01-Tw2103eu01 Eg0001 Digital Transmission

8/13/2019 01-Tw2103eu01 Eg0001 Digital Transmission

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Digital Transmission Siemens

1 Digital Transmission

Contents Pages

1 objectives 22 Individual Connections 33 Frequency-Division Multile! "FDM# $$ Time-Division Multile! "TDM# %& Summary '

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Siemens Digital Transmission

1.1 Objectives

+on comletion o t.is c.ater/ you 0ill .ave an overvie0 o .o0 multile lines areused or long-range communications

ou 0ill be able to

*!lain t.e rincile o Frequency-Division Multile! "FDM# and Time-Division

Multile! "TDM#

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1.2 Individual Connections

In a tele.one net0or/ every subscriber is normally connected to t.e e!c.ange"*!c.# via .is o0n air o 0ires

4t t.e beginning o tele.ony/ t.ere 0as a searate 0ire air or every connectionalso bet0een t.e e!c.anges

Fig. 1

Due to t.e .ig. costs o t.e net0or/ eorts 0ere made at an early stage to use atleast t.ose lines required or long-range communication in a multile 0ay T.is ledto t.e introduction o t.e frequency-division multile!ing "FDM#

Fig. 2

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Frequency-Division ulti!le" #FD$

Seec. transmission only requires a narro0 requency band T.e requency band"seec. band# used in tele.ony is limited to 3)) to 3$)) 56

Fig. 3

T.e seec. band does not mae use o t.e entire band0idt. o a transmission line

To mae use o t.e ull band0idt./ a 0ide requency band is subdivided intonarro0er/ consecutive sub-bands o $ 756 *ac. sub-band transmits one call So in

our e!amle/ 12 calls can be transmitted at t.e same time via t.e requency band

Fig $

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Since t.e tec.nical e!ecution in t.e lo0er requency band is

rat.er diicult/ t.e irst sub-band is located at %) 756 T.erequency range belo0 t.is value is not used

Fig &

8y means o modulation 0it. various sinusoidal 0aves "carriers#/ t.e individualseec. bands are translated into t.e sub-bands and t.en transmitted T.is rocessis no0n as carrier transmission

4ter t.e demodulation on t.e receiver side/ t.e individual seec. bands are againavailable in t.eir original orm

Fig. 6

T.is rocedure allo0s t.e simultaneous transmission o several seec. bands viaone line

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Fig. 7

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1.% Time-Division ulti!le" #TD$

T.e rincile o time-division multile! is based on t.e t.eory t.at t.e comlete0aveorm is not required or transmitting signals suc. as t.ose encountered intele.ony

Fig. 8

It is suicient to samle t.e 0aveorm at regular intervals and to transmit only t.esesamles

Fig. 9

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9n t.e receiver side/ t.e original 0aveorm can be restored rom t.ese samles

Fig. 10

:elatively large intervals occur bet0een eac. samle T.ese intervals can be usedor transmitting ot.er ulse amlitude modulation ";4M# signals/ ie t.e samles oseveral dierent tele.one signals can be transmitted one ater t.e ot.er inreeated cycles

T.e samles are transmitted as ulses 0it. dierent amlitudes "analog#T.is rocedure is no0n as pulse amlitude modulation "PAM#

Fig. 11

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Due to t.e digital structure o t.e message/ ;CM signals are muc. less sensitive tointererences t.an analog signals "eg ;4M signals# 9n t.e receiver side/regenerative reeaters restore t.e digital to t.eir original orm

Fig. 14

4nalog signals can only be amliied "including t.e noise eas#

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1.& 'ummary

Transmission tc!ni"#s

Truns only carry tele.one signals 0it.in t.e requency range o 3)) = 3$))

56

(it. frequency-division multile!ing "FDM$/ tele.one signals are modulated

0it. dierent carriers and transmitted simultaneously via a common line

(it. time-division multile!ing "TDM$/ coded consecutive samles o

tele.one signals are transmitted via a common line

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01-Tw2103eu01 Eg0001 Digital Transmission