On Sun, Jan 2, 2011 at 3:02 PM, Harald Welte <lafo...@gnumonks.org> wrote: > 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):
I think this list is a fine place to ask these kinds of questions. > 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, Have you looked at this paper? http://wsl.stanford.edu/~ee359/doppler2.pdf It provides a very nice description of pi/4 DQPSK and a receiver architecture for it. It might provide the answers you're looking for. Tom _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
