Optimal coding of gps measurements for precise relative positioning

A system for coding GPS measurements in a vehicle communications system, said system comprising:

• a stand-alone position and velocity estimator receiving GPS measurement information at a first time and a prediction of a latent state vector from a previous time, said position and velocity estimator generating an estimated latent state vector, wherein the GPS measurement information includes satellite ephemeris, code range, carrier phase and Doppler shift for satellites and includes a series of data frames including an initialization frame, an additional data frame, a differential frame and a measurement frame and wherein the stand-alone position and velocity estimator provides the latent state vector to include six-dimensions of the position and velocity in earth-center/earth-fixed coordinates of satellites;
• an observation prediction model responsive to the estimated latent state vector from the position and velocity estimator and calculating an observation prediction from the estimated latent state vector;
• a first differencer responsive to the observation prediction from the observation prediction model and the GPS measurement information at the first time period and providing a first difference signal that includes model residuals;
• a first Huffman encoder responsive to the first difference signal and providing a first coded output;
• a state prediction model responsive to the estimated latent state vector from the position and velocity estimator and outputting the predicted latent state vector;
• a second differencer responsive to the estimated latent state vector from the position and velocity estimator and the predicted latent state vector from the state prediction model and generating a second difference signal that includes model residuals;
• and
• a second Huffman encoder responsive to the second difference signal and generating a second coded output.

A method for coding GPS measurements in a vehicle communications system, said method comprising:

• estimating a latent state vector using GPS measurement information at a first time and a prediction of a latent state vector from a previous time;
• calculating an observation prediction from the estimated latent state vector;
• providing a first difference signal between the observation prediction and the GPS measurement information at the first time period;
• encoding the first difference signal to provide a first coded output;
• using a state prediction model to generate the predicted latent state vector using the estimated latent state vector;
• providing a second difference signal between the estimated latent state vector and the predicted latent state vector;
• and
• encoding the second difference signal to generate a second coded output.