How can I calculate data rate?

Hi all,

I was wondering how can I calculate data rate given:
-B: bandwidth
-cr: code rate (say convolution code)
-some modulation scheme assume the sinr is good enough

thanks,
Yiu 

On Sep 10, 5:20 pm, "blueyiu" <ca...@cs.pdx.edu> wrote:
> Hi all,
>
> I was wondering how can I calculate data rate given:
> -B: bandwidth
> -cr: code rate (say convolution code)
> -some modulation scheme assume the sinr is good enough
>
> thanks,
> Yiu

You sort of have a mix of ideas there. Is this a homework problem,
perhaps?

The available bandwidth will affect the maximum data rate that you can
reliably use, as it helps to define your channel capacity. With that
said, it is not directly involved in a "bitrate" type of calculation,
as it is more of a function of the symbol rate chosen by the designer
(ostensibly you), any overhead introduced by channel coding (i.e. a
1/2 rate or 1/3 rate convolutional code), and the number of bits
transmitted per symbol (1 for BPSK, potentially more than 1 using more
complicated schemes). These are all parameters chosen at design time;
there really isn't any "secret sauce" to calculating the resulting
bitrate. If you can't figure out how to massage these quantities to
get the overall rate out, you could perhaps use some further study.

Jason

Thanks Jason. At least one person reply makes me feel much better. This is
not home work assignment (it will be much better if it is =) 

Anyway, I am new in this field and try to figure it out this complication
relation between all the trade off. I found it really hard to look at any
graph because it shows you one better than another but (hiding the fact
that you need to trade something with it). For example, coding can get
better bit error rate or Eb/No but you need to trade with your bandwidth.
But how much? Don't know.

I am trying to generalize things. For example, if there are N parameters
(such as bandwidth, Eb/No, code rate, data rate, bit error rate...etc) One
should be able to calculate the one of these value given the rest and the
modulation scheme.

Til now, no one can clearly precisely tell me how to do so. If any one has
any idea, help would be highly appreciate! I read the digital communication
book, but the only trade off chapter is given a table (where this data got
calculate?), check if you can use such modulation or choice the best one.
I want to find out how to calculate the data.

Thanks!


>On Sep 10, 5:20 pm, "blueyiu" <ca...@cs.pdx.edu> wrote:
>> Hi all,
>>
>> I was wondering how can I calculate data rate given:
>> -B: bandwidth
>> -cr: code rate (say convolution code)
>> -some modulation scheme assume the sinr is good enough
>>
>> thanks,
>> Yiu
>
>You sort of have a mix of ideas there. Is this a homework problem,
>perhaps?
>
>The available bandwidth will affect the maximum data rate that you can
>reliably use, as it helps to define your channel capacity. With that
>said, it is not directly involved in a "bitrate" type of calculation,
>as it is more of a function of the symbol rate chosen by the designer
>(ostensibly you), any overhead introduced by channel coding (i.e. a
>1/2 rate or 1/3 rate convolutional code), and the number of bits
>transmitted per symbol (1 for BPSK, potentially more than 1 using more
>complicated schemes). These are all parameters chosen at design time;
>there really isn't any "secret sauce" to calculating the resulting
>bitrate. If you can't figure out how to massage these quantities to
>get the overall rate out, you could perhaps use some further study.
>
>Jason
>
>

On Sep 12, 12:27 am, "blueyiu" <ca...@cs.pdx.edu> wrote:
> Thanks Jason. At least one person reply makes me feel much better. This is
> not home work assignment (it will be much better if it is =)
>
> Anyway, I am new in this field and try to figure it out this complication
> relation between all the trade off. I found it really hard to look at any
> graph because it shows you one better than another but (hiding the fact
> that you need to trade something with it). For example, coding can get
> better bit error rate or Eb/No but you need to trade with your bandwidth.
> But how much? Don't know.
>
> I am trying to generalize things. For example, if there are N parameters
> (such as bandwidth, Eb/No, code rate, data rate, bit error rate...etc) One
> should be able to calculate the one of these value given the rest and the
> modulation scheme.
>
> Til now, no one can clearly precisely tell me how to do so. If any one has
> any idea, help would be highly appreciate! I read the digital communication
> book, but the only trade off chapter is given a table (where this data got
> calculate?), check if you can use such modulation or choice the best one.
> I want to find out how to calculate the data.
>

It sounds like you might be biting off more than you can chew.
Communication system design, like any other type of engineering, isn't
simple. There are many tradeoffs to consider; it's not something as
simple as just solving for the "unknown parameter." You'd be best
served by doing some more in-depth study in digital communications so
you understand the various aspects of a system more clearly. If you
truly understand the function of the major "blocks" (source encoding,
channel encoding, modulator, demodulator, etc.), then you can make
informed design decisions. For instance, channel encoding can get you
a better bit-error rate for a given value Eb/No, but you trade off
overall throughput since it involves the transmission of redundant
information. It's up to you as the designer to make the overall system
meet your requirements, since only you know what those are.

Jason