Hermann,
I was wondering about that too! I found a slide presentation introducing
IEEE 802.3ab.
This signaling method actually sends signals in both directions
simultaneously.
It uses a "hybrid" circuit to remove the "self echo", ie cancel its own
transmission at it's receiver.
It also uses a lot of transistors for a complex encoding scheme, as well as
Digital Signal Processing
for Echo Cancellation and Crosstalk removal. It does training and adaptive
EQ.
It was also an early example of the use of DFE (decision feedback eq).
It required 125 MHz, 7-bit A/D conversion, to capture the 4-level data, back
in 1996 or so.
-Paul
-----Original Message-----
From: Hermann Ruckerbauer
Sent: Thursday, May 14, 2015 6:16 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Ethernet 1000-BaseT Full duplex Signaling ..
Hello *,
I know i can do some more homework on this one .. but I hope somebody
can provide a hint where to start (the Ethernet spec is very
comprehensive ;-) )
100Mb Ethernet (BASE-T) does have a RX and TX pair ... so full Duplex
seems quite simple as TX and RX direction can be handeled independently ...
I did quite some reading on Gigabit Ethernet (1000Base-T) and do
(partly) understand how we get the Gigabit Transferrate on 4 pairs by
coding.
What I have not found: How is this "Full duplex" done ?
There are no dedicated RX/TX wires, so either this is done
"Bidirectional" and write / Read "time slots" (allowing only 1Gb in one
direction), or simultanious bidirectional by subtracting sent from
received data ( allowing 1Gb TX + 1Gb RX = 2Gb transferrate in both
direction (what would be my understanding of "Full duplex) )
Or there might be another way to implement full duplex if all 4
wirepairs are used for one direction ..
If anybody could tell me what too look for in the ethernet spec (or give
a short explanation) this would be very much appreciated ..
Thanks and regards
Hermann
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