Adaptive demodulation using Raptor codes: Analytical results and extension to fading channels

An adaptive demodulation scheme (ADM) for AWGN channel that does not have the disadvantages of the traditional rate-adaptive systems has been recently proposed. In ADM, the transmitter uses M-QAM signaling to send a fixed level modulated Raptor coded data stream. The receiver demodulates only a subset of the bits in the QAM symbol, where the size of the subset to be demodulated is dictated by the channel condition observed by the receiver. In this paper we extend the ADM to fading channels and derive a lower bound for the bit error rate performance of ADM. We also present simulated bit error rate results that support our analysis.