用户移动性下的毫米波自适应调制策略研究

Mobility-based Millimeter Wave Adaptive Modulation Strategy

当用户移动时,信号的传输距离随之变化。基于此,利用毫米波通信对传输距离的敏感性提出了距离自适应调制策略。当用户接收误码率(Bit Error Rate,BER)超过门限时,用户通过反馈信道请求基站调整信号调制阶数和发送功率来保证BER在门限以下。基站根据用户反馈的BER门限、传输距离以及天线增益等确定调制阶数,通过最大化频谱效率(Spectrum Efficiency,SE)得到最优发送功率。通过仿真得出,当传输距离小于300 m时,采用256阶数的正交幅度调制(256-order Quadrature Amplitude Modulation,256QAM);距离在300~500 m时,采用64QAM调制;距离在500~800 m时,采用16QAM调制;距离大于800 m时,采用4QAM调制。比较已有的毫米波广义空间调制(Generalized Space Modulation-QAM,GSM-QAM)、脉冲位置调制(Pulse Position Modulation,PPM)和固定QAM调制策略,所提出的改进的自适应调制策略在保证BER的前提下,数据率最高。

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.