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## [Discuss-gnuradio] TETRA phase adjustment bits

**From**: |
Harald Welte |

**Subject**: |
[Discuss-gnuradio] TETRA phase adjustment bits |

**Date**: |
Sun, 2 Jan 2011 21:02:09 +0100 |

**User-agent**: |
Mutt/1.5.20 (2009-06-14) |

Hi!
I know this is slightly off-topic, as it is not really related to gnuradio
(despite the USRP and gnuradio being used in my current experiments regarding
TETRA):
Does anyone know how the phase alignment bits in TETRA exactly work?
I'm reading ETSI EN 300 392-2 V3.2.1 and can find the definition at
Section 9.4.4.3.6.
So the phase adjustment bits need to be set to the negated sum of the
phase shift of two other bits in the burst.
Let's assume I'm using hc1, hc2 and thus look at the symbols 8 (bit 15+16) and
108 (bit 215+216).
If all of those four bits are 1 (like in the case of the synchronization
continuous down-link burst), there is a total phase shift of -6pi/4 (two times
-3pi/4).
But how do you correct such a phase shift in only a single adjustment symbol?
Using the two bits in the adjustment symbol, I can only apply +1pi/4, -1pi/4,
+3pi/4 or -3pi/4 ?!?
Any help is appreciated.
Regards,
Harald
--
- Harald Welte <address@hidden> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)

**[Discuss-gnuradio] TETRA phase adjustment bits**,
*Harald Welte* **<=**