Adaptive modulation and coding in 3G wireless systems

Abstract

We address the application of adaptive modulation and coding (AMC) for third-generation (3G) wireless systems. We propose a new method for selecting the appropriate modulation and coding scheme (MCS) according to the estimated channel condition. We take a statistical decision making approach to maximize the average throughput while maintaining an acceptable frame error rate (FER). We use a first-order finite-state Markov model to represent the average channel signal-to-noise ratio (SNR) in subsequent frames. The MCS is selected in each state of this Markov model (among the choices proposed in the 3G standards) to maximize the statistical average of the throughput in that state. Using this decision-making approach, we also propose a simplified Markov model with fewer parameters, which is suitable in systems where changes in the fading characteristics need to be accounted for in an adaptive fashion. Numerical results are presented showing that both of our models substantially outperform the conventional techniques that use "threshold-based" decision making.