(collection of schemes to transmit multiple signals simultaneously)
- FDM - Frequency-Division Multiplexing - analog, modulated to a fixed frequency band, channel.
- TDM - Time-Division Multiplexing - same frequency in alternating time slices, each channel makes full use of the bandwidth, GSM and D-AMPS use TDM
- CDM - Code-Division Multiplexing - makes better use of frequency than FDM and TDM. Signals are transmitted on the same frequency and same time, but have a unique code to identify itself. CDMA use CDM, of course.