Grouped modulation scheme for led array module in a visible light Communication system
Grouped modulation is proposed to generate multiple-level optical signals and enhance the info rate for LED-array-module-based indoor visible lightweight Communication systems. By dividing LEDs in an array module into n groups and driving different groups with separate circuits, 2nlevel modulation can be realized with binary modulation for every cluster. The maximum driven current for respective circuits is reduced compared to that of the same multiple-level PAM for which an array module is driven by a single circuit. The limitation to modulation bandwidth of an LED array module, caused by the product of gain and bandwidth of its driven circuit, is alleviated. The benefit of grouped modulation is that the performance of a visual light Communication system can be improved with the medium complexity of driven circuits for various teams. Proof-of-concept experiments demonstrate that the information rate can be enhanced up to fifty Mb/s with three LEDs (LED465E provided by THORLABs) by a pair of-grouped OOK modulation and the transmission length is one.zero m with a small amount error rate but 1e-vi. Meanwhile, the utmost current of driven circuits for two teams is reduced by a third compared to a circuit driving 3 LEDs as a full. The enhancements can be further increased greatly if a larger-sized LED array module of hundreds or thousands of LEDs is split into a lot of teams. Grouped modulation can also be extended to other formats such as pulse position modulation and overlapping pulse position modulation.
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