FA-72282 / Error-correcting codes / Member archive

Chase combining decides zero LLRs as bit 0 · case 02

Positions with no information are reported as confident zeros.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Hybrid-ARQ chase combining. txs are equal-length LLR vectors from successive transmissions (None where a position was not received). Combined LLR = sum of received values, saturated once at the end to [-clip, clip]. Hard decision: positive -> 0, negative -> 1, zero -> None (undecided). Return [combined, hard]; empty or ragged input returns None.

Why this case matters

LTE/5G receivers soft-combine retransmissions before decoding; saturating too early discards information.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression [[[5, null]], 7]	`[[5, 0], [0, 0]]`	`[[5, 0], [0, null]]`	Failed

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