WHAT IS SDH
- Bit justification is needed in PDH - No would standards available at optical interface in PDH - line rates are not standard - Interfacing problem at multivendor equipment - PDH supports 16E1s and SDH supports 63E1s
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PDH (Plesiochronous Digital Hierarchy) and SDH (Synchronous Digital Hierarchy) are two different systems for transmitting digital signals over telecommunication networks. In PDH, signals are transmitted at fixed multiples of the basic data rate, resulting in slight timing variations between signals. In contrast, SDH uses a standardized synchronous timing system, allowing for more efficient and reliable data transmission with fixed frame structures.
SDH = 3 times of SONET
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== == what is the difference between sdh wan and ethernet wan
SDH and PDH are two digital hierarchies in which different line speeds (e.g. E1, T1, STM1) are categorized.PDH (plesiosynchronous digital hierarchy) was replaced by SDH (synchronous digital hierarchy) due to its drawback in synchronisation where plesio refers to nearlysynchronous.E1, T1 and J1 are generally categorized under PDH. STM1, OC3, STM4, OC12 etc. are categorized under SDH.E1 is used worldwide nowadays in 2G technologies except North America and Japan (who are using T1 and J1 respectively). It is the line speed of 2Mbps. But how this speed comes along? The derivation is as follows.The audio signals were sampled and converted to digital signal at 64kbps, since 1960s for digital transmission of voice calls. When 32 channels (30 assigned for voice channels and 2 channels for framing and signaling), with each having speed of 64kbps are put together (or we call multiplexing), a line speed of E1, i.e. 2Mbps is produced by having 32 x 64kbps = 2.048Mbps.T1 line, which transmits at 1.544 Mbps can be interconnected with E1 for international use.Having 3 different speeds (E1, T1 and J1), PDH was later replaced by SDH in order to standardize the speed, making only 1 standard speed worldwide, which is STM1 having the speed of 155.52Mbps.
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PDH (Plesiochronous Digital Hierarchy) communication has several disadvantages, including its complexity in synchronization, which can lead to difficulties in maintaining data integrity. Additionally, PDH systems are less flexible compared to newer technologies like SDH (Synchronous Digital Hierarchy), making upgrades and integrations with modern networks challenging. The limited bandwidth options and the inability to efficiently handle data traffic also hinder its performance in high-demand scenarios. Lastly, troubleshooting and maintenance can be cumbersome due to the proprietary nature of many PDH systems.
•Plesiochronous Digital Hierarchy (PDH) is the original standard for telephone network, now abandoned in favor of SONET/SDH • Exploits Time Division Multiplexing• Designed to support digital voice channels at 64kb/s•No store and forward: imposes strict synchronization between TX and RX. A "plesio-synchronous" (almost synchronous) solution is adopted• Different standards in US/Europe/JapanSONET:•Synchronous optical networking is a method for communicating digital information using lasers or light emitting diodes (LEDs) over optical fiber.•SONET was introduced to handle large amount of telephone calls and interoperability between equipments of different vendors.•Synchronous networking differs from PDH in that exact rates that are used to transport the data are highly synchronized across the entire network, made possible by atomic clocks.
Ethernet over E1 converter (also called E1 network bridge) is to transmit Ethernet data over E1 network (PDH,SDH network etc). The Ethernet port connect to terminal device,computer,Ethernet switch,Ethernet router etc. The device's E1 port connect to mail network(PDH SDH etc).E1 over IP (TDMOIP) is to transmit the E1 data over ethernet IPnetwork. It transports the legacy E1 data through the existing Ethernet or IP network. The typical application is transmit voice and data over wireless radio network.