PDH and SDH

Hello friend!

PDH and SDH are two different multiplexing techniques used in telecommunication. Theirmain features are shown below in brief;

PDH: Less synchronizedEasy to operateAbsent of high network management featuresLow data ratesHigh efficiency in allocating bits in the frameMore on manual control

SDH:Fully synchronizedMore software orientedNetwork management features availableHigh data ratesLow efficiency in the allocation of bits in the frameLow user interaction necessaryInteroperability is possible

advantages and disadvantages of SDH.

Advantages: Provision of high data ratesAvailability of advanced network management facilitiesLess user interactionInteroperability is possible

Disadvantages: High costComplex systemsHigh skill of staff required

Thanks!

Dear lan2019! 

SDH：

SDH (synchronous digital hierarchy) is defined according to ITU-T's recommendation. It is a technical system that provides corresponding level information structure for the transmission of digital signals at different speeds, including multiplexing method, mapping method, and related synchronization method.

PDH：

In the system of quasi synchronous digital hierarchy (PDH), high-precision clocks are set in each node of digital communication network, and the signals of these clocks have uniform standard rate. Although the accuracy of each clock is high, there are always some small differences. In order to ensure the quality of communication, the difference between these clocks should not exceed the specified range. Therefore, this synchronization method is not true synchronization strictly, so it is called "quasi synchronization".

Difference:

1. Interface aspect

PDH only has regional electrical interface specification, Bai has no unified world standard. The existing PDH system has three different signal rate levels: European series, North American series, and Japanese series.

2. Reuse mode

SDH can demultiplex the low-speed signal from the tell signal at one time; PDH branch / insert low-speed signal from high-speed signal step by step

3. Operation and maintenance

Compared with SDH, PDH has fewer overhead bytes for OAM in the frame structure of the PDH signal.

4. There is no unified network management interface

Compared with SDH, PDH has no network management function and unified network management interface, which is not conducive to the formation of a unified telecommunications management network.

5. Frequency band utilization

The transmission rate occupied by the PDH signal is lower than that occupied by the SDH signal, that is, the bandwidth occupied by the PDH signal is narrow.

6. The mechanism of pointer adjustment is complex

Compared with PDH, the SDH system has a unique jitter --- the combination jitter caused by pointer adjustment.

Thanks!