Abstract:
Techniques for use in a mobile device for obtaining location information with use of a Global Positioning System (GPS) involve receiving, through a user interface of the mobile device, a voice call request for establishing a voice call; and in response to receiving the voice call request: comparing a selected telephone number of the voice call request with one or more predetermined telephone numbers stored in memory of the mobile device; if the selected telephone number matches one of the predetermined telephone numbers stored in the memory: prior to initiating the voice call, performing a GPS fix with the GPS system for obtaining the location information of the mobile device; if the selected telephone number fails to match one of the predetermined telephone numbers stored in the memory: refraining from performing the GPS fix for obtaining the location information of the mobile device prior to establishing the voice call; and initiating the voice call from the mobile device via a wireless network.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. non-provisional patent application having application Ser. No. 12/331,760 and filing date of 10 Dec. 2008, now U.S. Pat. No. 7,912,483 B2, which is a continuation of and claims priority to U.S. non-provisional patent application having application Ser. No. 10/789,571 and filing date of 27 Feb. 2004, now U.S. Pat. No. 7,477,906 B2, each application being hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to wireless communications involving mobile stations, and more particularly to methods and apparatus for facilitating the determination of Global Positioning System (GPS) location information of a mobile station without disrupting voice communications of a voice call. 
     2. Description of the Related Art 
     Present-day wireless communication devices, such as cellular telephones or mobile stations, are capable of making and receiving voice calls and/or sending and receiving data through wireless communication networks. Fairly recent developments have given such mobile stations the ability to communicate Global Positioning System (GPS) location information which is indicative of the exact location of the mobile station. To reduce cost and complexity at the mobile station, this may be done using the same RF transceiver utilized for typical voice and data communications (or by sharing at least a portion thereof) without the need for a completely separate GPS transceiver (i.e. separate hardware). 
     Among the adopted position location technologies for Enhanced 911 (E911), Assisted GPS (A-GPS) is one of the solutions. For current Code Division Multiple Access (CDMA) systems, such GPS techniques are described in standard specification documents such as TIA/EIA/IS-801-1 of November 2000. During a voice call involving the mobile station, real-time GPS location information may be obtained and sent to a receiving entity. To obtain real-time GPS location information, the mobile station receives the signals from a GPS system as well as communicates with a location server in the wireless communication network. The location server may include a Position Determination Entity (PDE) which has a GPS receiver for wirelessly receiving information from the GPS system. The mobile station obtains GPS acquisition assistance data and uses it to perform what is referred to as a “GPS fix” during a voice call. During the GPS fix, the mobile station tunes to a GPS frequency different from the traffic channel of the voice call in order to obtain GPS pseudorange data from the GPS system. The mobile station obtains the GPS pseudorange data by measuring GPS signal delays at the mobile. After the GPS fix, the mobile station retunes back to the traffic channel of the voice call. Sometime during the voice call, the mobile station sends the GPS pseudorange data to the location server which calculates the location of the mobile station based on it. The location server/PDE may send the location of the mobile station to the receiving entity (e.g. 911 emergency center or PSAP) or, if received by the mobile station, the mobile station may send the location of the mobile station to the receiving entity. 
     Note that the mobile station may have to tune away from the voice call anywhere between about 300 milliseconds to 2 seconds, for example. As apparent, voice communications of the voice call are undesirably disrupted with use of the conventional procedure. Also, the conventional procedure undesirably increases the chances of the voice call being dropped. The processes also cause power control variations that can reduce system capacity. In the case where the voice call is very important, such as the 911 emergency call, these issues are of great concern. 
     Accordingly, there is a resulting need for methods and apparatus for facilitating the determination of GPS location information for a mobile station without disrupting voice communications of a voice call so as to overcome the deficiencies of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of present invention will now be described by way of example with reference to attached figures, wherein: 
         FIG. 1  is a block diagram which illustrates pertinent components of a wireless communication network and a mobile station which communicates with this network as well as with a Global Positioning System (GPS); 
         FIG. 2  is a more detailed diagram of the mobile station which may communicate within the wireless communication network; 
         FIG. 3  is a flowchart for use in describing a method of facilitating the determination of GPS location information for the mobile station without disrupting communications of a voice call (e.g. a 911 emergency voice call) involving the mobile station; 
         FIG. 4  is a system flow diagram for use in describing the method associated with  FIG. 3 ; 
         FIG. 5  is a flowchart for use in describing another method of facilitating the determination of GPS location information for the mobile station without disrupting communications of a voice call (e.g. a 911 emergency voice call) involving the mobile station; and 
         FIG. 6  is a system flow diagram for use in describing the method associated with  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Methods and apparatus for facilitating the determination of Global Positioning System (GPS) location information for a mobile station without disrupting communications of a voice call (e.g. a 911 emergency call) are disclosed. In one illustrative example, the mobile station causes GPS navigational-type data to be regularly or periodically received through a wireless receiver and stored in memory prior to the voice call. At some point in time, the mobile station receives, through a user interface, a voice call request to initiate the voice call through a wireless communication network. In response, the mobile station calculates GPS assistance data based on the stored GPS navigational-type data. The mobile station then causes a GPS fix to be performed with a GPS system using the GPS assistance data. The mobile station obtains GPS measurement data based on GPS signals received with the wireless receiver during the GPS fix. Thereafter, the mobile station causes the voice call to be established and maintained through the wireless communication network. The GPS measurement data is then transmitted from the mobile station to a location server in the wireless communication network for calculating the location of the mobile station. Thereafter, the location server may send the location to the requesting entity or, alternatively, the location server may send the location to the mobile station which then sends it to the requesting entity. Advantageously, the mobile station is operative to refrain from causing the GPS fix to be performed during the voice communications of the voice call so that the communications are not disrupted. 
       FIG. 1  is a block diagram of a communication system  100  which includes a mobile station  102  which communicates through a wireless communication network  104 . Mobile station  102  preferably includes a visual display  112 , a keyboard  114 , and perhaps one or more auxiliary user interfaces (UI)  116 , each of which is coupled to a controller  106 . Controller  106  is also coupled to radio frequency (RF) transceiver circuitry  108  and an antenna  110 . 
     Typically, controller  106  is embodied as a central processing unit (CPU) which runs operating system software in a memory component (not shown). Controller  106  will normally control overall operation of mobile station  102 , whereas signal processing operations associated with communication functions are typically performed in RF transceiver circuitry  108 . Controller  106  interfaces with device display  112  to display received information, stored information, user inputs, and the like. Keyboard  114 , which may be a telephone type keypad or full alphanumeric keyboard, is normally provided for entering data for storage in mobile station  102 , information for transmission to network  104 , a telephone number to place a telephone call, commands to be executed on mobile station  102 , and possibly other or different user inputs. 
     Mobile station  102  sends communication signals to and receives communication signals from network  104  over a wireless link via antenna  110 . RF transceiver circuitry  108  performs functions similar to those of a radio network (RN)  128 , including for example modulation/demodulation and possibly encoding/decoding and encryption/decryption. It is also contemplated that RF transceiver circuitry  108  may perform certain functions in addition to those performed by RN  128 . It will be apparent to those skilled in art that RF transceiver circuitry  108  will be adapted to particular wireless network or networks in which mobile station  102  is intended to operate. 
     Mobile station  102  includes a battery interface  122  for receiving one or more rechargeable batteries  124 . Battery  124  provides electrical power to electrical circuitry in mobile station  102 , and battery interface  122  provides for a mechanical and electrical connection for battery  124 . Battery interface  122  is coupled to a regulator  126  which regulates power to the device. When mobile station  102  is fully operational, an RF transmitter of RF transceiver circuitry  108  is typically turned on only when it is sending to network, and is otherwise turned off to conserve resources. Similarly, an RF receiver of RF transceiver circuitry  108  is typically periodically turned off to conserve power until it is needed to receive signals or information (if at all) during designated time periods. 
     Mobile station  102  operates using a memory module  120 , such as a Subscriber Identity Module (SIM) or a Removable User Identity Module (R-UIM), which is connected to or inserted in mobile station  102  at an interface  118 . As an alternative to a SIM or an R-UIM, mobile station  102  may operate based on configuration data programmed by a service provider into a non-volatile memory of mobile station  102 . Mobile station  102  may consist of a single unit, such as a data communication device, a cellular telephone, a multiple-function communication device with data and voice communication capabilities, a personal digital assistant (PDA) enabled for wireless communication, or a computer incorporating an internal modem. Alternatively, mobile station  102  may be a multiple-module unit comprising a plurality of separate components, including but in no way limited to a computer or other device connected to a wireless modem. In particular, for example, in the mobile station block diagram of  FIG. 1 , RF transceiver circuitry  108  and antenna  110  may be implemented as a radio modem unit that may be inserted into a port on a laptop computer. In this case, the laptop computer would include display  112 , keyboard  114 , and one or more auxiliary UIs  116 . Controller  106  is either embodied as the computer&#39;s CPU or a separate CPU within the modem unit. It is also contemplated that a computer or other equipment not normally capable of wireless communication may be adapted to connect to and effectively assume control of RF transceiver circuitry  108  and antenna  110  of a single-unit device such as one of those described above. Such a mobile station  102  may have a more particular implementation as described later in relation to mobile station  202  of  FIG. 2 . 
     Mobile station  102  communicates in and through wireless communication network  104 . In the embodiment of  FIG. 1 , wireless network  104  is a Second Generation (2G) or Third Generation (3G) supported network based on Code Division Multiple Access (CDMA) technologies. In particular, wireless network  104  is a CDMA2000® network which includes fixed network components coupled as shown in  FIG. 1 . Wireless network  104  of the CDMA2000-type includes a Radio Network (RN)  128 , a Mobile Switching Center (MSC)  130 , a Signaling System 7 (SS7) network  140 , a Home Location Register/Authentication Center (HLR/AC)  138 , a Packet Data Serving Node (PDSN)  132 , an IP network  134 , and a Remote Authentication Dial-In User Service (RADIUS) server  136 . SS7 network  140  is communicatively coupled to a network  142  (such as a Public Switched Telephone Network or PSTN) which may connect mobile station  102  with other call parties such as a call party  150  (e.g. a landline telephone or other mobile station) or an emergency call center  152 . On the other hand, IP network  134  is communicatively coupled to another network  144  such as the Internet. Note that CDMA2000® is a registered trademark of the Telecommunications Industry Association (TIA-USA). 
     During operation, mobile station  102  communicates with RN  128  which performs functions such as call-setup, call processing, and mobility management. RN  128  includes a plurality of base station transceiver systems that provide wireless network coverage for a particular coverage area commonly referred to as a “cell”. A given base station transceiver system of RN  128 , such as the one shown in  FIG. 1 , transmits communication signals to and receives communication signals from mobile stations within its cell. The base station transceiver system normally performs such functions as modulation and possibly encoding and/or encryption of signals to be transmitted to the mobile station in accordance with particular, usually predetermined, communication protocols and parameters, under control of its controller. The base station transceiver system similarly demodulates and possibly decodes and decrypts, if necessary, any communication signals received from mobile station  102  within its cell. Communication protocols and parameters may vary between different networks. For example, one network may employ a different modulation scheme and operate at different frequencies than other networks. The underlying services may also differ based on its particular protocol revision. 
     The wireless link shown in communication system  100  of  FIG. 1  represents one or more different channels, typically different radio frequency (RF) channels, and associated protocols used between wireless network  104  and mobile station  102 . An RF channel is a limited resource that must be conserved, typically due to limits in overall bandwidth and a limited battery power of mobile station  102 . Those skilled in art will appreciate that a wireless network in actual practice may include hundreds of cells depending upon desired overall expanse of network coverage. All pertinent components may be connected by multiple switches and routers (not shown), controlled by multiple network controllers. 
     For all mobile station&#39;s  102  registered with a network operator, permanent data (such as mobile station  102  user&#39;s profile) as well as temporary data (such as mobile station&#39;s  102  current location) are stored in a HLR/AC  138 . In case of a voice call to mobile station  102 , HLR/AC  138  is queried to determine the current location of mobile station  102 . A Visitor Location Register (VLR) of MSC  130  is responsible for a group of location areas and stores the data of those mobile stations that are currently in its area of responsibility. This includes parts of the permanent mobile station data that have been transmitted from HLR/AC  138  to the VLR for faster access. However, the VLR of MSC  130  may also assign and store local data, such as temporary identifications. Mobile station  102  is also authenticated on system access by HLR/AC  138 . In order to provide packet data services to mobile station  102  in a CDMA2000-based network, RN  128  communicates with PDSN  132 . PDSN  132  provides access to the Internet  144  (or intranets, Wireless Application Protocol (WAP) servers, etc.) through IP network  134 . PDSN  132  also provides foreign agent (FA) functionality in mobile IP networks as well as packet transport for virtual private networking. PDSN  132  has a range of IP addresses and performs IP address management, session maintenance, and optional caching. RADIUS server  136  is responsible for performing functions related to authentication, authorization, and accounting (AAA) of packet data services, and may be referred to as an AAA server. 
     Wireless communication network  104  includes position tracking components for tracking the locations of mobile stations. Location information of mobile stations is obtained based on Global Positioning System (GPS) techniques utilizing GPS satellites of a conventional GPS system  154 . In the typical configuration, GPS system  154  includes twenty-four (24) GPS satellites that circle the earth every twelve (12) hours. In the present application, mobile station  102  obtains GPS information based on signals received from GPS system  154  and utilizes a location server  190  in wireless network  104  to measure and obtain its location. Location server  190  is connected to MSC  130  and/or IP network  134  and may include what is referred to as a Position Determination Entity (PDE). The PDE is coupled to a GPS receiver  192  for receiving signals and decoding information transmitted by GPS system  154 . Note that mobile station  102  can receive GPS information from GPS system  154  and location server  190  using the same RF transceiver  108  utilized for typical voice and data communications (or by sharing at least a portion thereof). Thus, a separate GPS receiver is not utilized in mobile station  102  for receiving GPS information from GPS system  154 . 
     Among the currently adopted position location technologies for Enhanced 911 (E911), Assisted GPS (A-GPS) is one of the solutions. Such GPS techniques are described in standard specification documents such as TIA/EIA/IS-801-1 of November 2000. During a voice call involving mobile station  102 , real-time GPS location information may be obtained and sent to a receiving entity. To obtain the GPS location information, mobile station  102  operates with GPS system  154  as well as location server  190  in wireless communication network  104 . Conventionally, mobile station  102  obtains GPS acquisition assistance data and uses it to perform what is referred to as a “GPS fix” during a voice call. For the GPS fix, mobile station  102  tunes to a GPS signal frequency of GPS system  154  which is different from the traffic channel frequency of the voice call. During the GPS fix, mobile station  102  performs GPS pseudorange measurements based on GPS signals received from GPS system  154 . After the GPS fix, mobile station  102  retunes back to the traffic channel of the voice call. Sometime during the voice call mobile station  102  sends the GPS pseudorange data to location server  190 , which derives the location of mobile station  102  based on it. Location server/PDE  190  may send this location information to the receiving entity and/or to mobile station  102 . If received by the mobile station, mobile station  102  may send the location information to the receiving entity. Note that, using the conventional method, mobile station  102  may have to tune away from the voice call one or more times and, for each time, from anywhere between 300 milliseconds to 2 seconds, for example. As apparent, voice communications of the voice call are undesirably disrupted with use of the conventional procedure. Also, the conventional procedure undesirably increases the chance that the voice call will be dropped. The processes also cause power control variations that can reduce system capacity. In the case where the voice call is very important, such as the 911 emergency call, these issues are of great concern. In accordance with teachings of the present application as described in more detail in relation to  FIGS. 3-4 , however, these issues can be alleviated. 
     Those skilled in art will appreciate that wireless network  104  may be connected to other systems, possibly including other networks, not explicitly shown in  FIG. 1 . A network will normally be transmitting at very least some sort of paging and system information on an ongoing basis, even if there is no actual packet data exchanged. Although the network consists of many parts, these parts all work together to result in certain behaviours at the wireless link. 
       FIG. 2  is a detailed block diagram of a preferred mobile station  202 . Mobile station  202  is preferably a two-way communication device having at least voice and advanced data communication capabilities, including the capability to communicate with other computer systems. Depending on the functionality provided by mobile station  202 , it may be referred to as a data messaging device, a two-way pager, a cellular telephone with data messaging capabilities, a wireless Internet appliance, or a data communication device (with or without telephony capabilities). Mobile station  202  may communicate with any one of a plurality of base station transceiver systems  200  within its geographic coverage area. Mobile station  202  selects or helps select which one of base station transceiver systems  200  it will communicate with, as will be described in more detail later in relation to  FIGS. 3 and 4 . 
     Mobile station  202  will normally incorporate a communication subsystem  211 , which includes a receiver  212 , a transmitter  214 , and associated components, such as one or more (preferably embedded or internal) antenna elements  216  and  218 , local oscillators (LOs)  213 , and a processing module such as a digital signal processor (DSP)  220 . Communication subsystem  211  is analogous to RF transceiver circuitry  108  and antenna  110  shown in  FIG. 1 . As will be apparent to those skilled in field of communications, particular design of communication subsystem  211  depends on the communication network in which mobile station  202  is intended to operate. 
     Mobile station  202  may send and receive communication signals over the network after required network registration or activation procedures have been completed. Signals received by antenna  216  through the network are input to receiver  212 , which may perform such common receiver functions as signal amplification, frequency down conversion, filtering, channel selection, and like, and in example shown in  FIG. 2 , analog-to-digital (A/D) conversion. A/D conversion of a received signal allows more complex communication functions such as demodulation and decoding to be performed in DSP  220 . In a similar manner, signals to be transmitted are processed, including modulation and encoding, for example, by DSP  220 . These DSP-processed signals are input to transmitter  214  for digital-to-analog (D/A) conversion, frequency up conversion, filtering, amplification and transmission over communication network via antenna  218 . DSP  220  not only processes communication signals, but also provides for receiver and transmitter control. For example, the gains applied to communication signals in receiver  212  and transmitter  214  may be adaptively controlled through automatic gain control algorithms implemented in DSP  220 . 
     Network access is associated with a subscriber or user of mobile station  202 , and therefore mobile station  202  requires a memory module  262 , such as a Subscriber Identity Module or “SIM” card or a Removable User Identity Module (R-UIM), to be inserted in or connected to an interface  264  of mobile station  202  in order to operate in the network. Alternatively, a portion of the non-volatile memory or flash memory  224  is programmed with configuration data by a service provider so that mobile station  202  may operate in the network. Since mobile station  202  is a portable battery-powered device, it also includes a battery interface  254  for receiving one or more rechargeable batteries  256 . Such a battery  256  provides electrical power to most if not all electrical circuitry in mobile station  202 , and battery interface  254  provides for a mechanical and electrical connection for it. Battery interface  254  is coupled to a regulator (not shown in  FIG. 2 ) which provides power to all of the circuitry. 
     Mobile station  202  includes a microprocessor  238  (which is one implementation of controller  106  of  FIG. 1 ) which controls overall operation of mobile station  202 . This control includes network selection techniques of the present application. Communication functions, including at least data and voice communications, are performed through communication subsystem  211 . Microprocessor  238  also interacts with additional device subsystems such as a display  222 , a flash memory  224 , a random access memory (RAM)  226 , auxiliary input/output (I/O) subsystems  228 , a serial port  230 , a keyboard  232 , a speaker  234 , a microphone  236 , a short-range communications subsystem  240 , and any other device subsystems generally designated at  242 . Some of the subsystems shown in  FIG. 2  perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. Notably, some subsystems, such as keyboard  232  and display  222 , for example, may be used for both communication-related functions, such as entering a text message for transmission over a communication network, and device-resident functions such as a calculator or task list. Operating system software used by microprocessor  238  is preferably stored in a persistent store such as flash memory  224 , which may alternatively be a read-only memory (ROM) or similar storage element (not shown). Those skilled in the art will appreciate that the operating system, specific device applications, or parts thereof, may be temporarily loaded into a volatile store such as RAM  226 . 
     Microprocessor  238 , in addition to its operating system functions, preferably enables execution of software applications on mobile station  202 . A predetermined set of applications which control basic device operations, including at least data and voice communication applications (such as a network re-establishment scheme), will normally be installed on mobile station  202  during its manufacture. A preferred application that may be loaded onto mobile station  202  may be a personal information manager (PIM) application having the ability to organize and manage data items relating to user such as, but not limited to, e-mail, calendar events, voice mails, appointments, and task items. Naturally, one or more memory stores are available on mobile station  202  and SIM  256  to facilitate storage of PIM data items and other information. 
     The PIM application preferably has the ability to send and receive data items via the wireless network. In a preferred embodiment, PIM data items are seamlessly integrated, synchronized, and updated via the wireless network, with the mobile station user&#39;s corresponding data items stored and/or associated with a host computer system thereby creating a mirrored host computer on mobile station  202  with respect to such items. This is especially advantageous where the host computer system is the mobile station user&#39;s office computer system. Additional applications may also be loaded onto mobile station  202  through network, an auxiliary I/O subsystem  228 , serial port  230 , short-range communications subsystem  240 , or any other suitable subsystem  242 , and installed by a user in RAM  226  or preferably a non-volatile store (not shown) for execution by microprocessor  238 . Such flexibility in application installation increases the functionality of mobile station  202  and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using mobile station  202 . 
     In a data communication mode, a received signal such as a text message, an e-mail message, or web page download will be processed by communication subsystem  211  and input to microprocessor  238 . Microprocessor  238  will preferably further process the signal for output to display  222  or alternatively to auxiliary I/O device  228 . A user of mobile station  202  may also compose data items, such as e-mail messages, for example, using keyboard  232  in conjunction with display  222  and possibly auxiliary I/O device  228 . Keyboard  232  is preferably a complete alphanumeric keyboard and/or telephone-type keypad. These composed items may be transmitted over a communication network through communication subsystem  211 . 
     For voice communications, the overall operation of mobile station  202  is substantially similar, except that the received signals would be output to speaker  234  and signals for transmission would be generated by microphone  236 . Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on mobile station  202 . Although voice or audio signal output is preferably accomplished primarily through speaker  234 , display  222  may also be used to provide an indication of the identity of a calling party, duration of a voice call, or other voice call related information, as some examples. 
     Serial port  230  in  FIG. 2  is normally implemented in a personal digital assistant (PDA)-type communication device for which synchronization with a user&#39;s desktop computer is a desirable, albeit optional, component. Serial port  230  enables a user to set preferences through an external device or software application and extends the capabilities of mobile station  202  by providing for information or software downloads to mobile station  202  other than through a wireless communication network. The alternate download path may, for example, be used to load an encryption key onto mobile station  202  through a direct and thus reliable and trusted connection to thereby provide secure device communication. 
     Short-range communications subsystem  240  of  FIG. 2  is an additional optional component which provides for communication between mobile station  202  and different systems or devices, which need not necessarily be similar devices. For example, subsystem  240  may include an infrared device and associated circuits and components, or a Bluetooth™ communication module to provide for communication with similarly-enabled systems and devices. Bluetooth™ is a registered trademark of Bluetooth SIG. 
       FIG. 3  is a flowchart for use in describing a method of facilitating the determination of Global Positioning System (GPS) location information for a mobile station without disrupting voice communications of a voice call (e.g. a 911 emergency call) involving the mobile station. Related in  FIG. 4  is a system flow diagram for use in describing the method. The method may be performed by a mobile station in connection with pertinent system components as described, using one or more processors, memory, and its RF transceiver (e.g. see  FIGS. 1-2 ). The method may further be embodied in a computer program product which includes a computer storage medium (e.g. memory or computer disk) having computer instructions stored therein which are executable by one or more processors (e.g. a microprocessor) of the mobile station. In the following description,  FIGS. 3 and 4  will be referred to in combination. 
     Beginning at a start block  300  of  FIG. 3 , the processor of mobile station  102  causes GPS navigational-type data to be regularly or periodically requested, received, and stored in memory of mobile station  102  during its idle mode of operation (step  302  of  FIGS. 3-4 ). Note that during typical idle mode operation, no voice call is being maintained nor is a traffic channel established between mobile station  102  and wireless communication network  104  (except for that utilized in connection with the receipt of the GPS navigational-type data through the wireless network as will be described below). The regular or periodic requesting, receiving, and storage of GPS navigational-type data may be performed once every 30 minutes to 4 hours, for example, or for shorter or longer intervals if suitable. 
     The GPS navigational-type data may be “raw” navigational data or, alternatively, data derived from the raw navigational data which may include GPS ephemeris parameter data and/or GPS almanac parameter data. Hence the term, “navigational-type” data. The GPS navigational-type data may be received from location server  190  through the wireless network or, alternatively, directly from GPS system  154 . Preferably, mobile station  102  regularly or periodically requests and receives downloads of the GPS ephemeris data and/or GPS almanac data from location server  190 . To do this, mobile station  102  may have to send location server  190  information related to its coarse location as indicated by pilot phase measurements (PPMs). Thus, PPMs may also be regularly or periodically performed by mobile station  102  at the time the mobile station sets up traffic channel for requesting GPS navigational-type data from location server  190 . The PPM data are sent to location server  190  together with the request for downloading GPS navigational-type data. Note that location server/PDE  190  utilizes a triangulation/trilateration procedure based on the PPMs to obtain the coarse location of mobile station  102  in order to derive the GPS acquisition assistance information for mobile station  102 . Alternatively, the longitude and latitude of the serving base station(s) that may be available from broadcasted messages from the base station(s) may be used as the coarse location for location server/PDE  190  to derive the GPS acquisition assistance information for mobile station  102 . 
     During the idle mode, the processor of mobile station  102  also monitors to identify from the user interface whether a voice call request is detected (step  304  of  FIGS. 3-4 ). This step  304  may include monitoring to identify a potential voice call request within an upcoming foreseeable time period which is relatively short (e.g. within a few seconds of time). The detection of the voice call request may be based on one or more specific actions taken at the user interface by the end user. For example, the detection may be based on the end user invoking or starting a phone application, prior to entering or dialing a phone number. As another example, the detection may be based on the end user entering telephone digits or the telephone number of the voice call, which may include the actuation or selection of the SEND or ENTER key of the user interface. As even another example, the detection may be based on the end user removing the mobile station from a holster or a battery-charging unit for placing the voice call. Other triggering conditions include the end user powering up the mobile station. If the mobile station functions as a modem utilized by a personal computer (PC) or laptop, the triggering may occur from an application on the PC or laptop. Even further, the detection may include a combination of two or more of the above trigger mechanisms. 
     If the voice call request is not detected at step  302 , then the mobile station continues such monitoring. If the voice call request is detected at step  302 , the processor of mobile station  102  performs a GPS procedure for obtaining GPS location information. In particular, the processor of mobile station  102  derives GPS acquisition assistance data and/or sensitivity assistance data based on the last previous GPS navigational-type data received and stored in memory (step  306  of  FIGS. 3-4 ). GPS acquisition assistance data includes data that identifies the appropriate surrounding GPS satellites (e.g. in the form of PseudoRandom Noise or “PRN” code numbers), Doppler frequencies, and time delay window information. Sensitivity assistance data includes predicted bit contents of the GPS navigational data that will be modulated onto the GPS signals at the time the GPS fix is going to be performed. Next, the processor of mobile station  102  causes a GPS fix to be performed with GPS system  154  (step  308  of  FIGS. 3-4 ). During the GPS fix, the wireless receiver of mobile station  102  is tuned to a GPS frequency to receive GPS signals from GPS system  154 . Mobile station  102  obtains GPS measurement data associated with mobile station  102  based on the GPS signals received from GPS system  154 . The GPS measurement data may be or include GPS pseudorange data. Note that no call-setup procedures for the voice call have yet been performed. The time it takes to perform the GPS fix with the wireless receiver may vary but it is preferably no more than a few seconds, e.g. between about 300 milliseconds to 1 second, so that the end user does not experience a noticeable delay in connecting the call. 
     Thereafter, the processor of mobile station  102  causes the voice call to be established and maintained for the end user of mobile station  102  (step  310  of  FIGS. 3-4 ). During the voice call, a traffic channel is maintained between mobile station  102  and wireless network  154  so that voice communications may take place between the end user of mobile station  102  and terminating call party  150 . Terminating call party  150  is associated with a telephone number which may have been selected by the end user of mobile station  102 . Terminating call party  150  may be any ordinary call party (e.g. family, friend, or colleague of the end user) or, alternatively, an emergency call center associated with “911” or other emergency telephone number such as a Public Safety Answering Point (or PSAP). Note that the GPS fix of step  308  occurs prior to the actual setup of the traffic channel and voice communications of the voice call in step  310 . 
     Sometime during the voice call, the processor of mobile station  102  causes pilot phase measurements (PPMs) to be obtained from base station signals of wireless network  104  (step  312  of  FIGS. 3-4 ). Unlike the PPMs that may be performed at step  302 , PPMs obtained at step  312  are not for purpose of providing the coarse location of mobile station  102 , but rather for use in combination with pseudoranges to enhance location accuracy when the available GPS pseudoranges alone are not sufficient for determining the location accurately. Performing PPMs at steps  312  (as well as sending PPMs in step  314  described below) may be optional in this technique. 
     Next, the processor of mobile station  102  causes the PPMs, GPS measurement data, and a request for location determination to be sent to location server or PDE  190  (step  314  of  FIGS. 3-4 ). The sending of the GPS measurement data may be performed in response to a request from location server  190  or other requesting entity, or autonomously by the mobile station  102  (e.g. triggered by the dialed phone number such as an emergency number like “911”). Next, location server/PDE  190  computes the location of mobile station  102  based on a triangulation/trilateration technique using the GPS pseudorange data and/or PPM data (step  316  of  FIGS. 3-4 ). The location information of the mobile station may be or include latitude, longitude, and altitude information. Location server  190  may send the resulting location information of mobile station  102  directly to terminating call party  150  with or without its request. Alternatively, location server  190  may send the location information to mobile station  102 , which may send in turn to terminating call party  190 . The flowchart of  FIG. 3  ends at a finish block  318 . 
     As apparent from the method of  FIGS. 3-4 , mobile station  102  is operative to refrain from causing the GPS fix to be performed during voice communications of a voice call so that communications are not disrupted. When a mobile station has to tune away from the voice call to perform the GPS fix in accordance with the conventional procedure, voice communications of the voice call are disrupted. In addition, the conventional procedure increases the chance that the voice call will be undesirably dropped. The conventional process also causes power control variations that can reduce system capacity. In the case where the voice call is very important, such as a 911 emergency call, these issues are of great concern. 
     In one variation associated with the method of  FIGS. 3-4 , the GPS procedure in steps  306 ,  308 ,  312 ,  314 , and  316 , or steps  312 ,  314 , and  316 , are performed only for predetermined telephone numbers and/or upon predetermined actions taken at the user interface by the end user. For example, the GPS procedure may be performed only for emergency calls (e.g. a 911 telephone number) but no others. If steps  306  and  308  are performed, and when the phone number is not intended for location determination, the obtained and stored GPS pseudorange measurement data is discarded. As another example, the GPS procedure may be performed only for those telephone numbers of a prestored list in memory of the mobile station but not for all other telephone numbers. The prestored list may be configurable by the end user and/or dealer, and may or may not include a 911 emergency telephone number. If this approach is taken, the processor of the mobile station compares the selected telephone number with the one or more telephone numbers in the prestored list to make its determination. In yet another variation, the visual display of the mobile station may display a prompt “SEND LOCATION INFORMATION?” for the end user to respond “YES” or “NO”. If the end user selects YES, the location information is sent; if the end user selects NO, the location information is not sent. Note that, if the location information is displayed in the visual display, the end user may orally communicate this displayed location information during the voice call to any terminating call party (e.g. an emergency dispatch officer such as a Public Safety Answering Point or PSAP operator). 
     A related method of the present application is based on a triggering signal where the end user takes action to terminate the voice call. This related method may be performed subsequent to, or as an alternative to, the method described in relation to  FIGS. 3-4 . The related method will now be described in relation to a flowchart of  FIG. 5  and a system flow diagram of  FIG. 6 . Beginning at a start block of  FIG. 5 , a voice call is established and maintained between mobile station  102  and terminating call party  150  (step  502  of  FIGS. 5-6 ). Terminating call party  150  is associated with a telephone number which may have been selected by the end user of mobile station  102 . Terminating call party  150  may be any ordinary call party (e.g. family, friend, or colleague) or, alternatively, an emergency call center associated with “911” or other emergency telephone number. When the voice call is established, a traffic channel is setup between the mobile station and the network. 
     The voice call is maintained for voice communications until the processor of mobile station  102  detects a request to terminate the call (step  504  of  FIGS. 5-6 ). The request to terminate the voice call may be made by the end user of mobile station  102  through the user interface, for example. In response to the request to terminate the call, the processor of mobile station  102  immediately causes a GPS procedure to be performed. In particular, the processor of mobile station  102  causes pilot phase measurements (PPMs) to be obtained from wireless network  104  (step  506  of  FIGS. 5-6 ). PPMs provide an indication of the coarse location of mobile station  102  which may be optional for this technique; other data such as broadcasted serving base station location data may be utilized as an alternative if needed. Next, the processor of mobile station  102  causes the PPMs (or the coarse location information of mobile station  102 ) and a request for GPS assistance data to be sent to location server  190  (step  508  of  FIGS. 5-6 ). In response, mobile station  102  receives GPS acquisition assistance data from location server  190  through the wireless network (step  510  of  FIGS. 5-6 ). GPS acquisition assistance data includes data that identifies the appropriate surrounding GPS satellites (e.g. in the form of PseudoRandom Noise or “PRN” code numbers), Doppler frequencies, and time delay window information. The GPS acquisition assistance data may be in the form of GPS ephemeris data and/or GPS almanac data. 
     Next, the processor of mobile station  102  causes a GPS fix to be performed with GPS signals from GPS system  154  and also perform PPM (step  512  of  FIGS. 5-6 ). Note that although the voice call is still maintained, voice communications between the parties have ended. During the GPS fix, the wireless receiver of mobile station  102  is tuned to a GPS system frequency to receive signals from GPS system  154 . The GPS measurement data may be or include GPS pseudorange data. The time it takes to perform the GPS fix with the wireless receiver may vary between about 300 milliseconds to 2 seconds. The processor of mobile station  102  may then optionally request sensitivity assistance data and reperform the GPS fix with use of the sensitivity assistance data, if needed. 
     The processor of mobile station  102  then causes the received GPS measurement data, additional PPMs, and a request for location computation to be sent to location server  190  having the PDE (step  514  of  FIGS. 5-6 ). The sending of the GPS measurement data may be performed in response to a request from location server  190  or other requesting entity. Next, location server/PDE  190  computes the location associated with mobile station  102  based on a triangulation/trilateration technique using the GPS measurement data and/or the PPM data (step  516  of  FIGS. 5-6 ). The location information of mobile station  102  may be or include latitude, longitude, and altitude information. Location server  190  may send the location information of mobile station  102  directly to terminating call party  150  with or without its request. Alternatively, location server  190  may send the location information to mobile station  102  which receives it for communication to terminating call party  190  with or without its request. Once the location information has been computed, the processor of mobile station  102  causes the voice call to be terminated (step  518  of  FIGS. 5-6 ). The flowchart of  FIG. 5  ends at a finish block  520 . 
     As apparent from the method of  FIGS. 5-6 , mobile station  102  is operative to refrain from causing the GPS fix to be performed during voice communications of a voice call so that voice communications are not disrupted. When a mobile station has to tune away from the voice call to perform the GPS fix in accordance with the conventional procedure, voice communications of the voice call are disrupted. In addition, the conventional procedure increases the chance that the voice call will be undesirably dropped. The conventional process also causes power control variations that can reduce system capacity. In the case where the voice call is very important, such as a 911 emergency call, these issues are of great concern. 
     In one variation associated with the method of  FIGS. 5-6 , the GPS procedure in steps  506 - 518  is performed only for predetermined telephone numbers and/or upon predetermined actions taken at the user interface by the end user. For example, the GPS procedure may be performed only for emergency calls (e.g. a 911 telephone number) but no others. As another example, the GPS procedure may be performed only for those telephone numbers of a prestored list in memory of the mobile station but not for all other telephone numbers. The prestored list may be configurable by the end user and/or dealer, and may or may not include a 911 emergency telephone number. If this approach is taken, the processor of the mobile station compares the selected telephone number with the one or more telephone numbers in the prestored list to make its determination. In yet another variation, the visual display of the mobile station may display a prompt “SEND LOCATION INFORMATION?” for the end user to respond “YES” or “NO”. If the end user selects YES, the location determination procedures are performed; if the end user selects NO, the location determination procedures are not performed. 
     In an alternative embodiment, all steps in  FIGS. 3-6  involving PPMs are not utilized. In another alternative embodiment, steps  314  and  316  in  FIGS. 3-4  and steps  514  and  516  in  FIGS. 5-6  are not performed, but rather mobile station  102  computes the location of the mobile station based on GPS measurement data and/or PPM data. In yet another embodiment, location server/PDE  190  is not utilized; rather, mobile station  102  directly decodes GPS navigational-type data from signals of GPS system  154  periodically or regularly in the idle mode at step  302  of  FIGS. 3-4 , performs stand-alone GPS pseudorange measurement at step  308  of  FIGS. 3-4 , and computes its own location based on the GPS pseudorange measurement data at step  316 ; steps  312  and  314  of  FIGS. 3-4  are not performed. 
     The description above used a CDMA wireless network as an example, which has the advantage that the mobile station gets accurate GPS time easily from the wireless network. However, the method and system can also be used in connection with other suitable wireless networks. 
     Final Comments. Methods and apparatus for facilitating the determination of GPS location information for a mobile station without disrupting communications of a voice call (e.g. a 911 emergency call) have been described. In one illustrative example, the mobile station causes GPS navigational-type data to be received through a wireless receiver and stored in memory prior to voice communications of a voice call involving the mobile station. The mobile station then receives, through a user interface, a voice call request for the voice call through a wireless communication network. After receiving the voice call request, the mobile station derives GPS assistance data based on the stored GPS navigational-type data. The mobile station then causes, with use of the wireless receiver, a GPS fix to be performed with signals from a GPS system using the derived GPS assistance data. The mobile station obtains GPS measurement data based on signals from the GPS system. Thereafter, the mobile station causes the voice call to be established and maintained for the mobile station through the wireless communication network. The GPS measurement data is then transmitted from the mobile station to a location server in the wireless communication network for calculating the location of the mobile station. As apparent, the mobile station is operative to refrain from causing the GPS fix to be performed during the voice communications of the voice call so that the communications are not disrupted. 
     In another illustrative example, the mobile station again maintains a voice call (e.g. a 911 emergency call) through a wireless communication network. At some point in time, the mobile station identifies a trigger signal indicative of a request to terminate the voice call. In response to identifying the trigger signal, the mobile station causes a GPS fix to be performed, with use of a wireless receiver, with the GPS system using GPS assistance data. The mobile station obtains GPS measurement data based on signals from the GPS system. The GPS measurement data is then transmitted from the mobile station to a location server in the wireless communication network for calculating the location of the mobile station. The location server may send the location information to a recipient device or, alternatively, the location server may send the location information to the mobile station which then sends it to the recipient device. The mobile station then causes the voice call to be terminated. Using this method, the mobile station is again operative to refrain from causing the GPS fix to be performed during the voice communications of the voice call so that the communications are not disrupted. 
     The above-described embodiments of the present application are intended to be examples only. Those of skill in the art may effect alterations, modifications and variations to the particular embodiments without departing from the scope of the application. Note that the location information may be included and sent in any suitable message, such as a TeleType (TTY) message. Apart from GPS, for course, other satellite-based systems may exist and be used according to the present application, such as Global Navigation Satellite System (GLONASS), etc. The invention described herein in the recited claims intends to cover and embrace all such changes in technology.