Abstract:
A mobile terminal capable of operating in a plurality of position tracking modes. The mobile terminal comprises: 1) a Global Positioning System (GPS) unit capable of receiving GPS signals from a plurality of GPS satellites, wherein the GPS unit is further capable of operating in i) a device autonomous fix (DAF) mode, ii) a server-computed assisted fix (SCAF) mode, and iii) a device-computed assisted fix (DCAF) mode. The mobile terminal also comprises: 2) a network transceiver capable of communicating with at least one terrestrial wireless network; and 3) a controller capable of controlling the operating mode of the GPS unit. The controller is capable of transitioning the GPS unit between the DAF mode, the SCAF mode, and the DCAF mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY  
       [0001]     The present application is related to U.S. Provisional Patent No. 60/754,436, filed Dec. 28, 2005, entitled “Apparatus And Method For Controlling Autonomous And Assisted GPS Modes In A Wireless Mobile Terminal” and U.S. Provisional Patent No. 60/754,359, filed Dec. 28, 2005, entitled “Wireless Mobile Terminal Using Sensors For Controlling Autonomous And Assisted GPS Modes”. U.S. Provisional Patent Nos. 60/754,436 and 60/754,359 are assigned to the assignee of the present application and are hereby incorporated by reference into the present disclosure as if fully set forth herein. The present application hereby claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Nos. 60/754,436 and 60/754,359.  
         [0002]     The present application is also related to U.S. Patent Application Ser. No. [GABR01-00003], entitled “Wireless Mobile Terminal Using Sensors For Controlling Autonomous And Assisted GPS Modes,” and filed concurrently herewith. U.S. patent application Ser. No. [GABR01-00003], is hereby incorporated by reference as if fully set forth herein.  
     
    
     TECHNICAL FIELD OF THE INVENTION  
       [0003]     The present invention relates generally to GPS location devices and, more specifically, to a mechanism for switching a GPS mobile terminal between full autonomous mode and assisted GPS modes.  
       BACKGROUND OF THE INVENTION  
       [0004]     The Global Positioning System (GPS) is a location system that uses signals transmitted by satellites orbiting the earth. Because the GPS satellites provide accurate positioning 24 hours a day anywhere on earth, GPS technology has gained widespread use over the last decade in commercial and military applications. GPS receivers capable of determining geographic position are implemented in cell phones, laptop computers, PDA devices, automobiles and other vehicles, aircraft, and as stand-alone portable devices that may be worn or carried by a person or animal.  
         [0005]     A GPS receiver determines its own position based on the signals transmitted by a select number of satellites that the GPS receiver is capable of receiving. The orbits and locations of GPS satellites are known in advance. This satellite position information is stored in a first data record known as the “almanac”. Each GPS satellite continually broadcasts the almanac information in a standard message to GPS receivers on earth. Each GPS receiver automatically collects and stores the almanac information from each satellite that the GPS receiver is able to detect.  
         [0006]     However, the orbits of GPS satellites do not perfectly follow the almanac information. Ground-based radar stations monitor the naturally-occurring deviations between the actual position of each GPS satellite and the predicted information in the almanac. This deviation information is stored in a second data record known as the ephemeris. The ephemeris errors for a GPS satellite are transmitted to that GPS satellite, which in turn broadcasts the ephemeris errors as part of the standard message to GPS receivers on earth. Almanac information is useful for about one year before it must be updated. Ephemeris data is useful for about two hours before it must be updated.  
         [0007]     Each GPS receiver uses the almanac information and the ephemeris data to determine very precisely the position of a GPS satellite at a given point in time. Once the positions of several GPS satellites are precisely known, a GPS receiver is able to determine the distance to each of the satellites according to the amount of time it takes the GPS signal to travel from the satellite to the GPS receiver. The GPS receiver then uses the distance information for several satellites to determine very precisely the position of the GPS receiver on earth. The GPS receiver information may include latitude information, longitude information, and altitude information (i.e., height above sea level).  
         [0008]     The foregoing description is characteristic of a GPS receiver that operates in an autonomous mode. An autonomous GPS receiver determines its position entirely on its own, using only the signals from the GPS satellites. For the purposes of this disclosure, the autonomous mode of operation may also be referred to as “device autonomous fix (DAF)”. However, some GPS receivers operate in an assisted GPS (aGPS) mode. In assisted GPS mode, a GPS receiver may receive almanac and ephemeris data, and even position information, from a terrestrial (i.e., ground-based) network with which the GPS receiver may communicate by means of a wireless connection or a wireline connection. For example, a cell phone or wireless PDA containing a GPS receiver may communicate with a public or private wide-area network (WAN) using the CDMA2000 protocol, the GSM protocol, or the IEEE-802.11 protocol (or a similar Wi-Fi protocol.  
         [0009]     There are two broad categories under which an assisted GPS receiver may fall. In a first category, a terrestrial network delivers GPS correlation parameters to the measurement engine (ME) of the GPS receiver. The measurement engine uses the correlation parameters to direct the correlators of the GPS receiver to specific search regions for the expected time and frequency offsets for each visible satellite. The measured time and frequency offsets are often called pseudo-ranges (PRs) and pseudo-Dopplers (PDs). Frequently, the set of measured correlation parameters are collectively referred to as pseudo-ranges, even though these parameters include both frequency offset measurements and other parameters.  
         [0010]     However, the correlation search parameters may become stale very quickly, within 5 minutes or so. To overcome this problem, first and second order correction factors may be sent along with the correlation search parameters in order to allow the GPS receiver to correct for differences between the time at which the correlation data was created and the time at which the correlation data will be used. However, in this first category of assisted GPS mode, the actual calculation of true range, Doppler, time, and accurate position information is completed at a network server with receives from the GPS receiver the approximate location of the GPS receiver, its measured pseudo-range (PR) and pseudo-Doppler (PD) information, and the apparent GPS time at which the pseudo-range (PR) and pseudo-Doppler (PD) information was captured.  
         [0011]     Thus, in this first category of aGPS devices, the terrestrial network sends GPS correlation parameters to the measurement engine (ME) of the GPS receiver. The measurement engine of the GPS receiver then sends approximate location, measured pseudo-range and pseudo-Doppler information, and apparent GPS time to the terrestrial network. The server in the terrestrial network uses the information received from the GPS receiver to calculate true range, Doppler, time, and position information and returns this information to the GPS receiver. For the purposes of this disclosure, this first category of assisted GPS mode of operation may also be referred to as “server-computed assisted fix (SCAF)”.  
         [0012]     In the second category of assisted GPS mode of operation, the terrestrial network delivers to the GPS receiver almanac and ephemeris information that would otherwise be obtained from the GPS satellites at a low rate of 50 bits/second. The terrestrial network delivers the almanac and ephemeris record at a much higher data rate. The GPS receiver operates both a measurement engine (ME) as before and a position engine (PE). The position engine receives the pseudo-range information captured by the measurement engine and calculates the solutions to the GPS equations yielding true range, Doppler, time and position information for the given output of the measurement engine and the ephemeris tables for each visible satellite. This second category of assisted GPS is mobile terminal (MT) based. For the purposes of this disclosure, this second category of assisted GPS mode of operation may also be referred to as “device-computed assisted fix (DCAF)”. Also, as ephemeris tables become stale, the GPS receiver may request updated tables from the terrestrial network or may transition from DCAF to full autonomous mode (i.e., DAF).  
         [0013]     Unfortunately, most GPS receiver chipsets operate in only one of the available modes: DAF, DCAF, or SCAF. For example, stand-alone GPS units from Magellan or Garmin are typically DAF only. Most of the E911 elements built into CDMA mobile phones operate only in SCAF mode. Many of the GPS units based on the SiRFSTAR model operate only in the DCAF mode.  
         [0014]     However, newer GPS chipsets, such as the Texas Instruments TSL5001, can operate in any of the three modes. However, network configurations do not support a single device that operates in any of the three modes or that can shift dynamically between these modes on a single network. Moreover, while it is relatively easy to transition from the DCAF mode to the DAF mode on the TWL5001 chipsets, transitioning from SCAF to either DCAF or DAF is not straightforward.  
         [0015]     Therefore, there is a need in the art for an improved GPS receiver that is able to switch between autonomous mode and assisted mode and terrestrial networks that support such mode switching.  
       SUMMARY OF THE INVENTION  
       [0016]     To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide a mobile terminal capable of operating in a plurality of position tracking modes. According to an advantageous embodiment of the present invention, the mobile terminal comprises: 1) a Global Positioning System (GPS) unit capable of receiving GPS signals from a plurality of GPS satellites, wherein the GPS unit is further capable of operating in i) a device autonomous fix (DAF) mode, ii) a server-computed assisted fix (SCAF) mode, and iii) a device-computed assisted fix (DCAF) mode; 2) a network transceiver capable of communicating with at least one terrestrial wireless network; and 3) a controller capable of controlling the operating mode of the GPS unit, wherein the controller is capable of transitioning the GPS unit between the DAF mode, the SCAF mode, and the DCAF mode.  
         [0017]     According to one embodiment of the present invention, the controller is capable of accessing via the network transceiver a first remote server associated with the terrestrial wireless network when the GPS unit is operating in the SCAF node, and wherein the controller receives from the first remote server correlation parameters to be used by the GPS unit.  
         [0018]     According to another embodiment of the present invention, the controller is capable of accessing via the network transceiver a second remote server not associated with the terrestrial wireless network when the GPS unit is operating in the SCAF node, and wherein the controller receives from the second remote server correlation parameters to be used by the GPS unit.  
         [0019]     According to still another embodiment of the present invention, the controller is capable of accessing via the network transceiver a first remote server associated with the terrestrial wireless network when the GPS unit is operating in the DCAF node, and wherein the controller receives from the first remote server almanac information and ephemeris information to be used by the GPS unit.  
         [0020]     According to yet another embodiment of the present invention, the controller is capable of accessing via the network transceiver a second remote server not associated with the terrestrial wireless network when the GPS unit is operating in the DCAF node, and wherein the controller receives from the second remote server almanac information and ephemeris information to be used by the GPS unit.  
         [0021]     According to a further embodiment of the present invention, the controller accesses the second remote server if the first remote server does not support the DCAF mode of operation of the GPS unit.  
         [0022]     According to a still further embodiment of the present invention, the at least one terrestrial wireless network comprises a wide-area network.  
         [0023]     According to a yet further embodiment of the present invention, the at least one terrestrial wireless network comprises a short-range wireless network.  
         [0024]     Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:  
         [0026]      FIG. 1  illustrates a mobile terminal having GPS capability operating in a wireless network environment according to the principles of the present invention;  
         [0027]      FIG. 2  illustrates the GPS-capable mobile terminal in  FIG. 1  in greater detail according to an exemplary embodiment of the present invention; and  
         [0028]      FIG. 3  illustrates a procedure by which the GPS-capable mobile terminal in  FIG. 1  obtains position information and transitions between GPS modes according to the principles of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]      FIGS. 1 through 3 , discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged communications network having assisted GPS capability.  
         [0030]      FIG. 1  illustrates GPS-capable mobile terminal  110  operating in a wireless network environment according to the principles of the present invention. Mobile terminal (MT)  110  comprises a Global Positioning System (GPS) unit capable of receiving GPS signals from a constellation of GPS satellites, including exemplary GPS satellites  115   a  and  115   b , and determining the position of MT  110 . MT  110  further comprises at least one radio-frequency (RF) transceiver capable of communicating with one or more types of terrestrial wireless networks, including both wide-area networks (WANs) and short-range networks, also called personal area networks (PANs).  
         [0031]     Mobile terminal  110  may comprise any one of a wide variety of electronic devices, including cell phones, laptop computers, PDA devices, and the like. Mobile terminal  110  also may be a component device, such as a navigation system, implemented in an automobile or other vehicle, a boat or an aircraft. Mobile terminal  110  also may be a stand-alone portable device that is worn or carried by a person or animal, or is hidden within another device or object. For example, mobile terminal  110  may be an anti-theft tracking device embedded within an automobile.  
         [0032]     For example, in one embodiment, mobile terminal  110  is capable of communicating with base stations  120   a  and  120   b  of wireless network  101  (indicated by dotted line), which may be a public cellular wide area network (WAN) according to, for example, CDMA protocol, GSM protocol, or the like. In another embodiment, wireless network  101  may be a public or private wireless network according to, for example, OFDMA protocol or IEEE-802.16, or the like. In still another embodiment, wireless network  101  may be a two-way paging network, such as a ReFLEX paging network. In yet another embodiment, mobile terminal  110  is also capable of communicating with access point (AP)  150  of a short range wireless network, according to, for example, IEEE-802.11 protocol, Bluetooth protocol, or a similar WiFi protocol. Access point  150  and router  155  may be implemented in a home or office in order to provide access to Internet  140 .  
         [0033]     Mobile terminal  110  may use different types of RF transceivers to communicate with different types of terrestrial wireless networks. However, according to an advantageous embodiment of the present invention, mobile terminal  110  may communicate with terrestrial wireless networks using at least one reconfigurable RF transceiver based on software-defined radio (SDR) architecture. For example, mobile terminal  110  may use a first SDR transceiver to communicate with wide area networks according to at least CDMA protocol and GSM protocol and may use a second SDR transceiver to communicate with WiFi networks according to at least Bluetooth protocol and IEEE-802.11 protocol. In still another embodiment of the present invention, mobile terminal  110  may use a single SDR transceiver to communicate with both wide-area networks and short-range networks. Moreover, mobile terminal  110  is capable of supporting both voice traffic, as in older IS-95 and GSM networks, and data traffic, especially IP packets, as in newer OFDMA and IEEE-802.16 networks.  
         [0034]     According to the principles of the present invention, the GPS unit in mobile terminal  110  is capable of operating in both autonomous GPS mode (i.e., DAF) and assisted GPS modes (i.e., SCAF and DCAF). In an exemplary embodiment, the GPS unit in mobile terminal  110  may be based on a Texas Instruments TSL5001 chipset that can operate in device autonomous fix (DAF) mode, device computed assisted fix (DCAF) mode, or server computed assisted fix (SCAF) mode. In DCAF or SCAF mode, mobile terminal  110  may receive GPS assistance from position determining server (PDS)  130 , which is associated with wireless network  101 . PDS  130  and base stations  120   a  and  120   b  communicate via wireline network  121 , which may be, for example, a Gigabit Ethernet or a similar wireline network.  
         [0035]     However, if the capabilities of PDS  130  do not match the capabilities of mobile terminal  110 , mobile terminal  110  may receive GPS assistance from position determining server (PDS)  135 , which is not associated with wireless network  101 . For example, mobile terminal  110  may normally operate in SCAF mode in its home network. However, if mobile terminal  110  is roaming in wireless network  101  and PDS  130  provides supports only for DCAF mode, mobile terminal  110  accesses PDS  135  in order to obtain SCAF support. Mobile terminal  110  may access PDS  135  via base station  120  of wireless network  101  and Internet  140 . Alternatively, if mobile terminal (MT)  110  is relatively close to access point (AP)  150 , MT  110  may access Internet  140  via AP  150  and router  155 .  
         [0036]      FIG. 2  illustrates GPS-capable mobile terminal  110  in greater detail according to an exemplary embodiment of the present invention. Mobile terminal (MT)  110  comprises GPS unit  210 , radio frequency (RF) network transceiver  220 , input/output interface (I/O IF)  230 , user graphical user interface  240 , controller processor  250 , and memory  260 . Memory  260  comprises both volatile and non-volatile memories that store operating system (OS) program  261 , GPS mode control program  262 , device autonomous fix (DAF) data file  263 , server-computed assisted fix (SCAF) date file  264 , and device-computed assisted fix (DCAF) date file  265 .  
         [0037]     Together, controller processor  250  and memory  260  comprise a controller that controls the overall operation of mobile terminal  110  and the operations of the components parts of MT  110 . Control processor  250  executes control GPS mode control program  262  in order to control the transition of MT  110  between DAF, DCAF and SCAF modes. User GUS  240  comprises a display and some type of manual input device for the user, such as a keyboard, a touch screen, a mouse, or the like. Control processor  250  may communicate with external peripheral devices and/or networks via I/O IF  230 .  
         [0038]     RF network transceiver  220  comprises at least one reconfigurable RF transceiver based on software-defined radio (SDR) architecture that is capable of communicating with terrestrial wireless networks. In an advantageous embodiment of the present invention, RF network transceiver  220  may comprise a first reconfigurable SDR transceiver that communicates with different types of wide-area networks (including wireless network  101 ), according to at least two wide-range communication protocols. RF network transceiver  220  also may comprise a second reconfigurable SDR transceiver that communicates with different types of short-range (or WiFi) networks according to at least two short-range communication protocols. In still another embodiment of the present invention, transceiver  220  may comprises a single reconfigurable SDR transceiver that communicates with both wide-area networks and short-range networks.  
         [0039]     GPS unit  211  comprises receiver section  211 , measurement engine  212 , and position engine  213 . Receiver section  211  receives and down-converts the incoming GPS signals from several of the satellites  115  in the constellation of GPS satellites. In SCAF mode, measurement engine  212  uses correlation parameters received from a terrestrial network (i.e., PDS  130  or PDS  135 ) to direct the correlators of receiver section  211  to specific regions for the expected time and frequency offsets for each visible satellite. To compensate for stale correlation search parameters, measurement engine  212  also provides receiver section  211  with first-order and second-order correction factors to correct for differences between the time at which the correlation data was created and the time at which the correlation data will be used. Alternatively, the mobile terminal may employ its processor and an algorithm for the application of the correction factors to the nominal correlation search parameters in order to compensate for any significant difference in the intended and actual times of application. In such an embodiment, the corrected correlation search parameters would be delivered to the GPS unit.  
         [0040]     Measurement engine  212  stores the measured time and frequency offsets, or pseudo-ranges (PRs) and pseudo-Dopplers (PDs), in SCAF data file  254  via control processor  250 . Control processor  250  also relays the information stored in SCAF data file  254  to RF network transceiver  220 . Transceiver  220  transmits the information from SCAF data file  254  to PDS  130  or PDS  135 . The actual calculation of true range, Doppler, time, and accurate position information is completed at PDS  130  (or PDS  135 ). Then, PDS  130  (or PDS  135 ) transmits the true range data, Doppler data, time data, and accurate position information back to MT  110  via wireless network  101  or via AP  150 , as the case may be.  
         [0041]     In DCAF mode, measurement engine  212  uses almanac and ephemeris information from the terrestrial network (i.e., PDS  130  or PDS  135 ) at a high data rate. Position engine  213  receives the pseudo-range (and pseudo-Doppler) information captured by measurement engine  212  and calculates the solutions to the GPS equations yielding true range, Doppler, time and position information for the given output of measurement engine  212  and the ephemeris tables for each visible satellite. Position engine  213  then stores this data in DCAF data file  265  via control processor  250 .  
         [0042]     In DAF mode, mobile terminal  110  does not use any information received from the terrestrial network to determine position. Instead, measurement engine  212  receives almanac and ephemeris information at a low data rate (e.g., 50 bits/second) directly from GPS satellites  115  and measures pseudo-range and pseudo-Doppler information. Position engine  213  then the pseudo-range and pseudo-frequency information to calculate true range, Doppler, time and position information for the given output of measurement engine  212  and the ephemeris tables for each visible satellite. The calculated information is then stored in DAF data file  263 . This means of determining position requires the most time to acquire a first position fix.  
         [0043]      FIG. 3  depicts flow diagram  300 , which illustrates a procedure by which mobile terminal  110  obtains position information and transitions between GPS modes according to the principles of the present invention. Initially, it is assumed that mobile terminal  110  goes through a boot-up procedure after a cold-start (process step  305 ). After the boot-up procedure is completed, mobile terminal  110  searches for, and attempts to access, either a base station of wireless network  101  or access point  150 , or both (process step  310 ). If a terrestrial network is not found (process step  315 ), mobile terminal  110  may enter DAF mode, if desired (process step  320 ). MT  110  may enter DAF mode in response to a user prompt or in response to an internal event in MT  110 , such as the expiration of a timer.  
         [0044]     If a terrestrial network is found (process step  315 ) mobile terminal  110  may enter SCAF mode in response to a user prompt, in response to an internal event in MT  110 , or in response to a command or other message received from the terrestrial network (process step  325 ). Alternatively, if the capabilities of PDS  130  don not support SCAF mode, MT  110  may access PDS  135  in order to enter SCAF mode. If PDS  135  also does not support SCAF mode, MT  110  may enter DCAF mode.  
         [0045]     After performing an SCAF operation, MT  110  finally obtains an accurate first position fix (process step  330 ). Thereafter, mobile terminal may remain in SCAF mode. Alternatively, mobile terminal  110  may transition from SCAF mode to DCAF mode or to DAF mode in response to a user prompt, in response to an internal event in MT  110 , or in response to a command or other message received from the terrestrial network. At some later point, mobile terminal  110  may transition from DCAF mode to DAF mode (or vice versa) in response to a user prompt, in response to an internal event in MT  110 , or in response to a command or other message received from the terrestrial network (process step  335 ).  
         [0046]     Although the present invention has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.