Enhancing reliability to boost the throughput over screen-camera links

Abstract

With the rapid proliferation of camera-equipped smart devices (e.g., smartphones, pads, tablets), visible light communication (vlc) over screen-camera links emerges as a novel form of near-field communication. Such communication via smart devices is highly competitive for its userfriendliness, security, and infrastructure-less (i.e., no dependency on WiFi or cellular infrastructure). However, existing approaches mostly focus on improving the transmission speed and ignore the transmission reliability. Considering the interplay between the transmission speed and reliability towards effective end-to-end communication, in this paper, we aim to boost the throughput over screen-camera links by enhancing the transmission reliability. To this end, we propose RDCode, a robust dynamic barcode which enables a novel packet-frame-block structure. Based on the layered structure, we design different error correction schemes at three levels: intra-blocks, inter-blocks and inter-frames, in order to verify and recover the lost blocks and frames. Finally, we implement RDCode and experimentally show that RDCode reaches a high level of transmission reliability (e.g., reducing the error rate to 10%) and yields at least two-fold improvement of transmission rate, compared with the existing state-of-the-art approach COBRA.

SoftLight: Adaptive visible light communication over screen-camera links

“…In this section, we further study the impact of spatially-variant environments. We conduct experiments with RDCode [26], the latest high-throughput barcode design. We measure Bit Error Rate (BER), i.e., the ratio between the incorrectly-decoded bits and the total received bits.…”

“…It is hard to find a block size that efficiently extracts the correctly-received bits in one frame for different link qualities. Some FEC parity check bits may be added in each block [26] to enhance the block reception. The prefixed error correction capacity (sometimes also referred as coding rate) of FEC codes, nevertheless, cannot adapt to diverse link qualities.…”

“…Finally, the symbol frames are rendered and displayed on the screen according to a specific barcode layout. As a channel coding scheme, SoftLight works atop all general barcode layouts, e.g., QR Code [1], COBRA [10] and RDCode [26]. The size of a data frame is determined by the number of symbols in one barcode frame.…”

“…Visible Light Communication (VLC) over screen-camera links has become a promising technique for short-range communication on smartphones [12], [26]. When the sender screen displays a stream of barcodes, other camera-equipped devices can capture the frames and decode the information modulated by the colors of barcode symbols.…”

“…The experiment results suggest that SoftLight can correctly transmit a 22-KByte photo between two smartphones within 0.6 second and achieve the maximum goodput of 317.3 kbps. In practical scenarios, on average, SoftLight provides 2.2¢ and 10.3¢ goodput improvement over RDCode [26] and COBRA [10] respectively.…”