Cooperative Communication Using Bit-Selective Adaptive Demodulation and Raptor Codes: The Gaussian Relay Channel Case

In this paper, the authors propose a cooperative communication system where every link adapts to the channel condition without any feedback, by using a recently proposed Adaptive De-Modulation (ADM) scheme. In ADM, the receiver demodulates only a subset of the bits from a Raptor coded Gray mapped M-QAM received symbol, where the number of demodulated bits depends on the channel condition. The ADM scheme, which was originally proposed for point to point communication, determines the most reliable bits using approximate decision regions obtained through a binary composite hypothesis test in the AWGN environment.