Operating Manual Vol 1 - ES Documentation

SMIQDigital ModulationDifferential coding according to VDL is shown in the following table:Modulation symbol d n(binary, MSB, LSB)000 001 010 011 100 101 110 111Phase difference ∆ϕ 0° 45° 135° 90° 315° 270° 180° 225°Phase differential coding INMARSAT and PHASE DIFF correspond to system standards Inmarsat-Mand DVB according to ETS 300 429. The INMARSAT coding can generally be used for modulation typeswith 2 bit/symbol, such as QPSK. It uses the following algorithm.d0ndc0ndc1 n = [NOT (d1 n EXOR d0/ n)[(d1 n EXOR d0/ n)AND (d1 n EXOR dc1 n-1 )] ORAND (d1 n EXOR dc/0/ n-1)]INMARSATCODINGdc0/ n = [NOT (d1 n EXOR d0/ n) AND (d0/ n EXOR dc0/ n-1)] OR[(d1 n EXOR d0/ n-1) AND (d0/ n EXOR dc1 n-1 )]d1n(MSB)dc1n(MSB)2.10.1.5 Setting ConflictsAs already mentioned in the previous sections, the combination of the above modulation methods withmodulation parameters such as symbol rate, filtering and coding is limited. This limitation inevitablycauses setting conflicts if a parameter is changed which would lead to an impermissible combination.Table 2-10Examples of settings conflictsOriginal status Change by selection Conflict Solution1 MOD TYPE π/4DQPSKSYMBOL RATE 10 Msymb/s MOD TYPE→ GMSKGMSK is only possiblefor symbol rates up to7.5 Msymb/s.Reduction of symbol rate toa value of