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Oversampling in OFDM

Started by Mas Bas July 25, 2005
Hi,

I have a question related with the OFDM transmitter. What is the 
commonly method to increase the sampling rate ?

- Increasing the IFFT size and insert zero in the inpput ?
or
- Insert zero in the IFFT output and followed by interpolation filter ?

What is the trade-off ? anyone can help ?

Thanks.

Buzz

> Hi, > > I have a question related with the OFDM transmitter. What is the commonly > method to increase the sampling rate ? > > - Increasing the IFFT size and insert zero in the inpput ? > or > - Insert zero in the IFFT output and followed by interpolation filter ? > > What is the trade-off ? anyone can help ? > > Thanks. > > Buzz
To me this doesn't seem very straightforward to answer. The first solution would be the easiest and cost less HW/SW, certainly if you optimize the IFFT by knowing that some (most?) of the inputs are 0. However I would expect that the out-of-band suppression isn't very good with the first solution as you still keep the sinx/x of the all OFDM carriers between the extra inserted zeros. The interpolation filter you can make as good/bad as you want. Probably if you don't care about what is going on outside the OFDM band, doing the first would be best/cheapest you could also just use a very simple interpolation filter. Intiutively I would think tha exploiting the very HW/SW efficient IFFT in some way woud be a good thing to do. NL