Carrier-free amplitude phase modulation system and modulation method based on Faster-than-Nyquist precoding

Abstract

The invention belongs to the technical field of visible light communication, and especially relates to a carrier-free amplitude phase modulation system and modulation method based on a Faster-than-Nyquist precoding technology. The system and the method are applied to a visible light communication system. The modulation system mainly comprises a QAM mapping module, an I / Q separation module, a differential coding module, a delay addition module, an upper conversion module and a forming filtering module. When signals are processed, the signals are divided into two ways of same direction I and orthogonal Q branches. The upper way and the lower way are processed by the above-mentioned process. Finally, the two ways of signals are combined into one way of signals at a transmitting end through subtraction operation. Compared with a traditional Nyquist bandwidth CAP modulation system, the system and the method have the advantages that Faster-than-Nyquist CAP signals of which signal bandwidth is further compressed can be generated; the guard band between CAP sub-bands can be eliminated; a certain extent of overlap can be tolerated; the signal bandwidth is utilized effectively; and the spectrum efficiency of the visible light communication system is improved.

Description

technical field [0001] The invention belongs to the technical field of visible light communication, and in particular relates to a carrier-free amplitude-phase modulation system and modulation method applied in a visible light communication system. Background technique [0002] Visible light communication (VLC, Visible Light Communication) is a new green information technology that utilizes the fast response characteristics of LEDs to achieve high-speed data transmission. This technology uses LED as a light source, and can enable lighting equipment to have functions such as "wireless router", "communication base station", and "network access point" without affecting normal lighting. Visible light communication, as a new communication mode combining lighting and optical communication, will promote the integrated development and technological progress of next-generation lighting and access networks, and has become the focus and commanding heights of competition at home and abr...

AI Technical Summary

Problems solved by technology

[0004] Carrier-free amplitude-phase modulation (CAP), as a high-spectrum-efficient amplitude modulation, has been proved by experiments to be a very suitable modulation method for visible light communication systems. In the multi-sideband CAP modulation system in multi-user scenarios, the subband Due to strong out-of-band interference, a certain frequency interval (guard band) must be reserved, which is very unfavorable for visible light communication systems with precious spectrum resources.

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