Relationship between baud and characters-per-second? Other questions too.

[Green Xenon [Radium]]

Hi:

What is the relationship between baud, bits-per-character, and
characters-per-second?

Carrying more bits-per-symbol saves bandwidth as opposed to using more
bauds-per-symbol.

Does carrying more bits-per-character use up less bandwidth than
carrying more characters-per-bit?

http://en.wikipedia.org/wiki/Baud

“Conveying more than one bit per symbol has advantages. It reduces the
time required to send a given quantity of data, and allows modern
modems, FDDI and 100/1000 Mbit/s Ethernet LANs, and others, to achieve
high data rates. An optimal symbol set design takes into account channel
bandwidth, desired information rate, noise characteristics of the
channel and the receiver, and receiver and decoder complexity. A typical
2400-bit/s modem transmits at 600 baud (600 symbol/s), where each
quadrature amplitude modulation symbol carries four bits of information.
1000 Mbit/s Ethernet LAN cables use many wire pairs and many bits per
symbol to encode their data payloads. 1000BASE-T uses four wire pairs
and two data bits per symbol to get a symbol rate of 125MBd.”

“Representing one bit by many symbols overcomes signal noise like radio
jamming, and is common in military radio and CDMA radio, including cell
phones, despite using more bandwidth to carry the same bit rate. In
these systems, each signal is called a "chip" and the baud the "chip rate".”

Unfortunately I don’t think this answers my question. Unless of course,
if symbols and characters are the same thing.

Are “bits-per-symbol” and “bits-per-character” the same thing? I did a
Google search for “bits-per-character” and “characters-per-second” but
didn’t see much in terms of telecommunications, baud and modems.

http://www.google.com/search?hl=en&q=bits-per-character&btnG=Search

http://www.google.com/search?hl=en&q=%22characters+per+second%22&btnG=Search

OTOH, “bits-per-symbol” gave tons of links about telecommunications,
baud and modems.

http://www.google.com/search?hl=en&q=bits-per-symbol&btnG=Search

Thanks,

Radium

[Bob]

"Green Xenon [Radium]" <gluc...@excite.com> wrote in message
news:46e8c520$0$11012$4c36...@roadrunner.com...

> Hi:
>
> What is the relationship between baud, bits-per-character, and
> characters-per-second?

>
[snip]

>
> Thanks,
>
> Radium

Are you trying to get some homework done or do you really want to understand
these concepts? It seems from your post that it's the former.

Either way, here are the basics. From this you should be able to deduce the
answers you seek.

A symbol can represent one or more bits. For example, if you decide to
transmit data using only two signal level regions (e.g. 3.3V LVTTL -- where
a low = -0.5V to 0.8V and a high = 2.0V to 3.8V) then each symbol will carry
one bit of information. However, what if you allowed sixteen different
signal level regions instead of only two? Then, each symbol will carry four
bits of information. It mostly depends on the transmission path as to how
many bits you can represent with each symbol. If you're sending data through
a digital IC then you can only get one bit per symbol, but if you're sending
data through some type of analog medium then you can get more than one bit
(i.e. two signal levels) through the channel.

A baud is equal to the number of symbols sent per second.

A "character" can be made up of as many bits as is required. Typically, a
character (like an ASCII character) is eight bits.

Think about this for a while until it makes sense to you.

Bob

[Green Xenon [Radium]]

Bob wrote:

> Are you trying to get some homework done or do you really want to understand
> these concepts? It seems from your post that it's the former.

No. It's the latter.

> Either way, here are the basics. From this you should be able to deduce the
> answers you seek.

Okay.

> A symbol can represent one or more bits. For example, if you decide to
> transmit data using only two signal level regions (e.g. 3.3V LVTTL -- where
> a low = -0.5V to 0.8V and a high = 2.0V to 3.8V) then each symbol will carry
> one bit of information. However, what if you allowed sixteen different
> signal level regions instead of only two? Then, each symbol will carry four
> bits of information. It mostly depends on the transmission path as to how
> many bits you can represent with each symbol. If you're sending data through
> a digital IC then you can only get one bit per symbol, but if you're sending
> data through some type of analog medium then you can get more than one bit
> (i.e. two signal levels) through the channel.

Thanks.

> A baud is equal to the number of symbols sent per second.

Yes.

> A "character" can be made up of as many bits as is required. Typically, a
> character (like an ASCII character) is eight bits.

What about characters-per-second?

> Think about this for a while until it makes sense to you.

Most of it does make sense, except for the characters-per-second.

If there is a difference between "characters-per-second" and
"symbols-per-second", what is this difference?

[Bob]

"Green Xenon [Radium]" <gluc...@excite.com> wrote in message

news:46e8ced2$0$17100$4c36...@roadrunner.com...

It's just simple math. You haven't thought long enough, otherwise it would
be obvious to you.

It is very important that you do this for yourself. Someone once said:

"Give a man a fire and he'll be warm for a day. Set a man afire and he'll be
warm for the rest of his life."

Bob

Bob

[_]

simple maths

char/sec = (sym/sec) / (sym/char)

Are you *sure* this isn't homework?

[Tam/WB2TT]

"Green Xenon [Radium]" <gluc...@excite.com> wrote in message

news:46e8c520$0$11012$4c36...@roadrunner.com...

> Hi:
>
> What is the relationship between baud, bits-per-character, and
> characters-per-second?
>

Baud refers to how often the actual line signal changes state; the same as
symbols per second. Bits per character is really an animal of a different
color, and depends on the original encoding. For ASCII, a common value is 8
bits per character. For instance, the 8 bit ASCII code for the numeral 1 is
00110001. For 8 bit encoding the number of characters per second is 1/8 th
the bits per second, but usually not 1/8 the symbols/second. I am ignoring
any extra bits and characters which are often added.

> Carrying more bits-per-symbol saves bandwidth as opposed to using more
> bauds-per-symbol.
>

Suppose you transmit a 4 level signal. Call these A,B,C, and D. Suppose the
bits are packed into the symbols so that A=00, B=01, C=10, and D=11. You can
see that each symbol carries 2 bits, so that the baud rate would be 1/2 the
bit rate. For a 16 level signal, each symbol carries 4 bits.

Baud is symbols/second. Any time you increase the baud rate you increase the
bandwidth.

> Does carrying more bits-per-character use up less bandwidth than carrying
> more characters-per-bit?

You will have to work this out, but having LESS bits per character reduces
the bits per second and bandwidth. The original Teletype code used 5 bits
per character. This only allows for 32 characters, so, one of the characters
was a SHIFT character.

Tam

[Green Xenon [Radium]]

On Sep 13, 4:00 am, _ <jtayNOSPAM...@hfDONTSENDMESPAMx.andara.com> wrote
in
http://groups.google.com/group/sci.electronics.design/msg/d381292543bbfd9a?hl=en&
:

> simple maths
>
> char/sec = (sym/sec) / (sym/char)

What about char/bit?

char/bit = ?

> Are you *sure* this isn't homework?

Yes.

[Green Xenon [Radium]]

On Sep 13, 8:25 am, "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in
http://groups.google.com/group/sci.electronics.design/msg/f61737940524d4bc?hl=en&
:

> "Green Xenon [Radium]" <gluceg...@excite.com> wrote in
>messagenews:46e8c520$0$11012$4c36...@roadrunner.com...

> > What is the relationship between baud, bits-per-character, and
> > characters-per-second?

> Baud refers to how often the actual line signal changes state; the

same as
> symbols per second. Bits per character is really an animal of a different
> color, and depends on the original encoding. For ASCII, a common
value is 8
> bits per character. For instance, the 8 bit ASCII code for the
numeral 1 is
> 00110001. For 8 bit encoding the number of characters per second is
1/8 th
> the bits per second, but usually not 1/8 the symbols/second. I am
ignoring
> any extra bits and characters which are often added.

Why not 1/8 the symbols/seconds? Wouldn’t using fewer symbols-per-second
make it easer to transmit/receive in high-speed? The less
symbols-per-second, the less bandwidth is used, regardless of the amount
of bits-per-symbol.

> > Carrying more bits-per-symbol saves bandwidth as opposed to using more
> > bauds-per-symbol.

> Suppose you transmit a 4 level signal. Call these A,B,C, and D.

Suppose the
> bits are packed into the symbols so that A=00, B=01, C=10, and D=11.
You can
> see that each symbol carries 2 bits, so that the baud rate would be
1/2 the
> bit rate. For a 16 level signal, each symbol carries 4 bits.

Okay.

> Baud is symbols/second. Any time you increase the baud rate you
increase the
> bandwidth.

Yes.

> > Does carrying more bits-per-character use up less bandwidth than
carrying
> > more characters-per-bit?

> You will have to work this out, but having LESS bits per character

reduces
> the bits per second and bandwidth. The original Teletype code used 5 bits
> per character. This only allows for 32 characters, so, one of the
characters
> was a SHIFT character.

If you have more bits-per-character but less characters-per-second,
would this be more efficient in terms of bandwidth usage?

I ask because I am aware that more bits-per-symbol but fewer
symbols-per-second makes better use of bandwidth. So I am guessing that
this is analogous.

[Tam/WB2TT]

"Green Xenon [Radium]" <gluc...@excite.com> wrote in message

news:46e9b09b$0$19593$4c36...@roadrunner.com...

> On Sep 13, 8:25 am, "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in
> http://groups.google.com/group/sci.electronics.design/msg/f61737940524d4bc?hl=en& :
>
> > "Green Xenon [Radium]" <gluceg...@excite.com> wrote in
> > messagenews:46e8c520$0$11012$4c36...@roadrunner.com...
>
> > > What is the relationship between baud, bits-per-character, and
> > > characters-per-second?
>
> > Baud refers to how often the actual line signal changes state; the
> same as
> > symbols per second. Bits per character is really an animal of a
> > different
> > color, and depends on the original encoding. For ASCII, a common
> value is 8
> > bits per character. For instance, the 8 bit ASCII code for the
> numeral 1 is
> > 00110001. For 8 bit encoding the number of characters per second is
> 1/8 th
> > the bits per second, but usually not 1/8 the symbols/second. I am
> ignoring
> > any extra bits and characters which are often added.
>
> Why not 1/8 the symbols/seconds? Wouldn’t using fewer symbols-per-second
> make it easer to transmit/receive in high-speed? The less
> symbols-per-second, the less bandwidth is used, regardless of the amount
> of bits-per-symbol.
>

If you want to keep the overall data rate the same, then if you go to 1/8 as
many symbols/second as before you now need to have 8X as many bits per
symbol as before. Actually, this kind of thing is done, but there is a limit
as to how far you can go because every time you increase the bits/symbol,
the effective signal to noise ratio gets worse unless you increase the
power. For ATSC HDTV they go 3 bits/symbol for over the air transmission;
that means each symbol can have one of 8 values (2**3=8). If you wanted to
have 8 bits/symbol then each symbol must be capable of having one of 256
values (2**8 = 256). If you keep the power the same, then the resultant
signal will be 256 times more susceptible to noise than straight binary.

Tam

[Green Xenon [Radium]]

Tam/WB2TT wrote:

> If you want to keep the overall data rate the same, then if you go to 1/8 as
> many symbols/second as before you now need to have 8X as many bits per
> symbol as before. Actually, this kind of thing is done, but there is a limit
> as to how far you can go because every time you increase the bits/symbol,
> the effective signal to noise ratio gets worse unless you increase the
> power. For ATSC HDTV they go 3 bits/symbol for over the air transmission;
> that means each symbol can have one of 8 values (2**3=8). If you wanted to
> have 8 bits/symbol then each symbol must be capable of having one of 256
> values (2**8 = 256). If you keep the power the same, then the resultant
> signal will be 256 times more susceptible to noise than straight binary.

Ignoring the SNR, is there a physical limit to how many bits-per-symbol
a device can transmit/receive/process/record/playback if the symbol rate
is only 1 baud [1 symbol per second]?

Is it possible to have only 1-symbol-per-second but
1-billion-bits-per-symbol?

Also, my previous question -- [*most important and interesting to me*]: