Homework 4 - Chapter 4

Due: Sunday May 1, 2011 at 5:00pm NOTE: No late homework will be accepted so the solution can be posted before the midterm for you to study.

  1. (4 pts) Describe how the delay and throughput would differ between pure ALOHA and slotted ALOHA under the following conditions. Which would be higher? Explain why.
    1. Low load (few stations transmitting)
    2. High load (many stations transmitting)
  2. (2 pts) Describe how the delay and throughput would differ between 1-persistent CSMA and non-persistent CSMA.
  3. (4 pts) You are designing a network that will use CSMA/CD for contention. The physical media has the following characteristics: 1.5Mbps, signal speed is 2/3rds the speed of light and maximum cable length is 500m.
    1. How long would the contention slot have to be?
    2. What would be the minimum frame size (i.e. how long would a frame have to be so it takes longer to transmit than the length of a contetion slot)?
  4. (4 pts) Draw the Manchester and differential Manchester encodings for the bit sequence 01100011.
  5. (2 pts) Two half-duplex Ethernet stations are contending for the channel. What is the mean number of contention slots for these two stations?
  6. (2 pts) Explain why Manchester encoding cannot be used for Gigabit and Fast Ethernet.
  7. (2 pts) What encoding method is used on twisted pair for Fast Ethernet instead of Manchester encoding?