35 lines
1.6 KiB
Markdown
35 lines
1.6 KiB
Markdown
# E1C-pilot-aided E1B tracking
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The default E1 architecture uses two phase-coherent correlator branches:
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```text
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raw SignalSim IQ8
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-> E1C PCPS acquisition
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-> E1C 25-symbol secondary-code phase/frequency search
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-> shared double-precision carrier and code phase vectors
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-> E1C VE/E/P/L/VL -> FLL/PLL/DLL/CN0/BOC lock
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-> E1B VE/E/P/L/VL -> 4 ms Prompt stream -> I/NAV decoder
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```
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The secondary synchronizer jointly searches code phase and residual carrier
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frequency using complex 4 ms Prompt values. Its estimated secondary phase is
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then applied at every E1C primary-code epoch. Integrations may divide the 4 ms
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primary period exactly; the 2 ms navigation configuration applies the same
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secondary symbol to both halves.
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E1B navigation polarity never enters the pilot loop discriminators, C/N0
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estimator, or lock detector. The E1B branch receives the identical carrier and
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code phase arrays before either NCO advances, preserving sample-by-sample
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coherence. Only E1B Prompt I/Q is passed to symbol synchronization and I/NAV
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decoding.
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The initial 400 ms E1C secondary search operates on a buffered portion of the
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same input stream. The offline regression replays that buffer through the
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closed loops after synchronization; it does not load frozen Prompt, symbol,
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page, or ephemeris artifacts. A streaming implementation can use the same
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bounded input buffer or start output after synchronization.
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This pilot architecture is a separate robustness improvement. It is not used
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to conceal the legacy BOC metric defect: E1B-only and E1C-aided modes are both
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evaluated with the same corrected BOC-aware lock detector.
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