Modern Possibilities of Access and Transport Networks

Vladislav Skorpil

The principle of Time Division Multiplex

The Principle of Pulse Code Modulation (PCM)

The Principle of Delta Modulation (DM) and Adaptivre delta

Modulation (ADM)

Adaptive Diferential PCM - ADPCM

• For signal with no constant midle power, samples are adapted to constant midle power

The basic block diagram for TDM system with digital modulation

• Older type

• Common codec

Transmiter part

Receiver part

The basic block diagram for TDM system with digital modulation

• Modern type

• Individual codec

Quantizing step encoder

Weighting encoder (Bit encoder)

Counting Analogue to Digital Convertor

Tracking A/D Convertor

Parallel A/D Convertor

Compenzating A/D Convertor

Shannon decoder

Shannon decoder response

Shannon Rack decoder

Shannon-Rack Decoder Response

Weighting Decoder (Bit Encoder)

Operational Amplifier

D/A Convertor with weighting resistors

D/A Convertor with cross piece structure of resistor networks

D/A Convertor with current sources

Compandors and non-linear encoders

Compression and expansion characteristics

A-low compression characteristic

Unipolar and Bipolar Signal, Signal NRZ, RZ, TPC, SPC, HDB3,AMI

Code HDB3

• Maximal 3 zeroes in sequence• When the sequence of 4 or more zeroes

exist, then forth one is encoded as the impulse with the same polarity as the previous one

• This bipolarity interruption must be positive after negative and negative after possitive (zero direct current part)

Isolation impulse

Identification of impulse

Decision eye – bipolar signal

Decision eye – unipolar signal, basic noise

Influence of impulse interference

Influence of jitter

Generation of AMI signal

Quantizing distortion

Peak limiting

Time behaviour of sampling

Spectrum of sampling signal – PAM 1st sort

Ideal PAM 1st order (wide of samples approaches to zero

Spestrum of sampling signal -2nd order

Spectrum of PAM 2nd order – wide of samples equals to sampling

periode

• This is the end of my slides to the theme Modern possibilities of access and transport networks

• If you have any questions, you can write e-mail to:

• skorpil@feec.vutbr.cz