1 / 48

COE 341: Data & Computer Communications (T081) Dr. Marwan Abu-Amara

COE 341: Data & Computer Communications (T081) Dr. Marwan Abu-Amara. Chapter 8: Multiplexing. Lecture Contents . Introduction Multiplexing Types FDM Synchronous TDM Statistical TDM ADSL. Introduction.

teenie
Download Presentation

COE 341: Data & Computer Communications (T081) Dr. Marwan Abu-Amara

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. COE 341: Data & Computer Communications (T081)Dr. Marwan Abu-Amara Chapter 8: Multiplexing

  2. Lecture Contents • Introduction • Multiplexing Types • FDM • Synchronous TDM • Statistical TDM • ADSL COE 341 – Dr. Marwan Abu-Amara

  3. Introduction • Multiplexing: A generic term used when more than one application or connection share the capacity of one link • Objective is to achieve better utilization of resources COE 341 – Dr. Marwan Abu-Amara

  4. Multiplexing Types COE 341 – Dr. Marwan Abu-Amara

  5. Frequency Division Multiplexing (FDM) COE 341 – Dr. Marwan Abu-Amara

  6. FDM • Useful bandwidth of medium exceeds required bandwidth of channel • Each signal is modulated to a different carrier frequency • Carrier frequencies separated so signals do not overlap (guard bands) • e.g. broadcast radio • Channel allocated even if no data COE 341 – Dr. Marwan Abu-Amara

  7. FDM COE 341 – Dr. Marwan Abu-Amara

  8. FDM Multiplexing Process: Time-Domain View COE 341 – Dr. Marwan Abu-Amara

  9. FDM Multiplexing Process: Frequency-Domain View COE 341 – Dr. Marwan Abu-Amara

  10. FDM De-Multiplexing Process: Time-Domain View COE 341 – Dr. Marwan Abu-Amara

  11. FDM De-Multiplexing Process: Frequency-Domain View COE 341 – Dr. Marwan Abu-Amara

  12. FDM System – Transmitter COE 341 – Dr. Marwan Abu-Amara

  13. FDM System – Receiver COE 341 – Dr. Marwan Abu-Amara

  14. FDM of Three Voiceband Signals COE 341 – Dr. Marwan Abu-Amara

  15. Analog Carrier Systems • Devised by AT&T (USA) • Hierarchy of FDM schemes • Group • 12 voice channels (4kHz each) = 48kHz • Range 60kHz to 108kHz • Supergroup • 60 channels • FDM of 5 group signals on carriers between 420kHz and 612 kHz • Master group • 10 supergroups • Jumbo group • 6 master groups COE 341 – Dr. Marwan Abu-Amara

  16. Analog FDM Hierarchy COE 341 – Dr. Marwan Abu-Amara

  17. Time Division Multiplexing (TDM) COE 341 – Dr. Marwan Abu-Amara

  18. TDM • Data rate of medium exceeds data rate of digital signal to be transmitted • Multiple digital signals interleaved in time • May be at bit level or blocks • Time slots preassigned to sources and fixed • Time slots allocated even if no data • Time slots do not have to be evenly distributed amongst sources COE 341 – Dr. Marwan Abu-Amara

  19. Time Division Multiplexing COE 341 – Dr. Marwan Abu-Amara

  20. TDM Frames COE 341 – Dr. Marwan Abu-Amara

  21. TDM System – Transmitter COE 341 – Dr. Marwan Abu-Amara

  22. TDM System – Receiver COE 341 – Dr. Marwan Abu-Amara

  23. TDM Link Control • No headers and trailers • Data link control protocols not needed for MUXed line • Flow control • Data rate of multiplexed line is fixed • If one channel receiver can not receive data, the others must carry on • The corresponding source must be halted • This leaves empty slots • Error control • Errors are detected and handled by individual channel systems COE 341 – Dr. Marwan Abu-Amara

  24. Data Link Control on TDM COE 341 – Dr. Marwan Abu-Amara

  25. Framing • So far, no flag or SYNC characters bracketing TDM frames on the MUXed line • Must provide frame synchronizing mechanism • Added digit framing • One control bit added to each TDM frame • Looks like another channel - “control channel” • Identifiable bit pattern used on control channel • e.g. alternating 01010101…unlikely on a data channel • Can compare incoming bit patterns on each channel with sync pattern COE 341 – Dr. Marwan Abu-Amara

  26. Framing in TDM MUXed frame Four data channels C 1 2 3 4 C 1 2 3 4 C 1 0 0 1 ….. Control Channel, C 010101…. ….. A data Channel Unlikelyto have 010101…. over successive frames • RX knows the size of the MUXed frame • It can check each frame bit frame-to-frame for the special pattern until it finds it • Once the position of the control channel is established, RX knows where the channel • sequence starts and sync is established with TX COE 341 – Dr. Marwan Abu-Amara

  27. Pulse Stuffing • Problem - Synchronizing data sources • Clocks in different sources drifting • Data rates from different sources not related by simple rational number • Solution - Pulse Stuffing • Outgoing data rate (excluding framing bits) higher than sum of incoming rates • Stuff extra dummy bits or pulses into each incoming signal until it matches local clock • Stuffed pulses inserted at fixed locations in frame and removed at demultiplexer COE 341 – Dr. Marwan Abu-Amara

  28. TDM of Analog and Digital Sources COE 341 – Dr. Marwan Abu-Amara

  29. Digital Carrier Systems • Hierarchy of TDM (similar to FDM) • USA/Canada/Japan use one system • ITU-T use a similar (but different) system • US system based on DS-1 format • Multiplexes 24 PCM voice channels • Each frame has 8 bits per channel plus one framing bit • 193 bits per frame (24 ch.  8 bits per ch. + 1 framing bit = 193 bits per frame) COE 341 – Dr. Marwan Abu-Amara

  30. DS Signals COE 341 – Dr. Marwan Abu-Amara

  31. DS & T Lines Rates COE 341 – Dr. Marwan Abu-Amara

  32. Digital Carrier Systems • For voice each channel contains one word of digitized data (PCM, 8000 samples per second) • Data rate 8000 x 193 = 1.544Mbps • Five out of six frames have 8 bit PCM samples • Sixth frame is 7 bit PCM word plus signaling bit • Signaling bits form stream for each channel containing control and routing info • Same format for digital data • 23 channels of data • 7 bits per frame plus indicator bit for data or systems control • 24th channel is sync • DS-1 can carry mixed voice and data signals COE 341 – Dr. Marwan Abu-Amara

  33. DS-1 Transmission Format (8000 x 7 bits = 56 kbps) COE 341 – Dr. Marwan Abu-Amara

  34. T1 Due to 1 framing bit Per frame COE 341 – Dr. Marwan Abu-Amara

  35. T1 Frames COE 341 – Dr. Marwan Abu-Amara

  36. E1 COE 341 – Dr. Marwan Abu-Amara

  37. Mixed Data • DS-1 can carry mixed voice and data signals • 24 channels used • No sync byte • Can also interleave DS-1 channels • DS-2 is four DS-1 giving 6.312Mbps COE 341 – Dr. Marwan Abu-Amara

  38. SONET/SDH • Synchronous Optical Network (ANSI) • Synchronous Digital Hierarchy (ITU-T) • Compatible • Utilize the large channel capacity of optical fibers • Signal Hierarchy • Synchronous Transport Signal level 1 (STS-1) or Optical Carrier level 1 (OC-1) • Frame of 810 octets every 125 ms: 51.84Mbps • Carry DS-3 or group of lower rate signals (DS1, DS1C, DS2) plus ITU-T rates (e.g. 2.048Mbps) • Multiple STS-1 combined into STS-N signal • ITU-T lowest rate is 155.52Mbps (STM-1) COE 341 – Dr. Marwan Abu-Amara

  39. SONET/SDH Frame Format COE 341 – Dr. Marwan Abu-Amara

  40. Statistical TDM • In Synchronous TDM many slots are wasted • Statistical TDM allocates time slots dynamically based on demand • Multiplexer scans input lines and collects data until frame is full • Data rate on line lower than aggregate rates of input lines COE 341 – Dr. Marwan Abu-Amara

  41. Statistical TDM COE 341 – Dr. Marwan Abu-Amara

  42. Statistical TDM Frame Formats COE 341 – Dr. Marwan Abu-Amara

  43. Performance • Output data rate less than aggregate input rates • May cause problems during peak periods • Buffer inputs • Keep buffer size to minimum to reduce delay COE 341 – Dr. Marwan Abu-Amara

  44. Buffer Size and Delay • Increasing utilization increases • Buffer size • delay • Utilization > 0.8 is undesirable COE 341 – Dr. Marwan Abu-Amara

  45. ADSL • ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses • The existing local loops can handle bandwidths up to 1.1 MHz • ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line • Use the following as a rule of thumb • XYZ km  XYZ Mbps • XYZ km  XYZ Mbps COE 341 – Dr. Marwan Abu-Amara

  46. ADSL Hardware COE 341 – Dr. Marwan Abu-Amara

  47. ADSL Frequency Bands COE 341 – Dr. Marwan Abu-Amara

  48. DMT COE 341 – Dr. Marwan Abu-Amara

More Related