Abstract:
A mobile terminal stores almanac information relating to the position of satellites within a position detection system by converting selective portions of ephemeris information to almanac information. The ephemeris information may be provided by a mobile network continuously or on demand from the mobile terminal. Alternatively, the mobile terminal may secure the ephemeris information from satellites.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a position detection system integrated with a mobile terminal and a method to shorten time required to secure an accurate estimation of position. 
     Mobile terminals such as cellular phones, personal digital assistants, automobiles with GPS equipment, laptops equipped with wireless modems, and the like have exploded into the public consciousness. These devices enable individuals to remain connected to other people without being tied to a land-based phone. 
     Because mobile terminals are in fact, by definition, mobile, many recent patents have discussed incorporating position detection capabilities into the mobile terminals so that the user of the mobile terminal may know where they are. Alternatively, such technology may be used so that a third party knows where the mobile terminal is located. One such proposed use of a position detection system is to deter theft; items being protected may periodically report their present whereabouts through a wireless modem as determined by the position detection system. 
     One popular position detection system targeted for such incorporation into a mobile terminal is the Global Position System (GPS), which relies on a constellation of satellites to assist a GPS receiver in determining its location. Other satellite-based systems do exist, such as GLONASS, the Russian equivalent of GPS. 
     Unfortunately, while integration of position detection systems and mobile terminals seems like a laudable goal and is technically feasible, such integration may tend to ignore the realities behind such position detection systems and mobile networks. For example, GPS has an extremely slow data transfer rate. It takes on the order of ten to twenty minutes to secure all known data from the satellites. While GPS may be an extreme example, other positioning systems may experience similar delays. Inability to secure quick position information may lead to consumer frustration. In a theft deterrent usage, the long lag in determining a position of a stolen item may hinder recovery efforts. Furthermore, such a slow transfer rate means that the mobile terminal must be active for that entire time, creating a drain on its battery. 
     Several solutions to this problem have been proposed, although presently without any significant commercial exploitation. In one solution, the mobile terminal gets some or all information from the mobile network. One aspect of this solution requires that the mobile terminal inquire over the mobile network to a server about the precise present location (“ephemeris”) of the satellites. A problem arises for this solution when the mobile network may be unable to supply this information. This may occur, for instance, when users roam into new areas and the local service provider is not capable of providing the required assistance. In a second aspect of this solution, the mobile network continuously provides almanac information over a control channel. This creates a bandwidth drain for sporadically used information and is inefficient. 
     As a fallback position, the mobile terminal may still receive the information from the satellites themselves, but this, as previously noted is an extremely slow and battery intensive process. Additionally, the mobile terminal may never have been in an active state long enough to download the almanac information from the satellites. This may be because the user is selective about powering on the mobile terminal or because the mobile terminal has previously been able to acquire the almanac information from the service provider and has never had to access the satellites for almanac information. 
     Still another solution is to hardcode the almanac information into the mobile terminal. However, this information may become dated after a few months and no longer serve its intended purpose as satellite orbits may vary with time. Since the information is hardcoded, the mobile terminal would require a new circuit board or software update to access new information. 
     Thus, there remains a need for a mobile terminal that can selectively store almanac information for later use without requiring the power drain associated with downloading the information from the satellites and without wasting bandwidth on the control channels of the service providers. 
     SUMMARY OF THE INVENTION 
     The present invention uses ephemeris information to compute satellite positions for faster acquisition at a later time. In one embodiment, the present invention creates an almanac in the memory of the mobile terminal by converting ephemeris information into almanac information. The conversion may comprise merely scaling the ephemeris information and perhaps losing a few bits of information. The ephemeris information may be received from either the satellites or the mobile network. The ephemeris information may be received from the mobile network by the mobile terminal by one of a number of different techniques. The mobile terminal may periodically request the ephemeris information. The mobile network may continuously or periodically broadcast the ephemeris information at a low rate, thereby conserving bandwidth. Other techniques are also contemplated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a schematic drawing of a communication system suitable for use with the present invention; 
     FIG. 2 illustrates a schematic drawing of a mobile terminal for use in the communication system of FIG. 1; 
     FIG. 3 illustrates a schematic drawing of a communication system wedded to a first position detection system; 
     FIG. 4 illustrates a first embodiment of the methodology of the present invention as a flow chart; 
     FIG. 5 illustrates a second embodiment of the methodology of the present invention as a flow chart; and 
     FIG. 6 illustrates a third embodiment of the methodology of the present invention as a flow chart. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is directed to an improvement of a mobile terminal coupled with a position detection system. An understanding of an entire communications system and mobile terminal may be helpful for a proper understanding of the context of the present invention. While the following discussion is couched in terms of a TIA/EIA-136 communication system, it should be appreciated that the present invention is equally applicable to Digital Advance Mobile Phone Service (D-AMPS), European Total Access Communication System (ETACS), Global System for Mobile Communication (GSM), Pacific Digital Cellular (PDC), and the like, the standards and documentation of which are herein incorporated by reference. 
     Turning now to FIG. 1, a communication system  10  is illustrated. In particular, the communications system  10  includes the Public Switched Telephone Network (PSTN)  20  and the Public Land Mobile Network (PLMN)  30 , which may, in turn, be connected to one or more Localized Wireless Telephone Systems (LWTS, only one shown)  60 . LWTS  60  may be proprietary or public as needed or desired. While not shown, satellites may be used as needed either within the PSTN  20  or the PLMN  30  to provide remote communication links, such as across oceans or the like. 
     The operation of the PSTN  20  is well established and subject to extensive documentation beyond the scope of the present invention and therefore a more detailed discussion is omitted. 
     PLMN  30  may include a plurality of proprietary mobile networks  40 , such as those operated by AT&amp;T and BELLSOUTH MOBILITY, also known as service providers. Each mobile network  40  may include a plurality of Mobile Switching Centers (MSCs)  42 . Note that in a TIA/EIA-136 system, MSC stands for Mobile Switching Center. Equivalently, in a GSM system, MSC stands for a Mobile Services Switching Center. The acronym and the functions remain identical, however, the term for which the acronym stands is slightly different. Other systems may have yet other names, however, the function of the MSC as herein described is intended to be embraced. At least one MSC  42  in the PLMN  30 , and more likely one MSC  42  in each mobile network  40  is connected via a gateway to the PSTN  20 . Some MSCs  42  may also serve as gateways connecting the various mobile networks  40  within the PLMN  30 . Gateway functions may be all consolidated at a single MSC  42  within a mobile network  40  or dispersed amongst a plurality of MSCs  42  within a mobile network  40  as needed or desired. At least one MSC  42  within a particular mobile network  40  may be communicatively connected to a Home Location Register (HLR)  44  and a Visitor Location Register (VLR)  46 . Additionally, each mobile network  40  may be equipped with a message center  48  communicatively connected to an MSC  42 . Each MSC  42  may further be communicatively connected to a plurality of base stations  50 . An MSC  42  responsible for a LWTS  60  may treat the LWTS  60  as another base station  50  or a plurality of base stations  50  depending on the internal structure of the LWTS  60  in question. Each base station  50  may be communicatively connected to one or more mobile terminals  100 , typically over an RF communications channel. 
     The function of the MSCs  42  is to route calls and signals in the mobile network  40  to the appropriate destination. To perform this function, a mobile network  40  relies on the HLR  44  and the VLR  46 . HLR  44  is used to store information concerning subscribers to a mobile network  40 , e.g., AT&amp;T&#39;s subscribers. This information typically includes the subscriber&#39;s name and address for billing purposes, the serial number of the subscriber&#39;s mobile terminal  100 , and the services that the subscriber is entitled to receive. In addition, the current coarse location of the subscriber, as evidenced by the current location of their mobile terminal  100 , is stored in the HLR  44 . Note that in this context the current coarse location is a very rough location determination, as in, “the mobile terminal is somewhere within this cell,” which are typically anywhere from 300 m to 35 km in diameter. 
     The coarse current location of the subscriber is secured when the mobile terminal  100  is powered on and at periodic intervals thereafter. In particular, the mobile terminal  100  registers through the nearest base station  50  with an MSC  42 . This is referred to herein as the “servicing MSC.” The servicing MSC  42  then sends information to the HLR  44  indicating in which cell of the mobile network  40  the mobile terminal  100  may be found. This assumes that the subscriber is in his home network—i.e., the one in which he has a service contract. 
     Mobile terminal  100  also registers through the nearest base station  50  and hence with an MSC  42  when it travels between two different service areas (areas served by different MSCs  42 ). As part of this registration procedure, the mobile terminal  100  transmits its Mobile Identification Number (MIN) to the closest base station  50 , which in turn passes the information to the appropriate MSC  42 . MSC  42  uses the MIN to determine which HLR  44  to access. When the mobile terminal  100  registers with the new MSC  42 , the new servicing MSC  42  updates the HLR  44  with the current coarse location of the mobile terminal  100 . When an MSC  42  receives a call addressed to a subscriber that is not currently in that MSC&#39;s service area, the MSC  42  will query the HLR  44  for the subscriber&#39;s current coarse location so that the call can be forwarded to the MSC  42  currently servicing the subscriber. 
     VLR  46  is used to store information about subscribers of mobile terminals  100  that are not in their home network. When subscribers roam outside of their home network, the VLR  46  in the network being visited must keep track of the subscriber&#39;s location and be able to verify the Mobile Identification Number (MIN) of the mobile terminal  100 . The VLR  46  in the network being visited queries the HLR  44  in the subscriber&#39;s home service area to authenticate the subscriber and determine the services to which the subscriber is entitled. Information concerning the subscriber is stored in the VLR  46  as long as the subscriber remains registered in the visited network. VLR  46  also stores the current coarse location of the subscriber. The subscriber&#39;s current coarse location is communicated back to the home network HLR  44  so that the home mobile network  40  will know where to forward a call addressed to the subscriber who is currently outside the home mobile network  40 . 
     Together, the HLR  44  and the VLR  46  provide the information needed by the MSCs  42  to route calls to the appropriate destination. The routing may further be accomplished by handing the call to another mobile network  40 , locating the appropriate base station  50 , or passing the call to the PSTN  20  as is appropriate. The exact protocols and communication regimens between the various entities in a mobile network  40  are well documented, such as in TIA/EIA-136, GSM, D-AMPS, ETACS, PDC, or the like, previously incorporated by reference. 
     Many mobile networks  40  implement a service called short message service (SMS). This service allows subscribers to send and receive short text messages. Messages originating from, or terminating at, a mobile terminal  100  in the network  40  are stored in the message center  48  connected to an MSC  42 . Message centers  48  are well understood in the art and a further discussion is omitted. 
     LWTS  60  may be public or proprietary as needed or desired, and is typically a private network installed in a building or on a campus. LWTS  60  allows employees or other persons working in the building or on the campus to use a mobile terminal  100  as an office telephone. LWTS  60  connects with an MSC  42  in the PLMN  30 . Thus, subscribers of the LWTS  60  may move seamlessly between the PLMN  30  and the LWTS  60 . LWTS  60  may include a control and radio interface (not shown) and a plurality of transceiver stations. 
     Turning now to FIG. 2, a mobile terminal  100  typically includes a controller  122 , an operator interface  126 , a transmitter  138 , a receiver  150 , and an antenna assembly  158 . Operator interface  126  typically includes a display  128 , keypad  130 , interface control  132 , microphone  134 , and a speaker  136 . Display  128  allows the operator to see dialed digits, call status, and other service information. Keypad  130  allows the operator to dial numbers, enter commands, and select options. Interface control  132  interfaces the display  128  and keypad  130  with the controller  122 . Microphone  134  receives acoustic signals from the user and converts the acoustic signals to an analog electrical signal. Speaker  136  converts analog electrical signals from the receiver  150  to acoustic signals that can be heard by the user. 
     The analog electrical signal from the microphone  134  is supplied to the transmitter  138 . Transmitter  138  includes an analog to digital converter  140 , a digital signal processor  142 , and a phase modulator and RF amplifier  148 . Analog to digital converter  140  changes the analog electrical signal from the microphone  134  into a digital signal. The digital signal is passed to the digital signal processor (DSP)  142 , which contains a speech coder  144  and channel coder  146 . Speech coder  144  compresses the digital signal and the channel coder  146  inserts error detection, error correction and signaling information. DSP  142  may include, or may work in conjunction with, a DTMF tone generator (not shown). The compressed and encoded signal from the digital signal processor  142  is passed to the phase modulator and RF amplifier  148 , which are shown as a combined unit in FIG.  2 . The modulator converts the signal to a form that is suitable for transmission on an RF carrier. RF amplifier  148  then boosts the output of the modulator for transmission via the antenna assembly  158 . 
     Receiver  150  includes a receiver/amplifier  152 , digital signal processor  154 , and a digital to analog converter  156 . Signals received by the antenna assembly  158  are passed to the receiver/amplifier  152 , which shifts the frequency spectrum, and boosts the low-level RF signal to a level appropriate for input to the digital signal processor  154 . 
     Digital signal processor  154  typically includes an equalizer to compensate for phase and amplitude distortions in the channel corrupted signal, a demodulator for extracting bit sequences from the received signal, and a detector for determining transmitted bits based on the extracted sequences. A channel decoder detects and corrects channel errors in the received signal. The channel decoder also includes logic for separating control and signaling data from speech data. Control and signaling data are passed to the controller  122 . Speech data is processed by a speech decoder and passed to the digital to analog converter  156 . Digital signal processor  154 , may include, or may work in conjunction with, a DTMF tone detector (not shown). Digital to analog converter  156  converts the speech data into an analog signal that is applied to the speaker  136  to generate acoustic signals that can be heard by the user. 
     Antenna assembly  158  is connected to the RF amplifier of the transmitter  138  and to the receiver/amplifier  152  of the receiver  150 . Antenna assembly  158  typically includes a duplexer  160  and an antenna  162 . Duplexer  160  permits full duplex communications over the antenna  162 . 
     Controller  122  coordinates the operation of the transmitter  138  and the receiver  150 , and may for instance take the form of a typical microprocessor. This microprocessor may be a dedicated or shared microprocessor and may be a single processor or multiple parallel processors as needed or desired. This coordination includes power control, channel selection, timing, as well as a host of other functions known in the art. Controller  122  inserts signaling messages into the transmitted signals and extracts signaling messages from the received signals. Controller  122  responds to any base station commands contained in the signaling messages, and implements those commands. When the user enters commands via the keypad  130 , the commands are transferred to the controller  122  for action. Memory  124  stores and supplies information at the direction of the controller  122  and preferably includes both volatile and non-volatile portions. In particular, memory  124  may be conventional RAM, low power battery backed RAM, or non-volatile storage such as Flash EPROM, disk file, EEPROM, and the like. 
     In addition to the above-described elements, the mobile terminal  100  may also include a location detector  164  in communication with the controller  122 . Location detector  164  may have its own antenna (not shown) or may share antenna  162 . Location detector  164  maybe Global Positioning System (GPS) receiver, a GLONASS receiver, or other satellite system as needed or desired. Typically, the location detector  164  will output a geocoordinate expressed as longitude and latitude coordinates corresponding to the present location of the mobile terminal  100 . In contrast to the coarse location determination made by the mobile network  40 , a geocoordinate may, with present civilian systems, be accurate to within approximately 25 meters. 
     It should be appreciated that the term “mobile terminal” may include a cellular radiotelephone with or without a multi-line display; a Personal Communications System (PCS) terminal that may combine a cellular radiotelephone with data processing, facsimile and data communications capabilities; a PDA that can include a radiotelephone, pager, Internet/intranet access, Web browser, organizer, calendar and/or a global positioning system (GPS) receiver; and a conventional laptop and/or palmtop receiver or other appliance that includes a radiotelephone transceiver. Mobile terminals may also be referred to as “pervasive computing” devices. Thus, while the present discussion may be couched in terms of a phone, the present invention is equally applicable to these other sorts of devices. The previous discussion was by way of example, and not intended to be limiting on the definition of a mobile terminal. 
     With that discussion of mobile networks  40  and mobile terminals  100 , it is now possible to discuss using a mobile terminal  100  with a position detection system  200 . In particular, a satellite based position detection system  200 , such as GPS or GLONASS, is illustrated in FIG.  3 . Satellite based position detection system  200  employs a constellation of satellites  201  (only one shown) that orbit the earth in known trajectories. Applications  210  may be run at a number of positions that require location information from the position detection system  200 . 
     In a first embodiment, an application  210  may run on the mobile terminal  100 . An example of such an application would be a simple location program that tells the user of the mobile terminal  100  where the mobile terminal  100  is located. In a second embodiment, an MSC  42  (FIG. 1) within the mobile network  40  may have an application  210  running thereon that solicits information about the whereabouts of a particular mobile terminal  100 . This may be for emergency purposes, billing purposes, or some other reason. In a third embodiment, a server  202  external to the mobile network  40  may have an application  210  that inquires as to the whereabouts of a particular mobile terminal  100 . Examples of such usages include delivery services inquiring where their drivers are located as evidenced by the location of the drivers&#39; mobile terminals  100 . Server  202  interfaces with the mobile network  40  through conventional means and instructs the mobile terminal  100  to report its present location. Note that server  202  may also be in communication with the position detection system  200  and be adapted to receive almanac and ephemeris information therefrom routinely. 
     Regardless of the reason that application  210  wishes to know the location of the mobile terminal  100 , the fact remains that an application  210  may make an inquiry as to the location of the mobile terminal  100 . In the prior art, the mobile terminal  100  would have to either download from the satellite  201  almanac and/or ephemeris information. This may take approximately twelve and a half minutes or more. Alternatively in the prior art, the mobile terminal  100  would inquire over the mobile network  40  and retrieve almanac and/or ephemeris information from the mobile network  40  or the server  202 . This information would then be broadcast over the mobile network  40 , consuming bandwidth and making the jobs of network administrators more difficult. For example, such ephemeris information may be broadcast on the BATS channel in a TIA/EIA-136 based mobile network  40  and over the SDCCH in a GSM based mobile network  40 . It should be appreciated that mobile network  40  and server  202  as fixed installations may continually monitor the ephemeris information, and should always have readily available ephemeris information for downloading to the mobile terminal  100  through the base station  50 . 
     A problem may arise if the mobile terminal  100  is operating in conjunction with a mobile network  40  that does not have the ability to transmit the position detection system related information to the mobile terminal  100 . For instance, such a situation may arise when a mobile terminal  100  is outside of its home service area and instead borrowing from a neighboring mobile network  40  that has yet to upgrade its facilities so as to provide the requested information. Alternatively, the mobile terminal  100  may temporarily be out of service with respect to the mobile network  40 , yet still have a request to locate itself, such as from an application  210  internal to the mobile terminal  100 . In such situations, the mobile terminal  100  may be unable to locate itself quickly due to the lack of adequate almanac information. 
     The present invention addresses this situation by converting ephemeris information into almanac information when the ephemeris information is available, and storing the almanac information in memory  124 . The stored almanac information is then available for use in determining the position of the mobile terminal  100  at a later time. For instance, the mobile terminal  100  may receive the ephemeris information while communicating with an updated mobile network  40 , convert the ephemeris information to almanac information, store the almanac information, and then travel to an older mobile network  40  that has not yet been updated to provide ephemeris information. Mobile terminal  100  may then use the stored almanac information to help determine its position. 
     For the present invention to function properly, the mobile terminal  100  must be supplied with ephemeris information at some point. This may be done in a number of different ways. In a first embodiment, illustrated in FIG. 4, the mobile terminal  100  powers on (block  300 ) at some point. Initially, the mobile terminal  100  camps on a control channel (block  302 ) as is well understood. Mobile network  40  may periodically broadcast ephemeris information (block  304 ). It may be desirable to broadcast this information at a very low data rate, perhaps one bit per frame or superframe to preserve bandwidth for control information. However, it is not required that this low data rate be used. 
     Regardless of the rate at which the ephemeris information is broadcast by the mobile network  40 , the mobile terminal  100  receives the ephemeris information (block  306 ). After the mobile terminal  100  then converts the ephemeris information to almanac on (block  308 ). This is possible because of the nature and interrelationship of the almanac and ephemeris information. The almanac information is simply a reduced-precision subset of the clock and ephemeris parameters. Thus, with the appropriate mathematical transformations, ephemeris information may easily be converted to almanac information. Navstar document ICD-GPS-200, Revision C, updated Oct. 11, 1999, which is hereby incorporated by reference in its entirety, on pp. 87 and 96 lists the ephemeris parameters. Later in the same document, on page 108, is a list of the almanac parameters. The majority of the transformations are simply scaling or masking, perhaps losing a few bits of information. A table of the equivalent parameters and the applicable transformations is presented below: 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Ephemeris 
                 Almanac 
                   
               
               
                   
                 Parameter 
                 Parameter 
                 Transformation 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                  1 
                 Code on L2 
                 N/A 
                 Discard 
               
               
                  2 
                 Week Number 
                 N/A 
                 Discard 
               
               
                  3 
                 L2 P data flag 
                 N/A 
                 Discard 
               
               
                  4 
                 SV accuracy 
                 N/A 
                 Discard 
               
               
                  5 
                 SV health 
                 N/A 
                 Discard 
               
               
                  6 
                 T GD   
                 N/A 
                 Discard 
               
               
                  7 
                 IODC 
                 N/A 
                 Discard 
               
               
                  8 
                 t oc   
                 t oa   
                 Scaling/Masking 
               
               
                  9 
                 a f2   
                 N/A 
                 Discard 
               
               
                 10 
                 a f1   
                 a f1   
                 Scaling/Masking 
               
               
                 11 
                 a f0   
                 a f0   
                 Scaling/Masking 
               
               
                 12 
                 IODE 
                 N/A 
                 Discard 
               
               
                 13 
                 C rs   
                 N/A 
                 Discard 
               
               
                 14 
                 Δn 
                 N/A 
                 Discard 
               
               
                 15 
                 M 0   
                 M 0   
                 Scaling/Masking 
               
               
                 16 
                 C uc   
                 N/A 
                 Discard 
               
               
                 17 
                 e 
                 E 
                 Scaling/Masking 
               
               
                 18 
                 C us   
                 N/A 
                 Discard 
               
               
                 19 
                 (A) 1/2   
                 (A) 1/2   
                 Scaling/Masking 
               
               
                 20 
                 t oe   
                 N/A 
                 Discard 
               
               
                 21 
                 C ic   
                 N/A 
                 Discard 
               
               
                 22 
                 (OMEGA) 0   
                 (OMEGA) 0   
                 Scaling/Masking 
               
               
                 23 
                 C is   
                 N/A 
                 Discard 
               
               
                 24 
                 i o   
                 δ i   
                 0.3 semi-circle offset 
               
               
                   
                   
                   
                 and Scaling/Masking 
               
               
                 25 
                 C rc   
                 N/A 
                 Discard 
               
               
                 26 
                 ω 
                 ω 
                 Scaling/Masking 
               
               
                 27 
                 OMEGADOT 
                 OMEGADOT 
                 Scaling/Masking 
               
               
                 28 
                 IDOT 
                 N/A 
                 Discard 
               
               
                   
               
             
          
         
       
     
     The transformations may be performed by the controller  122 . After transformation the mobile terminal stores the newly created almanac information in memory  124  (block  310 ). 
     An example of a scaling/masking transformation is as follows. OMEGADOT comprises 24 bits having a scale factor of 2 −43  as ephemeris information. OMEGADOT comprises 16 bits having a scale factor of 2 −38  as almanac information. Thus, the transformation would be to change the scale to the new scale factor and mask the extra bits of information. Similar transformations would be performed for the other parameters. 
     The second embodiment, illustrated in FIG. 5, is almost identical to the first embodiment; however, it will be explicitly recited for completeness. Mobile terminal  100  powers on (block  400 ) at some point. Mobile terminal  100  initiates a request for ephemeris information from the mobile network  40  or the server  202  (block  402 ). Mobile network  40  broadcasts ephemeris information (block  404 ). In this embodiment, where there is a specific request for the information it may be desirable to have the information delivered rapidly, rather than at the slow data rate suggested above. Regardless of the rate at which the ephemeris information is broadcast by the mobile network  40 , the mobile terminal  100  receives the ephemeris information (block  406 ). After reception, the mobile terminal  100  then converts the ephemeris information to almanac information (block  408 ). This is identical to block  308 . The transformations may be performed by the controller  122 . After transformation the mobile terminal stores the newly created almanac information in memory  124  (block  410 ). 
     It should be appreciated that for either of these embodiments, the mobile network  40  may provide only ephemeris information for those satellites  201  that are visible within the service area of the mobile network  40 . This may conserve the amount of information that needs to be sent to the mobile terminal  100 . Further, it should be appreciated that the mobile terminal  100  may initiate the request for ephemeris information based on a request from an application  210  and in this situation, the conversion may be done concurrent with, subsequent to, or prior to the position determination and reporting to application  210 . 
     In a third, non-preferred embodiment, illustrated in FIG. 6, the mobile terminal  100  receives the ephemeris information from the satellites  201 . Each satellite  201  broadcasts ephemeris information for its own orbit, but not those of other satellites  201 . Every satellite  201  broadcasts almanac information for every satellite  201  in the position detection system  200 . Rather than the twelve and a half minutes it takes to get almanac information, the broadcast of the ephemeris information from the satellites  201  only takes approximately thirty seconds. Thus, it is possible to get the ephemeris information from the satellites relatively quickly. However, this requires that the mobile terminal  100  have some idea of where to look for the satellites  201  so that it may listen to the ephemeris broadcasts. Further, the mobile terminal  100  must listen to multiple satellites  201  to acquire a sufficient set of ephemeris information from which to assemble an almanac. However, if the mobile terminal is powered on (block  500 ) and is active (as opposed to sleeping) for an extended period of time, it may locate one or more satellites  201  during such an extended active period (block  502 ). Mobile terminal  100  then receives ephemeris information from the one or more satellites  201  (block  504 ). Mobile terminal  100  then converts the ephemeris information into almanac information (block  506 ) and stores the almanac information in memory  124  (block  508 ) as previously described. 
     Regardless of how the mobile terminal  40  acquires the ephemeris information and converts it to almanac information, the almanac information is now available to the mobile terminal  100  in those situations where the mobile terminal  100  does not have access to mobile network assistance. For example, imagine a mobile terminal  100  that has service from a first mobile network  40  and has the ability to rely on that mobile network  40  to provide ephemeris and almanac information on demand, but the mobile terminal  100  travels to another mobile network  40 &#39;s service area and receives a request to determine its position. This mobile terminal  100  may not be able to rely on the new mobile network  40  to provide assistance, but by storing the almanac information in memory  124 , mobile terminal  100  does not have to be active for twelve and a half minutes to download the almanac information from the satellites  201 . This shortens the Time To First Fix (TTFF), conserving battery power for the mobile terminal  100 . 
     The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and the essential characteristics of the invention. The present embodiments are therefore to be construed in all aspects as illustrative and not restrictive and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.