Assignment 2

Assigned: 10/2/09, Due: 10/8/09


Note: If you are using the 3rd edition, look for the corresponding problem numbers in square brackets.
  1. If the following bit-stuffed data portion of an HDLC frame arrived at the receiver, what would the receiver extract? Without even looking at the checksum for this frame how does the receiver knows there is an error? (10 points)
    1 1 0 1 0 1 1 1 1 1 0 1 0 1 1 1 1 1 0 1 0 1 1 1 1 1 1 1 0

  2. Why is it desirable to have the error detection bits be a fixed length? Note that they are in case of CRC and checksum algorithms but not 2-D parity? (5 points)

  3. Assuming a framing protocol that uses bit stuffing, show the bit sequence transmitted over the link when the frame contains the following bit sequence: (5 points)
    11010111111101011111101011111110

  4. Suppose we want to transmit the message 11011001 and protect it from errors using the CRC divisor polynomial x^3+1.
    1. Use polynomial long division to determine the message that should be transmitted. (10 points)
    2. Suppose the leftmost bit of the message is inverted due to noise on the transmission link. What is the result of receiver's calculation? How does the receiver know that an error has occurred? (5 points)

  5. Chapter 2, problem 23 [Chapter 2, problem 23]. (10 points)

  6. Chapter 2, problem 24 [Chapter 2, problem 24]. (10 points)

  7. Chapter 2, problem 61 [Not in 3rd edition, see 4th edition]. (10 points)

  8. Chapter 3, problem 15 [Chapter 3, problem 15]. (10 points)

  9. Chapter 3, problem 18 [Chapter 3, problem 18]. (10 points)