Optical Camera Communications for IoT–Rolling-Shutter Based MIMO Scheme with Grouped LED Array Transmitter

Abstract

In optical camera communications (OCC), the provision of both flicker-free illumination and high data rates are challenging issues, which can be addressed by utilizing the rolling-shutter (RS) property of the image sensors as the receiver (Rx). In this paper, we propose an RS-based multiple-input multiple-output OCC scheme for the Internet of things (IoT) application. A simplified design of multi-channel transmitter (Tx) using a 7.2 × 7.2 cm2 small 8 × 8 distributed light emitting diode (LED) array, based on grouping of LEDs, is proposed for flicker-free transmission. We carry out an experimental investigation of the indoor OCC system by employing a Raspberry Pi camera as the Rx, with RS capturing mode. Despite the small area of the display, flicker-free communication links within the range of 20–100 cm are established with data throughput of 960 to 120 bps sufficient for IoT. A method to extend link spans up to 1.8 m and the data throughput to 13.44 kbps using different configurations of multi-channel Tx is provided. The peak signal-to-noise ratio of ~14 and 16 dB and the rate of successfully received bits of 99.4 and 81% are measured for the shutter speeds of 200 and 800 µs for a link span of 1 m, respectively.

Spatial frequency-based angular behavior of a short-range flicker-free MIMO–OCC link

“…A simple design of the MIMO Tx unit is adopted from our previous work in [12], as illustrated in Fig. 2.…”

“…The characterization of the proposed MIMO Tx unit in terms of its optical radiation pattern and output optical power-current-voltage (L lux −I −V ) curves was performed in [12]. Note, it is recommended to drive each LED with I LED = 20 mA [12,28]. Therefore, for the LED array, the drive current I LED-array was set to 1.28 A to measure L lux −I −V .…”

“…Therefore, for the LED array, the drive current I LED-array was set to 1.28 A to measure L lux −I −V . It was found that the NeoPixels used either as a single LED chip or an LED-array together with the grid and diffuser depicted liner L lux −I −V plots, which are highly desirable in IM VLC systems [12]. Figure 3 illustrates the data mapping on the controller side for the proposed MIMO-OCC using two 64-NeoPixel Tx units and an Arduino Uno microcontroller-based driver per Tx.…”

“…However, the major challenge in implementing systems with a low R b is the requirement for flicker-free transmission. Authors established flicker-free communications links using the grouped LED array concept in [12] using RS-based capturing Rx with a R b of ∼1 kb/s. The RS acquisition mechanism that sequentially integrates light on rows of pixels is the major advantage of CMOS IS used as the Rx in OCC [13].…”

Design of Streaming Data Transmission Using Rolling Shutter Camera-Based Optical Camera Communications

“…At the camera receiver, the information sent via the visible light spectrum appears in the form of a barcode on the captured image, and the patterns of the barcode contain the transmitted data. Recently, Teli et al [12] carried out an experimental investigation of an indoor OCC system by employing a multi-channel transmitter and a Raspberry Pi camera as the Rx for IoT applications. Nguyen et al [13] proposed a rolling shutter-based OFDM OCC system with multiple LEDs to improve the data rate performance.…”