Real-time software receiver
First Claim
Patent Images
1. A method for computing prompt and early-minus-late in-phase and quadrature summed accumulations for a plurality of signals from a plurality of channels comprising the steps of:
- representing a carrier replica signal from the at least one channel from the plurality of channels as a carrier replica sign and a carrier replica magnitude;
representing signal data from the at least one channel of the plurality of channels as at least one signal word;
computing a baseband mixed sign as a function of the carrier replica sign and the at least one signal word;
computing a baseband mixed magnitude as a function of the carrier replica magnitude;
selecting a pseudo-random number (PRN) code having a prompt PRN code and an early-minus-late PRN code;
representing the prompt PRN code as a prompt PRN code sign;
computing a fully mixed prompt integrand sign as a function of the baseband mixed sign and the prompt PRN code sign;
representing the early-minus-late PRN code as an early-minus-late PRN code sign and an early-minus-late PRN code zero mask;
computing a fully mixed early-minus-late integrand sign as a function of the baseband mixed sign and the early-minus-late PRN code sign;
computing at least one set of prompt integrand value words as a function of the fully mixed prompt integrand sign and the baseband mixed magnitude;
computing at least one set of early-minus-late integrand value words as a function of the fully mixed early-minus-late integrand sign, the baseband mixed magnitude, and early-minus-late PRN code zero mask;
computing prompt in-phase and quadrature summed accumulations for the plurality of channels for an accumulation interval as functions of the number of significant bits in the at least one set of prompt integrand value words and as functions of the values associated with the at least one set of prompt integrand value words; and
computing early-minus-late in-phase and quadrature summed accumulations for the plurality of channels as functions of the number of significant bits in the at least one set of early-minus-late integrand value words and as functions of the values associated with the at least one set of early-minus-late integrand value words.
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Abstract
A real-time software receiver that executes on a general purpose processor. The software receiver includes data acquisition and correlator modules that perform, in place of hardware correlation, baseband mixing and PRN code correlation using bit-wise parallelism.
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Citations
26 Claims
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1. A method for computing prompt and early-minus-late in-phase and quadrature summed accumulations for a plurality of signals from a plurality of channels comprising the steps of:
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representing a carrier replica signal from the at least one channel from the plurality of channels as a carrier replica sign and a carrier replica magnitude;
representing signal data from the at least one channel of the plurality of channels as at least one signal word;
computing a baseband mixed sign as a function of the carrier replica sign and the at least one signal word;
computing a baseband mixed magnitude as a function of the carrier replica magnitude;
selecting a pseudo-random number (PRN) code having a prompt PRN code and an early-minus-late PRN code;
representing the prompt PRN code as a prompt PRN code sign;
computing a fully mixed prompt integrand sign as a function of the baseband mixed sign and the prompt PRN code sign;
representing the early-minus-late PRN code as an early-minus-late PRN code sign and an early-minus-late PRN code zero mask;
computing a fully mixed early-minus-late integrand sign as a function of the baseband mixed sign and the early-minus-late PRN code sign;
computing at least one set of prompt integrand value words as a function of the fully mixed prompt integrand sign and the baseband mixed magnitude;
computing at least one set of early-minus-late integrand value words as a function of the fully mixed early-minus-late integrand sign, the baseband mixed magnitude, and early-minus-late PRN code zero mask;
computing prompt in-phase and quadrature summed accumulations for the plurality of channels for an accumulation interval as functions of the number of significant bits in the at least one set of prompt integrand value words and as functions of the values associated with the at least one set of prompt integrand value words; and
computing early-minus-late in-phase and quadrature summed accumulations for the plurality of channels as functions of the number of significant bits in the at least one set of early-minus-late integrand value words and as functions of the values associated with the at least one set of early-minus-late integrand value words. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method for generating over-sampled prompt and early-minus-late pseudo-random number (PRN) codes in a bit-wise parallel format comprising the steps of:
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formulating a tabulated function for use in translating code chip and timing information into over-sampled prompt and early-minus-late PRN code in the bit-wise parallel format;
generating at least one prompt PRN code in real-time;
choosing at least one chip value from the at least one prompt PRN code, the at least one chip value corresponding to at least one data interval that contains at least one sample of a data word, the at least one chip value having a known timing relative to the at least one data interval;
transforming the relative timing into a time grid index; and
translating the at least one chip value and the time grid index during the at least one data interval into the over-sampled prompt and early-minus-late PRN codes in bit-wise parallel format for the at least one data interval, said step of translating resulting from the use of the tabulated function. - View Dependent Claims (23, 24)
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25. A method for using over-sampled prompt and early-minus-late pseudo-random number (PRN) code replica data words that are stored in a bit-wise parallel representation in a pre-computed table consisting of the steps of:
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selecting the over-sampled prompt and early-minus-late PRN code based on over-sampled prompt and early-minus-late PRN code start time as measured relative to an RF data sample time, said step of selecting substantially matching the midpoint of the over-sampled prompt and early-minus-late PRN code with a desired PRN code midpoint; and
bit-shifting the over-sampled prompt and early-minus-late PRN code data words, said step of bit-shifting insuring that the over-sampled prompt and early-minus-late PRN code start time corresponds with a pre-selected sample interval.
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26. A method for tracking the phase of a pseudo-random number (PRN) code to track the timing of its chips comprising the steps of:
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latching PRN code phase, carrier phase, epoch counters, and carrier frequencies at a pre-specified time;
computing a pseudo range using the PRN code phase and the epoch counters;
tracking and updating the PRN code phase and the carrier phase by estimating code chipping rate and carrier Doppler shift inputs; and
computing the PRN code phase at the pre-specified time as a function of the updated code chipping rate and the pre-specified time.
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Specification