Multi-path mitigation in tracking objects using compressed RF data
A split architecture is disclosed for determining the location of a wireless device in a heterogeneous wireless communications environment. A detector within the device or another component of the environment receives signals including parameters for a localization signal of the device. The parameters describe known in advance signals within the signals. Additional metadata including each frame start of the signals and assistance data and auxiliary information are also received. The known in advance signals are detected based on the parameters of the localization signal. Samples extracted from the known in advance signals are then processed and compressed and sent with other collect data to a locate server remote from the detector. The location server uses that information as well as similar information about the environment to calculate the location of the device, as well as perform tracking and navigation of the device, and report such results to the environment.
1. A method for preparing RF data for use in determining a location of a wireless mobile device in a wireless communications environment, comprising:
receiving signals from one or more receive channels that include parameters for a localization signal of the wireless mobile device, wherein the parameters of the localization signal describe known in advance signals within the signals;
receiving first metadata including each frame start of the signals and one or more of assistance data and auxiliary information;
detecting the known in advance signals from each receive channel among the one or more receive channels based on the parameters of the localization signal;
buffering a plurality of samples in a digital format extracted from the known in advance signals;
compressing in a digital format the plurality of samples to reduce a data size of the plurality of samples; and
sending the compressed data, the parameters of the localization signal, and the metadata to a locate server physically remote from the detector for determination of the location.
2. The method of claim 1 , wherein detecting comprising extracting the plurality of samples in the digital forma from the known in advance signals.
3. The method of claim 2 , wherein extracting comprising collecting a number of the digital samples per antenna at a receiver and collecting a signal identification corresponding to each digital sample.
4. The method of claim 2 , wherein compressing comprising pre-processing the collected digital samples to reduce the data size before sending the compressed data to the locate server.
5. The method of claim 4 , wherein pre-processing comprising extracting digital samples from the collected digital samples that only represent the known in advance signals that will be used to determine the location.
6. The method of claim 4 , wherein pre-processing comprising making a subset of data samples from the collected digital samples available in a frame of a GPS/GNSS navigation message.
7. The method of claim 6 , wherein pre-processing wherein the assistance data is carried in a remainder of the navigation message.
8. The method of claim 7 , wherein the assistance data includes one or more of a reference time, a reference location, a satellite ephemeris, clock corrections, Ionospheric Models, Earth Orientation Parameters, GNSS Time Offsets, an Acquisition Assistance, an Almanac, and UTC Models.
9. The method of claim 1 , wherein compressing comprising utilizing one or more of a A-law compounding algorithm and a U-law compounding algorithm.
10. The method of claim 1 , wherein compressing comprising reducing a sample size of each digital sample size to a smaller number of bits.
11. The method of claim 1 , wherein compressing comprising employing a coherent compression scheme wherein a size of a resultant data sample to be sent to the locate server for observable estimation is reduced to a non-zero portion of a cross-correlation output of the known in advance signal received at the one or more receive channels and integrating a number of uniquely identified known in advance signals received.
12. The method of claim 1 , wherein compressing comprising employing a compression scheme including matched filtering of the known in advance signals combined with carrier frequency offset (CFO) processing per each uniquely identified known in advance signal received and integrating in time of a number of resultant digital samples.
13. The method of claim 1 , wherein compressing comprising matched filtering of only known in advance signals used for determination of the location.
14. The method of claim 1 , wherein compressing comprising calculating singular-value decomposition (SVD) principle eigenvalues of a matrix formed from one or more of the digital samples.
15. The method of claim 1 , wherein compressing comprising performing additional pre-processing based on a tradeoff between a computational load resources required and a reduction of communication bandwidth with the locate server.