System and method for sub-coherent integration for geo-location using weak or intermittent signals
First Claim
1. A method for determining a time of arrival of a signal transmitted by a mobile device, the method comprising:
- receiving a signal from a mobile device as a plurality of data samples, the received signal including a first component corresponding to a known reference signal and a second component corresponding to at least one of an unknown channel impairment and an unknown noise;
forming a sequence of blocks based on the received samples, wherein the first component of the received signal corresponding to the reference signal is known to within a constant phase shift over each block;
generating a first plurality of function values as a function of time, frequency, and phase, based on the received signal, wherein the function values of the first plurality correspond to a plurality of times, a plurality of frequencies, and a plurality of phase sequences, and the function values of the first plurality are calculated to compensate for frequency and phase discontinuities and drift;
determining a time, a frequency, and a phase sequence corresponding to an optimal value of the first plurality of function values; and
outputting the determined time as the time of arrival of the received signal.
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Abstract
A signal is received from a mobile device as multiple data samples. The received signal includes a first component corresponding to a known reference signal and a second component corresponding to an unknown channel impairment or an unknown noise. A sequence of blocks is formed based on the received samples. The first component of the received signal corresponding to the reference signal is known to within a constant phase shift over each block. A plurality of function values are generated as a function of time, frequency, and phase, based on the received signal, corresponding to a plurality of times, a plurality of frequencies, and a plurality of phase sequences. A time, a frequency, and a phase sequence corresponding to an optimal value the function values are determined. The determined time is outputted as a time of arrival of the received signal.
185 Citations
20 Claims
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1. A method for determining a time of arrival of a signal transmitted by a mobile device, the method comprising:
receiving a signal from a mobile device as a plurality of data samples, the received signal including a first component corresponding to a known reference signal and a second component corresponding to at least one of an unknown channel impairment and an unknown noise;
forming a sequence of blocks based on the received samples, wherein the first component of the received signal corresponding to the reference signal is known to within a constant phase shift over each block;
generating a first plurality of function values as a function of time, frequency, and phase, based on the received signal, wherein the function values of the first plurality correspond to a plurality of times, a plurality of frequencies, and a plurality of phase sequences, and the function values of the first plurality are calculated to compensate for frequency and phase discontinuities and drift;
determining a time, a frequency, and a phase sequence corresponding to an optimal value of the first plurality of function values; and
outputting the determined time as the time of arrival of the received signal.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A non-transitory computer readable storage medium having instructions stored tangibly thereon, the instructions when executed by a processor causing the processor to perform the operations of:
receiving a signal from a mobile device as a plurality of data samples, the received signal including a first component corresponding to a known reference signal and a second component corresponding to at least one of an unknown channel impairment and an unknown noise;
forming a sequence of blocks based on the received samples, wherein the first component of the received signal corresponding to the reference signal is known to within a constant phase shift over each block;
generating a first plurality of function values as a function of time, frequency, and phase, based on the received signal, wherein the function values of the first plurality correspond to a plurality of times, a plurality of frequencies, and a plurality of phase sequences, and the function values of the first plurality are calculated to compensate for frequency and phase discontinuities and drift;
determining a time, a frequency, and a phase sequence corresponding to an optimal value of the first plurality of function values; and
outputting the determined time as the time of arrival of the received signal.- View Dependent Claims (15, 16)
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17. A method for determining a time of arrival of a signal transmitted by a mobile device, the method comprising:
receiving a signal from a mobile device as a plurality of data samples, the received signal including a first component corresponding to a known reference signal and a second component corresponding to at least one of an unknown channel impairment and an unknown noise;
forming a sequence of blocks based on the received samples;
dividing the sequence of blocks into plural sets of blocks, wherein for each set, the first component of the received signal corresponding to the reference signal is known to within a constant phase shift over each block in said set;
for each set;
generating a plurality of function values as a function of time, frequency, and phase, based on the received signal, wherein the function values of the plurality correspond to a plurality of times, a plurality of frequencies, and a first plurality of phase sequences, and the function values are calculated to compensate for frequency and phase discontinuities and drift, and determining a time, a frequency, and a phase sequence associated with said set corresponding to an optimal value of the first plurality of function values; and
determining the time of arrival based on the determined times associated with respective sets.- View Dependent Claims (18, 19)
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20. A method for determining a time of arrival of a signal transmitted by a mobile device, the method comprising:
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receiving a signal from a mobile device as a plurality of data samples, the received signal including a first component corresponding to a known reference signal and a second component corresponding to at least one of an unknown channel impairment and an unknown noise; forming a sequence of blocks based on the received samples, wherein the first component of the received signal corresponding to the reference signal is known to within a constant phase shift over each block; generating, for each block, a first plurality of function values as a function of time and frequency, based on the received signal, wherein the function values of the first plurality correspond to a plurality of times and to a plurality of frequencies; sorting the sequence of blocks according to a predetermined metric; dividing the sorted sequence of blocks into plural sets of blocks, wherein the sets are ranked according to an order; at an initial processing stage Z0, determining at least one candidate phase sequence based on a function of time, frequency, and phase and based on an initial set S0 among the sets of blocks; at each stage Zi of one or more subsequent processing stages corresponding to respective distinct sets other than said initial set S0, determining at least one candidate phase sequence based on the function of time, frequency, and phase, further based on a set Sj corresponding to said processing stage, and further based on the sets preceding set Sj, wherein an initial subsequence of each candidate phase sequence determined at stage Zi includes one of the candidate phase sequences determined at a stage Zi-1 preceding stage Zi; determining a time, a frequency, and a phase sequence that optimize the function of time, frequency, and phase based on the at least one candidate phase sequence determined at a last processing stage among the subsequent processing stages; and outputting the determined time as the time of arrival of the received signal.
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Specification