Adaptive modulation transmission in high speed railway environment with QoS provisioning

Abstract

Robust adaptive modulation (AM) is a promising technique to improve the spectrum efficiency (SE) of high speed railway (HSR) communication system. Although robust AM transmission schemes with assumption of block fading channel have been extensively investigated, which are no longer valid in the fast time-varying channel due to the channel variation in frame duration. This paper investigates the optimum of AM transmission schemes design with different bit-error rate (BER) criteria for maximizing SE in HSR communication system. We propose a variable rate and variable power modulation scheme in a normal HSR environment, in which the closed-form expression of the power allocation policy is derived. Furthermore, considering the extract coverage requirements in a higher mobility scenario and different BER requirements, we propose two constant power and variable rate transmission schemes with probability BER constraint and average BER constraint. The effectiveness of the proposed AM transmission schemes are validated by extensive simulations. The effects of channel quality and Doppler shift on the performance of the proposed AM transmission schemes are evaluated.