Error detection Flashcards
What can be the result of an error in the context of data transmission ?
It can either be a forbidden code word or another valid code word
How is the strenght of a given code measured ?
Strenght is measured in the distance between adjacent code word.
How is distance used in order to fix the error ?
If there is a larger number of forbidden code words between two code words the result of a transmission if invalid will be grouped with the closer valid code word with respect to its distance
What are two groups of error protection codes ?
Error detection codes and Error correction codes.
EXTRA :
ERROR DETECTION : d ( min ) >= t + 1
ERROR CORRECTION : d ( min ) >= 2t + 1
What is the problem with using distance to fix error ?
It creates a large amount of unused code words.
How is parity bit used in order to prevent errors ?
A 0 or a 1 is added to the most significant position in order to create either a odd or even amount of ones in a given code word. This solution detects every single bit error. The problem comes from the fact that it can not correct it as well as the fact that it adds even more digits
How can two dimensional code be used to protect against errors ? What is the problem with this solution ?
Code words must are placed one below the other and at the start of each row ( on the left ) and each column ( down ) a parity bit is added. This solution provides security against single bit errors as well as being able to correct the error by checking the parity of each row and column. The problem comes from the fact that it can not correct a double error it can only detect it in a single row or a column due to the fact that a double error does not change the parity.
What is block check character ?
character added to a given block in order to prevent errors
Describe multi-parity testing.
Refer to the docx. file
What do you know about the Hamming code ?
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