A power efficient adaptive modulation scheme over fading channel

We proposed a power efficient Quadrature Amplitude Modulation (QAM) modulation scheme for Rayleigh fading channel, which varies the number of modulation levels in accordance with the wireless fading channel variation. We first review the various kinds of adaptive modulation techniques, concerning their goals, methods and results. Then we proposed our system architecture and framing arrangement, using a unmodulated pulse to indicate the channel fading state, and 3 identical modulation identifiers to determine which modulation constellation is used in the remaining QAM symbols. After that we derived our MQAM signal constellation, and compare it with star-constellation MQAM. The result shows that it can greatly decrease the power consumption, and will achieve better Peak Power-Average Power performance. We present closed-form of adaptation boundaries for these constellations, computer simulation is also made to demonstrate our scheme optimizes transmission.

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