Method and system for selecting optimal satellites in view

A system for determining a set of satellites in view of a wireless device comprising:

• (a) circuitry for receiving a request for satellite assistance data from a requesting entity;
• (b) circuitry for determining a reference location as a function of the request;
• (c) circuitry for determining a set of satellites as a function of the reference location;
• (d) circuitry for caching initial information for each satellite in the set of satellites;
• (e) circuitry for determining and caching subsequent cached information for each satellite in the set of satellites when the cached initial information has been cached for greater than a predetermined time period, the time period determined as a function of elevation of a respective satellite;
• and
• (f) circuitry for determining one or more satellites in view of the wireless device as a function of either the subsequent cached information or initial cached information.

A method for determining one or more satellites in view of a wireless device comprising:

• (a) receiving a request for satellite assistance data from a requesting entity;
• (b) determining a reference location as a function of the request;
• (c) determining a first set of satellites in view as a function of the reference location when there is information available from a first cached set of satellites, the first cached set of satellites being cached for less than a predetermined time period, the time period determined as a function of elevation of a respective satellite;
• and
• (d) determining a second set of satellites in view as a function of the reference location when the first cached set of satellites has been cached for greater than the predetermined time period and determining additional cached information for each satellite in the second set of satellites as a function of the reference location.

A method for determining an estimated location of a wireless device comprising:

• (a) receiving a request for satellite assistance data from a wireless device;
• (b) determining a reference location of the wireless device;
• (c) determining a set of satellites as a function of the reference location;
• (d) determining subsequent cached information for one or more satellites in the set of satellites when previously cached information for the one or more satellites in the set of satellites has been cached for greater than a predetermined time period, the time period determined as a function of elevation of a respective satellite;
• (e) determining one or more satellites in view of the wireless device as a function of either the subsequent cached information or previously cached information;
• (f) transmitting assistance data to the wireless device, the assistance data including information from the one or more satellites in view;
• and
• (g) determining an estimated location of the wireless device from the included information.