针对室内可见光通信调制技术问题, 提出翻转光无载波幅度相位调制和单极性光无载波幅度相位调制两种功率有效的调制方案, 二者分别采用“正、负模块极性分组”以及“零值位置极性编码”方法实现信号单极性处理, 以满足可见光通信“强度调制/直接检测”的要求.基于朗伯辐射模型, 考虑到高斯背景光噪声的可见光直射传输信道, 推导了包括直流偏置光无载波幅度相位调制在内的三种调制方案的误比特率闭式表达式, 仿真验证了其准确性.在此基础上, 分析比较了三者频带利用率, 讨论了信道参量对光无载波幅度相位调制系统误码性能的影响, 结果表明, 在5 m×5 m×3 m的室内场景下, 与发射机辐射角为30°和45°相比, 0°时的系统误码性能分别优于6.9 dB和29.9 dB; 收发机距离为1 m时, 误码性能比2 m时改善近12 dB.

Aimed at the modulation technique used in indoor visible light communication systems, two power efficiency schemes named flip optical carrierless amplitude and phase modulation as well as unipolar optical carrierless amplitude and phase modulation are proposed in this paper. To ensure the signal be suitable for an intensity modulation/direct detection system, the first scheme forms the so called positive block and negative block based on the bipolar signal, the second utilizes a pair of samples including a zero level to mark signal polarity. Lambertian reflection model is introduced in visible light channel which is corrupted by additive white Gaussian noise. The theoretical bit error rate of the three modulation schemes involving DC biased optical carrierless amplitude and phase modulation over visible light transmission channel is derived. Meanwhile, the performance of bandwidth efficiency is analyzed and compared. Monte Carlo simulations is evaluated to corroborate the analysis. In addition, the effects of channel parameters on the system performance are discussed in this paper. The simulation results show that the bit error rate performances improve 6.9 dB and 29.9 dB when the radiation angle of LED is 0° compared with 30° and 45° in the room measuring 5 m×5 m×3 m. As the distance between the transmitter and receiver reduced from 2 m to 1 m, the optical carrierless amplitude and phase modulation system can obtain better performance of approximately 12 dB.