Patent ID: 7477694

Claim:
A system, comprising: a transmitter configured to transmit a signal, the transmitter including a 2 P -state quadrature amplitude modulation (QAM) submodulator configured to receive an original data stream and to produce an encoded data stream of symbols, wherein P is a length of sequence of tones, a M-ary frequency shift keying modulator configured to receive the encoded data stream and to modulate each symbol as the length four sequence of tones, each tone of the length four sequence having a frequency corresponding to one of M frequencies, wherein M is a number of frequencies, and each unique length four sequence of tones corresponding to a respective unique symbol, and a mechanism for transmitting each of the length four sequence of tones as the signal; and a receiver configured to receive the signal and to incoherently demodulate the signal to recover the original data stream, the receiver including a M-ary frequency shift keying demodulator configured to receive the signal and to demodulate the signal to produce a demodulated sequence of tones, each tone corresponding to one of the M frequencies, and a 2 P -state quadrature amplitude modulation (QAM) subdemodulator configured to receive the demodulated sequence of tones, to correlate the demodulated sequence of tones into the encoded data stream of symbols, and to decode the encoded data stream of symbols to produce the original data stream.