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