Multiplexing

Frequency Division Multiplexing

The bandwidth of a single physical medium is divided into a number of smaller, independent frequency channels.

Time Division Multiplexing

All signals operate with the same frequency (bandwidth) at different times.

Code Division Multiplexing

Assign a m-bit chip to each user, and all chips are orthogonal(正交).

• For example, m = 8 and S = 00011011.
  • When user transmit bit 1, send original chip.
  • When user transmit bit 0, send reverse code S’ 11100100.

  00011011 ⇒ (-1 -1 -1 +1 +1 -1 +1 +1)

  $1/m·S·S=1$

  $1/m·S·S’=-1$

  When receiver use S to calculate received data:

  • Result 0 ⇒ data from other users
  • Result 1 ⇒ sender sends bit 1
  • Result -1 ⇒ sender sends bit 0