With the help of the rolling shutter mechanism of the complementary metal oxide semiconductor transistor (CMOS) camera, LED-camera based optical camera communication (OCC) system can obtain a data transmission rate much higher than a camera’s frame rate. This makes the OCC system one of the most potential branches of visible light communication system together with advantages like ease of use and almost cost free. However, limited by the fundamental film function of a camera, there exists a gap time between every two consecutively captured pictures. This brings an inevitable incident light signal loss problem, and limits the system throughput. Furthermore, the gap time vibrates during a camera’s working time, this makes the unidirectional OCC data link fragile to burst error. Aiming to fix the signal loss problem, and to obtain a reliable OCC data link, camera parameters like read out time, frame rate are analyzed, and a framing method is also proposed in this paper. In the proposed framing method, the original data is packed and sent sequentially. When compared to the related method like Hamming coding and Raptor coding, the proposed framing method has a higher system throughput, and has the capability to fix both the inter-frame and intraframe data loss problem. Numerical results show that the proposed framing method can effectively fix the data loss problem resulted from the gap time, fix the synchronization problem between the LED and camera, and increase the system throughput as well.
The NOMA-based VLC systems require channel state information (CSI) at the transmitter, which increases the computational complexity and feedback overhead. To tackle this challenge, this paper proposes an effective NOMA scheme for indoor VLC systems, in which the quantized CSI, instead of the full CSI, is used for user pairing and power allocation at the transmitter. Simulation results show that although the performance has some fluctuation in the single trial, the average performance of random trials is almost the same as that of the traditional scheme.
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