Aiying Yang

High Accuracy VLC Indoor Positioning System With Differential Detection

Recently, several positioning systems based on visible light communications (VLC) have been proposed, and most of them are based on received signal strength (RSS) because of its simplicity and high accuracy. In order to improve the accuracy further, a differential detection-based positioning algorithm is proposed. It can reduce positioning instability caused by light intensity fluctuation and the area outside the light-emitting diode (LED) cell can also be positioned. Experimental results show that the proposed method can improve the positioning accuracy from 10.0 to 4.0xa0cm and reduce the standard deviation from 9.0 to 2.5xa0cm. Meanwhile, the positioning accuracy outside the cell can reach 10.0xa0cm or less.

Indoor Positioning Method Based on Metameric White Light Sources and Subpixels on a Color Image Sensor

An indoor positioning method based on metameric white light sources and subpixels on a color image sensor is proposed in this paper. Metameric white light sources are obtained by merging multiple-color light-emitting diode (LED) chips with different intensity ratios. The output intensity ratios of subpixels on color image sensor at the receiver are employed to identify the respective metameric white light sources. Proof of concept experiments demonstrates that the average error of 2-D indoor positioning is 1.50 cm and 3-D indoor positioning is 3.58 cm. The indoor positioning system with the proposed method is cost effective and convenient because image sensors in nowadays available mobile devices can be utilized.

A Novel Noise-Insensitive Chromatic Dispersion Estimation Method Based on Fractional Fourier Transform of LFM Signals

We propose a novel chromatic dispersion (CD) estimation method by fractional Fourier transformation of linear-frequency modulation (LFM) signals. This method can measure inband and outband CD without using extra spectrum or timeslot resourses. In our method, LFM signals are added on quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16-QAM) signals with different center frequency offsets. The average estimation error of CD estimation is 0.234%, 0.25%, and 0.41% when the center frequency offset is 0, 15, and 40 GHz after five, 10, 15, and 20 spans standard single-mode fiber transmission. The results demonstrates that the maximum estimation error is always below 80 ps/nm for accumulated CD less than 24xa0000 ps/nm. For all scenarios, the CD estimation performance barely drops with optical signal-to-noise ratio from 10 to 25 dB and launch power from 0 to 6 dBm of five channel transmission.

Localization Accuracy Improvement of a Visible Light Positioning System Based on the Linear Illumination of LED Sources

As a new technique of indoor localization, visible light positioning has the advantages of high accuracy and antielectromagnetic interference. Received signal strength (RSS) based visible light positioning method is easy to implement because it requires simple hardware structure. However, in practical scenarios, the actual channel gain does not follow the ideal channel model. Instead of Lambertian channel model, some approximations have to be adopted to describe the relationship between received optical power and distance, and these approximations will cause deviation of positioning calculation. In this paper, an optical antenna based on freeform lens design is proposed to improve the accuracy of RSS-based positioning. With the optical antenna, the luminous intensity distribution is optimized, and the relationship between received optical power and distance becomes a simple linear relationship. Results show that RSS-based positioning system using freeform lens optical antenna can improve the positioning accuracy by 44%. Furthermore, the advantage of the optical antenna we designed for a visible light communication positioning system demonstrated uniformity under different conditions.

Joint OSNR and Interchannel Nonlinearity Estimation Method Based on Fractional Fourier Transform

We propose a novel joint optical signal noise ratio (OSNR) and interchannel nonlinearity (NL) estimation method by fractional Fourier transformation of linear-frequency modulation (LFM) signal. In our method, LFM signal acts as time domain pilot in front of the payload. Our method of OSNR estimation is insensitive to nonlinear noise of optical fiber. Lower OSNR estimation error is also achieved in comparison with differential pilot method. The interchannel NL measurement procedures are also simplified compared with previous work. We also provide a scientific way to calculate the reference interchannel NL. The interchannel NL estimation error of our method is lower than 1 dB for 9 channels transmission after 10 spans with launch power from 10 to 14 dBm.

Fusion Based on Visible Light Positioning and Inertial Navigation Using Extended Kalman Filters

With the rapid development of smart technology, the need for location-based services (LBS) increases every day. Since classical positioning technology such as GPS cannot satisfy the needs of indoor positioning, new indoor positioning technologies, such as Bluetooth, Wi-Fi, and Visible light communication (VLC), have already cut a figure. VLC positioning has been proposed because it has higher accuracy, costs less, and is easier to accomplish in comparison to the other indoor positioning technologies. However, the practicality of VLC positioning is limited since it is easily affected by multipath effects and the layout of LEDs. Thus, we propose a fusion positioning system based on extended Kalman filters, which can fuse the VLC position and the inertial navigation data. The accuracy of the fusion positioning system is in centimeters, which is better compared to the VLC-based positioning or inertial navigation alone. Furthermore, the fusion positioning system has high accuracy, saves energy, costs little, and is easy to install, making it a promising candidate for future indoor positioning applications.

Fusion of Visible Light Indoor Positioning and Inertial Navigation Based on Particle Filter

With the increasing demand for indoor positioning-based services, indoor positioning methods based on Bluetooth, Wi-Fi, ultra wide band (UWB), inertial navigation, and visual light communications (VLC) have been proposed. Considering the limitations of accuracy, cost and complexity, we propose a fusion positioning scheme integrating VLC positioning and inertial navigation base on particle filter. The experimental results demonstrated that the performance degradation caused by the multipath effect and light obstruction in VLC-based positioning and the cumulative error associated with inertial navigation are solved in the proposed fusion system. The accuracy of the fusion positioning system is in centimeters, which is two to four times better as compared to the VLC-based positioning or inertial navigation alone. Furthermore, the fusion positioning system has the advantages of high accuracy, energy saving, low cost, and easy to install, making it a promising candidate for future indoor positioning applications.

An improved diversity combining receiver for layered ACO-FOFDM in IM/DD systems

In this paper, an improved receiver based on diversity combining is proposed to improve the bit error rate (BER) performance of layered asymmetrically clipped optical fast orthogonal frequency division multiplexing (ACO-FOFDM) for intensity-modulated and direct-detected (IM/DD) optical transmission systems. Layered ACO-FOFDM can compensate the weakness of traditional ACO-FOFDM in low spectral efficiency, the utilization of discrete cosine transform in FOFDM system instead of fast Fourier transform in OFDM system can reduce the computational complexity without any influence on BER performance. The BER performances of layered ACO-FOFDM system with improved receiver based on diversity combining and DC-offset FOFDM (DCO-FOFDM) system with optimal DC-bias are compared at the same spectral efficiency. Simulation results show that under different optical bit energy to noise power ratios, layered ACO-FOFDM system with improved receiver has 2.86, 5.26 and 5.72xa0dB BER performance advantages at forward error correction limit over DCO-FOFDM system when the spectral efficiencies are 1, 2 and 3 bits/s/Hz, respectively. Layered ACO-FOFDM system with improved receiver based on diversity combining is suitable for application in the adaptive IM/DD systems with zero DC-bias.

Chromatic dispersion estimation based on heterodyne detection for coherent optical communication systems

Abstract. We propose an accurate and nondata-aided chromatic dispersion (CD) estimation method involving the use of the cross-correlation function of two heterodyne detection signals for coherent optical communication systems. Simulations are implemented to verify the feasibility of the proposed method for 28-GBaud coherent systems with different modulation formats. The results show that the proposed method has high accuracy for measuring CD and has good robustness against laser phase noise, amplified spontaneous emission noise, and nonlinear impairments.