A Spectrum Effective Adaptive Modulation and Coding Scheme for OFDM System

With variable code, variable power and variable rate, link adaptation has been shown to have significant benefits for high-speed wireless data transmission. In this paper, an adaptive modulation and coding (AMC) scheme applied to variable bit rate services is proposed for orthogonal frequency division multiplexing (OFDM) system. The objective is to maximize the spectral efficiency by adaptively selecting the code and allocating rate and power over the frequency band under the packet error rate constraint. Following analysis on rate-compatible punctured convolutional codes and linking adaptive techniques in OFDM, a sub-optimal AMC scheme with uniform power allocation is investigated. We realize the rate allocation by setting the instantaneous bit error rate to the average bit error rate which varies over different coding schemes. Simulation results indicate that the proposed scheme exhibits 4~8dB signal-noise-ratio gain relative to non-adaptive scheme. Compared to optimal scheme, the proposed scheme shows negligible loss at high SNR scenarios while the implementation complexity can be reduced significantly.