BER performance study for optical OFDM of optical camera communication

In this article, different forms of optical orthogonal frequency division multiplexing (OFDM) were observed which were suitable for optical camera communication (OCC) systems. This research aims to establish the bit error rate (BER) versus signal-to-noise ratio (SNR) of the OCC system. This research will focus on OCC systems and the design that produces the noise of the clipping but will gain SNR as a whole if an optimum clipping factor is chosen. The BER versus SNR analysis was investigated for the different clipping factors 0.7, 1.4, and 2.6. The BER performance of the asymmetrically clipped optical OFDM (ACO-OFDM) was also compared with the direct current optical OFDM (DCO-OFDM) to show the suitable effectiveness of the proposed approach. ACO-OFDM was considered to be better due to lower bit loading, but DCO-OFDM was efficient for higher SNR values. This was because the DC bias used was inefficient in terms of optical capacity, while ACO-OFDM used only half of the subcarriers to transmit the information. Moreover, ACO-OFDM two-dimensional half-subcarriers of mapping rule would introduce the clipping noise to its unused 2D subcarriers, although further data can be provided by the 2D DCO-OFDM mapping rule

Photographic Noise Performance Measures Based on RAW Files Analysis of Consumer Cameras

[EN] Photography is being benefited from the huge improvement in CMOS image sensors. New cameras extend the dynamic range allowing photographers to take photos with a higher quality than they could imagine one decade ago. However, the existence of different technologies make more complicated the photographic analysis of how to determine the optimal camera exposure settings. In this paper, we analyze how the different noise models are translated to different signal to noise SNR curve patterns and which factors are relevant. In particular, we discuss profoundly the relationships between exposure settings (shutter speed, aperture and ISO). Since a fair comparison between cameras can be tricky because of different pixel size, sensor format or ISO scale definition, we explain how the pixel analysis of a camera can be translated to a more helpful universal photographic noise measure based on human perception and common photography rules. We analyze the RAW files of different camera models and show how the noise performance analysis (SNR and dynamic range) interact with photographer's requirements.Igual García, J. (2019). Photographic Noise Performance Measures Based on RAW Files Analysis of Consumer Cameras. Electronics. 8(11):1-30. https://doi.org/10.3390/electronics8111284S130811Camera Imaging Products Association: Digital Cameras Reporthttp://cipa.jp/stats/dc_e.htmlGye, L. (2007). Picture This: the Impact of Mobile Camera Phones on Personal Photographic Practices. Continuum, 21(2), 279-288. doi:10.1080/10304310701269107Bhandari, A., & Raskar, R. (2016). Signal Processing for Time-of-Flight Imaging Sensors: An introduction to inverse problems in computational 3-D imaging. IEEE Signal Processing Magazine, 33(5), 45-58. doi:10.1109/msp.2016.2582218Wang, J., Zhang, C., & Hao, P. (2011). New color filter arrays of high light sensitivity and high demosaicking performance. 2011 18th IEEE International Conference on Image Processing. doi:10.1109/icip.2011.6116336Chan, C.-C., & Chen, H. H. (2018). Improving the Reliability of Phase Detection Autofocus. Electronic Imaging, 2018(5), 241-1-241-5. doi:10.2352/issn.2470-1173.2018.05.pmii-241Kirkpatrick, K. (2019). The edge of computational photography. Communications of the ACM, 62(7), 14-16. doi:10.1145/3329721Koppal, S. J. (2016). A Survey of Computational Photography in the Small: Creating intelligent cameras for the next wave of miniature devices. IEEE Signal Processing Magazine, 33(5), 16-22. doi:10.1109/msp.2016.2581418CMOS Image Sensor Market: Forecasts from 2019 to 2024https://www.knowledge-sourcing.com/report/cmos-Image-sensor-marketPhotonstophotos.nethttp://photonstophotos.netDxomarkhttp://dxomark.comBoukhayma, A., Peizerat, A., & Enz, C. (2016). Temporal Readout Noise Analysis and Reduction Techniques for Low-Light CMOS Image Sensors. IEEE Transactions on Electron Devices, 63(1), 72-78. doi:10.1109/ted.2015.2434799Vargas-Sierra, S., Linán-Cembrano, G., & Rodríguez-Vázquez, A. (2015). A 151 dB High Dynamic Range CMOS Image Sensor Chip Architecture With Tone Mapping Compression Embedded In-Pixel. IEEE Sensors Journal, 15(1), 180-195. doi:10.1109/jsen.2014.2340875Hassan, N. B., Huang, Y., Shou, Z., Ghassemlooy, Z., Sturniolo, A., Zvanovec, S., … Le-Minh, H. (2018). Impact of Camera Lens Aperture and the Light Source Size on Optical Camera Communications. 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP). doi:10.1109/csndsp.2018.8471766Hirsch, J., & Curcio, C. A. (1989). The spatial resolution capacity of human foveal retina. Vision Research, 29(9), 1095-1101. doi:10.1016/0042-6989(89)90058-8ColorChecker Classic Charthttps://xritephoto.com/colorchecker-classicWang, F., & Theuwissen, A. (2017). Linearity analysis of a CMOS image sensor. Electronic Imaging, 2017(11), 84-90. doi:10.2352/issn.2470-1173.2017.11.imse-191Wakashima, S., Kusuhara, F., Kuroda, R., & Sugawa, S. (2015). Analysis of pixel gain and linearity of CMOS image sensor using floating capacitor load readout operation. Image Sensors and Imaging Systems 2015. doi:10.1117/12.2083111Wang, F., Han, L., & Theuwissen, A. J. P. (2018). Development and Evaluation of a Highly Linear CMOS Image Sensor With a Digitally Assisted Linearity Calibration. IEEE Journal of Solid-State Circuits, 53(10), 2970-2981. doi:10.1109/jssc.2018.285625

Optical Camera Communications: Principles, Modulations, Potential and Challenges

Optical wireless communications (OWC) are emerging as cost-effective and practical solutions to the congested radio frequency-based wireless technologies. As part of OWC, optical camera communications (OCC) have become very attractive, considering recent developments in cameras and the use of fitted cameras in smart devices. OCC together with visible light communications (VLC) is considered within the framework of the IEEE 802.15.7m standardization. OCCs based on both organic and inorganic light sources as well as cameras are being considered for low-rate transmissions and localization in indoor as well as outdoor short-range applications and within the framework of the IEEE 802.15.7m standardization together with VLC. This paper introduces the underlying principles of OCC and gives a comprehensive overview of this emerging technology with recent standardization activities in OCC. It also outlines the key technical issues such as mobility, coverage, interference, performance enhancement, etc. Future research directions and open issues are also presented

Impact of Camera Lens Aperture and the Light Source Size on Optical Camera Communications

In this paper, we investigate the defocused image in optical camera communications and the use three parameters including half power full width, maximum intensity, and slopes of the hazy area to characterize the blurred image. The paper outlines theoretical analysis for the blurry image using the captured image of the light source and the circle of confusion. An experimental test bed is developed to investigate the effect of width, height and slopes of the image of defocusing of the camera. Results show that for a larger aperture, which results in higher received power, the interference level between two light sources is increased due to defocusing of the camera

Single and Multi-Hop Vehicular Visible and Infrared Light Communications

Visible light communications (VLC) have been proposed as a complementary technology in vehicular networks due to its several merits including high security, high scalability than RF technology. Notably, the RF technology established for vehicular networks best known as the dedicated short-range communications, supports many applications but doubts still exist on the capability of this technology to meet the low latency (where not more than 20 ms is required for pre-crash sensing and cooperative collision mitigation) and high reliability requirements in intelligent transport systems (ITS), when considering issues such as network outages as well as security issues. Of interest is the wide increase in the use of light emitting diode (LED)-based vehicle and traffic lights, and cameras in vehicles (rear and dashcams), traffic and security cameras, hence opening more opportunities for the VLC technology as part of ITS. Remarkably, camera-based VLC (i.e., optical camera communications) offers even further capabilities such as vehicle localization, motion and scene detection and pattern recognition. However, the VLC system has few challenges that needs addressing for the practical implementation of this technology as part of ITS. Consequently, this thesis focuses on addressing the key challenges and proposing novel technical analytical and experimental solutions. Firstly, increasing the robustness to sunlight induced noise is one of the major challenges in vehicular VLC, hence this thesis proposes an infrared (IR) transmission, as the amount of solar irradiance is lesser in the IR band than in the visible band. Performance of the proposed scheme is validated through numerical simulations with realistic emulated sunlight noise from empirical measurement. Investigations on the effects of turbulence with aperture averaging and fog on vehicular VLC is also carried out via experiments. Secondly, increasing the communication range is another major challenge, consequently the feasibility of using different vehicle taillights (TLs) as the VLC transmitter are evaluated via simulations based on empirical measurements of the radiation characteristics and transmit powers of the TLs. Results obtained indicate that, only a very low link span of 89 m at the forward error correction (FEC) bit error rate (BER) limit of 3.8 × 10-3, compared to 4.5, 5.4, and 6.3 m for the BMW vehicle-based TL at data rates of 10, 6, and 2 Mbps are achieved under realistic sunlight conditions. While, to increase the communication distance of camera-based VLC links, reducing the spatial bandwidth of the camera in its out of focus regions is proposed, mathematically analysed, and experimentally demonstrated where up to a 400 m link span at a 100 % success reception rate is achieved at a data rate of 800 bps, which is the longest so far reported. Relay-assisted links are also investigated using amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes under the emulated sunlight noise. A mathematical and simulation-based system model is developed, where different transmitter/receiver geometries are considered and AF and DF schemes. Results obtained via simulations shows that the DF scheme is a suitable candidate for vehicular VLC connectivity under emulated sunlight noise, offering at the FEC BER limit of 3.8 × 10-3 up to 150 % increase in the link distance by the end of the 2nd hop. Proof of concept experimental demonstration of AF and DF schemes for vehicular VLC are also carried out showing that DF is the preferred option. Moreover, insights are provided into the impact of various system parameters on the relay-assisted links. Finally, increasing the mobility of the vehicular VLC system is another major challenge, hence analysis on the required angular field of view (AFOV) for vehicular links considering necessary geometry parameters is investigated. Mathematical expressions to determine the required AFOV based on key system parameters are also derived. Furthermore, the relevance of the choice of the receiver parameters for an enhanced AFOV is also analysed, consequently a means to mitigate the effects of beam spot offset induced power losses at the photodiode caused by the misalignment of the transmitter and imaging receiver is proposed