Data Technologies-CERN School af Compuaing 2019 Data Technologes-CERN School of Computing 2019 Understanding error correction If we lose some information .. A line is defined by 2 numbers:a,b If we transmit more than 2 points,we can lose (a,b)is the information any point,provided the total number of point left ◆y=ax+b is>=2 Instead of transmitting a and b,transmit some points on the line at known abscissa.2 points define a line.If I transmit more points,these should be aligned. 1 point instead of 2 2 points instead of 3 2 or 3 points instead of 4 2 points 3 points 4 points information lost Data Technologles-CERN School af Compuang 2019 Data Technologles-CERN School of Computing 2019 If we have an error... If you have checksumming on data .. If there is an error,I can detect it if I have You can detect errors by verifying the transmitted more than 2 points,and correct it if consistency of the data with the respective have transmitted more than 3 points checksums.So you can detect errors independently. ..and use all redundancy for error correction Informason lost Error detection Error comection Infommation lost 2 Eror corrections possible (and you do not notice) Information is lost Information is recovered (and you notice) Infommation is recovered Information is recovered (and you notice)38 Data Technologies – CERN School of Computing 2019 Understanding error correction  A line is defined by 2 numbers: a, b  (a, b) is the information  y = ax + b  Instead of transmitting a and b, transmit some points on the line at known abscissa. 2 points define a line. If I transmit more points, these should be aligned. 2 points 3 points 4 points 39 Data Technologies – CERN School of Computing 2019 2 points instead of 3 2 or 3 points instead of 4 1 point instead of 2 information lost If we lose some information …  If we transmit more than 2 points, we can lose any point, provided the total number of point left is >= 2 ? 40 Data Technologies – CERN School of Computing 2019 If we have an error …  If there is an error, I can detect it if I have transmitted more than 2 points, and correct it if have transmitted more than 3 points Information lost (and you do not notice) Error detection Information is lost (and you notice) Error correction Information is recovered ? 41 Data Technologies – CERN School of Computing 2019 If you have checksumming on data …  You can detect errors by verifying the consistency of the data with the respective checksums. So you can detect errors independently.  … and use all redundancy for error correction Information lost (and you notice) Error correction Information is recovered 2 Error corrections possible Information is recovered ?