Flashcards in Information Coding Systems Error Checking Deck (7)
Convert Computer Science to ASCII
067 111 109 112 117 116 101 114 032 083 099 105 101 110 099 101
What causes errors?
Bits can change during transmission because of different interference.
What is a parity bit?
Parity bits - check that bits are likely to be correct
ASCII 7 bit leaves an additional bit free. An additional bit can be added to add odd or even parity to the data. (parity bit) This is the MSB.
How do parity bits work?
If the data is checking for ODD Parity, the bit added will ensure that there are an ODD number of 1’s and vice versa for EVEN parity.
What are disadvantages of parity bits?
Parity Bits will ONLY check for errors and cannot identify or correct the error. It may also fail if there are an even number of errors:
1011011 is sent with ODD Parity and so the parity bit is 0.
1000011 is received. 2 errors have occurred but the parity bit of 0 will not catch it.
How does majority voting work?
Each bit within the data is sent 3 times. Majority Voting will select the data in the majority of each 3 bits.