What are Disadvantage of PDH?

• Inflexible and Expensive for Telecommunication Networking
• Inefficient use of transmission capacity (typically 75% fill per stage =>0.75e3=42% fill at 140 Mbps
• Extremely limited network management and maintenance support capabilities
• Higher rates are proprietary

What are the Advantages of SDH?

Advantages of SDH:-

• Worldwide standard
• First standard for bitrates higher than 45/140 Mbps
• Standardised optical interfaces
  simple coding of the electrical signal into the line signal (scrambling)
  Integration of multiplexer and line equipment
• Huge overhead capacity for error monitoring and for management purposes (TMN)
• Direct access to tributary channels
• Only small buffers required --> small group delay figures
•  Provides concept for clock/synchronization, protection switching etc.
•  Suitable as the physical layer of ATM networks