Signal transmission distance varies when users move randomly.By exploiting the sensitivity to distance in millimeter wave communication,a distance-adaptive modulation scheme is proposed.When the received Bit Error Rate(BER)exceeds the threshold,the user sends distance,antenna gain and average Signal to Noise Ratio(SNR)feedbacks to the base station,and the latter adjusts the modulation order and transmission power to ensure that the BER is below the threshold.The modulation order is determined according to the BER threshold,distance and SNR.And the transmit power is optimized by maximizing the Spectrum Efficiency(SE).Simulation results show that when the transmission distance is less than 300 m,256-order Quadrature Amplitude Modulation(256QAM)is used.When the transmission distance is between 300～500 m,64QAM modulation is used.And when the transmission distance is between 500～800 m,16QAM modulation is adopted.4QAM modulation is applied when the transmission distance is more than 800 m.Compared with existing millimeter wave modulation schemes such as Generalized Space Modulation(GSM-QAM),Pulse Position Modulation(PPM)and constant QAM,the proposed adaptive modulation scheme has the highest data rate under the same BER condition.
adaptive modulationtransmission distanceBERtransmit powermillimeter wave communication
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