Re: [Discuss-gnuradio] DSSS sync question

[Richard Bell]

So long as you know what you're looking for in any given scenario, you can use that to correlate to. It can be data or a preamble. If your receiver knows the data will always be a certain way ahead of time though, it's hard to call that data. Semantics at that point.

Rich

On Fri, Feb 5, 2016 at 2:44 PM, Henry Barton <address@hidden> wrote:

That sounds great, Richard. But I wonder, what if the useful payload contains that sequence by chance?

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From: Richard Bell
Sent: ‎Friday‎, ‎February‎ ‎5‎, ‎2016 ‎5‎:‎27‎ ‎PM
To: Henry Barton
Cc: address@hidden

Typically a correlator is used to look for a known sequence of bits, so the radio can align the rest of the processing from the end of this known sequence. This is referred to as frame synchronization. You could use the correlation estimation block to implement something like this. It would place a tag on the stream when it finds your known sequence and you would then know how everything is aligned from then on.

Rich

On Fri, Feb 5, 2016 at 1:04 PM, Henry Barton <address@hidden> wrote:

Hi all. I've successfully written a DSSS modulator and demodulator in Windows with a chip rate of 16x. It writes samples to a file that the demodulator can read and despread. Before I try any practical implementations, I need to know how a DSSS stream would be synchronized. Assuming the transmitter and receiver were perfectly clocked in unison, what stops the receiver from tuning in in the middle of a byte, thus getting a nibble from the current byte and a nibble from the next?

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