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Re: [Discuss-gnuradio] Can threading disturb sensing continuety

From: kaleem ahmad
Subject: Re: [Discuss-gnuradio] Can threading disturb sensing continuety
Date: Mon, 23 Mar 2009 07:20:13 -0700 (PDT)

Thanks for all these replies,

 The problem is my investigation about cycle time is not restricted to FSK,
I just gave the example of FSK system. I would like to calculate the cycle
time of any system (ZigBee, FSK, CSS etc) present in the area. My target is
to sense as much systems as possible and then calculate the cycle time of

Best Regards

Brian Padalino wrote:
> On Fri, Mar 20, 2009 at 1:27 PM, Johnathan Corgan
> <address@hidden> wrote:
>> A common, non-coherent method for FSK demodulation and baud rate
>> detection is to multiply each succeeding sample by the complex
>> conjugate of the preceding sample, then take the phase of the product.
>>  This turns the sample series into baseband "level" shifts.  If you
>> are at zero IF, then the sample stream will be roughly symmetrical
>> about zero (frequency offsets are turned into DC offsets, though).
>> From here you can use zero crossings to estimate baud rate and
>> integration between transitions to improve noise performance.  The
>> success of this technique relies on sufficient zero crossing density,
>> and has a higher bit error rate than coherent detection and
>> demodulation.
> Assuming an FSK system with unknown frequency separation and baudrate,
> is the above algorithm robust enough to determine said parameters to
> then pass along to a coherent demodulator to achieve a better BER?
> I would assume yes - since you're just taking a quick guess/estimate
> and letting the coherent demodulator actually timetrack, figure out
> the bits, etc.
> Brian
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