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# Explain the differences between modulation and multiplexing

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#### pmonon

##### Full Member level 3
Explain the differences between modulation and multiplexing?

#### jakjoud

##### Full Member level 2
Re: Explain the differences between modulation and multiplex

Ok,
Modulation is when you have a low frequency signal and you want to transit it for exemple, it's useful to grow up its frequency, so you use a modulation method (AM FM PM in analogical modulations ASK FSK and PSK for digital ones).
AM or ASK is an amplitude modulation: it's about variying the amplitude of a high frequency signal (carrier) in function of your signal(information) then in reception you can easily demodulate the signal by detecting the enveloppe (a diod with a lowpass filter).
The Fm or FSK is a frequency modulation, it's a bit more difficult than amplitude one but in general it's the same principle you change the frequency of your carrier in function of the information.
The same thing is applying when you want a phase modulation PM or PSK but changing the phase.

Multiplexing is a different thing it's when you have one transmission support and you have many signals to transmit through it, so there is three kinds of multiplexing (at least)
in time: which means that you take every laps δt of a signal and you send it through you transmission support. then you switch to the other signal....
in frequency which means that you have (or modulate ) your signals at different frequencies so you send them all on the support at reception a simple filter bandpass permit to have every signal alone.
There in a hybrid mode of multiplexing which combains the two modes.
Sorry for my bad english I just try to express what I have learned in french and really it's hard.

### pmonon

Points: 2

#### bcl

##### Member level 1
Re: Explain the differences between modulation and multiplex

In a nuttshell;
Modulation: analog or digital baseband signal multiplied (in time domain) by a carrier signal.

Multiplexing: selecting two or more parallel signals to the signle output in an alternating fashion.

### pmonon

Points: 2

#### music_lover04

##### Newbie level 6
Re: Explain the differences between modulation and multiplex

Modulation is for transmission of a signal over an RF band (wireless). eg analog modulation (AM, FM, PM) and digital (ASK,PSK,FSK etc....)

Multiplexing is generally done for parallel communications and is genarally wired.

#### venkateshkumar

##### Newbie level 6
Re: Explain the differences between modulation and multiplex

hai
In telecommunications, modulation is the process of varying a periodic waveform, i.e. a tone, in order to use that signal to convey a message, in a similar fashion as a musician may modulate the tone from a musical instrument by varying its volume, timing and pitch. Normally a high-frequency sinusoid waveform is used as carrier signal. The three key parameters of a sine wave are its amplitude ("volume"), its phase ("timing") and its frequency ("pitch"), all of which can be modified in accordance with a low frequency information signal to obtain the modulated signal.

multiplexing

In electronics, telecommunications and computer networks, multiplexing is a term used to refer to a process where multiple analog message signals or digital data streams are combined into one signal. The aim is to share an expensive resource. For example, in electronics, multiplexing allows several analog signals to be processed by one analog-to-digital converter (ADC), and in telecommunications, several phone calls may be transferred using one wire.

its enougf i think

#### aztroboy

##### Newbie level 4
Re: Explain the differences between modulation and multiplex

jakjoud said:
Ok,
Modulation is when you have a low frequency signal and you want to transit it for exemple, it's useful to grow up its frequency, so you use a modulation method (AM FM PM in analogical modulations ASK FSK and PSK for digital ones).
AM or ASK is an amplitude modulation: it's about variying the amplitude of a high frequency signal (carrier) in function of your signal(information) then in reception you can easily demodulate the signal by detecting the enveloppe (a diod with a lowpass filter).
The Fm or FSK is a frequency modulation, it's a bit more difficult than amplitude one but in general it's the same principle you change the frequency of your carrier in function of the information.
The same thing is applying when you want a phase modulation PM or PSK but changing the phase.

Multiplexing is a different thing it's when you have one transmission support and you have many signals to transmit through it, so there is three kinds of multiplexing (at least)
in time: which means that you take every laps δt of a signal and you send it through you transmission support. then you switch to the other signal....
in frequency which means that you have (or modulate ) your signals at different frequencies so you send them all on the support at reception a simple filter bandpass permit to have every signal alone.
There in a hybrid mode of multiplexing which combains the two modes.
Sorry for my bad english I just try to express what I have learned in french and really it's hard.
this would be the finest ansewer

#### vizard356

##### Newbie level 6
Modulation is basically transmit the lower frequency signal on high frequency signal.

While multiplexing is required because transmitting channel has finite bandwith(means frequency range that can be transmitted).
It means that one can transmit different frequency signal(as far as they are not overlapping) on the same channel. And for that we use modulation to change frequency of the signal we want to transmit.

#### Naveed Alam

##### Full Member level 5
Re: Explain the differences between modulation and multiplex

Modulation: TX of baseband signal (its low frequency) using high frequency carrier.
Multiplexing: Before modulation more than one carriers are multiplexed (added in a manner to be seen one), then this multiplexed signal is transmitted.

Regards,

#### vkalariya

##### Member level 1
Re: Explain the differences between modulation and multiplex

multiplex : one single channel or single carrier you are going to transmit the more number of information using the multilexing. we can say that the this is the method of one type of modulation with more than one modulating signal.

modulation means transforming the spectrum of the modulating signal to higher frequency

#### pico

##### Full Member level 6
Modulation = How message is carried by the carrier into a channel.
Mutiplex = How to carry more than 1 message together into a channel.

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