室内可见光多维CAP空间调制

Spatial Modulation Based on Multi-dimensional Carrierless Amplitude and Phase for Indoor Visible Light Communication System

针对室内可见光通信(VLC)光链路发射源(LED器件)有限的调制带宽问题,基于多维无载波幅度相位调制(CAP)技术,提出一种频带利用率高效的光空间调制方案(OSM-CAP)。OSM-CAP系统将输入信息序列分成两部分,一部分进行空域映射即空间调制,其结果用来选择激活的LED;另一部分进行信号域映射,即CAP调制。其中,CAP调制采用序列二次规划算法求取的时域正交多维CAP滤波器组实现。对于采用强度调制/直接检测(IM/DD)的VLC系统,该CAP信号还将进行单极化处理,文中提出两种相应的解决方案,即采用添加直流偏置(OSM-DCO/CAP方案)和零值位置极性编码(OSM-U/CAP方案)。基于朗伯体辐射模型,且可见光背景噪声建模为加性高斯白噪声,推导了OSM-DCO/CAP、OSM-U/CAP调制方案的误码率理论解,仿真验证了其准确性。在5 m×5 m×3 m的室内场景下,探讨了无载波幅度相位调制维度以及接收机个数、发射机间距、收发平面距离以及链路遮挡情况等信道参数对系统性能的影响。结果表明,星座调制阶数相同时,CAP调制维度越高,误码性能越好;接收机个数增多、发射机间距加大以及收发平面距离减小与系统可靠性存在正相关关系;链路存在遮挡情况时,会提高信道间的差异性,改善系统性能。

Aimed at the limited bandwidth of LED devices used in a visible light communication(VLC)system,a bandwidth efficiency spatial modulation scheme based on multi-dimensional carrierless amplitude and phase named OSM-CAP was proposed in this paper.The bit sequence was divided for two parts in OSM-CAP system,a part was modulated to represent the spatial information and then used to select the active LED,another part convolved with multi-dimensional CAP filter banks acquired by solving a quadratic programming algorithm,and then some modifications were performed to obtain unipolar signal in OSM-CAP VLC system because only real and positive signals could be intensity modulated.According to Lambertian reflection model and considering light of sight link corrupted by additive white Gaussian noise,the theoretical bit error rate(BER)of OSM-DCO/CAP and OSM-U/CAP was derived and corroborated by Monte Carlo simulations.Meanwhile,the effects of the dimensionality of CAP filter banks and the channel parameters on the system performance were evaluated in the room in size of 5 m×5 m×3 m.The numerical results show that the higher dimension of filter banks,the better error performance of OSM-CAP VLC system.In addition,increasing the number of the receiver,enlarging the separation distance between two LEDs,decreasing the distance between the transmitter and receiver,and using something to block the transmission link,can improve the system reliability.