Research On Link Survivability Of Visible Light Communication Network Based On MIMO

With the rapid development of the Internet,people's demand for communication speed and bandwidth is increasing.However,the traditional radio frequency(RP)spectrum resources are in short supply and cannot meet the ever-increasing demand for data transmission in the future.Visible light communication(VLC)is a wireless communication technology based on light emitting diode(LED),which can simultaneously meet the needs of lighting and communication.Because LED light source has the advantages of energy saving,environmental protection,low price and high stability,it has been widely concerned and studied by experts and scholars.Due to the linear propagation characteristics of light,the channel of VLC is different from traditional RF communication.The link survivability of VLC mainly refers to the ability of the system to cope with occlusion or light source failure.In addition,a single LED as light source is limited due to the illumination coverage and channel capacity,which cannot meet the requirements of indoor communication and lighting.In the field of wireless communication,multiple-input multiple-output(MIMO)adopts multiple transmitting antennas at the transmitting end,and corresponding receiving antennas are also used at the receiving end,so that the information to be transmitted is respectively.The transmission and reception by multiple antennas make full use of space resources.Since multiple spatial subchannels are used without occupying additional spectrum resources,the overall capacity of the system is correspondingly increased.Therefore,the application of MIMO technology in VLC and the joint transmission of multiple LED light groups not only expand the illumination range,but also double the channel capacity,and meet the needs of indoor VLC and illumination perferably.In the link survivability problem based on MIMO-VLC,how to reduce the communication and lighting quality caused by occlusion and sudden failure of light source through effective measures is the research purpose of this thesis.At present,the most common method for occlusion problems is to use wall reflection or repeater forwarding.This method has special requirements on the material of the wall or the installation position of the repeater,and can only be applied to specific occasions.For the anti-light source burst problem,there is no complete solution at present,but there are some dimming control methods to improve the indoor lighting environment.Therefore,this paper studies the above two problems and proposes corresponding solutions.The innovative work of this paper mainly includes the following two aspects:·A MIMO-VLC anti-occlusion communication scheme based on random interleaving is proposed.In the VLC communication system,since visible light is very sensitive to obstacle occlusion,in the process of data communication,the channel is easily degraded due to occlusion,which lead to decreased communication quality,even the communication is interrupted.In this case,how to resume communication and how to communicate efficiently is the issues that this paper is concerned with.The traditional anti-occlussion method generally uses wall reflection or repeater to forward information,which has special requirements on the material of the wall or the installation position of the repeater,so it is inflexibille.The scheme proposed in this paper uses random interleaving technology to randomly discard the encoded information and send it out by multiple LED groups,thus converting continuous burst errors caused by occlusion into discrete random errors,combined with error correction coding technology.The original information can be demodulated without distortion at the receiving end finally.Compared with the traditional repeater forwarding,this scheme has better flexibility,and without additional requirements for the environment.The experimental results show that with the 4×4 MIMO-VLC system when transmission distance is 0.6m,and the bit error rate of 3.7*10-4 is achieved,which can meet the basic communication requirements.·An adaptive dimming-based MIMO-VLC anti-fault communication scheme is proposed.In the existing research on VLC technology,there are few researches on light source failure.When some LEDs fail,the link information is lost and the lighting environment is greatly affected.This is different from the previously mentioned anti-occlusion and cannot be solved by existing technologies.Instead,the system needs to be adaptively adjusted to enable communication and illumination to continue.There are two technical difficulties here:Firstly,how to distribute the data information to be transmitted by the faulty LED to other branches,and how to distinguish the original information from the superimposed information without affecting the communication of other branches;Secondly,under the premise of indoor lighting environment changes,how to adj ust the lighting parameters,so that the illuminance maintains a stable level relatively.These two difficulties are solved by an adaptive dimming-based MIMO-VLC anti-fault communication scheme proposed in this paper.Simulation and experimental results show that the system can restore communication transmission and improve lighting performance at the same time,when the transmission distance is 0.6m,the bit error rate of 3.3*10-3 is achieved.