日志
ECC
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天气: 阴雨
心情: 平静
§ECC?
§Error Correction Code
§Add redundant bits to detect and correct error
§Encoding and decoding
SEC ： single error correction
DEC： double error correction
hamming distance
§The number of positions in which two code words differ
§d_min--- Minimum Hamming Distance
–Detect e bits error only: d_min≥e+1
–Correct t bits error only:〖 d〗_min≥2t+1
–Detect e bits and correct t bits: d_min≥t+e+1, (e≥t)
hamming code
§Single Error correction, Single Error detection (SEC-SED)
§For (n,k), 2^r-1≥k+r, (r=n-k)
§Hamming distance ≥ 3
enhanced hamming code
§Add one parity bit for overall even parity check
§Single Error Correction, Double Error Detection
§Hamming distance ≥4
§For (n,k), 2^(r-1)≥k+r, (r=n-k)
–k=8, r=5
–k=16, r=6
optimal minimum odd weighted code
§SEC-DED
§Parity Check matrix (H-Matrix)
–There are no all-0 columns
–Every column is distinct
–Each column has odd number of 1’s (odd-weight-column)
–Total number of 1’s in matrix should be minimum (minimum)
–Number of 1’s in each row should be made equal or as close as possible (optimal)
§For (n,k), 2^(r-1)≥k+r, (r=n-k)
–k=8, r=5
–k=16, r=6
具体的矩阵构造，encode/decode详细内容未列
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