Trellis Diagram with Forward/Backward Metrics
Log-Likelihood Ratios (LLR) per Bit
Decoded Sequence Comparison
Hard Decision Errors
0
Soft Decision (BCJR) Errors
0
Bit 0
Bit 1
Error Position
8 bits
3.0 dB
Seed: 42
Encoder: Rate 1/2 (7, 5)
Generator 1:
g1 = 111 (7)
Generator 2:
g2 = 101 (5)
Constraint Length:
K = 3
States:
4 (00, 01, 10, 11)
Current Metrics
α (Forward):
-
β (Backward):
-
γ (Branch):
-
Algorithm Steps
1. Encode: Message → Codeword
2. Transmit: Add AWGN noise
3. γ (Branch): Channel LLRs
4. α (Forward): Left-to-right
5. β (Backward): Right-to-left
6. APP: Combine α, β, γ
7. LLR: Soft decisions
2. Transmit: Add AWGN noise
3. γ (Branch): Channel LLRs
4. α (Forward): Left-to-right
5. β (Backward): Right-to-left
6. APP: Combine α, β, γ
7. LLR: Soft decisions