Internet-based time and frequency recovery for position fixing of GNSS receiver

A method for synchronizing a local clock at a device, comprising:

• determining, using a processor and for each packet exchange of a plurality of packet exchanges between a master device and a slave device in a packet-based network of computers, a) a round trip delay (RTD) based on i) a first message sent from the master device to the slave device and ii) a second message sent from the slave device to the master device, and b) a time offset for use in adjusting a local clock at the slave device based on the RTD, wherein each RTD and its respective time offset for each respective packet exchange is a doublet, and wherein the determining includes obtaining a respective doublet for each packet exchange of the plurality of packet exchanges;
• loading the plurality of doublets into a data register;
• ordering the plurality of doublets in the data register according to RTD by starting with the doublet having the smallest RTD of all of the plurality of doublets and continuing to the doublet having the largest RTD of all of the plurality of doublets;
• removing a subset of adjacent doublets in the ordered data register that includes the doublet having the largest RTD of all of the plurality of doublets;
• manipulating the time offsets of the doublets remaining in the ordered data register after the removing step to obtain a slave device offset estimate;
• and
• providing the slave device offset estimate for use in updating the local clock of the slave device.

A system for synchronizing a local clock at a receiver device, the system comprising:

• a local clock operative to generate a timing signal;
• a network interface module in operative communication with an asynchronous packet-switched communication network to engage in a series of synchronization packet exchanges with a grandmaster device;
• a synchronization module in operative communication with the network interface module for synchronizing the timing signal generated by the local clock based on the packets exchanges with the grandmaster device, wherein the synchronization module includes a set of computer-readable instructions that are executable by a processor to:
• determine, for each of the packet exchanges, a) a round trip delay (RTD) based on i) a first message sent from the grandmaster device to the receiver device and ii) a second message sent from the receiver device to the grandmaster device, and b) a time offset for use in adjusting the timing signal generated by the local reference oscillator based on the RTD, wherein each RTD and its respective time offset for each respective packet exchange is a doublet, and wherein a respective doublet is obtained for each packet exchange of the series of packet exchanges;
• load the plurality of doublets into a data register;
• order the plurality of doublets in the data register according to RTD by starting with the doublet having the smallest RTD of all of the plurality of doublets and continuing to the doublet having the largest RTD of all of the plurality of doublets;
• identify a subset of adjacent doublets in the ordered data register that includes the doublet having the smallest RTD of all of the plurality of doublets;
• manipulate the time offsets of the identified subset of adjacent doublets to obtain a receiver device offset estimate;
• and
• provide the receiver device offset estimate for use in synchronizing the local clock of the receiver device.