Design and Implementation of a Novel Compatible Encoding Scheme in the Time Domain for Image Sensor Communication

Abstract

This paper presents a modulation scheme in the time domain based on On-Off-Keying and proposes various compatible supports for different types of image sensors. The content of this article is a sub-proposal to the IEEE 802.15.7r1 Task Group (TG7r1) aimed at Optical Wireless Communication (OWC) using an image sensor as the receiver. The compatibility support is indispensable for Image Sensor Communications (ISC) because the rolling shutter image sensors currently available have different frame rates, shutter speeds, sampling rates, and resolutions. However, focusing on unidirectional communications (i.e., data broadcasting, beacons), an asynchronous communication prototype is also discussed in the paper. Due to the physical limitations associated with typical image sensors (including low and varying frame rates, long exposures, and low shutter speeds), the link speed performance is critically considered. Based on the practical measurement of camera response to modulated light, an operating frequency range is suggested along with the similar system architecture, decoding procedure, and algorithms. A significant feature of our novel data frame structure is that it can support both typical frame rate cameras (in the oversampling mode) as well as very low frame rate cameras (in the error detection mode for a camera whose frame rate is lower than the transmission packet rate). A high frame rate camera, i.e., no less than 20 fps, is supported in an oversampling mode in which a majority voting scheme for decoding data is applied. A low frame rate camera, i.e., when the frame rate drops to less than 20 fps at some certain time, is supported by an error detection mode in which any missing data sub-packet is detected in decoding and later corrected by external code. Numerical results and valuable analysis are also included to indicate the capability of the proposed schemes.

Design and Implementation of the MIMO–COOK Scheme Using an Image Sensor for Long-Range Communication

“…The figure demonstrates that the use of a matched filter to decode the COOK scheme is better than the zero-crossing filter. It illustrates that the performance of our proposed scheme is better than that of the COOK proposed in [22]. From the SNR measurements of Figures 10 and 11, we can gain a BER of 10 −4 at 20 m (SNR of 12.5 dB, exposure time of 50 µs) using the matched filter.…”

“…In Section 3, we provide the details of the MIMO-COOK scheme. Unlike the COOK mentioned in [22], we used RoI algorithms to detect light sources. To detect preambles and decode, we used a matched filter instead of the zero-crossing filter.…”

“…In [22], we proposed the camera on-off keying (COOK) scheme with a single LED. To decode data, we used the zero-crossing to verify the on/off value in the images.…”

Design and Implementation of a Monitoring System Using Optical Camera Communication for a Smart Factory

“…Using region-of-interest (RoI) signaling, a waveform for a vehicular system has been presented in [20]. Based on the rolling-shutter effect, in [21] the authors present camera on-off keying (OOK) modulation with a high data rate, but the rolling-shutter method has some drawbacks, including the limited transmission distance and high error rate. Two-dimensional orthogonal frequency division multiplexing (OFDM) for OCC, using the screen method, is discussed in [22], which demonstrates a high data rate but also reveals a disadvantage: the large size of the transmitter and short distance make it an expensive transmitter.…”

An optoelectronic equivalent narrowband filter for high resolution optical spectrum analysis

“…Optical filters are essential in a wide range of applications, including optical communications [1], spectroscopy [2,3], electronics [4] and optical sensors [5~9]. Especially, high resolution optical spectroscopy of high performance optical sensors has always attracted considerable interest and characters of optical spectrum analysis (OSA) such as resolution, dynamic range and measurable range highly depend on optical filters.…”