| Title: | DEChub/HUBwatch/PROBEwatch CONFERENCE |
| Notice: | Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7 |
| Moderator: | NETCAD::COLELLA DT |
| Created: | Wed Nov 13 1991 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 4455 |
| Total number of notes: | 16761 |
Some customer questions....
In the Open DECconnect Applications Guide on page 2-6 regarding
FDDI (TP-PMD), it says "Although the data rate is 100Mb/s, the peak
signal power is below 31.25 MHz because of the MLT3 encoding scheme."
What does this mean?
Does the encoding scheme actually move data at 100Mb/s?
Thanks,
Dave
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 2314.1 | NETCAD::B_CRONIN | Wed May 24 1995 19:30 | 22 | ||
The MAC to MAC data rate is 100 Mbps.
The transmission rate on the PHY is faster than that, because of
the coding involved. The MLT-3 coding transmits with a transition
rate of 8 ns, which is a rate of 125 Mbaud. This is, by the way, the
same transmission rate as the optics, but it uses a 3 level code,
rather than a 2 level code like the optics uses.
All signaling schemes have signal energy distributed across some band of
frequencies. In this case, the peak of the energy in the coded signal
lies below a frequency of 31.5 MHz, (but some energy extends out
as high as 125 MHz) If you took an MLT-3 signal, and connected it to
a spectrum analyzer, you would see a peak in the spectral energy
around 31 MHz.
So, the data rate is 100 Mbps; the transmission rate is 125 Mbaud, and
the distibution of the signal power (in the frequency domain) peaks
around 31 MHz.
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| 2314.2 | Thanks | ALBANY::BARTLEY | Thu May 25 1995 12:17 | 1 | |
| 2314.3 | but is standard, ok? | MXOC00::CSILVA | Thu May 25 1995 17:46 | 10 | |
Question?
In wich standard is specified that coding scheme?
Are we talking of course of a PMD ANSI FDDI spec. true?
Carlos
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| 2314.4 | It's in there.. | ALBANY::BARTLEY | Fri May 26 1995 10:12 | 7 | |
This is out of the Open DECconnect Guide on page 2-6,
"(MLT3 is specified in TP-PMD portion of the ANSI X3T9.5 standard.)"
Dave
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| 2314.5 | Thanks! | MXOC00::CSILVA | Fri May 26 1995 15:03 | 1 | |