27-11-2012, 02:45 PM
ERROR CORRECTION
ERROR CORRECTION.pptx (Size: 269.92 KB / Downloads: 54)
Error Correction can be handled in two ways
When an error is discovered, the receiver can have the sender retransmit the entire data unit.
The receiver can use the error correcting code, which automatically corrects certain errors.
Most error correction techniques is limited to one or two or three bit errors.
Single bit Error Correction
An error occurs when the receiver reads a 1 bit as 0 and 0 bit as 1.
To correct the error, the receiver simply reverses the value of the altered bit.
Redundancy Bits
To calculate the number of redundancy bits® required to correct a given number of data bits (m), we must find a relationship between m and r.
If the total number of bits in a transmittable unit is m+r, then r must be able to indicate atleast m+r+1 different states.
Of these 1 state means no error and n+r states indicate the location of an error in each of m+r positions.
m+r+1 states must be discoverable by r bits. And r bits can indicate 2r different states.