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[Discuss-gnuradio] Re: Measure BER
From: |
Patrick Strasser |
Subject: |
[Discuss-gnuradio] Re: Measure BER |
Date: |
Mon, 21 Jan 2008 16:16:04 +0100 |
User-agent: |
Thunderbird 2.0.0.9 (Windows/20071031) |
irene159 schrieb am 2008-01-21 16:01:
Hi!
2) When comparing data sent and data received, how can we detect bit lost in
order to avoid clock shifting? In other words, if I’m sending “11010110” for
example, and that the 4th bit is lost, a simple comparison will compare tx :
“11010110” with rx : “1100110”. Detecting a lost is easy because the number
of bits in reception will be inferior to the number of bits sent, but how
can continue to compare the rest correctly?
You would use a known sequence which you synchronize on. This can be a
pseudo-noise sequence or a long pattern. It should have low
autocorrelation except for a shift of 0. In hardware you would run the
sequence a slightly lower or higher rate and try to lock. If the
receiver-generated and the received sequence are approximately equal,
you get lock and run the sequence at the right speed.
In software? Dunno, is correlating fast and robust?
Patrick
--
Engineers motto: cheap, good, fast: choose any two
Patrick Strasser <patrick dot strasser at tugraz dot at>
Student of Telematik, Techn. University Graz, Austria