Sistemas de comunicación digital

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Sistemas de Comunicación Digital

Msc. Ing. Henry A. Vásquez

Tecnologías de Acceso, Transporte y Conmutación. Tecnología de Transmisiones. Revisión de Sistemas de transporte PDH y SDH.Introducción MPLS en los Sistemas de Comunicaciones.


Sistemas de acceso por cable de pares
Línea Tradicional (POTS)

Sistemas de acceso por cable de pares
Acceso a RDSI (DSL) Sistemas de acceso por cable de pares

4 KHz

25,8 KHz 50 KHz

1,1 MHz frecuencia

Trama MIC europea y americana

Distintas jerarquías PDH a nivel mundial

Jerarquías DigitalesEuropeas (PDH)

Jerarquías Digitales Europeas (PDH)

Jerarquías Digitales Europeas (PDH)

Plesiochronous Digital Hierarchy (PDH)
– Designed in the 1960’s to supersede the analogue telephoneinfrastructure – Limitations of 1960’s technology
• No buffering of frames at high speeds possible
– Thus the term ‘plesi’ (nearly synchronous)

• Bit stuffing used instead of buffering tocompensate for drifts in clocks

– A hierarchical structure was implemented
• To connect millions of low speed customers in a effective manner • ETSI market hierarchy (see ‘Multiplex Mountain’ later)
–2Mb/s to 8Mb/s to 34Mb/s to 140Mb/s

• Once multiplexed, lower order signals can only be extracted by de-multiplexing

Pulse Code Modulation (PCM30)
– There are two PCM systems recommended by theITU
• T1 (24 channel in USA, Canada and Japan) • E1 (30 channel in Europe and most of the world)

– The focus of the following slides will be the E1 variant of PCM
• Also known as PCM30 Generation of the PCM30 Signal
The conversion of analogue signals (speech) into a digital format is generally referred to as Pulse Code Modulation (PCM) This is achieved by a number of processesSampling Quantising


• This is where a “snapshot” of the analogue signal is taken • Also the polarity and amplitude of the signal is determined (8000 times a second...
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