In this work, a novel positioning algorithm based on a long short term memory-fully connected network (LSTM-FCN) is proposed to improve the performance of an indoor visible light positioning (VLP) system. Using the proposed LSTM-FCN based positioning algorithm, the VLP system with a single light emitting diode (LED) and multiple photodetectors (PDs) was implemented. On this basis, the positioning performance of the established VLP system using proposed LSTM-FCN, traditional FCN and support vector regression (SVR) based algorithm is investigated and compared. It is demonstrated that the VLP system using the proposed LSTM-FCN based algorithm has better performance than that using other machine learning algorithms. As a result, an average positioning error of 0.92 cm and a maximum positioning error of less than 5 cm can be obtained for the established VLP system.

This paper presents a visible light positioning (VLP) system using a single light emitting diode (LED) and a novel receiver. In the proposed system, the receiver is composed of a horizontal photodetector (PD) and two tilted PDs, and a known calibration point is deployed to improve the accuracy of the positioning. Based upon the multi-PDs' relative positions and the received signal strength (RSS), the location of the receiver can be estimated regardless of the LED's and PDs' characteristics. The influences of tilted PDs on the positioning errors are discussed, i.e. the polar angle - and the difference - between two azimuth angles. The experimental results show that high accuracy can be achieved when α=20° and θ ranges from 30° to 90°. The average and maximum errors are 2.15cm and 4.01cm respectively in the case of α=20° and θ=45°. The proposed system avoids the inter-cell interference (ICI) caused by different transmitters and can be applied in scenarios with limited LEDs.

In this paper, a novel laser spot tracking algorithm that incorporates the Kalman filter with the continuously adaptive Meanshift algorithm (Cam-Kalm) is proposed and employed in an underwater optical wireless communication (UOWC) system. Since the Kalman filter has the advantage of predicting the state information of the target spot based on its spatial motion features, the proposed algorithm can improve the accuracy and stability of the moving laser spot tracking. A 2 m optical wireless communication experimental system with auto-tracking based on a green laser diode (LD) is built to evaluate the tracking performance of different algorithms. Experimental results verify that the proposed algorithm outperforms conventional tracking algorithms in aspects of tracking accuracy, interference resistance, and response time. With the proposed Cam-Kalm algorithm, the experimental system can establish an effective communication link, while the maximum tracking speed is 20 mm/s given the forward-error-correction (FEC) threshold.

In this paper, an integrated visible light communication and positioning (VLCP) code division multiple access (CDMA) system is proposed for recovering original user data and obtaining positioning information simultaneously. A generalized modification method for balanced bipolar code set is presented, which can be applied to VLCP-CDMA system with intensity modulation. Both modified bipolar code sets, zero correlation zone (ZCZ) code set and Walsh code set, are employed and evaluated in VLCP-CDMA systems. When considering synchronous and quasi-synchronous (QS) systems, it is demonstrated that the modified ZCZ code set with ideal zero correlation zone properties performs better communication and positioning performance than the modified Walsh code set by system simulations and experiments. As a result, a bit error rate (BER) of 1.8×10⁻³ and an average positioning error of 1.50 cm are successfully obtained by adopting modified ZCZ code set in a 4-user real-time VLCP-CDMA system. It will offer a promising solution to meet both communication and positioning requirements of future intelligent systems.

The relation between the peak-to-average-power-ratio (PAPR) reduction schemes and the transmission performance of the orthogonal frequency division multiplexing (OFDM) based visible light communication (VLC) system is experimentally investigated. The linear selective mapping (SLM) scheme and the nonlinear logarithmic companding scheme are optimized by considering both PAPR reduction and bit error rate (BER) performance. It is demonstrated that the logarithmic companding scheme, albeit providing larger PAPR reduction when compared to the SLM scheme, may result in worse BER performance due to the additional noise induced in its expanding process. Both numerical and experimental investigations show that, at the expense of increased complexity and reduced efficiency, the VLC system using the linear SLM scheme exhibits better BER performance compared to the system using the nonlinear logarithmic companding scheme. We show that for a 400-Mb/s transmission at a distance of 1 m, the BER can be reduced from 2.02 × 10⁻³ to 2.51 × 10⁻⁴ by using logarithmic companding scheme. By using the linear SLM scheme, the BER can be further reduced to 1.77 × 10⁻⁶.

In this paper, a novel adaptive feedback threshold (AFT) based demodulation for mobile visible light communication and positioning (VLCP) integrated system is proposed. The AFT can vary with the received signal without excessive fluctuation and support communication and positioning in mobile environment. For the VLCP integrated system with single light emitting diodes (LED) and multiple photodetectors (PDs), maximal ratio combining (MRC) and received optical power ratio (ROPR) based on the AFT is further achieved for communication and positioning with high performance, respectively. It is demonstrated that high credible communication and high accuracy positioning for the mobile integrated VLCP system can be realized by using the proposed AFT based demodulation. As a result, the implemented VLCP system with a moving speed of 1 m/s is evaluated experimentally. Average positioning error of 3.43 cm with 800 mA current and the bit error ratio (BER) with different currents are also obtained.