FA-72280 / Error-correcting codes / Member archive

Chase combining saturates after every addition · case 05

Retransmissions that disagree strongly are combined with the wrong sign or magnitude.

Member previewVariant 5 · 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 [[[null, 5, 8, 8, 0, 0], [-6, 2, -1, 2, 2, 11], [2, 0, -9, null, -9...	`[[-4, 7, -3, 7, -7, 7], [1, 0, 1, 0, 1, 0]]`	`[[-4, 7, -2, 7, -7, 7], [1, 0, 1, 0, 1, 0]]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.