Visible light communication has advantages such as high speed, broadband, green, safety, and low cost. Moreover, visible light communication is not subject to electromagnetic interference, so it is useful in a wide range of application scenarios such as aviation, hospitals, and mines. However, due to the limited spectrum and coverage provided by a single LED, multiple LED coverage is adopted in the indoor layout to provide seamless connection, which also brings spectrum interference in overlapping areas. This paper proposes an indoor visible light interference suppression method based on the backward forward markup (BFM) algorithm. This method not only solves the problem of spectral interference, but also improves throughput while ensuring user fairness. The simulation results show that the BFM algorithm has brought significantly improvements in various aspects, with system throughput increased by 75% and fairness factor increased by 0.3.
Optical fiber bus technology is an important research direction in communication systems of electronic devices in special vehicle platforms. According to the requirements for communication quality between devices in special vehicle platforms, an optical fiber bus based on gigabit passive optical network topology is proposed. A data cache-based predictive weighted interpolated polling dynamic bandwidth allocation method is presented and investigated for the optical fiber bus’s upstream bandwidth allocation. The network controller establishes a weighted buffer area for the communication requirements in the polling period according to the type and data volume of the network terminal (NT) data stream and dynamically allocates the bandwidth of each optical NT to better meet the communication requirements for different data within the special device platform. Verification is done by means of OPNET software simulation and the establishment of a NT simulation test system in the laboratory. This proves that the proposed dynamic bandwidth allocation algorithm can reduce the end-to-end delay of RS422 port data by more than 50% and meet the Ethernet and controller area network port data delay requirements.
In the indoor visible light communication (VLC) system, the light source has the dual function of illumination and communication. Due to the different size of indoor space and indoor facilities, it will inevitably lead to different indoor light power distribution. In order to achieve the optimal communication effect, the layout of the light source must be reasonably designed so that the receiving power distribution is relatively uniform on the same horizontal plane in the room. The current layout methods are mostly based on the square plane three-dimensional space, while the layout methods of the rectangular plane three-dimensional space are rarely studied. In this paper, a room with size 5m×4m×3m is used as a model. Firstly, according to the shock response principle, the optimal layout of four LED lights is obtained through theoretical calculations, so that the received light power fluctuation in the z=h plane in this room is minimized. Then, according to a set of simulation parameters, the theoretical optimal layout with the minimum fluctuation of receiving optical power in the h=0.75m plane in the room is calculated, and then Matlab is used to simulate the received optical power distribution of the plane under different layouts. The simulation results are consistent with the theoretical calculations. Finally, the illumination distribution under the optimal layout is calculated to verify that the designed optimal layout meets the international illumination standards. The light source layout model designed in this paper not only meets the illumination standards, but also ensures the reliability of communication. It provides an optimization method for the layout of indoor visible light communication LED light source.
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