OFDM or SC-FDMA

Hi  All,

  1) I  want to implement MODEM with 128Kbps at 100Khz  with high
doppler shift channel. Which modulation technique would be suitable .
Whether I can go with OFDM or SC-FDMA?    Any suggestions

  2) Is it possible to simulate  128Kbps with Matlab



Thanks & Regards,
Ammankumar.S

On Tue, 03 Mar 2009 20:32:40 -0800, Ammankumar wrote:

> Hi  All,
> 
>   1) I  want to implement MODEM with 128Kbps at 100Khz  with high
> doppler shift channel. Which modulation technique would be suitable .
> Whether I can go with OFDM or SC-FDMA?    Any suggestions

Dunno.  It probably depends on a lot more than you've put down here.

>   2) Is it possible to simulate  128Kbps with Matlab

As long as you don't mind not being in real time, you can simulate 
128Gbps in Matlab.

-- 
http://www.wescottdesign.com

Ammankumar schrieb:
> Hi  All,
> 
>   1) I  want to implement MODEM with 128Kbps at 100Khz  with high
> doppler shift channel. Which modulation technique would be suitable .
> Whether I can go with OFDM or SC-FDMA?    Any suggestions
> 
>   2) Is it possible to simulate  128Kbps with Matlab
> 
> 
> 
> Thanks & Regards,
> Ammankumar.S


OFDM will be more sensitive to doppler shifts than a single carrier 
system when assuming the same symbol bandwidth. But just like already 
stated this is influenced by a whole lot of more issues than just the 
modulation scheme like forward error correction, the way you shape the 
spectrum of your single carrier system etc.

Ammankumar wrote:

> Hi  All,
> 
>   1) I  want to implement MODEM with 128Kbps at 100Khz  with high
> doppler shift channel. Which modulation technique would be suitable .
> Whether I can go with OFDM or SC-FDMA?    Any suggestions

Whatever you do, you will be f...

>   2) Is it possible to simulate  128Kbps with Matlab

Not for you.

VLV

1> OFDM and SC-FDMA  are almost identical except for DFT pre-coding
done in the later. The only additional benefit you get in SC-FDMA is
low PAPR. The only downside is additional FFT stage. Regarding doppler
shift. Both OFDM and SC-FDMA are bad with high doppler. What we need
to know is the bandwidth rather than the carrier frequency. From that
we can calculate the sub-carrier spacing based on the data rate you
wan't to support. The receiver is simplified if the doppler shift is
substantially less than the sub-carrier spacing.
2> Nobody does real-time simulation with matlab. So whether it is 1
Kbps or 1 Gbps, it really doesn't matter.


Regards
Piyush

On Mar 5, 12:03�am, piyushk...@gmail.com wrote:
> 1> OFDM and SC-FDMA �are almost identical except for DFT pre-coding
> done in the later. The only additional benefit you get in SC-FDMA is
> low PAPR. The only downside is additional FFT stage. Regarding doppler
> shift. Both OFDM and SC-FDMA are bad with high doppler. What we need
> to know is the bandwidth rather than the carrier frequency. From that
> we can calculate the sub-carrier spacing based on the data rate you
> wan't to support. The receiver is simplified if the doppler shift is
> substantially less than the sub-carrier spacing.
> 2> Nobody does real-time simulation with matlab. So whether it is 1
> Kbps or 1 Gbps, it really doesn't matter.
>
> Regards
> Piyush

SC-FDMA makes sense when you do multiple access to lower the PAPR. If
it is only for one to one communications, ofdm should be the choice.
Or, you can even simply transmit in the time domain and
use equalizer (such as viterbi) at the receiver side, which should
give you the optimal performance.