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# 5.9 Multiplexing

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### 5.9 Multiplexing

1. 1. Module 5: Digital Techniques and Electronic Instrument Systems 5.9 Multiplexing
2. 2. Multiplexing  Simplex bus:  Data flow always in one way.  Half duplex bus:  Send and receive but not in the same.  Full duplex bus:  Send and receive simultaneously.
3. 3. How can a transmitter send information to more than one receivers through a single wire?  Multiplexing  2 types of multiplexing:  Frequency Division Multiplexing (FDM):  The information intended to for different receivers is differentiated by using different frequencies.  Time Division Multiplexing (TDM):  Each transmitter has its own time-slot at which he can send information.
4. 4. Frequency Division Multiplexing  Each transmitter modulates the data using a “carrier” with a specific frequency.  The receiver obtains the original data using a filter and a demodulator circuit, which removes the “carrier”.  ADSL example:  Voice: 0 – 4KHz  Upstream: 25 – 138KHz.  Downstream: 138 – 1104KHz
5. 5. Frequency Division Multiplexing  Signal in time domain  Signal in time frequency domain  OFDM: Orthogonal carriers overlap, but data can be still recovered by the receiver.   Bandwidth savings!
6. 6. Time Division Multiplexing  Each receiver has a specific timeslot.  Multiplexer receives one bit form each transmitter in order, combines them to a TDM frame and sends them to the channel.  Demultiplexer receives the TDM frame and gives each bit the appropriate receiver in order.
7. 7. Multiplexer  a, b: address lines.  A, B, C & D: transmitters.  Q: Output connected to the channel.  a & b define from which transmitter, data will be forwarded to the output.  Usually a clock is connected to a & b to perform TDM.
8. 8. Demultiplexer  s0, s1: address lines.  DATA: data received from the channel.  Y0,…, Y3: receivers.  s0 & s1 will select to which of receivers the data will be forwarded.  s0 & s1 are usually connected to a clock to perform TDM.
9. 9. Symbols