PDH和SDH的区别

1.准同步数字体系(PDH)：
PDH 代表 Plesiochronous Digital Hierarchy。它是一种电信网络传输技术，旨在通过大规模数字网络传输大量数据。在 PDH 中，将 2 Mbit/s 信号复用为更高阶的复用信号。交换机站点之间的敷设电缆非常昂贵。它通过增加比特率来增加电缆的流量容量。

2. 同步数字体系(SDH)：
SDH代表Synchronous Digital Hierarchy，它指的是电信中使用的多路复用技术。国际上使用的是同步光网络。据说它是 SONET 的一种变体，被认为等同于 SDH。它的特性建立在高阶复用之上。这些是提供比 PDH(代表 Plesiochronous Digital Hierarchy)更快且价格低廉的网络互连的技术。

PDH和SDH的区别：

S.No.	PDH	SDH
1.	Reference clock is not synchronized throughout the network.	Reference clock is synchronized throughout the network.
2.	There is no synchronization between payload and frame.	There is synchronization between payload and frame.
3.	Its system has different frame structures at different hierarchy levels.	Its system has consistent frame structures throughout the hierarchy.
4.	In this, Physical cross-connections are provided on the same level.	In this, Digital cross-connections are provided at different signal levels.
5.	In this, rates are derived from basic rate of 1.544 Mbps. The maximum capacity is about 566 Mbps.	In this, rates are derived from basic rate of 155.52 Mbps. The maximum up to 40 Gbps rates can be derived from basic rate mentioned.
6.	The implementation cost of PDH is lower.	The implementation cost of SDH is higher.
7.	The multiplying method used in PDH is complex.	The multiplying method used in SDH is simple.
8.	It is incompatible with other signals such as ATM, FDDI, DQDB etc.	It is compatible with other signals such as ATM, FDDI, DQDB etc.
9.	There is no universal standard for PDH.	The universal standard exists for SDH.