Question

Assume that a bit sequence "10000000" has been transmitted through a transmission media using parity bits. Two bits have been altered in the path and the receiver has received it as "10000011". will the receiver be able to detect the error. Justify your answer.

Answer 1

Given bit sequence 10000000. Here the data is transmitted through the transmission media using parity bits.

Here parity bits are extra bits that are added to the original data to check the data integrity after transmission.

Note:- Usually, If the count of 1s in the data is an even number then the parity bit is 0 will be used and If the count of 1s in the data is an odd number then the parity bit is 1. Here all the data is 0s only so parity bit 1 is added.

Now given that two bits have been altered and the bit sequence after alteration became 10000011. So let's check from the side of the receiver can we find that data is altered or not. As we said before if the count of 1s in data is even then parity will be 0. But here we have 1 as the parity bit. by this, we can say that the data has been altered.

Here the receiver is able to detect the error.

But wait, In this case, it works but usually this parity checking to find errors won't work if the altered bits are more than 1.

Important:-

We can prove this by altering 3 bits now. Change all the last 3 bits to 1. Now the parity should be 1 and it's also there 1. It showing no alteration but we altered 3 bits there. So parity checking fails.

Parity checking doesn't support Multiple bit error detection.

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