Adaptive Trellis-Coded Modulation over Predicted Flat Fading Channels

Link adaptation techniques aim at the efficient utilization of the scarce bandwidth of mobile radio links while satisfying the users’ demands. A competitive candidate for these purposes is an adaptive scheme based on the Trellis Coded Modulation (TCM) which increases the noise robustness without bandwidth expansion, in comparison with an uncoded scheme. We consider the optimum design of an adaptive scheme based on TCM and predicted Channel State Information (CSI) for flat Rayleigh fading channels, intended for the fast link adaptation. We answer the question of how to optimally adjust the data rate to maximize the spectral efficiency, subject to a Bit Error Rate (BER) constraint when imperfect CSI is taken into account. We derive an optimum solution based on the predicted Signal-to-Noise Ratio (SNR) and the prediction Mean Square Error (MSE) variance. Finally, we illustrate the performance of the adaptive TCM scheme utilizing seven 4-D trellis codes based on the International Telecommunications Union’s ITU-T V.34 modem standard.