Markov channel-based feedback schemes for adaptive modulation systems

In adaptive modulation systems,, it is widely assumed that the feedback channel is error-free by employing sophisticated error-control codes and ARQ signaling. However, since feedback is sent over a wireless channel, a heavy price may be paid to justify this assumption. In this paper, we first analyze system performance given additive noise and fading on the feedback channel. Then, by utilizing the Finite-State Markov Channel model for a slowly fading Rayleigh channel, we design differential and full-state feedback schemes to correct most of the errors caused by an AWGN channel. For a fading feedback channel, a Markov-based scheme is designed with a threshold level, below which feedback decisions are deemed unreliable. The resulting system performance in terms of the spectral efficiency and bit error rate (BER) is comparable to the ideal case of an error-free feedback channel.