FIELD: obtaining information about signal quality and/or bit reliability for set of phase-modulated information characters. SUBSTANCE: phase of received phase-modulated signal is detected, phase estimate obtained is compared with closest expected value for shaping phase error signal. The latter is then displayed as signal quality estimate which is further averaged to set of character intervals to shape signal quality index. Finally, bit reliability information is generated by weighing cophasal (I) and quadrature (Q) components of phase estimate by signal quality index obtained. EFFECT: provision for determining signal quality and/or bit reliability information without using information about signal amplitude. 10 cl, 3 dwg
