Re: Correct use of the term Baud
At 11:29 AM 12-02-2000 +0900, Dae Young KIM wrote:
>This maybe a small thing to be ignored and I might be wrong, but...:
>"Baud" by itself means a rate:
> Baud == symbol rate = signaling rate = symbols/sec
the origin of the term has been traced to a man who was working on telegraphy
in France, a long time ago (can't recall the year at the moment, but i can get it
if you'd like) whose name was Baudot. according to the story that i read, he
was working on a relatively low-rate (by today's standard) encoding scheme
and the term "baud" came to be known as the number of symbols transmitted
per second over an ordinary wire line. today, those who use the phrase
"baud rate" are actually saying "symbol rate rate", which either describes
a kind of symbol acceleration or is redundant. also, "baud" and "bit rate"
seldom mean the same thing.
>So, it is correct to say like "8B10B has a data rate of 10Gbps and a
>symbol rate of 12.5GBaud."
somewhat correct, though here it seems you highlight a difference in data
communication with, and without, "overhead". in this, "10Gbps" may be
the "payload" or base information that is to be transmitted from point A
to point B, and the additional "2.5Gbaud" would be excess coding that is
meant to correct for baseline wander, correct for transmission error, signal
one kind of management control or another, and so on.
so... if you want to transmit 10Gbits in one second, and you choose the
current 8b10b encoding scheme (there are many ways to create a map
between 8 bits of data and 10 bits of line code but one is currently popular),
the added overhead forces you to transmit symbols at 12.5Gbaud.
aside: most of us describe a line rate of 10^9 with a soft "g" as in the
word "get" or "gone", but the word "giga" originally had a hard "g"
similar to "j" in "jet". so far, i've met only one person who consistently
uses the original pronunciation.