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Multiplexing
CEN 220/CIS 192 Advanced Data Communications and Networking
Data and Computer Communications, W. Stallings 9/...
2
Multiplexing
“It was impossible to get a conversation going,
everybody was talking too much.”
—Yogi Berra
3
Multiplexing
multiple links on 1 physical line
common on long-haul, high capacity, links
have FDM, TDM, STDM alternatives
4
Frequency Division Multiplexing (FDM)
5
FDM
System
Overview
6
FDM Voiceband Example
7
Analog Carrier Systems
long-distance links use an FDM hierarchy
AT&T (USA) and ITU-T (International) variants
Group

12...
8
North American and International FDM
Carrier Standards
9
Wavelength Division Multiplexing (WDM)
10
ITU WDM Channel Spacing (G.692)
11
Synchronous Time Division Multiplexing
12
TDM System
Overview
13
TDM Link Control
no headers and trailers
data link control protocols not needed
flow control
 data rate of multiplexed...
14
Data Link Control on TDM
15
Framing
no flag or SYNC chars bracketing TDM frames
must still provide synchronizing mechanism between
source and desti...
16
Pulse Stuffing
– problem of synchronizing various data sources
– variation among clocks could cause loss of
synchroniza...
17
TDM Example
18
Digital Carrier Systems
19
North American and International
TDM Carrier Standards
20
DS-1 Transmission Format
21
SONET/SDH
Synchronous Optical Network (ANSI)
Synchronous Digital Hierarchy (ITU-T)
high speed capability of optical fib...
22
SONET/SDH Signal Hierarchy
23
SONET Frame Format
24
Statistical TDM
25
Statistical TDM Frame Format
26
Single-Server Queues with Constant Service Times
and Poisson (Random) Arrivals
27
Cable Modems
– dedicate two cable TV channels to data transfer
– each channel shared by number of subscribers using
sta...
28
Cable Spectrum Division
To support both cable television programming and data
channels, the cable spectrum is divided i...
29
Cable Modem Scheme
30
Asymmetrical Digital Subscriber Line (ADSL)
link between subscriber and network
uses currently installed twisted pair c...
31
ADSL Channel Configuration
32
Discrete Multitone (DMT)
multiple carrier signals at different frequencies
divide into 4 kHz subchannels
test and use s...
33
DMT Transmitter
34
Broadband – Customer Side
DSL link is between provider and customer
a splitter allows simultaneous telephone and data
s...
35
Broadband – Provider Side
a splitter separates telephone from Internet
voice traffic is connected to public switched
te...
36
xDSL
high data rate DSL (HDSL)

2B1Q coding on dual twisted pairs

up to 2Mbps over 3.7km
single line DSL

2B1Q codi...
37
Comparison of xDSL Alternatives
38
Summary
Multiplexing multiple channels on single link
FDM

analog carrier systems

wavelength division multiplexing
T...
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Chapter 8 - Multiplexing 9e

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Chapter 8 - Multiplexing 9e

  1. 1. Multiplexing CEN 220/CIS 192 Advanced Data Communications and Networking Data and Computer Communications, W. Stallings 9/E, Chapter 8
  2. 2. 2 Multiplexing “It was impossible to get a conversation going, everybody was talking too much.” —Yogi Berra
  3. 3. 3 Multiplexing multiple links on 1 physical line common on long-haul, high capacity, links have FDM, TDM, STDM alternatives
  4. 4. 4 Frequency Division Multiplexing (FDM)
  5. 5. 5 FDM System Overview
  6. 6. 6 FDM Voiceband Example
  7. 7. 7 Analog Carrier Systems long-distance links use an FDM hierarchy AT&T (USA) and ITU-T (International) variants Group  12 voice channels (4 kHz each) = 48 kHz  Range 60 kHz to 108 kHz Supergroup  FDM of 5 group signals supports 60 channels  carriers between 420 kHz and 612 kHz Mastergroup  FDM of 10 supergroups supports 600 channels original signal can be modulated many times
  8. 8. 8 North American and International FDM Carrier Standards
  9. 9. 9 Wavelength Division Multiplexing (WDM)
  10. 10. 10 ITU WDM Channel Spacing (G.692)
  11. 11. 11 Synchronous Time Division Multiplexing
  12. 12. 12 TDM System Overview
  13. 13. 13 TDM Link Control no headers and trailers data link control protocols not needed flow control  data rate of multiplexed line is fixed  if one channel receiver can not receive data, the others must carry on  corresponding source must be quenched  leaving empty slots error control  errors detected & handled on individual channel
  14. 14. 14 Data Link Control on TDM
  15. 15. 15 Framing no flag or SYNC chars bracketing TDM frames must still provide synchronizing mechanism between source and destination clocks added digit framing is most common  one control bit added to each TDM frame  identifiable bit pattern used as control channel  alternating pattern 101010…unlikely to be sustained on a data channel  receivers compare incoming bits of frame position to the expected pattern
  16. 16. 16 Pulse Stuffing – problem of synchronizing various data sources – variation among clocks could cause loss of synchronization – issue of data rates from different sources not related by a simple rational number
  17. 17. 17 TDM Example
  18. 18. 18 Digital Carrier Systems
  19. 19. 19 North American and International TDM Carrier Standards
  20. 20. 20 DS-1 Transmission Format
  21. 21. 21 SONET/SDH Synchronous Optical Network (ANSI) Synchronous Digital Hierarchy (ITU-T) high speed capability of optical fiber defines hierarchy of signal rates – Synchronous Transport Signal level 1 (STS-1) or – Optical Carrier level 1 (OC-1) is 51.84 Mbps – carries one DS-3 or multiple (DS1 DS1C DS2) plus ITU-T rates (e.g., 2.048 Mbps) – multiple STS-1 combine into STS-N signal – ITU-T lowest rate is 155.52 Mbps (STM-1)
  22. 22. 22 SONET/SDH Signal Hierarchy
  23. 23. 23 SONET Frame Format
  24. 24. 24 Statistical TDM
  25. 25. 25 Statistical TDM Frame Format
  26. 26. 26 Single-Server Queues with Constant Service Times and Poisson (Random) Arrivals
  27. 27. 27 Cable Modems – dedicate two cable TV channels to data transfer – each channel shared by number of subscribers using statistical TDM
  28. 28. 28 Cable Spectrum Division To support both cable television programming and data channels, the cable spectrum is divided in to three ranges:  user-to-network data (upstream): 5 - 40 MHz  television delivery (downstream): 50 - 550 MHz  network to user data (downstream): 550 - 750 MHz
  29. 29. 29 Cable Modem Scheme
  30. 30. 30 Asymmetrical Digital Subscriber Line (ADSL) link between subscriber and network uses currently installed twisted pair cable is Asymmetric - bigger downstream than up uses Frequency Division Multiplexing  reserve lowest 25 kHz for voice (POTS)  uses echo cancellation or FDM to give two bands has a range of up to 5.5 km
  31. 31. 31 ADSL Channel Configuration
  32. 32. 32 Discrete Multitone (DMT) multiple carrier signals at different frequencies divide into 4 kHz subchannels test and use subchannels with better SNR 256 downstream subchannels at 4 kHz (60 kbps)  in theory 15.36 Mbps, in practice 1.5-9 Mbps
  33. 33. 33 DMT Transmitter
  34. 34. 34 Broadband – Customer Side DSL link is between provider and customer a splitter allows simultaneous telephone and data service data services use a DSL modem  sometimes referred to as G.DMT modem DSL data signal can be divided into a video stream and a data stream  the data stream connects the modem to a router which enables a customer to support a wireless local area network
  35. 35. 35 Broadband – Provider Side a splitter separates telephone from Internet voice traffic is connected to public switched telephone network (PSTN) data traffic connects to a DSL multiplexer (DSLAM) which multiplexes multiple customer DSL connections to a single high-speed ATM line. ATM line connects ATM switches to a router which provides entry to the Internet
  36. 36. 36 xDSL high data rate DSL (HDSL)  2B1Q coding on dual twisted pairs  up to 2Mbps over 3.7km single line DSL  2B1Q coding on single twisted pair (residential) with echo cancelling  up to 2Mbps over 3.7km very high data rate DSL  DMT/QAM for very high data rates  separate bands for separate services
  37. 37. 37 Comparison of xDSL Alternatives
  38. 38. 38 Summary Multiplexing multiple channels on single link FDM  analog carrier systems  wavelength division multiplexing TDM  TDM link control  pulse stuffing statistical TDM broadband ADSL and xDSL

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