Dimmable optical orthogonal frequency division multiplexing (D-OFDM) is challenging to design for visible light communications, due to the high peak-to-average power ratio (PAPR) of OFDM signals and limited dynamic range of LEDs. Current D-OFDM schemes focused on the time domain and spatial domain designs of OFDM signals. This paper proposes a novel dynamic subcarrier activation based OFDM (DSA-OFDM) scheme. In DSA-OFDM, the number of activated subcarriers, as well as the signal's DC bias and the number of activated LEDs, is adjusted to provide both flexible dimming control and reliable communication. A generalized index modulation in both spatial domain and frequency domain is designed to select the activated subcarriers and activated LEDs. To show the influence of frequency domain design analytically, the closed-form expressions of the PAPR and the clipping noise of the DSA-OFDM signals are derived, and the optimized signal form is obtained accordingly. Simulation and numerical results show that the proposed scheme can outperform conventional dimming control schemes at various illumination levels in terms of the bit-error rate performance.

中文翻译：

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具有动态副载波激活的 VLC 可调光 OFDM 方案

由于 OFDM 信号的高峰均功率比 (PAPR) 和 LED 的动态范围有限，可调光光学正交频分复用 (D-OFDM) 对可见光通信的设计具有挑战性。当前的 D-OFDM 方案侧重于 OFDM 信号的时域和空间域设计。本文提出了一种新的基于动态副载波激活的 OFDM (DSA-OFDM) 方案。在 DSA-OFDM 中，激活子载波的数量以及信号的直流偏置和激活的 LED 数量都经过调整，以提供灵活的调光控制和可靠的通信。空间域和频域中的广义索引调制旨在选择激活的子载波和激活的 LED。为了分析显示频域设计的影响，推导了PAPR的闭式表达式和DSA-OFDM信号的限幅噪声，从而得到了优化的信号形式。仿真和数值结果表明，就误码率性能而言，所提出的方案可以在各种照明水平下优于传统的调光控制方案。