Research On Key Technologies Of Visible Light Communication And Monitoring Network On Dual Communication Mode

Visible light communication(VLC)utilizes light emitting diodes(LED)as light source,which can transmit data at high speed while lighting.Compared with other wireless communication technologies,VLC has the advantages of wide spectrum resources,no electromagnetic interference,and green energy saving.Meanwhile,indoor high precision positioning can be achieved by using VLC technology.A new visible light communication and monitoring network can be realized through the combination of visible light communication and visible light positioning(VLP)technology.With the increasing demand for information sharing between mobile terminals,the device-to-device communication(D2D)technology arises at the historic moment.As a carrier of D2D communication,VLC can provide business services with large bandwidth for users.In modern indoor environment,users often need to work in dual communication mode(i.e.,cellular communication mode and D2D communication mode).Visible light is very sensitive to occlusion and other disturbing light,which leads to the decline of communication quality in VLC network of the dual communication mode.And the mutual interference between VLC and VLP signals also brings some challenges to system performance.So this paper researches and solves these two important problems in the real application scenario.The innovative work of this paper mainly includes the following two aspects:· An anti-occlusion visible-light communication system based on physical-layer network coding(PNC)is proposed.The communication will be interrupt when the link of VLC is blocked.It's a technical difficulty in the VLC communication system with dual communication modes.So how to recovery communication and how to communicate efficiently is a big problem.Conventional anti-occlusion methods usually use highly reflective wall for signal reflection or use some repeaters in a fixed location for forwarding signal.In this paper,we propose an efficient relay scheme by design appropriate coding.The received communication signals are processed and modulated in the physical layer by PNC technology.The signals go through particular relay nodes with appropriate modulation and demodulation scheme,and then the superimposed communication signals are mapped and transmitted by constellation.Compared with traditional relay schemes,the time slot of communication can reduce to half and the system throughput can be doubled in theory by using the relay scheme we propose in this paper.· An indoor intelligent visible light system based on Triple-Domain-Cooperation scheme is proposed.VLC technology and VLP technology have been independent researched broadly.And there are two technical difficulties in combining the two technologies.One is to integrate communication and positioning in a system.Another is how to alleviate the influence of other LED cells.In this paper,we overcome these two difficulties through the cooperation of time domain,frequency domain and space domain.Considering the collision of communication and positioning,the LED lamp beads are connected in series and are divided into two groups,so they are isolated in the space.In the frequency domain,the communication and positioning information are isolated by the division of frequency band,and positioning information of the cells is allocated in different time slot by using the four color theory.The methods of trilateration and reference point correction are used for indoor positioning.The experimental results show that the system achieves the positioning accuracy of 0.04m in the 0.8m*0.8m*0.65m experimental environment and the bit error rate of 10-5 is gained at the communication rate of 10MHz/s.