Background ephemeris download in navigational receivers
First Claim
1. A method of maintaining current ephemeris in a navigation receiver, comprising:
- alternating between a sleep mode and a wake up mode;
testing a received signal strength when the receiver wakes up from the sleep mode;
if the tested signal strength is sufficient to download ephemeris, downloading current ephemeris if a last downloaded ephemeris is no longer current; and
if the tested signal strength is too weak to download ephemeris, placing the receiver back in sleep mode.
4 Assignments
0 Petitions
Accused Products
Abstract
The present invention provides methods and systems for keeping the ephemeris in a navigational receiver current to achieve fast TTFF without the need for connecting to an aiding network or remote server. In an embodiment, the receiver keeps the ephemeris current by downloading the ephemeris in the background. In the preferred embodiment, the receiver uses a background sleep/wake up process to download current ephemeris with minimal power drain. In this embodiment, the receiver alternates between a sleep mode and a wake up mode. During the wake up mode, the receiver attempts to download current ephemeris. The receiver then goes back to the sleep mode until the next wake up to conserve power. The receiver may wake up from the sleep mode to download the ephemeris when the stored ephemeris is no longer current or the ephemeris broadcasted from a satellite has been updated or based on receiver usage patterns.
-
Citations
39 Claims
-
1. A method of maintaining current ephemeris in a navigation receiver, comprising:
-
alternating between a sleep mode and a wake up mode; testing a received signal strength when the receiver wakes up from the sleep mode; if the tested signal strength is sufficient to download ephemeris, downloading current ephemeris if a last downloaded ephemeris is no longer current; and if the tested signal strength is too weak to download ephemeris, placing the receiver back in sleep mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 38, 39)
-
-
16. A method of maintaining current ephemeris in a navigation receiver, comprising:
-
alternating between a sleep mode and a wake up mode; and downloading current ephemeris if a last downloaded ephemeris is no longer current; wherein when a user initiates a fast start of the receiver, further comprising; if the ephemeris of acquired satellites are current, using the ephemeris for a position fix; and if not all of the ephemeris of the acquired satellites are current, determining the position and subsequent receiver trajectory by computing the position and subsequent trajectory using the ephemeris and correcting the computed position and subsequent trajectory. - View Dependent Claims (17)
-
-
19. A navigation signal receiver, comprising:
-
a radio frequency (RF) front-end for receiving satellite signals; a baseband section for processing received signals into correlation values; a processor coupled to the baseband section, wherein the processor downloads current ephemeris if a last downloaded ephemeris is no longer current; a signal strength detector for testing a received signal strength from the RF front-end; and a sleep/wake up module coupled to a power system of the receiver, wherein the sleep/wake up module alternately switches the receiver between a sleep mode and a wake up mode; wherein the signal strength tests the received signal strength when the receiver wakes up from the sleep mode, and if the tested signal strength is sufficient to download ephemeris, the sleep/wake up module powers up the baseband section and the processor to download the current ephemeris from a navigation satellite if the last downloaded ephemeris is no longer current. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 36)
-
-
34. A navigation signal receiver, comprising:
-
a radio freiuency (RF) front-end for receiving satellite signals; a baseband section for processing received signals into correlation values; a processor coupled to the baseband section, wherein the processor downloads ephemeris if a last ephemeris is no longer current; and a sleep/wake up module coupled to a power system of the receiver, wherein the sleep/wake up module alternately switches the receiver between a sleep mode and a wake up mode; wherein when a user initiates a fast start of the receiver, the processor uses ephemeris to compute a position fix if the ephemeris of acquired satellites are current, and determines the position and subsequent receiver trajectory by computing the position and subsequent trajectory using the ephemeris and correcting the computed position and subsequent trajectory if not all of the acquired ephemeris are current. - View Dependent Claims (35)
-
-
37. The receiver of 19, wherein the processor stores the downloaded ephemeris to predict the satellite orbit and using the predicted satellite orbit to compute satellite position when current ephemeris can not be downloaded.
Specification