Is the signal within a LAN all digital

Posted on 2011-05-11
Medium Priority
Last Modified: 2012-05-11
I have a discucssion with my friend about digital or analog signal. I know that from a modem will translate (or modulate)  the digital signal from the computer or router to an analog signal and send to the network. Does it means that all the signal within a simple home LAN is digital ? I can transfer almost 0.5 GBit/s with my LANs. What is the signal format in that cat6 cable. Is it really digital ? Or the digital signal is actually embedded inside some analog signal ?
Question by:wilsonchtam
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LVL 22

Expert Comment

ID: 35740766
Yes, it is a digital signal.  The spec is defined under IEEE 802.3

Author Comment

ID: 35740871
Hi eeRoot,
Thanks for your quick respond. Does 802.3 specify the physical layer needs to be a square wave with 1 or 0 ?
My next question is 'What is the frequency in the cat6 cable' ? Can the frequency transfer 1Gbit/s without any modulation or multiplexing ?

LVL 11

Accepted Solution

Patmac951 earned 750 total points
ID: 35741093
Yes the a CAT6 cable is certified to handle a throughput of 1GB assuming your network devices, switches and network cards in the computers are 1GB.  However from personal experience I have had no problem running CAT5 cable in 1GB network environment.  Physically there is very little difference in a CAT5 or a CAT6 cable....the sheilding on a CAT6 cable is a little different.

As far as the physical layer needing to be a square wave check out this link:
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LVL 22

Expert Comment

ID: 35741108
Yes, 802.3 defines the signal as a square wave, with different specs for the different types of cabling and transmission speeds.

The spec for Cat6 calls for 200 - 250 MHz.  And a 1 Gbps connection does require modulation.

I don't *think* there is any multiplexing in a standard 1 Gbps Cat6 connection, although there may be some proprietary/unique setups that do.

Author Comment

ID: 35742796
Thanks eeRoot.
I just checked the link your provided. 1000BASE/T (Gig E) uses all four pairs. Each pair sends data bi-directionally. Signals are variations of sine waves; the peak voltage of each "wave" is 5 levels.
That's why it can provide the 1Gbps with a 200Mhz.

Author Closing Comment

ID: 35742799
The next question make the answer complete

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