Question

A bit-stuffing based framing protocol uses an 8-bit delimiter pattern of 01111110. If the output bit-string after stuffing is 01111100101, then the input bit-string is

• A. 0111110100
• B. 0111110101
• C. 0111111101
• D. 0111111111

Hint:

- In bit stuffing, insert a '0' after five consecutive '1's in the data stream. - To recover the original data, remove any extra stuffed '0' after five '1's.

Answer 1

The Correct Option is B

Step 1: Understanding Bit Stuffing
- In bit-stuffing, an extra '0' bit is inserted after every sequence of five consecutive '1's to prevent confusion with the frame delimiter (01111110).
- Given the stuffed output 01111100101, we need to remove any extra stuffed '0' bits.
Step 2: Removing the Stuffed Bit
- Identifying the stuffed '0', we see 01111100 in the given output.
- The stuffed bit '0' follows five consecutive '1's.
- Removing the stuffed '0', we get the original input 0111110101.
Step 3: Evaluating the Options
- (A) Incorrect: 0111110100 is different from the obtained result.
- (B) Correct: 0111110101 matches the calculated input.
- (C) Incorrect: 0111111101 does not follow from the stuffing process.
- (D) Incorrect: 0111111111 is an incorrect assumption.