Abstract
We address the lens optimization and signal processing for array-based multiple-input multiple-output (MIMO) visible light communication, especially under link misalignment. We employ one concave lens and one convex lens to separate the lights from different light-emitting diodes (LEDs), and optimize the lens structure to minimize the condition number of channel gain matrix. In this way, the light emitted by different LEDs can be separated well from each other. To further mitigate the interference under transmitter/receiver mobility, we propose two signal processing approaches based on successive interference cancellation (SIC) and multi-layer coding (MC), along with maximum ratio combining (MRC) for interference/signal decoding. It is demonstrated that the interference can be reconstructed and eliminated through SIC, and MC can partially decode the interference to better reconstruct the desirable message. The proposed signal processing approaches can significantly improve the sum rate in both link alignment and misalignment cases. Moreover, MC can achieve higher sum rate, especially in the case of link misalignment.
Highlights
With steady development of mobile communication technology, the spectrum resource has become more and more sparse, leading to spectrum crisis
We present the numerical results of achievable rate using signal combining with multi-layer coding (SC+MC), as well as the successive interference cancellation (SC+SIC) under different mobile situations
We have proposed a long-distance multiple-input multiple-output (MIMO) visible light communication (VLC) system and the corresponding signal processing method considering the misalignment due to transmitter/receiver mobility
Summary
With steady development of mobile communication technology, the spectrum resource has become more and more sparse, leading to spectrum crisis. In the MIMO VLC system, imaging architecture can be adopted at the receiver to achieve spatial diversity For such type of system, the design of suitable optical antennas is an essential problem. Hemispherical lens [18], fisheye lens [19] are typically used to provide a wider view while increasing the optical gain, and other different kinds of lenses [20] [21] that can separate light beams and reduce inter-cross are desirable Another issue in MIMO VLC system is the signal interference under link misalignment, which means that the PD receives the desired signal, and the interference signal from adjacent LEDs. Common signal processing methods focus on suppressing interference. Considering the special interference structure of the array-based system, we propose two approaches for signal processing under transmitter/receiver mobility, including SIC and group decoding to eliminate the interference.
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