Autonomous transmit chain delay measurements
A system and method for determining transmission delay in a communications system. In some embodiments, satellite positioning information having System Frame Number (SFN) information may be received for a mobile device and observed time difference of arrival (OTDOA) measurements may be received for a mobile device. A location of the mobile device may be determined as a function of the received satellite positioning information. A Global Positioning System (GPS) time estimate may be determined as a function of the determined location of the mobile device. Transmission delay between a node serving the mobile device and an antenna serving the mobile device may be determined as a function of the received OTDOA measurements and determined GPS time estimate.
1. A method of determining transmission delay in a communications network having a plurality of nodes comprising the steps of:
(a) receiving satellite positioning information for a mobile device, the received satellite positioning information including System Frame Number (SFN) information;
(b) receiving observed time difference of arrival (OTDOA) measurements for a mobile device from one or more of the plural nodes;
(c) determining a location of the mobile device as a function of the received satellite positioning information;
(d) determining a Global Positioning System (GPS) time estimate as a function of the determined location of the mobile device; and
(e) determining transmission delay between a node serving the mobile device and an antenna serving the mobile device as a function of the received OTDOA measurements and determined GPS time estimate.
2. The method of claim 1 wherein the step of receiving satellite positioning information further comprises requesting the mobile device to report a GPS to network time relationship.
3. The method of claim 1 wherein the serving node is an eNodeB.
4. The method of claim 1 wherein the OTDOA measurements include SFN initialization time.
5. The method of claim 1 further comprising the step of determining propagation delay between the serving antenna and the mobile device as a function of the determined mobile device location and location of the serving antenna, wherein the determined transmission delay is a function of the determined propagation delay.
6. The method of claim 5 wherein the determined propagation delay is a function of a transmission path from the mobile device to the serving antenna or from the serving antenna to the mobile device.
7. The method of claim 1 wherein the step of determining transmission delay further comprises determining cable delay and/or radio frequency component delay.
8. The method of claim 1 further comprising the step of iteratively repeating step (c) and averaging the determined locations over the iteration.
9. The method of claim 1 further comprising the step of determining a location of one or more other mobile devices using respective received satellite information, wherein the step of determining transmission delay comprises determining transmission delay as a function of the determined locations of the one or more other mobile devices to minimize bias.