The difference between SDH and PDH technology

SDH is the PDH ( Plesiochronous Digital Hierarchy quasi synchronous digital series ) network of a revolution.PDH is asynchronous multiple connection, in any network nodes to access a low-speed tributary signals to the node for multiplexing, code conversion, code speed regulating, timing, scrambler, descrambler and other processes, and PDH only provides electrical interface, on line system and optical interface no unified regulations, unable to achieve global the establishment of the information network.

As the SDH technology is introduced, the transmission system not only has to provide signal propagation in the physical process of the function, but also provides for signal processing, monitoring process function. SDH through multiple container virtual container C and VC as well as the cascade complex frame structure is defined, which can support multiple circuit layers of business, such as various rate asynchronous digital series, DQDB, FDDI, ATM, and in the future may occur in a wide variety of new business. Section overhead in a large number of spare channel enhancement to the SDH network expansibility.

By software control, so that the original PDH artificial change wiring method of achieving cross connection and add-drop multiplexing connection, provides a flexible upper / lower circuit capacity, and make network topology dynamic variable, enhance network adapted to the business development of the flexibility and security, in the larger geometric range circuit protection, height and communication ability to optimize use, so as to enhance the network ability to lay a foundation, just a few seconds to network. Especially SDH self-healing ring, the circuit has failure, rapid recovery of tens of milliseconds. SDH these advantages make it a broadband services digital network based transmission network.

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digital video multiplexer

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