This document discusses multiplexing techniques used in mobile computing. It describes four types of multiplexing: frequency division multiplexing (FDM), time division multiplexing (TDM), code division multiplexing (CDM), and space division multiplexing (SDM). For each type, it provides details on how the technique works and its advantages and disadvantages. FDM uses different frequencies to transmit multiple signals simultaneously. TDM divides a signal into time slots to share a frequency. CDM assigns unique codes to signals sharing the same frequency. SDM splits a channel across physical locations.