Method to increase performance of secondary data in a hierarchical modulation scheme

In a digital data transmission system including a transmitter for transmitting transmit signals, a receiver comprising:

• a receiving unit including satellite signal detection means for detecting a first transmit signal transmitted from a first communication satellite and a second transmit signal transmitted from a second communication satellite, the first transmit signal produced when the transmitter modulates a primary data stream with a secondary data stream on a first carrier wave associated with the first communication satellite and the second transmit signal produced when the transmitter modulates the primary and secondary data streams on a second carrier wave associated with the second communication satellite;
• and
• at least one demodulator coupled to said receiving unit and configured to demodulate at least one of the first and the second transmit signals,
• wherein said receiving unit is operable to receive the first and the second transmit signals including secondary data comprising modulated data in the form of a phase offset relative to the modulated primary data.

A method of receiving transmitted data, the method comprising the steps of:

• detecting a first transmit signal, the first transmit signal transmitted from a first communication satellite and comprising a first level data and a second level data modulated on a first carrier wave associated with the first communication satellite;
• detecting a second transmit signal, the second transmit signal transmitted from a second communication satellite and comprising the first level data and the second level data modulated on a second carrier wave associated with the second communication satellite;
• detecting a third transmit signal, the third transmit signal transmitted from a terrestrial repeater and comprising the first level data and the second level data re-encoded on a third carrier wave associated with the terrestrial repeater;
• demodulating the first and the second transmit signals;
• interpreting the first transmit signal;
• and
• providing the interpreted signal to an output unit,
• wherein the first level data comprises one of QPSK, D-QPSK and pi/4 D-QPSK modulated data and includes a first number of information bits per symbol;
• and
• the second level data comprises BPSK modulated data in the form of a phase offset relative to the first level data and includes a second number of information bits that is lower than the first number of information bits.