Performance Of Modulation Formats In Indoor Positioning Visible Light Communication System

In order to combat with multipath effect and minimize the delay spread damage to the system , one of effective technologies is adopting different modulation scheme based on the specific communication environment for data transmission. In indoor visible light communication(VLC), LEDs array form layout usually adopted to ensure double-property of light emitting diode (LED), both of illumination and communication., that way can avoid the shadow effect. But too much LED number will strengthen the influence of multipath effect, data in receiver data will be caused by system delay spread, which makes inter symbol interference (ISI) added, eventually decreasing the overall system performance. Especially for edge and corner area , which can not meet the requirement of the stable communication link, becoming the dead zone. Thus, choosing suitable modulation scheme is very important to improve the system performance and guarantee system stability.Research shows that: as the basic modulation technology of the VLC,on-off keying(OOK) is suitable for low-delay transmission communication environment with high average transmission power and high-delay low-speed transmission environment with higher average transmission power demand.. Compared with other modulation formats.Pulse position modulation (PPM), with simple principle is more suitable for high-delay high-speed communications environment with low average transmission power. Compared with two other kinds of modulation technology, adopting Asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) modulation scheme is best for low-delay high-speed communication environment with low average transmission power and high-delay high-speed communication environment with high average transmission power.This paper focus on VLC modulation formats, specific working actions and simulation result conclusions are as follows:First, introduce basic principles of visible light communication system model and transmission links. After that, establish the simulation platforms, including light intensity and light power of receiving plane, the impulse response of different link, system delay and signal to noise ratio(SNR) and bit error rate (BER) performance analysis, Simulation result shows that the system conforms to international lighting standards of OSI model, but the edge and the corner of the room become communication blind zone, improving communication performance is required.Second, set up he system simulation platform for OOK, ACO -OFDM and PPM, and then make analysis on the three modulation format.The simulation result shows that: 1. For M-QAM ACO-OFDM modulation, when Mequals 4, the BER performance achieves the best; 2.For Q - PPM modulation, when Q equals 16, the BER performance to achieve the best; 3. No matter what kind of modulation format, system delay and transmission rate are the two main factors influencing system performance. A reverse relationship between system delay and system performance as well as transmission rate and system performance.Third, comparing three kinds of modulation formats, the result shows that as the basic modulation technology of the VLC, on-off keying(OOK) is suitable for low-delay transmission communication environment with high average transmission power and high-delay low-speed transmission environment with higher average transmission power demand.. Compared with other modulation formats. Pulse position modulation (PPM), with simple principle is more suitable for high-delay high-speed communications environment with low average transmission power. Compared with two other kinds of modulation technology, adopting Asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) modulation scheme is best for low-delay high-speed communication environment with low average transmission power and high-delay high-speed communication environment with high average transmission power.In a nut shell, this paper focus on VLC modulation formats.establishing simulation model in order to verify simulation platform feasibility. Comparing OOK the ACO-OFDM and PPM in indoor VLC system, the result shows that: 1. For M-QAM ACO-OFDM modulation,when M equals 4, the BER performance achieves the best; 2. For Q -PPM modulation, when Q equals 16, the BER performance to achieve the best; 3. No matter what kind of modulation format, system delay and transmission rate are the two main factors influencing system performance. A reverse relationship between system delay and system performance as well as transmission rate and system performance.