Patent Application
20150057018
The invention relates to position determination systems, and more particularly, to hybrid positioning using wireless communication signals.
To perform position location in wireless cellular networks (e.g., a cellular telephone network), several approaches perform trilateration based upon the use of timing information sent between each of several base stations and a mobile device, such as a cellular telephone. One approach, called Advanced Forward Link Trilateration (AFLT) in CDMA or Enhanced Observed Time Difference (EOTD) in GSM or Observed Time Difference of Arrival (OTDOA) in WCDMA, measures at the mobile device the relative times of arrival of signals transmitted from each of several base stations. These times are transmitted to a Location Server (e.g., a Position Determination Entity (PDE) in CDMA), which computes the position of the mobile device using these times of reception. The transmit times at these base stations are coordinated such that at a particular instance of time, the times-of-day associated with multiple base stations are within a specified error bound. The accurate positions of the base stations and the times of reception are used to determine the position of the mobile device.
In another approach, called Uplink Time of Arrival (UTOA), the times of reception of a signal from a mobile device is measured at several base stations (e.g., measurements taken at base stations 101, 103 and 105).
Yet a third method of doing position location involves the use in the mobile device of circuitry for the United States Global Positioning Satellite (GPS) system or other Satellite Positioning Systems (SPS), such as the Russian GLONASS system and the proposed European Galileo System or a combination of satellites and pseudolites. Pseudolites are ground-based transmitters, which broadcast a PN code (similar to a GPS signal) modulated on an L-band carrier signal, generally synchronized with SPS time. Each transmitter may be assigned a unique PN code so as to permit identification by a mobile device. Pseudolites are useful in situations where SPS signals from an orbiting satellite might be unavailable, such as tunnels, mines, buildings or other enclosed areas. The term “satellite”, as used herein, is intended to include pseudo lite or equivalents of pseudolites, and the term GPS signals, as used herein, is intended to include GPS-like signals from pseudolites or equivalents of pseudolites. Methods that use an SPS receiver to determine a position of a mobile station may be completely autonomous (in which the SPS receiver, without any assistance, determines the position of the mobile station) or may utilize the wireless network to provide assistance data or to share in the position calculation. Examples of such methods are described in U.S. Pat. Nos. 5,812,087; 5,841,396; 5,874,914; 5,945,944 and 6,208,290. For instance, these patents describe, among other things: a method to obtain from cellular phone transmission signals accurate time information, which is used in combination with SPS signals to determine the position of the receiver; a method to transmit the Doppler frequency shifts of in-view satellites to the receiver on the mobile device through a communication link to determine the position of the mobile device; a method to transmit satellite almanac data (or ephemeris data) to a receiver through a communication link to help the receiver to determine its position; a method to lock to a precision carrier frequency signal of a cellular telephone system to provide a reference signal at the receiver for SPS signal acquisition; a method to use an approximate location of a receiver to determine an approximate Doppler for reducing SPS signal processing time; and a method to compare different records of a satellite data message received to determine a time at which one of the records is received at a receiver in order to determine the position of the receiver. In practical low-cost implementations, both the mobile cellular communications receiver and the SPS receiver are integrated into the same enclosure and may in fact share common electronic circuitry.
In yet another variation of the above methods, the round trip delay (RTD) is found for signals that are sent from the base station to the mobile device and then are returned. In a similar, but alternative, method the round trip delay is found for signals that are sent from the mobile device to the base station and then returned. Each of these round-trip delays is divided by two to determine an estimate of the one-way propagation delay. Knowledge of the location of the base station, plus a one-way delay constrains the location of the mobile device to a circle on the earth. Two such measurements from distinct base stations then result in the intersection of two circles, which in turn constrains the location to two points on the earth. A third measurement (even an angle of arrival or cell sector identification) resolves the ambiguity.
A combination of either the AFLT or U-TDOA with an SPS system may be referred to as a “hybrid” system. For example, U.S. Pat. No. 5,999,124 describes, among other things, a hybrid system, in which the position of a cell based transceiver is determined from a combination of at least: i) a time measurement that represents a time of travel of a message in the cell based communication signals between the cell based transceiver and a communication system; and ii) a time measurement that represents a time of travel of an SPS signal.
Altitude aiding has been used in various methods for determining the position of a mobile device. Altitude aiding is typically based on a pseudo-measurement of the altitude. The knowledge of the altitude of a location of a mobile device constrains the possible positions of the mobile device to a surface of a sphere (or an ellipsoid) with its center located at the center of the earth. This knowledge may be used to reduce the number of independent measurements required to determine the position of the mobile device. For example, U.S. Pat. No. 6,061,018 describes, among other things, a method where an estimated altitude is determined from the information of a cell object, which may be a cell site that has a cell site transmitter in communication with the mobile device.
In one aspect of the present invention, a method of determining a position of a mobile station, the method comprising: receiving wireless signals from a first wireless network; receiving wireless signals from a second wireless network; determining timing measurements based on the wireless signals from the first wireless network and the wireless signals from the second wireless network; and determining the position of the mobile station based on the timing measurements.
In another aspect of the present invention, a method of determining a position of a mobile station, the method comprising: receiving wireless signals from a first base station in a first wireless network, wherein the mobile station is unauthorized for access to the first wireless network; receiving wireless signals from a second base station in a second wireless network, wherein the mobile station is subscribed to the second wireless network; determining a first identity of the first base station in the first wireless network; determining a second identity of the second base station in the second wireless network; transmitting the first and second base station identities to a location server having access to a base station almanac; retrieving corresponding positions of the first and second base stations based on the first and second base station identities; and determining the position of the mobile station based on the timing measurements.
In another aspect of the present invention, a mobile device for determining a position of the mobile station, the mobile device comprising: means for receiving wireless signals from a first wireless network; means for receiving wireless signals from a second wireless network; means for determining timing measurements based on the wireless signals from the first wireless network and the wireless signals from the second wireless network; and means for determining the position of the mobile station based on the timing measurements.
In another aspect of the present invention, a mobile device comprising a processor and a memory wherein the memory includes software instructions to: receive wireless signals from a first wireless network; receive wireless signals from a second wireless network; determine timing measurements based on the wireless signals from the first wireless network and the wireless signals from the second wireless network; and determine the position of the mobile station based on the timing measurements.
In another aspect of the present invention, a non-transitory computer readable medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method for determining a position of a mobile station having memory and a processor, said method comprising operations of: receiving wireless signals from a first wireless network; receiving wireless signals from a second wireless network; determining timing measurements based on the wireless signals from the first wireless network and the wireless signals from the second wireless network; and determining the position of the mobile station based on the timing measurements.
The present invention includes methods and apparatuses that perform these methods, including data processing systems, which perform these methods, and computer readable media that when executed on data processing systems cause the systems to perform these methods. Further, the inventions described herein may be implemented on different nodes within a system, such nodes including a mobile station, a base station (such as a wireless access point) or a location server or other nodes in a network or wireless network.
Other features of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.
The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.
The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention. Numerous specific details are described to provide a thorough understanding of the present invention. However, in certain instances, well known or conventional details are not described in order to avoid obscuring the description of the present invention. References to one or an embodiment in the present disclosure are not necessary to the same embodiment; and such references mean at least one.
Recent development of wireless communication technologies leads to the deployment of various different wireless networks with substantial overlapping coverage in some areas. In the present application, a wireless network refers to a set of wireless access points (e.g., base stations) with a same air interface, operated by one service provider (e.g., Verizon Wireless or Sprint), such that a mobile unit can access the network through one of the set of the wireless access points when in the coverage area of the network; and the union of the coverage areas of the wireless access points of the wireless network is the coverage area of the network. Further, data communication refers to the transmission of data in a two-way communication system although, in certain embodiments, data communication may be a one-way communication or may include extracting information embedded in a signal, which is broadcasted regardless whether the receiver needs it or not. A wireless access point may be considered to be a cell tower or a base station or other wireless transmitter or receiver, which is coupled to a network of other nodes (for example, the wireless access point is coupled by wireless or wire line to the other nodes).
In certain areas, especially urban metropolitan areas, different wireless networks have substantially overlapping coverage. For example, different service providers may offer the same type of wireless service (e.g., cellular phone communication) in the same area. Further, different types of wireless services, such as wireless phone services (e.g., cellular phone services for data, voice or both) and wireless digital communication services (e.g., wireless local area networks such as WiFi networks, bluetooth, ultra-wideband), may have overlapping in coverage area. For example, wireless LAN (Local Area Network) access points (e.g., for an IEEE 802.11 based wireless network) may be located within the coverage areas of wireless telecommunication networks (e.g., based on Telecommunications Industry Association (TIA)/Electronic Industries Alliance (EIA) Standards, such as IS-95, IS-856 or IS-2000), such as those based on TDMA (Time Division Multiple Access), GSM (Global System for Mobile communications), CDMA (Code Division Multiple Access), WCDMA (Wideband Code Division Multiple Access), UMTS (Universal Mobile Telecommunication System), TD-SCDMA (Time Division Synchronous Code Division Multiple Access), iDEN (integrated Digital Enhanced Network), HDR (High Data Rate) or other similar cellular networks.
At least one embodiment of the present invention seeks a comprehensive system, which supports positioning using these disparate sources of wireless signals to determine measurements and to obtain aiding information (e.g., the position and the coverage area of an access point, Doppler frequency shifts for in-view SPS satellites, SPS ephemeris data) to form a flexible and ubiquitous navigation solution. In this comprehensive system, when information about an access point (e.g., base station almanac, such as the location and coverage area of the base station) is available, it is used and may be enhanced. Where it is not, the system may automatically gather and enhance such information for the benefit of future positioning attempts.
At least one embodiment of the present invention uses wireless signals transmitted from access points of more than one wireless network to combine information, such as SPS observations, wireless network observations, terrain elevation information and others, to obtain a position solution for a mobile station. In one embodiment of the present invention, a mobile station of a hybrid position system transfers information over access points of more than one wireless network (in two-way communication) to aid in the acquisition of SPS signals, time stamping for measurements and other operations at the mobile station. In one embodiment of the present invention, a mobile station of a hybrid position system performs measurements using signals from access points of different wireless networks, while communicating with a remote server using one or more of the wireless networks.
Typically, information describing the identification, location and coverage area of the sectors of a wireless network is stored in a base station almanac, which has been used in a hybrid positioning system using a single wireless network. However, when different wireless networks (e.g., different service providers or different types of networks) have overlapping coverage, a typical mobile station does not have access to such information for the access points of the different wireless networks, even though the wireless signals transmitted from the access points of the different wireless networks are in the air and available to the mobile station. This is usually because the mobile station is allowed or is authorized to have access to one wireless network but not another wireless network. One simple example of this is a cell phone that has been authorized access to a first wireless network (e.g., a cell phone network operated by a service provider such as Verizon Wireless) but has not been authorized access to a second wireless network (e.g., Sprint's cell phone network) or to a third wireless network (e.g., a Wi-Fi “hotspot”).
In one embodiment of the present invention, when available, information from small and localized transmitters, such as an IEEE 802.11 wireless LAN access point, is incorporated into the wireless navigation solution. In many cases, the location information for these transmitters is not well known. In some cases, the “almanac” information describing the physical characteristics of a wireless network (e.g., ID, location and coverage area of access points) is not available to users who might like to use it. Some network providers may choose not to share such information, while still others may not have it available. In one embodiment of the present invention, information for deriving the physical characteristics of a network is gathered from mobile stations that use another wireless network for communication. In one embodiment of the present invention, using the wireless signals available in the air from different wireless networks and the abilities of the mobile station for position determination (e.g., a cell phone with a GPS receiver or with a portion of a GPS receiver), mobile stations harvest information about the access points of the different wireless networks, which in general may not be under control of an operator of a wireless network through which the mobile stations typically perform data communication. The harvested information is used to derive location information (e.g., the location, coverage area) about the access points, which can be used for aiding hybrid position determination for future position determinations.
In one embodiment of the present invention, the signals used to provide time information and/or frequency information to a mobile station are not the same as the one over which data communication transactions are carried out.
A mobile station that supports multiple wireless communication interfaces (e.g., IEEE 802.11 [and other IEEE 802 standards such as 802.15, 802.16 and 802.20], Bluetooth, UWB [Ultra-Wideband], TDMA, GSM, CDMA, W-CDMA, UMTS, TD-SCDMA, iDEN, HDR or other similar networks) is used in one embodiment of the present invention to use multiple wireless networks. Such a mobile station may have, for example, several different portions in a communication section, which support the transmission and/or reception of data for these different communication interfaces. Thus, one portion may handle the transmission and/or reception of Wi-Fi signals (e.g., IEEE 802.11 or 802.16) and another portion of the communication section may support a cellular telephone interface such as a CDMA interface. This also gives the user alternative communication paths from which to choose when deciding to communicate. For example, the availability, coverage, expense, data speed and ease of use may be considered when choosing which communication path to use.
In one embodiment of the present invention, a first wireless network is used for communications and positioning, while a second wireless network is used for positioning and optionally communications. For example, each of these wireless networks might use a completely different air interface (e.g., different TIA/EIA standards), such as an air interface that is for a typical wireless cell phone (e.g., TDMA, GSM, CDMA, W-CDMA, UMTS, TD-SCDMA, iDEN, HDR or other similar cellular networks) or some other wireless air interface, such as that in accordance with IEEE 802.11, bluetooth or UWB. A plurality of these wireless networks is used for positioning purposes, even when only one wireless network may be used for communications. The advantages of a hybrid approach according to at least some of the embodiments of the present invention include: improved redundancy for a more failsafe solution, higher positioning availability, better accuracy and faster time to fix.
Multiple cellular base stations are typically arranged to cover a geographical area with radio coverage. These different base stations are coupled to at least one mobile switching center, as is well known in the prior art (e.g., see
The server 201, which is a form of a data processing system, includes a bus 202 which is coupled to a microprocessor 203 and a ROM 207 and volatile RAM 205 and a non-volatile memory 206. The processor 203 is coupled to cache memory 204 as shown in the example of
Note that while
In some embodiments, the methods of the present invention may be performed on computer systems that are simultaneously used for other functions, such as cellular switching, messaging services, etc. In these cases, some or all of the hardware of
It will be apparent from this description that aspects of the present invention may be embodied, at least in part, in software. That is, the techniques may be carried out in a computer system or other data processing system in response to its processor executing sequences of instructions contained in memory, such as ROM 207, volatile RAM 205, non-volatile memory 206, cache 204 or a remote storage device. In various embodiments, hardwired circuitry may be used in combination with software instructions to implement the present invention. Thus, the techniques are not limited to any specific combination of hardware circuitry and software nor to any particular source for the instructions executed by the data processing system. In addition, throughout this description, various functions and operations are described as being performed by or caused by software code to simplify description. However, those skilled in the art will recognize what is meant by such expressions is that the functions result from execution of the code by a processor, such as the processor 203.
A machine readable medium can be used to store software and data, which when executed by a data processing system causes the system to perform various methods of the present invention. This executable software and data may be stored in various places including for example ROM 207, volatile RAM 205, non-volatile memory 206 and/or cache 204 as shown in
Thus, a machine readable medium includes any mechanism that provides (i.e., stores and/or transmits) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). For example, a machine readable medium includes recordable/non-recordable media (e.g., read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; etc.), as well as electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc.
Mobile device 310 is an example of a combined GPS receiver and a communication receiver and transmitter. The communication receiver and transmitter may be implemented as multiple receivers and transmitters for the different wireless networks. For example, the communication transceiver 305 may include a transceiver portion for receiving and/or transmitting cellular telephone signals and another transceiver portion for receiving and/or transmitting Wi-Fi signals. Mobile device 310 contains a GPS receiver stage including GPS acquisition and tracking circuit 321 and communication transceiver 305. GPS acquisition and tracking circuit 321 is coupled to GPS antenna 301, and communication transceiver 305 is coupled to communication antenna 311. GPS signals (e.g., signal 370 transmitted from satellite 303) are received through GPS antenna 301 and input to GPS acquisition and tracking circuit 321 which acquires the PN (pseudorandom noise) codes for the various received satellites. The data produced by GPS acquisition and tracking circuit 321 (e.g., correlation indicators) are processed by processor 333 for transmittal (e.g., of SPS pseudoranges) by communication transceiver 305. Communication transceiver 305 contains a transmit/receive switch 331 which routes communication signals (typically RF) to and from communication antenna 311 and communication transceiver 305. In some systems, a band splitting filter or “duplexer,” is used instead of the T/R switch. Received communication signals are input to communication receiver 332 and passed to processor 333 for processing. Communication signals to be transmitted from processor 333 are propagated to modulator 334 and a frequency converter (IF/RF converter 335). Power amplifier 336 increases the gain of the signal to an appropriate level for transmission to base station 352 (or to wireless LAN access point 362).
In one embodiment of the present invention, communication transceiver 305 is capable of being used with a number of different air interfaces (e.g., IEEE 802.11, bluetooth, UWB, TD-SCDMA, iDEN, HDR, TDMA, GSM, CDMA, W-CDMA, UMTS or other similar networks) for communication (e.g., through communication links 350 and 360). In one embodiment of the present invention, communication transceiver 305 is capable of being used with one air interface for communication and capable of being used to receive signals with other air interfaces. In one embodiment of the present invention, communication transceiver 305 is capable of being used with one air interface for communication while also being capable of being used with signals in another air interface to extract timing indicators (e.g., timing frames or system time) or to calibrate the local oscillator (not shown in
In one embodiment of the combined GPS/communication system of mobile device 310, data generated by GPS acquisition and tracking circuit 321 is transmitted to a server over communication link 350 to base station 352 or over communication link 360 to wireless LAN access point 362. The server then determines the location of mobile device 310 based on the data from the remote receiver, the time at which the data were measured and ephemeris data received from its own GPS receiver or other sources of such data. The location data can then be transmitted back to a receiver 332 in mobile device 310 or to other remote locations. More details about portable receivers utilizing a communication link can be found in U.S. Pat. No. 5,874,914.
In one embodiment of the present invention, the combined mobile device 310 includes (or is coupled to) a data processing system (e.g., a personal data assistant or a portable computer). The data processing system includes a bus that is coupled to a microprocessor and a memory (e.g., ROM, volatile RAM and/or non-volatile memory). The bus interconnects various components together and also interconnects these components to a display controller and display device and to peripheral devices such as input/output (I/O) devices, which are well known in the art. The bus may include one or more buses connected to each other through various bridges, controllers and/or adapters as are well known in the art. In one embodiment, the data processing system includes communication ports (e.g., a USB (Universal Serial Bus) port, a port for IEEE-1394 bus connection). In one embodiment of the present invention, the mobile station stores the locations and identifications (e.g., MAC address) of wireless access points (e.g., according to the types of the wireless access points) for extracting and enhancing the location information about the wireless access points using the memory and software program instructions stored in the memory. In one embodiment, the mobile station only stores the locations of the mobile station and identifications of the wireless access points for transmission to a server (e.g., through a communication port or a wireless communication link) when a communication connection is established.
In one embodiment of the present invention, the position determination is performed at location server 411 shown in the example depicted in
Network 401 may include local area networks, one or more intranets and the Internet for the information exchange between the various entities. It is understood that servers 411, 413 and 415 may be implemented as a single server program or different server programs in a single data processing system or in separate data processing systems (e.g., maintained and operated by different service providers).
In one embodiment of the present invention, different service providers operate wireless networks A and B, which are used by the mobile station for position determination. A typical mobile station is a subscriber only to one of them, and thus the mobile station is authorized to use (and to have access to) only one wireless network. However, it is often still possible to at least receive signals from the wireless network that is not subscribed to and thus it is still possible to make range measurements or signal strength measurements relative to wireless access points in the wireless network that is not subscribed to. One specific example of this situation would involve a user of a tri-mode CDMA cellular phone, which can receive PCS frequency band signals (e.g., from the wireless network operated by Sprint, which is a first service provider) and can also receive other CDMA signals at other frequencies (such as, for example, from the wireless network operated by Verizon Wireless, which is a second service provider). If the user has subscribed only to Sprint's wireless network, then the user's phone (a form of a mobile station) is authorized to operate with Sprint's wireless network but not Verizon's wireless network. The user may use the phone in an environment in which only one Sprint wireless access point (e.g., a Sprint cellular base station) is capable of radio communication with the user's phone, but in this environment there are numerous Verizon wireless access points that are within radio communication range of the user's phone. In this context, it is still possible for the phone to obtain SPS assistance data (if desired) from a location server through Sprint's wireless network and to transmit SPS pseudoranges, obtained at the phone, to the location server. However, it will not be possible to obtain more than one range measurement to a wireless access point unless range measurements to Verizon's wireless access points are obtained. With an embodiment of the invention, the phone obtains range measurements to the available Verizon wireless access points, thereby providing at least a few range measurements (e.g., distances between the phone and two Verizon cellular base stations) which can be used in the position calculations that are performed to determine the position of the phone.
The service providers maintain the almanac information on servers 413 and 415 separately. Although mobile station 407 has communication access to only one of the wireless networks, location server 411 may have access to both servers 413 and 415 for base station almanac data. After determining the identities of base stations (e.g., the wireless access points 403 and 405) of both wireless networks A and B, the mobile station 407 transmits the base station identifications to location server 411, which uses servers 413 and 415 to retrieve the corresponding positions of the base stations, which can be used in determining the position of the mobile station.
Alternatively, the cooperation between the service providers to share almanac data is not necessary. For example, the operator of location server 411 maintains both almanac servers 413 and 415 (e.g., through a survey process to obtain the almanac data or through a data harvesting process using mobile stations, which will be described in detail with
In one embodiment of the present invention, mobile station 407 uses both wireless networks A and B for communicating with the location server (instead of using only one of the wireless networks for communication purpose). As known in the art, various types of information can be exchanged between the mobile station and the location server for position determination. For example, location server 411 can provide the mobile station 407 with Doppler frequency shift information for in-view satellites of the mobile station (e.g., through wireless network A); and the mobile station can provide pseudorange measurements for SPS signals, the identification information of the base stations and associated range measurements (e.g., round trip time measurements) to the location server for the calculation of the position of the mobile station (e.g., through wireless network B). In one embodiment of the present invention, a mobile station is capable of communicating through more than one wireless network to the location server when in the coverage area of these wireless networks. However, the trade-off between cost and performance may dictate communication with the server using one of the wireless networks, while using the others only for timing measurements (or other measurements, such as received signal levels) or for aiding in measurement, such as obtaining time information from wireless transmission from an access point for time stamping measurements (e.g., for resolving ambiguity) or locking to the accurate carrier frequency of a wireless cellular base station for calibrating the local oscillator of the mobile station.
In one embodiment of the present invention, the location of the mobile station is determined at the location server using the information communicated from the mobile station and then transmitted back to the mobile station. Alternatively, the position calculation can be performed at the mobile station using assistance information from the location server (e.g., Doppler frequency shifts for in-view satellites, positions and coverage areas of access points, differential GPS data and/or altitude aiding information).
Typically, a wireless LAN access point (or other similar low power transmitters) has a small coverage area. When available, the small coverage area of such an access point provides a very good estimate of the location of the mobile station. Further, wireless LAN access points are typically located near or inside buildings, where the availability of other types of signals (e.g., SPS signals or wireless telephone signals) may be low. Thus, when such wireless transmissions are used with other types of signals, the performance of the positioning system can be greatly improved.
In one embodiment of the present invention, the wireless signals from different wireless networks are used for position determination. For example, the wireless signals from the different wireless networks can be used to determine the identities of the corresponding access points, which are then used to determine the locations and coverage areas of the corresponding access points. When precision range information (e.g., round trip time or signal traveling time between an access point and the mobile station) is available, the range information and the location of the access point can be used in obtaining a hybrid positioning solution. When approximate range information (e.g., received signal level, which can be approximately correlated with an estimated range) is available, the location of the access point can be used to estimate the position of the mobile station (or determine the estimated altitude of the mobile station). Further, the mobile station can use precision carrier frequency from one of the wireless networks (e.g., from access point 505 or 509), which may not be the one used for the data communication purpose, to calibrate the local oscillator of the mobile station. More details about locking to a precision carrier frequency of a wireless signal to provide a reference signal at an SPS receiver for signal acquisition can be found in U.S. Pat. No. 5,874,914. Further, the mobile station can use the accurate time information in the wireless signals from one of the wireless networks (e.g., from access point 505 or 509), which may not be the one used for the data communication purpose. More details about using the accurate time information (e.g., timing markers or system time) for time stamping can be found in U.S. Pat. No. 5,945,944.
Since some of the access points of the different wireless networks do not have well-known almanac data (e.g., position of the wireless access point and/or coverage area of the wireless access point), one embodiment of the present invention derives the almanac data from the information collected from mobile stations.
Further, the accumulated data points of the locations of mobile stations show the coverage area of the access point (e.g., in a scatter plot of the mobile locations). When the position of the access point is not known, the collected data points can be used to estimate the position and the coverage of the access point. When an initial estimation of the position of the access point is available, the collected data points can be used to improve the estimation. The collection and enhancement process can be a continuous process during the service of the location server. Note that the collection and enhancement operations can also be performed on a different server other than the location server. For example, in one embodiment of the present invention, the collection and enhancement operations are performed in almanac server 513, which communicates with location server 511 in performing hybrid position determination for mobile stations.
However, precision information of range to some access points may not be available to mobile stations of a location server 511.
For example, a wireless LAN access point is located inside building 701. While SPS signals (e.g., signals from SPS satellites 741-745) and wireless cellular phone signals (e.g., signals from cellular base station 751) may be weak inside building 701, the position of a mobile station can be easily determined (e.g., without using the signals from access point 703) at certain locations around the building (e.g., locations 711-725, which may be just outside the building or at certain locations inside the building, such as spots close to windows). In one embodiment of the present invention, the identification of the access point is determined and sent to the server with the location of the mobile station (or information specifying the location of the mobile, such as pseudoranges to in-view satellites) for the determination of the coverage area (and/or the position) of the access point 703. The location information of the access point (e.g., coverage area and/or position) can be maintained at the server (or a different server). When a mobile station is inside a building (or at a position near the building), where the blockage of some of the SPS signals and cellular phone signals occurs, the location information about the access point can be used to aid in determining the position of the mobile station.
It is understood that some access points may be moved from one location to another. In one embodiment of the present invention, the server tracks the collected position information about one or more mobile stations that receive the transmission from one access point in order to determine if the access point is moved. For example, the server may compare the old coverage area with the recent coverage area (e.g., through comparing the center and the radius of the coverage area) to determine if the access point is moved. Alternatively, the server may periodically discard old information in view of newly collected information. Further, the server may weight the collected information so that the freshly collected data carries more weight in determining the coverage area and/or the location of the access point and the influence from the data collected previously may eventually diminish over time. Further, the server may determine if an access point moves frequently; and, if the access point moves frequently, the access point may be disqualified as a reference point for the position determination. Further, in one embodiment, when an access point has not been observed for a certain period of time, the access point is removed from the database; similarly, when a new access point is observed, it is added to the database. Thus, the server may update the information about the access point in an ongoing basis.
In at least one embodiment of the present invention, a mobile station can determine its position without a communication link. The mobile station has memory for storing at least some of the information about the locations of the mobile station and the corresponding received signal levels or range measurements of a number of wireless access points (e.g., for cellular phone access or for wireless LAN access). The mobile station transmits the data to a server when a communication link (e.g., a wire connection through a communication port of the mobile station or a wireless connection through a transceiver of the mobile station) is available. Alternatively, the mobile station may directly use the stored information to derive the position information about the access point in determining its own position when needed.
The first wireless network in
Although the methods and apparatus of the present invention have been described with reference to GPS satellites, it will be appreciated that the descriptions are equally applicable to positioning systems, which utilize pseudolites or a combination of satellites and pseudolites. Pseudolites are ground-based transmitters, which broadcast a PN code (similar to a GPS signal), typically modulated on an L-band carrier signal, generally synchronized with GPS time. Each transmitter may be assigned a unique PN code so as to permit identification by a remote receiver. Pseudolites are useful in situations where GPS signals from an orbiting satellite might be unavailable, such as tunnels, mines, buildings or other enclosed areas. As used herein, the term “satellite” is intended to include pseudolites or equivalents of pseudolites and the term GPS signals is intended to include GPS-like signals from pseudolites or equivalents of pseudolites.
In the preceding discussion the invention has been described with reference to application upon the United States Global Positioning Satellite (GPS) system. It should be evident, however, that these methods are equally applicable to similar satellite positioning systems, and in particular, the Russian GLONASS system and the proposed European Galileo System. The GLONASS system primarily differs from GPS system in that the emissions from different satellites are differentiated from one another by utilizing slightly different carrier frequencies, rather than utilizing different pseudorandom codes. In this situation substantially all the circuitry and algorithms described previously are applicable. The term “GPS” used herein includes such alternative satellite positioning systems, including the Russian GLONASS system and the European Galileo System.
Although the operations in the above examples are illustrated in specific sequences, from this description, it will be appreciated that various different operation sequences and variations can be used without having to be limited to the above illustrated examples.
The above examples are illustrated without presenting some of the details known in the art; as pointed out in the above discussion, these details can be found in publications, such as U.S. Pat. Nos. 5,812,087, 5,841,396, 5,874,914, 5,945,944, 5,999,124, 6,061,018, 6,208,290 and 6,215,442, all of which are hereby incorporated here by reference.
In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
This application claims priority to and is a divisional of U.S. patent application Ser. No. 13/354,235, filed Jan. 19, 2012, which claims priority to and is a continuation of U.S. patent application Ser. No. 10/877,205, filed Jun. 25, 2004, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/483,094, filed Jun. 27, 2003, each of which is expressly incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 60483094 | Jun 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13354235 | Jan 2012 | US |
| Child | 14505095 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10877205 | Jun 2004 | US |
| Child | 13354235 | US |
