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.

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.

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.

This paper investigates the deployment issues and analyzes the performance of a relay-assisted indoor visible light communications (VLC) system with dc-biased optical orthogonal frequency division modulation (DCO-OFDM). The study considers two light sources in an office environment. One light source works as the information source and is located at the ceiling while the other one works as the relay terminal, which usually is a desk light or a floor light. We analyze the general blockage in a room, discuss the path loss of the VLC channel, and compare received signal power from a line of sight (LOS) link and a non-LOS link. The constraints on the relay height in order to achieve LOS connection are investigated. Simplified optimal power allocation under illumination and blockage constraints is proposed. Bit error rate performance is analyzed and the required signal power is derived for the relay-assisted DCO-OFDM VLC system. The study shows that in a relay-assisted VLC system, the blockage of source to destination link has trivial influence on the overall system performance if relays are properly deployed.

In this letter, we apply code division multiple access (CDMA) technology to an integrated visible light communication and positioning (VLCP) system, which can recover the original user data and obtain the positioning information simultaneously. The two unipolar code sets with flexible construction methods, zero cross correlation (ZCC) code set and optical zero correlation zone (OZCZ) code set, are adopted and evaluated in the proposed system. Compared with the traditional spreading code set, these two code sets can directly suit to the VLCP system with higher transmission efficiency. In addition, the results show that zero correlation properties of OZCZ code set can effectively overcome non-perfect synchronization effects in the quasi-synchronous (QS) system. In a space of 6 m $\times $ 6 m $\times $ 5 m, the bit error rate (BER) of $1.58\times {10^{-3}}$ and average positioning error of 2.73 cm are successfully achieved in the synchronous system, while the BER of $1.60\times {10^{-3}}$ and average positioning error of 3.62 cm are realized in the QS system.

Due to the inherent tendency to be blocked by obstacles, reliability is a major challenge for visible light communication (VLC). The intelligent reflective surface (IRS) is an effective way to reduce or eliminate the influence of blockage in the VLC system. However, the complexity increases correspondingly due to complex shadow analysis when access points (APs), IRSs, and obstacles coexist. We proposed a robust layout optimization scheme for the IRS-VLC system to resist blockages. First, we model the random obstructions based on spatial geometry methods. Second, we build the optimization problem model considering consistent illumination, achievable data rate (ADR), the positions of the APs, and the directions of the IRS array. In order to achieve this objective, we develop an anti-occlusion method based on the non-dominated sorting genetic algorithm-II (NSGA-II) to get the Pareto front and use enhanced measurement functions (ASFs) to extract the best solution. Simulation results show that the proposed scheme works well in the IRS-VLC system. It is noteworthy that the rectangle layout has always demonstrated superior performance in the IRS-VLC system compared to other traditional layouts.