可见光通信系统的低复杂度预编码矩阵设计

Low Complexity Precoding Matrix Design for Visible Light Communication Systems

在可见光通信(VLC)系统中,发射端调制信号的幅度必须保持非负才能驱动LED发光,导致VLC系统的可达速率公式与传统射频通信系统存在较大差异。此时,传统最大化可达速率的预编码矩阵设计方法不再适用。针对该问题,提出了一种适用于多输入多输出VLC系统的预编码矩阵设计方法。首先,基于严格卡罗需库恩塔克条件求解出特征信道功率分配表达式。然后,根据注水算法的思想为性能较好的子信道分配较大功率。通过对特征信道功率的取值次序进行约束,本方法能在逼近最优可达速率的同时具备低复杂度特点。仿真结果表明,相比现有预编码矩阵设计方法,本方法的可达速率指标有显著提升。

In visible light communication(VLC)systems,the amplitude of the modulated transmit signal must be nonnegative to drive lightemitting diodes to illuminate,resulting in a very different achievable rate formula of VLC system compared to that of a traditional radio frequency system.Therefore,the traditional precoding matrix design method for maximizing the achievable rate is no longer applicable.In terms of the issue,this study proposes a precoding matrix design method for multiple input multiple output VLC systems.First,it is based on the strict KarushKuhnTucker conditions to achieve the eigenchannel power allocation expression.Then,the waterfilling algorithm ensures that the subchannels with better performance are allocated higher power.The method can achieve the optimal achievable rate with low complexity characteristics by constraining the order of eigenchannel power values.The simulation results show that the achievable rate index of the method is significantly improved,compared with the existing precoding matrix design methods.