|
From: | Henry Barton |
Subject: | Re: [Discuss-gnuradio] DSSS sync question |
Date: | Fri, 5 Feb 2016 23:07:46 +0000 |
The last thing I wonder is, can a receiver just pick up a DSSS signal and start applying the despreading code? I watched a YouTube video about this and the example involved multiplying the spreading code by the voltages of the composite waveform and averaging them. My system takes 16 chips to express 1 bit. Let’s say my demodulator starts on the 10th chip and goes on for 16 chips, getting 6 chips from this cycle and 10 from the next. If it keeps on like this, it will never fall into sync, and without being in sync it can’t get any real bits to help itself align. Sent from Windows Mail From: Richard Bell Sent: Friday, February 5, 2016 5:59 PM To: Henry Barton, address@hidden It will depend on how the rest of the radio is built up. I'm not familiar with VP9, but can I assume it's a spec on bits in a higher layer then Layer 1? Another words, you are assuming you have bits to correlate with, as opposed to wave shapes? You're getting into the difficulties of radio design now. You need to fully understand the needs of your system to make decisions like this. You don't have bits until you've synchronized and demodulated your signal. If you require some sort of FEC, it will need block alignment before you can decode it, so the correlator will need to be in the waveshape domain. You can still use the known VP9 headers to correlate to in this cas , but you wouldn't correlate to the bit version, you would correlate to the modulated version of those headers. P.S. Please reply to the mailing list, so others can see and reply if need be. Rich On Fri, Feb 5, 2016 at 2:53 PM, Henry Barton <address@hidden> wrote:
|
[Prev in Thread] | Current Thread | [Next in Thread] |