31-07-2014, 10:17 AM
Digital Communication
Systems
[attachment=66397]
Topics in Digital Communications
zDigital communication system
advantages and disadvantages
zDigital communication system
classification
zDigitization of analog signals
zDigital transmission systems
zData communication systems
zIntegrated Services Digital Network
and other advanced digital
communication systems
Digital Communication advantages
zReliable communication; less sensitivity to changes in
environmental conditions (temperature, etc.)
z
E
asy multiplexing
zEasy signaling
Hook status, address digits, call progress information
zVoice and data integration
zEasy processing like encryption and compression
zEasy system performance monitoring
QOS monitoring
zIntegration of transmission and switching
zSignal regeneration, operation at low SNR, superior performance
zIntegration of services leading to ISDN
Increased bandwidth
64 KB for a 4 KHz channel, without compression (However,
less with compression)
zNeed for precision timing
Bit, character, frame synchronization needed
zAnalogue to Digital and Digital to Analogue conversions
Very often non-linear ADC and DAC used, some
performance degradation
zHigher complexity
ISDN principles
Ê ISDN is based on concepts developed for telephony. Therefore,
evolutionary changes
Ê Transition from the present network to ISDN may require about
one decade.
Ê End-to-end digital connectivity to be obtained using digital
transmission, TDM switching and or SDM switching.
Ê Present ITU standards part of new standards
Ê In early development of ISDN interim measures needed for
interfacing with present networks
Systems
[attachment=66397]
Topics in Digital Communications
zDigital communication system
advantages and disadvantages
zDigital communication system
classification
zDigitization of analog signals
zDigital transmission systems
zData communication systems
zIntegrated Services Digital Network
and other advanced digital
communication systems
Digital Communication advantages
zReliable communication; less sensitivity to changes in
environmental conditions (temperature, etc.)
z
E
asy multiplexing
zEasy signaling
Hook status, address digits, call progress information
zVoice and data integration
zEasy processing like encryption and compression
zEasy system performance monitoring
QOS monitoring
zIntegration of transmission and switching
zSignal regeneration, operation at low SNR, superior performance
zIntegration of services leading to ISDN
Increased bandwidth
64 KB for a 4 KHz channel, without compression (However,
less with compression)
zNeed for precision timing
Bit, character, frame synchronization needed
zAnalogue to Digital and Digital to Analogue conversions
Very often non-linear ADC and DAC used, some
performance degradation
zHigher complexity
ISDN principles
Ê ISDN is based on concepts developed for telephony. Therefore,
evolutionary changes
Ê Transition from the present network to ISDN may require about
one decade.
Ê End-to-end digital connectivity to be obtained using digital
transmission, TDM switching and or SDM switching.
Ê Present ITU standards part of new standards
Ê In early development of ISDN interim measures needed for
interfacing with present networks