1. Chapter 6 Multiplexers and Switching Concepts
Introduction
Used in long distance transmission.

2. Multiplexer and Demultiplexer
Introduction
Multiplexer and Demultiplexer
MUX: combines several low-speed data channels and transmits all of the data on a single high-speed channel
DMUX: the opposite of a multiplexer.

3. Chapter 6 Multiplexers and Switching Concepts
6.1 Types of Multiplexers
TDM (SPM, FPM)
FDM
WDM
CDM.

4. TDM Each input is assigned equal time to transmit its information
6.1 Types of Multiplexers
TDM
Each input is assigned equal time to transmit its information
have idle time.

5. SPM The bandwidth is dynamically allocated to active users.
6.1 Types of Multiplexers
SPM
The bandwidth is dynamically allocated to active users.

6. FPM Use the same method as SPM
6.1 Types of Multiplexers
FPM
Use the same method as SPM
SPM: use store-and-forward technology, perform error detection
FPM: does not use store-and-forward technology , faster than SPM, can’t perform error detection.

7. 6.1 Types of Multiplexers
FDM
Used for analog transmission , several signals transmit on a single line.

8. 6.2 Telephone System Operation
Chapter Multiplexers and Switching Concepts
6.2 Telephone System Operation
Telephone system transmits information in analog signal from a telephone set to the Central Office
PCM method is used in the central switch to convert the human voice to digital signals (Fig 6.7).

9. Chapter 6 Multiplexers and Switching Concepts
6.3 Digitizing the Voice
PAM: the human voice is sampled at the rate of samples per second
PCM: each PAM sample is represented by eight bits (digital signal DS-0)
DS-0: the rate is 8000*8=64Kbps .

10. Chapter 6 Multiplexers and Switching Concepts
6.4 T1 Link
Long distance carriers use TDM to transmit voice signals over high-speed digital lines
One of the application of TDM is the T1 link
A T1 link carries a level-1 digital signal (DS-1) .

11. 6.4 T1 Link
DS-1
A DS-1 is generated by multiplexing 24 voice digital signals (DS-0) .

12. 6.4 T1 Link
DS-2 and T2 Link
The rate of T1 link: 24 DS-0 + 8k overhead = 24*64k+8k=1.544Mbps
A DS-2 is generated by multiplexing 4 DS-1
The rate of T2 link: (24*4=96 DS-0, 168 overhead) 96*64k+168k=6.312M .

13. Chapter 6 Multiplexers and Switching Concepts
To overcome the disadvantage of a fully-connected network, a device called a switch is used to connect stations.

14. Type of switching Circuit Switching Message Switching
6.5 Switching Concepts
Type of switching
Circuit Switching
Message Switching
Packet Switching (Virtual Circuit)
Cell Switching.

15. 6.5 Switching Concepts
Circuit Switching
A physical connection must be established between the source and the destination before transmission of data begins
Only two stations use a communication link at the same time.

16. Message Switching The entire message is transmitted to the switch
6.5 Switching Concepts
Message Switching
The entire message is transmitted to the switch
The switch stores the message, then retransmits it to the next switch or destination
The switch needs to have a large buffer.

17. 6.5 Switching Concepts
Packet switching
Source divides the message into packets, each packet has a sequence number
Each packet send by a different route and may be out of order at the destination
The destination uses the sequence numbers of the packets to put them in proper order.

18. Virtual circuit A type of packet switching
6.5 Switching Concepts
Virtual circuit
A type of packet switching
The routing of the packets is specified before transmission
All packets will be received at the destination in the proper order.

19. Packet switching and Virtual circuit
6.5 Switching Concepts
Packet switching and Virtual circuit

20. Short answer questions
Chapter Multiplexers and Switching Concepts
Short answer questions
17, 20