Adaptive transmission scheme for OFDM system

Conventional wireless communication system capacity is limited by the worst channel parameters which determine the transmission mode. In this paper, a novel adaptive transmission scheme used in OFDM system is proposed to increase the system capacity by adaptively adjusting the transmission mode depending on channel parameters. In FDD mode, channel estimation is needed to feedback to the transmitter, which brings delay. Channel parameters of current frame are used to determine the modulation scheme of the next frame. When the multiplicity of Doppler frequency and frame length is below 0.022, current channel parameters can be used to determine the modulation mode of the next frame. When the multiplicity of Doppler frequency and frame length is below 0.2, the prediction of the channel parameters of the next frame is used for modulation mode. When the multiplicity of Doppler frequency and frame length is above 0.2, average SINR is used to determine the modulation mode. Simulations results show that this adaptive modulation scheme can achieve good performance with low complexity.