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feat: QO-100 beacon AO-40 FEC decode end-to-end (Milestone 2)
Full chain now decodes the QO-100 central beacon to 256-byte AO-40 frames on-air (frames>0, RS errors=0). Builds on M1 (stable BPSK demod). FEC backend (BeaconFEC.pas, TBeaconFEC): - AO-40 FEC: distributed sync (65 bit, step 80) -> 80x65 deinterleave -> Viterbi r=1/2 k=7 -> CCSDS descramble -> 2x RS(160,128). Links system libfec (Karn) load-time (libfec.so/.dll/.dylib). Viterbi AO-40 [0x4F,-0x6D] remapped to libfec [0x6D,0x4F]. Validated against gr-satellites reference vectors (fectest2: exact 256-byte frame, 0 mismatches). DBPSK Manchester frontend (BeaconDecoder.pas): - Chip-rate (800) processing: RRC matched filter -> ML signal-times-slope timing recovery -> Costas -> Manchester combine (block phase select) -> differential decode -> soft symbols to FEC. - Carrier acquisition: squaring-FFT estimates the residual (carrier at +-pi/chip defeats decision-directed Costas), one-shot pulls it to DC via residual NCO. - Costas frequency offload into pre-RRC NCO (with deadband) tracks LNB drift without hitting the +-pi Costas clamp. - ML TED replaces Gardner, which degenerates on the Manchester chip stream. Temporary on-air diagnostics retained (IQ dump + STATE log) pending wider signal validation; to be removed before final cleanup. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Claude Opus 4.8
+341
@@ -0,0 +1,341 @@
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unit BeaconFEC;
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{
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QO-100 центральный маяк — FEC-бэкенд (Milestone 2).
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Декодирует AO-40 FEC поверх потока мягких символов (400/с, после Manchester+
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дифф-декода фронтенда). Цепочка (ровно как gr-satellites ao40_fec_deframer):
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мягкие символы 400/с
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→ distributed sync (65 бит, шаг 80, окно 5200, порог 8, обе полярности)
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→ matrix deinterleave 80×65: out[i]=data[80*(i%65)+i/65], skip 65, take 5132
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→ Viterbi r=1/2 k=7, полиномы [0x4F, -0x6D] (CCSDS), terminated → 2560 бит/320 байт
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→ CCSDS additive descramble (LFSR mask 0xA9, seed 0xFF, len 7, XOR по битам)
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→ 2× RS(255,223) укороч. pad=95 → (160,128), conventional basis, 2-way интерлив
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→ 256 байт кадра → OnFrame.
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Viterbi и RS — через libfec Карна (разделяемая libfec.so/.dll/.dylib, load-time
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линковка как WDSP/IIO). libfec ставится отдельно на каждой ОС.
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}
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{$IFDEF FPC}{$MODE Delphi}{$ENDIF}
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{$PACKRECORDS C}
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interface
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uses
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Classes, SysUtils;
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const
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AO40_SYNC_LEN = 65;
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AO40_SYNC_STEP = 80;
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AO40_FRAME_SYMS = AO40_SYNC_LEN * AO40_SYNC_STEP; // 5200
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AO40_IL_ROWS = 80;
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AO40_IL_COLS = 65;
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AO40_VITERBI_SYM = 5132; // после skip 65
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AO40_DATA_BITS = 2560; // выход Viterbi (без 6 tail)
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AO40_CONV_BYTES = AO40_DATA_BITS div 8; // 320
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AO40_RS_NROOTS = 32;
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AO40_RS_PAD = 95; // 255-160
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AO40_RS_NN = 160; // укороченная длина
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AO40_RS_KK = 128;
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AO40_INTERLEAVE = 2;
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AO40_FRAME_BYTES = AO40_RS_KK * AO40_INTERLEAVE; // 256
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AO40_SYNC_THRESH = 8; // допуск ошибок синхры
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type
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TBeaconFrame = array[0..AO40_FRAME_BYTES-1] of Byte;
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TBeaconFrameEvent = procedure(const Frame: TBeaconFrame; RSErrors: Integer) of object;
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TBeaconFEC = class
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private
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FSync: array[0..AO40_SYNC_LEN-1] of Byte;
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FRing: array[0..AO40_FRAME_SYMS-1] of Single;
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FRingPos: Integer; // позиция следующей записи = старейший элемент
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FRingCnt: Integer;
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FCooldown: Integer; // не перепроверять сразу после успешного кадра
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FVp: Pointer; // viterbi27 instance
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FFrames: Int64;
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FOnFrame: TBeaconFrameEvent;
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function CheckSyncAt: Integer; // -1 нет; 0 норм. полярность; 1 инверсия
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procedure DecodeCurrentFrame(Invert: Boolean);
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procedure Descramble(var Buf: array of Byte; Count: Integer);
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public
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constructor Create;
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destructor Destroy; override;
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procedure Reset;
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procedure PushSoftSymbol(const S: Single);
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function SelfTest(out Msg: string): Boolean;
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property Frames: Int64 read FFrames;
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property OnFrame: TBeaconFrameEvent read FOnFrame write FOnFrame;
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end;
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implementation
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// ---------------- libfec bindings (Karn) ----------------
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// Динамическая (load-time) линковка против разделяемой libfec — как WDSP/IIO.
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// libfec ставится отдельно на каждой ОС (Linux: make install из исходников;
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// Windows/macOS — отдельная сборка). НЕ статический {$LINKLIB}: на Arch системный
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// libfec.a собран с LTO (slim-объекты без машинного кода) и не линкуется обычным ld.
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const
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{$IFDEF WINDOWS}
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FEC_LIB = 'libfec.dll';
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{$ENDIF}
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{$IFDEF LINUX}
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FEC_LIB = 'libfec.so';
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{$ENDIF}
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{$IFDEF DARWIN}
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FEC_LIB = 'libfec.dylib';
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{$ENDIF}
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{$IFDEF UNIX}{$LINKLIB m}{$ENDIF} // libfec использует log() из libm
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function create_viterbi27(len: LongInt): Pointer; cdecl; external FEC_LIB;
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function init_viterbi27(vp: Pointer; starting_state: LongInt): LongInt; cdecl; external FEC_LIB;
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function update_viterbi27_blk(vp: Pointer; syms: PByte; npairs: LongInt): LongInt; cdecl; external FEC_LIB;
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function chainback_viterbi27(vp: Pointer; data: PByte; nbits: LongWord; endstate: LongWord): LongInt; cdecl; external FEC_LIB;
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procedure delete_viterbi27(vp: Pointer); cdecl; external FEC_LIB;
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function decode_rs_8(data: PByte; eras_pos: PLongInt; no_eras: LongInt; pad: LongInt): LongInt; cdecl; external FEC_LIB;
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procedure encode_rs_8(data: PByte; parity: PByte; pad: LongInt); cdecl; external FEC_LIB;
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// ---------------- helpers ----------------
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function ParityB(x: LongWord): Byte; inline;
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// чётность числа единичных битов: 1=нечётно, 0=чётно
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begin
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x := x xor (x shr 16);
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x := x xor (x shr 8);
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x := x xor (x shr 4);
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x := x xor (x shr 2);
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x := x xor (x shr 1);
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Result := x and 1;
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end;
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const
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// 65-битная распределённая синхра AO-40 (gr-satellites _syncword)
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AO40_SYNCWORD: array[0..AO40_SYNC_LEN-1] of Byte = (
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1,1,1,1,1,1,1,0,0,0,0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,
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0,0,0,0,0,1,0,0,0,1,0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0);
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// ---------------- TBeaconFEC ----------------
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constructor TBeaconFEC.Create;
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var i: Integer;
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begin
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inherited Create;
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for i := 0 to AO40_SYNC_LEN-1 do FSync[i] := AO40_SYNCWORD[i];
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FVp := create_viterbi27(AO40_DATA_BITS);
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Reset;
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end;
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destructor TBeaconFEC.Destroy;
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begin
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if FVp <> nil then delete_viterbi27(FVp);
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inherited Destroy;
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end;
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procedure TBeaconFEC.Reset;
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var i: Integer;
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begin
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for i := 0 to AO40_FRAME_SYMS-1 do FRing[i] := 0;
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FRingPos := 0; FRingCnt := 0; FCooldown := 0;
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end;
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procedure TBeaconFEC.PushSoftSymbol(const S: Single);
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var r: Integer;
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begin
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FRing[FRingPos] := S;
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FRingPos := FRingPos + 1;
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if FRingPos >= AO40_FRAME_SYMS then FRingPos := 0;
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if FRingCnt < AO40_FRAME_SYMS then Inc(FRingCnt);
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if FCooldown > 0 then begin Dec(FCooldown); Exit; end;
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if FRingCnt < AO40_FRAME_SYMS then Exit;
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r := CheckSyncAt;
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if r >= 0 then
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begin
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DecodeCurrentFrame(r = 1);
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FCooldown := AO40_FRAME_SYMS; // следующий кадр — через полный фрейм
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end;
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end;
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function TBeaconFEC.CheckSyncAt: Integer;
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// Кандидат-кадр = текущее содержимое кольца (старейший→новейший), старт = FRingPos.
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// Синхра на относительных позициях j*step. Возвращает полярность или -1.
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var
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j, idx, hard, matches: Integer;
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begin
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matches := 0;
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for j := 0 to AO40_SYNC_LEN-1 do
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begin
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idx := FRingPos + j * AO40_SYNC_STEP;
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if idx >= AO40_FRAME_SYMS then Dec(idx, AO40_FRAME_SYMS);
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if FRing[idx] > 0.0 then hard := 1 else hard := 0; // gr-конвенция: +soft = «1»
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if hard = FSync[j] then Inc(matches);
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end;
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if matches >= AO40_SYNC_LEN - AO40_SYNC_THRESH then Exit(0); // норм. полярность
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if matches <= AO40_SYNC_THRESH then Exit(1); // инверсия
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Result := -1;
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end;
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procedure TBeaconFEC.Descramble(var Buf: array of Byte; Count: Integer);
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// CCSDS additive descrambler = GNU Radio additive_scrambler_bb(0xA9, 0xFF, 7).
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// Fibonacci LFSR, seed 0xFF, XOR с каждым битом (MSB-first), reset на старте кадра.
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var
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state: Byte;
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i, b, outp, newbit, bit: Integer;
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v: Byte;
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begin
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state := $FF;
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for i := 0 to Count-1 do
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begin
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v := Buf[i];
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for b := 7 downto 0 do
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begin
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outp := state and 1;
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newbit := ParityB(state and $A9);
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state := (state shr 1) or (newbit shl 7);
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bit := (v shr b) and 1;
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bit := bit xor outp;
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if bit <> 0 then v := v or (1 shl b) else v := v and not (1 shl b);
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end;
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Buf[i] := v;
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end;
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end;
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procedure TBeaconFEC.DecodeCurrentFrame(Invert: Boolean);
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var
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win: array[0..AO40_FRAME_SYMS-1] of Single;
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deint: array[0..AO40_FRAME_SYMS-1] of Single;
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syms: array[0..AO40_VITERBI_SYM-1] of Byte;
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conv: array[0..AO40_CONV_BYTES-1] of Byte;
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cw: array[0..AO40_RS_NN-1] of Byte;
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frame: TBeaconFrame;
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i, idx, k, j, sgn, totErr, res: Integer;
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v: Double;
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begin
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// 1. снимок кольца в хронологическом порядке (+ инверсия полярности)
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if Invert then sgn := -1 else sgn := 1;
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for i := 0 to AO40_FRAME_SYMS-1 do
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begin
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idx := FRingPos + i;
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if idx >= AO40_FRAME_SYMS then Dec(idx, AO40_FRAME_SYMS);
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win[i] := sgn * FRing[idx];
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end;
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// 2. матричный деинтерливер 80×65, out[i]=data[80*(i%65)+i/65]
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for i := 0 to AO40_FRAME_SYMS-1 do
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deint[i] := win[AO40_IL_ROWS * (i mod AO40_IL_COLS) + (i div AO40_IL_COLS)];
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// 3. skip 65 (синхра) → 5132 мягких символа → байты для libfec (255=«1»).
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// РЕМАП КОНВЕНЦИИ Viterbi: AO-40/gr-satellites кодирует полиномами [0x4F, -0x6D]
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// (cc_decoder), а libfec viterbi27 ЗАШИВАЕТ [0x6D, 0x4F] БЕЗ инверсии. Эмпирически
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// (брут-форс против gr post_viterbi_reference, см. историю) точное соответствие:
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// libfec[2p] = -soft[2p+1] (своп пары + инверсия первого символа)
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// libfec[2p+1] = soft[2p]
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// Без ремапа Viterbi выдаёт мусор → RS не корректируется.
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for i := 0 to (AO40_VITERBI_SYM div 2) - 1 do
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begin
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v := 128.0 - deint[AO40_SYNC_LEN + 2*i + 1] * 100.0; // -soft[2p+1]
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if v > 255.0 then v := 255.0 else if v < 0.0 then v := 0.0;
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syms[2*i] := Round(v);
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v := 128.0 + deint[AO40_SYNC_LEN + 2*i] * 100.0; // soft[2p]
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if v > 255.0 then v := 255.0 else if v < 0.0 then v := 0.0;
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syms[2*i+1] := Round(v);
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end;
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// 4. Viterbi r=1/2 k=7 terminated → 2560 бит = 320 байт (MSB-first)
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init_viterbi27(FVp, 0);
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update_viterbi27_blk(FVp, @syms[0], (AO40_DATA_BITS + 6)); // 2566 пар
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chainback_viterbi27(FVp, @conv[0], AO40_DATA_BITS, 0);
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// 5. CCSDS дескремблер
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Descramble(conv, AO40_CONV_BYTES);
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// 6. RS: 2-way байт-интерлив, decode_rs_8 укороч. pad=95
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totErr := 0;
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for j := 0 to AO40_INTERLEAVE-1 do
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begin
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for k := 0 to AO40_RS_NN-1 do
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cw[k] := conv[j + k * AO40_INTERLEAVE];
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res := decode_rs_8(@cw[0], nil, 0, AO40_RS_PAD);
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if res < 0 then Exit; // некорректируемо → кадр невалиден
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Inc(totErr, res);
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for k := 0 to AO40_RS_KK-1 do
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frame[j + k * AO40_INTERLEAVE] := cw[k];
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end;
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Inc(FFrames);
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if Assigned(FOnFrame) then FOnFrame(frame, totErr);
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end;
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// ---------------- self-test ----------------
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function TBeaconFEC.SelfTest(out Msg: string): Boolean;
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// Проверяет линковку libfec и базовую корректность: RS encode/decode round-trip
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// с внесёнными ошибками (укорочение pad=95) + Viterbi encode/decode round-trip.
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var
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data: array[0..AO40_RS_KK-1] of Byte;
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par: array[0..AO40_RS_NROOTS-1] of Byte;
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cw: array[0..AO40_RS_NN-1] of Byte;
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i, res, encst, sym0, sym1, errs: Integer;
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bits: array[0..AO40_DATA_BITS-1] of Byte;
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vsyms: array[0..AO40_VITERBI_SYM-1] of Byte;
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outb: array[0..AO40_CONV_BYTES-1] of Byte;
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b: Integer;
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begin
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Result := False;
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// --- RS round-trip ---
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for i := 0 to AO40_RS_KK-1 do data[i] := (i * 37 + 11) and $FF;
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encode_rs_8(@data[0], @par[0], AO40_RS_PAD);
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for i := 0 to AO40_RS_KK-1 do cw[i] := data[i];
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for i := 0 to AO40_RS_NROOTS-1 do cw[AO40_RS_KK + i] := par[i];
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// вносим 16 байтовых ошибок (= предел исправления для nroots=32)
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for i := 0 to 15 do cw[i * 9] := cw[i * 9] xor $A5;
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res := decode_rs_8(@cw[0], nil, 0, AO40_RS_PAD);
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if res < 0 then begin Msg := 'RS decode FAILED (link/params?)'; Exit; end;
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for i := 0 to AO40_RS_KK-1 do
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if cw[i] <> data[i] then begin Msg := Format('RS mismatch at %d', [i]); Exit; end;
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// --- Viterbi round-trip ---
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// libfec viterbi27 зашивает полиномы V27POLYA=$6D, V27POLYB=$4F (CCSDS) БЕЗ
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// инверсии и без API смены. Энкодер строго как у Карна (vtest27.c):
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// sr=(sr shl 1)|bit; sym0=parity(sr & $6D); sym1=parity(sr & $4F).
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// Мягкий «1» = 255, «0» = 0. + 6 хвостовых нулей (terminated).
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Randomize;
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for i := 0 to AO40_DATA_BITS-1 do bits[i] := Random(2);
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encst := 0;
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for i := 0 to AO40_DATA_BITS + 6 - 1 do
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begin
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if i < AO40_DATA_BITS then b := bits[i] else b := 0;
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encst := ((encst shl 1) or b) and $7F;
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sym0 := ParityB(encst and $6D);
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sym1 := ParityB(encst and $4F);
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vsyms[2*i] := sym0 * 255;
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vsyms[2*i+1] := sym1 * 255;
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end;
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init_viterbi27(FVp, 0);
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update_viterbi27_blk(FVp, @vsyms[0], AO40_DATA_BITS + 6);
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chainback_viterbi27(FVp, @outb[0], AO40_DATA_BITS, 0);
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errs := 0;
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for i := 0 to AO40_DATA_BITS-1 do
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begin
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b := (outb[i div 8] shr (7 - (i mod 8))) and 1; // MSB-first
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if b <> bits[i] then Inc(errs);
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end;
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if errs <> 0 then
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begin
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Msg := Format('Viterbi round-trip: %d/%d bit errors (convention mismatch)',
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[errs, AO40_DATA_BITS]);
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Exit;
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end;
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Msg := Format('OK: RS corrected 16 errs; Viterbi 0/%d bit errors', [AO40_DATA_BITS]);
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Result := True;
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end;
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end.
|
||||
Reference in New Issue
Block a user