Encoding Information on an Ethernet Network

Ethernet Cable Setup

• Ethernet cable has four pairs of wires:
  • Orange pair
  • Blue pair
  • Brown pair
  • Green pair
• Connected to a 10BASE-T network.
  • 10BASE-T: Older standard by IEEE, transmits data at 10Mbps (10 million bits per second).
  • Supports other standards:
    • 100BASE-TX: 100Mbps
    • 1000BASE-T (Gigabit Ethernet): 1Gbps
• Usage of Wire Pairs:
  • 1000BASE-T uses all four wire pairs.
  • 10BASE-T and 100BASE-TX use only two wire pairs.
  • Transmission/Reception:
    • Orange pair: Transmitting data
    • Green pair: Receiving data
    • Blue/Brown pairs: Unused

Experiment Setup

• Tool Used: Oscilloscope
  • Connected to orange pair to measure voltage
  • Plots voltage over time
  • Observed voltage fluctuations between +1V and -1V

Voltage and Time Measurement

• Center line on oscilloscope graph: 0 volts
• Each division: 500 millivolts (two divisions = 1 volt)
• Horizontal division: 100 nanoseconds
  • Time Conversion:
    • 1 nanosecond = 10⁻⁹ seconds
    • 100 nanoseconds = 1/10 millionth of a second

Encoding and Decoding Data

• Encoding Used: Manchester Encoding
  • Symbol for Zero: Positive to negative voltage transition
  • Symbol for One: Negative to positive voltage transition
• Expectation: 1 bit every 100 nanoseconds
  • Ethernet speed: 10Mbps = 10 million bits per second
• Decoding Example:
  • Observed voltage transitions to decode bits:
    • 1: Negative to positive
    • 0: Positive to negative
  • Example decoded sequence: 10011001
  • Flipped order: 01100101
  • Conversion:
    • Binary to decimal: 75 (K), 65 (A)
  • ASCII Representation: K and A

Key Takeaway

• Demonstrates how information is encoded and decoded on a real Ethernet link using Manchester encoding.