Chapter Objectives After completing this chapter you will

Chapter Objectives After completing this chapter you will be able to: l Describe the various PDH standards l Describe the operation and the frame format, of PDH systems l Describe the SONET standard under the following headings: frame structure, overheads, pointers, multiplexing and the network l Describe the SDH standard under the following headings: frame structure, payload capacity, multiplexing and equipment

Europe and North American PDH Systems

Digital Hierarchy Levels

PDH Multiplexing

Disadvantages of PDH r r r r r Inflexible and expensive Limited management and maintenance capabilities Costly AO&M Low capacity Network status verification problems Network failure High capacity growth Access network problems Vendor incompatibility

Basic Frame Structure of Plesiochronous Digital Signals FAS TB 1. . 4 JSJS JS JS 1 2 3 4 TB 1. . 4 JB JB 1 2 3 4 TB 1. . 4

PDH/SDH and SONET

SONET Hierarchy

STS-1 Frame Format B B B 87 B (B = 8 Bit Byte) Transport Overhead Synchronous Payload Envelope (SPE)

STS-1 Frame Elements 90 Columns 9 Rows Transport Overhead 87 Columns Synchronous Payload Envelope

STS-1 59 Fixed Stuff 30 Fixed Stuff 9 Rows 1 STS POH (9 Bytes) STS-1 Payload Capacity 87 Columns 87

STS-1 SPE 90 Columns Start of STS-1 SPE 9 Rows J 1 STS-1 POH Column STS-1 SPE 125 s 9 Rows 250 s Transport Overhead

STS-N N x 90 Columns 9 Rows (B = 8 Bit Byte) 125 s Transport Overhead STS-N Envelope Capacity

Overhead Layers Path Line Section PTE Path Termination Service (DS 1, DS 3. . ) Mapping and Demapping Line REG Section Termination Section ADM or DCS Line Termination Section REG Section Termination PTE Path Terminating Element REG Regenerator ADM Add-Drop Multiplexer DCS Digital Cross-Connect System PTE Path Termination Service Mapping and Demapping

Section Overhead Line Overhead 1 2 3 4 5 6 7 8 9 1 A 1 B 1 D 1 H 1 B 2 D 4 D 7 D 10 S 1 Z 1 2 A 2 E 1 D 2 H 2 K 1 D 5 D 8 D 11 M 0 or. M 1/Z 2 Transport Overhead 3 JO/ZO F 1 D 3 H 3 K 2 D 6 D 9 D 12 E 2 J 1 B 3 C 2 H 4 G 1 F 2 Z 3 Z 4 Z 5 Path Overhead

Line Overhead Section Overhead Line Overhead 1 2 3 4 5 6 7 8 9 1 A 1 B 1 D 1 H 1 B 2 D 4 D 7 D 10 S 1 Z 1 2 A 2 E 1 D 2 H 2 K 1 D 5 D 8 D 11 M 0 or. M 1/Z 2 Transport Overhead 3 JO/ZO F 1 D 3 H 3 K 2 D 6 D 9 D 12 E 2 J 1 B 3 C 2 H 4 G 1 F 2 Z 3 Z 4 Z 5 Path Overhead

Path Overhead Section Overhead Line Overhead 1 2 3 4 5 6 7 8 9 1 A 1 B 1 D 1 H 1 B 2 D 4 D 7 D 10 S 1 Z 1 2 A 2 E 1 D 2 H 2 K 1 D 5 D 8 D 11 M 0 or. M 1/Z 2 Transport Overhead 3 JO/ZO F 1 D 3 H 3 K 2 D 6 D 9 D 12 E 2 J 1 B 3 C 2 H 4 G 1 F 2 Z 3 Z 4 Z 5 Path Overhead

VT POH BIP-2 1 2 REI-V RFI-V 3 4 Signal Label 5 6 7 RFI-V VT Path Remote Failure Indication REI-V VT Path Remote Error Indication RDI-V VT Path Remote Defect Indication RDI-V 8

Pointer 90 Columns Start of STS-1 SPE 9 Rows H 1 H 2 J 1 STS-1 POH Column STS-1 SPE 125 s 9 Rows 250 s Transport Overhead

VT Superframe and Envelope Capacity Mulitframe Indicator H 4 of previous STS-1 SPE X = undefined bit XXXXXX 00 V 1 VT Envelope Capacity VT 1. 5 VT 2 VT 3 VT 6 26 35 53 107 104 140 212 428 XXXXXX 01 V 2 125 s XXXXXX 10 V 3 250 s XXXXXX 11 V 4 375 s 500 s VT Envelope Capacity Bytes/Superframe

VT SPE and Payload Capacity VT Superframe V 1 VT Payload Capacity VT SPE V 5 V 2 J 2 VT 3 VT 6 25 34 52 106 100 136 208 424 250 s V 4 J 7 VT 2 125 s V 3 J 6 VT 1. 5 375 s 500 s VT Payload Capacity Bytes/VT SPE

Mulitplexing Hierarchy 2. 5 Gbit/s OC-48 622 Mbit/s OC-12 155 Mbit/s OC-3 OC-1 x 4 STS-12 x 4 STS-3 STS-1 x 3 140 Mbit/s SPE 3 c SPE 45 Mbit/s 52 Mbit/s VT Group VT-6 6 Mbit/s VT-2 2 Mbit/s x 3 x 4 VT-1. 5 Mbit/s

Network Configurations Point-to-point Point-to-multipoint Hub Network

SONET/SDH Hierarchies

SDH Frame Structure 125 Microseconds 1 2 3 4 5 6 7 8 9 Each box = 1 byte equivalent to 64 kbit/s capacity 1 SOH 2 3 Pointer 4 5 6 SOH 7 8 9 9 Columns of Overheads 261 Columns of Payload 270 Columns 9 Rows

SDH Bit Rates

SDH Multiplexing Structure VC-4 STM-1 C-4 140 Mbit/s STM-1 SOH VC-4 Pointer SOH C-4 P O H 9 260

SDH Multiplexing Structure STM-N AUG x. N AU 4 C 4 VC 4 x 1 139, 264 kbit/s x 3 TU 3 x 1 TUG 3 Aligning Mapping Multiplexing STM Synchronous Transport Mode AUG Administrative Unit Group AU Administrative Unit TUG Tributary Unit Group TU Tributary Unit VC Virtual Container C Container VC 3 x 7 TU 2 TUG 2 VC 2 x 1 x 3 44, 736 34, 368 kbit/s 6, 312 kbit/s TU 12 VC 12 2, 048 kbit/s VC 11 1, 544 kbit/s

Add-Drop Multiplexer Direct West East 155 Mbit/s Carries 63 x 2 Mbit/s Add-Drop Up to 63 x 2 Mbit/s Tributaries or other rates