MODULATION SCHEME FOR HIGH SPEED MUD PULSE TELEMETRY WITH REDUCED POWER REQUIREMENTS

A method for transmitting data from a downhole location to a location at the surface of the earth includes: receiving data using a modulator disposed at the downhole location on a drill tubular in a borehole penetrating the earth and modulating the data using offset quadrature phase shift keying (OQPSK) and smooth transitions between phase shifts to produce a series of two-bit symbols having smooth transitions in transition intervals between phase shifts of both in-phase and quadrature-phase components of the OQPSK modulated data. The method further includes transmitting the series of two-bit symbols as an acoustic signal in drilling fluid disposed in the borehole using a mud-pulser, receiving the acoustic signal using a receiver disposed uphole from the downhole location; and demodulating the acoustic signal using a demodulator coupled to the receiver to provide demodulated data.