Data communication formulas on one card

Lesson notes

Key points

• Bit rate = 2B log₂L: Nyquist gives maximum bit rate on a noiseless channel with L signal levels.
• C = B log₂(1+SNR): Shannon capacity sets the ceiling for a noisy channel, using SNR as a ratio.
• SNR_dB = 10 log₁₀SNR: Convert decibels back to a plain ratio before plugging into Shannon's formula.
• Prop. delay = d ÷ v: Propagation delay is distance divided by signal speed in the medium.
• Trans. delay = L ÷ R: Transmission delay is frame length in bits divided by the link's bit rate.
• Baud vs bit rate: Bit rate equals baud rate times bits carried per signal element.

Takeaway: Convert dB to ratio, and never mix propagation with transmission delay.