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Re: [Discuss-gnuradio] OFDM receiver on USRP2
From: |
Guanbo |
Subject: |
Re: [Discuss-gnuradio] OFDM receiver on USRP2 |
Date: |
Wed, 12 Jan 2011 16:37:16 -0800 (PST) |
Hi, Tom
I am not quite understand the ofdm_sync_xx.cc in python/gnuradio/blks2impl/.
What is the difference between frequency synchronization and carrier
frequency offset.
Why we have to do the timing and frequency synchronization before it?
Also,
Thanks,
Guanbo
Tom Rondeau wrote:
>
> On Tue, Feb 16, 2010 at 5:45 PM, Srinivas <address@hidden> wrote:
>> Matt,
>>
>> Thanks for verifying the data rate calculation!
>>
>> I tried the other solutions that you suggested, namely,
>>
>> - increasing the data rate by a factor of 2 or 4
>> It works.
>>
>> - modifying the OFDM code to widen the search range - How do I widen the
>> search range ?
>> Should I be looking in the "ofdm_sync_" blocks in "blks2impl" folder ? If
>> yes, which synchronizer is currently used with ofdm_examples ?
>
> You need to add an argument to gr.ofdm_frame_acquisition in
> ofdm_receiver.py (in python/gnuradio/blks2impl).
>
> In the current Git master, this is located on line 109 of
> ofdm_receiver.py. After the "ks[0]" argument, you can put in an
> integer. This is the maximum number of bins the receiver will search
> over for correlation. It defaults to 10.
>
>
>> - locking the usrps to a common reference
>> My usrp2s are located wide apart so I guess this solution is not
>> practical.
>>
>> Besides, this confirms that the problem is somewhere in the USRP2 board,
>> right ? (as I tried swapping the daughter cards & firmware with the
>> working
>> pair)
>>
>> Thanks,
>> Srinivas
>
> Nope, this is typical of radio hardware. They are always off
> frequency. If two oscillators are off frequency and then multiplied up
> to another frequency, the difference will also be magnified. So a 2.4
> GHz board will have a larger frequency offset than if you ran it just
> through the BasicTx/Rx boards (even though the ratios should be the
> same).
>
> Tom
>
>
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>
>
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