Abstract
Colour-shift keying (CSK) constitutes an important modulation scheme conceived for the visible light communications (VLC). The signal constellation of CSK relies on three different-color light sources invoked for information transmission. The CSK constellation has been optimized for minimizing the bit error rate, but no effort has been invested in investigating the feasibility of CSK aided unequal error protection (UEP) schemes conceived for video sources. Hence, in this treatise, we conceive a hierarchical CSK (HCSK) modulation scheme based on the traditional CSK, which is capable of generating interdependent layers of signals having different error probability, which can be readily reconfigured by changing its parameters. Furthermore, we conceived an HCSK design example for transmitting scalable video sources with the aid of a recursive systematic convolutional (RSC) code. An optimization method is conceived for enhancing the UEP and for improving the quality of the received video. Our simulation results show that the proposed optimized-UEP 16-HCSK-RSC system outperforms the traditional equal error protection scheme by $\sim 1.7$ dB of optical SNR at a peak signal-to-noise ratio of 37 dB, while optical SNR savings of up to 6.5 dB are attained at a lower PSNR of 36 dB.
Highlights
Background of Visible Light Communication Overview of Unequal Error Protected Video Transmission Brief Review of Multilevel Coded Modulation Rationale of This TreatiseColour-shift keying (CSK) Modulation CSK Constellation and Coding Optical Domain Channel Model Soft Demodulator for CSK
Multilevel coded modulation was originally proposed by Calderbank and Seshadri for providing unequal error protection (UEP) [72], where the 2-dimensional signal constellation is partitioned into disjoint subsets and the bit streams of different importance are carefully mapped to the different-integrity bit-positions of the constellation subsets
The constellation and bit-tosymbol mapping of the traditional CSK are completely redesigned in our novel hierarchical CSK (HCSK). 2) We provide a HCSK design example for transmitting scalable video sources relying on the recursive systematic convolutional (RSC) code as the forward error correction (FEC). 3) Our optimisation metric is the quality of the received video
Summary
This treatise is based on the structure of Fig. 1. In the light of these problems, Visible Light Communications (VLC) [2]–[6] has emerged as an appealing access method to provide extra licensefree bandwidth, as a compliment to WiFi, femtocells, ultra wideband (UWB) and mm-wave communications in order to support indoor communications. VLC supports high-rate downlink communications, in addition to its primary function of illumination in indoor environments. IEEE 802.15 Working Group [5] Li-Fi (Light-Fidelity) Consortium [14] VLCA (Visible Light Communications Associations) [15]. Contributions proposed high-switching-speed LEDs and their modulation for visible light communications. Proposed white LED for both communications and illumination. Was formed in Oslo, Norway, as a complement to Wi-Fi. is established as a successor of VLCC in Japan for further standardization of VLC
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