Re: [Discuss-gnuradio] 802.11a source codes? or any OFDM implementation on GNU Radio

[Dan Halperin]

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On Sep 11, 2008, at 11:26 AM, Mohsen Baratvand wrote:

> Guy, all I need to do is changing some parameters such as preamble,  
> LTF, STF, modulation and etc of the OFDM transmitter and then send a  
> predefined pattern to the OFDM receiver, then estimate the channel.  
> So I'm not gonna pass all the information and data to PC via the USB  
> link. Just sending some report to my PC.

It's conceivable that by putting the modulation in the FPGA, you could  
get 802.11a OFDM modulation to work using the USRP -- just send the  
data across the bus. But no one has written such a firmware image yet  
- -- feel free! (Disclaimer: I have no idea whether an 802.11a modulator  
would fit into the small FPGA on USRP1, and haven't tried).

If you want to do modulation in the host, which doesn't involve FPGA  
coding and might allow you to use some of the existing OFDM code,  
you're going to be limited by the bandwidth of the USB -- 8 MHz isn't  
really enough. If you used 8-bit mode to get 16 MHz of bandwidth AND  
used one of the low bitrate encodings, high-SNR packets MIGHT get  
received by a good receiver. I don't know enough about 802.11's use of  
OFDM to decide. Maybe Kyle or Tom has a comment here.

- -Dan
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