Efficient coding modulation and seamless rate adaptation for visible light communications

The past decade has witnessed a rapid development of VLC technologies. However, the spectral efficiency has to be improved and the robustness enhanced, especially in dynamic lighting conditions. This article proposes an analog rateless code (ARC) modulation scheme for VLC in a hybrid VLC-RF system. The ARC uses a variable-length low-density random projection matrix to map a block of bits into a virtually unlimited number of modulation symbols. The sender progressively transmits the symbols, which are jointly decoded at the receiver, until an acknowledgment of successful decoding is received. Both the protocol design and coding matrix generation are discussed. Simulations validate that our proposed scheme not only achieves the desired seamless rate adaptation, but significantly outperforms a traditional OFDM VLC system in spectrum efficiency. Furthermore, experimental results demonstrate the feasibility of the proposed ARC scheme in a VLC system.