Line coding and bit time

Data

Link
Playback

Spacebar: play or pause. R: reset. Duration refers to 1 Mbps; the cursor always advances at the same speed, so at higher rates the frame finishes sooner.

+V −V

Bit time 1/R

Bits L

Transmission L/R

Sending

–

Each bit occupies the link for a fixed time, the bit time. Transmission delay is the sum of those intervals: changing the line code changes the waveform, changing R narrows each bit. The on-screen width is not proportional to real time (1 Gbps is a thousand times faster than 1 Mbps, not four); the cards give the exact values.

About this visualization

Shows the waveform of a 2 to 24 bit sequence (typed in or random) encoded as NRZ-L, NRZ-I or Manchester, together with the bit time T_b = 1/R. The student changes the link rate R, from 1 Mbps to 1 Gbps on a logarithmic scale, and plays back the transmission with a cursor that highlights the bit currently being sent. The cards give T_b, the number of bits L and the transmission delay L/R. The key idea is that every bit occupies the link for a fixed time, and the transmission delay is the sum of those intervals.

Concepts: bit time, transmission rate, transmission delay, line coding, NRZ-L, NRZ-I, Manchester, waveform.

Formulas:

Network Architecture I, Session 1.1 · Enrique de la Hoz, University of Alcalá · License CC BY-SA 4.0 · Source and catalogue on GitHub · DOI 10.5281/zenodo.23285664