modulation and demodulation ?

[Muneeb Ahsan]

hi everyone,
i want to ask a very basic question? who performs modulation and demodulation? NIC(network interface card) or modem(provided by ISP)? Modulation and demodulation is necessary because the information which we want to send primarily consists of 1's and 0's which cant be traveled as it is on transmission medium such as cat5 cable. so it is nic which connects to home router by a cable. so if it is, then nic should have performed some kind of conversion so that information can be traveled.
please make my concept clear, i'm very much confused.
Thanks in advance

 

[thx1138v2]

"Modem" stands for MOdulator-DEModulator. It provides both functions. It modulates the digital signal to an analog signal for transmission. It demodulates a received analog signal to a digital signal.
https://en.wikipedia.org/wiki/Modem

CAT5, CAT6, NIC, etc are only designed to handle digital signals and have relatively severe distance limitations compared to analog cable transmissions.

Wireless connections also use modems to transmit and receive data. In this case the analog signal is the radio signal between the ends of the wireless connection rather than a cable. A digital signal is modulated to an analog radio signal for transmission and the received analog signal is demodulated to a digital signal.

Generally speaking, analog signals are sine wave signals that are either amplitude or frequency modulated and digital signals are always square wave signals. It gets a lot more complicated than that but that's the basic scenario.
https://en.wikipedia.org/wiki/Amplitude_modulation
https://en.wikipedia.org/wiki/Frequency_modulation
https://en.wikipedia.org/wiki/Square_wave

 

[jsmithepa]

or modem(provided by ISP)?

^This.

MO-DEM (MOdulation-DEModulation) duh!

At every step of the signal path, all sort of conversions are performed, nothing new there.

You may want to read up on RF versus BASELINE signals, because that's what exist at either end of a modem.

An IT person seldom concerns himself with this item, an ISP guy, a little. An IT classroom situation, they seem to be at least obligated to mention that there is such a thing but is not something that you have to configure. WIFI signal is RF but they don't talk about modulated signal here, you just learn coverage, spectrum, channels assignment, channels overlapping, signal strength, signal-to-noise.