Subband Adaptation Employing Turbo Coded Modulation for OFDM Transmissions
OFDM传输中的子带自适应Turbo编码调制

To improve the spectral efficiency for wireless data transmissions, a subband-by-subband adaptive turbo coded modulation scheme based on capacity evaluation is proposed for Orthogonal Frequency Division Multiplexing (OFDM). The target is to optimize the overall throughput under constant transmit power and target Bit-Error-Rate (BER). Simulation results show that the adaptive OFDM scheme exhibits a 2.5-5dB Signal to Noise Ratio (SNR) gain relative to fixed threshold adaptive turbo coded modulation when the transmitter knows the perfect channel information. However, the adaptation performance is degraded due to the feedback delay in time-varying channels. Then, the investigation indicates that decreasing the amounts of subbands, and utilizing the diversity characteristic adequately in frequency domain of OFDM is an effective approach to reduce the performance degradation.