Course Name: Mobile CommunicationCourse No.: ECE 4207

Topics:• T-1 Carrier System• E-1 Carrier System• PDH & SDH Transmission Technology

Digital Carrier Standards

T-1 Carrier System

T-1 Frame Structure

T-Carrier Digital Multiplexing Hierarchy

T-Carrier Digital Multiplexing Hierarchy

E-1 Carrier System

E-Carrier Digital Multiplexing Hierarchy

E-Carrier Digital Multiplexing Hierarchy

Digital Carrier Comparison

PDH

SDH

SDH = Synchronous Digital Hierarchy.

Multiplexing Standard for Optical Fiber

Transmission.

Use Single Master Clock for Synchronize.

Bit Stream can be added or extracted directly.

Basic Transmission Rate = 155.52 Mbps.

Goals of SDH

Advantages of SDH over PDH

Universal Standard Interfaces:

I. PDH provides no standard electrical or optical interfaces.

II. In PDH, it becomes difficult to interconnect different equipments from different vendors.

III. SDH provides a standard for electrical and optical interfaces to add different equipments from different vendors.

Advantages of SDH over PDH

Multiplexing Method

In PDH, adding/dropping low-rate signals from high-rate signals must be conducted level by level.

Advantages of SDH over PDH

Multiplexing Method

• Low-rate SDH signals are multiplexed into the frame structure of high-rate SDH signals via byte interleaved method.

• Location of low-rate SDH signals are fixed, regular, and predictable in the frame of high-rate SDH signals.

Advantages of SDH over PDH

Operation, Administration, and Maintenance

I. Few Overhead bytes are added to PDH signals for OAM purpose.

II. In SDH, about 1/20 of the total bytes in a frame are used for OAM purpose.

Advantages of SDH over PDH

Compatibility

SDH has high compatibility with PDH, ATM, FDDI, DQDB system.

Disadvantages of SDH

Low Bandwidth Utilization Ratio

To transmit, the same amount of valid information, PDH signals occupy less frequency bandwidth than SDH signals.

Disadvantages of SDH

Complex Mechanism of Pointer Justification

I. Pointer constantly indicates the location of low-rate signals so that they can be demultiplexed easily.

II. This pointer function increases the complexity of the system.

Disadvantages of SDH

Influence of Excessive use of Software n System Security

SDH Frame Structure (STM-1)

SDH Frame Structure (STM-N)

Data Rate of STM-1

Total bits in one Frame=9×270×8 bits

Frame Period= 125 µs

Data Rate = 19440/125 µs

= 155.52 Mbps