Non-linear feedback rate-adaptive modulation scheme in wireless communications over Rayleigh channels

In wireless communications, adaptive modulation is widely used to optimize the utilization of the limited resources. In this paper, a new rate adaptation method is proposed by an appropriate choice of feedback controller that drives the system states to equilibrium. The mathematical model of the adaptive modulation system is established for an ideal case with a perfect knowledge of the channel condition. The transmission rate is dynamically adjusted by a controller that is chosen to be a function of the system state feedback to achieve a stable the system under a given constraint. Finally, the imperfection of the channel state information is taken into account by treating the channel gain as a conditional random variable. Simulation results are presented to verify the analysis and it is also shown that the proposed rate adaptation scheme is robust against the imperfection of the feedback information due to Doppler effect.