Assume that you are transmitting data and cannot tolerate undetected errors of a
ID: 3835040 • Letter: A
Question
Assume that you are transmitting data and cannot tolerate undetected errors of any sort, and some sort of ability to correct errors in transmission would be even better. a. You transmit the 8-bit pattern: 0111001, and your counterpart receives 0111101. Assume that the parity bit is the high order bit. Has there been an error? Why do you say that? b. The overhead rate of an error detection/correction scheme is Number of parity bits/Total bits transmitted what is the overhead rate of this simple parity scheme? c. Say we decided to make the overhead smaller, by using this same parity scheme, but instead of protecting 7 bits with one parity bit, we are protecting 62 bits. i. Is that necessarily better? ii. What are the disadvantages of 1 parity bit for 62 bits of data versus one parity bit for 7 bits of data?Explanation / Answer
a.
yes there is an error , Because the parity bit is high order bit i.e 0 in case 0111001. here we have 4 1's and
parity bit as 0 so we are using even parity scheme here i.e we have to maintain number 1's as even in data.
by using pairty bit.
now hen our counter part receives 0111101 here we have 5 1's and we were using even parity scheme which means the number of 1's have to be even but they are not hence data has been altered .
b.
overhead= number of parity bits/ Total bits data trasnmitted= 1/8 =0.125
c.
i. No,although it will reduce overhead from 0.125 to 0.0162 , but there is more chance of data alteration in large amount of bits then in small amount.
ii.
If one bit (or odd number of bits) gets inverted during transmission, then paritycheck will detect an error. In other words, only odd numbers of errors are detected by parity check. But, if two (or even number) of bits get inverted, and then the error remains undetected.
so disadvantge is that . when 1 parity is used to protect 7 bits it is better becuase lesser bits are less prone to error then 62 bits .It is more likely that more errors will occur in 62 bits and if they are even number of errors they will go undetected.