Generating Accurate Time Assistance Data for An LTE Network
A system method for estimating Global Navigation Satellite System assistance data in a communications network. The method may comprise transmitting a location request from a mobility management entity to a location server, requesting a wireless device to transmit a first signal, and transmitting the first signal by the wireless device. A path delay estimate between the wireless device and location server may be determined as a function of an elapsed time for the request to the wireless to be received and as a function of an elapsed time for the transmitted first signal to be received. Satellite assistance data may then be determined as a function of current network time and the determined path delay estimate.
1 . A method for estimating Global Navigation Satellite System (“GNSS”) assistance data in a communications network, the method comprising:
(a) transmitting a location request from a mobility management entity (“MME”) to a location server;
(b) requesting a wireless device to transmit a first signal;
(c) transmitting the first signal by the wireless device;
(d) determining a path delay estimate between the wireless device and location server as a function of an elapsed time for the request to the wireless device to be received and as a function of an elapsed time for the transmitted first signal to be received; and
(e) determining satellite assistance data as a function of current network time and the determined path delay estimate.
2 . The method of claim 1 wherein the determined path delay estimate is determined by the following relationship:
( t req −t rsp )/2
where t req represents the elapsed time for the request to the wireless device to be received and t rsp represents the elapsed time for the transmitted first signal to be received.
3 . The method of claim 1 wherein the location server is an evolved serving mobile location center (“E-SMLC”).
4 . The method of claim 1 wherein the step of determining a path delay estimate further comprises accounting for variations in path delay as a function of packet size.
5 . The method of claim 1 further comprising the step of refining the path delay estimate as a function of acknowledgement messages transmitted from the server or wireless device.
6 . The method of claim 1 wherein the communications network is a long term evolution (“LTE”) communications network.
7 . The method of claim 1 wherein the first signal includes one or more parameters selected from the group consisting of: transport channel parameters, physical channel parameters, Packet data Convergence Protocol parameters, Radio Link Control parameters, physical layer parameters, radio frequency parameters, measurement parameters, Inter-Radio Access Technology parameters, General parameters, Multimedia Broadcast Multicast Service related parameters, and combinations thereof.
8 . The method of claim 1 further comprising the steps of:
(i) using the satellite assistance data to measure signals from one or more GNSS satellites;
(ii) determining a location of the wireless device as a function of the measured signals.
9 . The method of claim 8 wherein the location of the wireless device is determined at the wireless device.
10 . The method of claim 8 wherein the location of the wireless device is determined by the server using satellite measurements provided to the server from the wireless device.
11 . The method of claim 1 wherein the first signal includes one or more parameters of GNSS assistance data selected from the group consisting of: satellite ephemeris and clock parameters, ionosphere model, UTC model, differential GPS corrections, other GNSS assistance data, and combinations thereof.
12 . A method for estimating a location of a wireless device in a communications network, the method comprising:
(a) transmitting a location request from the wireless device to a server;
(b) determining a path delay estimate between the server and the wireless device as a function of a redundant request transmitted by the server to the wireless device or as a function of messages provided in an acknowledgement sub-layer;
(c) determining satellite assistance data as a function of current network time and the determined path delay estimate;
(d) using the satellite assistance data to measure signals from one or more Global Navigation Satellite System (“GNSS”) satellites; and
(e) determining a location of the wireless device as a function of the measured signals.
13 . The method of claim 12 where the server is an evolved serving mobile location center (“E-SMLC”).
14 . The method of claim 12 wherein the communications network is a long term evolution (“LTE”) communications network.
15 . The method of claim 12 wherein the step of transmitting a location request further comprises transmitting a location request to the server via a mobility management entity (“MME”).
16 . A method for estimating a location of a wireless device in a communications network, the method comprising:
(a) transmitting a location request from the wireless device to server;
(b) determining a path delay estimate between the server and the wireless device as a function of a default value or as a function of a path delay estimate previously determined for a node serving the wireless device;
(c) determining satellite assistance data as a function of current network time and the determined path delay estimate;
(d) using the satellite assistance data to measure signals from one or more Global Navigation Satellite System (“GNSS”) satellites; and
(e) determining a location of the wireless device as a function of the measured signals.
17 . The method of claim 16 where the server is an evolved serving mobile location center (“E-SMLC”).
18 . The method of claim 16 wherein the communications network is a long term evolution (“LTE”) communications network.
19 . The method of claim 16 wherein the step of transmitting a location request further comprises transmitting a location request to the server via a mobility management entity (“MME”).