparatus for machine location
US7535796B2 (en) 2002-04-09 2009-05-19 Sonitor Technologies As System and method for position determination of objects
US7864633B2 (en) 2002-04-09 2011-01-04 Sonitor Technologies As System and method for position determination of objects
WO2004051304A1 (fr) * 2002-12-04 2004-06-17 Sonitor Technologies As Systeme de poursuite et de localisation ultrasonores
US7352652B2 (en) 2002-12-04 2008-04-01 Sonitor Technologies As Ultrasonic tracking and locating system
US7362656B2 (en) 2002-12-04 2008-04-22 Sonitor Technologies As Ultrasonic locating system
US6897763B2 (en) 2003-08-07 2005-05-24 Eastman Kodak Company Retail signage management system
US8947300B2 (en) 2003-09-02 2015-02-03 Csr Technology Inc. Control and features for satellite positioning system receivers
US9869770B2 (en) 2003-09-02 2018-01-16 Qualcomm Incorporated Control and features for satellite positioning system receivers
WO2006014170A1 (fr) * 2004-07-03 2006-02-09 Sirf Technology, Inc. Systeme de communication pour localisation assistee

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