Hongyao Chen

In this paper, a positioning algorithm based on the combination of K-means clustering and deep neural networks (DNNs) is first presented for multiple light emitting diodes (LEDs) integrated with visible light positioning (VLP) systems. We extracted the maximum value from the collected optical power of LEDs, utilizing the ratio of each optical power to this maximum optical power as the input training data. The experimental results demonstrate that the proposed algorithm outperformed the conventional DNN algorithm in terms of anti-jamming capability and positioning accuracy. In addition, the positioning accuracy of the proposed system reached a millimeter level, which is the highest experimental VLP accuracy, to the best of our knowledge.

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.

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, a practical scheme to achieve reconfigurable optical frequency comb (OFC) and Nyquist pulses generation based on two cascaded Mach–Zehnder modulators and a polarization control structure is theoretically analyzed and verified by simulation. A rectangular-shaped OFC with evolvable comb lines (4 to 8) was obtained. Since there is no filter built in the structure, the turntable comb spacing is also an inherent feature of the OFC. These properties make the OFC can be used to produce high quality Nyquist pulses with flexible pulse duration (25.6ps~14.4ps), duty cycle (11.5%~20.5%) and repetition rate (4GHz~40GHz). It is found that the sensitivity of the reconstruction process of the OFC and corresponding pulses is adjustable. By methods of mathematics, we expound the observed results and provide mathematical expressions about the relations between the optical sideband suppression ratio, modulation index, principle polarization direction and sensitivity. Moreover, a proof-of-concept experiment of the OFC generation is carried out and the results are consistent with the theoretical ones, which indicates the potential of our work to generate user-friendly reconfigurable OFC and Nyquist pulses demanded in microwave photonics, optical communications, all-optical sampling and light storage applications.

In this paper, a real-time frequency-octupling photonic generator scheme that can realize stable microwave signal generation by using two incoherent optical sources without the support of phase-locked loops is successfully demonstrated, which proves that the improved feed-forward modulation is a feasible method for reducing phase noise. The principle of the proposed generator is illustrated by theory, simulation, and experiment. A 16GHz stable microwave signal with a bandwidth less than 0.2MHz is generated by using a 2GHz driving signal, and a 64GHz optical millimeter wave signal is obtained by using an 8GHz driving signal. Furthermore, a purity 320GHz terahertz wave signal is obtained by simulation based on the same principle and setup. The results show that the terahertz signal has good transmission characteristic and fine eye diagram in the 40.5km fiber link. In addition, to enhance the flexibility and feasibility of the generator, the feasible range of the modulation index and a signal enhancement method are also explored.