Performance Improvement on 64-QAM Multicarrier with Closed-Loop Rotate Modulation

To improve performance in the 64-QAM multicarrier communication system, we propose a new method, closed-loop rotate modulation. The closed-loop process requires feedback channel information in the form of complex quantities that contain information on the gain and delay of the channel. Based on the purpose of distortionless transmission, we can get the equation in the closed-loop rotate modulation method on the multi-carrier system at the transmitter side. From the simulation results, with the application of closed-loop rotate modulation, the output signal of the multicarrier demodulator is exactly the same as the transmission signal. On the probability of error curve generated, the application of closed-loop rotate modulation can coincide with the system performance if only disturbed by the AWGN channel. Terms so that the algorithm can work optimally, the speed of updating feedback must be faster than changes in channel fluctuations and channel feedback works perfectly. The simulation results also show that although channel information feedback is not perfect, but still can produce a good performance, the more accurate channel feedback will result in a better probability of error. Another advantage of the scheme that we propose is that the transmission process of a multi-carrier system does not use guard intervals, so the efficiency of the data is maximized.