In this paper, we investigate the constellation design for the multiple-input single-output (MISO) dimmable visible light communication, where a total average- and a peak-intensity constraint are imposed on the channel input. An optimized spatial constellation is obtained by an equiprobable equally-spaced signal constellation (with a carefully-chosen minimum distance) concatenated with the minimum-energy signaling mapper. Error performance and rate loss of the proposed spatial constellation at high SNRs are evaluated as well. Numerical results show the performance advantage of our proposed constellation over the benchmarks.
Recently, visible light communication (VLC) is regarded as a new type of wireless communication that utilizes intensity modulation and direct detection (IM/DD) to realize signal transmission. In order to make better use of spatial resources to realize multi-LED collaborative transmission and dimming control, multi-LED phase-shifted space-time codes (MP-STC) has been proposed for dimmable multi-LED VLC systems. Although the MPSTC scheme has much better communication and illumination performance, the complexity of the traditional maximum likelihood (ML) detection algorithm is too high to implement. In this paper, a low complexity detection algorithm has been proposed for the MP-STC scheme. The simulation results show that the detection algorithm’s error performance is close to or even achieving the ML detection algorithm’s error performance.
Free space optical (FSO) communication is an efficient and environmentally friendly communication technology. FSO communication has attracted attention and it been considered as a next emerging high-speed communication technology due to high bandwidth, low cost of implementation, unlicensed spectrum allocation, and security compared with other wireless technology. Atmosphere turbulence, leading to the performance loss of communication links, is the main influence factor in the outdoor optical communication system. In this paper, the mitigation of channel fading is studied by designing a transceiver scheme and making full use of the advantages of the diversity technology on the premise of channel statistics at the transmitter. Spatial diversity technology is an effective means to mitigate channel fading and improve system performance. Besides, as the number of users' devices is growing significantly, the demand for multi-user high-speed communication is more and more urgent. Meanwhile, for low implementation complexity, intensity modulation with direct detection (IM/DD) is commonly used in the FSO communication system. For those reasons, we study the IM/DD transceiver design for two-user SIMO FSO communications over weak atmospheric turbulent channels, to mitigate fading caused by turbulence and improve bit error rate performance. To efficiently realize transmission and manage the multi-user interference, which is a core problem in modern digital communication systems, this paper develops a novel concept of multiplicative unique decomposable constellation group (MUDCG) and then propose a signal set design, which can be uniquely and efficiently decomposed by each user at the receiver. We design a MUDCG in one dimension, with the constellation minimizing the optical power with the minimum Euclidean distance after taking the logarithm. Notably, the proposed constellation is equivalent to the commonly-used pulse amplitude modulation (PAM) constellation, which admits a fast decoding structure. Simulation results show that the MUDCG design has a significant improvement in error performance as compared with the conventional TDMA scheme.
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