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Multiplexing SDH Signals into STM-1 Frame

Learn about the different types of SDH multiplexing and how 140 Mbps and 34 Mbps signals are multiplexed into the STM-1 frame. Understand the structure and adaptation procedures involved.

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Multiplexing SDH Signals into STM-1 Frame

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  1. Chapter 8 Digital Transmission Systems Part 3 Bahman R. Alyaei

  2. 14 Types of SDH Multiplexing • SDH multiplexing combines low-speed digital signals such as 2, 34, and 140 Mbps signals with required Overhead to form a frame called STM-1. • It also multiplexes ATM and ISDN signals into SDH frame. • SDH is a Byte-Interleaving multiplexing system. Bahman R. Alyaei

  3. Continue… • SDH multiplexing includes two types: • Multiplexing lower-order SDH signals into higher-order signals. • Multiplexing low-rate tributary signals into SDH signal. The goods of different size is analogous to different data rates such as 140 Mbps, 34 Mbps, and 2 Mbps. Bahman R. Alyaei

  4. 14.1 Multiplexing 140 Mbps Signal into STM-1 • First, the 140 Mbps PDH signal (E4) is adapted via bit rate justification into Container level 4 (C-4). • The C-4 has 9 x 260 = 2340 bytes. • The frame rate of C-4 is 8000 frames/Sec, every 125 μS. • The rate of E4 signal after adaptation is 9 x 260 x 8 x 8000 = 149.760 Mbps Bahman R. Alyaei

  5. Continue… • A column of POH is added in front of every C-4 block in order to implement real-time monitoring over the 140 Mbps path signals. • The resulting block is called Virtual Container level 4 (VC-4) with a rate of 9 x 261 x 8 x 8000 = 150.336 Mbps. Bahman R. Alyaei

  6. 1 260 C-4 149.760 Mbps 139.264 Mbps 9 POH 9 261 C-4 150.336 Mbps 149.760 Mbps 9 POH Bahman R. Alyaei

  7. 149.760 Mbps 150.336 Mbps 261 261 VC-4 VC-4 261 9 9 C-4 9 POH = Bahman R. Alyaei

  8. Continue… • The VC-4 is loaded into the information Payload of the STM-1 frame. • Location of the VC-4 within the Payload may float when it loads. • Part of the VC-4 is transmitted in one STM-1 frame and another part in the next frame. • This problem is solved by adding AU-PTR before the VC-4. • It will indicate the start of the VC-4 in the Payload. Bahman R. Alyaei

  9. AU-PTR AU-PTR Payload VC-4 Payload AU-PTR AU-PTR Continue… Bahman R. Alyaei

  10. Continue… • The resulting block (VC-4 + AU-PTR) is called Administrative Unit level 4 (AU-4). • It has the same basic structure of STM-1 frame (9 rows x 270 columns), but only without SOH. • AU-4 = VC-4 + AU-PTR = STM-1 – SOH • To complete the STM-1 frame, the SOH is added to AU-4. Bahman R. Alyaei

  11. 270 VC-4 AU-PTR 9 270 270 SOH 3 AU-4 AU-4 9 9 SOH 5 9 = Bahman R. Alyaei

  12. Bahman R. Alyaei

  13. Continue… • The complete procedure of multiplexing 140 Mbps signal into STM-1 is as follow: • 140 Mbps PDH signal adapted into container C-4. • Add POH to C-4 to form VC-4. • Add AU-PTR to VC-4 to form AU-4. • Add SOH to AU-4 to form STM-1. Bahman R. Alyaei

  14. AU-4 VC-4 C4 C-4 C-4 C-4 POH POH PTR 139.264Mbps STM-1 SOH C-4 POH PTR SOH 155.52Mbps Continue… Bahman R. Alyaei

  15. 14.2 Multiplexing 34 Mbps Signals into STM-1 Frame • Three different 34 Mbps signals can be multiplexed into one STM-1frame as follow: • First, the 34 Mbps PDH signal is adapted viabit rate adaptation into container level 3 (C-3). • The C-3 has 9 raw x 84 column = 756 Bytes. • A column of POH is added in front of every C-3 block in order to implement real-time monitoring over the 34 Mbps signals • The resulting block is called VC-3. Bahman R. Alyaei

  16. 1 84 C-3 48.384 Mbps 34 Mbps 9 POH 9 85 C-3 9 POH 48.96 Mbps 34 Mbps Bahman R. Alyaei

  17. 85 85 VC-3 VC-3 48.96 Mbps 34 Mbps 9 9 85 C-3 9 = POH Bahman R. Alyaei

  18. Continue… • Every VC-3 is assigned a 3-Byte Tributary Unit Pointer (TU-PTR) which allows VC-3 to float in the Payload. • The area in which the VC-3 is allowed to float with the aid of TU-PTR is called Tributary Unit level 3 (TU-3). • TU-PTR contains an address which indicates the start of the VC-3 in the TU-3. • TU-3 frame structure is incomplete, therefore, 6-Bytes pseudo-random data (R) are stuffedto fill the gap of TU-3. • The resulting block is called Tributary Unit Group 3 (TUG3). Bahman R. Alyaei

  19. 85 1 VC-3 3 TU-PTR TU-PTR 9 86 VC-3 3 9 Bahman R. Alyaei

  20. 86 VC-3 3 9 TU-PTR = 86 86 VC-3 TU-3 TU-3 3 3 P T R P T R 9 9 Bahman R. Alyaei

  21. 1 R 6 86 86 TU-3 TU-3 3 3 P T R P T R 9 9 R 49.536 Mbps 34 Mbps 6 Bahman R. Alyaei

  22. 86 86 86 TUG-3 TUG-3 TU-3 3 P T R = 9 9 9 R 6 49.536 Mbps 34 Mbps Bahman R. Alyaei

  23. Continue… • Three TUG-3 blocks are byte interleaved into a container C-4. • Since the resulting structure has only 258 columns (3 x 86), two columns of stuffedbitsare added to complete the C-4 structure. • Finally, C-4 is multiplexed into STM-1 signal which is similar to multiplexing 140 Mbps signal into STM-1. Bahman R. Alyaei

  24. 86 86 86 TUG-3 #2 TUG-3 #3 TUG-3 #1 9 9 9 258 . . . . . . . 9 Bahman R. Alyaei

  25. 86 86 86 TU-3 # 1 TU-3 # 3 TU-3 # 2 3 3 3 P T R P T R P T R 9 9 9 R R R 6 6 6 . . . . . 9 258 Bahman R. Alyaei

  26. 258 9 Incomplete C-4 . . . . . 9 258 Bahman R. Alyaei

  27. 260 258 2 C-4 Incomplete C-4 9 R R 9 260 C-4 149.760 Mbps 34 Mbps 9 Bahman R. Alyaei

  28. Continue… • The complete procedure of multiplexing 34 Mbps signal into STM-1 is as follows: • The 34 Mbps signal is adapted into container C-3. • POH is added to C-4 to form VC-3. • TU-PTR is added to VC-3 to form TU-3. • Stuffing bits is added to TU-3 to fill the gap and form TUG-3. Bahman R. Alyaei

  29. Continue… • By byte interleaving three TUG-3 blocks and adding two columns of stuffing bits, C-3 is formed. • A higher-order POH is added to V-4 to form VC-4. • AU-PTR is added to VC-4 to form AU-4. • Finally, SOH is added to AU-4 to form STM-1 signal. Bahman R. Alyaei

  30. 34 Mbps VC-3 VC-3 C-3 C-3 TU-PTR TU-PTR TU-3 TU-3 = = POH POH Incomplete C-4 TUG-3 TUG-3 TUG-3 = TUG-3 VC-4 C-4 C-4 Incomplete C-4 = = POH PTR SOH AU-4 SOH VC-4 AU-4 = PTR SOH SOH STM-1 SOH AU-4 = 155.52Mbps SOH Bahman R. Alyaei

  31. 3 x TUG3 Interleave + Stuffed bits +Stuffed bits + HO-POH +TU-PTR + POH TU-3 34 Mbps C-4 TUG-3 VC-3 C-3 STM-1 VC-4 AU-4 155.52Mbps +SOH +AU-PTR Bahman R. Alyaei

  32. 14.3 Multiplexing 2 Mbps Signals into STM-1 Frame • 63 E1 signals (2 Mbps) can be multiplexed into one STM-1 signal. • First, the 2Mbps signal is adapted via bit rate adaptation into container level 1, order 2, C-12 • Container C-12 accommodate 34 bytes. • A Multiframe is formed by arranging Four C-12 basic frames side-by-side. Bahman R. Alyaei

  33. Continue… • Since the frequency of E1 is 8000 frames/sec. • Therefore, the frame frequency of C-12 basic frame is also 8000 frames/sec. • Hence, the frequency of the C-12Multiframe is 2000 frames/sec. • When a Multiframe multiplexed into STM-1 frame, they are placed in four successive STM-1 frames, instead of one single frame. Bahman R. Alyaei

  34. Continue… • The Multiframe is used for the convenience of rate adaptation. • If E1 (2 Mbps) signals have standard rate of 2.048 Mbps, each C-12 will accommodate 256 bits (32 bytes) Payload (2.048 Mbps /8000 = 256 bits). • However, when the rate of the E1signals is not standard, the average bit number accommodated into each C-12 is not an integer. • In this case, a Multiframe of four C-12 frames is used to accommodate signals. Bahman R. Alyaei

  35. 4 3 2 Mbps C-12 9 3 C-12 C-12 C-12 C-12 125 μS 125 μS 125 μS 125 μS 500 μS Bahman R. Alyaei

  36. Continue… • To monitor the performance of each 2 Mbpssignal, a Lower-Order Path Overhead (LO-POH) with the size of one byte is added to the notch in the top-left corner of each C-12. • Each Multiframe has four different LO-POHbytes: V5, J2, N2, and K4. • The combination of a C-12 and a LO-POHbyte is called Virtual Container level 1, order 2 (VC-12). Bahman R. Alyaei

  37. V5 J2 N2 K4 C-12 C-12 C-12 C-12 V5 C-12 C-12 J2 C-12 N2 K4 C-12 Bahman R. Alyaei

  38. C-12 V5 C-12 J2 C-12 N2 C-12 K4 Equal VC-12 VC-12 VC-12 VC-12 Bahman R. Alyaei

  39. Continue… • Every Multiframe is assigned a four-byteTributary Unit Pointer (TU-PTR) which allow it to float. • There are four different pointer bytes: V1, V2, V3, and V4. • The first two (V1, V2) contains an address indicating the start of the Multiframe. • Then the information structure changes into Tributary Unit level 1, order 2 (TU-12) with 9 raws x 4 columns. Bahman R. Alyaei

  40. VC-12 VC-12 VC-12 VC-12 V1 V2 V3 V4 VC-12 VC-12 VC-12 VC-12 V1 V2 V3 V4 Bahman R. Alyaei

  41. VC-12 VC-12 VC-12 VC-12 V1 V2 V3 V4 Equal 4 TU-12 TU-12 TU-12 TU-12 9 Bahman R. Alyaei

  42. Continue… • Three TU-12 frames from different Multiframes are byte interleaved to form a Tributary Unit Group 2 (TUG-2). • In the next step, seven TUG-2 frames are byte interleaved in the same manner and add two columns of stuffed bits to form a TUG-3 structure. • And finally, the procedure of multiplexing TUG-3 into STM-1 signal is the same as mentioned before. Bahman R. Alyaei

  43. 4 4 4 V5 V5 V5 9 9 9 V1 V1 V1 12 V5 V5 V5 9 V1 V1 V1 Bahman R. Alyaei

  44. 12 V5 V5 V5 9 V1 V1 V1 Equal 12 TUG-2 9 Bahman R. Alyaei

  45. 12 TUG-2 #1 TUG-2 # 2 TUG-2 # 6 TUG-2 # 7 9 …….. Byte interleaving 84 2 R R Incomplete TUG-3 9 9 86 R R Incomplete TUG-3 9 86 Equal TUG-3 9 Bahman R. Alyaei

  46. Continue.. • The complete procedure of multiplexing of 2 Mbps signal into STM-1 is as follow: • 2 Mbps signal is adapted into C-12. • Add LO-POH to C-12 to form VC-12. • Add TU-PTR to VC-12 to form TU-12. • Multiplex three TU-12 frames to form TUG-2. Bahman R. Alyaei

  47. Continue… • Multiplex seven TUG-2 frames and add two columns of stuffing bits to form TUG-3. • Multiplex three TUG-3 frames and add two columns of stuffing bits to form C-4. • Add HO-POH to C-4 to form VC-4. • Add AU-PTR to VC-4 to form AU-4. • Add SOH to AU-4 to form STM-1. Bahman R. Alyaei

  48. 2 Mbps TUG-2 TU-12 TU-12 TU-12 = = TU-12 C-12 C-12 TUG-2 TUG-3 R R Incomplete TUG-3 R R Incomplete TUG-3 TUG-2 TUG-2 = TUG-2 TUG-2 TUG-2 TUG-2 VC-12 VC-12 TUG-3 C-4 R R Incomplete C-4 TUG-3 POH TUG-3 STM-1 AU-4 VC-4 C-4 = POH 155.52Mbps Bahman R. Alyaei

  49. 3 x TU-12 +TU-PTR + LO-POH 7 x TUG-2 + Stuffing bits TUG-2 TU-12 C-12 2 Mbps +AU-PTR + HO-POH 3 x TUG-3 + Stuffing bits VC-12 VC-4 C-4 TUG-3 AU-4 +SOH STM-1 155.52Mbps Bahman R. Alyaei

  50. ×1 Mapping AUG-64 STM-64 Aligning ×4 Multiplexing ×1 AUG-16 STM-16 Pointer processing ×4 ×1 AUG-4 STM-4 ×4 ×1 ×1 AU-4 VC-4 C-4 AUG-1 STM-1 139264 kbit/s ×3 TU-3 VC-3 C-3 ×1 TUG-3 34368 kbit/s ×7 TUG-2 TU-12 VC-12 C-12 2048 kbit/s ×3 SDH Multiplexing Structure Bahman R. Alyaei

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