Upsampling - questions

[Girly_girl]

whats the advantage of using Upsampling in an OFDM modem? and why do we use it?

is the other approach using DAC?

How does the upsampling factor affects the data ?

 

[ckshivaram]

**broken link removed**
UPSAMPLING/INTERPOLATION AND TIME ALIGNMENT MECHANISM UTILIZING INJECTION OF HIGH FREQUENCY NOISE

 

[swordfish01]

Hi,

I'm not entirely sure about the OFDM, but with upsampling you increase your symbol rate. To get an accurate answer you might have to tell us where the upsampling occurs (before the IDFT, after it, etc.). If the iDFT output is upsampled, it may be to decrease inter-symbol interference.

If I'm not mixing abbreviations completely, then DAC mean Digital to Analog Converter, and it is used to convert the digital signal (in that case the iDFT output, most likely filtered by a raised cosine filter) to an analog signal that can be mixed with your carrier frequency.

If my assumption (upsampling after iDFT) is correct, then the data is completely uneffected, just the symbol rate is higher, depending on you upsampling factor.
In general: the data should never be different after upsampling, it is just there at a higher sampling frequency (and if not filtered after the upsampling with images of the original signal)

Regards,
Andreas

 

[Girly_girl]

many thanks..
ur assumption is correct.. Thank u..
yea my upsampling factor is 1 .. hence nothing is changed..
Thanks alot
Regards