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03 time division-multiplexing

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03 time division-multiplexing

  1. 1. Time Division Multiplexing Claude Rigault ENST claude.rigault@enst.frClaude Rigault, ENST Communication networks 03 104/10/2004
  2. 2. Time division multiplexing Claude Rigault, ENST Communication networks 03 2 04/10/2004
  3. 3. Time division multiplexing Time Division multiplexing (1) • Time Slot 1 Multiplexer De-multiplexer Claude Rigault, ENST Communication networks 03 3 04/10/2004
  4. 4. Time division multiplexing Time Division multiplexing (2) • Time Slot 2 Multiplexer De-multiplexer Claude Rigault, ENST Communication networks 03 4 04/10/2004
  5. 5. Time division multiplexing Time Division multiplexing (3) • Time Slot 3 Multiplexer De-multiplexer Claude Rigault, ENST Communication networks 03 5 04/10/2004
  6. 6. Time division multiplexing Time Division multiplexing (4) • Time Slot 4 Multiplexer De-multiplexer Claude Rigault, ENST Communication networks 03 6 04/10/2004
  7. 7. Time division multiplexing Frames • Each rotation corresponds to a frame on the multiplex Multiplexer TS3 TS2 TS1 TS0 De-multiplexer Claude Rigault, ENST Communication networks 03 7 04/10/2004
  8. 8. Time division multiplexing Time Division multiplexing • Time division multiplexing is based on peak rate • TDM is adapted to constant rate sources (like voice) C nt = d max Switching Switching network Trunk circuits Trunk circuits network J J J J J J trunks J J Claude Rigault, ENST Communication networks 03 8 04/10/2004
  9. 9. Time division multiplexing Sampling an analog signal • Time division multiplexing requires that only samples of the signal are transmitted. If we have fs rotations /second, the sampling frequency is fs Claude Rigault, ENST Communication networks 03 9 04/10/2004
  10. 10. Time division multiplexing Effect of sampling Energy Fmax Fs-Fmax Fs 2Fs Frequency To recover the original signal, there should be no overlapping : fs- fmax> fmax or : fs> 2fmax Claude Rigault, ENST Communication networks 03 10 04/10/2004
  11. 11. Time division multiplexing PAM modulation Fs Fmax Fs > 2 Fmax Claude Rigault, ENST Communication networks 03 11 04/10/2004
  12. 12. Time division multiplexing Voice spectrum Energy filter 4000 300 800 3400 Frequency (Hz) Cut off frequency of filter is at 4000 Hz ⇒ fs = 8000 Hz Claude Rigault, ENST Communication networks 03 12 04/10/2004
  13. 13. Time division multiplexing PAM and Time division multiplexing • 8000 rotations / second • Advantage of TDM : the filter is the same everywhere • Disadvantage of PAM : analog system ⇒ noise sensitivity Claude Rigault, ENST Communication networks 03 13 04/10/2004
  14. 14. Time division multiplexing PCM and Time division multiplexing PCM link CODER DECODER PAM PAM Claude Rigault, ENST Communication networks 03 14 04/10/2004
  15. 15. Time division multiplexing Voice signal dynamics • The dynamics of the voice signal is very large ⇒ quantization noise gets very large on small signals Claude Rigault, ENST Communication networks 03 15 04/10/2004
  16. 16. Time division multiplexing Quantization noise • Quantization produces « Quantization noise » • A linear measurement scale would result in a lower SNR for small signals than for big signals • What we want is an amplitude independent SNR Claude Rigault, ENST Communication networks 03 16 04/10/2004
  17. 17. Time division multiplexing ‘µ’ Law coding x= v , y= c Code 63 60 50 vmax cmax Log(1+µx) 40 y= Log(1+µ ) 30 20 10 Volts 1,6 µ =255 0 0 0,5 1 1,5 Claude Rigault, ENST Communication networks 03 17 04/10/2004
  18. 18. Time division multiplexing ‘A’ Law coding 140 120 Niveau du signal Code sur 13 bits Code sur 8 bits 100 0 à 25 mV 0 à 63 0 à 33 80 25 à 50 mV 64 à 127 34 à 49 50 à 100 mV 128 à 255 50 à 65 60 0,1 à 0,2 V 256 à 511 66 à 81 40 0,2 à 0,4 V 512 à 1023 82 à 97 20 0,4 à 0,8 V 1024 à 2047 98 à 113 0,8 à 1,6 V 2048 à 4095 114 à 128 0 0 0,5 1 1,5 2 Claude Rigault, ENST Communication networks 03 18 04/10/2004
  19. 19. Time division multiplexing Primary multiplex T1 (T1 carrier) v0 v1 v23 Flag signalisation IT23 IT0 IT1 (24×8)+1=193 bits par trame 193×8000 trames/s =1544 Kbit/s Claude Rigault, ENST Communication networks 03 19 04/10/2004
  20. 20. Time division multiplexing Primary multiplex E1 IT0 IT16 IT1 IT31 Claude Rigault, ENST Communication networks 03 20 04/10/2004
  21. 21. Time division multiplexing E1 frame organization v1 IT0 : x001 1011 ou z1zz zzzz v15 IT16 : supertrame de signalisation v29 v2 v16 v30 IT0 IT16 IT30 IT1 IT15 IT17 IT31 Claude Rigault, ENST Communication networks 03 21 04/10/2004
  22. 22. Time division multiplexing In-band 2 16-2 16-18 15 2 15 1 500 Hz 8000 Hz signalisation 16 0 16-15 16 17 31 16-31 30 31 Claude Rigault, ENST Communication networks 03 22 04/10/2004
  23. 23. Time division multiplexing PCM E1 : superframe v 1-16 v 3-18 v 13-28 v 15-30 v 2-17 v 14-29 IT16-0 IT16-2 IT16-14 IT16-1 IT16-13 IT16-15 Claude Rigault, ENST Communication networks 03 23 04/10/2004
  24. 24. Time division multiplexing The HDB 3 line code • 1 ⇒ Mark, 0 ⇒ Space • Alternate Mark Inversion Clock Data 1 0 1 0 0 1 1 0 Line signal Claude Rigault, ENST Communication networks 03 24 04/10/2004
  25. 25. Time division multiplexing The HDB 3 line code • Coding of sequences of 4 zeros : alternate violations inversion 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 Claude Rigault, ENST Communication networks 03 25 04/10/2004
  26. 26. Time division multiplexing Line Termination circuit 1 HDB 3 Line code circuit 1 MUX LT LT DE-MUX circuit 30 circuit 30 Galvanic insulation Repeater Remote feeding Line code circuit 1 circuit 1 DE-MUX LT LT MUX circuit 30 circuit 30 Claude Rigault, ENST Communication networks 03 26 04/10/2004
  27. 27. Time division multiplexing Asynchronous Transmission • Slips occur after n bits > te/2 1 0 1 1 0 1 0 0 1 0 0 1 0 1 1 0 1 te = fefr n= = 2(te−tr)  1 1  2( fe− fr ) 2 −   fr fe  Claude Rigault, ENST Communication networks 03 27 04/10/2004
  28. 28. Time division multiplexing Asynchronous Transmission • Start and Stop signals required • Caracter Oriented Procedure (COP) Start Te Te Te Te Te Stop Tr Tr Tr Tr Tr Claude Rigault, ENST Communication networks 03 28 04/10/2004
  29. 29. Time division multiplexing Synchronous Transmission • 2 channels required : one for data, one for clock • Bit Oriented Procedure (BOP) SIGNAL HORLOGE 0 1 1 1 1 0 0 0 Claude Rigault, ENST Communication networks 03 29 04/10/2004
  30. 30. Time division multiplexing Mixing clock and data • Line codes such as the Manchester code give a mean to recover the clock, at the expanse of bandwidth Data Line code Clock Line code 0 1 1 1 1 0 0 0 Claude Rigault, ENST Communication networks 03 30 04/10/2004
  31. 31. Time division multiplexing Asynchronous multiplexing signal 1 clock 1 elastic store 1 f1 MUX signal 4 fo clock 4 elastic store 4 f4 Clock out Control ./. 4 Claude Rigault, ENST Communication networks 03 31 04/10/2004
  32. 32. Time division multiplexing Justification signal 1 clock 1 elastic store 1 f1 T j = nTi = 1 fo − fi MUX 4 signal 4 fo clock 4 elastic store 4 f4 Clock out Control ./. 4 Claude Rigault, ENST Communication networks 03 32 04/10/2004
  33. 33. Time division multiplexing European PDH hierarchy 1 E1 1 30 E2 1 64 kbit/s 4 E3 1 2 Mbit/s 4 E4 1 8 Mbit/s 4 E5 565 Mbit/s 34 Mbit/s 4 140 Mbit/s Claude Rigault, ENST Communication networks 03 33 04/10/2004
  34. 34. Time division multiplexing American PDH hierarchy • Caution ! One T3 multiplexes 7 T2 ! 1 1 T1 24 1 T2 56 kbit/s 4 T3 44 Mbit/s 1,5 Mbit/s 7 6 Mbit/s Claude Rigault, ENST Communication networks 03 34 04/10/2004
  35. 35. Time division multiplexing Point to point structure of PDH networks 64 kbit/s 64 Kbit/s 2 Mbit/s 2 Mbit/s E1 E1 8 Mbit/s E2 E2 2 Mbit/s 2 Mbit/s Claude Rigault, ENST Communication networks 03 35 04/10/2004
  36. 36. Time division multiplexing SDH : Adding and Dropping order n order n order n order>n+1 order n order n ADM order n order n order n order n order n order n order n order n order n order n order n The condition : synchronous multiplexing Claude Rigault, ENST Communication networks 03 36 04/10/2004
  37. 37. Time division multiplexing SDH : the STM-1 frame 9 Bytes 261 Bytes Regenerator Section overhead Payload Pointers overhead 9 rows Multiplexer Section overhead STM-1 : Synchronous transfer module Claude Rigault, ENST Communication networks 03 37 04/10/2004
  38. 38. Time division multiplexing Container and Virtual Container P C C + POH → VC O H VC Claude Rigault, ENST Communication networks 03 38 04/10/2004
  39. 39. Time division multiplexing Synchronous multiplexing (high order) • High Order Path (high order multiplex) High order VC pointer Claude Rigault, ENST Communication networks 03 39 04/10/2004
  40. 40. Time division multiplexing Synchronous multiplexing (low order) • Low Order Path (low order multiplex) pointer P Low order VC O H Claude Rigault, ENST Communication networks 03 40 04/10/2004
  41. 41. Time division multiplexing SDH mechanisms • C + POH → VC • Low order VC + pointer → TU • High order VC + pointer → AU Claude Rigault, ENST Communication networks 03 41 04/10/2004
  42. 42. Time division multiplexing SDH tributaries Container Europe US C11 T1 1,5 Mbit/s C12 E1 2Mbit/s 4 C2 T2 6 Mbit/s E3 34Mbit/s 7 C3 T3 44 Mbit/s C4 E4 140Mbit/s Claude Rigault, ENST Communication networks 03 42 04/10/2004
  43. 43. Time division multiplexing Multiplexing paths STM-1 AUG AU-4 VC-4 C-4 3 TUG-3 TU-3 VC-3 3 AU-3 VC-3 C-3 7 7 1 TUG-2 TU-2 VC-2 C-2 3 TU-12 VC-12 C- 4 12 TU-11 VC-11 C-11 Claude Rigault, ENST Communication networks 03 43 04/10/2004

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