Patent ID: 7609614

Claim:
A demodulator apparatus for use in a wireless multiple-access communication system where a headend communicates with a plurality of wireless subscriber stations, and the plurality of wireless subscriber stations use frequency division multiplexing to share an uplink frequency bandwidth, the demodulator apparatus comprising: a channelizing filter bank that separates a collection of frequency division multiplexed uplink signals into a plurality of noncoherently demodulated channel signals including a particular noncoherently demodulated channel signal, wherein the noncoherently demodulated channel signals are noncoherently demodulated complex-valued channel signals and the particular noncoherently demodulated channel signal is a particular noncoherently demodulated complex-valued channel signal; a noncoherent detector configured to detect information from the particular noncoherently demodulated channel signal, the noncoherent detector including an I/Q demodulator that noncoherently extracts first and second real-valued baseband signals respectively from an in-phase carrier signal and a quadrature-phase carrier signal, and the particular noncoherently demodulated complex-valued channel signal comprises the first and second real-valued baseband signals; and a trellis decoder responsive to the particular noncoherently demodulated complex-valued channel signal, wherein the trellis decoder includes: a set of composite states including a first composite state that represents information related to first and second simple states, wherein the first simple state corresponds to a first state of a first real-valued trellis path of a first real-valued message signal and the second simple state corresponds to a first state of a second real-valued trellis path of a second real-valued message signal; and a branch metric calculator that calculates a respective branch metric for each of a plurality of composite state transitions, wherein each composite state transition of the plurality of composite state transitions respectively leads from the first composite state to a respective second composite state, and each respective second composite state represents information related to third and fourth simple states, wherein the third simple state corresponds to a next state after the first state of the first real-valued trellis path and the fourth simple state corresponds to a next state after the first state of the second real-valued trellis path; and wherein the particular noncoherently demodulated complex-valued channel signal corresponds to a quadrature-multiplexed continuous phase modulation (QM-CPM) signal, and the first and second real-valued message signals are related to respective first and second continuous-phase baseband signals though a complex-to-real mapping function.