Fundamentals of SDH

Giới thiệu tổng quát về hệ thống SDH được sử dụng trong mạng cáp quang

[...]... Capable of transporting future ATM  Capable of operating multi vendor and multi –operator environment SDH Rates  SDH is a transport hierarchy based on multiples of 155.52 Mbit/s  The basic unit of SDH is STM-1  STM-Synchronous Transport Module  Higher rate is an exact multiple of the lower rate therefore the hierarchy is synchronous STM-N Where N =1,4,16 ,64 n is a multiples of four SDH BIT RATES SDH. .. 9x270 NUMBER OF BYTES = 9x270 NUMBER OF BITS = 9x270x8 NUMBER OF BITS = 9x270x8 NUMBER OF BITS / /SECOND = 9x270x8x8000 NUMBER OF BITS SECOND = 9x270x8x8000 =155520000 =155520000 =155.520 Mbps (STM-1) =155.520 Mbps (STM-1) •• BIT RATE OF STM-N = (Nx155.520) Mbps BIT RATE OF STM-N = (Nx155.520) Mbps SDH ACCOMMODATES EXISTING SIGNALS 34M 8M 2M 64K 140M 34M 1 C4 3 C3 M U X 8M 2M S D H 63 1 C12 SDH Multiplexing... with a bit rate of 155.52 Mbit/s is defined in ITU-T Recommendation G.707  It is made up from a byte matrix of 9 rows and 270 columns SDH FRAME REPRESENTATION 9 9 S O H 261 PAY LOAD 270 (MATRIX REPRESENTATION) STM-1 frame structure (contd ) • As indicated in the figure, the STM – n signal is multiples of frames consisting of 9 rows with 270 bytes in each row • The order of transmission of information... capacity of one Byte: 64 kbit/s Frame capacity: 270 x 9 x 8 x 8000 = 155.520 Mbit/s Frame repetition time: 125 µs transmit row by row FRAME REPRESENTATION 1ST ROW 2ND ROW 3RD ROW 9TH ROW 9 261 9 9 9 261 I 9 S O H I 261 261 261 I I PAY LOAD 270 (MATRIX REPRESENTATION) I BIT RATE : STM-N •• •• •• •• •• NUMBER OF ROWS = 9 NUMBER OF ROWS = 9 NUMBER OF COLUMNS = 9+261=270 NUMBER OF COLUMNS = 9+261=270 NUMBER OF. .. The basis of Synchronous Digital Hierarchy (SDH) is synchronous multiplexing - data from multiple tributary sources is byte interleaved MERITS OF SDH  Simplified multiplexing / demultiplexing techniques  Direct access to lower speed tributaries  Enhance Operation , Administration & Maintenance  Easy growth to higher bit rates in steps with evolution of transmission technology  Capable of transporting... of PDH  Specialized equipment required for interwork two hierarchy  Inability to identify individual channels in a higher order bit stream  Insufficient capacity for network management  Higher bit rates are difficult to achieve  Supports only linear topology  no common standards among vendors SDH- Synchronous Digital Hierarchy  SDH is an ITU-T standard for a high capacity telecom network  SDH. .. Multiplexing  The multiplexing principles of SDH follows these terms  Mapping - A process used when tributaries are adapted into Virtual Containers (VCs) by adding justification bits and Path Overhead (POH) information  Aligning - This process takes place when a pointer is included in a Tributary Unit (TU) or an Administrative Unit (AU), to allow the first byte of the Virtual Container to be located... Multiplexing Structure Elements of SDH • • Virtual Container (VC) • Tributary Unit (TU) • Tributary Unit Group (TUG) • Administrative Unit (AU) • Administrative Unit Group (AUG) • 29 Container (C) Synchronous Transport Module - N (STM – N) CONTAINER  Input is PDH  Provides justification for PDH signals  Output is synchronous JUSTIFICATION P D H 2Mb/s CONTAINER 34 BYTES SDH synchronized VIRTUAL CONTAINER... from top to bottom • The first 9 bytes in each row are for information and used by the SDH system itself.This area is divided into 3 parts • Regenerator Section Overhead(RSOH) • Multiplex Section Overhead(MSOH) • Pointers 19 THE TRUCK ANALOGY PAYLOAD OVERHEAD THE TRUCK ANALOGY PAYLOAD OVERHEAD THE TRUCK PAYLOAD OVERHEAD SDH Frame Structure 270 Columns (Bytes) 270 9 1 1 RSOH 3 4 Payload AU Pointer (transport... MB) 4X9 POINTER VC 36 BYTES  4 X9 TU12 (1) 4 X9 TU12 (2) 4 X9 TU12 (3) TUG-2 12 X9 TRIBUTARY UNIT GROUP-2 TU12 CONTAINS -ONE 2 MB TUG-2 CONTAINS THREE 2MB Tributary unit group -3  Homogeneous assembly of identical tributary units Tug-2 (1) Tug-2 (7) TUG-3 TUG-3 CONTAIS 21X2MB VC-4 FORMATION  Virtual container formation TUG-3 TUG-3 VC-4=261 TUG-3 VIRTUAL CONTAINER -4  Virtual container 258C + 1C POH+ . evolution of transmission technology  Capable of transporting existing PDH  Capable of transporting future ATM  Capable of operating multi vendor and multi –operator environment !#  SDH. transport hierarchy based on multiples of 155.52 Mbit/s.  The basic unit of SDH is STM-1  STM-Synchronous Transport Module  Higher rate is an exact multiple of the lower rate therefore the hierarchy. indicated in the gure, the STM – n signal is multiples of frames consisting of 9 rows with 270 bytes in each row • The order of transmission of information is rst from left to right and then